Clinically important Gram positive bacilliSpore forming1. Bacillus2. Clostridium

Non spore forming1.Corynebacterium2.Listeria3.Lactobacillus

Bacilli w/ branching filaments

1.Actinomyces2.Nocardia

1.BACILLUSBacillus anthracis

Human pathogenIsolation also considered to be clinically significantZoonosis

Bacillus cereusEnvironmental organismContaminates foodCommon cause of food poisoning

Bacillus stearothermophilusTolerates very high temperaturesUsed for quality control of autoclaves

a.Bacillus anthracisLarge bacilli of 1-3

mHistorical

importanceSingle or paired in

clinical isolatesIn vitro –

prominent capsuleHighly resistant

spores

Anthrax Pathogenesis and clinical presentations

Virulence factorsCapsule

(antiphagocytic)Toxin

(oedema & death)

Cutaneous anthraxAbout 20% mortality

Cutaneous anthraxAbout 20% mortality

Gastrointestinal anthraxHigh mortality

Gastrointestinal anthraxHigh mortality

Inhalation anthraxHigh mortality

Inhalation anthraxHigh mortality

Anthrax - Epidemiology

Anthrax - DiagnosisSpecimen

Aspirate or swab from cutaneous lesionBlood cultureSputum

Laboratory investigationGram stainCultureIdentification of isolate

Anthrax – treatment and prevention

Penicillin(Tetracycline /chloramphenicol)

Erythromycine,Clindamicine

PreventionVaccination of animal herdsProper disposal of carcasses

Active immunisation with live attenuated bacilli

b.Bacillus cereusLarge, motile, saprophytic bacillusHeat resistant sporesPre formed heat and acid stable toxin

(Emetic syndrome)Heat labile enterotoxin (Diarrhoeal disease)Lab diagnosis – Demonstation of large

number of bacilli in food

Gastroenteritis

Gastroenteritis

Bacillus cereus clinical presentation

Incubation period < 6 hoursSevere vomitingLasts 8-10 hours

Incubation period > 6 hoursDiarrhoea

Lasts 20-36 hours

EMETIC FORM DIARRHOEAL FORM

CLOSTRIDIUM(ANAROBES)AnaerobicSporingGram positiveDiameter of the spore is larger than the

cell resemble a spindleClostridium is derived from Kloster

meaning spindle

Spores Pleomrhic (elongated, spindle)

Most are obligate anaerobes produce neurohisto toxins

Saprophytes - Most

Some are opportunists - tetanus/gas gangrene/food poisoning

Cl. perfringens - commensal of the intestine

Cl. sporogenes - -do- Can invade the intestine after the death

CLASSIFICATION BASED ON THE TYPE OF

DISEASE PRODUCED A . Tetanus Cl. tetani - Present in soilB. Gas gangrene

Established Cl. perfringens ‘gut’ organism

Cl. septicum Cl. novyi

- Less pathogenic Cl. histolyticum Cl. fallax

- Doubtful Cl. bifermentans Cl. sporogenes

C. Food poisoning 1. Gastroenterritis - Cl perfringens Type

A

2. Botulism - Cl. botulinum/ Soil 3. Pig-bel Cl. perfringens type C

D. Acute colitis - Cl. difficile / gut’ organism

(pseudomembranous colitis)

Commonest cause of ‘nosocomial’ diarrhoea

Gas gangrene C. perfringens type A (Principal),

Capsulated, non-motile

Lecithinase C - toxaemia

Nagler reaction

Colonies with haloes

Colonies withouthaloes

Incorporated withAntitoxins

GAS GANGRENE

Dead tissue, blood clots, foreign matter aerobic organisms

In an injury DEVELOP ANAEROBIC CONDITION

(Exogenous infection) Germination of spores

Gas gangrene

oedema, necrosis, gas production,

toxaemia, myositis

Crepitus

C PerfringensC histolyticum

C septicumC novyii

C Perfringens Alpha toxin(lecithinase)

TETANUS Cause tetanus in both man and animals

disease which effect the nervous system

of the host.

