Abstract:
The study was designed to investigate the virulence patterns of Salmonella enterica serovar typhimurium that is associated with cheese. Two hundred and sixty (260) cheese samples were collected from vendors at Akure, Ikare and Owo in Ondo State using sterile sample bottles, stored in ice packed cooler and transported to the Department of Microbiology, Federal University of Technology, Akure. Isolation and characterization of Salmonella enterica and other bacteria from cheese samples were carried out by serial dilution and pour plate techniques on Nutrient agar (N.A) and Salmonella-Shigella (S.S) agar at 37 °C for 24h. The antibiotic sensitivity patterns of the bacterial isolates were carried out using Kirby Bauer disc diffusion method. The highest percentage frequency of bacterial occurrence was accounted for Ikare Akoko, with a total of 100% while the lowest frequency of occurrence was detected in samples bought from vendors in Owo town (51.3%). Fourteen (14) Salmonella enterica isolates were tested for multidrug resistant profiles using Clinical Laboratory Standard Institute (CLSI) specification. 56.3% of Salmonella enterica isolates were resistant to Augmentin (30μg); 31.3% were resistant to Amoxicillin (30μg), 21% were resistant to Gentamycin (10μg); 18.8% were resistant to Septrin (30μg) and ciprofloxacin (10μg) while 6.3% were resistant to Ofloxacin (Tarivid) (10μg), Chloramphenicol (30μg) and Sparfloxacin (10μg). Three (3) S. enterica isolates that were most resistant to the commonly used antibiotics were selected for plasmid analysis (profiling and curing) and their resistance were confirmed ‘plasmid-mediated’ after curing. Molecular characterization of Six (6) Salmonella enterica isolates for the possession of iro B, stn, hil A and spv gene were revealed through Multiplex polymerase chain reaction (PCR) analysis. Four (4) possess only iro B; two (2) possess only stn gene; and another three (3) possess hil A gene. None of the isolates possess spv C gene. This research has shown that antibiotic resistant Salmonella enterica serovar typhimurium is
present in locally made soft cheese samples. It also shows that virulence genes such as hil A, stn and iro B as well as plasmids mediating antibiotic resistance are present in S. enterica serovar typhimurium found in locally produced cheese. Therefore, locally produced soft cheese used for this study was found to be unsafe for human consumption.
