Proteus
๐ About
- Proteus species โ members of the Enterobacteriaceae family, known for their swarming motility ๐ and urease production (hydrolyses urea โ ammonia + COโ).
- Most clinically relevant: P. mirabilis (commonest) and P. vulgaris (less common, more resistant).
๐ฌ Characteristics
- Gram-negative rods, facultative anaerobes.
- Glucose fermenters, non-lactose fermenters โ pale colonies on MacConkey agar.
- Oxidase-negative, catalase-positive.
- Reduce nitrates โ nitrites (basis of dipstick UTI test).
- Highly motile โ form concentric โswarmingโ colonies on agar plates.
- Urease-positive โ alkalinises urine, predisposing to stones.
๐ Source
- Found in human gut flora and in water/soil environments.
- Become pathogenic in urinary tract or wounds, especially in hospitalised or immunocompromised patients.
โ ๏ธ Pathogenicity
- UTIs: Classic presentation.
- Urease โ โ urine pH โ ammonia smell ๐จ.
- Precipitates struvite (magnesium ammonium phosphate) calculi โ staghorn calculi.
- Can lead to recurrent or complicated UTIs.
- Wound/Abdominal Infections: Post-op or immunocompromised โ abdominal abscesses, wound sepsis.
๐ Antibiotic Sensitivity
- Effective options (guided by sensitivity):
- TMP-SMX (common in uncomplicated UTIs).
- Ciprofloxacin (fluoroquinolone).
- 3rd-gen cephalosporins (e.g. ceftriaxone, cefotaxime).
- Aminoglycosides (gentamicin) โ usually in combination.
- Piperacillinโtazobactam for severe infections.
- Carbapenems (meropenem) reserved for multi-drug resistant strains.
- P. vulgaris โ more resistant, esp. to penicillins & 1st-gen cephalosporins.
๐งฌ Resistance
- ฮฒ-lactamase production โ resistance to penicillins.
- Fluoroquinolone & aminoglycoside resistance also seen.
- P. mirabilis = generally less resistant; P. vulgaris = more resistant.
- Always perform susceptibility testing before therapy.
๐ฉบ Management
- Uncomplicated UTIs: Oral TMP-SMX or ciprofloxacin.
- Complicated UTIs / Stones: IV therapy (e.g. ceftriaxone, piperacillinโtazobactam, or carbapenem). Surgical removal if staghorn calculi present.
- Wound infections: Broad-spectrum cover (piperacillinโtazobactam or carbapenem) + wound care/drainage.
- Prevention: Minimise catheter use, strict aseptic technique, good hygiene in hospitals.
โ ๏ธ Exam pearl: *Proteus mirabilis* โ UTI with alkaline urine, ammonia smell + struvite (staghorn) calculi.
Differentiate from *E. coli* UTIs (acidic urine, lactose fermenter).
