Medical Microbiology: Gram-Positive Bacilli

Study Notes

Pleomorphic Gram-positive bacilli, aerobic and part of normal flora in respiratory, urinary tract, and skin.
Mostly nonpathogenic, with Corynebacterium diphtheriae as a human pathogen causing diphtheria.
Diphtheria is highly infectious, spreading via droplets with asymptomatic carriers.
Clinical features include throat inflammation, necrosis, and pseudomembrane formation.
Toxigenic strains release Diptheria Toxin, leading to high mortality rates.
Diphtheria vaccine (toxoid) administered to children at 2, 4, and 6 months.
Diagnosis involves Albert's and Gram stain, throat culture on Blood Tellurite Medium, and testing for toxin production.

Gram-positive spore-forming bacilli are aerobic or anaerobic, resilient in dry environments, and commonly found in soil, water, and animal intestines.
Generally saprophytic, with few pathogenic representatives.

Associated with food contamination (rice, meat); produces heat-stable enterotoxin.
Causes food poisoning with vomiting and diarrhea; incubation period ranges from 1-24 hours.
Treatment is supportive, no antibiotics needed.

Small, motile, non-capsulated bacillus; opportunistic pathogen.
Can cause wound infections and sepsis, especially in infants and immunocompromised individuals.
Spores are used as a sterilization efficiency test for ethylene oxide.

Large, non-motile rectangular bacilli, arranged in chains; produces oval, central spores.
Infection occurs through contact with contaminated animals/products; causes cutaneous anthrax or inhalational anthrax with high fatality rates.
Biological warfare agent; diagnosed by culturing specimens from skin ulcers or blood.

Anaerobic, spore-forming, Gram-positive bacilli; mostly saprophytic with a few pathogens among them.
Produce potent exo- and enterotoxins, which can be fatal without treatment.

Causes tetanus; highly fatal with high mortality rates due to potent neurotoxin (tetanospasmin).
Spores germinate in necrotic tissue, leading to local multiplication and remote symptom manifestation.
Treatment includes surgical debridement, antibiotics, antitetanic serum, and vaccination.
Lab diagnosis is based on Gram-stain and culture of specimens from damaged tissues.

Often fatal in developing countries due to poor aseptic technique during childbirth, particularly at the umbilical stump.

Some are toxigenic and invasive, producing enzymes like collagenase and hyaluronidase.
Associated with deep wound infections, gas gangrene, myonecrosis, and bacteremia.
Treatment involves surgical debridement, amputation, and antibiotics; there is no preventative vaccine.
Clostridium perfringens causes food poisoning with enterotoxin, characterized by intense watery diarrhea without fever.