Survival of Shiga toxin-producing Escherichia coli O157:H7 in Minas frescal cheese

Abstract

Shiga toxin-producing Escherichia coli (STEC) D157:H7 strains (isolated by cattle's faeces and a reference strain, EDL933), were inoculated into pasteurized milk (10 2 and 10 3 cells.mL -1) to prepare the Minas frescal cheese. As control was used uninfected milk. Physicochemical and microbiological analyses were performed to milk and elaborated cheese. The D157:H7 strains were quantified in the stages of cheese processing and during 0, 2, 4, 5, 7, 10 and 15 storage days at 8 °C onto Sorbitol MacConkey Agar supplemented with potassium tellurite and cefixime (CT-SMAC). D157:H7 was not present in the pasteurised milk prior to the artificial inoculation. At the end of the processing the cheese had 10 to 100 times more STEC D157:H7 than the initial inoculum. During the storage, the Minas frescal cheese exhibited the largest population increase on the 4th and 5th day when inoculated with 10 2 and 10 3 cells.mL -1, respectively. Additionally, viable cells were found up to the 10th and 15th day, according to the amount of initial inoculum. This number of cells is able to cause infection in humans, and therefore, Minas frescal cheese, even when stored under refrigeration, is a potential vehicle of disease caused by STEC D157:H7.Keywords: cheese; psychrotrophic bacteria; foodborne disease. Practical Application:This study demonstrates that the Minas frescal cheese may be an important vehicle for STEC D157:H7, since this microorganism remains viable in this food for a long period even under refrigeration. In this study we can observe the psychrotrophic behavior of STEC D157:H7 in this rich food which is Minas frescal cheese.

Antimicrobial Usage Factors and Resistance Profiles of Shiga Toxin-Producing Escherichia coli in Backyard Production Systems From Central Chile

“…These production systems have been linked to the occurrence of several zoonotic and non-zoonotic outbreaks worldwide ( 11 , 14 , 15 , 64 ). BPS maintain a wide spectrum of species that harbor STEC, including cattle ( 22 ), sheep and goats ( 23 , 65 ), and poultry and captive wild birds ( 11 , 24 ). Positivity reported by this study (11.76%) is similar to what has been reported in productive animal species (cattle and swine) under industrialized conditions in Chile ( 7 ).…”

“…Therefore, BPS could be an important source of pathogens to people. In this context, reports from BPS estimate STEC prevalence between 0.2 and 74% in dairy cattle ( 22 ), over 70% in sheep and goats ( 23 ), and even a 4% in captive wild birds ( 24 ), with several other reports in different animal species with close in-contact with humans ( 25 , 26 ). Information about positivity to STEC in Latin America is scarce, but a report described STEC isolation in alpacas, raised under small farmer condition in Peru ( 25 ).…”

Shiga toxin‐producingEscherichia coliin the animal reservoir and food in Brazil

“…As a survival strategy in food, STEC uses mechanisms of stress resistance. Some STEC strains may grow at low temperatures ranging from 6·5 to 8°C (Frozi et al ), and resist to acid conditions (pH 2·5) which allow them to survive in foods with an adverse pH and to pass through the stomach. The latter ability is directly related to its low infective dose and high pathogenicity (Tilden et al ).…”

Condições higiênico-sanitárias e percepção de risco dos agentes envolvidos no sistema produtivo, comercialização e consumo do Queijo Minas Frescal

“…Os microrganismos relacionados à contaminação do leite e produtos lácteos são diversos, mas Salmonella spp., Staphylococcus aureus, Listeria monocytogenes e Escherichia coli são os mais comuns, sendo S. aureus relacionado à mastite, doença comum em vacas leiteiras (BELIO et al, 2016;FROZI et al, 2015;RYSER, 2011;UNIVERSITY OF GUELPH, 2008;THOMAS et al, 2008;FOX et al, 2000). Mesmo com a pasteurização, tratamento que pode reduzir ou eliminar os microrganismos, o risco de contaminação existe, seja pela temperatura inadequada do tanque de armazenamento de leite, limpeza e manutenção dos equipamentos deficientes, manipulação incorreta, dentre outros fatores.…”

“…A contaminação mais comum é causada pelos integrantes do grupo dos coliformes (totais e termotolerantes) e estafilococos patogênicos (S. aureus). O uso do fermento lático mesofílico homofermentador pode ser utilizado para inibir a contaminação, no entanto, o queijo apresenta sabor ácido intenso, que não agrada a maioria dos consumidores (BELLIO et al, 2016;FROZI et al, (2015); FURTADO, 2005).…”