Effects Of AmpC Gene Distribution And Producing AmpC Enzyme In Pseudomonas Aeruginosa On Drug Susceptibility

The status of drug resistance caused by unreasonable application of antibiotics was becoming severer.It was a worldwide problem in controling the serious infections.One of the methods to deal with this problem was that the treatment should be based on the status of drug resistance caused by infectious agents. Detection of drug resistance was still based on traditional susceptibility test.The most disadvantage was that the times of diagnose for treatment was so long that doctors could not make the correct choices at the beginning of infections.Drug resistant gene could be detected by Polymerase chain reaction(PCR) directly.It was an efficient teclmology to determine the drug resistance of pathogen quickly and sensitively, which should provide evidences to choose the reasonable antibiotics.β-lactam antibiotics were used to treat infections caused by Pseudomonas aeruginosa,which were the familiar pathogenic bacterium in intensive care unit(ICU) now.β-lactamase was mostly produced by gram-negative clinical isolates,responding to resistance toβ-lactam antibiotics.It bad a great variety,including AmpC enzyme,ESBLs and so on.AmpC enzyme was belonging to groupⅠof Bush and group C of Ambler and was encoded by ampC gene.It han been showed that the sequences of ampC gene were remarkable different in different genera of strains.ObjectiveTo investigate effects of ampC gene distribution and producing AmpC enzyme in Pseudomonas aeruginosa isolated from respiratory ICU on drug susceptibility.On this basis,the methods by double detection of ampC gene and AmpC enzyme guides the application of antibiotics in the treatment of Charrin disease.Methods1.The 147 Pseudomonas aeruginosa strains were collected from ICU of respiratory department of Jinling hospital from february in 2004 to february in 2006.2.ampC gene was amplified by polymerase chain reaction(PCR) in 147 Pseudomonas aeruginosa strains.3.AmpC enzyme was examined by Cefoxitin in three dimensional test in 147 Pseudomonas aeruginosa strains..4.Disk diffusion method was used for detecting the susceptibility of antimicrobial agents against 147 Pseudomonas aeruginosa strains.5.The relationship between ampC gene distribution or producing AmpC enzyme in Pseudomonas aeruginosa and drug susceptibility were investigated by statistics software SPSS 10.0.Results1.107 out of 147 strains were found to be positive by PCR for ampC gene, positive rate of ampC gene was 72.8%.The PCR product showed completely coincident with the GenBank ampC sequence(AE 004827).2.The susceptibility rates of ampC gene negative strains to Imipenam, Ceftazidime,Cefepime,Cefoperazone/sulbactam were 95.0%,92.5%,90.0%,90.0%, respectively;while susceptibility rates of ampC gene positive strains were 95.3%,75.7%,74.8%,73.0%,respectively.The analytic results showed the susceptibility rates of ampC gene positive strains were significantly lower to Ceftazidime,Cefepime, Cefoperazone/sulbactam(P＜0.05). 3.88 out of 147 strains were found to be positive by PCR for producing AmpC enzyme,positive rate of producing AmpC enzyme was 59.9%.3 strains negative by PCR for ampC gene producd AmpC enzyme,which is probably associated with plasmid transmitted manner.4.The susceptibility rates of no-producing AmpC enzyme strains to Imipenam, Cefoperazone/sulbactam,Ceftazidime,Cefepime,were 100%,94.9%,93.2%,91.5%, respectively;while susceptibility rates of producing AmpC enzyme to Imipenam, Cefepime,Ceftazidime,Cefoperazone/sulbactam,were 92.0%,81.8%,71.6%,62.5%, respectively.The analytic results showed the susceptibility rates of producing AmpC enzyme strains were significantly lower to Imipenam,Cefoperazone/sulbactam, Ceftazidime,Cefotaxime,Aztreonam,Cefuroxime(P＜0.05).5.The methods by double detection of ampC gene and AmpC enzyme guides the choices of antibiotics in the treatment of Charrin disease.Before the use of antibiotics,ampC gene in the genome DNA of Pseudomonas aeruginosa were tested by polymerase chain reaction(PCR),if positive,we avoid to apply Amikacin, Ciprofloxacin,Cefuroxime,Amoxicillin/clavulanic acid alone;In the period of therapy,bacterial culture and detection of AmpC enzyme are undertook,then the modulation of the antimicrobial agents is determined by the results of ampC gene distribution and drug resistance.Conclusions These experiments confirmed that the status of drug resistance in strains with ampC gene or producing AmpC enzyme was more severer than those without ampC gene or producing AmpC enzyme.To clear out ampC gene distribution and producing AmpC enzyme in Pseudomonas aeruginosa is helpful to select the antimicrobial agents in the treatment of clinical infection.