Isolation And Identification Of Tetracycline Resistant Bacteria And Distribution Of Resistance Genes From Pork In Abattoirs In Xiamen

Variety of antibiotics applied to human medical field are used in agriculture and animalhusbandry in recent years. Approximately90%of the world antibiotics are using as feed additiveseach year. Antibiotics are long-term overused as growth promoters, resulting in emergence anddiffusion of drug-resistant, and that threats of food safety and human health.Tetracyclines as a broad-spectrum antimicrobial agents,due to theirs high efficiency, lowtoxicity, low cost features, they are widely used in the treatment and preventing of animals andhumans clinical disease. At the same time, tetracyclines are commonly used antibiotics in theswine industry for disease treatment and growth promotion. Under the circumstances, the usageof antibiotics causes emergence of drug-resistant bacteria.Resistance plasmids transfer plays an important role in nature bacterial resistancephenomenon, which is the main reasons of resistance quickly changing in clinical. Resistantbacteria mediated by resistance plasmids were increasing dramatically worldwide and towardingthe development of multi-drug resistance mediated.Drug-resistant genes from food products of animal origin may directly or indirectlyspread to humans along the food chain. However, the understanding of the distribution ofresistance genes in the aninmal derived food is still limited. In this study, drug-resistance bacteriaisolated from slaughterhouse pork in Xiamen, P.R.China were identified via sequecing16S rRNAgene. Their susceptibility to9antimicrobial agents and distribution of tetracycline-resistant genesas well mechanisms of resistance to tetracycline, were studied. The main results are presented asfollows:A total of129strains from50pork samples sampled in slaughterhouse in Xiamen wereseparated on the basis of traditional culture and identified by sequencing their16S rRNA genesproducts. The129strains belonged to15different species. Among these strains,118wereGram-negative bacteria (91.5%),11were Gram-positive bacteria (8.5%), respectively. of thegenus Serratia, Aeromonas, Citrobacter, Escherichia, and Acinetobacter were commonly isolated,accounting for23.26%-10.85%. The ratio of the genus Myroides and Galactococcus were5.43% and6.20%, respectively. Be contrast, the numbers of stains belonged to Providencia, Raoul,Staphylococcus, Proteus, Klebsiella, Pseudomonas, Macrococcus caseolyticus, Lactobacilluswere few, no more than three.The drug resistance of strains were detected by using the method of K-B. The resultssuggested that116strains (89.92%) could tolerate three or more antibiotics. Among of these,33strains were found to be resistant to three,53strains resistant to four kinds of antibiotics.13strains resistant to four and five kinds of antibiotics.3strains resistant to seven kinds of antibioticand one strain resistant to eight kinds of antibiotics. These strains appeared different degrees ofresistance to nine kinds of antibiotics. The number of Strains resistant to penicillin andvancomycin were readily accounting for97.67%,89.92, relatively. Then resistance toerythromycin, tetracycline and sulfamethoxazole was relatively less, accounting for72.93%68.22%and27.91%, relatively. Separation rate of strains resistant to gentamicin,chloramphenicol, cefotaxime and ciprofloxacin was less than20%.In addition, the15kinds of genes resistant to tetracycline including seven efflux pump genes(tet A, tet C, tet E, tet G, tet K, tet L, tet A/P), seven ribosomal protection genes (tet M, tetO, tetQ,tetS, tet W, tet T, tet B/P) and one passivation enzyme gene (tet X) were detected, using PCRamplification techniques. The results showed that efflux pump genes were more than ribosomalprotection genes. More efflux pump genes existed in Gram-negative strains and more ribosomalprotection genes existed in gram-positive strains. Efflux pump mechanisms played a moreimportant role in tetracycline resistance.Finally, five Escherichia coli were subjected to plasmid curing via variable temperature-SDSmethod. By observing the change of the drug-resistant spectrum, PCR amplification of resistantgenes, comparing changes in the plasmid patterns, it was found that the tet drug-resistant genefrom one strain (Escherichia coli397) existed in the plasmid, which indicating the probabilitywithin these strains.