Bacterial diseases caused by Gram-positive rods

Major pathogens

1. Bacillus
   • Gram-positive endosporing rods; facultative anaerobes or aerobes
   • Virulence factors include capsule (B. anthracis)
   • Produce exotoxins which are responsible for symptoms
   • Gastroenteritis, anthrax
2. Clostridium
   • Regular endospore-forming rods; strict anaerobes
   • Exotoxin responsible for symptoms
   • Colitis, gas gangrene, botulism, tetanus
   • C. septicum: myonecrosis (patients with diabetes, leukemia, colon cancer)
   • C. sordellii: toxic shock syndrome (abortion/childbirth); nosocomial
3. Mycobacterium
   • Regular non-sporing rods, mycolic acid cell wall (acid-fast); aerobes
   • Intracellular growth; host immune response responsible for tissue damage and symptoms
   • Tuberculosis, leprosy, disseminated infections
     • Mycobacterium avium complex (MAC) disease common in immunocompromised patients
     • Tissues, blood crowded with Mycobacteria; organ function impaired
     • Most common Mycobacterial infection in the US!
   • Buruli ulcer: Mycobacterium ulcerans
4. Corynebacterium
   • Irregular non-sporing rods; aerobes or facultative anaerobes
   • Exotoxin responsible for symptoms of diphtheria
   • Diphtheria, opportunistic infections (~30 species)
     • endocarditis, UTI, wound infections
     • muilti-drug resistance, kidney stones
5. Listeria
   • Short rods, often in pairs or short chains
   • Capable of growing from 1 - 45°C
   • Intracellular growth and exotoxins (cytolysins) cause damage
   • Listeriosis: Gastroenteritis, neonatal disease, meningitis
6. Erysipelothrix
   • Thin rods, often in long filaments
   • Common in swine (zoonotic)
   • Erysipeloid: zoonotic skin infection
7. Nocardia
   • Acid-fast Gram-positive rods; filamentous
   • Soil microbes; infection through inhalation & wounds
   • Immunocompromised are most at risk
   • pulmonary disease, cutaneous infections
8. Other Gram-positive rods
   • Rhodococcus, Gordonia, Tsukamurella, Actinomadura, Nocardiopsis, Streptomyces, Tropheryma, Mobiluncus

Major diseases

Most of these diseases fall into a few major pathogenic groups: Bacillus, Clostridium, Corynebacterium, and Mycobacterium.

1. Acne: Propionibacterium acnes
2. Actinomycosis: Actinomyces israelii
3. Anthrax: Bacillus anthracis
4. Botulism: Clostridium botulinum
5. Colitis: Clostridium difficile
6. Diphtheria: Corynebacterium diphtheriae
7. Erysipeloid: Erysipelothrix rhusiopathiae
8. Food poisoning/Gastroenteritis: Bacillus cereus
9. Gas gangrene: Clostridium perfringens
10. Leprosy: Mycobacterium leprae
11. Listeriosis: Listeria monocytogenes
12. MAC disease: Mycobacterium avium complex
13. Tetanus: Clostridium tetani
14. Tuberculosis: Mycobacterium tuberculosis
15. Whipple Disease: Tropheryma whipplei

Case study exercise