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. ß-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 ß-lactamase ranged from 6.6 to 57.7 percent, with an overall prevalence of 18.4 percent. High frequency of ß-lactamase-mediated ampicillin resistance was observed in Distrito Federal (25 percent), Säo Paulo (21.7 percent) and Paraná (18.5 percent). Of the 1712 strains analyzed, none was ß-lactamase negative, ampicillin resistant. A total of 16.8 percent of the strains were resistant to chloramphenicol, and 13.8 percent of these also presented resistance to ampicillin, and only 3.0 percent were resistant to chloramphenicol alone. All strains were susceptible to ceftriaxone and rifampin and the MIC90 were 0.015 æg/ml and 0.25 æg/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

Antimicrobial resistance patterns of Haemophilus influenzae isolated from patients with meningitis in São Paulo, Brazil

From 1989 to 1995, a total of 391 Haemophilus influenzae isolates were recovered from the cerebrospinal fluid (CSF) of hospitalized patients in São Paulo, Brazil. The majority of strains were isolated from infants aged less than 5 years. Strains belonging to biotype I (64.7 per cent), biotype II (34.5 per cent) and biotype IV (0.76 per cent) were detected. Ninety-nine percent of these strains were serotype b. Minimal inhibitory concentration (MIC) was determined for ampicillin, chloramphenicol and ceftriaxone. The ß-lactamase assay was performed for all strains. The rate of ß-lactamase producer strains ranged from 10 to 21.4 per cent during a period of 7 years, with an overall rate of 13.8 per cent. Of the 391 strains analyzed, none was ß-lactamase negative ampicillin resistant (BLNAR). A total of 9.7 per cent of strains showed resistance to both ampicillin and chloramphenicol; however, 4 per cent of them were resistant to ampicillin only and 2 per cent to chloramphenicol. All strains were susceptible to ceftriaxone and the MIC90 was 0.007 µg/ml, suggesting that ceftriaxone could be an option for the treatment of bacterial meningitis in pediatric patients who have not been screened for drug sensitivity.