Empirical testing of modified Salmonella MLST in aquatic environmental samples by in silico analysis

Subtyping Salmonella isolated from pet dogs with multilocus sequence typing (MLST) and clustered regularly interspaced short palindromic repeats (CRISPRs)

Salmonella, as a zoonotic pathogen, has attracted widespread attention worldwide, especially in the transmission between household pets and humans. Therefore, we investigated the epidemic distribution of dog Salmonella from pet hospitals and breeding base in Xuzhou, Jiangsu Province, China, and used multilocus sequence typing (MLST) and clustered regularly interspaced short palindromic repeats (CRISPRs) to subtype Salmonella isolates. From April 2018 to November 2019, a total of 469 samples were collected from pet hospitals and breeding base, including 339 dog samples and 60 cat samples. S. Kentucky (40.74%) was the most prevalent serotype, but other, such as S. Typhimurium (18.52%) and S. Indiana (18.52%), were also widespread. Eight different sequence type (ST) patterns were identified by MLST and ST198 was the highest proportion of these isolates. CRISPRs analysis showed that 9 different Kentucky CRISPR types (KCTs) was identified from ST198. 48 spacers including 29 (6 News) for CRISPR1 and 19 (4 News) for CRISPR2 that proved the polymorphic of Salmonella genes in samples from different sources. The analysis demonstrated that the common serotypes were widely present in pet hosts in the same area. This analysis shows that CRISPR genes have better recognition ability in the same serotype, which has a positive effect on the traceability of Salmonella and the prevention and treatment of salmonellosis.

The association of Salmonella enterica from aquatic environmental and clinical samples in Taiwan

Salmonella is one of the most common pathogens of waterborne and foodborne disease-causing pathogens. In this study, we collected 172 surface water samples from Puzih River and Kaoping River between the years 2010 and 2011. Salmonella was detected in 31.7% (32/101) and 42.2% (30/71) of the samples from the two rivers, respectively. From these positive samples, 44 Salmonella isolates were obtained from these positive samples and were characterized using serotyping and pulsed-field gel electrophoresis (PFGE) genotyping. The isolates were found with 17 serovars and 32 PFGE patterns. Salmonella enterica Newport, Bareilly, Kedougou, Albany and subspecies IIIb 50:k:z were the five most common serovars in aquatic environmental Salmonella isolates. In addition, of the total clinical samples from Chiayi and Kaohsiung, 33.7% (60/178) Newport serovars were isolated. After conducting categorical analysis, we found that the serovar Newport was not uniformly distributed cross the cities. The serovar Newport was over-represented (p<0.001) among human isolates in Chiayi and Kaohsiung. To investigate the association between Salmonella isolates from aquatic environment and human samples, we compared the environmental PFGE patterns of the test samples with those of 2438 clinical isolates, obtained from 51 hospitals across the country between 2010 and 2011. Of the 32 PFGE genotypes of environmental isolates, 8 genotypes were identical to those of clinical samples. Serovar Newport isolates with PFGE patterns SNX.119 and SNX.183 obtained from Puzih River samples were also identified in human samples at a local hospital. These suggest that there is a link between environmental and human clinical Salmonella. Identification of Salmonella serovars and genotypes present in surface water provides an indication of the specific S. enterica serovars and genotypes present in humans. This is the first study to investigate the Salmonella serovars and genotypes present in aquatic environment and humans in Taiwan.