Background and Aim: The genetic relationship among serotypes of Salmonella enterica from food animals, food of animal origin, and human is of interest as the data could provide an important clue for the source of human infection. This study aimed to determine the genetic relatedness of S. enterica from pig production and human in Thailand-Laos border provinces.

Materials and Methods: A total of 195 S. enterica serotypes isolated from pig and pork (n=178) and human (n=17) including four serotypes (Typhimurium, Rissen, Derby, and Stanley) were randomly selected to examine their genetic relatedness using highly conserved sequence of three genes (fim A, man B, and mdh).

Results: The results showed that 195 Salmonella isolates of four different serotypes were grouped into five different clusters, and members of the same Salmonella serotypes were found in the same cluster. Salmonella isolated from pig production and human in Thailand-Laos border provinces represented overlapping population and revealed a high degree of similarity, indicating close genetic relationship among the isolates.

Conclusion: The results support that the determination of Salmonella serotyping combined with analysis of phylogenetic tree can be used track the clonal evolution and genetic diversity of Salmonella serotypes in different host species.

Keywords: Laos, pig, Salmonella, Thailand.

1. Kaferstein, F.K., Motarjemi, Y. and Bettcher, D.W. (1997) Foodborne disease control: A transnational challenge. Emerg. Infect. Dis., 3(4): 503. [Crossref]

2. Paitoonpong, S. (2006) Thailand's cross-border trade in the Greater Mekong Subregion: Some issues never solved. TDRI Q. Rev., 21(1): 11-19.

3. KNIPS, V. (2004) Review of the Livestock Sector in the Mekong Countries (Livestock Information, Sector Analysis and Policy Branch Report), Rome, Food and Agriculture Organization of the United Nations. Available from: http://www.fao.org/WAICENT/FaoInfo/Agricult/againfo/resources/es/publications/sector_reports/lsr_mekong.pdf. [Last accessed on 19-09-2018].

4. Cocks, P., Abila, R., Bouchot, A., Benigno, C., Morzaria, S., Inthavong, P., Van Long, N., Bourgeois-Luthi, N., Scoizet, A. and Sieng, S. (2009) FAO ADB and OIE SEAFMD Study on Cross-Border Movement and Market Chains of Large Ruminants and Pigs in the Greater Mekong Sub Region. Funded by the Government of PR China and Australian Standz Initiative, Thailand, Bangkok. p1-63.

5. Li, K., Ye, S., Alali, W.Q., Wang, Y., Wang, X., Xia, X. and Yang, B. (2017) Antimicrobial susceptibility, virulence gene and pulsed-field gel electrophoresis profiles of Salmonella Enterica serovar Typhimurium recovered from retail raw chickens, China. Food Control, 72(A): 36-42. [Crossref]

6. CDC. (2004) Salmonella Surveillance Study. (2003) Centers for Disease Control and Prevention. US Department of Health and Human Services, Atlanta, Ga.

7. Selander, R.K., Beltran, P., Smith, N.H., Helmuth, R., Rubin, F.A., Kopecko, D.J. and Musser, J.M. (1990) Evolutionary genetic relationships of clones of Salmonella Serovars that cause human typhoid and other enteric fevers. Infect. Immun., 58(7): 2262-2275. [PubMed] [PMC]

8. Fisher, I.S. (1999) The Enter-net international surveillance network-how it works. Eur. Commun. Dis. Bull., 4(5): 52-55. [Crossref]

9. Swaminathan, B., Barrett, T.J., Hunter, S.B., Tauxe, R.V. and Force, C.P.T. (2001) The molecular subtyping network for foodborne bacterial disease surveillance, United States. Emerg. Infect. Dis., 7(3): 382-389. [Crossref]

10. Sukhnanand, S., Alcaine, S., Warnick, L.D., Su, W.L., Hof, J., Craver, M.P.J. and Wiedmann, M. (2005) DNA sequence-based subtyping and evolutionary analysis of selected Salmonella Enterica serotypes. J. Clin. Microbiol., 43(8): 3688-3698. [Crossref] [PubMed] [PMC]

11. Edgar, R.C. (2004) MUSCLE: Multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Res., 32(5): 1792-1797. [Crossref] [PubMed] [PMC]

12. Naruya, M.N. (1987) The neighbor-joining method: A new method for reconstructing phylogenetic trees. Mol. Biol. Evol., 4(4): 406-425.

