Isolation and Molecular Identification of Different Salmonella SerovarsDistributed In Benue State, Nigeria

Isolation and molecular characterization of Salmonella serovars in Benue State was undertaken. Conventional cultural characterization and biochemical results showed that eighteen [18]positive samples of Salmonella species were obtained out of the four hundred and twenty [420] samples collected from Patients across the three [3] senatorial districts sampled. The organisms possessed characteristic pinkish colonies and black dots at the center on the XLD agar and whitish-green colonies on BGA. The API tests result showed the difference in the utilization of various substrates that distinguished between Salmonella species and other members of Enterobacteriaceae. Four [4] distinct serovars of S.enterica and one from S.bongori, totaling eight different groups of Salmonella were observed. S.enterica Typhimurium was the highest with 6 [33.33%] and prevalence of 1.43% followed by S.enterica Enteritidis with 4 [22.22%] and prevalence of 0.95%. Other serovars had <0.5% prevalence. S.entericaTyphi and S.enterica Heidelberg had 2 cases each while the remaining four [S.enterica Agona, S.enterica Paratyphi B, S.enterica Huaian and S.bongori] had a lone case each. Significant association was established between occurrence of Salmonella infection and causative serovars [χ2= 57.93, P<0.05]. Molecular characterization results obtained showed that the dendrogram formed 2 main clusters [numbered 36 and 81] with two divergent Salmonella strains. The first sub cluster of main cluster [numbered 57] has four strains isolated from different locations: S.entericaHeidelberg- MG663473.1 from Gboko; S.entericaTyphimurium- JQ228518.1 from Katsina-Ala; S.enterica Typhimurium- CP014981 from Makurdi and S.enterica Typhimurium- CP023166.1 from Kwande. Seventy five percent [75%] of strains in this group were Typhimurium serovars. In this group, S.entericaTyphimurium-CP023166.1 sourced from Kwande was a unique strain that showed wider genetic variability but closely related to the check strain [S.bongori strain KU060291.1]. The second sub cluster of a main [numbered 98] also consisted of 3 strains all of different serovars of S.enterica and one strain of another species. They are: S.entericaParatyphi B-JQ694526.1; S.enterica Heidelberg-CP019176.1; S.enterica Typhimurium- CP024619.1 and S.bongori-FR877557.1. The latter belongs to the same group with Paratyphi serovar and even closely related with Paratyphi B strain MF772492.1 used as a check. The second main cluster [numbered 81] comprised 8 strains belonging to 4 Enteritidis, 2 Typhi, 1 Huaian and 1 Typhimurium cutting across all locations except Gboko. Within this group, 4 strains showed wider relationships with other members and they were all of different serovars while Typhimurium strains were either closely clustered to themselves or to the Typhi strain. S.entericaTyphimurium- Mh496335.1 is divergent from the source of the main clusters [88] bearing no close relationship with any existing check strain. The most unique of all the 18 strains identified was the S.enterica serovar Agona strain 392869-2 and is closely related with a known check Enteritidis strain.