Pseudomonas fluorescens pneumonia
Hiroshi Ishii1, Hisako Kushima1, Yohei Koide1
1Department of Respiratory Medicine, Fukuoka University Chikushi Hospital, Chikushino, Fukuoka, Japan; Department of Infection Control and Prevention, Fukuoka University Chikushi Hospital, Chikushino, Fukuoka, Japan.
Abstract:
Pseudomonas fluorescens (P. fluorescens) is not generally considered a bacterial pathogen in humans; however, multiple culture-based and culture-independent studies have identified it in the indigenous microbiota of multiple body sites. We herein report a rare case of pneumonia caused by P. fluorescens. A man in his 80 s with chronic obstructive pulmonary disease and diabetes mellitus was diagnosed with stage II rectal cancer. He underwent laparoscopic surgery, and on the 6th postoperative day, he developed a high fever. Chest computed tomography revealed infiltration in the left lower lung. Gram staining of the sputum showed Gram-negative rods phagocytosed by neutrophils, suggesting postoperative nosocomial pneumonia. The patient was started on tazobactam/piperacillin, and his pneumonia quickly improved. Later, only P. fluorescens was detected in a sputum culture. It was susceptible to common antipseudomonal agents. Gram staining of P. fluorescens appears to show a slightly thicker and larger morphology in comparison to Pseudomonas aeruginosa. Although there have been reports of opportunistic infections caused by P. fluorescens in immunosuppressed patients, including those with advanced cancer, most have been bloodstream infections, with very few reports of pneumonia alone. Clinicians should be aware that patients, who are not necessarily immunosuppressed, may develop pneumonia caused by P. fluorescens.
Insights
Pseudomonas fluorescens, typically a harmless bacterium, rarely causes pneumonia. This case highlights its potential as a pathogen, even in non-immunosuppressed individuals, emphasizing the need for clinical awareness.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Pseudomonas fluorescens is commonly found in human microbiota but not typically pathogenic.
- Opportunistic infections by P. fluorescens are rare, mostly bloodstream infections in immunocompromised individuals.
Observation:
- An elderly male patient with comorbidities developed severe pneumonia post-surgery.
- Sputum analysis revealed Gram-negative rods, diagnosed as nosocomial pneumonia.
- P. fluorescens was the sole bacterium identified in sputum cultures.
Findings:
- P. fluorescens, usually non-pathogenic, caused pneumonia in a post-operative patient.
- The identified P. fluorescens strain was susceptible to standard antipseudomonal antibiotics.
- Morphological differences were noted between P. fluorescens and Pseudomonas aeruginosa in Gram stains.
Implications:
- P. fluorescens should be considered a potential cause of pneumonia, not exclusively in immunocompromised patients.
- Awareness of P. fluorescens pneumonia is crucial for clinicians, especially in post-operative settings.
- This case expands the spectrum of P. fluorescens-associated infections.
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