Antimicrobial susceptibility of Haemophilus influenzae isolates collected from 4 centers in Brazil (1990-2003).

Antimicrobial susceptibility was determined for 174 Haemophilus influenzae strains collected from patients with infection before and after vaccination against Hib (1990-1999 and 2000-2003, respectively) from 4 public health -laboratories in 3 Brazilian states. All strains were characterized for serotype and beta-lactamase production and in vitro activity of the following antimicrobial agents: -ampicillin, amoxicillin/clavulanate, ceftriaxone, rifampin, chloramphenicol, and trimethoprim/sulfamethoxazole (TMP-SMX). Minimum inhibitory concentrations were determined according to the guidelines of the National Committee for Clinical Laboratory Standards. Overall, ampicillin resistance was observed in 29 strains (17%), all beta-lactamase producers. All isolates were susceptible to amoxicillin/clavulanate and ceftriaxone. The prevalence of TMP-SMX-resistant isolates increased from 32.6% in the period 1990-1999 to 65.8% during the period 2000-2003. Among these isolates, 10.0% and 12.5% were resistant to ampicillin and chloramphenicol, respectively. Resistance to rifampin was detected in 8.2% and 9.7% of the strains, in 2 periods, respectively. Continued surveillance is necessary to monitor trends with the H. influenzae disease in Brazil.