Genotypic versus Phenotypic Characterization, with Respect to β-Lactam Susceptibility, of Haemophilus influenzae Isolates Exhibiting Decreased Susceptibility to β-Lactam Resistance Markers

Abstract

Among 165 Spanish Haemophilus influenzae isolates with mutations in the ftsI gene (ftsI+) (2005 to 2007), 73% were β-lactamase negative and 26.7% were positive. The proportion of β-lactamase-negative isolates to β-lactamase-positive isolates was 2:1 to 4:1 in general, versus 1:3 in pediatric hospitals. Among 44 β-lactamase-positive strains, 8 strains produced ROB-1 (5 from the pediatric hospital). β-Lactamase-positive ftsI+ strains were phylogenetically closer than were β-lactamase-negative strains.