aAccording to Ubukata et al., Hasegawa et al., Garcia-Cobos et al., Hotomi et al. and this study. NA, not applicable.
bEssential amino acid substitutions in PBP3 (transpeptidase domain, 338–573) with the amino acid sequence of H. influenzae Rd KW20 [GenBank:U32793] as reference. SSN, Ser-Ser-Asn motif; KTG, Lys-Thr-Gly motif.
crPBP3, isolates with PBP3 sequences conferring resistance to beta-lactams (isolates assigned to groups I, II, III-like and III); sPBP3, isolates with PBP3 sequences conferring wild-type susceptibility to beta-lactams (remaining isolates).
dOriginally reserved for isolates with the additional substitutions M377I and L389F by Ubukata et al., modification proposed by Hotomi et al..
eOriginally categorized as group I by Ubukata et al., new group assignment proposed by Garcia-Cobos et al..