Bacteriological Quality And Safety Evaluation Of Raw Milk And The Source Of Harmful Bacteria In Gansu Province Of China

Milk was recognized as the most completely food product in nature,it provides almost all macronutrients and trace elements for human body and has an irreplaceable role and status in the human diet.Raw milk,as the upstream of the dairy supply chain,is the constraint of dairy development in China.In this paper,raw milk sampling from farms in Gansu province were studied,mainly including total bacteria count,total spore count,the dominant harmful bacteria and its source.The main results summarized were as followings:1.The total bacteria count and total spore count of raw milk in Gansu province were 14,975 cfu/m L and 32 ?/m L,except some retail farming,most total spore count could reach the acquisition standards of UHT,and all of the total bacteria count reached the acquisition standards of China;Compared to the intensive scale farming,retail farming had much more quantities of bacteria and spores,the counts of bacteria and spores were significantly in summer and winter in Gansu province.2.A total of 105 bacteria were isolated from raw milk samples in summer and winter in Gansu province,which belonged to 12 genera,Bacillus and Staphylococcus were the dominant bacteria,the species were associated with the season and farm.Bacillus and Staphylococcus were the dominant bacteria in summer,but few Staphylococcus were isolated in winter,and the species of bacteria in retail farming were more diversity.Corynebacterium,Microbacterium,Chryseobacterium,Escherichia coli and Citrobacter were pathogenic bacteria;Bacillus,Acinetobacter,Pseudomonas,Deinococcus and Kocuria were spoilage bacteria isolated in raw milk of this region.3.Staphylococcus aureus were resistant to almost all of the antibiotics and some of them had multi-drug resistance,the isolates' rates of resistance to penicillin,erythromycin and compound sulfonamide were 80%,75% and 75%,there was a certain resistance to ampicillin,tetracycline and gentamicin,and few strains were resistant to amoxicillin,ciprofloxacin and chloromycetin.Staphylococcus aureus showed multi-drug resistance,most of strains wereresistant to tetracyclines,penicillin,ampicillin and compound sulfadiazine.All strains were susceptible to cefalexin,so cefalexin could be a prior choice for the treatment of mastitis in lactating cows in this region.4.Bacillus and Staphylococcus aureus were dominant bacteria in this region,the playground was the heaviest region polluted seriously.The result of specific PCR revealed that the detection rate of Bacillus,Staphylococcus aureus and Acinetobacter were 75.36%,39.13% and 21.74%,The detection of possible contamination showed that Bacillus were found in silage,bulk tank wall,bedding material and playground;Staphylococcus aureus was detected in silage,bedding material and playground,both bedding material and playground had high detection rate;the detection of Acinetobacter was similar to Bacillus,but low detection rate.From above,we could see silage playground was heavily polluted areas in these farms,and staff in farm should pay much more attention to these areas.