| Salmonella’is one of the most important food-borne pathogens. It leads very serious food safety problems every year, causing widespread concern worldwide. Moreover, widely abused antibiotics usage leads to drug resistance in Salmonella. As time goes on, the resistance has been enhanced and resistance spectrum has been enlarged, that increased the difficulty of treatment in Salmonella infection. Therefore, the drug resistance of Salmonella received widespread attention. In recent years, in addition to genetic mutations, bacteria resistant to propagation by horizontal transfer of genes has also become an important way. For example, one of the important mobile genetic elements, plasmid, which is independent outside the chromosome and independent of DNA replication, played an essential role in the spread of resistance genes. Therefore, to analyze the antibiotic resistance, and to detect the resistance genes in Salmonella isolates of different sources, could reveal the relationship between the resistance genes and the antibiotic resistant strains, that has a very important significance. The main contents of this paper and the results are as follows: 1. Screening of resistant in Salmonella isolates from foodborne and clinical. The antibiotic resistance were tested in226isolates from both food and clinical sources using VITEK2Compact, according to the2012Clinical and Laboratory Standards Institute (CLSI) standard to calculate the antibiotic resistance rate (R), the intermediaries rate (I), and sensitive rate (S). Moreover, the plasmid resistance genes were detected in those non-sensitive isolates. To penicillins, the ampicillin-resistance rate was15.9%(36/226), and the ampicillin/sulbactam-resistance rate was12.8%(29/226); To aminoglycosides, the tobramycin-resistance rate was6.2%(14/226),and the gentamicin-resistance rate was5.8%(13/226); To quinolones, the ciprofloxacin-resistance rate was4.0%(9/226), and the levofloxacin-resistance rate was1.8%(4/226); To cephalosporins, the cefazolin-resistance rate was4.4%(10/226), the ceftazidime-and ceftriaxone-resistance rate was2.2%(5/226), respectively, and the cefotetan-resistance rate was0.9%(2/226). To carbapenems, and to those β-lactams except penicillins and cephalosporins, all the isolates were sensitive.2. Non-sensitive isolates detected from VITEK test were rescreened on resistance by K-B disk diffusion method. Using K-B method to test all the drug-resistant strains, the quasi-coincidence rate (CA) of Imipenem, Amikacin, Ceftazidime reached100%; Ceftazidime was at the rate of98.3%; Levofloxacin was96.6%; Ceftriaxone was94.9%; Aztreonam was93.2%, Ampicillin, Tobramycin, Ciprofloxacin were91.5%;Trimethoprim/Sulfamethoxazole was86.4%; and Gentamicin was84.7%.3. Non-sensitive isolates detected from VITEK test were screened for the distribution of resistance genes. Among all the non-antibiotics-sensitive isolates, the carrying rate of P-lactam resistance genes was59.5%(50/84), in which the CMY gene was10.7%(9/84), the OXA gene was27.3%(23/84), the TEM gene was39.2%(33/84), and the PSE gene was1.2%(1/84). Among the non-quinolones-sensitive isolates, the carrying rate of qnr genes was14.7%(5/34), in which the qnrA gene was11.8%(4/34), and the qnrS gene was2.9%(1/34). Among the non-quinolones-aminoglycosides sensitive isolates, the carrying rate of ace (6’)-Ib-cr gene was17.1%(7/41). Only the distribution of CMY gene in foodborne versus clinical isolates was significantly different (x2=5.480, P<0.05).4. Non-sensitive isolates detected from VITEK test were screened for the distribution of virulence plasmid. The carrying rate of spv in non-sensitive isolates was6.0%(5/84). All of these5Salmonella isolates carrying spv genes were from clinical sources, so the derived carrying rate was14.7%(5/34); there was no significant difference between foodborne versus clinical isolates on the carrying rate of virulence plasmid (x2=2.05, P>0.05).In this study, the antibiotic resistance of foodborne and clinical Salmonella isolates was analyzed, as well as the resistance genes, which could reveal the relationship between the resistance genes and the antibiotic resistant strains, providing the basis for food safety risk assessment, and providing a reference data for the clinical treatment of choice of medication as well. |
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