mira infection notes

8/19/2019 MiRa Infection Notes

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Sporotrichosis

Sporofhrix schenckii is a dimorphic fungus found in the natural

environment in the form of mold (hyphae).

It resides on the bark of trees. shrubs. and garden plants. and on

plant debris in soil.

Sporotrichosis is common in gardeners.

The initial lesion. a reddish nodule that later ulcerates.

appears at the site of the thorn prick or other skin injury.

From the site of inoculation the fungus spreads along the

lymphatics forming subcutaneous nodules and ulcers.

Subse!uent papules develop along the route of lymphatic flo". #denopathy and systemic signs of infection are usually absent

Candida

$andida coloni%es air"ays and usually does not cause pneumonia

&ral itracona%ole is effective against some strains of $andida that

are resistant to flucona%ole.

Mucormycosis

This patient is most likely suffering from mucormycosis of the nose

and maxillary sinus.

The most common etiologic agent is 'hi%opus. oorly controlled diabetes mellitus predisposes to this disease.

o"*grade fever. bloody nasal discharge. nasal congestion. and

involvement of the eye "ith chemosis. proptosis. and diplopia are

important features.

Involved turbinates often become necrotic.

Invasion of local tissues can lead to blindness. cavernous sinus

thrombosis. and coma.

If left untreated. mucormycosis can lead to death in days to "eeks.


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+,- . Influen%a and /oraxella catarrhalis are common causes of

bacterial sinusitis.

These usually do not cause necrotic infections.

Invasive aspergillosis

Invasive aspergillosis can involve multiple organ systems

occurs in immunocompromised patients (e.g those "ith neutropenia.

those taking cytotoxic drugs such as cyclosporine. and those taking

very high doses of glucocorticoids).Invasive pulmonary disease presents "ith fever cough dyspnea or

hemoptysis.

$hest x*ray may sho" cavitary lesions.

$T scan sho"s pulmonary nodules "ith the halo sign or lesions "ith

an air crescent.

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Blastomycosis is endemic in the south*central and north*central 1S.

Histoplasmosis is most common in the southeastern. mid*#tlantic.

and central 1S.

,oth blasto2histo in both &haio 2missisipi

Coccidioides is endemic in the south"estern 1S. as "ell as $entral

and South #merica(#ri%ona3$alifornia)


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BLASTOMYCOSIS - !LC"#AT"$ S%I& L"SIO&S ' LYTIC

BO&" L"SIO&S-

. Fungal infection of the lung.. . 'esidence in great lakes /ississippi &hio river 2 4isconsin.

. ulmonary symptoms resembling T.,. 2 istoplasmosis.

. 1$5'#T56 S7I+ 5SI&+S 2 8TI$ ,&+5 5SI&+S

($haracteristic9).

. Skin lesions *: /ultiple "ell circuscribed verrucus crusted lesions.

. ,one lesions *: ytic lesions in the anterior ribs.

. 6x *: Sputum culture *: ,' ,#S56 ,166I+; 85#ST.

. Tx *: IT'#$&+#


4/39

. It is a dimorphic fungus found in soil "ith high concentration of

bird or bat droppings

. Infection through inhalation of the spores of istoplasma

capsulatum fungus.

This patient presents "ith signs3symptoms consistent "ith

disseminated pulmonary histoplasmosis.

a fungal disease caused by contaminated soil in endemic areas such

as the &hio 'iver valley.

istoplasmosis is fairly self*limiting in immunocompetent people but

can cause significant pulmonary and disseminated disease

in patients "ith $6? counts @ A BB3jC. These patients typically present "ith fever. "eight loss. night

s"eats. nausea. vomiting. and cough "ith shortness of breath.

5xamination findings can include diffuse lymphadenopathy and

hepatosplenomegaly.

aboratory findings can include pancytopenia (if bone marro" is

involved).

elevated liver function tests. and elevated ferritin

Flucona%ole has less activity for histoplasma than does

itracona%ole and is not recommended as primary treatment unlessthe patient cannot tolerate itracona%ole.

Flucytosine is effective against $ryptococcus and $andida but not

against histoplasma.

/etronida%ole is effective against amebiasis and other anaerobic

bacterial infections but does not treat histoplasma.

ltracona%ole is the preferred antifungal treatment forhistoplasmosis.

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5/39

In(luen)a

The influen%a virus has three different antigenic types- # , and $.Influen%a # and , produce clinically indistinguishable infections.

"hereas type $ usually causes a minor illness

This patient presents "ith signs and symptoms of influen%a

pneumonia.

Influen%a is characteri%ed by the abrupt onset of fever. chills.

malaise. myalgias. cough. and cory%a.

It typically occurs in an epidemic pattern. often in the "inter. &n physical exam. patients "ill often be febrile and may have a

variety of pulmonary findings. including "hee%es. crackles. and

coarse breath sounds.

eukopenia is common and proteinuria may be present.

$hest x*ray may be normal or sho" an interstitial or alveolar

pattern.

This patient became ill in the "inter and has classic symptoms.

laboratory results. and radiographic findings of influen%a.

+asal s"abs for influen%a antigens are the fastest "ay to confirm

this diagnosis.

#ntiviral treatment must be started "ithin ?D hours to be effective.

T"o classes of antiviral drugs are available for the prevention and

treatment of influen%a-

A . #mantadine and rimantadine * these are only active againstInfluen%a #

E. +euraminidase inhibitors (i.e .. %anamivir. oseltamivir) * these are

active against both influen%a # and influen%a ,.


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The administration of antiviral drugs usually results in shortening of

the duration of symptoms by E* daysG

ho"ever. the benefit is greatest "hen the drug is given "ithin the

first E? to B hours in a patient "ho presents "ith fever.

*e+rile neutropenia

&ver the past decade. there has been a shift from gram*negative to

gram*positive bacteria being the most fre!uent cause of neutropenic

infection.

considered a medical emergencyG thus. empiric antibiotics should bestarted immediately.

5mpiric therapy should be broad*spectrum and should cover

(seudomonas aeruginosa .

