Location: Food and Feed Safety ResearchTitle: Characterization of multidrug-resistant Salmonella enterica serovars Indiana and Enteritidis from chickens in Eastern China Author
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2014
Publication Date: 5/2/2014
Publication URL: http://handle.nal.usda.gov/10113/59499
Citation: Lu, Y., Zhao, H., Sun, J., Liu, Y., Zhou, X., Beier, R.C., Wu, G., Hou, X. 2014. Characterization of multidrug-resistant Salmonella enterica serovars Indiana and Enteritidis from chickens in Eastern China. PLoS One. 9:e96050. doi: 10.371/journal.pone.0096050. Interpretive Summary: Salmonella are a leading cause of microbial foodborne disease, and salmonellosis is also an important bacterial disease in chickens, leading to large numbers of chicken deaths and a significant loss to the poultry industry. The widespread use of antimicrobial agents in food-animal production has contributed to the decreased susceptibility of Salmonella to antibiotics. Three-hundred and ten Salmonella strains were isolated from chicken farms in Eastern China during 2009. Only two serotypes of Salmonella were detected out of the 310 strains isolated: Salmonella enterica serovar Indiana and Salmonella enterica serovar Enteritidis. Antimicrobial sensitivity test results showed that the isolates were generally resistant to sulfamethoxazole, ampicillin, tetracycline, doxycycline and trimethoprim, and that 95% of the isolates were sensitive to the antibiotics amikacin and polymyxin. We have identified the ability to acquire antibiotic resistance in a high percentage (66.5%) of the isolated Salmonella. The data presented here suggests the emergence of multi-drug resistant Salmonella enterica serovar Indiana. These drug resistant Salmonella strains isolated from broiler chicken farms in Eastern China were strongly resistant to antibiotics commonly used in clinical practice. This data may help guide the rational clinical use of antibiotics and help prevent and control the spread of drug-resistant bacteria.
Technical Abstract: A total of 310 Salmonella isolates were isolated from 6 broiler farms in Eastern China and serotyped according to the Kauffmann-White classification. All isolates were examined for susceptibility to 17 commonly used antimicrobial agents and representative isolates were examined for resistance genes and class I integrons using PCR technology. Clonality was determined by pulsed-field gel electrophoresis (PFGE). There were two serotypes detected in the 310 Salmonella strains, which included 133 Salmonella enterica serovar Indiana isolates and 177 Salmonella enterica serovar Enteritidis isolates. Antimicrobial sensitivity results showed that the isolates were generally resistant to sulfamethoxazole, ampicillin, tetracycline, doxycycline, and trimethoprim and 95% of the isolates were sensitive to amikacin and polymyxin. Among all Salmonella enterica serovar Indiana isolates, 108 (81.2%) possessed the blaTEM, floR, tetA, strA, and aac (6’)-Ib-cr resistance genes. The detected carriage rate of class 1 integrons was 66.5% (206/310), with 6 strains carrying gene integron cassette dfr17-aadA5. The increasing frequency of multi-drug resistance rate in Salmonella was associated with increasing prevalence of int1 genes (rs = 0.938, P = 0.00039). The int1, blaTEM, floR, tetA, strA, and aac (6’)-Ib-cr positive Salmonella enterica serovar Indiana isolates showed five major patterns as determined by PFGE. Most isolates exhibited the common PFGE patterns found from the chicken farms, suggesting that many multi-drug-resistant isolates of Salmonella enterica serovar Indiana prevailed in these sources. Some isolates with similar antimicrobial resistance patterns represented a variety of Salmonella enterica serovar Indiana genotypes and were derived from a different clone.