Most clinicians recognize Pseudomonas stutzeri as an environmental, low-virulence organism that is only occasionally implicated in human disease. When infections occur, they are usually associated with immunocompromise, prosthetic material, previous surgery, or cardiovascular disease. Gastrointestinal infection due to P. stutzeri, however, has rarely been documented.
In this report, Moradi and colleagues describe a 61-year-old Iranian livestock farmer with ischemic heart disease, heart failure with reduced ejection fraction, pulmonary arterial hypertension, hypertension, and prior coronary angiography who presented with 7 days of bloody diarrhea accompanied by fever, chills, and vomiting. Laboratory evaluation demonstrated rising inflammatory markers, leukocytosis, and elevated erythrocyte sedimentation rate and C-reactive protein, supporting an infectious process.
Routine stool culture excluded common enteric bacterial pathogens including Salmonella, Shigella, and Vibrio cholerae. Instead, microbiologic investigation identified P. stutzeri, with confirmation by the BD Phoenix™ M50 automated identification system. The report also provides detailed microbiologic characterization, including colony morphology, biochemical testing, and culture findings that distinguish P. stutzeri from other non-fermenting Gram-negative organisms. These laboratory details provide valuable educational material for both clinicians and diagnostic microbiologists.
The patient was treated with intravenous ciprofloxacin and metronidazole followed by oral therapy, with complete clinical resolution after 7 days. Although the precise source of infection could not be established, the authors propose two plausible contributing factors: environmental exposure through livestock farming and an underlying susceptibility associated with cardiovascular disease and previous invasive cardiac procedures. Previous reports have linked P. stutzeri primarily to endocarditis, prosthetic valve infections, pneumonia, osteomyelitis, and other opportunistic infections rather than gastrointestinal disease.
This case reminds clinicians that uncommon organisms may occasionally be responsible for common clinical presentations. When routine diagnostic considerations fail to explain severe gastroenteritis—particularly in patients with significant comorbidities or unusual environmental exposures—careful microbiologic evaluation can identify unexpected pathogens and guide appropriate antimicrobial therapy.
Clinical Take-Home Message
- Pseudomonas stutzeri is an uncommon but clinically significant opportunistic pathogen capable of causing gastrointestinal infection.
- Cardiovascular disease and prior invasive cardiac procedures may represent predisposing risk factors in susceptible patients.
- Comprehensive stool culture and organism identification remain essential when evaluating severe or atypical infectious diarrhea.
- Recognition of rare pathogens allows targeted antimicrobial therapy and expands our understanding of the clinical spectrum of opportunistic infections.
Multiple-Choice Question
Question:
A 61-year-old man with ischemic heart disease, heart failure with reduced ejection fraction, and hypertension presents with 7 days of bloody diarrhea, fever, chills, and vomiting. Stool culture is negative for Salmonella, Shigella, and Vibrio cholerae, but automated microbiologic identification confirms Pseudomonas stutzeri. Based on this case report, which of the following statements is MOST accurate?
A. Pseudomonas stutzeri is a common cause of community-acquired bacterial gastroenteritis.
B. The diagnosis was confirmed by stool culture followed by automated identification using the BD Phoenix™ M50 system, and the patient improved with ciprofloxacin-based therapy.
C. The patient's blood cultures were positive for Pseudomonas stutzeri, confirming bacteremia as the source of infection.
D. The infection required emergent surgical intervention because antimicrobial therapy alone is ineffective.
Correct Answer:
B. The diagnosis was confirmed by stool culture followed by automated identification using the BD Phoenix™ M50 system, and the patient improved with ciprofloxacin-based therapy.
Explanation
Answer B is correct.
The patient's stool culture identified an unusual non-fermenting Gram-negative organism that was confirmed as Pseudomonas stutzeri using the BD Phoenix™ M50 automated identification system. He was successfully treated with intravenous ciprofloxacin and metronidazole followed by oral therapy, with complete clinical recovery after 7 days.
Why the other answers are incorrect:
- A. Incorrect. Although P. stutzeri is widely distributed in soil and water, it is a rare human pathogen and only exceptionally causes gastrointestinal infection. Most reported infections involve endocarditis, prosthetic devices, pneumonia, osteomyelitis, or other opportunistic infections rather than enteric disease.
- C. Incorrect. Blood cultures obtained during the patient's febrile illness remained negative throughout incubation. The diagnosis was established from stool culture rather than bloodstream infection.
- D. Incorrect. The patient responded well to medical management alone with antimicrobial therapy. No surgical intervention was required.
Key Learning Point
Although Pseudomonas stutzeri is generally regarded as a low-virulence environmental organism, it can occasionally cause clinically significant gastrointestinal infection. In patients with severe diarrhea, cardiovascular comorbidities, or unusual environmental exposures, comprehensive microbiologic evaluation may reveal uncommon pathogens and allow appropriate targeted antimicrobial treatment.
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