Antimicrobial Susceptibilities of 1,730 Haemophilus influenzae Respiratory Tract Isolates in Spain in 1998-1999

A β-lactamase prevalence of 23% was found among 1,730 Haemophilus influenzae isolates. Ampicillin susceptibility was 70%, and 12% of β-lactamase-negative strains presented diminished susceptibility to ampicillin (BLNAR phenotype). Susceptibility of 90% was found for cefaclor and clarithromycin, whereas it was nearly 100% for cefotaxime, cefixime, azithromycin, and cefuroxime. Ciprofloxacin-resistant (0.1%) and β-lactamase-positive amoxicillin/clavulanate-resistant (BLPACR) phenotypes (0.1%) are anecdotal so far.