Modelling the Effect of Different Storage Temperatures on the Growth and Toxin Production of Staphylococcus aureus in Milk

Introduction:  In India, 80% of the milk is produced by the rural producer and handled by an unorganized sector. The remaining 20% is handled by an organized sector. The maintenance of the cold chain is a difficult task; as most of the milk chilling centers are nonfunctional or underutilized. This leads to exposure of consumers to pathogenic bacteria and their toxins.

Purpose:   The purpose of this study was to assess the growth of Staphylococcus aureus and its toxin production using a Quantitative Microbial Risk Assessment (QMRA) model under different storage temperatures.

Methods:   A QMRA model was constructed using the published literature data, data for India and consumption from NDDB, India using two scenarios viz., high temperature and low temperature storage scenarios, and by using three modules to assess the exposure of S. aureus and SEA toxin in the population (India) that consumes the milk contaminated with S. aureus.

Results:  The mean dose exposure to toxins was calculated as 159.12 ng/serving. It was also found that in 95% of the cases, the probability of risk of illneess to at least one recipient was equal to or less than 0.00004. In 99% of the cases, the probability of illness due to the consumption of S. aureus contaminated milk is 0.00008.

Significance: The results predicted that S. aureus levels could surpass the 10⁵ CFU/ml level of concern, at the 70^th percentile of servings; and therefore, may represent a potential consumer risk to the SEA enterotoxin.