Table 1.

Characteristics of the H. influenzae strains used in the experiments

				Resistance mechanismsc		MIC (mg/L) and susceptibility categoryf
Strain	Source	Serotypea	STb	β-Lactams	Quinolones	Ampicillin	Ampicillin/sulbactam	Ciprofloxacin
Hi-022	Sputum from patient with COPD	Non-typeable	ST836	TEM-1 β-lactamase Group III(+) high-rPBP3d	None	>16 (R)	8 (R)	≤0.06 (S)
Hi-072	Sputum from patient with COPD	Non-typeable	ST1	Group III(+) high-rPBP3d	Altered GyrA and ParCe	2 (R)	2 (R)	1 (R)

^aUsing hicap v.1.0.3 (https://github.com/scwatts/hicap).

^bBy MLST (https://pubmlst.org/organisms/haemophilus-influenzae).

^cTransferable genes were detected using ResFinder v.4.1 (https://cge.food.dtu.dk/services/ResFinder); alterations in chromosomal genes were detected by multiple sequence alignment of translated genes, with H. influenzae Rd KW20 (GCA_000027305) as reference.

^dCharacterized by the S385T, L389F and N526K substitutions in the transpeptidase region of PBP3.⁶

^eSubstitutions in the QRDRs of GyrA (S84L) and ParC (S84I) present.³¹

^fMICs were determined by broth microdilution according to recommendations from EUCAST (https://www.eucast.org/ast_of_bacteria), using custom MIC panels (Sensititre NONAG7, Thermo Fisher Scientific), and interpreted (S, susceptible; R, resistant) according to the most recent version of the EUCAST breakpoint table (version 13.0).