RESUMEN
The aim of this study was to determine the prevalence Cronobacter from 30 samples of oats and 30 of linseeds commercially available in Brazil. The detection of Cronobacter was as according to the ISO 22964:2017. The isolates were characterized according to their phenotypically using Vitek 2.0 and antibiotic susceptibility profile. Molecular characterization was accomplished by real-time PCR targeting dnaG gene, PCR targeting rpoB gene, multiplex-PCR targeting cgcA gene and fusA allele sequencing. A total of 34 samples (56.7%) contained Cronobacter; 19 (63.3%) of linseeds and 15 (50.0%) of oats. The isolates were identified as C. sakazakii (n = 18, 52.9%), C. dublinensis (n = 7, 20.6%), C. turicensis (n = 6, 17.7%) and C. malonaticus (n = 3, 8.8%). Thirty-four Cronobacter isolates were assigned to 11 different fusA alleles of which 3 were new (169, 170 and 171). The PCR targeting rpoB gene and cgcA gene failed to identify 19 isolates. Seven (20.6%) strains showed resistance or intermediate/resistance to tetracycline, and one (2.9%) strain had intermediate resistance to piperacilin-tazobactam. The presence of Cronobacter in oats and linseeds indicate that these foods can be a potential threat to human health, particularly when preparing food for elderly or immunosuppressed persons. The incorrect use of this foods for feeding of neonates (<6 months) by careers should also be avoided.
Asunto(s)
Avena/microbiología , Cronobacter/efectos de los fármacos , Cronobacter/genética , Lino/microbiología , Microbiología de Alimentos , Antibacterianos/farmacología , Técnicas de Tipificación Bacteriana , Brasil , Cronobacter/clasificación , Genes Bacterianos/genética , Humanos , Pruebas de Sensibilidad Microbiana , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Proficiency tests are considered relevant tools of quality control programs used to monitor the laboratory performance and to assess the reliability of tests results. In Brazil, the provision of proficiency testing (PT) is restricted to food microbiology area. Furthermore, high costs reduce the regular participation of national laboratories in these tests. This study evaluated the freeze-drying technique employed for preparing reference materials (RM) to be used in the PT schemes for detecting Salmonella spp. in milk. The concentration of inoculums used for preparing two batches of RM was determined, and the procedures for matrix contamination were standardized. The control trials were established in order to monitor the quality of the produced RM, and among them, there are long and short-term homogeneity and stability assays. The freeze-drying technique proved to be a suitable procedure for producing RM for PT. The RM were stable for the first three months when stored at -20ºC, nevertheless, viability loss could be observed after 12-month storage. The RM were stable at 4C at short-term stability, although when the products were kept at 25C and 37C for seven days, a significant reduction in the number of cells could be observed.
Ensaios de proficiência (EP) são considerados importantes ferramentas para a condução de programas de controle de qualidade, que possibilitam efetuar a avaliação da habilidade de laboratórios em obter resultados precisos. No Brasil é restrita a oferta de EP na área de microbiologia de alimentos. Além disso, os altos custos diminuem a participação regular de laboratórios nacionais nesses ensaios. O presente estudo teve como objetivo realizar a avaliação da técnica de liofilização no preparo de materiais de referência (MR) para EP destinados ao ensaio de detecção de Salmonella spp. em leite. Foi determinada a concentração do inóculo utilizado no preparo de dois lotes e, também, foi padronizado o procedimento de contaminação da matriz. Para monitorar a qualidade dos MR produzidos foram estabelecidos ensaios de controle, dentre eles o teste da homogeneidade e da estabilidade em longo e curto prazo. A técnica de liofilização mostrou ser adequada para a produção de MR de qualidade e aplicável para EP. Os MR apresentaram estabilidade à temperatura de estoque (-20ºC) durante os três primeiros meses, porém foi observada perda de viabilidade após doze meses de armazenamento. Na estabilidade em curto prazo, os MR foram estáveis a 4C, contudo apresentaram redução significativa no número de células quando mantidos a temperaturas de 25ºC e 37ºC durante sete dias.