[The use of microbiological tools for the diagnosis of nosocomial pulmonary infections].

Objectives: To assess the use of microbiological examinations, notably serology, in the etiological diagnosis of pulmonary diseases in a department of infectious diseases.

Methods: A retrospective study assessing the habits of microbiological examination prescriptions in pulmonary infections was carried out from 1/05/2000 to 31/10/2001. All patients admitted during this period for pulmonary infection diagnosis and treatment in the infectious diseases and tropical Unit of Saint Antoine Hospital (Paris), were included. The relevance of use of the following diagnostic procedures was assessed: cytobacteriological examination of sputum, specimens obtained on bronchoscopy, hemoculture, serology and search for Legionella urinary antigens. Factors having influenced the co-prescription of these microbiologic examinations were analysed.

Results: The survey concerned 179 patients: 7 acute bronchitis, 25 acute exacerbations of chronic bronchitis and 147 community-acquired pneumonia. Microbiological diagnosis was obtained for 34 patients (17.4%), primarily on respiratory specimens. Serology was prescribed in 61 cases with a second serology in 23% (14/61). The principal factor predictive of bacterial serology prescription was the existence of interstitial opacity on chest radiography. Likewise, the search for Legionella urinary antigens was associated with the presence of interstitial opacity on the X-ray and of hyponatremia. However, it was only carried out in 37% of pneumonia with serious clinical presentation (25/67) and was followed by the prescription of combined antibiotics in 70% of the cases (40/57).

Conclusion: Assessment of the microbiology diagnostic methods of pulmonary infections showed the misuse of serology and insufficient prescription of the search for Legionella urinary antigens, recommended in the case of serious clinical signs.