2nd term lecture,_,vib,_helico,tb,_spiro,rick[1]
TRANSCRIPT
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Microbiology PHT 123
2010-20112nd Term 2nd Semester
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Haemophilus Spp (Blood-loving bacteria)H. Influenzae
Does not cause influenza, Why named so? mistakenly considered the cause of influenza 1890 Pandemic.
Gram negative coccobacilliObligate parasites of manCause hidden disease because:
Does not cause a specific disease Responding first with antibiotics may mask Hib's Difficult to isolate
Fastidious, require X (hemine) and V (NAD or NADP) factors in chocolate agar
A "Rapid Assessment Tool" has been developed by WHO and CDC to make sensible estimates of Hib
H. Ducreyi : STD (soft chancroid) not commonOpportunistic Haemophilus pathogens are rare
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H. Influenza have no specific syndrome but
can cause:meningitis, conjunctivitis, sinusitis, cellulitis, otitis, epiglottitis, pneumonia,
Health Canada and www.cdc.gov/vaccines/pubs
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One of the most transformable genomes
H. Influenza was the first free living organism to have the complete genome sequenced in 1995
The genome consists of 1.8 MB of DNA in a single circular chromosome of which 1.7 code for proteins.
How does it become highly-specific to humans?. Mutations,Transformable by many ways, Phase variation by DNA repeats
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Diagnosis
Microscopy to detect in CSF, synovial fluids, Culturing, difficult, may be not sensitivelatex particle agglutination test (LAT)PCR
H.Influenza Gram stain H.Influenza Choclate agar
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Treatment and prophylaxis cefotaxime , ceftriaxone, ampicillin and
sulbactam, cephalosporins of the second and third generation, or fluoroquinolones are preferred.
Hib conjugate vaccineHib is preventable, but there are two
problems:A shortage of information : difficult to diagnose,
it causes death without being recognizedExpensive: Hib vaccine is expensive
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VibrioV. cholerae, and V. parahaemolyticus are human pathogens
V. cholerae: cause cholera. Comma shaped rods , with Two circular chromosomesWhat is Cholera? Cholera toxin activates adenyl cyclase causing
increased cAMP level and hypersecretion of fluids and electrolytes
Extensive watery diarrhea (15-20 liters/day) called Rice-Water Stool:· Colorless· Odorless· No protein· Speckled with mucus
Source contaminated waters and foodCaused 8 cholera pandemics, example of Pandemic strain is
El TorTreatment and prevention
· Rehydration & supportive therapy· Water purification, sanitation & sewage treatment· Vaccines
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Sack, David, et al. 2004. Seminar: Cholera. The Lancet. 363: 223-233.
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DiagnosisRapid tests
Dark-field microscopyRapid immunoassaysMolecular methods – PCR & DNA probes
Selective/differential culture medium - Thiosulfate Citrate Bile salts Sucrose (TCBS) agarV. cholerae grow as yellow colonies
Biochemical and serological tests
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HelicobacterH. pylori = gastritis, peptic ulcer disease(PUD)
Helical (spiral or curved) corkscrew shape and lophotrichous (tuft at one pole)flagella helps in penetration and colonization of mucosal lining of stomach & duodenum
Acid-inhibitory proteinHydrolyzes urea and inhibits acids in gastrics
• Most gastric cancers are preceded by an infection with H. pylori
Microaerophilic: Change chape to coccoid when exposed to oxygen or upon prolonged culture
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Diagnostic aspectsDetected in endoscopic antral gastric biopsy materialCulture media containing whole or lysed bloodMicroaerophilic does not ferment or oxidize carbohydrates
Triple Chemotherapy (synergism):Proton pump inhibitor (e.g., omeprazole =
Prilosec(R))One or more antibiotics (e.g., clarithromycin;
amoxicillin; metronidazole)Bismuth compound
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Mycobacterium tuberclosis: Tuberclosis 1/3RD of World has it, a global Emergency.
TB what it is, and how it spreads? Outside body Inside body:
Spreads through the air when a person with TB:
Coughs
Speaks
Laughs
Sneezes
Sings
bacilli go to lungs and infect alveoli
Macrophages attack bacteria, but some survive
Infected macrophages form tubercles
Dead cells form granulomas
http://www.cpmc.columbia.edu/resources/tbcpp/abouttb.html.
