title: Diversity of ampicillin resistance genes and antimicrobial susceptibility patterns in Haemophilus influenzae strains isolated in Korea.
abstract: By Etest determination of the susceptibilities of 229 Haemophilus influenzae strains isolated in Korea to 10 antibiotics, the isolates were found to be antibiotic nonsusceptible in the following order: ampicillin (58.1%), trimethoprim-sulfamethoxazole (52%), cefaclor (41.1%), clarithromycin (25.8%), chloramphenicol (14.0%), amoxicillin-clavulanic acid (13.5%), meropenem (11.7%), cefixime (10.9%), cefuroxime (9.2%), and levofloxacin (1.3%). The prevalences of each resistance class were 23.6% for beta-lactamase-negative ampicillin-susceptible (BLNAS) strains; 37.6% for strains with the TEM-1 type beta-lactamase gene; 1.3% for strains with the ROB-1 type beta-lactamase gene; 29.3% for the beta-lactamase-negative ampicillin-resistant (BLNAR) strains with a mutation in the ftsI gene, which encodes PBP 3; and 8.3% for beta-lactamase-positive amoxicillin-clavulanate-resistant (BLPACR) strains, which showed both resistance mechanisms (i.e., a beta-lactamase gene and a mutation in the ftsI gene). The MIC50s of all beta-lactams, including cephem and meropenem agents, for the BLNAR strains were two to three times higher than those for the BLNAS strains. This study confirms that the prevalence of BLNAR and BLPACR strains is relatively high and for the first time confirms the presence of H. influenzae strains carrying blaROB-1 in Korea. Even though mutations in another gene(s) might be involved in beta-lactam resistance, these results suggest that mutations in the ftsI gene are important for the development of resistance to beta-lactams in H. influenzae strains in Korea.
authors.affiliation: Department of Laboratory Medicine, Gyeong-Sang University College of Medicine, Jinju, Korea.
authors.forename: In-Suk
authors.initials: IS
authors.lastname: Kim
authors.forename: Chang-Seok
authors.initials: CS
authors.lastname: Ki
authors.forename: Sunjoo
authors.initials: S
authors.lastname: Kim
authors.forename: Won Sup
authors.initials: WS
authors.lastname: Oh
authors.forename: Kyong Ran
authors.initials: KR
authors.lastname: Peck
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Song
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: Nam Yong
authors.initials: NY
authors.lastname: Lee
mesh_terms: D000668:Ampicillin Resistance / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006192:Haemophilus Infections / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D007723:Korea; D008826:Microbial Sensitivity Tests; D009154:Mutation; D046915:Penicillin-Binding Proteins / Q000235:genetics; D013045:Species Specificity; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D046915:Penicillin-Binding Proteins; D001618:beta-Lactamases