5ither monotherapy or combination therapy can be employed.

/onotherapy consists of cefta%idime. imipenem. cefepime. or

meropenem.

$ombination therapy is e!ually effective. and consists of anaminoglycoside plus an anti*pseudomonal beta*lactam.

in(ectious mononucleosis

>the kissing disease> and >glandular fever.>

fever sore throat malaise jaundice and mild hepatosplenomegalyconsistent "ith likely infectious mononucleosis (I/).

The clinical features of I/ include fever sore throat toxic

symptoms. and symmetrical lymphadenopathy involving the posterior

cervical chain of lymph nodes more fre!uently than the anterior

chain.

Inguinal and axillary lymphadenopathy can also be present.

&ther physical findings include pharyngitis tonsillitis and tonsillarexudates.


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/ild palatal petechiae may be found but this non*specific sign may

also be seen in streptococcal pharyngitis.

Tonsillar enlargement can cause air"ay compression.

epatitis and jaundice are present in a small percentage of cases. The findings of hepatosplenomegaly malaise and fatigue. and

generali%ed lymphadenopathy (as seen in this patient) tend to favor

I/ and are not commonly seen in other bacterial causes such as

streptococcal pharyngitis.

The diagnosis of I/ is confirmed by -the presence o( atypical

lymphocytosis and anti-heterophile anti+odies ,Monospot. "hich

typically indicate 5,= associated disease.

eterophile antibodies are sensitive and specific for I/. The "B/-speci(ic anti+ody test is used in patients "ith suspected

I/ and a negative heterophile antibody test

These antibodies generally appear "ithin one "eek of the onset of

symptoms and may persist in lo" levels for up to one year.

o"ever these antibodies sometimes may not appear until later in

the course of the illness.

For this reason a negative heterophile antibody test in the first

fe" "eeks of illness does not rule out the diagnosis of I/.

#typical lymphocytes are seen in the peripheral smear of patients

"ith I/ but are nonspecific.

They may also be present in patients "ith to0oplasmosis1 ru+ella1

roseola1 viral hepatitis1 mumps1CM/1 acute HI/ in(ection1 and

some drug reactions

&ne of the hematological complications of I/ is autoimmunehemolytic anemia and throm+ocytopenia. "hich is due to cross

reactivity of the 5,=*induced antibodies against red blood cells and

platelets.

These antibodies are lg/ cold*agglutinin antibodies kno"n a anti*i

antibodies.

"hich lead to complement*mediated destruction of red blood cells

(usually $oombsH*test positive).


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The onset of the hemolytic anemia can be E* "eeks after the

onset of the symptoms. even though the initial laboratory studies

may not sho" anemia or thrombocytopenia (as in this patient).

This patient is most likely suffering from infectious mononucleosis.and splenic rupture is a serious potential complication.

#ll patients "ith splenomegaly should avoid excessive physical

activity. particularly contact sports. until their spleen regresses in

si%e and is no longer palpable (usually after one to three months).

osterior cervical lymphadenopathy and a maculopapular rash may be

seen in infectious mononucleosis

eukocytosis is common.

In infectious mononucleosis. rash often develops after theadministration of ampicillin.

rimary I= infection causes a febrile illness that can closely

resemble infectious mononucleosis.

The key distinctions bet"een the t"o are that rash (unless

antibiotics have been administered) and diarrhea are 5SS common

in infectious mononucleosis and the finding of a tonsillar exudate is

uncommon in primary I=.

&ocardia

+ocardia is a gram*positive "eakly acid*last filamentous branching

rod found in soil and "ater.+ocardia (usually +. asteroides) is an important cause of infection in

immunocompromised hosts such as I= patients or organ transplant

recipients.

The lung is the most fre!uently involved organ. and infection can

manifest as nodules. a reticulonodular pattern. di((use pulmonary

in(iltrate. a+scess. or cavity (ormation.

6iagnosis of +ocardia is difficult.


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# presumptive diagnosis can be made it partially acid*Fast

filamentous. branching rods are seen in clinical specimens.

The treatment of choice is trimethoprim-sul(ametho0a)ole.

#u+ella ' measles

The characteristic rash of ru+ella is erythematous andmaculopapular.

It starts on the face and progresses to the trunk and extremities.

rodromal symptoms include fever. lymphadenopathy. and malaise.

&ccipital and posterior cervical lymphadenopathy are suggestive of

the diagnosis.#dult "omen usually have associated arthritis. "hich is another

diagnostic clue.

Some patients may have mild cory%a and conjunctivitis.

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The characteristic rash of measles is also erythematous andmaculopapular. and similarly progresses from the head to the trunk

and extremities.There is usually a prodrome of fever. cough. cory%a. and

conjunctivitis.

The presence of 7oplikHs spots is suggestive. #rthritis is not

commonly seen.

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The rash of chic2en po0 is pruritic and usually develops after aprodrome of fever and malaise.

The lesions appear in consecutive crops. so lesions of several

different stages are often visible on examination (i.e .. papular.

vesicular. and crusted lesions).


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ru+ella immuni)ation.If a "oman becomes pregnant earlier than three months after

rubella immuni%ation.

reassurance is the appropriate step. reviously. "omen of childbearing age "ere advised to avoid

conception for at least three months after rubella immuni%ationG

ho"ever. there have been no case reports to date of congenital

rubella syndrome in "omen inadvertently vaccinated during early

pregnancy.

In fact. the #dvisory $ommittee on Immuni%ation ractices (#$I)

has reduced the recommended "aiting time for conception from

months to ED days

CM/

$/= pneumonitis should be considered in the differential diagnosis

of any bone marro" transplant (,/T) recipient "ith both lung and

intestinal involvement. 'isk factors include certain types of immunosuppressive therapy

older age and seropositivity before transplantation.

The median time of development of $/= pneumonitis after ,/T is

about ? days (range of t"o "eeks to four months).

