Bacterial Resistance And The Gene Type Of ESBLs-Producing Bacteria In Surgical Infection

Objective:To investigate the antibiotic resistance of clinical isolates and the gene type of extended spectrum β-lactamases(ESBLs) producing strains in surgical infection.Methods: Aerobic clinical isolates were collected from the surgical specimens in three teaching hospitals of jiangxi medical college; The clinical isolates was identified by the Vitek Am System and the antibiotic resistance of these clinical isolates was judged using the Kirby-Bauer agar diffusion method and the Vitek Am System. The data were sorted and analyzed by WHONET-5. The ESBLs-producing strains were confirmed by a disc dilution confirmatory test.In further test, the gene type of ESBLs was confirmed by PCR .Results 1, 631 strains were collected from September 2000 to September 2002, including 199 strains of Gram positive bacteria (31.54%) and 432 strains of Gram negative bacteria (68.46%). The first four isolates separated from the surgical specimens were Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae. Gram-negative bacteria remain dominant in surgery in Nanchang city .The antibiotic-resistance rate to most antibiotic was high. 2,The family Enterobacteriaceae is by far the most common species in which ESBLs have been recognized in three teaching hospitals in Nanchang city.The detectable rate of ESBLs-producing strains in Escherichia coli and Klebsiella pneumoniae was 38.89% and 31.94%, respectively.In Escherichia coli and Klebsiella pneumoniae,the resistance of ESBLs-producing group to Cefoxitin,ceftazidime,cefetaxime,aztreonam and ciprofloxacin was much higher than that of non-ESBLs-producing groups (p<0.05).The difference of resistance to other antibiotics between ESBLs-producing and non-ESBLs producing group show no statistical significent. The resistance rate of imipinem to ESBLs-producing strains was the lowest.3,From September 2001 to May 2002, 35 ESBLs-producing strains were isolated and confirmed.They were positive in β-lactamase test and their plasmids were obtained;The agarose gel electrophoresis of plasmidic DNA revealed that the positive strap appeared in all strains.By using TEM-1 type specific primers, the DNA fragment was amplified from plasmidic DNA in 26 strains, and using CTX-M-3 type specific primers,4 strains were positive and none strain was positive by using SHV-1-specific primers. 5 strains were negative by using all three specific primers respectively. The same methods were used in Chromosomal DNA, but negative results were obtained.Conclusions: ①.Gram-negative bacteria is the predominant bacteria in the three teaching hospitals of Jiangxi medical college. The situation of antibiotic-resistance is very serious.②.In Escherichia coli and Klebsiella pneumoniae,the resistant spectrum of ESBLs producing strains is beyond that of non-ESBLs producing strains. ③. The gene of ESBLs that exists in the plasmid can be transfered among the bacteria and enhance the antibiotic resistance of bacteria. Most of them are TEM type and CTX-M type is also detected.