Phenotypic Characterization of Virulence Factors in Multidrug-Resistant Salmonella typhi Serovars Isolated from Clinical Specimens in Bauchi Metropolis

Background: Typhoid fever is one of the most common infectious diseases in developing countries including Nigeria. Globally, typhoid fever is an important cause of morbidity and mortality in many regions of the world. People most at risk for serious complications due to Salmonella infections include older adults, pregnant women, infants, children, and people who have compromised immune systems.

Design and Duration: The study involves the collection of blood and stool specimens across all ages and gender between ages 0-70 years who present with fever and diarrhoea among other symptoms of typhoid in selected hospitals within Bauchi from January 2019 to August 2020.

Aim: The aim of this research is to phenotypically characterize virulence factors in Multidrug-Resistant Salmonella typhi serovars isolated from clinical specimens in selected hospitals within Bauchi.

Materials and Methods: A total of 518 blood and stool specimens were collected from selected health facilities within Bauchi metropolis to determine the presence of Salmonellae pathogens. Phenotypic identification of Salmonella typhi was performed using standard microbiological procedures, virulence factors were investigated and the Kirby Bauer Disk Diffusion method was used for the determination of the antimicrobial susceptibility and Multidrug Resistant pattern of the isolates.

Results and Discussion: Highest number of specimens collected was among patients with fever. Age groups 31-40 and 0-10 had the highest frequencies of occurrence respectively while age group 61-70 had the least. There was no significant difference between the age group and the number of isolates as p>0. 05. Highest frequency of S. typhi was found within the Female gender while Males recorded the lowest. The stool had the highest number of positive samples 31(21.6%) and blood had the least 17(4. 5%). Flagella was present in 18(37.5%) of 48 virulence isolates and was the most prevalent. Haemolysin was the least prevalent 4(8.3%) in all the isolates in our study. In the present study, 37(77.0%) of S. typhi isolates were resistant to 2 or more antimicrobial agents (Multidrug resistance). The highest resistance was observed in Oxacillin 46(95.8%). The isolates were sensitive to Ciprofloxacin 31(64.5%), Colistin Sulphate 29(60.4%), and Ceftriaxone 28(58.3%). All isolates 48(100%) were Multidrug-resistant and sensitive to Ciprofloxacin, Colistin Sulphate, Ceftriaxone, and Amikacin.

Conclusion: This study established that Salmonella typhi was more prevalent in the middle age group, female out-patient with most cases of fever, diarrhoea, and sometimes both. Most of the Salmonella typhi recovered from this study were more from stool than blood. Of all of the isolates in this study 48(9.2%) produced two or more virulent factors, with flagella as the commonest across all the MDR isolates; which is indicative of a significant relationship between virulence factors and multidrug resistance. The emergence of multidrug-resistant strains of Salmonella has added to the urgent need for the development of more effective control measures.