Typical chest x*ray findings include multifocal diffuse patchy

infiltrates.

igh*resolution $T scan sho"s parenchymal opacification or multiple

small nodules.,ronchoalveolar lavage is diagnostic in most cases.

&ther than pneumonitis $/= infection in post*,/T patients also

manifests as upper and lo"er gastrointestinal ulcers bone marro"

suppression. arthralgias. myalgias. #nd 5sophagitis

$onsider cytomegalovirus ( $/=) infection in a patient "ith

mononucleosis*like symptoms. #typical lymphocytes on the blood

smear. and a negative monospot test.


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1nlike 5,=*associated mononucleosis.

Sore throat and lymphadenopathy are uncommon in $/= infection.

,3/H$

The most common organ involved in graft*versus*host disease

(;=6) is the skinG

skin rash is almost al"ays seen.

The other organs commonly involved include the intestine liver and

lung.

ung involvement is seen in chronic ;=6 and manifests as

bronchiolitis obliterans.

tests (or HI/

5IS# is the preferred screening test for I= infection because

its sensitivity is greater than JJ.JK.

4estern blot is a confirmatory test for I= infection. Its

specificity is greater than JJ.JJK "hen combined "ith 5IS#.

I= viral load is an indicator of disease progression.

=ery high viral loads (:ABBBBB copies3ml) is associated "ith a poor

prognosis.

#bsolute $6? count is an indicator of disease progression.The risk of #I6S*opportunistic infections is high "hen the $6?

count is less than EBB cells3jC.

atients "ith a $6? count belo" EBB cells3jC should be

started on antiretroviral therapy.

E? antigen assay is not used for screening purposes.


12/39

4henever a healthcare "orker is exposed to the blood or blood

products of I=*infected patients testing for I= should be

performed immediately to establish the personHs baseline serologic

status.'epeat testing should be performed after L "eeks months and L

months.

&nce the blood is dra"n for baseline serological studies

I= postexposure prophylaxis should be started "ithout delay.

rophylaxis includes a combination of t"o or three drugs.

T"o nucleoside reverse transcriptase inhibitors are typically

used.

If a third drug is used it is usually a protease inhibitor.#ddition of a third drug increases the efficacy of the t"o*drug

regimen.

Three*drug prophylaxis may be routinely used in all patients but is

particularly indicated for exposures that pose an increased risk for

transmission as in this vignette (i.e. very lo" $6? count high viral

load and high*risk type of injury such as deep percutaneous injury

"ith a hollo"*bore needle).

The common acute life*threatening reactions associated "ith I=

therapy include-

A . didanosine*induced pancreatitis

E. abacavir*related hypersensitivity syndrome

. lactic acidosis secondary to the use of any of the +'Tis?. Stevens*Cohnson syndrome secondary to the use of any of the

++'Tis

. nevirapine*associated liver failure

L.$rystal*induced nephropathy is a "ell*kno"n side effect of

indinavir therapy.


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. Bacillary angiomatosis,right red. firm. friable. exophytic nodules in an I= infected

patient are most likely bacillary angiomatosis.

,acillary angiomatosis is caused by ,#'TI+5# . # ;ram*negative bacillus.

6iagnosis is made via tissue biopsy and microscopic identification of

organisms and the characteristic angiomatous histology.

5xtreme caution must be exercised in biopsying these lesions

because they are prone to hemorrhage.

,# can be treated "ith a variety of antibiotics "hich lead to

involution of the lesions.

&ral erythromycin is the antibiotic of choice

7aposi sarcomaThe cutaneous lesions of 7aposi sarcoma are asymptomatic elliptical

and arranged linearly.

$ommonly involved regions include the legs face oral cavity and

genitalia.

The lesions begin as papules and later develop into pla!ues ornodules.

The color typically changes from light bro"n to violet.

There is no associated necrosis of the skin or underlying structures.

In the 1S this disease is most commonly seen in homosexual I=

patients.

7aposi sarcoma in I= patients is caused by human herpesvirus D.

4neumocystisneumocystis may cause nodular and papular cutaneous lesions of the

external auditory meatus in immunocompromised (I=) patients.

4ith use of trimethoprim*sulfamethoxa%ole. neumocysfis infection

is highly unlikely.

#lthough initiation of antiretroviral treatment is indicated.

it is important to treat the $ first.


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Failure to start treatment in patients "ith $ is associated "ith

almost ABBK mortality. ##'T is usually started after the acute

episode is over.

5ncapsulated bacteria especially 4neumococcus are the most

common cause of pneumonia in I= patients.

&ral trimethoprim*sulfamethoxa%ole (T/*S/M) is effective in

preventing neumocystis pneumonia ($) in transplant patients.

It may also prevent toxoplasmosis nocardiosis and other infections

(e.g. urinary tract infections and pneumonia).

#ll post transplant patients should receive prophylaxis "ithT/*S/M.

;anciclovir or valganciclovir can be used to prevent $/=

infections

$iarrhea in HI/

$auses of diarrhea in I= patients include non*opportunistic

infections (e.g .. Salmonella. $ampylobacter. 5ntamoeba. $hlamydia

Shigella. and ;iardia Iamblia).

opportunistic infections (e.g .. $/=. $ryplosporidium.3sopora belli.

D3aslocyslis. /#$. erpes simplex virus. #denovirus. and I= itself).

and non*infectious causes

(e.g .. 7aposi sarcoma or lymphoma of the ;l tract).

ematoche%ia and lo"er abdominal cramps are usually due to colonic

infection "ith $/=. $lostridium difficile. Shigella. 5 hislofylica. or$ampy3obacter.

In an I=*infected patient. bloody diarrhea and a normal stool

examination are highly suspicious for $/= colitis and "arrant a

colonoscopy "ith biopsy

$/= is a common opportunistic pathogen in I=*infected patients

and may cause esophagitis. gastritis. colitis. proctitis. or small bo"el

disease.


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In this case. the patient presents "ith the typical presentation of

$/= colitis- chronic bloody diarrhea. abdominal pain. and a $6? count

less than B cells3IC.

