MICROBIOLOGY

• Aerobic, Gram-negative, urease-splitting rod. It is a non-lactose fermenter, indole-negative, oxidase-negative but catalase- and nitrate-positive.
  • "Swarms" on moist agar (many flagella per organism, see video as an example).
  • The second most commonly isolated Enterobacteriaceae after E. coli in many series.
• Most common species: P. mirabilis (indole negative) causes 90% of infections.
  • Other Proteus spp. are indole positive, e.g., P. vulgaris and P. penneri.
  • Proteus rettgari now a member of Providencia spp., properly Providencia rettgari, often a highly resistant organism.
• It can raise urine pH due to urea-splitting activity.
  • Other organisms commonly capable: Pseudomonas aeruginosa, Klebsiella pneumoniae, and Providencia species
• P. mirabilis is usually inherently resistant to tetracycline, colistin and nitrofurantoin, while 10-20% are resistant to ampicillin or cephalexin. P. vulgaris usually resistant to ampicillin or cephalexin/cefazolin.