Assessment of Microbiological Quality of Raw Milk and Identification of Pathogenic Bacteria

Abstract

Milk contains important nutrients such as minerals, vitamins, proteins and lipids and are consumed by all age group of humans around the world. It is impossible to avoid contamination of milk with micro-organisms because presence of nutrients therefore quality of milk can be determined by the microbial content in milk. Objective: To investigate the microbiological quality of raw milk. Methods: In the present study, there were 30 cow milk samples collected from different dairy farms of Lahore. Firstly, a surf field mastitis test was performed for detection of clinical and sub-clinical mastitis. The microbial isolation was performed by microbial culturing and biochemical tests and antibiotic sensitivity test was performed for isolated bacteria. These isolated bacterial DNA was extracted and amplified by 16S rRNA PCR. The precipitated amplicon was sequenced by 16S rRNA sequencing. The results were evaluated statistically to check the level of significance among them. Results: The Chi-square values of catalase test, oxidase test, indole test, methyl red test, Voges Proskauer test and triple sugar iron were 12.42, 13.77, 8.77, 9.02, 10.67 and 4.29 respectively and the p-values were 0.034, 0.031, 0.042, 0.039, 0.044 and 0.056 respectively on MacConkey Agar. The Chi-square values of catalase test, oxidase test, indole test, methyl red test, Voges Proskauer test and triple sugar iron were 12.44, 11.98, 9.38, 7.02, 14.22 and 10.43 respectively and p-values were 0.034, 0.045, 0.039, 0.012, 0.022 and 0.053 receptively on Mannitol salt Agar. The Chi-square and p-values of gram staining bacteria were 13.99 and 0.034 respectively and showed the significant relationship among them. Mastitis test were presented the value of Chi-square 17.86 and p-value 0.029. The ANOVA table on DNA isolation method were exposed the highly significant relationship among the variables. Conclusions: There was a significant association between different treatments. Different pathogens can grow in milk and milk products and produce toxic metabolites. Products that are contaminated by these toxic metabolites when consumed may results in food poisoning