A survey of antimicrobial drug resistance in respiratory tract pathogens, isolated in a northern Italian teaching hospital between 1990 and 1999.

Drug susceptibility test results of respiratory tract pathogens, isolated from patients admitted to the Clinic of Respiratory Diseases of the IRCCS San Matteo Hospital, University of Pavia (Italy) between 1990 and 1999, were retrospectively evaluated. A total of 1366 bacterial isolates were collected, including 499 gram-positive and 867 gram-negative strains. In comparison to methicillin-susceptible Staphylococcus aureus, the methicillin-resistant strains (MRSA) showed high levels of resistance to many selected antibiotics, except for glycopeptides. Resistance rates to beta-lactams were high in both Pseudomonas aeruginosa and in the other gram-negative isolates, while aminoglycoside and ciprofloxacin resistance was less than 20%. Some pathogens became more resistant to selected antimicrobials during the observation period, including staphylococci to methicillin, MRSA to ciprofloxacin, P. aeruginosa isolates to imipenem and ciprofloxacin, and the other gram-negative strains to almost all drugs considered, with the exception of cefotaxime and cotrimoxazole.