Research On The Resistance Mechanisms Of Pandrug-resisitance Acinetobacter Baumannii In Xiamen

Objective:To study the infection distribution and drug resistance characteristics of acinetobacter baumannii in Xiamen area, so as to provide a basis for effective control infection and rational use of antimicrobial drugs. The molecular homology of Pandrug-resisitance acinetobacter baumannii (PDR-Ab) were investigated, which provides the strategies of controlling the prevalence of PDR-Ab in Xiamen area. By detecting resistance genes of PDR-Ab in P-lactamases, efflux pumps, quinolone, aminoglycoside modifying enzymes and 16S rRNA methylase. To analysis correlation of resistance gene and the drug resistantance, and explore PDR-Ab major resistance mechanisms in Xiamen area.Methods:1 From January 2012 to December 2013,326 clinical isolates of Acinetobacter baumannii were collected from three hospitals in Xiamen area. Bacterial identification was carried out by the VIKET COMPACT 2 automatic bacterial identification system. The minimal inhibitory concentrations (MIC) of the 16 kinds of commonly used antibiotics were detected by GN16 card. The antimicrobial susceptibility testing of cefoperazone/sulbactam, meropenem and polymyxin B were performed by broth dilution method.2 To analyze the molecular homology of 69 strains PDR-Ab by pulsed field gel electrophoresis (PFGE).3 The PDR-Ab resistance gene of extended-spectrum β-lactamases (ESBLs), metal β-lactamases (MBLs), Amp Cephalosporinases (AmpC), oxacillinases (OXA), efflux pumps, quinolone, aminoglycoside modifying enzymes and 16S rRNA methylase were amplified by polymerase chain reaction (PCR).Results:1 Clinical Distribution:Of the 326 strains of acinetobacter baumannii,121 strains were multiple drug resistant strains and 69 strains panresistant strains, the detection rates were 37.1% and 21.2%, respectively. Acinetobacter baumanii were isolated mainly from respiratory specimens, accuppied 70.2%, followed by secretions (14.4%) and blood (6.8%). Department distributed mainly in the intensive care unit (ICU), followed by respiratory medicine (21.2%) and neurosurgery (19.9%). Acinetobacter baumanii mainly infection the patients over the age of 50,especially 65-75 years old patients.2 Drug susceptibility testing:The resistance rates of acinetobacter baumanii to β-lactams, aminoglycosides, fluoroquinolones were very high. The resistance rates of multidrug-resistant and pan-resistant strains group were> 90%, some even up to 100%, the resistance rates of non-multi-drug resistant strains group roughly 50-80%; Carbapenems also showed high rates of resistance, such as imipenem and meropenem were as high as 85.8% and 77.4%, respectively. Cefoperazone/sulbactam showed a good antibacterial activity, resistance rate was 42.6%. Tigecycline and polymyxin B as the antibiotics of the two better antibacterial activity,resistance rates were 7.9% and 11.6%, respectively.3 Molecular homology analysis by PFGE:69 strains PDR-Ab can be divided into seven genotypes. There were the same clone strains spread in the same hospital. Zhongshan hospital with type A, the people’s liberation army 174th hospital with type B,the first hospital of Xiamen with type C.The same clone strains spreading among three hospitals was not found.4 Resistance gene test results:Of 69 strains PDR-Ab detected ESBLs:TEM gene positive 65 strains, the positive rate was 94.2%, PER gene 36 strains, the positive rate was 52.2%. AmpC:ADC gene 64 strains,the detection rate was 92.8%.OXA:OXA-23 gene 33 strains, the detection rate was 47.8%.adeABC efflux pump:adeB gene 69 strains, the detection rate was 100%; quinolones:gyrA gene 56 strains positive, the detection rate was 81.2%, parC gene positive 48 strains, the detection rate was 69.6%. Aminoglycoside modifying enzymes:aac(3)-Ⅰ gene 57 strains, aac(3)-Ⅱ1 strain, aac (6’)-Ⅰ b 46 strains, ant(3 ")-161 strains, Aph(3’)-Ⅰ48 strains, the detection rate were 82.6%、1.4%、66.7%、88.4%、69.6%, respectively.16S rRNA methylase:arm A gene 54 strains, the detection rate was 78.3%.Conclusions:1 The drug resistance of Acinetobacter baumannii in this area was very serious, there were the characteristics of multiple drug resistance and high resistance rates. The resistant rates of currently used antibiaotics were very high,such as β-lactams, aminoglycosides, quinolones and so on. The resistance rates of imipenem and meropenem were higher than the national average. Cefoperazone/sulbactam had a good antibacterial activity, tigecycline and polymyxin B showed the better antibacterial activity.2 The isolate rates of multidrug-resistant and pandrug-resistant were very high. It’s suggested that we should strengthen monitoring of drug resistance, for prevention of infection outbreak.3 PDR-Ab in Xiamen area mainly carried:TEM and PER gene of ESBLs, ADC gene of AmpC, OXA-23 gene of OXA, gyrA and parC gene of quinolones, adeB gene of efflux pump, aac(3)-Ⅰ, aac(3)-Ⅱ, aac (6’)-Ⅰ b, ant(3 ")-Ⅰ, Aph(3’)-Ⅰ genes of aminoglycoside modifying enzymes, armA gene of 16S rRNA methylase. Of which adeB gene positive rate was highest (100%), followed by TEM gene of ESBLs (94.2%) and ADC gene of AmpC (92.8%).4 The resistance mechanisms of PDR-Ab in Xiamen area are very complex. The resistant genes carried rates was high and wide coverage. Expression of adeABC efflux pump and production of β-lactamase are two main mechanisms of drug resistance in Xiamen area.