- Agricultural workers and gardeners and

are more prone because the spores are

present in the soil.- At birth under unhygienic conditions baby’s

can get – tetanus neonatorum.

Soil/Intestine/Vagina

Drum stick appearance

Motile with peritrichous flagella

Obligatory anaerobes

Grow on Robertson’s cooked medium

All types produce the same toxin

C. tetani – 10 types based on the H antigens

(CP – 5 types based on the type of toxins, alpha, beta, epsilon, iota).

Susceptibility -

Some strains can withstand boiling for 3hrs/dry heat 1600C for 1hr. but all will destroy at 1210C/15 min.

COMMON FEATURES FOR BOTH CT AND CP

All CP’s produce alpha toxinAll CT’s produce same exotoxin – plasmid mediatedHowever, CP’s got enterotoxins.

Exotoxin of CT has got two components .Tetanolysin – both heat and O2 labile – may act as a leucocidin

.Tetanospasmin – heat labile, but O2 stable (Therefore, can you give an edvantage ? will not get destroyed in the blood).

Spores germinate -------toxin-----motor nerve endings--------along the motor neurones of the peripheral nerve to the anterior horn cells------local tetanus (in the proximity of the wound).

Ascending tetanus – when toxins spreads upwards along the spinal cord towards C.N.S. Gives generalized spasms.

Descending tetanus – when toxin is given IV , spasms will appear in the muscles of the head, neck and spreads downwards.

Clinical symptoms

Early symptom is trismus (lock jaw) – spasms of the masseter muscle- difficulty in opening of the mouth and masticating - rigidity spreads to muscles of the face, neck and truck- risus sardonicus – contraction of the frontails and muscles at the angle of the mouth- back is usually slightly curved (Opisthonotus ?) - Insevere cases violent spasms will last for few seconds to 3-4 mins.- If convulsions appear soon after the initial symptoms, it is very serious.- The spasms gradually intensify and patient may die of

.exhaustion, b. asphyxia or aspiration peumonia - If local tetanus after a wound at the neck, you might think of tuberculous meningitis (irritation and

paralysis is common).

What happens

Toxin acts at the synaptic junction – prevent the synthesis of acetylcholine. Thus, prevents synaptic transmission.

ToxinsTetanolysin - heat and oxygen labile/lyse

RBC/Tetanospasmin - heat and oxygen

stable/highly lethal (for mice 0.0000001 mg) dies within 1 - 2 days

get easily neutralize with antitoxin

GABA GLYCINE

Tetanus

Treatment - 10, 000 units of human tetanus immunoglobulin(HTIG)

Prevention and control

a. Immunization - HTIG 250 - 500 units (to immune patientsonly)

To non-immune adsorbed toxoid followed by

Clostridial food poisonngC. perfringensCarriers for food poisoning strainsSurvival of heat resistant spores in

bulk mealsSporulation in gut - Short IP and

watery diarrhoea for 24-48 hoursBeta toxin production in C.

prerfringens type C – Necrotizing enteritis(Pig bell)

BOTULISMSausage

Food borne botulism(IP 1-2 days)

Infant botulismWound botulism

(IP > 4 days)

8 toxins (A-G)

DiagnosisIsolation of organism in food/faecesDetection of toxin in faeces / serum

Produces BotulismWorld wide distributionFound in soil and occasionally in animal fecesSporese are highly heat resistant ,withstand 100C for 3-5 hrs.Heat resistance is reduced by acid pH or high salt concentrations

ToxinReleased during growth and autolysis of bacteria.It is found in 7 antigenic varieties.A-GThe principle cause for human disease A,B,E/F

A,B - Variety of foodsE - Fish productsC - Limberneck in birdsD - botulism in mammalsToxin is neurotoxic proteinDestroyed by heating at 100C for 20 mins.Action :Block release of Acetylecholine at synapsesand NMJ causing flaccid paralysis.PathogenecityIllness is not an infection.Botulism is an intoxication resulting from the ingestion of food in which C.botulinum has produced toxin.

