Characterization of multidrug-resistant Salmonella enterica serovars Indiana and Enteritidis from chickens in Eastern China.
A total of 310 Salmonella isolates were isolated from 6 broiler farms in Eastern China, serotyped according to the Kauffmann-White classification. All isolates were examined for susceptibility to 17 commonly used antimicrobial agents, 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 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 multidrug 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 multidrug-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.
College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Yan
Y
Lu
National Institute of Biological Sciences, Beijing, China.
Hongyu
H
Zhao
Department of Animal Husbandry and Veterinary Medicine, Beijing Vocational College Agriculture, Beijing, China.
Jian
J
Sun
College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Yuqi
Y
Liu
College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Xuping
X
Zhou
USDA, Agricultural Research Service, Southern Plains Agricultural Research Center, Food and Feed Safety Research Unit, College Station, Texas, United States of America.
Ross C
RC
Beier
College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Guojuan
G
Wu
College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Xiaolin
X
Hou
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002645:Chickens / Q000382:microbiology*; D002681:China; D024901:Drug Resistance, Multiple, Bacterial; D004751:Enteritis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D032023:Integrons / Q000235:genetics; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology*; D019779:Salmonella enterica / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology*; D017422:Sequence Analysis, DNA; D012703:Serotyping
D000900:Anti-Bacterial Agents