$olonoscopy sho"s multiple mucosal erosions and colonic ulceration.,iopsy sho"s the presence of large cells "ith eosinophilic

intranuclear and basophilic intracytoplasmic inclusions (>o"lHs eye>

effect).

The treatment of choice is ganciclovir.

Foscarnet is used in case of ganciclovir failure or intolerance.

This I=*infected man is suffering from unexplained fever andcough.

The differential includes /ycobacterium avium complex

/ycobacterium tuberculosis disseminated cytomegalovirus

infection and non*odgkinHs lymphoma.

$larithromycin in combination "ith ethambutol is used as treatment

for /ycobacterium avium complex infection.

ulmonary cavitation in an I=*inFected patient can be caused by a

number of different organisms. Including-/ycobacterium

tuberculosis atypical mycobacteria +ocardia gram*negative rods

and anaerobes.

I= patients are at high risk for tuberculosis. # positive 6 test

(skin induration of greater than mm in I= patients) re!uiresprophylaxis "ith isonia%id (and pyridoxine) for J months.

yridoxine is added to the regimen to prevent possible neuropathy

caused by isonia%id.

yridoxine does not prevent isonia%id*induced hepatitis. and thus

periodic liver function tests should be monitored in these patients.


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eripheral neuropathy may present as tingling in the extremities.

numbness and ataxia. It is a kno"n side effect of isonia%id.

For this reason. all patients "ho are started on anti*tubercular

therapy are also started on vitamin supplements.especially pyridoxine ( A B mg3day).

If the peripheral neuropathy has already developed.

the dose of pyridoxine is increased to A BBmg3day.

dysphagia5odynophagia in an HI/ patient

The most common cause of dysphagia3odynophagia in an I= patientis candidal esophagitis.

If these symptoms develop. an initial one* to tvvo*"eek course of

empiric oral flucona%ole should be prescribed.

If symptoms persist despite therapy endoscopy "ith biopsy should

be performed to investigate other possible etiologies.

I= patients "ith severe odynophagia but "ithout oral thrush are

likely to have ulcerative esophagitis. "hich is most often caused by

cytomegalovirus ( $/=).

The triad of -

A) focal substernal burning pain "ith odynophagia

E) evidence of large shallo" superficial ulcerations.

) presence of intranuclear and intracytoplasmic inclusions is

diagnostic of $/= esophagitis.

The treatment of choice is I= ganciclovir.

I=*infected patients "ho develop esophagitis are first

started on flucona%ole directed against candidiasis

Failure to respond to a * day course of oral flucona%ole

"arrants further investigation "ith endoscopy.


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Herpes simple0 virus ,HS/ esophagitis

erpes simplex virus (S=) esophagitis is also a common cause of

esophagitis in I= patients.The ulcers of S= esophagitis are usually multiple small and "ell

circumscribed and have a >volcano*like> (small and deep) appearance.

$ells sho" ballooning degeneration and eosinophilic intranuclear

inclusions.

#cyclovir is the treatment of choice.

herpes simple0 virus ,HS/ encephalitis.

S= most fre!uently affects the temporal lobes of the brain.

#s a result features such as bi%arre behavior and hallucinations may

be present.

The disease is usually abrupt in onset. "ith fever and impaired

mental status.

/eningeal signs are fre!uently absent.

$erebrospinal fluid ( $SF) findings are nonspecific. "ith lo" glucose

levels and pleocytosis.

The diagnostic test of choice is $SF polymerase chain reaction ($')

for herpes simplex virus 6+#. not viral culture9

o"ever. "henever there is a suspicion of S= encephalitis.

I= acyclovir should be started "ithout delay. ,? $'

)osterShingles is caused by reactivation of the varicella*%oster virus.

Fallo"ing the primary infection (chicken pox).

the virus remains latent in the dorsal root ganglia.

# decrease in cell*mediated immunity (e.g. older age stressful

situation I= lymphoma)

can allo" the virus to reactivate and spread along the sensory nerve.


18/39

This accounts for the typical unilateral dermatomal distribution of

the pain and rashG T to are the most fre!uently involved

dermatomes.

atients often develop pain or discomfort in the affected areabefore the onset of rash.

=alacyclovir is the drug of choice for treating herpes %oster.

o"ever acyclovir is less expensive and is also effective.

5arly antiviral therapy reduces the duration of rash and associated

pain. and is also thought to reduce the likelihood of developing post

herpetic neuralgia.

ostherpetic neuralgia can be prevented and3or treated "ithtricyclic antidepressants such as amitriptyline or nortriptyline along

"ith acute antiviral therapy.

+acterial meningitis.

The most appropriate empiric antibiotic regimen is vancomycin.

ceftriaxone. and ampicillin.

=ancomycin N ceftriaxone is ideal for community*ac!uired bacterial

meningitis in adults and children since it covers the three most

fre!uent etiologic agents- Streptococcus pneumoniae. aemophi3us

inf3uen%ae. #nd +eisseria meningitidis

#mpicillin is included in the empiric regimen to cover isteria

monocyfogenes . "hich is also an important cause of meningitis in

patients older than .

&ther patients "ho are at risk for isteria meningitis include

immunocompromised patients patients "ith malignancies (especially

lymphoma). and patients taking corticosteroids


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I= cefotaxime N ampicillin is the ideal antibiotic regimen for patients

less than three months of age.

I= cefta%idime N vancomycin is the ideal antibiotic regimen forhospitali%ed patients "ho develop meningitis. especially after

neurosurgery.

These drugs cover (seudomonas and Staphylococcus aureus.

respectively.

$iarrhea

6iarrhea in travelers is most commonly due to contaminatedfood and "ater. #lthough a variety of agents (e.g .. bacteria.

viruses. parasites) are possible. enteroto0igenic ". coli is the

most fre!uent cause of travelerHs diarrhea.

It is a rare cause of diarrhea in the 1S

#bdominal tenderness "ith an absence of fever is most

suggestive of infection "ith "nterohemorrhagic ". coli,"H"C.

