Study On PER-1 Type Extended-Spectrum β-Lactamases Produced By Gram-Negative Bacilli

Study on PER-1 type Extended-Spectrum β-Lactamases Produced by Gram-Negative Bacilli Background β-lactam antibiotics are the most important antimicrobial agents. Resistance toβ-lactam antibiotics is most frequently related to the production of β-lactamases ,especially in Gram-Negative bacilli .In the past 30 years, due to lots of 3th Cephalosporins were used for therapying infection resulted from multiresistant bacteria ,more and more Gram-Negative bacilli produced Extended-Spectrumβ-lactamases (ESBLs).So far, more than 100 types of ESBLs has been detected . Escherichia coli and Klebsiella pneumoniae were main ESBLs-producing isolates. But many other genus of Enterobacteriaceae and non-fermenters also can produce ESBLs. ESBLs-producing isolates become multi-resistant to antibiotics. PER-1 type ESBLs is non-TEM or non-SHV type ,first was detected in Pseudomonas aeruginosa isolated in France ,1993.PER-1 type ESBLs was mainly detected in Pseudomonas aeruginosa in Europe .Subsequently, it was detected in Salmonella typhimurium Acinetobacter baumannii Proteus mirabilis and Klebsiella pneumoniae.Recently, PER-1 type ESBLs was detected in Korea and China .But less research were proceed on PER-1 type ESBLs produced by Enterobacteriaceae. Study on PER-1 type ESBLs produced by Enterobacteriaceae is necessary Objective To investigate the prevalence of ESBLs in Escherichia coli Klebsiella pneumonia and Enterobact cloacae and their antimicrobial-resistance profile; To detect PER-1 type ESBLs in above isolates and investigate the antimicrobial pattern of PER-1 type ESBLs-producing isolates Methods 167 strains of Escherichia coli,154 strains of Klebsiella pneumoniae and 67 strains of Enterobacter cloacae were tested .All of them were isolated from all kinds of clinical specimens in four hospitals of Nanchang city from August,2002 to June ,2003. Antimicrobial Susceptibility Tests(AST)were determined by K-B disk diffusion test. Cefotaxime(CTX)andCeftaxidime(CAZ)were used for screening ESBLs-producing isolates.Double-disk test(CTXandCTX/CA or CAZ andCAZ/CA)and three-dimension extract test were used to determine ESBLs. PER-1 gene was amplified by PCR .The products of PCR were sequenced to identify itsβ-lactamase encoding gene. The genotype of blaPER-1–positive Escherichia coli and Enterobacter cloacae were performed by Enterobacter Repetitive Intergenic Consecus(ERIC)primer PCR Rusults The positive rates of ESBLs in Escherichia coli,Klebsiella pneumoniae and Enterobact cloacae were 30%,34%and 36%, respectively .The antimicrobial-resistant rates of ESBLs-producing isolates to Ampicillin, Azithromycin and Clindamycin were high to 100%, to Amikacin ,Ciprofloxacin and Nitrofurantoin were relatively low ,to Imipenem was 0%except 2 isolates of Klebsiella pneumoniae. 16 isolates were PER-1 gene positive .The PER-1 gene positive rates of Escherichia coli , Klebsiella pneumoniae and Enterobact cloacae were 3.6%(6/167),3.2%(5/156)and 9.0%(5/67) 2 isolates produced PER-1 type ESBLs and AmpC (Klebsiella pneumonia037 Enterobact cloacae017 )The antimicrobial-resistant rates of isolates harboring blaPER-1 to Cefotaxime,Ceftaxidime,Amikacin,Cefoxitin,Cefepime and Imipenem were 100%,100%,56%,94%,31%and 0% ,respectively.6 strains of Escherichia coli and 5 strains of Enterobact cloacae harboring blaPER-1 were devided to 5 kinds of genotypes ,respectively.DNA bands of 2 strains of E.coli were identical Conclusion The positive rate of ESBLs in Gram-Negative Bacilli is very high in Nanchang area .Antimicrobial-resistance of ESBLs-producing isolates is serious. blaPER-1 is detected in Escherichia coli,Klebsiella pneumoniae and Enterobact cloacae and blaPER-1 is first reported in Enterobact cloacae. blaPER-1 has diffused in Enterobacteriaceae. Imipenem and Amikacin may be used to therapy the infection caused by bacteria harboring blaPER-1. Modified three-dimension extract test can detect isolates producing ESBLs and AmpC. ERIC-PCR is suitable for investigating the dissemination of multi-resistance isol...