MVSc

A total of 144 raw milk samples, consisting of individual and pooled milk samples collected from three societies, viz. S1, S2 and S3 were tested to assess the microbial quality by determining Total Viable Count (TVC), Coliform Count (CC), Escherichia coli Count (ECC), Faecal Streptococcal Count (FSC), Psychrotrophic Count (PC), and Yeast and Mould Count (YMC). The presence of certain bacterial pathogens like Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Yersinia enterocolitica, Aeromonas and Salmonella was also assessed.
Statistical analysis of the data revealed highly significant difference (P<0.01) in microbial counts of individual samples of the three sources. The overall mean total viable count, coliform count, faecal streptococcal count, psychrotrophic count, and yeast and mould count was 6.12 ± 0.07, 3.27 ± 0.04, 3.06 ± 0.05, 3.81 ± 0.06, 3.48 ± 0.07 log10 cfu/ml, respectively. Escherichia coli was not detected in 61.11 per cent of individual samples. The overall Escherichia coli count of the samples was 1.23 ± 0.15 log10 cfu/ml. Samples of S2 had the highest mean count. Highly significant (P<0.01) and positive correlation was observed between all the bacterial counts. Association between total viable count and psychrotrophic count, total viable count and coliform count and coliform count and psychrotrophic count was the highest.
Anlaysis of variance test of the data revealed highly significant (P<0.01) difference between the bacterial count of the 36 pooled milk samples obtained from the three sources. The overall mean total viable count, coliform count, faecal streptococcal count and psychrotrophic count were 6.52 ± 0.08, 3.47 ± 0.07, 1.52 ± 0.27, 3.37 ± 0.07 and 4.26 ± 0.07 log10 cfu/ml, respectively. Significant (P<0.05) difference was observed in the mean yeast and mould count of pooled milk samples and the overall mean count was 3.85 ± 0.09 log10 cfu/ml. The highest mean microbial count was observed in the samples of S2. Highly significant (P<0.01) and positive correlation was observed between total viable count and other bacterial counts. The correlation between psychrotrophic count and other counts was also very high.
Among the individual samples of S1, highest mean total viable count was seen in the samples of F4 (6.75 ± 0.07 log­10 cfu/ml) and the lowest mean count was in the samples of F2 (4.68 ± 0.05 log­10 cfu/ml). The highest coliform count and psychrotrophic count were observed in the samples of F4 and the lowest count was seen in the samples of F2. Samples of F4 had the highest Escherichia coli count (2.68 ± 0.54 log­10 cfu/ml). and the lowest count was observed in the samples of F6 (1.04 ± 0.66 log­10 cfu/ml). None of the samples of F2 and F3 revealed the presence of the organism. Faecal streptococcal count was the highest in the samples of F5 and the lowest mean count was in the samples of F2. The mean yeast and mould count was the highest in samples of F4 (4.26 ± 0.06 log­10 cfu/ml) and the lowest in the samples of F2 (2.25 ± 0.07 log­10 cfu/ml). The association between psychrotrophic count and the other bacterial counts was highly significant (P<0.01). Highly significant (P<0.01) association was also observed between total viable count and coliform count.
The total viable count of individual samples of S2 showed highly significant (P<0.01) difference. Samples of F2 had the highest mean count (6.72 ± 0.06 log­10 cfu/ml). The lowest mean count was observed in the samples of F6 (6.09 ± 0.08 log­10 cfu/ml). All bacterial count, except Escherichia coli count was highest in the samples of F2. The highest Escherichia coli count was in the samples of F3. All the microbial counts, except faecal streptococcal count was lowest in the samples of F6. Faecal streptococcal count was lowest in the samples of F3.
Total viable count of samples of farmers belonging to S3 showed highly significant (P<0.01) difference. The samples of F1 had the lowest count (4.74 ± 0.04 log­10 cfu/ml) and the highest count was observed in the samples of F6 (6.72 ± 0.05 log­10 cfu/ml). All microbial counts were highest in the samples of F6.

Escherichia coli was isolated from 38.89 per cent individual samples and 47.22 per cent of pooled milk samples. Only 23 isolates from individual samples and eight isolates from pooled milk samples were serotyped. The serotypes obtained were O5, O24, O25, O68, O84, O87, O103, O116, O157 and O172. Out of the isolates, 14 and five from individual samples and seven and two from pooled samples were untypable and rough, respectively. Congo red binding property was shown by 17 serotyped and 10 untypable isolates obtained from individual milk samples and five serotyped and four untypable strains obtained from pooled milk samples.
Staphylococcus aureus was isolated from 28.70 per cent of individual and 27.78 per cent of pooled milk samples. Listeria monocytogens was isolated from two individual milk samples from S3. Bacillus cereus was isolated from two milk samples obtained from S2. Aeromonas was isolated from 12.04 per cent of individual samples and 25.00 per cent of pooled milk samples. From the individual samples, seven isolates of Aeromonas sobria and six isolates of Aeromonas caviae were obtained. From the pooled milk samples, three isolates of Aeromonas hydrophilia and six isolates of Aeromonas caviae were obtained.
Antibiogram of the Escherichia coli isolates revealed that the isolates were highly sensitive to cephotaxime, chloramphenicol, ciprofloxacin and gentamicin whereas 11.86 per cent isolates were resistant to streptomycin. Staphylococcus aurues isolates were sensitive to cephotaxime, chloramphenicol, ciprofloxacin and gentamicin. But 19.51 per cent and 9.76 per cent isolates were resistant to erythromycin and penicillin, respectively.
Grading of individual milk samples based on total viable count as per the standards prescribed by Indian Standards (1977), revealed that 42.59 per cent samples were graded as fair. Only 16.67 per cent samples were graded as very good whereas 20.37 per cent each were graded as good and poor. None of the pooled milk samples was graded as very good, while 16.67, 58.33 and 25.00 per cent samples were graded as good, fair and poor, respectively.
Based on methylene blue reduction test, 21.30, 30.56, 39.81 and 8.33 per cent individual samples were graded as very good, good, fair and poor, respectively while, 13.89, 30.56, 47.22 and 8.33 per cent pooled milk samples were graded as very good, good, fair and poor, respectively.
The various critical control points of microbial contamination of milk was evaluated by collecting samples of air, water, hand wash of the handler and utensil wash and subjecting to estimation of the bacterial load. Hand wash was found to be a major source of contamination. The highest microbial count in the samples of air and hand wash was observed in S2. The higher mean microbial count in the milk samples of S2 might be attributed to the contamination from these sources. The microbial count in water and utensil wash was the highest in the samples of S1.