The contamination in the milk results from microorganisms during processing and site of production. The source of bacteria may be from the milking equipment’s, udder of the animals or after milk in handling procedure. The study was aimed to isolate E. coli and staphylococcus from milk (dairy farm, milk sellers and house) and milk products (viz. Yogurt, Ice cream, Khoa and Butter). The present study was performed to assess the microbiological quality of milk sold in and around Hyderabad city, India. 105 milk and milk products (viz; Yogurt, Ice cream, Khoa and Butter) samples were collected in and around Hyderabad. Each sample was enriched in peptone water and incubated at 37 °C for 24 hours. Each inoculum was cultured on selective medium for staphylococcus (Baird parker agar) and E. coli (Mac Conkey Lactose Agar) and incubated at 37 °C for 48 hours and 24 hours respectively. The isolated colonies were subjected to cultural, morphological, staining and various biochemical characteristics for their identification and confirmation. The outcomes of the present study revealed that out of 105 samples, 21 samples were found to be contaminated with Staphylococcus (10) and E. coli (11). The highest degree of contamination was recorded in milk from milk sellers on cycle (5) while the lowest was recorded in Ice cream (1). The present study reveals that the collected milk and milk products were found to be contaminated with Staphylococcus and E. coli which may cause food poisoning and pose a threat to public health. It indicates a need for more strict hygienic practices. To ensure that only good quality milk is sold, and there should be proper quality control system. This will improve the reputation as a quality milk supplier, increase the profits and protect the health of consumers.

Keywords: Food poisoning, Public Health, Entero-pathogenic bacteria.

INTRODUCTION

The most common contaminants i.e. E. coli and Staphylococcus; pathogenic bacteria could be an important causative agent for gastrointestinal infections including food poisoning and food borne illness. Raw and unpasteurized milk obtained from milch cow and buffalo by hand milking may contain bacteria from cow’s udders, flies, manure etc. Indigenous sweet based product like Khoa is highly susceptible to variety of microorganism because of high nutritive value and complex chemical composition (Soomro et al., 2003). Contamination of this product with pathogenic bacteria can serve as a source of spread of certain harmful human disease like TB, gastroenteritis, Brucellosis, Salmonellosis, and Staphylococcal food poisoning (Jay et al., 1978). Besides these, enterotoxins produced by Staphylococcus aureus, is the most dangerous and harmful for the human health. About 50% strain of this organism are able to produce enterotoxins associated with food poisoning (Payne and Wood, 1954). Especially in India, rate of infection is still higher because of warm and humid climate (Bhatia and Zahoor, 2007). There is evidence that Staphylococcus aureus was isolated from Khoa samples (Masud et al., 1988; Teufal et al., 1992). The most important source of contamination is probably the human. The contaminants reached the products either during cooking or handling after cooking (Ghosh and Laximiniarayan, 1976). Raw milk represents an ideal growth medium for microorganism (Haridy, 1992). Among all unpasteurized samples, E. coli is frequently contaminating organism and is reliable indicator of faecal pollution (Diliello, 1982). E. coli was isolated from milk products like Mawa, Khoa, Cream, Yogurt, Cheese, Butter, Gulabjamun (Bhat et al., 1948; Kumar and Sinha, 1989; Kulshrestha, 1990). Supply of milk to the people in Hyderabad city (India) through different marketing channels such as directly from dairy farms, milk sellers, milk collection centres and milk vendors of the surrounding areas and is based on unorganized marketing system. Hence, the present study was undertaken to evaluate the quality of raw milk.

MATERIALS AND METHODS

A total of 105 samples of milk (dairy farm, milk sellers and house) and milk products (viz; Yougurt, Ice cream, Khoa, Butter) were collected from different places of Hyderabad, India. 15 samples of each product were collected in sterilized test tubes and brought to laboratory for isolation and identification of bacteria.
Staphylococcus: Each sample was enriched in peptone water and incubated at 37 °C for 24 hours. Each inoculum was cultured on Baird parker agar (selective medium for Staphylococcus) and incubated at 37 °C for 48 hours. The colonies appeared as black colour then a single isolated colony was then picked and streaked on nutrient agar slant and further the organism was identified on the basis of their cultural, morphological, staining and various biochemical characteristics as described by Cruickshank (1970). All positive samples were subjected to coagulase test for confirmation of Staphylococcus aureus as described by Monica (1991).
E. coli: Each sample was enriched in peptone water and incubated at 37 °C for 24 hours. Each inoculum was streaked on Mac Conkey Lactose Agar (MLA), a differential media and pink colored colonies appeared after incubation at 37 °C for 24 hours. A single isolated colony was then picked and streaked on nutrient agar slant. The cultural characteristics of isolates were confirmed by streaking the pure culture on Eosin Methylene Agar (EMB) and further various bio- chemical tests were performed.

RESULTS

In the present study, it was found that out of all milk samples the highest contamination was recorded in the milk collected from milk sellers (33.3%) followed by dairy farm (26.6%) and house milk (13.3%). This may be due to unhygienic handling of milk. In case of milk products, the contamination was recorded as Yogurt (20%), Butter (20%), Khoa (20%), and Ice cream (6.6%), respectively suggesting that it could be due to contaminated environment and unhygienic handling or preparations.

Table1. Study of microbiological quality of milk and milk products for the detection of E. coli and Staphylococcus. Click here to view full image

DISCUSSION

The animals are the main source of contamination that probably results in high number of microbial flora in raw milk. Bacteria can easily enter dairy utensils and milk contact surfaces present in water, soil, manure etc and further transferred to milk. Bacteria might grow in great amounts if the milk contact surfaces are improperly cleaned. The present study revealed that the milk samples (33.3%) were of poor category while the 73.4 % of milk samples from dairy farms were found to be of good quality as these were properly pasteurized which corroborates the study performed by Ziney et al., (2007). Donkor et al., (2007) also conducted the similar studies in milk samples. They cultured and identified different bacterial strains. Due to poor hygiene condition probable faecal contamination of the milk was mostly caused by Enterobacteria. They identified most of the microorganisms and prevalence rate were Mycobacterium spp. (1%), Bacillus spp. (11.5%), Staphylococcus spp. (14.6%), Escherichia coli (2.1%), Proteus spp. (7.3%), Yersinia spp. (19.8%), Enterobacter spp. (6.3%) and Klebsiella spp (16.7%), respectively.

CONCLUSION

The present study reveals that the collected milk and milk products were found to be contaminated with Staphylococcus and E. coli which may cause food poisoning and pose a threat to public health. It indicates a need for more strict hygienic practices, regular sterilization of dairy equipments, washing of utensils, milker’s hands, udder, eradication of diseased animals, pasteurization/boiling of milk before collection and distribution for consumption and product making. To ensure that only good quality milk is sold, and there should be proper quality control system. The milk chain from farm gate to final dairy products should be assured for better quality of milk. Milk sellers, dairy farms, state regulatory departments, retail distributors, milk and milk product processors, and consumers of dairy products should have a major concern for production of quality milk. We can ensure that good quality milk can be produced by using this simple quality control system. This will improve the reputation as a quality milk supplier, increase the profits and protect the health of consumers.

CONFLICT OF INTEREST
None declared.

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