Characterization of virulence factors of Salmonella isolated from human stools and street food in urban areas of Burkina Faso

Solange Kakou-ngazoa,Marguerite E. M. Nikiema,Nicolas Barro,Absatou Ky/Ba,Kobo Gnada,Ameyo Yayra Audrey Addablah,Lassana Sangaré,Emmanuel Sampo,Evariste Bako,Aboubacar Sylla,Jean Bienvenue Ouoba,Oumarou Zongo,Isidore Juste Ouindgueta Bonkoungou,Adama Sanou,Kuan Abdoulaye Traoré,Rasmata Ouédraogo

doi:10.1186/s12866-021-02398-6

Abstract

BackgroundThis study was undertaken to identify and functionally characterize virulence genes from Salmonella isolates in street food and stool cultures. From February 2017 to May 2018, clinical and food Salmonella strains were isolated in three regions in Burkina Faso. Salmonella was serotyped according to the White-Kauffmann-Le Minor method, and polymerase chain reaction (PCR) was used to detec invA, spvR, spvC, fimA and stn virulence genes commonly associated with salmonellosis in Sub-Saharan Africa.ResultsA total of 106 Salmonella isolates (77 human stools; 14 sandwiches) was analyzed using a serological identification with an O-group test reagent. The presence of Salmonella was confirmed in 86% (91/106) of the samples were reactive (OMA-positive/OMB-positive). Salmonella serogroup O:4,5 was the most common serogroup detected (40%; 36/91). Salmonella Enteritidis and Typhimurium represented 5.5% (5/91) and 3.3% (3/91), respectively and were identified only from clinical isolates. Furthermore, 14 serotypes of Salmonella (12/91 human strains and 2/15 sandwich strains) were evocative of Kentucky/Bargny serotype. For the genetic profile, 66% (70/106) of the Salmonella had invA and stn genes; 77.4% (82/106) had the fimA gene. The spvR gene was found in 36.8% (39/106) of the isolates while 48.1% (51/106) had the spvC gene. Among the identified Salmonella Enteritidis and Salmonella Typhimurium isolated from stools, the virulence genes detected were invA (3/5) versus (2/3), fimA (4/5) versus (3/3), stn (3/5) versus (2/3), spvR (4/5) versus (2/3) and spvC (3/5) versus (2/3), respectively.ConclusionThis study reports the prevalence of Salmonella serotypes and virulence genes in clinical isolates and in street foods. It shows that food could be a significant source of Salmonella transmission to humans. Our results could help decision-making by the Burkina Faso health authority in the fight against street food-related diseases, in particular by training restaurateurs in food hygiene.

Highlights

This study was undertaken to identify and functionally characterize virulence genes from Salmonella isolates in street food and stool cultures
Salmonella strains isolated from food and clinical samples Fifteen (15) Salmonella was isolated from sandwich samples and 91 from clinical samples
Serotyping of Salmonella strains All 106 Salmonella isolates were agglutinated with antisera Antiserum O mixture of group A (OMA) and Antiserum O mixture of group B (OMB)

Summary

Introduction

This study was undertaken to identify and functionally characterize virulence genes from Salmonella isolates in street food and stool cultures. In 2019, pathogens responsible for foodborne diseases, including Salmonella enterica (non-typhoid), caused 230,000 deaths in Africa [7]. In resource-limited countries, in Sub-saharan Africa, NTS is endemic, with high rates in children under 3 years of age and immunocompromised individuals [8, 9]. These diseases have a significant negative economic impact in resource-limited countries amounting to $ 110 billion per year [10]

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