Qualidade microbiológica de queijos coloniais sob inspeção higiênico-sanitária comercializados em Porto Alegre

A produção de alimentos inócuos, aptos ao consumo humano, é de extrema importância tanto à saúde pública quanto para atividade econômica. O queijo colonial é tipicamente consumido pela população do Rio Grande do Sul, porém ainda há poucos dados sobre a qualidade microbiológica desse produto. Sendo assim, os objetivos do presente estudo foram: (i) avaliar a qualidade microbiológica de queijos coloniais comercializados em feiras modelo e mercado público de Porto Alegre; (ii) caracterizar as cepas de Staphylococcus aureus e Listeria monocytogenes presentes neste produto quanto a alguns fatores de patogenicidade, resistência e tipificação genotípica. Para tanto, no período de novembro de 2014 a maio de 2015, foram analisadas 205 amostras de queijo colonial inspecionado, compreendendo 17 marcas distintas comercializadas em feiras modelos e no Mercado Público de Porto Alegre. As análises microbiológicas evidenciaram que 47,31% dos queijos estavam não conformes com pelo menos um dos parâmetros microbiológicos estabelecidos na RDC nº12, portanto impróprios ao consumo humano. Com relação à quantificação de coliformes termotolerantes e Staphylococcus coagulase positiva, 10,73% e 40,48% das amostras apresentaram contagens superiores ao limite máximo estabelecido na legislação, respectivamente. Valores acima do padrão aceitável foram observados em 5,85% dos queijos amostrados para ambos os parâmetros. No que diz respeito à pesquisa de Salmonella sp., todas as amostras apresentaram-se em conformidade. Listeria sp. foi detectado em 12,19% dos queijos, dos quais 24% foram classificados como L. monocytogenes, 52% L. inoccua, 16% L. welshimeri/L. seeligeri e 8% L. grayi.

The production of innocuous food, fit for human consumption, is of extreme importance to both public health and economic activity. Colonial cheese is typically consumed by the population of Rio Grande do Sul, but there is still limited data on the microbiological quality of this product. Thus, the objectives of the present study were: (i) to evaluate the microbiological quality of colonial cheeses marketed in model fairs and central market in Porto Alegre; (ii) to characterize Staphylococcus aureus and Listeria monocytogenes strains present in these products according to some pathogenicity and resistance factors as well as to their genotype. Thus, from November 2014 to May 2015, we analyzed 205 samples of colonial cheese, comprising 17 different brands marketed in model fairs and in the Public Market of Porto Alegre. Microbiological analyzes showed that 47.31% of the samples were not compliant with at least one of the microbiological parameters established in RDC nº12, therefore unfit for human consumption. Regarding the quantification of thermotolerant coliforms and Staphylococcus coagulase positive, 10.73% and 40.48% of the samples presented counts higher than the maximum limit established in the legislation, respectively. Values above the acceptable standard were observed in 5.85% of the samples for both parameters. With regard to Salmonella sp., all samples were negative. Listeria sp. was detected in 12.19% of the samples, of which 24% were classified as L. monocytogenes, 52% L. inoccua, 16% L. welshimeri / L. seeligeri and 8% L. grayi. Concomitant isolation of L. monocytogenes and L. inoccua species was observed in one sample. Two samples presented counts of 3.6 NMP.g-1 and 11 NMP.g-1 of Listeria sp.,; in the others, the population found was <3.0 NMP.g-1. Serotyping of L. monocytogenes indicated the presence of serovars 1 / 2a, 1 / 2b and 1 / 2c and the PFGE profile showed five pulse types. The amplification of the nuc gene, confirmed the 83 isolates of Staphylococcus coagulase positive as S. aureus. Regarding the antimicrobial susceptibility profile, all strains were susceptible to cefoxetin, oxacillin and vancomycin. Strains resistant to: penicillin (26.5%) were detected, all of them confirmed as beta-lactamase producers; ciprofloxacin and erythromycin (9.63%); tetracycline (7.22%) and gentamicin (4.81%). Of the total strains, 66.26% were susceptible to all antimicrobials tested, while 6.02% were considered multiresistant. The gene blaZ was detected in 31.32% of the strains. All strains were negative for mecA and lukS-F genes. As for the presence of genes coding for classical SEs, 16.86% amplified some gene being sea and sec the most frequent. From the molecular typing of the 83 strains of S. aureus it was possible to detect 19 different spa types among the 11 brands of cheeses commercialized; the t127 and t002 genotypes were predominant. Three different types of sequences were detected in the four strains of S. aureus selected for typing by the MLST technique performed in silico: ST-133, ST-5 and ST-1. The colonial cheese marketed in model fairs and in the public market of Porto Alegre, was confirmed as a possible carrier of microorganisms that cause DTA. Among these pathogens, the frequency of isolation of L. monocytogenes and, especially, of S. aureus is noteworthy.