Occurrence of Salmonella serovars implicated in Salmonellosis in North-western part of Nigeria

Abstract

Accurate diagnosis of clinical Salmonella enterica and differentiation into its serovars is important from a public health and epidemiological point of view. Standard cultural, biochemical and polymerase chain reaction techniques were employed to isolate and identify Salmonella enteric serovars implicated in salmonellosis. This study was carried out between June 2015 and May 2016 in some selected hospitals in North-Western Nigeria. Four hundred and twenty stool samples were collected from patients clinically diagnosed of pyrexia and/or gastroenteritis. Of the 420 samples collected, 27 were positive for Salmonella, given rise to an overall prevalence rate of 6.4%. One hundred and fifty two samples were collected from ≤1-5yrs age-group and 19 (12.5%) were positive for Salmonella species. Out of the 199 male patients recruited for this study, 16 (8.0%) had Salmonella infection while 11 (5.0%) of221female patients recruited had Salmonella infection. Sex of the patients has no significant association with the infection (p>0.05). Out of the 27 Salmonella isolated, six different serovars were encountered. S. typhi and S. enteritidis were the most frequently encountered; given rise to 25.9% prevalence rate each. The second most frequently encountered was S. typhimurium with 18.5% prevalence rate. The least encountered serovar was S. paratyphi B which had 3.7% prevalence rate. Out of the 27 Salmonella isolates, 17 (63%) were isolated from patients presenting with mix symptoms and S.Typhi was the most frequently encountered, given rise to 35.3%. Seven isolates (25.9%) of the 27 Salmonella were isolated from patients presenting with diarrheoa only and S. enteritidis (57.1%) was the most frequently encountered. However, frequency of occurrences of serovars has no significant association to the salmonellosis symptoms (p>0.05).The prevalence rate in elderly patients (≥60yrs) was also high, for out of the 18 samples collected from them, 5 (27.8%) were positive. The age-group with least prevalence rate was 16-40yrs; all samples collected from them were negative for Salmonella infection. Salmonella infection was significantly associated with the age groups with p<0.05.Out of the 16 cases of salmonellosis in male patients, 7 (43.8%) were typhoidal, while 9 (56.3%) were non- typhoidal. Among female patients, 11 salmonellosis cases were recorded, 5 (45.5%) were typhoidal and 6 (54.5%) were non-typhoidal. This result showed that there was reduced in Salmonella infection in part of North Western Nigeria. However, there is need to sustain good sanitary practices in order to curtail increase and reduced children’s exposure to the infection.

Keywords

• PCR
• Salmonella Serovars
• Salmonellosis
• Prevalence