13. Koichiro, T.M. and Nei, S.K. (2004) Prospects for inferring very large phylogenies by using the neighbor-joining method. Proc. Natl. Acad. Sci., 101(30): 11030-11035. [Crossref] [PubMed] [PMC]

14. Tamura, K., Stecher, G., Peterson, D., Filipski, A. and Kumar, S. (2013) MEGA6: Molecular evolutionary genetics analysis version 6.0. Mol. Biol. Evol., 30(12): 2725-2729. [Crossref] [PubMed] [PMC]

15. Palhares, J.C.P., Kich, J.D., Bessa, M.C., Biesus, L.L., Berno, L.G. and Triques, N.J. (2014) Salmonella and antimicrobial resistance in an animal-based agriculture river system. Sci. Total Environ., 472(15): 654-661. [Crossref] [PubMed]

16. Ranjbar, R., Ahmadi, M. and Memariani, M. (2016) Multiple-locus variable-number tandem repeat analysis (MLVA) for genotyping of Salmonella Enterica subspecies enterica serotype infantis isolated from human sources. Microb. Pathog., 100(1): 299-304. [Crossref] [PubMed]

17. Fricke, W.F., Mammel, M.K., McDermott, P.F., Tartera, C., White, D.G., LeClerc, J.E. and Cebula, T.A. (2011) Comparative genomics of 28 Salmonella Enterica isolates: Evidence for CRISPR-mediated adaptive sublineage evolution. J. Bacteriol., JB-00297. Available from: https://www.jb.asm.org/content/early/2011/05/20/JB.00297-11.short. Last accessed on 25-09-2018. [Crossref]

18. Tankouo-Sandjong, B., Sessitsch, A., Liebana, E., Kornschober, C., Allerberger, F., Hachler, H., Bodrossy, L. (2007) MLST-v, multilocus sequence typing based on virulence genes, for molecular typing of Salmonella Enterica subsp. enterica serovars. J. Microbiol. Method, 69(1): 23-36. [Crossref] [PubMed]

19. Foley, S.L., White, D.G., McDermott, P.F., Walker, R.D., Rhodes, B., Fedorka-Cray, P.J. and Zhao, S. (2006) Comparison of subtyping methods for differentiating Salmonella Enterica serovar Typhimurium isolates obtained from food animal sources. J. Clin. Microbiol., 44(10): 3569-3577. [Crossref] [PubMed] [PMC]

20. Wannaprasat, W., Padungtod, P. and Chuanchuen, R. (2011) Class 1 integrons and virulence genes in Salmonella Enterica isolates from pork and humans. Int. J. Antimicrob. Agents, 37(5): 457-461. [Crossref] [PubMed]

21. Ronnqvist, M., Valttila, V., Ranta, J. and Tuominen, P. (2018) Salmonella risk to consumers via pork is related to the Salmonella prevalence in pig feed. Food Microbiol.,71(1): 93-97. [Crossref] [PubMed]

22. Zaidi, M.B., McDermott, P.F., Fedorka-Cray, P., Leon, V., Canche, C., Hubert, S.K. and Tollefson, L. (2006) Nontyphoidal Salmonella from human clinical cases, asymptomatic children, and raw retail meats in Yucatan, Mexico. Clin. Infect. Dis., 42(1): 21-28. [Crossref] [PubMed]

23. Hauser, E., Tietze, E., Helmuth, R., Junker, E., Blank, K., Prager, R. and Malorny, B. (2010) Pork contaminated with Salmonella Enterica serovar 4,[5], 12: i: An emerging health risk for humans. Appl. Environ. Microbiol., 76(14): 4601-4610. [Crossref] [PubMed] [PMC]

24. Hauser, E., Hebner, F., Tietze, E., Helmuth, R., Junker, E., Prager, R. and Malorny, B. (2011) Diversity of Salmonella Enterica serovar Derby isolated from pig, pork and humans in Germany. Int. J. Food Microbiol., 151(2): 141-149. [Crossref] [PubMed]

25. Kerouanton, A., Rose, V., Weill, F.X., Granier, S.A. and Denis, M. (2013) Genetic diversity and antimicrobial resistance profiles of Salmonella Enterica serotype derby isolated from pigs, pork, and humans in France. Foodborne Pathog. Dis., 10(11): 977-984. [Crossref] [PubMed]

26. Campioni, F., Davis, M., Medeiros, M.I.C., Falcao, J.P. and Shah, D.H. (2013) MLVA typing reveals higher genetic homogeneity among S. Enteritidis strains isolated from food, humans and chickens in Brazil in comparison to the North American strains. Int. J. Food Microbiol., 162(2): 174-181. [Crossref] [PubMed]

---