Pseudomonas putida / fluorescens
Non-fermenting Gram-negative bacilli
Identification & Growth
Identification
- Oxidase-positive, fluorescein-positive, pyocyanin-negative
- Does not grow at 42 °C (differs from P. aeruginosa)
Growth Conditions
- MacConkey agar, lactose-negative; blood agar 30–35 °C, 24–48 h
Clinical Significance
- Contamination of solutions and catheters; bacteremia related to blood-product transfusion
Intrinsic Resistance
- Natural resistance to ampicillin, first- and second-generation cephalosporins and trimethoprim-sulfamethoxazole, similar to other environmental Pseudomonas spp.
Bench Alerts
- No dedicated BrCAST/EUCAST breakpoints: use PK/PD criteria and annotate the report
- Repeated isolates suggest an environmental source — investigate water and solutions
Clinical Notes
Clinical presentations
- Catheter-related bacteremia and bloodstream infection from contaminated blood components, mostly in hospitalized and immunocompromised patients.
- Low-virulence wound, urinary and respiratory infections, often of doubtful clinical significance.
- Pseudobacteremia and outbreaks linked to solutions, dialysis water and equipment, requiring epidemiological investigation.
Specimens and collection
- Paired blood cultures (peripheral and catheter) to separate true infection from collection contamination.
- Catheter tip by semiquantitative (Maki) technique when vascular-access infection is suspected.
- In suspected outbreaks, also sample solutions, water and point-of-use surfaces.
Epidemiology and at-risk populations
- Environmental and ubiquitous in water and soil; they grow well at low temperatures, favouring multiplication in refrigerated blood components.
- Highest risk in neutropenic, oncology and neonatal patients and in those with long-dwelling invasive devices.
- Repeated isolates from the same unit suggest a common environmental source and should trigger infection control.
Resistance and therapeutic implications
- Non-fermenters with variable intrinsic resistance to narrow-spectrum beta-lactams; therapy must follow the antibiogram, never species presumption.
- EUCAST/BrCAST publish no species-specific criteria for these organisms: apply Pseudomonas spp. criteria only where the current document allows, and flag the limitation in the report.
- Device removal is usually more decisive for resolution than the choice of antimicrobial.
Bench and reporting notes
- Oxidase-positive, do not ferment glucose on TSI/Rugai and produce fluorescent pigment (pyoverdine) under UV light on King B agar.
- They do not grow at 42 °C, unlike P. aeruginosa — a useful presumptive bench distinction.
- Species identification requires MALDI-TOF or sequencing; report as a complex when the method cannot discriminate.
Sources
- EUCAST — Clinical breakpoints (v16.1)
- EUCAST — Expert rules and expected resistant phenotypes
- UKHSA — Standards for Microbiology Investigations (SMI)
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Pseudomonas putida / fluorescens in the lab?
Pseudomonas putida / fluorescens is identified through oxidase-positive, fluorescein-positive, pyocyanin-negative, does not grow at 42 °c (differs from p. aeruginosa).
What are the intrinsic resistances of Pseudomonas putida / fluorescens?
This organism is naturally resistant to natural resistance to ampicillin, first- and second-generation cephalosporins and trimethoprim-sulfamethoxazole, similar to other environmental pseudomonas spp.. These drugs should not be reported as susceptible.
Where is Pseudomonas putida / fluorescens commonly found?
It is typically associated with contamination of solutions and catheters; bacteremia related to blood-product transfusion.
Want the free Bench Kit?
Sign up to receive the PDF kit: agars, Gram, Rugai, dilutions and the antibiogram checklist.