CHEST
Volume 150, Issue 2, August 2016, Pages 415-425
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Original Research: Chest Infections
Community-Acquired Pneumonia Due to Multidrug- and Non–Multidrug-Resistant Pseudomonas aeruginosa

https://doi.org/10.1016/j.chest.2016.03.042Get rights and content

Background

Pseudomonas aeruginosa is not a frequent pathogen in community-acquired pneumonia (CAP). However, in patients with severe CAP, P aeruginosa can be the etiology in 1.8% to 8.3% of patients, with a case-fatality rate of 50% to 100%. We describe the prevalence, clinical characteristics, outcomes, and risk factors associated with CAP resulting from multidrug-resistant (MDR) and non-MDR P aeruginosa.

Methods

Prospective observational study of 2,023 consecutive adult patients with CAP with definitive etiology.

Results

P aeruginosa was found in 77 (4%) of the 2,023 cases with microbial etiology. In 22 (32%) of the 68 cases of P aeruginosa with antibiogram data, the isolates were MDR. Inappropriate therapy was present in 49 (64%) cases of P aeruginosa CAP, including 17/22 (77%) cases of MDR P aeruginosa CAP. Male sex, chronic respiratory disease, C-reactive protein <12.35 mg/dL, and pneumonia severity index risk class IV to V were independently associated with P aeruginosa CAP. Prior antibiotic treatment was more frequent in MDR P aeruginosa CAP compared with non-MDR P aeruginosa (58% vs 29%, P = .029), and was the only risk factor associated with CAP resulting from MDR P aeruginosa. In the multivariate analysis, age ≥65 years, CAP resulting from P aeruginosa, chronic liver disease, neurologic disease, nursing home, criteria of ARDS, acute renal failure, ICU admission, and inappropriate empiric treatment were the factors associated with 30-day mortality.

Conclusions

P aeruginosa is an individual risk factor associated with mortality in CAP. The risk factors described can help clinicians to suspect P aeruginosa and MDR P aeruginosa.

Section snippets

Study Design and Patients

We performed an observational cohort study of consecutive patients admitted to Hospital Clinic, Barcelona, Spain, between January 1999 and December 2014 with a diagnosis of CAP. The exclusion criteria were: (1) patients without a positive microbiologic diagnosis, (2) severe immunosuppression (AIDS, chemotherapy, immunosuppressive drugs [e.g., oral corticosteroid ≥10 mg prednisone or equivalent per day for at least 2 weeks]), (3) health-care–associated pneumonia cases, (4) active tuberculosis,

Patient Characteristics

A total of 5,384 consecutive patients with CAP were enrolled during the study period. The final study population consisted of 2,023 patients with an established microbial etiology (Fig 1). There were 1,253 (62%) males and the mean (SD) age was 65 (19) years. CAP was the result of P aeruginosa in 77 of 2,023 cases (4%). Sixty-eight of the 77 (88%) cases had susceptibility data; 22 (32%) were MDR P aeruginosa and 46 (68%) were non-MDR P aeruginosa. We did not find XDR or pandrug-resistant strains

Discussion

The main findings of this study are the following: (1) The prevalence of CAP resulting from P aeruginosa in this large series of consecutive patients with CAP was 4% of patients with a defined etiology, and 32% of these patients had MDR P aeruginosa. (2) We identified several risk factors associated with CAP resulting from P aeruginosa in general and for CAP resulting from MRD P aeruginosa. (3) CAP resulting from P aeruginosa was associated with a significantly higher rate of inappropriate

Conclusions

In summary, we found that, although not common, P aeruginosa was a cause of CAP and one that is often treated inappropriately (64% of patients). Some 32% of cases are MDR, and these patients need to be identified because we found that 77% received inappropriate empiric therapy. Compared with other forms of CAP, patients with P aeruginosa had severe disease more commonly (62% vs 28%). In this series, as in others, inappropriate empiric antibiotic therapy was a mortality risk for all patients

Acknowledgments

Author contributions: A. T. is the guarantor of the entire manuscript and is responsible for the content of the manuscript, including the data collected and its analysis. C. C. is the main author of the paper; she reviewed the study data, edited the main body of the manuscript, contributed to supervising the collection of clinical, radiological, and microbiological data, and approved the final manuscript. M. S. N. contributed to the design of the project, analysis and interpretation of the

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    FUNDING/SUPPORT: The study was funded by Ciber de Enfermedades Respiratorias (CibeRes CB06/06/0028) and by 2009 Support to Research Groups of Catalonia 911.

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