Proteus hauseri- Introduction, Morphology, Pathogenicity, Lab

Introduction

Table of Contents

Proteus hauseri is a Gram-negative, facultatively anaerobic bacillus in the Enterobacteriaceae family. It is closely related to other Proteus species and commonly found in soil, water, and the human gastrointestinal tract. Though less prevalent than P. mirabilis, P. hauseri can cause opportunistic infections—especially in hospitalized or immunocompromised patients.

Morphology

Cellular: Straight to slightly curved rods, 0.4–0.8 µm × 1.0–3.0 µm
Motility: Highly motile via peritrichous flagella; exhibits “swarming” on solid media
Colony Appearance on MacConkey: Pale, non-lactose-fermenting colonies (colorless)
Other Media: On nutrient agar, forms concentric rings due to periodic swarming waves

Pathogenicity

Adhesion & Invasion: Fimbriae and adhesins mediate attachment to urinary epithelium
Enzymatic Factors: Urease production elevates urinary pH, promoting stone formation
Infection Spectrum:

Urinary tract infections (UTI): Especially catheterized patients
Wound infections: Including surgical sites and decubitus ulcers
Bacteremia & Sepsis: In neonates or immunocompromised hosts
Rarely: Respiratory or intra-abdominal infections

Laboratory Diagnosis

Specimen Culture: Inoculate urine, wound swab, or blood onto MacConkey and blood agar; incubate at 35–37 °C.
Colony & Swarming: Observe non-lactose-fermenting colonies with swarming on non-inhibitory media.
Biochemical Tests

Proteus hauseri in wet mount of culture — Fig. Proteus hauseri in a wet mount of culture

Urease positive (rapid)
Indole variable (distinguishes from P. mirabilis)
Phenylalanine deaminase positive
TSI: K/K with H₂S production

Automated ID: MALDI-TOF MS or biochemical panels (e.g., API 20E) confirm species.
Antimicrobial Susceptibility: CLSI disk diffusion or automated broth microdilution, with special attention to AmpC-mediated β-lactam resistance.

Treatment

First-Line:
Trimethoprim-sulfamethoxazole
Fluoroquinolones (e.g., ciprofloxacin)
β-Lactams: Carbapenems or β-lactam/β-lactamase-inhibitor combinations guided by susceptibility
Avoid: Ampicillin or first-generation cephalosporins if AmpC β-lactamase is present
Supportive Care: Hydration, catheter removal, or change in UTIs

Prevention

Aseptic Technique: Especially during catheter insertion and wound care
Catheter Management: Remove or replace indwelling catheters promptly
Environmental Controls: Regular disinfection of hospital surfaces and equipment
Antibiotic Stewardship: Limit broad-spectrum cephalosporins to reduce AmpC induction

Keynotes

Swarming Motility: Unique diagnostic clue on non-inhibitory media
Urease Activity: A Major virulence factor in UTIs and stone formation
AmpC β-lactamase: Watch for inducible resistance to many β-lactams
Opportunistic Pathogen: Primarily affects hospitalized or immunocompromised patients, requiring vigilant infection control

Proteus hauseri-Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes