Microbiological analysis of ready-to-eat salads available at different outlets in Lahore, Pakistan

Food-borne diseases are the global public health problem. These play a significant role in human morbidity, mortality and economic loss. Ready-to-eat salads are considered as a high-risk food because they do not require any heating, washing or cleaning prior to consumption. Therefore, we aimed to determine the microbiological quality of ready-to-eat salads in our locality. A total of 50 different salads were collected aseptically from different vendors and restaurants of Lahore, Pakistan. Each sample (10 g) was homogenized in stomacher. The homogenized material was serially diluted up to 10–6 using 0.1% peptone water as diluent. The dilutions were inoculated on blood, nutrient and MacConkey agar by Surface-Spread Plate technique and plates were incubated at 35°C for overnight. Aerobic colony count (ACC) was determined by counting the colonies on nutrient agar plates. The identification of the organisms was determined by their morphology, culture characteristics and biochemical profile. The ACC range of salad samples was found to be 1.0 x 10³ cfu/g to 5.8 x 10⁸ cfu/g. Among these, 22% samples showed unsatisfactory level of ACC and 20% were at borderline. The highest ACC (cfu/g) was found in dry vegetables salads (5.8 x 10⁸) and least microbial loads (1.0 x 10³) were observed in vinegar-containing vegetable salads. Among Gram-negative rods Klebsiella spp. (16%) were isolated most frequently followed by Enterobacter spp. (11%). Whereas among Gram-positive cocci, Enterococcus spp. (13%) was foremost followed by Staphylococcus aureus (7.5%). This study revealed the potential hazard of ready-to-eat salads and it is the need of the hour to perform a surveillance study at national scale.