Pseudomonas putida: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, and Prevention

Introduction

Pseudomonas putida is a versatile, Gram-negative, rod-shaped bacterium primarily known for its bioremediation capabilities but recognized as a rare opportunistic human pathogen. Found globally in soil, water, and plant roots, it thrives in diverse environments due to its unique metabolic endurance.

Morphology and Characteristics

• Cell Shape: Straight, rod-shaped bacilli measuring 0.5 to 1.0 µm in length.
• Arrangement: Occurs mostly as single cells or in end-to-end pairs.
• Gram Reaction: Gram-negative (stains pink/red).
• Motility: Highly motile via multiple polar flagella.
• Pigmentation: Produces pyoverdine, a fluorescent yellow-green pigment.
• Key Distinction: Does not produce pyocyanin (the blue-green pigment unique to Pseudomonas aeruginosa).

• Colony Appearance: Smooth, circular, convex, and creamy-white on standard agar.

Pathogenicity

• Target Audience: Affects immunocompromised patients, newborns, and hospitalized individuals.
• Risk Factors: Associated with medical devices like indwelling urinary or central venous catheters.
• Clinical Manifestations: Causes bloodstream infections (bacteremia), urinary tract infections (UTIs), pneumonia, skin/soft tissue infections, and neonatal sepsis.
• Virulence Factors: Relies on pili for tissue adherence, flagella for invasion, and biofilm formation to shield itself from host immune defenses.

Laboratory Diagnosis

• Specimen Collection: Blood, urine, sputum, or wound swabs depending on infection site.
• Microscopy: Gram staining reveals Gram-negative rods.
• Culture Media: Grows easily on Nutrient Agar and MacConkey Agar (appearing as a non-lactose fermenter).
• Incubation: Grows optimally at 30°C to 35°C; cannot grow at 41°C (unlike P. aeruginosa).
• Biochemical Tests:
  • Oxidase-positive.
  • Catalase-positive.
  • Citrate-positive.
  • Gelatin liquefaction-negative.

Treatment

• Susceptibility: Shows high sensitivity to colistin, gentamicin, amikacin, and meropenem.
• Resistance: Exhibits intrinsic or acquired resistance to aztreonam, levofloxacin, and ciprofloxacin.
• Approach: Requires a mandatory Antimicrobial Susceptibility Test (AST) due to emerging multidrug-resistant strains.
• Device Removal: Prompt removal or replacement of contaminated catheters or implants is required for cure.

Prevention

• Hygiene: Implementation of rigorous handwashing protocols among healthcare workers.
• Sterilization: Strict disinfection of catheters, ventilators, and surgical instruments.
• Environmental Control: Minimizing standing water and damp areas in clinical environments to restrict habitat growth.
• Aseptic Care: Maintaining sterile techniques during the insertion and maintenance of indwelling lines.

Further Readings

1. https://www.canada.ca/en/health-canada/services/chemical-substances/fact-sheets/chemicals-glance/pseudomonas-putida.html
2. https://www.indogulfbioag.com/post/pseudomonas-putida-application
3. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/pseudomonas-putida
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC9726331/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6946569/
6. https://microbewiki.kenyon.edu/index.php/Pseudomonas_putida_alesha_%26_gwen
7. https://microbenotes.com/pseudomonas-putida/
8. https://www.sciencedirect.com/science/chapter/edited-volume/pii/B9780323905138000066
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC9772044/