CLS04 - Corynebacterium, Listeria, and Similar Organisms

  1. Corynebacterium - General characteristics (morpho, biochem, preferred media)
    • Gram + rods
    • palisades: arranged side-by-side "hot dog package" (nonpathogenic)
    • catalase +
    • Non-acid-fast
    • Non-spore forming
    • Full growth on 5% sheep blood agar, less/smaller growth on chocolate agar
    • *NOTE - use this comparison for ID
    • Lipophilic species grow larger with 1% Tween 80
  2. What are the 5 clinically significant Corynebacterium w/ brief description
    • C. diptheriae: pharyngitis with exudative membrane
    • toxin production
    • only carried by humans
    • C. jeikeium: septicemia, skin infections, and immunocompromised
    • C. ulcerans: bovine mastitis, RARELY diptheria-like sore throat
    • C. urealyticum: UTIs, wound infections in immunocompromised (or alkaline vag)
    • C. pseudotuberculosis: Zoonotic infections
    • suppurative granulomatous lymphadentis
  3. Briefly describe cultivation of Corynebacterium diptheriae
    • Selective/differential media used if suspected
    • Loeffler medium: colonies will appear gray/white
    • Cystine-tellurite blood agar: halo produced
    • Modified Tinsdale agar: halo produced
    • *NOTE - slight CO2 for incubation on BAP/Choc
  4. Loeffler agar - use? Important ingredients?
    • Enriched medium
    • For cultivation of Corynebacterium diptheriae, especially for detection of metachromatic granules (bright blue granules after meth blue stain)
    • includes horse serum, dextrose (for fermenting)
  5. Cystine-tellurite blood agar - use? Important ingredients?
    • Selective/differential medium
    • For isolation/ID of Corynebacterium diptheriae
    • Includes sheep blood, L-cysteine (enhances H2S production), Potassium tellurite
    • Potassium tellurite: selective for corynebacterium (inhibits commensal respiratory flora and gram -)
    • differential - C. diphteriae reduces tellurite, other diptheroides don't
  6. Modified Tinsdale agar (TIN) - use? Important ingredients?
    • Selective/differential medium
    • For primary isolation/ID of C. diphtheriae
    • *TURNS BLACK with HALO around colonies
    • Includes Cystine and sodium thiosulfate (differntial for H2S)
    • Potassium tellurite: selective for corynebacterium (inhibits commensal respiratory flora and gram -)
    • differential - C. diphteriae reduces tellurite, other diptheroides don't
  7. What are diphtheroids?
    Nonpathogenic Corynebacteria commensals that resemble C. diphtheriae in appearance
  8. What Bacilli arrangements might indicate Corynebacteria?
    • Diptheroids: found in palisades (hotdog package)
    • C. diphteriae: form 90deg angles (X, Y, "chinese letters")
    • *NOTE - other bacteria can as well, don't be fooled.  Better to find metachromatic granules
  9. What are metachromatic granules?
    • Bright blue granules found in C. diphtheriae bacteria after methylene blue stain
    • Phosphage granules take up dye more intensely
    • Appears as cocci (several dots of bright blue)
    • *NOTE - this is why you do gram stain first!
  10. What is required for definitive diptheria identification in a patient?  How?
    • Demonstration of toxin production
    • Guinea pig lethality test (old)
    • ELISA, Tissue Culture Cell Test, PCR (not common)
    • Elek test (most common)
    • Elek test: immunodiffusion test (look for lines of precipiation)
    • Unknown and controls are streaked in straight lines, 10mm apart on low-iron medium
    • Filter paper w/ diptheria antitoxin is laid across the center of the lines at right angles
    • plates incubated and examined for lines of precipitation at 45 degrees from filter paper
    • *NOTE - test is very sensitive to reagants and antisera, only performed in certain reference labs
    • *NOTE - controls are both C. diphtheriae, one toxigenic, one nontoxigenic
  11. Corynebacterium diphtheriae treatment/prevention
    • Immunization: TDAP (2 months, 4 months, 6 months, 15-18 months, 4-6 years, boosters as needed)
    • Treament: intramuscular dose of penicllin (primary)
    • oral erythromycin
    • anti-toxin
  12. Listeria monocytogenes - found? micro appearance? Colony morphology?
    • Found: soil, water, GI tract animals/humans, milk, raw veggies, cheese, meats (fridge)
    • micro: Gram + short bacillus, single or diplo
    • colony: Small,round colonies
    • Cold enrichment (grows 0.5-45C)
    • B hemolytic
    • Tumbling motility: tumbling motility on wetmount at RT (ends at 37C)
  13. What is the primary virulence factor of L. monocytogenes?  Why is it a problem?
    • Listeriolysin O: allows organism to live inside WBC, then escape at a later time
    • this lets them travel with WBC to blood stream and potentially enter CNS or placenta
  14. How does L. monocytogenes typically affect various populations?
    • Healthy adults: usually asymptomatic
    • Transient colonization
    • Pregant women: have depressed immunity
    • Flu-like symptoms, bacteria enter uterus/fetus
    • Potential for still-birth/abortion
    • Immunocompromised adults: often fatal
    • Meningitis, Bacteremia
    • Neonates: transplancental exposure
    • early onset disease - sepsis immediately following brith, often fatal
    • late onset disease - meningitis days/weeks after birth, often fatal
  15. How is L. monocytogenes processed from planetal/other tissue?  Why?
    • Cold enrichment is used to enhance recovery
    • NB at 4C for weeks/months (that's a looooong time)
    • Isolation is difficult
  16. Listeria colonial morphology and specific media?
    • Sterile site specimen cultured on BAP (B-hemolytic) or specialized media (chromogenic agar, Listeria-selective media)
    • Appears as a mercury drop on Oxford agar
    • Very small B-hemo on BAP (may need to move colony to see!)
  17. Important/identifying biochem characteristics of L. monocytogenes?
    • Webmount tumbling!
    • Tube umbrella motility!
    • 6.5% NaCl resistant (many other gram + are inhibited)
  18. What is the best prevention of L. monocytgenes?
    • Heat leftover and ready-to-eat foods (L. monocytogenes replicates at 4C)
    • Immunocomp/preggos should avoid: soft cheese, lunch meats, etc
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CLS04 - Corynebacterium, Listeria, and Similar Organisms
CLS04 - Corynebacterium, Listeria, and Similar Organisms