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Asymptomatic carriage of Pneumocystis jiroveci in subjects undergoing bronchoscopy: a prospective study
N A Maskell1, D J Waine, A Lindley
1Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford Radcliffe NHS Trust, Oxford OX3 7LJ, UK.
Background:
The opportunistic fungus Pneumocystis jiroveci is a common cause of respiratory infection in immunocompromised patients. By contrast, pneumocystis pneumonia (PCP) occurs only rarely in immunocompetent individuals. Asymptomatic colonisation with P jiroveci has recently been described in patients who are either minimally immunosuppressed or who have underlying lung disorders such as bronchiectasis. We sought to determine the prevalence of asymptomatic colonisation by P jiroveci in a cohort of adult patients undergoing diagnostic bronchoscopy.
Methods:
A prospective observational cohort study was performed in patients who required bronchoscopy and bronchoalveolar lavage (BAL) as part of their routine clinical assessment. All the samples underwent standard microbiological analysis and a Grocott methenamine silver stain was performed where clinically indicated to detect the presence of P jiroveci. Polymerase chain reaction for detection of P jiroveci specific DNA was also performed.
Results:
Ninety three consecutive BAL fluid samples were analysed, 17 (18%) of which contained P jiroveci DNA. Of the potential predictors examined, only glucocorticoid use was significantly associated with detectable P jiroveci DNA. Eighteen patients were receiving oral glucocorticoids (equivalent to >20 mg/day prednisolone) at the time of bronchoscopy, of whom eight (44%) had detectable P jiroveci DNA. In contrast, P jiroveci was detected in only nine of 75 patients (12%) who were not receiving glucocorticoids (difference between proportions 32%, 95% CI 8 to 57; p=0.004, two tailed Fisher's exact test).
Conclusions:
P jiroveci colonisation, as determined by detection of P jiroveci DNA in BAL fluid, is common in HIV negative patients with primary respiratory disorders undergoing bronchoscopy and BAL. The higher prevalence in patients receiving corticosteroids suggests that oral glucocorticoid therapy is an independent risk factor for colonisation. In contrast, underlying lung cancer or COPD did not appear to be risk factors.
Insights
Asymptomatic Pneumocystis jiroveci colonisation is common in patients with respiratory disorders. Glucocorticoid use significantly increases the risk of this P. jiroveci colonisation.
Area of Science:
- Medical Microbiology
- Pulmonology
- Infectious Diseases
Background:
- Pneumocystis jiroveci causes pneumonia in immunocompromised individuals.
- Asymptomatic colonization by P. jiroveci is increasingly recognized in specific patient groups.
- The prevalence of asymptomatic P. jiroveci colonization in patients undergoing bronchoscopy is not well-defined.
Purpose of the Study:
- To determine the prevalence of asymptomatic Pneumocystis jiroveci colonization.
- To identify risk factors associated with P. jiroveci colonization in patients undergoing bronchoscopy.
Main Methods:
- Prospective observational cohort study.
- Bronchoalveolar lavage (BAL) fluid samples analyzed.
- Polymerase chain reaction (PCR) and silver stain used for P. jiroveci detection.
Main Results:
- P. jiroveci DNA detected in 18% of BAL samples.
- Glucocorticoid use was significantly associated with P. jiroveci detection (44% vs 12%).
- No association found between P. jiroveci and lung cancer or COPD.
Conclusions:
- Asymptomatic P. jiroveci colonization is prevalent in HIV-negative patients with respiratory disorders.
- Oral glucocorticoid therapy is an independent risk factor for P. jiroveci colonization.
- Further research may explore targeted screening or preventative strategies in high-risk patients.