Shigella. Salmonella. and $ampylobacter can also cause bloody

diarrhea but often result in fever and3or lack of abdominal pain.

55$ is different from other strains of 5. coli because it produces

a Shiga toxin that causes its propensity to cause bloody diarrhea.

The most common serotype of 55$ in the 1S is BAO-O.

/ost cases are caused by ingestion of undercooked ground beefalthough it is not uncommon for patients to not remember a

particular exposure.

otential complications include development of emolytic*1remic

Syndrome (1S) or Thrombotic Thrombocytopenic urpura (TT).

A stool culture could be considered to confirm the diagnosis and

determine antibiotic susceptibilities.


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suspect Bacillus cereus "henever you read about a patient "ho

eats rice and subse!uently develops nausea and severe

vomiting.,acillus cereus produces a heat*stable toxin in inade!uately

refrigerated cooked rice.

,ecause the illness is due to a preformed toxin symptoms of nausea

and vomiting appear !uickly after consumption of the contaminated

food (bet"een one and six hours after ingestion).

# side from preformed toxins. chemical irritants also produce

abrupt*onset nausea and severe vomiting.

Staphylococcus aureus toxin is present in foods such as dairy.

salad. meat. and eggs.

Symptoms include nausea. vomiting. diarrhea. and abdominal pain.

,ecause S. aureus food poisoning is also due to a preformed toxin.

symptom*onset is rapid. usually "ithin one to six hours after

ingestion.

Clostridium per(ringens is a spore*forming organism.

Its spores germinate in foods such as meats. poultry. or gravy.

Ingestion of such food results in "atery diarrhea due to production

of toxin in the gut.

Symptom onset is later than "ith preformed toxins (D*A? hours

after ingestion).

6iarrhea occurs "ith ingestion of a large number of organisms.

6iarrhea due to /i+rio parahaemolyticus is usually transmitted by

the ingestion of sea(ood.

&ther signs and symptoms include fever abdominal cramps and

nausea.

These clinical features develop after an incubation period of four

hours to four days.

=. parahaemolyticus can cause either "atery or bloody diarrhea.


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Shigella is a very common cause of dysentery in the 1S and is

actually the second most common cause of food*borne illness.

6ysentery due to Shigella usually occurs in daycare centers or other

institutional settings.

4seudomonas aeruginosa

The presence of gram*negative bacilli in the sputum of an intubated

intensive care unit patient "ith fever and leukocytosis should make

you think of possible (seudomonas aeruginosa infection

ttt

Fourth generationcephalosporins (i.e .. cefepime)

a%treonam.

ciprofloxacin.

imipenem3cilastatin.

tobramycin.

gentamicin.amikacin.

iperacillin*ta%obactam

osteomyelitis

#lthough Staphylococcus aureus is the most common cause of

osteomyelitis in children and adults.4seudomonas aeruginosa is a fre!uent cause of osteomyelitis in

adults "ith a history of a nail puncture "ound (especially "hen the

puncture occurs through rubber*soled foot"ear).

ematogenous spread is the most likely pathogenic mechanism of

hematogenous osteomyelitis "hich is typically observed in children.

6irect inoculation of pathogenic bacteria during trauma may beresponsible for post*traumatic osteomyelitis


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In diabetic patients the pathogenic mechanism of osteomyelitis

adjacent to a foot ulcer is contiguous spread of infection.

Leprosy

eprosy is a chronic granulomatous disease that primarily affects

the peripheral nerves and skin.

It is caused by Myco+acterium leprae.

In the early part of the disorder.

it may present as an insensate. ypopigmented pla!ue.

rogressive peripheral nerve damage results in muscle atrophy. "ithconse!uent crippling deformities of the hands.

The most common affected sites are the face. ears. "rists.

buttocks. knees. #nd eyebro"s.

6iagnosis is made by demonstration of acid*fast bacilli on skin biopsy

early syphilis

6ark field microscopy is especially useful in diagnosing primary

syphilis and visuali%ation of the spirochetes confirms the diagnosis.

This patientHs syphilis infection suggests that he may be involved in

high*risk sexual activity also putting him at risk for I= exposure.

#fter proper counseling I= screening using 5IS# should be

offered.

The drug of choice for early syphilis is ben%athine penicillin ;. and asingle I/ dose is sufficient.

For those patients "ho are allergic to penicillin.

doxycycline or tetracycline can be given for A? days.

# single dose of oral a%ithromycin can also be used. but resistance

to a%ithromycin has been reported.


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Secondary syphilis

Secondary syphilis re!uires a high index of suspicion for a clinical

diagnosis.Initial testing is "ith a non treponema9 test (e.g .. '' or =6'). "ith

positive results confirmed "ith a specific treponema test (e.g ..

FT#*#,S test).

Treatment involves 6 doses of ben%athine penicillin. each given

"eekly.

atients occasionally develop the Carisch*erxheimer reaction

(acute febrile reaction "ith headaches and myalgias) in the first E?

hours of therapy.#lternative regimens include doxycycline or a%ithromycin in

penicillin*allergic patients

Some superficial scaling can be present in secondary syphilis. "hich

can be confused for psoriasis.

soriasis usually involves the elbo"s and knees and is not associated

"ith systemic symptoms and lymphadenopathy

hereditary hemochromatosis.

atients "ith hemochromatosis and cirrhosis are at increased risk of

infection "ith isteria monocytogenes.

ossible explanations include increased bacterial virulence in the

presence of high serum iron and impaired phagocytosis due to iron

overload in reticuloendothelial cells.

Iron overload is also a risk factor for infection "ith 8ersinia

enferocolifica and septicemia from =ibrio vulnificus both of "hich

are iron*loving bacteria


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Intermittent catheteri%ation

Intermittent catheteri%ation is associated "ith a significantly lo"er

risk of urinary tract infections (1TI) as compared to the use ofind"elling catheters in patients "ith spinal cord injuries.

#lthough each passage of the catheter can introduce bacteria into

the bladder ind"elling catheters carry a greater risk of infection.

