Brazil: Study finds viral and bacterial contamination of semi-hard cheeses
Data published in FEMS Microbiology Letters indicated that norovirus genogroup I and II (NoV GI-II) and human adenovirus (HAdV) were detected in one and nine samples, respectively.
Scientists from the Laboratory of Comparative and Environmental Virology at the Oswaldo Cruz Institute and the National Institute of Quality Control in Health also reported that five samples were contaminated with Listeria monocytogenes, 27 samples were contaminated with fecal coliform bacteria, and 10 with coagulase-positive staphylococci (CPS).
In all, the scientists analyzed 30 samples each of Minas, Prato and sliced Prato cheese.
“[T]he presence of enteric viruses and the incidence of fecal coliforms and L. monocytogenes in the cheese samples collected in the market suggest deficiencies in hygiene procedures applied during the production line, failures in the storage process of these products and/or their handling,” wrote the authors, led by Fabiana Melgaço from the Oswaldo Cruz Institute.
“Our results stress the need for good manufacturing practices, rigorous quality control systems in the dairy industry and markets, with an emphasis on the inclusion of virological parameters in the monitoring of foods, especially those that are handcrafted, or those that are handled when marketed.”
Study details
The data are in agreement with previously published results from the Brazilian Ministry of Health, said the scientists, which found that milk and dairy products were implicated in 371 outbreaks of foodborne diseases between 2000 and 2017. During that time, Brazilian authorities documented 12,108 outbreaks in total.
For the new study, Melgaço and her co-workers purchased 90 cheese samples from commercially obtained in supermarkets, bakeries, grocery stores across the Greater Metropolitan Region of the State of Rio de Janeiro. All of the samples were purchased in their primary packaging.
In addition to the findings outlined above, the scientists also reported that viruses were detected in 11 samples, with nine of those meeting the microbiological criteria used to evaluate the microbiological quality of the cheeses.
“The results also revealed that cheese samples, which were considered appropriate according to bacterial indicators, were contaminated with viral pathogens,” they wrote. “The viruses do not multiply in or on foods as some bacterial species. So, viral presence in fresh foods does not affect its degradation, or compromise appearance, color, texture, flavor or smell and is therefore undetectable to consumers and represents a health risk.”
Another result to note was the difference between sliced and non-sliced Prato cheese samples, with some sliced samples found to contain HAdV, L. monocytogenes and fecal coliforms at the same time. This indicated that “human manipulation and/or poor hygiene of surfaces contributed to the contamination of the product offered”, said the researchers.
Source: FEMS Microbiology Letters
2018, Volume 365, Number 20, fny225 doi: 10.1093/femsle/fny225
“Assessment of viral and bacterial contamination of fresh and ripened semi-hard cheeses”
Authors: F.G. Melgaço et al.
