clostridium perfringens the agent of - gangrene - food poisoning bacteria features: gpb, capsulate,...

Clostridium perfringensClostridium perfringens

The agent of The agent of - Gangrene - Food poisoning

Bacteria features:GPB, Capsulate, non-motile. Spores: bulgingRapidly growing (doubling time ~ 8min) specially

on soil.

Colonies:Colonies:On blood agar: β-haemolytic, flat, spreading, rough,

translucent colonies with irregular margins.

Determinants of pathogenicity

• 12 exotoxins and an enterotoxin• The major exotoxins: alpha toxin, beta toxin, epsilon-toxin and Theta-toxin.

• Types of the organism (A through E) can be differentiated according to the toxin repertoire.

• Alpha toxin (Lecithinase) is the primary toxin and common to all types of C. perfringens but mostly by type A.

Determinants of pathogenicity

Lecithinase (or phospholipase) degrades Lecithin in cell membrane into PhosphorylcholinePhosphorylcholine and DiglycerideDiglyceride.

• Hyaluronidase produced by C. perfringens breaks down the intraceullar cytoskeleton.

• Collagenase and other proteinases break down muscles and liquiefy.

• Dnase• Enterotoxin

Nagler reactionNagler reaction• It is done in: A Nagler agar plate,

containing 5-10% egg yolk.• It is used to identify strains produceing

α-toxin (phospholipase).• C. perfringens phospholipase causes

turbidity (characteristic precipitate) around the colonies on egg-yolk medium Inhibited by specific antiserum.

One-half of the plate is inoculated with antitoxin to act as a control in the identification.

Heat resistancyHeat resistancy

• Type A strains (causing gas gangrene): produce heat inactivated spores

quickly.

• Food poisoning strains: produce heat resistant spores.

TransmissionTransmission• A saprophyte, occuring in soil,

H2O, decomposing plant, human and animal feces.• Vegetative cells are members of

normal flora in colon and 5% of female genital systems (vagina).

GangreneGangrene• Gangrene is necrosis and putrefaction of

tissues. Gas production forms bubbles of gas in muscle (crepitus) and smell in decomposing tissue.

• Gangrene is mostly a mix infection mainly by C. perfringens but also C. septicum, D. sordelli & other proteolitic clusteridums, cocci, gram negative bacilli…. may be found.

Clinical findingsClinical findings

• Glycogen metabolism: Myonecrosis

Bad smelling exuda, inflamation, very progressive necrosis, fever, hemolysis, Crepitation, hemolytic anemia, severe toxemia, shock.

Crepitation

• Gangrene is associated with war war and truma wounds.and truma wounds.• Also after:Also after:- Illegal abortion Illegal abortion (causing GangreneGangrene or

Toxic shock syndrome)Toxic shock syndrome)

- 1-3 days after infant delivery infant delivery (Endometric infection).

Anaerobic cellulitisAnaerobic cellulitis• This is infection of the dermis and

subcutaneous tissue.

TreatmentTreatment- Antibiotic trapy: Penicillin- Surgery (Ampotasion): Wounds

should be debrided- H2O2- Hyperbaric oxygen therapy (HBOT) - Antitoxin (polyvalent against

different sub-species.)

• Hyperbaric oxygen therapy (HBOT) Hyperbaric oxygen therapy (HBOT) is a medical treatment in which the patient breathes 100% oxygen while inside a pressurized chamber.

Hyperbaric oxygenHyperbaric oxygen

Food poisoningFood poisoning

Food poisoningFood poisoning• Soil and food. Survives cooking and grows to large

numbers in reheated food, especially meat.

• Enterotoxin is produced when more than 108 vegetative cells is eaten. The cells convert into spores in GI. Enterotoxin is a part of spore coat.

• Clinical findings: Clinical findings: Incubation: 8-16 hours Symptoms: watery diarrhea, cramps, little

vomiting. Resolves in one or two days.

Treatment and preventionTreatment and preventionof food poisoningof food poisoning

• Treatment: Symptomatic – No antimicrobial drugs

• Prevention Cooking well

Lab diagnosisLab diagnosis• Smear of necrotic tissue and exudate samples:

large positive G+ rods.• Cultured anaerobically I. Blood agarII.Thyoglicolate(identified with fermentation reactions)• Food poisoning: isolation of similar strains in

large numbers from food sources and faeces.

Clostridium difficileClostridium difficile• GPB • Motile• Long, irregularly (often "drumstick" or

"spindle") shaped cells• Spores: Terminal, bulging• Ubiquitous in nature and especially prevalent

in soil

TransmissionTransmissionUbiquitous in nature and are especially

prevalent in soil.

Commensal bacterium of the human intestine in 2-5% of the population.

DiseaseDiseaseClostridium difficile infection (CDI)

• Antibiotic-associated diarrhea (25% of antibiotic-related diarrhea)

• Antibiotic-associated pseudomembranous colitis

• Nosocomial infection

Determinants of pathogenicityDeterminants of pathogenicity

• Enterotoxin (toxin A) and Cytotoxin (toxin B) (heat and acid-labile proteins)

Both found in patients’ feces with pseudomembranous colitis.

Attach to the intestinal epithelial cells at the microvilli level and are responsible for the diarrhea and inflammation.

Pathogenesis of C. difficile:Pathogenesis of C. difficile: Pseudomembranous colitisPseudomembranous colitis

• A severe infection of the colon, often resulting from eradication of the normal gut flora by antibiotics.

• Antibiotic (Clindamycin and Ampicillin) supress drug-sensitive normal flora, allowing C. difficile.

Pseudomembranous colitisPseudomembranous colitis (PMC) (PMC)

• Acute colitis characterized by the formation of an adherent inflammatory membrane overlying sites of mucosal injury.

• Exudates composed of fibrin, mucin, bacteria and polymorphonuclear leukocytes attach to the mucosal surface.

Clinical findings

• Diarrhea• Pseudomembranes (yellow-white plaques)

on the colonic mucosa.• Visualised by colonoscopy.

Lab diagnosisLab diagnosis• Culture and isolation of C. difficile on Blood agarBlood agar

• Identification of toxins by specific antibody using Enzyme immunoassays (EIAs) for the detection of toxins A and B in fecal material.

• Identification of exotoxins by cell cultures: Cytopatic effects (CPEs)

• PCR

TreatmentTreatment• Withdrew the antibiotics Clindamycin

and Ampicillin.

• Oral metronidazole or vancomycin instead along with fluids.