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Coxiella burnetii DNA in milk, milk products, and fermented dairy products
2021
Valkovska, Linda | Mališevs, Artjoms | Kovaļenko, Kaspars | Bērzin̦š, Aivars | Grantiņa-Ieviņa, Lelde
Q fever in dairy cattle has been investigated in Latvia since 2012. In 2015, 10.7% of farms tested positive for the DNA of C. burnetii, its aetiological agent, in bulk tank milk. The presence of C. burnetii DNA and infectious bacteria in dairy products has been assessed in several countries, and because Latvian milk may contain them, parallel assessment in this country is recommended. Accordingly, the present study tested shop and farm retail dairy products from Latvia and included foreign products for comparison. Investigation was carried out of 187 samples of a diverse range of dairy products from 41 Latvian milk producers. Twenty-six comparable samples pooled from Estonia, France, Germany, Greece, Italy, Lithuania, the Netherlands, Poland and Spain were also included. The all-countries total number of fermented milk products was 160. Special attention was paid to products that could be more attractive to children because of their added chocolate, cacao, berry and fruit content. DNA was extracted and amplification of C. burnetii IS1111 was performed using a commercial PCR kit. Overall positivity was 60.56%. Domestic products were positive more often (60.96%) than foreign ones (57.69%). Only 26.67% of unpasteurised Latvian cow’s milk samples were positive whereas 76.47% of pasteurised equivalents and 63.13% of fermented milk products were. Sweetened and fruit-containing samples were 71.43% positive. The shedding of C. burnetii via milk should be monitored and only milk from healthy animals allowed for sale for direct human consumption without pasteurisation. Raw milk quality and the effectiveness of industrial heat treatment and pasteurisation methods in Latvia and other countries should be carefully assessed to ensure adequate consumer health protection.
Show more [+] Less [-]Prevalence and Characterization of Some Pathogenic Bacteria in Fermented Milk Products and Mish Cheese in Dakahalia Governorate, Egypt
2022
Rana Abd Elkader Mahmoud Abd El latif | Mohammed El Sherbini El-sayed Ali | Adel Abdelkhalek
Bacterial contamination of fermented dairy products has serious implications for both safeties of the final products, and the transmission of foodborne pathogens to the consumers. In this regard, 175 samples of fermented dairy products including 50 each of plain yoghurt, fruit yoghurt, laban rayeb, and 25 from mish cheese were randomly collected from different supermarkets and retail shops in Dakahlia Governorate, Egypt. Samples were examined bacteriologically for the prevalence of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), particularly, E. coli O157. The recovered isolates were examined for the detection of toxin, and virulence-associated genes using PCR. The obtained results showed that the average counts (CFU/g) of total bacterial, psychrotrophic, coliform, and S. aureus were 1.72x105, 9.9 x103, 5.08x102, and 3.07 x102 for the plain yoghurt, 7.1 x 104, 2.3 x 103, 9.5 x10, and 3.3 x10 for fruit yoghurt, 6.07x104, 6.1 x 103, 9.8 x10, and 1.35x102 for laban rayeb, and 1.2 x 106, 2.5 x104, 8.3 x10, and 7.2 x103 for Mish cheese, respectively. E. coli and E. coli O157 were detected in 13 out of 175 (7.43%) and 4 out of 175 (2.3%) samples, respectively. Using PCR for 9 selected E. coli isolates showed that 7 out of 9 E. coli isolates were positive for the stx1 gene, 5 out of 9 were positive for stx2, and 3 out of 9 were positive for eaeA, and 4 out of 9 were positive for hylA. S. aureus showed that 55.6% of the recovered isolates were coagulase positive. Ten randomly selected S. aureus isolates tested positive for nuc (thermonuclease genes), while mecA (methicillin-resistant S. aureus “MRSA”) gene was detected in 20% of the examined isolates. Therefore, strict hygienic measures should be adopted during all steps of the manufacture of such dairy products.
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