Antimicrobial resistance among invasive Haemophilus influenzae strains: results of a Brazilian study carried out from 1996 through 2000.
A total of 1712 strains of Haemophilus influenzae isolated from patients with invasive diseases were obtained from ten Brazilian states from 1996 to 2000. beta-Lactamase production was assessed and the minimum inhibitory concentrations (MIC) of ampicillin, chloramphenicol, ceftriaxone and rifampin were determined using a method for broth microdilution of Haemophilus test medium. The prevalence of strains producing beta-lactamase ranged from 6.6 to 57.7%, with an overall prevalence of 18.4%. High frequency of beta-lactamase-mediated ampicillin resistance was observed in Distrito Federal (25%), São Paulo (21.7%) and Paraná (18.5%). Of the 1712 strains analyzed, none was beta-lactamase negative, ampicillin resistant. A total of 16.8% of the strains were resistant to chloramphenicol, and 13.8% of these also presented resistance to ampicillin, and only 3.0% were resistant to chloramphenicol alone. All strains were susceptible to ceftriaxone and rifampin and the MIC90 were 0.015 micro g/ml and 0.25 micro g/ml, respectively. Ceftriaxone is the drug of choice for empirical treatment of bacterial meningitis in pediatric patients who have not been screened for drug susceptibility. The emergence of drug resistance is a serious challenge for the management of invasive H. influenzae disease, which emphasizes the fundamental role of laboratory-based surveillance for antimicrobial resistance.
Casagrande
S T
ST
Departamento de Bacteriologia, Instituto Adolfo Lutz, São Paulo, SP, Brasil.
Landgraf
I M
IM
Kobata
A M M
AM
Zanella
R C
RC
Bokermann
S
S
D000668:Ampicillin Resistance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001938:Brazil; D002443:Ceftriaxone / Q000494:pharmacology; D002648:Child; D002702:Chloramphenicol Resistance; D024881:Drug Resistance, Bacterial; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000201:enzymology / Q000302:isolation & purification; D006801:Humans; D008583:Meningitis, Haemophilus / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D012293:Rifampin / Q000494:pharmacology; D001618:beta-Lactamases / Q000096:biosynthesis*
D000900:Anti-Bacterial Agents; D002443:Ceftriaxone; D001618:beta-Lactamases; D012293:Rifampin