Comparison of Coliform Contamination and Endotoxin Levels in Raw Cow’s Milk

Abstract

Background: Milk forms a considerable part of the necessary materials needed for the physical and mental growth of all community members, especially children and the elderly. Since milk is a suitable culture medium for the growth of many bacteria, strict standards have been introduced for its safety. The aim of this study was to evaluate the coliform contamination of raw cow’s milk and the level of endotoxin in it. Methods: Using random sampling, 43 samples of raw cow’s milk were collected in Isfahan, Iran. Coliforms were identified by biochemical tests. Then, the molecular method was employed for the definitive identification of the coliforms. Moreover, endotoxin levels were assessed employing the limulus amebocyte lysate (LAL) test. Results: Results indicated the presence of coliforms in 17 (39.45%) of the raw milk samples. Based on the molecular identification of the isolated coliforms, 10 samples were contaminated with Escherichia coli, five with Enterobacter spp., and two with Klebsiella pneumoniae. The results of the LAL test showed that 17 samples contained 0.250 units, six samples contained 0.125 units, and 20 samples contained 0.063 units of endotoxin. Conclusions: There was a significant correlation between coliform contamination of raw cow’s milk and 0.250 unit/mL endotoxin (P < 0.001). Increasing the number of coliforms in milk samples is consistent with the increase in endotoxin levels.