This is due to the ability of bacteria to form a biofilm along the

catheter "all that can reach the bladder "ithin E? hours of

insertion.

;enerally the longer the catheteri%ation the greater the risk of

bacteriuria.#pplication of antibacterial creams to the urethral meatus or

antibacterial "ashes of external genitalia are not helpful in

decreasing the incidence of bacteriuria or the risk of 1TI.

in(ective endocarditis

Staphylococcus aureus is the major cause of acute infective

endocarditis in I/ drug a+users.

Injection drug users are prone to get tricuspid endocarditis caused

by S. aureus. Fragments of the vegetation can emboli%e to the lungs

causing the characteristic nodular infiltrate "ith cavitation.

Staphylococcus epidermidis is the most fre!uent cause of

infective endocarditis in patients "ith prosthetic valves.

Staphylococcus saprophytic usually causes urinary tract

infections in young "oman.

"nterococcus is an important but less fre!uent cause of

infective endocarditis.

Streptococcus +ovis endocarditis is associated "ith colorectal

cancer. $olonoscopy should be pursued For further evaluation


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/iridans group streptococci are a fre!uent cause of subacute

bacterial endocarditis (S,5) in patients "ith pree0isting

valvular disease.

/iridans group streptococci (most commonly S. mulans) are themost common cause of endocarditis follo"ing dental

procedures

Four members of the viridans group cause I5- Streptococcus mitis

S. sanguis S. m ulans and S. salivarius.

S. mulans also causes dental caries.

Mitral regurgitation is the most common valvular abnormality

observed in patients "ith infective endocarditis not related to I=drug abuse

4henever an infective endocarditis is suspected empiric antibiotics

should be administered a(ter dra7ing the blood for culture

=ancomycin is the initial empiric antibiotic of choice

;entamycin is often added to regimens for endocarditis because of

its synergistic effect.

Actinomycosis

#ctinomycosis is an infection caused by Actinomyces israelii.

These anaerobic. ;ram*positive. ,ranching bacteria can present "ith

an infection in the cervicofacial. thoracic. or abdominal region.

The infected area usually begins to drain fluid containing sul(ur

granules. "hich appear yello".The treatment is high*dose penicillin for L*AE "eeks

yperbaric oxygenation is not used to treat actinomycosis.

yperbaric oxygen (,&) therapy is generally used to treat the

>bends> from deep sea diving carbon monoxide poisoning slo"*

healing ulcers.


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LymeThe risk of developing a tick*borne disease is lo" if the tick is

attached for @E? hours.

The techni!ue recommended by the $enters for 6isease $ontrol andrevention is to grasp the tic2 7ith t7ee)ers as close to the skin as

possible and then remove the tick using steady up"ard pressure.

Some studies suggest that mouthparts that break off and remain in

the skin can be left alone because the infective body of the tick is

no longer attached.


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$rushing t"isting or puncturing the tick may increase the risk of

infection by releasing infectious fluids from its body into the skin

and is therefore discouraged.

erythema migrans ,"M

5/ is pathognomonic for yme disease.It is the only manifestation that allo"s for clinical diagnosis "ithout

laboratory confirmation.

,lood cultures for , burgdorferi are not available in most clinical

laboratories and are not recommended.

$o0ycycline is an excellent treatment option for most patients as it

has the advantage of simultaneously preventing or treating


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coexisting human granulocytic anaplasmosis an infection also carried

by I. scapularis.

o"ever. doxycycline is contraindicated in young children as "ell as

pregnant and lactating "omen because it can cause permanentdiscoloration of teeth and retardation of skeletal development in

exposed children and fetuses

&ral amo0icillin is the treatment of choice in pregnant and lactating

"omen as "ell as children age @D years.

The rash and constitutional symptoms should resolve "ithin "eeks

of treatment.

regnant patients should be reassured that yme disease is not

kno"n to cause congenital anomalies or fetal demise.

Malaria/alaria is a proto%oal disease caused by genus plasmodium. "hich is a

',$ parasite and is transmitted by the bite of infected Anopheles

mos!uitoes.

It is the most important parasitic disease and is endemic in most of

the developing countries of #sia and #frica.

Four species of lasmodium. vi%. (. falciparum. (. vivax. (.ovale. and

(. malariae can cause malaria.

/ost of the deaths are due to falciparum malaria "hereas

vivax and ovale are responsible for several relapses.

$yclical fever is hallmark of malaria and it coincides "ith ',$ lyses

by the parasites.

Fever occurs every ?D hours "ith . vivax and . ovale andevery OE hours "ith . malariae.

"hereas periodicity is generally not seen "ith . falciparum.

The typical episode consist of a cold phase characteri%ed by chills

and shivering.

follo"ed by a hot phase characteri%ed by high grade fever. follo"ed

E*L hours later by a s"eating stage characteri%ed by diaphoresis


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and resolution of fever. +ausea. vomiting. headache. anorexia.

malaise and myalgia are commonly seen.

In people from endemic areas. anemia and splenomegaly are common

findings.=itals "ould sho" hypotension and tachycardia.

#ll travelers to malarious regions should be prescribed antimicrobial

prophylaxis.

$hloro!uine*resistant (lasmodium falciparum is particularly

common in Sub*Saharan #frica and the Indian subcontinent

(e.g .. India. pakistan. and ,angladesh).

It is not common in the 1S. /eflo!uine is the drug of choice for chemoprophylaxis against

chloro!uine*resistant malaria.

To be effective. prophylaxis should be started one 7ee2 +e(ore

travel and continued until (our 7ee2s a(ter departure from an

endemic area.

Chloro8uine is the drug of choice for chemoprophylaxis in regions

"ith chloro!uine*sensitive malaria.

"hile me(lo8uine is given in areas endemic for chloro!uine*resistant

(lasmodium falciparum.

The use of prima8uine (both for prophylaxis and treatment) is

indicated in settings "here malaria is due to (lasmodium vivax or

(lasmodium ovaleG these organisms cause persistent infection in the

liver.

