Antimicrobial resistance among invasive Haemophilus influenzae strains: results of a Brazilian study carried out from 1996 through 2000

Abstract

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%, with an overall prevalence of 18.4%. High frequency of ß-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 ß-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 MIC 90 were 0.015 µg/ml and 0.25 µg/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.

Nasopharyngeal colonization by Haemophilus influenzae in children attending day-care centers, in Ribeirão Preto, State of São Paulo, Brazil

“…In Brazil the combination of ampicillin and chloramphenicol is extensively applied because of its low cost and effectiveness (6); both antibiotics have been checked in two Brazilian studies on Hi antibiotic resistance, showing rates for ampicillin ranging from 10.0 to 13.8% (7,8), again agreeing with those presently reported.…”

“…Recently, in a few studies in DCC in which Hi biotypes were reported, one in Brazil (5), one in France (35) where the most common biotypes for Hi were type II (62.2%), V (18.0%) and I (16.2%), and one in the USA (14), where the most common types were type II (37.0%), III (21.0%), I (13.0%), V (12.0%) matched the results of the present study. The studies in Brazil showed to involve Hib diseases, particularly meningitis, and in these cases the more commonly isolated biotypes were of types I and II (7). After the introduction of Hib immunization in Brazil, type a has been proven to replace type b as causative agent of meningitis (36).…”

Prevalence and Genotypic Characteristics of ß-lactamase Negative-Ampicillin-Resistant (BLNAR) Haemophilus Influenzae in a Children's Hospital in Turkey

“…PCR results and se- quencing confirmed it to be a TEM-1 enzyme that reported as the most frequent β-lactamase found in ampicillin-resistant H. influenzae in the world. [13][14][15] In this study, ampicillin MICs were ≥0.5μg/mL in 36 isolates and IEF and PCR results showed that it was not due to a β-lactamase and later confirmed by sequencing that they were low BLNAR according to Ubukata classification. On the other hand, four ampicillin-resistant and β-lactamase positive isolates had reduced amoxicillin clavulanic acid susceptibility (0.5 to 1 μg/mL) isolates that TEM-1 positive and were low-BLNAR.…”