bacteriology tree
- Cocci:
- Catalase+: breaks down H2O2
- Staphylococcus: grape-like clusters
- Coagulase+:
- Staph. aureus (beta hemolytic, yellow on mannitol salt agar; protein A inhib. phagocytosis by binding Ig Fc and destroys GI epithelium’s ability to regulate water/electrolytes → diarrhea; common in nose; prosthetics → osteomyelitis)
- coagulase-:
- Novobiocin-resistant:
- Staph. saphtophyticus (“honeymoon cystitis”)
- novobiocin-sensitive:
- Staph. epidermidis (skin → acute endocarditis; prosthetics → osteomyelitis)
- Novobiocin-resistant:
- Coagulase+:
- Staphylococcus: grape-like clusters
- catalase-:
- alpha-hemolytic: partial hemolysis = greenish on blood agar
- Optochin-resistant:
- Strep. viridans
- optochin-sensitive:
- Strep. pneumoniae (IgA protease to survive on mucosal surface; MCC meningitis in 6mo-60+)
- Optochin-resistant:
- beta-hemolytic: complete hemolysis = yellowish/clear on blood agar (*Streptococcus is usually in pairs or chains)
- Bacitracin-resistant:
- Strep. agalactiae (GBS)
- bacitracin-sensitive:
- Strep. pyogenes (GAS; M protein of capsule helps S.py evade humoral immunity and phagocytosis by binding fibrinogen; C5a peptidase inactivates anaphylatoxin decreasing inflammatory response; Strep throat and Rheumatic Fever)
- Bacitracin-resistant:
- gamma-hemolytic:
- Strep. bovis
- Enterococcus (GDS; cocci in chains; black on bile esculin agar)
- Peptostreptococcus
- alpha-hemolytic: partial hemolysis = greenish on blood agar
- Catalase+: breaks down H2O2
- Bacillus:
- Spore-forming:
- Aerobic:
- Bacillus (chains; virulence factors are capsule and toxin)
- B. cereus (fried rice; enterotoxin destroys GI epithelium’s ability to regulate water/electrolytes → diarrhea)
- B. anthracis (exotoxin “edema factor” obtained via plasmid increases cAMP)
- Bacillus (chains; virulence factors are capsule and toxin)
- anaerobic:
- Clostridium
- C. botulinum (botulinum toxin blocks ACh release causing flaccid paralysis; C2 enterotoxin obtained via phage destroys GI epithelium’s ability to regulate water/electrolytes → diarrhea)
- C. tetanus (tetanospasmin obtained via plasmid blocks glycine release causing spastic paralysis)
- C. perfringens (gas gangrene; enterotoxin destroys GI epithelium’s ability to regulate water/electrolytes → diarrhea)
- C. difficile (pseudomembranous colitis caused by Clindamycin, etc and treated by Metronidazole; enterotoxin destroys GI epithelium’s ability to regulate water/electrolytes → diarrhea)
- Clostridium
- Aerobic:
- non-spore-forming:
- Aerobic:
- Corynebacterium (club/”Chinese-letter”-shaped; acid-fast; black on Tellurite agar, Loeffler’s coag. serum)
- Lactobacillus (in breast milk and birth canal; causes gingivitis)
- Listeria (Catalase+, beta hemolytic, grows in low temperatures, facultative INTRACELLULAR organism, listeriolysin O to escape phagolysosome; tumbles in broth; found in soft-cheeses and meats; beware in pregnancies → meningitis)
- Nocardia (filamentous, branching; weakly acid-fast)
- anaerobic:
- Actinomyces (filamentous, branching; “Farmer’s Lung”)
- Aerobic:
- Spore-forming:
- Spirochetes: gram- wall, helical, endoflagella within periplasm, seen via dark-field microscopy
- Borellia (facultative intracellular)
- B. burgdoferi (Lyme disease, from Ixodes tick)
- Leptospira (silver stain)
- Treponema (not cultured)
- T. pallidum (Syphilis; antibodies attack cardiolipin)
- Borellia (facultative intracellular)
- Obligate intracellular: gram- wall, unable to produce own ATP
- Anaplasma (aerobic, arthropod-born; infects PMNs/leukocyte → morulae; prevents lysosomal fusion and remains in vacuole)
- Chlamydia (spore-like elementary body, no PG)
- C. trachomatis (STD and Reiter’s syndrome (“can’t see, can’t pee, can’t climb a tree”))
- Coxiella (in vagina and unpasteurized food; zoonoses via PLACENTA/lactating animals; causes Q fever)
- Ehrlichia (infects monocytes; prevents lysosomal fusion and remains in vacuole)
- Rickettsia (escapes into endothelial cell cytoplasm and multiplies; arthropod-born; causes Rocky Mountain Spotted Fever and Typhus)
- Mycobacteria: mycolic acid wall makes mycobac acid-fast, Auramine rhodamine/Ziehl-Neilson stain; infects macrophages; slow-growing and resistant to drying, chemicals, and germicides
- Mycobacterium tuberculosis (facultative intracellular)
- Mycobacterium leprae (obligate intracellular)
- Mycoplasma and (“fried-egg”-looking) Mollicutes: sterolx3 instead of cell wall, pleomorphic; sensitive to environment; cold (IgM) agglutination; resistant to beta-lactam Abx b/c has no PG (must do Ab serological test to find)