Fansidar is not used for prophylaxis of malaria because of theserious side effects

(Stevens*Cohnson syndrome and toxic epidermal necrolysis)

associated "ith it.


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Ba+esiosis

Suspect babesiosis in any patient from an endemic area "ho

presents "ith a tick bite. This illness is caused by the parasite Ba+esia and is transmitted by

the I0odes tic2. It is endemic in the northeastern 1nited States.

Follo"ing a tick bite the parasite enters the patientHs ',$s and

causes hemolysis.

$linical manifestations vary from asymptomatic infection to

hemolytic anemia associated "ith jaundice hemoglobinuria renal

failure and death.

1nlike other tick*borne illnesses rash is not a feature of babesiosisexcept in severe infection "here thrombocytopenia may cause a

secondary petechial or purpuric rash.

$linically significant illness usually occurs in persons over age ?B

patients "ithout a spleen or immunocompromised individuals.

6efinitive diagnosis can be made from a ;iemsa*stained thick and

thin blood smear.

aboratory studies may demonstrate intravascular hemolysis

anemia thrombocytopenia mild leukopenia atypical lymphocytosis

elevated 5S' abnormal liver function tests and decreased serum

complement levels.

The t"o most "idely used drug regimens are !uinine*clindamycin andatova!uone*a%ithromycin (P$3##)


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"hrlichiosis1 or 9spotless #oc2y Mountain spotted (ever19

5hrlichiosis is a category of tick*borne illness that is caused by one

of three different species of ;ram*negative bacteria each "ith adifferent tick vector.

It is endemic in the southeastern south*central mid*#tlantic and

upper /id"est regions of the 1S as "ell as $alifornia.

It usually occurs in the spring or summer.

The incubation period varies from one to three "eeks.

$linical features include fever malaise myalgias headache nausea

and vomiting.

There is usually no rashG hence its description as the >spotless 'ocky /ountain spotted fever.>

abs often sho" leukopenia and3or thrombocytopenia along "ith

elevated aminotransferases.

4henever ehrlichiosis is suspected treatment should be started

"ithout delay

the drug of choice is do0ycycline.

: (ever

P fever is a %oonosis caused by Co0iella +urne(ii.

The main sources of human infection are infected cattle goat and

sheep.

eople at risk include meat processing "orkers and veterinarians.

Infection due to $. burnefii occurs in most areas of the "orld.

/anifestations of P fever may include a flu*like syndrome

hepatitis or pneumonia.

TTT-6&M8$8$I+5


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Cysticercosis$ysticercosis is a parasitic disease caused by the larval stage of the

pork tape"orm Taenia solium.ig farmers are at high risk for neurocysticercosis

It is contracted "hen a person consumes T. solium eggs excreted by

another person.

Humans are the only definitive host for T. solium. meaning that only

humans can become infected "ith the adult tape "orm.

The adult tape "orm lives in the upper jejunum and excretes its eggs

into the personQs feces (intestinal infection).

If an animal consumes these eggs. it becomes an intermediate host."ith larvae encysting in its tissues.

The most common intermediate host is a pig.

Then. "hen humans consume larvae in meat such as infected.

undercooked pork. they can once again develop intestinal infection

"ith the adult tape"orm.

o"ever. if a person (rather than a pig) consumes the T. solium eggs

excreted in human feces.

$ysticercosis results #fter ingestion.

the embryos are released in the intestine and the larvae invade the

intestinal "all.

They disseminate hematogenously to encyst in the human brain.

skeletal muscle. subcutaneous tissue. or eye. (+ote that

cysticercosis is not contracted by eating infected pork. so people"ho do not eat pork can still be affected.)

The most common manifestations of cysticercosis are neurologic.

+eurocysticercosis (+$$) is characteri%ed by multiple. small

(usually @ A cm). fluid*filled cysts in the brain parenchyma.

These cysticerci have a membranous "all and often demonstrate a

characteristic invaginated scolex on neuroimaging.


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Interestingly. +$$ is the most common parasitic infection of the

brain. and is most prevalent in the rural areas of atin #merica. sub*

Saharan #frica. $hina. southern and Southeast #sia. and 5astern

5urope.particularly "here pigs are raised and sanitary conditions are poor.

umans "ith cysticerci are deadend hosts.

5ighty percent of neurocysticercal infections are asymptomatic. and

are accidentally found on brain autopsy.

Hydatid cysts

5chinococcosis is a parasitic disease caused by tape"orm

echinococcus.

Four species of 5chinococcus can produce infection in humans.

the t"o most common being 5. granulosus. causing cystic

echinococcosis. and 5. multilocularis. causing alveolar echinococcosis.

The majority of human infections are due to sheep strain of 5.

granulosus.

for "hich dogs and other canids are the definitive hosts and sheep

are the intermediate hostsG humans are the deadend accidental

intermediate host.

It is most commonly seen in areas "here sheep are raised (sheep

breeders are thus at high risk) and transmission is seen "hen dogs

living in close proximity of humans are fed the viscera of home*

slaughtered animals.

The infectious eggs excreted by dogs in the feces are passed on toother animals and humans.

#fter ingestion of eggs by humans. the oncospheres are hatched

and they penetrate the bo"el "all disseminating hematogenously to

various visceral organs. leading to formation of hydatid cysts.

The liver. follo"ed by the lung. is the most common viscus involvedG

ho"ever. any viscera can be involved.


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ydatid cyst is a fluid*filled cyst "ith an inner germinal layer and

an outer acellular laminated membrane. ;erminal layer gives rise to

numerous secondary daughter cysts.

trichinosis (also kno"n as trichinellosis). a parasitic infection caused by the

round "orm Trichinella.

It is ac!uired by eating undercooked pork that contains encysted

Trichinella larvae.

The disease occurs in three phases.

The initial phase occurs in the first "eek of infection "hen thelarvae invade the intestinal "all.

This phase manifests as abdominal pain. nausea. vomiting. and

diarrhea.

The second phase begins in the second "eek of infection.

