Coliform detection in cheese is associated with specific cheese characteristics, but no association was found with pathogen detection

Abstract

Coliform detection in finished products, including cheese, has traditionally been used to indicate whether a given product has been manufactured under unsanitary conditions. As our understanding of the diversity of coliforms has improved, it is necessary to assess whether coliforms are a good indicator organism and whether coliform detection in cheese is associated with the presence of pathogens. The objective of this study was (1) to evaluate cheese available on the market for presence of coliforms and key pathogens, and (2) to characterize the coliforms present to assess their likely sources and public health relevance. A total of 273 cheese samples were tested for presence of coliforms and for Salmonella, Staphylococcus aureus, Shiga toxin-producing Escherichia coli, Listeria monocytogenes, and other Listeria species. Among all tested cheese samples, 27% (75/273) tested positive for coliforms in concentrations >10cfu/g. Pasteurization, pH, water activity, milk type, and rind type were factors significantly associated with detection of coliforms in cheese; for example, a higher coliform prevalence was detected in raw milk cheeses (42% with >10cfu/g) compared with pasteurized milk cheese (21%). For cheese samples contaminated with coliforms, only water activity was significantly associated with coliform concentration. Coliforms isolated from cheese samples were classified into 13 different genera, including the environmental coliform genera Hafnia, Raoultella, and Serratia, which represent the 3 genera most frequently isolated across all cheeses. Escherichia, Hafnia, and Enterobacter were significantly more common among raw milk cheeses. Based on sequencing of the housekeeping gene clpX, most Escherichia isolates were confirmed as members of fecal commensal clades of E. coli. All cheese samples tested negative for Salmonella, Staph. aureus, and Shiga toxin-producing E. coli. Listeria spp. were found in 12 cheese samples, including 5 samples positive for L. monocytogenes. Although no association was found between coliform and Listeria spp. detection, Listeria spp. were significantly more likely to be detected in cheese with the washed type of rind. Our data provide information on specific risk factors for pathogen detection in cheese, which will facilitate development of risk-based strategies to control microbial food safety hazards in cheese, and suggest that generic coliform testing cannot be used to assess the safety of natural cheese.

Gouda cheese spoilage prevention: Biodegradable coating induced by Bunium persicum essential oil and lactoperoxidase system

“…These microorganisms can rapidly degrade lactose and subsequently lead to formation of lactate, acetate, ethanol, and CO 2 in approximately identical ratios (Ledenbach & Marshall, ). Postpasteurization contamination is mainly due to the presence of coliform in cheese which is brought by unsanitary conditions during cheese processing (Kwenda, Nyahada, Musengi, Mudyiwa, & Muredzi, ; Trmčić et al., ).…”

Microbiological changes throughout ripening of Keş cheese

“…Lactic acid production by lactic acid bacteria is probably the cause of the coliform reduction due to its acid sensitivity (Nunez et al, 1985). The presence of coliform bacteria in cheese is the indicator of unsanitary conditions and contamination during cheesemaking (Trmčić et al, 2016). Coliform contamination is undesirable because it creates structural defects in cheese (Donnelly, 2007).…”

Survival and detection of coliforms, Enterobacteriaceae, and gram-negative bacteria in Greek yogurt

“…This testing represents a valuable tool for the dairy industry, allowing processors to identify areas of improvement within their operations that can be targeted to increase the quality and consumer acceptance of finished products (Silva et al, 2010;Costa Dias et al, 2012;Cusato et al, 2013). The majority of published research on dairy hygiene indicators focuses on coliforms in fluid milk and cheese (Martin et al, 2012;Masiello et al, 2016;Trmčić et al, 2016); there is currently little information on the use and detection of bacterial hygiene indicators in low-pH fermented dairy products, such as Greek yogurt. Despite a steady decline in fluid milk consumption in the United States since the 1970s, both the production and consumption of Greek yogurt has greatly expanded in recent decades (Desai et al, 2013;USDA-ERS, 2015).…”