Combination of altered PBPs and expression of cloned extended-spectrum β-lactamases confers cefotaxime resistance in Haemophilus influenzae

Resistance to beta-lactams in Haemophilus influenzae is mostly due to the presence of TEM beta-lactamases. beta-Lactamase-negative ampicillin resistance (BLNAR) also occurs as a result of PBP3 modifications. BLNAR strains are particularly common in Japan and France, and strains with combined mechanisms of altered PBP3 and beta-lactamase (BLPACR) are emerging. Although the prevalence of beta-lactamase-positive strains is high, TEM-derived extended-spectrum beta-lactamase (ESBL)-mediated cephalosporin resistance, which is common in Enterobacteriaceae, has not been reported in H. influenzae. In this study, the ability of ESBLs TEM-3, -4 and -5 to confer beta-lactam resistance in H. influenzae strains with or without modified PBP3 was tested.