Abstract
Salmonella can cause enteric diseases in humans and a wide range of animals, and even outbreaks of foodborne illness. The aim of this study was to investigate the frequency and distribution of serovars, and antimicrobial resistance in Salmonella isolates from pigs with diarrhea in 26 provinces in China from 2014 to 2016. A total of 104 Salmonella isolates were identified and the dominant serovar was S. 4,[5],12:i:- (53.9%). All Salmonella isolates were resistant to trimethoprim-sulfamethoxazole, and many were resistant to ampicillin (80.8%) and tetracycline (76.9%). Among 104 Salmonella isolates, aac(6′)-Ib-cr was the dominant plasmid-mediated quinolone resistance gene (80.8%), followed by qnrS (47.1%). The pulsed-field gel electrophoresis results suggest that the Salmonella isolates from different regions were genetically diverse, and ST34 was the most prevalent. S. 4,[5],12:i:- isolates is the widespread presence of heavy metal tolerance genes. The fact that the same sequence types were found in different regions and the high similarity coefficient of S. 4,[5],12:i:- isolates from different regions indicate the clonal expansion of the isolates, and the isolates carried various antimicrobial resistance genes. The multidrug resistant Salmonella can be widely detected in pigs, which will present a challenge for farm husbandry.
Highlights
Salmonella is Gram-negative pathogenic intestinal species of bacteria of the Enterobacteriaceae family
A total of 492 samples were obtained from 66 farms in 26 provinces. These samples were derived from the intestinal contents of pigs that died of diarrhea or from the feces of pigs with diarrhea
Between 2014 and 2016, a total of 104 Salmonella isolates were obtained from the intestinal contents of pigs that died of diarrhea or from the feces of pigs with diarrhea
Summary
Salmonella is Gram-negative pathogenic intestinal species of bacteria of the Enterobacteriaceae family. The World Health Organization (WHO) has estimated that Salmonella is responsible for 550 million infections among humans each year. In the USA population, approximately 1.2 million infections are caused by Salmonella and the economic loss owing to salmonellosis is estimated to be $3.5 billion annually [1]. Despite the lack of official surveillance data on Salmonella in China, it is estimated that it causes 75% of foodborne diseases [2]. More than 2500 serovars have been identified, and these serovars are classified based on slide agglutination with O and H antigen-specific sera. Some serovars are host specific, but others can infect a variety of hosts. Pigs are considered to be one of the major environmental reservoirs of Salmonella [3]
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