MVSc

In the present study a total of 108 milk samples were collected from farmers of three societies (S1, S2 and S3) and analysed for microbial quality, by estimating various microbial counts and also by assessing the presence of certain bacteria of public health importance. Antibiotic susceptibility of Escherichia coli and Staphylococcus aureus was also evaluated. The samples were graded based on total viable count and also by methylene blue reduction test. The critical control points of bacterial contamination of milk at various stages of production were also assessed during the investigation.
Analysis of variance test of the data revealed highly significant difference (P0.01) between the mean counts of milk samples collected from three societies. Milk samples from S2 had the highest mean total viable count (6.57 ± 0.13 log10 cfu/ml), coliform count (3.89 ± 0.08 log10 cfu/ml), Escherichia coli count (1.11 ± 0.19 log10 cfu/ml), faecal streptococcal count (3.86 ± 0.08 log10 cfu/ml) and psychrotrophic count (5.57 ± 0.12 log10 cfu/ml). But the highest mean yeast and mould count (4.08 ± 0.01 log10 cfu/ml) was observed in samples collected from S1.
Milk samples from S2 revealed maximum contamination. Analysis of data revealed that highly significant (P<0.01) and positive correlation between various bacterial counts. Highly significant (P<0.01) and positive association was observed between total viable count and psychrotrophic count and also between the former count and faecal streptococcal count.
Microbial analysis of milk samples collected from six farmers of S1 revealed that samples from F4 had highest mean total viable count (7.44 ± 0.01 log10 cfu/ml) and the lowest in samples of F3 (4.82 ± 0.03 log10 cfu/ml). Similarly, the other bacterial counts, viz., coliform count, Escherichia coli count, faecal streptococcal count, psychrotrophic count was also seen in the highest level in the samples of F4. Whereas the highest mean yeast and mould count was observed in the samples of F1.
Microbial analysis of the samples collected from farmers of S2 revealed that the highest mean total viable count (7.42 ± 0.08 log10 cfu/ml) and coliform count (4.44 ± 0.08 log10 cfu/ml) was seen in the samples of F5. Whereas these counts were lowest in the samples of F2. But the Escherichia coli count was highest in the samples collected from F3. However, the organism was not detected in the samples of F2 of S2. The highest mean faecal streptococcal count and psychrotrophic count was also seen in samples of F5, indicating that the hygienic practices followed by the farmer is very poor.
Microbial analysis of the milk samples collected from six farmers of S3 revealed that the samples from F4 had the highest mean total viable count, coliform count, Escherichia coli count, faecal streptococcal count and psychrotrophic count indicating the poor hygienic practices followed by the farmer. The highest yeast and mould count was observed in the samples of F6. The presence of these organisms revealed the unsanitary condition of production of milk.
The public health impact on the consumer was assessed by isolation and identification of Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Yersinia enterocolitica, Aeromonas and Salmonella. The presence of coliforms and faecal streptococci indicate unhygienic handling of milk and possible faecal contamination. Escherichia coli was isolated from 41.67 per cent of the samples examined. A total of 45 isolates were obtained. Only 22 (48.89 per cent) out of 45 isolate were serotyped. The isolates fell into 10 serotypes viz., O116, O24, O84, O145, O172, O125, O79, O87, O103 and O157. Out of these serotypes except 024, 079 and 087 showed a positive congo red binding test which indicate the property of pathogenisity of isolates.
Staphylococcus aureus was isolated from 33 (30.56 per cent) samples. The highest number of isolates was obtained from S2 (14) followed by S1 (12) and S3 (7). Listeria monocytogenes was isolated from 3 (2.70 per cent) samples. All isolates were obtained from F5 of S1. Bacillus cereus was isolated from 3.70 per cent of the total samples. Of the four isolates obtained, one was from S3 and three from S2. The per cent of isolation of Aeromonas was 18.51. Two species of Aeromonas were obtained viz., Aeromonas hydrophila and Aeromonas caviae. None of the samples tested revealed the presence of salmonella and Yersinia enterocolitica.
Antibiogram of Escherichia coli isolates obtained from the samples belonging to various sources revealed that all isolates were sensitive to chloramphenicol, co-trimoxazole and gentamicin. None of the isolates showed resistance to all the antibiotics used. Antibiogram of Staphylococcus aureus isolates revealed that all the isolates were sensitive to chloramphenicol. Highest per cent (36.36) of organisms showed resistance against erythromycin followed by oxytetracycline (21.22). None of the isolates revealed resistance to all the antibiotics used.
Milk samples collected from three societies were graded based on total viable count. Out of the 108 samples analysed 16.67, 29.63, 20.37 and 33.33 per cent were graded as very good, good, fair and poor quality based on BIS (1977). However 16.67 per cent from S1 and 33.33 from S3 were graded as very good. The per cent of samples graded as good, fair and poor from S1 was 19.44, 30.56 and 33.33, respectively. However, the corresponding per cent from S2 was 33.33, 16.67 and 50.00. The per cent of good, fair and poor samples from S3 was 36.11, 13.89 and 16.67, respectively.
Milk samples collected from three societies were graded based on methylene blue reduction test and the result showed that 22.22, 34.26, 25.00 and 18.52 per cent of samples were graded as very good, good, fair and poor, respectively.
The various critical control points of bacterial contamination of milk was evaluated by collecting samples of air, water, rinsinging of utensils, hand wash of the milker and udder washes of the animals and estimating their bacterial load. The highest bacterial counts were observed in the hand wash samples of the milker, followed by udder wash of the animal and these two were considered as the point of major source of contamination of milk. The highest bacterial counts in water, utensil rinsings, hand wash of milker and udder washes of animal were observed in samples collected from S2. Thus it may be inferred that the high bacterial load of milk samples from S2 might be due to the contamination of milk from these sources.
Therefore, utmost care should be given to monitor the microbial quality of milk at various stages of production, and also to identify various sources of bacterial contamination of milk. Then only we can improve the quality and shelf life of milk produced.