Genetic basis of multidrug resistance in Acinetobacter clinical isolates in Taiwan.
Multidrug-resistant (MDR) Acinetobacter spp. have emerged as a threat to public health. We investigated the various genes involved in resistance to fluoroquinolones, aminoglycosides, cephalosporins, and carbapenems in 75 clinical Acinetobacter isolates from a Taiwanese hospital. All isolates were tested for the gyrA mutations, the presence of integrons, bla(AmpC), and carbapenem resistance genes. The Ser83Leu mutation in GyrA accounted for fluoroquinolone resistance. The presence of integrons containing aminoglycoside-modifying enzymes was associated with resistance to gentamicin and tobramycin but not with resistance to amikacin. The presence of an ISAba1 element upstream of bla(AmpC) was correlated with cephalosporin resistance. Although most Acinetobacter baumannii isolates with ISAba1-bla(OXA-51-)(like) were resistant to carbapenems, several isolates remained susceptible to carbapenems. Transformation by the introduction of ISAba1-bla(OXA-23) or ISAba1-bla(OXA-66) into A. baumannii ATCC 15151 (CIP 70.10), resulting in the overexpression of OXA-23 or OXA-66, respectively, suggested the role of the ISAba1 element as a strong promoter. The two transformants showed significantly increased resistance to piperacillin-tazobactam, imipenem, and meropenem. The cefepime resistance conferred by ISAba1-bla(OXA-23) and the impact of ISAba1-bla(OXA-66) on carbapenem resistance in A. baumannii are reported here for the first time. Continuous surveillance of antibiotic resistance genes in MDR Acinetobacter spp. and elucidation of their antibiotic resistance mechanisms are crucial for the development of therapy regimens and for the prevention of further dissemination of these antibiotic resistance genes.
Lin
Yu-Chi
YC
Research and Diagnostic Center, Centers for Disease Control, Taipei, Taiwan.
Hsia
Ko-Chiang
KC
Chen
Yee-Chun
YC
Sheng
Wang-Huei
WH
Chang
Shan-Chwen
SC
Liao
Mei-Hui
MH
Li
Shu-Ying
SY
D000151:Acinetobacter Infections / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics*; D000617:Aminoglycosides / Q000494:pharmacology; D015780:Carbapenems / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D018432:Drug Resistance, Multiple / Q000235:genetics*; D024841:Fluoroquinolones / Q000494:pharmacology; D006801:Humans; D013624:Taiwan; D001618:beta-Lactamases / Q000235:genetics
D000617:Aminoglycosides; D015780:Carbapenems; D002511:Cephalosporins; D024841:Fluoroquinolones; D001618:beta-Lactamases; D027081:DNA Gyrase