Anaerobic Bacterial Infections Review

Flashcards covering key anaerobic bacterial infections, including Clostridium difficile, Clostridium perfringens, Clostridium tetani, Clostridium botulinum, and Bacteroides fragilis, their characteristics, pathogenesis, diagnosis, and treatment.

What is a characteristic structural feature of Clostridium difficile?

Motile, Gram-positive rods with oval subterminal spores.

What are the primary virulence factors of Clostridium difficile?

Enterotoxin (toxin A) and a cytotoxin (toxin B) from the LCT family; some strains also produce a binary toxin.

What is the typical mode of transmission for Clostridium difficile?

It is contagious, often spread via the fecal-oral route.

What is a common presentation of severe Clostridium difficile disease?

Pseudomembranous colitis.

Why are immunoassays for C. diff toxin A often considered unreliable, and what has replaced them?

Immunoassays are unreliable and have been replaced by PCR assays that target the toxin genes.

What is the recommended treatment for severe Clostridium difficile infection?

Oral metronidazole or oral vancomycin.

What is the characteristic clinical presentation of Clostridium perfringens food poisoning?

A short incubation period (8-12 hours), abdominal cramps, and watery diarrhea, but typically no fever, nausea, or vomiting, lasting less than 24 hours.

How does Clostridium perfringens food poisoning typically result?

From ingestion of meat products contaminated with large numbers (10^8 - 10^9 organisms) of enterotoxin-producing type A C. perfringens.

What condition allows Clostridium perfringens spores to germinate and multiply in contaminated foods?

Holding contaminated foods at temperatures less than 60°C after cooking.

How can the enterotoxin produced by Clostridium perfringens be destroyed in food?

Reheating the food to at least 74° C.

What is a distinctive diagnostic feature of Clostridium perfringens growth on sheep blood agar?

A 'double zone of hemolysis', with an inner zone of complete hemolysis (due to θ-toxin) and a larger outer zone of incomplete hemolysis (due to α-toxin).

Why is antibiotic therapy generally not recommended for Clostridium perfringens food poisoning?

It is a self-limiting disease, and oral rehydration is the primary management.

Where is Clostridium tetani commonly found?

It is ubiquitous in soil.

What is the presenting sign of generalized tetanus due to Clostridium tetani?

Involvement of the masseter muscles (trismus or lockjaw).

What are severe neurological symptoms of tetanus?

Difficulty talking, swallowing, and breathing, neck rigidity, respiratory failure, and persistent back spasms (opisthotonos).

What are the common portals of entry for Clostridium tetani spores into the body?

Wounds contaminated with dirt, feces, or saliva, including puncture wounds, burns, crush injuries, and dead tissue.

What is the primary method of preventing tetanus?

Vaccination with tetanus toxoid vaccine and good wound care.

What type of toxin is responsible for the symptoms of botulism?

Botulinum toxin.

What conditions allow Clostridium botulinum spores to germinate and produce toxin in food products like carrot juice?

Low acid content (e.g., pH 6.0) and being left at room temperature.

What are the characteristic neurological symptoms of foodborne botulism?

Cranial nerve palsies and progressive descending flaccid paralysis, often leading to respiratory failure.

How is infant botulism typically diagnosed?

By detecting botulinum toxin in the infant's feces or serum, or culturing the organism from feces.

What is a critical aspect of treatment for severe botulism?

Adequate ventilatory support to reduce mortality.

Why are patients who recover from botulism still susceptible to future infections?

Protective levels of antibodies do not develop after the disease.

What is a key preventative measure to avoid infant botulism?

Avoiding consumption of honey contaminated with C. botulinum spores.

What type of bacteria is Bacteroides fragilis?

A non-spore-forming, anaerobic, Gram-negative rod-shaped bacterium.

Where is Bacteroides fragilis commonly found in the human body?

It constitutes 1-2% of the normal colonic bacterial microflora in humans.

What types of infections can Bacteroides fragilis cause when it spreads outside its normal habitat?

Extraintestinal infections including abscesses, soft tissue infections, and diarrheal diseases, acting as an opportunistic pathogen.

Why is antibiotic monotherapy often unreliable for treating intraabdominal abscesses caused by Bacteroides fragilis?

Due to poor blood supply within an abscess, which limits antibiotic penetration.

What is an emerging concern regarding antibiotic resistance in Bacteroides fragilis?

The rare but increasing possibility of concomitant carbapenem- and metronidazole-resistant strains, especially in patients with travel history to certain regions.