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Yersinia (member of Enterobacteriaceae)
  1. Yersinia Pestis
    1. Discovered by Yersin & Kitasato
    2. Gram negative, pleomorphic ( enhanced by 3% NaCl)
    3. Giemsa or methylene blue: bipolar staining “safety pin” appearance
    4. Slime layer (best at 37° C), NM, NS, O2 & Fac AnO2
    5. Dark brown colonies on blood agar: absorption of Hemin
    6. Stalactite growth in oil or ghee broth

A farmer from Himachal pradesh with inguinal lymphadenopathy. On examination multiple small ulcer seen in leg and Which of the following stain would you prefer for bipolar staining (AIIMS Nov 09)
A. KOH                    
B. Gram stain          
C. Wayson’s             
D. Nigrosin


Ans. C. Wayson’s

  1. Determinants of pathogenicity:
a. Fraction I
  1. Heat labile protein
  2. Formed at 37° C
  3. inhibits phagocytosis
    V & W antigens
  4. Plasmid encoded
  5. Inhibit phagocytosis & intracellular killing
  6. Pesticin I, coagulase & fibrinolysin
  7. Ability to synthesize purines
  8. Endotoxin
  9. Guinea-pig toxin
  10. Murine toxin
b. Plague:
  1. “Black death “: extensive cutaneous hemorrhage and gangrene
  2. India: last epidemic in 1994 in Surat
  3. Zoonotic disease
  4. Rodents are the foci
c. Humans: Plague types
  1. Bubonic: Flea bite on legs, most common
  2. Pneumonic: during epidemics of bubonic plague; rarely primary; droplet; haemorrhagic pneumonia;highly infectious, most dangerous
  3. Septicemic: terminal event in bubonic and pneumonic plague
  1. Epidemics usually in cool, humid seasons: “High Flea Index”
  2. Two natural cycles:
  3. Urban or domestic plague: plague intimately associated with human beings and rodents living with them
  4. Wild or sylvatic plague: occurs in nature and in wild rodents independent of human beings; prairie dogs, squirrels, wood rats, mice, gerbils, bandicoots

3. Yersinia Pseudotuberculosis
  1. Motile at 20°C but not at 37°C
  2. Most human infections are caused by serotype I
  3. Human infections: Mesenteric lymphadenitis simulating appendicitis, Erythema nodosum, Generalized disease
4. Yersinia Enterocolitica
  1. Motile at 22°C
  2. 3 types of human disease:
  3. Young children: self limited gastroenteritis or enterocolitis
  4. Older children: mesenteric adenitis and inflammatory terminal ileitis; mimics appendicitis
  5. Adults: bacteremia, meningitis, arthralgia or erythema nodosum

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