Isolation, Identification and Resistance of Salmonella spp. in Eggs for Human Consumption

Aim: The present investigation aims to construct a comparative analysis based on isolation, identification and observation of resistance of Salmonella spp. in eggs for human consumption.

Study Design: This is an experimental study.

Place and Duration of Study: The present study was conducted in the Microbiology laboratory of Department Microbiology, St. Xavier’s College (Autonomous), Kolkata (West Bengal, India), from January to March, 2020.

Methodology: In this study, a total of 48 poultry (chicken) eggs from local and super markets (24 samples from each market) were examined to study the diversity of microorganisms in eggshell surface as well as in the internal contents with the specific objective to isolate Salmonella spp. and to study their resistance against a range of antibiotics- Cefotaxime (30 mcg), Levofloxacin (5 mcg), Aztreonam (30 mcg), Imipenem (10 mcg), Amikacin (30 mcg) and Ceftazidime (30 mcg).

Results: Microscopic and biochemical observations revealed the presence of Salmonella spp. in 68% egg samples. About 22% of the identified Salmonella spp. cultures were resistant to the antibiotics used in the study. Further, the total and the outer membrane proteins of specific isolated Salmonella spp. were isolated, few of which exhibit antibiotic resistance. More than 50% of the cultures exhibited biofilm formation which is a clear indication of the potential risk that it may pose after egg consumption. A 33 kDa and a 36 kDa protein was isolated from the resistant cultures and analysed by SDS-PAGE that could serve as promising vaccine development agents and the level of toxicity was checked on Human Cheek Cells (HCCs), of which 15% caused morphological distortions in the cells.

Conclusion: The study was conducted to isolate, identify and observe the antibiotic resistance pattern of Salmonella spp. from eggs obtained from local and supermarkets. The study clearly indicates the prevalence of antibiotic resistant Salmonella spp. contamination in eggs that may be detrimental for human consumption. Thus, appropriate measures should be adopted by vendors and poultry farm workers to ensure supply of egg samples suitable for human consumption. From the research and development point of view, the results hold a promising prospect to develop potential therapeutics and vaccine candidates against selected Salmonella spp. to reduce the incidence of food-borne infections in humans.