Abstract
The objective of this study was to explore the molecular epidemiology and the genetic support of clinical multidrug resistant (MDR) Acinetobacter baumannii (A. baumannii) isolates in an ICU ward of a comprehensive hospital. A total of 102 non-duplicate drug-resistant A. baumannii isolates were identified and 93 (91.1%) of them were MDR strains. Molecular analysis demonstrated that carbapenemase genes blaOXA-23 and blaOXA-51 were presented in all 93 MDR isolates (100%), but other carbapenemase genes, including blaOXA-24, blaOXA-58, blaIMP-1, blaIMP-4, blaSIM, and blaVIM genes were completely absent in all isolates. In addition, genes of AdeABC efflux system were detected in 88.2% (90/102) isolates. Interestingly, an addition to efflux pump inhibitor, reserpine could significantly enhance the susceptibility of MDR isolates to moxifloxacin, cefotaxime, and imipenem (p < 0.01). Clonal relationship analysis further grouped these clinical drug-resistant isolates into nine clusters, and the MDR strains were mainly in clusters A, B, C, and D, which include 16, 13, 25, and 15 isolates, respectively. This study demonstrated that clinical isolates carrying carbapenemase-encoding genes blaOXA-23 and AdeABC efflux pump genes are the main prevalent MDR A. baumannii, and the co-expression of oxacillinase and efflux pump proteins are thus considered to be the important reason for the prevalence of this organism in the ICU of this hospital.
Highlights
The emergence of multidrug-resistant (MDR) bacterial strains has been recognized as a main challenge for treatment of clinical infection with broad-spectrum antibiotics
Among the 102 drug-resistant isolates, 93 out of the 102 isolates were categorized as multidrug resistant (MDR) A. baumannii which were resistant to at least three classes of antimicrobials; nine of them were identified as drug-resistance to less than three classes of the tested antibiotics, which were designated as antibiotic unsusceptible isolates in this study (Table 2)
We investigated possible molecular epidemic mechanisms of MDR A. baumannii in the intensive care units (ICU) ward of the General Hospital of Ningxia Medical
Summary
The emergence of multidrug-resistant (MDR) bacterial strains has been recognized as a main challenge for treatment of clinical infection with broad-spectrum antibiotics. Acinetobacter baumannii (A. baumannii) is an emerging opportunistic nosocomial pathogen with great concern worldwide, which is the most common clinically isolated Acinetobacter species and a cause of severe infections in intensive care units (ICU) of hospitals, owing to its remarkable ability to acquire resistance to most antimicrobials [1,2]. MDR A. baumannii isolates have recently been increasingly reported in many countries, in Asia-Pacific countries including China [3,4,5,6,7,8,9,10,11,12]. An analysis of the molecular epidemiology of nosocomial infection MDR A. baumannii, in the ICU ward of a hospital may help to develop efficient guidelines to control the spread of these bugs [17]
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