Study On Drug Resistance Genes Of OXA Type Extended-spectrum β-lactamases In Pseudomonas Aerugenosa

Objective The OXA-type extended-spectrumβ-lactamases(ESBLs) are originated from OXA-10,OXA-2 and OXA-1. They are divided into five groups, Group I and Group II are the major groups. Most of them are produced by Pseudomonas aerugenosa. We have studied the research in order to acquire the prevalence and genotype distribution of OXA-type ESBLs in Pseudomonas aerugenosa strains which were isolated from Xiangya Hospital of Central South University.Methods 97 non-repetitive clinical isolates of Pseudomonas aerugenosa strains were collected from Xiangya Hospital of Central South University from September 2006 to January 2007, they were prese -rved in -20℃refrigerator by defatting milk. All of clinical isolates were identificated and antibacterial susceptibility tested by Biomerieus automated microbiological-assay system VITEK-2,using GN identificati on cards and AST GN-13 cards, respectively. The genotypes of 97 Pseudomonas aerugenosa strains were screened about OXA group I and group II by PCR, then the gene of OXA enzyme in positive strains was amplified by specific primers and the PCR products were purificated and sequenced by automatic sequencer. The sequences acquired were compared with the known sequence in GenBank datebase in order to determine the gene subtype by BLAST searching. Results 3 of 97 Pseudomonas aerugenosa isolates carried blaOXA genes by PCR, the isolate rate of OXA-type extended-spectrumβ-lactamases was 3.1%(3/97). 3 clinical isolates (PA13, PA15, and PA17) were collected from urine, sputum and secretion respectively. Only OXA group I gene was detected in these isolates and no OXA group II type gene was detected by PCR. They were amplified by specific primers and the derivant of OXA-10. 2 of 3 isolates (PA15 and PA17) were found to be same homologous by sequencing analysis and gene sequence of another isolate P13 was different from them. The genotypes of 3 isolates were not included in GenBank datebase. The results suggested we have discovered two new subtypes of OXA enzymes which were named blaOXA-128 and blaOXA-129.The submit number were EU573214 and EU573215.Conclusions (1)It is the first discovery to two new OXA-type extended-spectrumβ-lactamases blaOXA-128 and blaOXA-129 in the worldwide. (2)This study is also the first report of the OXA-type ESBLs produced in Pseudomonas aerugenosa in Hunan Province, the isolate rate of OXA-type extended-spectrumβ-lactamases in Xiangya Hospital is low.