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Abstract
Summary:-One hundred and sixty random samples (85 of raw milk and 75 of pasteurized milk) were collected from different markets and dairy shops in Sharkia Governorate, Egypt. A survey was conducted to determine the bacteriological quality of examined milk samples.
It is evident from the obtained results that the mean values of total mesophilic count/ml of raw and pasteurized milk samples were 3.50×109±1.49×109 and 2.6×105±1.93×105, respectively.
The obtained results revealed that the prevalence of coliforms contamination in raw and pasteurized milk samples were 94.11% and 32%, while the mean coliform count/ml (MPN/ml) in examined raw and pasteurized milk samples were 4.5×108±0.78×108 and 8.7×103±1.42×103, respectively.
Citrobacter freundii, Cit. diversus, Klebsiella pneumonae pneumonae (oxytoca), Kl. pneumonae, Enterobacter aerogenes, Ent. intermedius, Ent. agglumerans and Escherichia coli could be isolated at varying percentages ranging from 2.35% to 31.76%, while in pasteurized milk samples the percentages were 5.33%, 4.00%, 9.33%, 4.00%, 5.33%, 1.33%, 0.00% and 2.66%, respectively.
Concerning the Staphylococci count/ml, the mean was 1.80×105 in examined raw milk samples, while in those of pasteurized ones was 2.70×103.
Staphylococcus aureus and Staphylococcus epidermidis could be isolated from the examined raw milk samples in percentages of 16.47% and 37.64%, while in pasteurized milk samples were 4.00% and 6.66%, respectively.
Bacillus cereus could be isolated from examined raw and pasteurized milk samples at percentages of 17.64% and 21.33% with an average of 3×105 and 3.3×103/ml, respectively.
The mean psycrotrophic count/ml of examined raw and pasteurized milk samples were 9.4×107 and 2.8×103, respectively.
Salmonella failed to be detected in both examined raw and pasteurized milk samples.
Yersinia species could be detected in 29.41% and 9.33% of raw and pasteurized milk samples, respectively.
Yersinia enterocolitica and Yersinia pseudotuberculosis could be isolated from raw and pasteurized milk samples in percentages of (12.94%, 16.47%) and (6.66%, 2.66%), respectively.
Polymerase chain reaction (PCR) was performed for detection of VirF gene in 26 Yersinia enterocolitica isolates (5 strains isolated from pasteurized milk samples and 21 isolated from raw milk samples). The PCR product was visualized after agarose electrophoresis. One amplification band of 590 bp was observed whereas Yersinia enterocolitica colonies were used as template for the PCR.
Y. enterocolitica strains showing positive results for VirF gene were 3(60%) and 6(28.57%) of pasteurized and raw milk samples, respectively.
Grading of raw and pasteurized milk samples according to Egyptian standards (2005) showed that 83.53%, 82.35 and 100% of examined raw milk samples agreed with the Egyptian standards in case of Staph. aureus, Bacillus cereus counts and isolation of salmonellae, while 16.47% and 17.65% exceeded the standard limits of Staph. aureus and Bacillus cereus counts, respectively.
In pasteurized milk samples 86.67%, 68.00%, 96.00%, 78.67% and 100% had the permissible limits of total colony count, total coliform count, Staph. aureus count, Bacillus cereus count and isolation of salmonellae, while 13.33%, 32.00%, 4.00% and 21.33 exceeded the standard limits of total colony, total coliform, Staph. aureus and Bacillus cereus counts, respectively.
The hygienic and public health importance of isolated organisms as well as their control measures were discussed to improve the quality of raw and pasteurized milk to safe-guard the consumers from infection.