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

Introduction

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:

1. Urinary tract infections (UTI): Especially catheterized patients
2. Wound infections: Including surgical sites and decubitus ulcers
3. Bacteremia & Sepsis: In neonates or immunocompromised hosts
4. 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

1. Urease positive (rapid)
2. Indole variable (distinguishes from P. mirabilis)
3. Phenylalanine deaminase positive
4. 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

Further Readings

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC88947/
2. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/proteus
3. http://www.antimicrobe.org/b226.asp
4. https://www.culturecollections.org.uk/nop/product/proteus-hauseri
5. https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/pathogen-safety-data-sheets-risk-assessment/proteus.html
6. https://medtigo.com/pathogen/proteus-hauseri/
7. https://www.atcc.org/products/13315
8. https://en.wikipedia.org/wiki/Proteus_hauseri
9. https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=183417
10. https://emedicine.medscape.com/article/226434-overview