Molecular Characterization of Bacterial Pathogen Isolated from Raw Salad Vegetables

Abstract

Vegetables salad are considered as a high-risk food because they do not require any heating, washing or cleaning prior to consumption. The study was conducted to examine microbiological quality of raw salad vegetables and their role as a source of antibiotic resistant bacteria. Seven types of vegetables which are commonly used for salad i.e Cucumber, Carrot, Green Chilli, Peeper Mint, Lemon, Onion, Corriandar Leaves were collected from two Open markets and four different hotel/ restaurants of Dinajpur town. All the vegetables were contaminated with Klebsiella spp, E.coli spp, Salmonella spp, Shigella spp, Staphylococcus spp, Proteus spp, Vibrio spp, Pseudomonas spp, Streptococcus spp. The isolated bacteria were identified by studying staining characteristics, cultural properties on different selective media, biochemical tests, their antimicrobial resistance by Kirby-Bauer disc diffusion method and finally molecular characterization by PCR by 16S rRNA gene region was amplified with the universal primers, Forward primer 27F (5’- AGAGTTTGATCCTEGGCTCAG3) and Reverse primer 1492 R (5’- TACCTTGTTACGACTT3 ). From market samples, the bacterial loads were : Klebsiella spp. (10.90%), E.coli (12.73%), Salmonella spp (7.27%), Shigella spp (18.18%), Staphylococcus spp (1.82%) ,Proteus spp (16.36%), Vibrio spp (12.73%), Pseudomonas spp (18.18%), Streptococcus spp ( 1.82%). On the other hand, In hotel/ restaurant samples, the bacterial loads were : Klebsiella spp (6.38%), E.coli (29.79%), Salmonella spp ( 10.64%), Shigella spp (23.40%), Staphylococcus spp (6.38%), Proteus spp (2.13%), Vibrio spp (8.51%), Pseudomonas spp (8.51%) and Streptococcus spp (4.26%). Antibiotic sensitivity test showed that all bacterial isolates were resistant to Amoxicillin, Piperacillin, Bacitracin, Cloxacillin, Novobiocin, Methicillin, Cefixime and Vancomycin and sensitive to Nalidixic acid, Azithromycine, Chloramphenicol; Intermediate sensitive to Kanamycin, Tetracycline, and Norfloracin. Therefore, we saw that a great risk towards public health is posed by the organic fertilizers applied in the fields. Vegetables grown with untreated fertilizers may play a significant role in showering pathogens to the consumers. Hence, it is recommended that a more close supervision of such food type should be carried out by relevant authorities to avoid any future pathogen outbreaks. Thus the results suggest the necessity to follow the hygienic practices in salad preparation because salad might have an important role as a source of multiple antibiotic resistant bacteria.