Isolation, molecular profiling and antibiotics resistance of bacterial pathogens from street-vended soymilk

Street-vended soymilk, derived from Glycine max, is widely consumed for its nutritional value and affordability. However, its high moisture content and nutrient richness make it susceptible to microbial contamination, especially when produced and sold under unhygienic conditions. This study aimed to isolate, molecularly profile, and determine the antibiotic resistance patterns of bacterial pathogens present in street-vended soymilk within a university community. Fresh soymilk samples were aseptically collected from multiple vendors and analyzed using standard microbiological methods. Isolates were characterized phenotypically through colony morphology, Gram staining, lactophenol cotton blue staining, and biochemical tests. Molecular identification was performed via DNA extraction, PCR, amplification of the 16S rRNA gene, agarose gel electrophoresis, and sequencing. Antibiotic Susceptibility Testing of the bacterial isolates were carried out using the Kirby-Bauer disk diffusion method on Mueller-Hinton agar. The zones of inhibition was measured using a meter rule and interpreted according to the guidelines of Clinical and Laboratory Standard Institute (CLSI). The results showed high bacterial counts across the assayed samples (≤4.8 × 10⁷CFU/mL). The bacterial isolates were identified as Salmonella typhi (98.4% sequence similarity) and Bacillus cereus (90.27% similarity). No fungal contamination was detected in any of the samples analyzed. Antibiotic susceptibility testing revealed that S. typhi SMIII was susceptible to ciprofloxacin, ceftriaxone, and chloramphenicol but resistant to amoxicillin, while B. cereus SMI was susceptible to gentamicin, vancomycin, and erythromycin but resistant to penicillin. Intermediate responses to tetracycline were observed in both isolates. These results highlight the presence of pathogenic and antibiotic-resistant bacteria in street-vended soymilk within the university community, posing potential public health risks. The findings underscore the importance of improved hygiene during processing and handling, routine microbial monitoring, and enforcing public health measures to minimize contamination to ensure consumer safety.