Departments: Interventional Pulmonology in Other Journals
Asymptomatic Carriage of Pneumocystis Jiroveci in Subjects Undergoing Bronchoscopy: A Prospective Study
Thorax. 2003;58:594–597. Maskell NA, Waine DJ, Lindley A, Pepperell JCT, Wakefield AE, Miller RF, Davies RJO. Oxford Centre for Respiratory Medicine, Churchill Hospital, Department of Paediatrics, Weatherall Institute of Molecular Medicine, Oxford Radcliffe NHS Trust, Oxford, and Windeyer Institute of Medical Sciences, Royal Free and University College Medical School, University College London, London.
This prospective observational cohort study of bronchoalveolar lavage (BAL) effluent samples from 93 consecutive patients who required bronchoscopy and BAL as part of their routine clinical assessment evaluated the prevalence of asymptomatic colonization by Pneumocystis jiroveci. None of the subjects was known to be HIV-positive, but HIV testing was not performed routinely as part of the study protocol. All samples underwent standard microbiologic analysis and a Grocott methenamine silver stain was performed when clinically indicated to detect the presence of P. jiroveci. Polymerase chain reaction for detection of P. jiroveci-specific DNA was also performed. Of the 60 men and 33 women (median age, 65 y; range, 20–87 y) who participated in the study, 23 (25%) had chronic obstructive pulmonary disease with a mean FEV1 2.0 and FVC 2.8. History of active tobacco smoking was present in 27% and 49% were exsmokers. Of the 93 consecutive BAL fluid samples, 17 (18%) 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 prednisolone per day) at the time of bronchoscopy, of whom 8 (44%) had detectable P. jiroveci DNA. In contrast, P. jiroveci was detected in only 9 of 75 patients (12%) who were not receiving glucocorticoids. There were no significant differences between those with and without detectable P. jiroveci in age, sex, or lung function (FEV1 and FVC). However, immunosuppression (resulting from glucocorticoids, cyclophosphamide, azathioprine, or hematologic malignancy) was significantly more likely in the subjects with detectable P. jiroveci in the BAL fluid. None of the 17 patients with detectable P. jiroveci developed Pneumocystis carinii pneumonia (PCP) during the 2-year follow-up period. The authors conclude that P. jiroveci colonization, 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. They further infer that higher prevalence in patients receiving corticosteroids suggests that oral glucocorticoid therapy is an independent risk factor for colonization by P. jiroveci. In contrast, underlying lung cancer or chronic obstructive pulmonary disease did not appear to be risk factors. The role of PCP as a major cause of illness and death in persons with impaired immune systems is well known. In recognition of its genetic and functional distinctness, the organism that causes human PCP is now named Pneumocystis jiroveci Frenkel 1999 (Emerg Infect Dis. 2002;8:891–896). Pneumocystis is a clinically well-recognized opportunistic fungus. It is also well known that PCP occurs in immunocompromised patients. Asymptomatic colonization by the Pneumocystis species is not well known. However, asymptomatic colonization by P. jiroveci has been reported in minimally immunosuppressed patients or in those with bronchiectasis. The transmission of Pneumocystis to humans is most likely by the airborne route. The newer techniques of identification of Pneumocystis have demonstrated that this fungus can exist as a saprophyte in asymptomatic subjects who are only mildly immunosuppressed by long-term glucocorticoid therapy for underlying malignancy, as well as in immunocompetent patients with chronic pulmonary diseases (Lancet. 1996;347:977; Am J Med. 1987;82:73–78). The study by Maskell and colleagues is a further corroboration of the earlier findings. They have also shown that in the subgroup of patients who were not receiving oral glucocorticoids or other immunosuppressants, P. jiroveci was present 12% of patients. More importantly, as noted by these authors, the high frequency of detection of P. jiroveci in BAL effluent from unselected patients undergoing routine bronchoscopy suggests that the incidence of colonization with P. jiroveci in hospital patients, and perhaps the general population, might be higher than previously thought. The authors also state that the significance of this colonization is unknown at present, although it could represent a biologic reservoir of infection that can be transmitted to hosts that are more susceptible.