KNUST Research Week and Scientific Conference: Empowering Researchers to Achieve Impactful Outcomes

Fresh salad vegetables are widely consumed, and repeated microbial analysis on these vegetables over the years persistently indicates the presence of microbial contaminants in the salad vegetables that pose food safety risks to the consumer. Standard, culture-based detection methods are mostly used in the detection of bacteria. These culture-based methods are biased toward detecting fast-growing mesophilic bacteria and often miss viable but non-culturable (VBNC) or thermophilic species. Recommendations from previous studies suggest the use of modern technologies at the molecular level, such as the use of PCR and 16S rRNA, for the full detection of the microorganism. This study employed PCR and 16S rRNA gene sequencing tools to investigate bacterial diversity in 120 samples of cabbage, carrot, cucumber, green pepper, lettuce, and tomato from 20 farms across Ghana’s Eastern Region. Unlike conventional techniques, this approach enabled the detection of thermophilic bacteria such as Geobacillus stearothermophilus, Parageobacillus caldoxylosilyticus, and Bacillus thermoterrestris, organisms that require high incubation temperatures (>50°C) and are virtually undetectable using the conventional lab protocols. The method also identified VBNC and environmentally adapted species, including Bacillus stercoris, Mycobacterium mangenotii, and Clostridioides mangenotii, revealing a more complete picture of microbial contamination. Amplicon sizes ranged from 1280 to 1500 bp, with smaller fragments in some vegetables suggesting primer mismatch or low-complexity templates. Phylogenetic analysis confirmed the presence of known pathogens (Bacillus anthracis, Campylobacter jejuni), alongside beneficial or spoilage-associated strains. These findings highlight the unique strength of molecular diagnostics in detecting hard-to-culture bacterial threats and expand the understanding of microbial risks in farm-fresh salad vegetables. Incorporating such DNA-based tools into food safety monitoring is essential, especially in tropical agricultural systems where thermophilic and VBNC organisms may thrive unnoticed.