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Symptoms for Pulmonary TB:There are many types of Tuberclosis, pulmonary
is most important
Perpetual Cough
Fever
Weight loss
Night sweats
Loss of appetite
Fatigue
Swollen glands
Chills
Pain while breathing
Types of TB bacteria include:
Mycobacterium tuberculosis
Mycobacterium leprae
Mycobacterium avium
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Some diagnosticsAcid fast staining, and Lowenstein-Jensen
AgarSkin test- Mantoux testPurified Protein Derivative PPD injected in
forearm and examined 2-3 days laterRed welt around injection indicates infectionExamine medical history, x-rays, and sputum
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Treatment and preventionTake antibiotics for 6-12 monthsPreventative drug to destroy dormant bacteriaFor active TB, 4 medications: isoniazid,
rifampin, ethambutol, and pyrazinamideVaccines (relatively ineffective today)Check with X-ray
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Mycobacterium leprae, Leprosy (uncommon)
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Spirochetes: Treponema, Borrelia, & Leptospira
Spirochete means “coiled hair” Greek. They are tightly coiled like telephone cord, only a fraction of a micron in diameter but hundred of microns long
Twisting Motility by periplasmic flagella (axial fibrils or endoflagella) is a major difference between this and other bacteria
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Spirochaetes: Genus TreponemaGenus: Treponema: Treponema pallidum, causes
syphilis (sexually, or congenitally transmitted), delicate obligate parasite
Stages of Syphilis:1. Primary Chancre lesion is the main sign
2. Secondary rash
3. Latent , no sign but bacteria present
4.Tertiary, very complicated systemic
Treponema pertenue, causes yawsskin lesion
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SpirochetesGenus: Borrelia
Borrelia burgdorferi, Causes a zoonotic vector borne disease called Lyme disease Transmitted by ticks Linear chromosome
Borrelia recurrentis, causes relapsing feverGenus: Leptospira
Leptospira species, causes leptospirosisMain Diagnostic tests for Spirochetes:
Darkfield microscopyFluorescent antibody stainingVDRLWasserman TestHemagglutination tests
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Treatment and control
Penicillin remains drug of choice• WHO monitors treatment recommendations• 7-10 days continuously for early stage• At least 21 days continuously beyond the
early stage Prevention of Mother-child transfer by
barrier methods (e.g., condoms) Prophylactic treatment of contacts
identified through epidemiological tracing
Cautiousness, and morals play significant roles
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Rickettsial DiseasesTransmitted by Arthropod Vectors
Fastidious, obligate intracellular bacteria that grow only on cells, eggs, and tissue cultures
Transmitted by Arthropod VectorsThey are pleomorphic & coccobacillaryDo not show on Gram stain, but can be seen with
either Gimenez or Giemsa stains
Gimenez stain of tissue culture cellsinfected with Rickettsia rickettsii
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Rickettsial Diseases1. Spotted Fever Group
Rocky Mountain spotted fever
– Rickettsia rickettsiiRickettsial pox– Rickettsia akariCanadian typhus– Rickettsia canada
Mediterranean spotted fever
– Rickettsia conoriiSiberian tick typhus– Rickettsia sibericaQueensland tick typhus– Rickettsia australis
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2. Typhus Group
Murine typhus– Rickettsia mooseri (typhi)Epidemic typhus– Rickettsia prowazekiiScrub typhus– Rickettsia tsutsugamushi
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3. OthersQ Fever– Coxiella burnetii• Ehrlichiosis– Ehrlichia canis– Ehrlichia equi– Ehrlichia chafeensis– Several others now identified
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Pathogenesis and Clinical Symptoms
Pathogenesis for all these infections is very similar regardless of species. A vasculitis (inflammation of blood vessel wall) is caused by the invasion and multiplication of the organism in the endothelial and smooth muscle cells of the blood vessels.
Clinical symtomsThrombosis, occlusion, and necrosis of blood vessel wallsThrombocytopenia with hemorrhage
– occurs primarily as a result of platelet consumption as opposed to true (DIC)disseminated intravascular coagulation
Massive capillary leakage, edema, hypotension, and respiratory distress, encephalitis, myocarditis, & nephritis
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Four Prototype Diseases
1. Rocky Mountain spotted fever… by Rickettsia rickettsiiFever, heache, rash…
2. Murine typhus…by Rickettsia typhi3. Epidemic typhus …by Rickettsia prowazekii4. Q fever…by Coxiella burnetii
Occurs in veterinarians, ranchers, and animal researchers from infected placenta of sheep, cattle, or goats (no arthropod vector for C. burnetii). Pneumonia is common
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Weil-Felix Reaction and the bit of a history
Historical known that Proteus antibodis cross-reactive with several of the rickettsiae. Today, Weil-Felix test is not confirmed for rickettsial infection.
In Poland during World War II, two physicians cleverly used killed Proteus bacteria to vaccinate the men of a small town, to induce a positive Weil-Felix reaction.
The occupying Germans feared typhus epidemic and Due the vaccination reaction, the village was saved of a certain destruction. The men were not forced into the army, and the women and children were not forced into the camps.
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Diagnosis and treatmentSpecific & sensitive tests:
Indirect immunofluorescent antibody (IFA)Indirect hemagglutination antibody (IHA)Complement fixation (CF)
TreatmentIn life-threatening rickettsial infections, early antibiotic
intervention is recommended to prevent endothelial damage
Doxycycline, tetracycline, and chloramphenicol are the drugs of choice
Prevention (transmitted by vectors so avoid them)Use of repellents & protective clothing in endemic areasInspection & removal of ticksVaccine for RMSF is available for risk groupsWeekly doxycycline