oa Distribution and factors associated with predominance of Salmonella enterica serovars in humans and animals using multi-locus sequence typing in Qatar

Background and Objectives-Salmonella enterica is one of the most commonly reported causes of bacterial foodborne illness around the world. Many factors, including food of animal sources, play a role in the predominance of certain serovars. The occurrence of S. enterica serovars varies between different geographical regions and data on their occurrence in Qatar is lacking. Knowledge on the occurrence of zoonotic serovars and associated factors will help to design cost-effective risk mitigation strategies. This risk of salmonellosis has been exacerbated by the ease of travel around the world, increase in world trade of food and animal items, and continued migration of people. Qatar is one of the countries where the factors that exacerbate the risk of foodborne diseases intersect. We carried out a combination of epidemiologic and molecular studies to investigate the distribution of S. enterica serovars in this highly diverse population, and to identify the factors that play a role in the predominance of a particular serovar. Methods-We carried out a repeat cross-sectional study in which human and non-human samples were collected and Salmonella spp. were detected using a combination of bacterial enrichment and real-time PCR. Salmonella isolates were analysed using the Multi-locus sequence typing (MLST) scheme and assigned accordingly by their eBURST groups (eBGs). We used the minimal spanning tree (MST) analysis to investigate the relationship among the isolates from different sources. Data on putative risk factors were collected and analysed for significance of association with particular serovars. Results-We identified 27 different sequence types (STs) and the most common were ST11 (29.5%) and ST19 (11.5%). Among the 27 STs, seven were novel (ST1695, ST1696, ST1697, ST1698, ST1699, ST1702, and ST1703). The STs related to serovar Enteritidis were ST-11, ST1695, and ST-1702; to Typhimurium were ST-15, ST-19, and ST-568; and to Newport were ST-31, ST-808, and ST-1698. Three of them were revealed to be common serovars in this study. In the MST analysis, three major clusters were presented in the overall population: Enteritidis, Newport and Typhimurium. Furthermore, it also revealed the possibility of transmission of strains between human and animal sources according to the lineages of STs. It was more likely to detect serovar Enteritidis in Qataris and serovar Typhimurium in non-Qataris in this study population. Conclusions—A diverse set of serovars were identified among the samples which could be due to the large scale of emigration and importation of animal feed and products in Qatar. Overall, our data also reveals the possibility of transmission of Salmonella isolates between human and animals; however, a detailed analysis of larger sample over a longer period of time using whole genome sequencing (WGS) could help to shed more light on the dynamics of transmission between these populations.