PSEUDOMEMBRANOUS COLITISVirulence factors

Enterotoxin(Toxin A)

Cytotoxin(Toxin B)

Diagnosis

Clinical suspicionCulture of faecesDetection of toxin

Management

Discontinue antibioticsAmpi/Tetra/ClindaOral metronidazoleOral vancomycin

CORYNEBACTERIA(AEROBES)

- Causes localized inflammation (pseudomembrane, greyish white exudate ) and generalized toxaemia

- Prevalent in baby’s after 3-6 months (that’s why DPT is given at 3, 5, 7 months, boosters at 18 months and at school entry), very high in young children

MorphologyGram/+ve/palisade/Chineseletter arrangement

Irregular swellings at one end -club shaped.

Corynebacteria tend to pleomorphism in microscopic

and colonial morphology.

On blood agar Small granular & gray with irregular edges and may have small zones of hemolysis.

Grow aerobically on ordinary media

a. Corynebacterium diphtheriae

Normal flora of nasopharynx in about 10%

Diphtheria caused when infected by lysogenic bacteriophage

b. DiptheroidsNormal flora of skinUsual contaminants of samplesCan cause disease in ‘compromised’ host

C. ulcerans C. haemolyticum

C. jeikeium

Rare in developed countries/ third world countries

Nose, Nasopharynx, skin aerobic, facultatively anaerobic

Nasal carriers are very dangerous

Loeffler's serum slope Blood telurite agar (black colonies)

Morphological differences

Three biotypes

Gravis (severe)

Inter-medius (intermediate)

Mitis (mild)

Epidemiology

It is rare in developing countries, a disease of the third world countries. Still highly prevalent in the former Soviet Union.

Spread through droplets.

Types of DiphtheriaFaucialLaryngealNasalConjunctivalVulvovaginalOtiticCutaneous around the mouth and the nose

Effect of toxins1. Local2. General

Toxaemia and acts on the myocardium and on motor nerves and adrenals

Complicationsa, pseudomembrane may extend to larynx and

cause obstructionb.myocarditis /PolyneuropathyDegenerative changes in the liver adrenals, kidney's

Pathology

•Toxin is absorbed in the mucus membrane and causes destruction of epethelium and causes a superficial inflammatory respons.

•Necrotic epethelium becomes embeded in exuding fibrin and red and white cells, with bacteria-

•Grayish pseudomembrane is formed over the tonsilasand pharynx and larynx.

•Removal of pseudomembrane - capillary damage and bleeding..

•Regional lymphadynopathy with marked edema of the neck within the membrane bacilli produce toxin.

•This results in distant toxic damage paranchymatous degeneration fatty infiltration & necrosis in heart muscle liver kidney & adrenals.

How to identify the immune persons

Shick test – suitably diluted stabilized toxin intradermally, localized erythema (1-3cm) in 2-4 days, means no or little antibodies

DiagnosisDirect smear - Albert's stainCulture - Loffler's serum slope/blood agar/blood

telurite agar

Check the toxigenicityAnimal inoculation

Death within 96 hrs

Guinea pigs/rabbits

Elek's plate test

Filter paper with antitoxin Precipitation

Strain

Management –

1. Patients - isolation of the patient / bed rest/antibiotic treatment/antitoxins (horse serum)

Penicillin/erythromycin/teracycline/rifampicin/clindamycin

2. Contacts – immunize if not (toxoid) – adults should be shick tested or given low dose as immunization of immune adults can result in severe reaction.

- prophylactic antibiotic – erythromycin- swab nose and throats of contacts

3. Community – immunization

DIPHTHERIA

DIAGNOSIS

Clinical suspicionSwab for cultureToxin production

TREATMENT

PenicillinAnti-diphtheretic serum

Maintaining airwaySupportive

PREVENTION

Immunization(toxoid)

4.Listeria monocytogenes