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2016, Cilt 46, Sayı 4, Sayfa(lar) 181-187 |
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Investigation of the Presence of Class D Beta-lactamases in Clinical Isolates of Carbapenem-Resistant Acinetobacter baumannii |
Demet GÜR VURAL1, Belma DURUPINAR2 |
1Gebze Fatih Devlet Hastanesi, Kocaeli 2Ondokuz Mayıs Üniversitesi Tıp Fakültesi, Tıbbi Mikrobiyoloji Anabilim Dalı, Samsun |
Keywords: Acinetobacter baumannii, carbapenem, oxacillinases |
Objective: Acinetobacter baumannii is an aerobic, gram negative and
glucose non-fermenting opportunistic pathogen that is frequently associated
with outbreaks mostly in intensive care units. One of the main reasons for
the growing interest in A. baumannii in recent years is its tendency to
produce outbreaks and its ability to acquire and to accumulate resistance
determinants that lead to the emergence of multidrug resistant (MDR)
strains. The survival of this organism in hospital environment for long
periods, its genetic flexibility and high adaptability has resulted in rapid and
global spread of MDR A. baumannii strains resistant to many antimicrobial
classes, including carbapenems, especially in the last few years.
Carbapenems are important agents of the beta-lactam group that are used
in the treatment of Acinetobacter baumannii infections. Carbapenem
resistance in Acinetobacter species has been increasingly reported
throughout the world and has become the indicator of emerging antimicrobial
resistance. Carbapenem resistant A. baumannii is considered as an
important health problem today because of limited number of treatment
options. The most common mechanisms of carbapenem resistance in
Acinetobacter species involves OXA-type enzymes. A. baumannii can
produce four different families of enzymes including OXA-23, OXA-24,
OXA-51 and OXA-58 and derivatives of all these 4 enzymes that can
hydrolyze carbapenems. In this study, we aimed to investigate OXA-type
Class D beta-lactamases on carbapenem-resistant- A. baumannii strains
isolated from various clinics of our hospital.
Material and Methods: One hundred clinical isolates of carbapenemresistant A. baumannii isolated from various clinical specimens were included in the study. Isolates were identified and their antibiotic susceptibility tests were performed by VITEK 2 system (bioMérieux, USA). Minimal Inhibitory Concentration (MIC) values for imipenem and meropenem were determined by broth microdilution method according to the recommendations of CLSI (Clinical and Laboratory Standards Institute). The presence of OXA carbapenemases namely blaOXA-23, blaOXA-24, blaOXA-51, blaOXA-58 gene regions in isolates was investigated by PCR. Results: All isolates were found to be resistant to piperacillin, cefepime and ceftazidime according to the antimicrobial susceptibility test results. All A. baumannii clinical isolates in the study appeared to be susceptible to colistin. All isolates were found to be resistant to imipenem and meropenem with broth microdilution method. A. baumannii specific blaOXA-51 was found to be positive in all isolates. While blaOXA-23 was found to be positive in 93% of the isolates, blaOXA-24 and blaOXA-58 gene regions weren't detected in isolates. Conclusion: The high level of resistance to beta lactam antibiotics and the high prevalence of OXA type carbapenemases are remarkable. As a result of the study,it was concluded that carbapenem resistance may occur as a result of the overproduction of OXA-51 type natural oxacillinases and the presence of OXA-23 gene. Additionally, further studies are needed to investigate other resistance mechanisms. |
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