[Prevalence of Haemophilus influenzae resistant to ampicillin, cefaclor, cefotaxime, chloramphenicol and cotrimoxazol isolated from laboratories in the city of São Paulo, Brazil].
OBJECTIVE
To determine Haemophilus influenzae resistant to ampicillin and other antibiotics isolated from different clinical specimens.


METHODS
Isolates of H. influenzae were identified by culture with V and X factors and the aminolevulinic test. Nitrocefin was used to detect beta-lactamase (betaLac) production isolates were tested for antimicrobial susceptibility by disc diffusion and agar dilution methods. Serotype b was assessed by slide co-agglutination.


RESULTS
From 245 H. influenzae identified, 155 were tested for serotype b, 28% (43/155) of which were positive. The global rate of beta-lactamase-positive isolates was 9% (22/245). Resistance was similar among serotype b (11.6%) and non-type b H. influenzae (9.8%) (p>0.05). No difference on betaLac production was found according to specimen's origin or the patients' age. Resistances to other antibiotics (by agar dilution and disc diffusion method, respectively) were: chloramphenicol 3.3 to 7.1%; cefaclor: 1.6 to 3.9% and cotrimoxazol: 9.1 to 10.5%. No resistance to cefotaxime has been detected; 63% (5/8) beta-Lac-positive isolates by agar dilution showed also resistance to chloramphenicol, compared to 3% (4/118) in the ss-Lac-negative group (p<0.001).


CONCLUSIONS
H. influenzae ampicillin-resistance has shown to be lower than other hospital-based-studies in São Paulo, and comparable to rates found in healthy carriers. The association between ampicillin and chloramphenicol resistance was significant: where this pattern is frequently found, the initial therapy for severe H. influenzae infections - like meningitis - should include a third generation cephalosporin.
Rey
L C
LC
Universidade Federal de São Paulo/EPM. reyfonte@fortalnet.com.br
Farhat
C K
CK