Desenvolvimento de material de referência para microbiologia de alimentos contendo Listeria monocytogenes em matriz queijo / Development of reference material for food microbiology containing Listeria monocytogenes in matrix

A NBR ISO/IEC 17025:2005, uma das normas mais utilizadas em laboratórios de ensaio, descreve como um de seus critérios para a garantia da qualidade dos resultados analíticos a participação periódica dos laboratórios em ensaios de proficiência (EP). Os analitos, utilizados nos EP são materiais de referência (MR) provenientes de um mesmo lote, e devem apresentar características de homogeneidade e estabilidade. O objetivo deste estudo foi produzir um MR qualitativo destinado ao ensaio de pesquisa de Listeria monocytogenes em matriz queijo pela técnica de liofilização. Para a produção do MR, foi utilizado como matriz o queijo Minas frescal (QMF) ultrafiltrado. A matriz foi distribuída em frascos, contaminada com a bactéria alvo e submetida à liofilização, tendo a sacarose como crioprotetor. O MR produzido foi considerado homogêneo e estável na temperatura de ≤-70°C durante todo o período estudado (10 meses). O material apresentou estabilidade a 4, 25, 30 e 35°C por quatro dias e a -20°C por 48 dias, e os resultados estatísticos indicam tendência à estabilidade. Conclui-se que o material apresentou todos os requisitos necessários de um MR de qualidade e poderia ser transportado aos laboratórios participantes de um EP à temperatura máxima de 35°C por até quatro dias, uma vez que os resultados indicaram a manutenção da concentração celular nesse período. Esse foi o primeiro trabalho a descrever uma metodologia de produção de MR contendo L. monocytogenes em matriz queijo.

The standard most used in testing laboratories, ISO/IEC 17025:2005, describes the participation of laboratories in periodic proficiency testing (PT), as a criteria for quality assurance of analytical results. The analyses used in PT are reference materials (MR) from the same lot, and must have characteristics of homogeneity and stability. This study aimed to produce a qualitative RM for detection of Listeria monocytogenes assays in cheese matrix. For the production of RM, Minas Frescal cheese (MFQ) was used as matrix. The matrix was distributed in flasks, contaminated with the target bacteria and submitted to freeze-drying. Sucrose was used as cryoprotector. The RM produced was considered homogeneous and stable at -70°C during the entire period of study (10 months). The material showed stability at 4, 25, 30 and 35°C for 4 days and at -20°C the RM showed stability for 48 days, and the statistical results indicate a tendency to maintain stability. It was concluded that the material showed all the requirements of an RM quality and could be transported to the laboratory participants of a PT at 35°C up to 4 days, since the results indicate the maintenance of cell concentration during this period. This is the first study to describe a methodology for producing MR containing L. monocytogenes in cheese matrix.

Antimicrobial resistance profiles of enterococci isolated from poultry meat and pasteurized milk in Rio de Janeiro, Brazil.

The enterococci are important nosocomial pathogens with a remarkable capacity of expressing resistance to several antimicrobial agents. Their ubiquitous nature and resistance to adverse environmental conditions take account for their ability to colonize different habitats and for their potential for easy spreading through the food chain. In the present study we evaluated the distribution of species and antimicrobial susceptibility among enterococcal isolates recovered from food obtained in retail stores in Rio de Janeiro, Brazil. The following species were identified among 167 isolates obtained from poultry meat and 127 from pasteurized milk: Enterococcus faecalis (62.6%), E. casseliflavus (17.3%), E. durans (6.5%), E. gallinarum (3.0%), E. gilvus (2.4%), E. faecium (2.0%), E. hirae (1.4%), and E. sulfureus (1.0%). The overall percentages of antimicrobial resistant isolates were: 31.2 % to tetracycline, 23.8% to erythromycin, 11.3% to streptomycin, 4.3% to chloramphenicol, 3.9% to gentamicin, 1.4% to norfloxacin, 1.1% to imipenem, 0.7% to ciprofloxacin, nitrofurantoin, and penicillin, and 0.4% to ampicillin. Intermediate resistance was detected in frequencies varying from 0.5% for linezolid to 58.2% for erythromycin. None of the isolates showed resistance to glycopeptides. High-level resistance to aminoglycosides was observed in 13.1% of the isolates. Multiresistance was observed in E. faecalis, E. casseliflavus, E. faecium, E. gallinarum, E. durans and E. gilvus.

Antimicrobial resistance profiles of enterococci isolated from poultry meat and pasteurized milk in Rio de Janeiro, Brazil

The enterococci are important nosocomial pathogens with a remarkable capacity of expressing resistance to several antimicrobial agents. Their ubiquitous nature and resistance to adverse environmental conditions take account for their ability to colonize different habitats and for their potential for easy spreading through the food chain. In the present study we evaluated the distribution of species and antimicrobial susceptibility among enterococcal isolates recovered from food obtained in retail stores in Rio de Janeiro, Brazil. The following species were identified among 167 isolates obtained from poultry meat and 127 from pasteurized milk: Enterococcus faecalis (62.6 percent), E. casseliflavus (17.3 percent), E. durans (6.5 percent), E. gallinarum (3.0 percent), E. gilvus (2.4 percent), E. faecium (2.0 percent), E. hirae (1.4 percent), and E. sulfureus (1.0 percent). The overall percentages of antimicrobial resistant isolates were: 31.2 percent to tetracycline, 23.8 percent to erythromycin, 11.3 percent to streptomycin, 4.3 percent to chloramphenicol, 3.9 percent to gentamicin, 1.4 percent to norfloxacin, 1.1 percent to imipenem, 0.7 percent to ciprofloxacin, nitrofurantoin, and penicillin, and 0.4 percent to ampicillin. Intermediate resistance was detected in frequencies varying from 0.5 percent for linezolid to 58.2 percent for erythromycin. None of the isolates showed resistance to glycopeptides. High-level resistance to aminoglycosides was observed in 13.1 percent of the isolates. Multiresistance was observed in E. faecalis, E. casseliflavus, E. faecium, E. gallinarum, E. durans and E. gilvus.