Yersinia pestis

• Gram-negative bacillus that exhibits bipolar staining ("safety pin" appearance)
• Colonies have typical "fried-egg" appearance
• Transmitted by Xenopsylla cheopis, the Oriental rat flea
• Treatment is with gentamicin, streptomycin, doxycycline, ciprofloxacin, TMP-SMX, chloramphenicol
  • Beta-lactam antibiotics may appear effective in vitro but are not reliable in vivo