Distribution of Salmonella Typhimurium in Environmental Samples

Abstract

Contaminated leafy greens are occasionally involved in disease outbreaks through enteric pathogens. In order to control the contamination it is important to understand the factors that influence enteric pathogen survival. The study aimed to examine the effect of temperature and application of food grade reagents (sodium benzoate, acetic acid and potassium sorbate) on the survival of Salmonella and microbial contamination within lettuce produced in Rawalpindi and Islamabad. Samples were analyzed under low (4°C) and high temperature (41.5 °C) storage conditions to predict the potential growth and survival of Salmonella in lettuce. Salmonella count were observed to increase significantly (P < 0.05) at low temperature (3.4 – 4.1 log cfu/g) whereas it decreased at high temperature storage conditions (3.4– 0.36 log cfu/g; P < 0.05). Heterotrophic plate count (HPC) in lettuce ranged from 5.6 – 5.971 log cfu/g; P < 0.05 at 4°C and 5.6 – 3.18 log cfu/g; P < 0.05 at 41.5 °C. Microbial and Salmonella count within lettuce samples exceeded the World Health Organization (WHO) 2.3 log cfu/g and International Commission on Microbiological Specifications for Food standards (ICMSF) permissible limit of 103 cfu/g. Among the different organic acid treatments, acetic acid proved to be more reliable as it reduces HPC count by 69 % (5.6 – 1.7 log cfu/g) and Salmonella count by 64 % (3.4 – 1.1 log cfu/g). Potassium sorbate exhibited 29 % HPC reduction (5.6 – 4.1 log cfu/g) and 19 % Salmonella count (3.4 - 2.8 log cfu/g) whereas sodium benzoate showed a reduction of HPC by 27 % (5.6 – 3.9 log cfu/g) and Salmonella count by 11 % (3.4 – 3.1 log cfu/g).