It reflects a local and systemic hypersensitivity reaction caused by

larval migration. "ith features such as >splinter> hemorrhages.

conjunctival and retinal hemorrhages. periorbital edema. and

chemosis.

#s the larvae enter the patientHs skeletal muscle during the third

phase. muscle pain. tenderness. s"elling. and "eakness occur.

,lood count usually sho"s eosinophilia.

Ascariasis

#scariasis can also present "ith intestinal symptoms and

eosinophilia. but the triad of periorbital edema. myositis. and

eosinophilia is most suggestive of trichinellosis.

#scariasis more often presents as a lung phase "ith non*productive

cough follo"ed by an asymptomatic intestinal phase.

Symptoms of ascariasis often result from obstruction caused by the

organisms themselves. such as small bo"el or biliary obstruction.


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" histolytica

5 histolytica is a parasite that cause bloody diarrhea. but it can

usually be diagnosed by visuali%ation of tropho%oites on stoolexamination.

$olonoscopy sho"s the presence of Hflask*shapedH colonic ulcers.

Inclusion bodies are not seen.

Cutaneous larva migrans

$utaneous larva migrans or creeping eruption is a helminthic disease

caused by the infective*stage larvae of Ancylostoma +ra)iliense

the dog and cat hook"orm.

Infection occurs after skin contact "ith soil contaminated "ith dog

or cat feces containing the infective larvae.

This disease is prevalent in tropical and subtropical regions including

the southeastern 1nited States.

eople involved in activities on sandy beaches or in sandboxes areparticularly at risk.

Initially multiple pruritic erythematous papules develop at the site

of larval entry follo"ed by severely pruritic elevated serpiginous

reddish bro"n lesions on the skin "hich elongate at the rate of

several millimeters per day as the larvae migrate in the epidermis.

It is most commonly seen in the lo"er extremities but the upper

extremities can also be involved.

Cat scratch disease

$at*scratch disease is caused by ,artonella henselae.

The condition may be transmitted by a cat scratch cat bite or flea

bite.

It is commonly seen in young1 immunocompetent individuals.


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$at scratch disease typically presents as a locali%ed cutaneous and

lymph node disorder near the site of the inoculum "ith very rare

involvement of the liver spleen eye or central nervous system.

# local skin lesion evolves through vesicular erythematous andpapular phases but can be pustular or nodular.

The hallmark of cat scratch disease is locali%ed regional

lymphadenopathy "hich is tender and may be suppurative.

The diagnosis is clinical although a positive ,. henselae antibody

test or a tissue specimen demonstrating a positive 4arthin*Starry

stain supports the diagnosis.

# short course of antibiotics is recommended.

Five days of a%ithromycin has been found to be particularlyeffective.

+,s-

rednisone is used to treat aphthous ulcers

olyvalent pneumococcal vaccine is recommended in all children

and adults "ith I= infection and a $6? count above EBB

cells3micro.

Tuberculosis can also cause a draining infection in this region.

"hich is called scrofulaG therefore. an acid*fast stain must be

done to rule out T,.

$ombination therapy "ith intravenous ceftriaxone and

vancomycin is the empiric treatment for bacterial meningitis.

6rug eruptions can present as morbilliform. urticarial.

papulos!uamous. pustular. and3or bullous lesions.

/ost drug eruptions are not associated "ith sore throat and

lymphadenopathy.


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The patients "ith uncomplicated pyelonephritis can be usually

s"itched to an oral antibiotic after ?D*OE hours of parenteral

therapy

The commercial sex "orker is at high risk for perihepatitis

from gonorrhea and numerous other

sexually*transmitted diseases

Streptococcus pneumoniae is the most common pathogen

causing pneumonia in nursing home patients

only S. aureus is kno"n to cause post*viral 1'I necroti%ingpulmonary bronchopneumonia "ith multiple nodular infiltrates

that can cavitate to cause small abscesses

,ecause patients "ith I6 are at increased risk for other

ST6s most physicians advise that I= '' pap smear and

hepatitis , surface antigen testing also be performed ("ith the

patientHs consent).

4hen there is a history of I= drug abuse hepatitis $ serology

should also be obtained.

# clenched fist injury is a bite "ound to the hand incurred

"hen a personHs fist strikes an opponentHs teeth (also kno"n as

a >fight bite>).

#moxicillin*clavulanate is the antibiotic of choice for

prophylaxis and treatment of infections caused by a human

bite.

These infections are usually polymicrobial and thus coverage

for ;ram positives ;ram negatives and anaerobes should be

provided.


38/39

$lavulanic acid is a beta*lactamase inhibitor and is helpful

against beta*lactamase*producing anaerobes

,ro"n recluse spider bites are characteri%ed by a papule "itherythema at the site of the bite follo"ed by severe ulceration.

$ondylomata acuminata ( anogenital "arts) are caused by the

human papilloma virus. The characteristic lesions are

verrucous papilliform and either skin*colored or pink.

This is in contrast to the lesions of condyloma lata "hich are

flat or velvety.

There are three treatment options for condyloma acuminata-

o A . $hemical or physical agents (e.g. trichloroacetic acid

*florouracil epinephrine gel and podophyllin)

o E. Immune therapy (e.g. imi!uimod interferon alpha)

o . Surgery (e.g. cryosurgery excisional procedures laser

treatment)

The choice of treatment depends upon the number and extent

of lesions.

odophyllin is a topical antimitotic agent that leads to cell

death.

It is teratogenic and thus contraindicated in pregnancy.

Its other adverse effects include local irritation and

ulceration.

4roteus species produce urease. "hich makes the urine

al2aline. This infection is particularly common in patients "ho

live in long*term care facilities and have chronic ind"elling

catheters.

Candida1 4seudomonas. and %le+siella infections are also

common in patients "ith chronic ind"elling catheters but they

do not produce alkaline urine.


39/39

". coli is the most common cause o( !Tis. but it does not

produce urease and thus does not alter the normal acidic p of

urine.

mira infection notes

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