Role of inter-species recombination of the ftsI gene in the dissemination of altered penicillin-binding-protein-3-mediated resistance in Haemophilus influenzae and Haemophilus haemolyticus

enzae (NTHi) and Haemophilus haemolyticus for the presence of mosaic ftsI gene structures, and to evaluate the role of inter-species recombination of the ftsI gene in the formation and distribution of resistant ftsI genes. Methods: The ftsI genes of 100 Haemophilus isolates comprising genetically defined b-lactamase-negative ampicillin-susceptible (gBLNAS), b-lactamase-positive ampicillin-resistant (gBLPAR), b-lactamase-negative ampicillin-resistant (gBLNAR) and b-lactamase-positive amoxicillin/clavulanate-resistant (gBLPACR) isolates of NTHi (n¼50) and H. haemolyticus (n ¼50) were analysed in this study. Both the flanking regions and the fulllength ftsI gene sequences of all study isolates were screened for mosaic structures using H. influenzae Rd and H. haemolyticus ATCC 33390 as reference parental sequences, and bioinformatics methods were used for recombination analysis using SimPlot. Results: Of the 100 clinical isolates analysed 34% (34/100) harboured mosaic ftsI gene structures containing distinct ftsI gene fragments similar to both reference parental sequences. The inter-species recombination events were exclusively encountered in the ftsI gene of gBLNAR/gBLPACR isolates of both NTHi and H. haemolyticus, and were always associated with the formation of a mosaic fragment at the 3 ′ end of the ftsI gene. There was no evidence supporting horizontal gene transfer (HGT) involving the entire ftsI gene among the clinical isolates in vivo. Conclusions: We provide evidence for the HGTand inter-species recombination of the ftsI gene among gBLNAR/ gBLPACRisolatesofNTHiandH.haemolyticusinaclinicalsetting, highlightingtheimportanceofrecombinationof the ftsI gene in the emergence of altered penicillin-binding protein 3 and BLNAR-mediated resistance.