Molecular and Epidemiological Characterization of Carbapenem-Resistant Acinetobacter baumannii in Non-Tertiary Korean Hospitals

PURPOSE: The increasing prevalence and global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) has become a serious problem. The aim of this study was to investigate molecular and epidemiological characteristics of carbapenem-resistant A. baumannii isolates collected from Korean non-tertiary hospitals. MATERIALS AND METHODS: Thirty six non-duplicated carbapenem-resistant A. baumannii isolates were collected from 17 non-tertiary hospitals in Korea between 2004 and 2006. Isolates were typed by multilocus sequence typing and repetitive-sequence-based PCR (rep-PCR). Detection of genes encoding OXA carbapenemase and their relationship with ISAba1 was performed by PCR. RESULTS: Two clones were prevalent among 36 isolates: ST69 (17 isolates, 47.2%) and ST92 (19 isolates, 52.8%). Rep-PCR patterns were diverse and revealed that all isolates were clustered into eight band patterns. The ISAba1-activated blaOXA-23-like and ISAba1-activated blaOXA-51-like genes were prevalent among the carbapenem-resistant A. baumannii isolates. CONCLUSION: The class D beta-lactamase genes of A. baumannii were distributed nationwide in non-tertiary Korean hospitals.

Carbapenem Resistance Mechanisms and Molecular Epidemiology of Acinetobacter spp. from Four Hospitals in Seoul and Gyeonggi Province in 2006 / 대한임상미생물학회지

BACKGROUND: Increasing numbers of Acinetobacter spp. resistant to multiple drugs, including carbapenem, has been a serious problem. The aims of this study were to determine carbapenem resistance patterns and mechanisms, as well as to study the molecular epidemiology of Acinetobacter spp. METHODS: Clinical isolates of Acinetobacter spp. were collected from May to November in 2006. Antimicrobial susceptibility testing was performed using CLSI disk diffusion and agar dilution methods. Metallo-beta-lactamase- and OXA carbapenemase-producing isolates were detected by PCR. Carbapenem resistance and hydrolytic activities were compared according to OXA type and presence of ISAba1. Pulsed-field gel electrophoresis (PFGE) was performed to determine the epidemiologic features. RESULTS: The imipenem non-susceptible rates were variable from 10% to 67%. Among 151 isolates carrying bla(OXA-51-like), 75 isolates carried both bla(OXA-51-like) and ISAba1, and 25 isolates had both bla(OXA-51-like), bla(OXA-23-like), and ISAba1. Carbapenem MICs of both bla(OXA-51-like) and ISAba1-carrying isolates were higher than those with bla(OXA-51-like) only. Carbapenem MICs of bla(OXA-23-like)-carrying isolates were higher than those with both bla(OXA-51-like) and ISAba1. Both bla(OXA-51-like) and ISAba1-carrying isolates and blaOXA-51-like, blaOXA-23-like, and ISAba1-carrying isolates demonstrated higher hydrolysis activities in oxacillin and carbapenems. Most of the tested isolates were susceptible to tigecycline, and all of them were susceptible to colistin. Pulsed-field gel electrophoresis suggested that there had been several outbreaks of bla(OXA-23-like) and bla(OXA-51-like)-positive strains. CONCLUSION: Carbapenem non-susceptible Acinetobacter isolates and OXA carbapenemase-producing isolates were prevalent. Dissemination of bla(OXA)-harboring isolates may make it difficult to treat infections due to carbapenem-resistant Acinetobacter spp. Further surveillance studies are required to prevent the spread of carbapenem resistance.

Mechanisms of Acquiring Carbapenem-resistance in Acinetobacter Species / 대한임상미생물학회지

A rapid dissemination of carbapenem-resistant Acinetobacter spp. represents a significant clinical threat. Production of OXA carbapenemases and metallo-beta- lactamases (MBLs) is the most important mechanism in acquiring carbapenem resistance in Acinetobacter spp. Carbapenem resistance has also ascribed to non- enzymatic mechanisms, including changes in outer membrane proteins, alterations in the affinity or expression of penicillin-binding proteins, and overexpression of efflux pumps. The most important mechanism in A. baumannii isolates from Korea is the production of OXA-23, while that in other species of Acinetobacter is the production of metallo-beta-lactamases.

Multiplex PCR to detect multidrug-resistant Acinetobacter baumannii isolated from nosocomial infections / 临床检验杂志

Objective To develop a novel multiplex polymerase chain reaction (PCR) to detect multidrug-resistant Acinetobacter baumannii.Methods One hundred and five strains of multidrug-resistance A. baumannii were isolated from January 2006 to April 2007. The bacterial DNA was obtained by boiling the pure growth of A. baumannii. All isolates were subjected to the multiplex PCR to detect genes of blaOXA-23-like,blaOXA-24-like,blaOXA-51-like,blaOXA-58-like,intI 1 and intI 2.Results Among 105 isolates,76 were positive for blaOXA-51-like,blaOXA-23-like,and intI 1,18 were positive for blaOXA-51-like and intI 1,10 were positive for blaOXA-51-like and blaOXA-23-like,1 was positive for blaOXA-51-like and blaOXA-23-like,1 was positive for blaOXA-51-like,blaOXA-23-like,and blaOXA-58-like,and all were negative for blaOXA-24-like and intI 2.Conclusion The presence of OXA carbapenemase and integrase genes was correlated with multidrug resistance in A.baumannii.