Diversity of ampicillin resistance genes and antimicrobial susceptibility patterns in Haemophilus influenzae strains isolated in Korea.
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.
Kim
In-Suk
IS
Department of Laboratory Medicine, Gyeong-Sang University College of Medicine, Jinju, Korea.
Ki
Chang-Seok
CS
Kim
Sunjoo
S
Oh
Won Sup
WS
Peck
Kyong Ran
KR
Song
Jae-Hoon
JH
Lee
Kyungwon
K
Lee
Nam Yong
NY
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
D046915:Penicillin-Binding Proteins; D001618:beta-Lactamases