Microbiology of organic and conventionally grown fresh produce

ABSTRACT Fresh produce is a generalized term for a group of farm-produced crops, including fruits and vegetables. Organic agriculture has been on the rise and attracting the attention of the food production sector, since it uses eco-agricultural principles that are ostensibly environmentally-friendly and provides products potentially free from the residues of agrochemicals. Organic farming practices such as the use of animal manure can however increase the risk of contamination by enteric pathogenic microorganisms and may consequently pose health risks. A number of scientific studies conducted in different countries have compared the microbiological quality of produce samples from organic and conventional production and results are contradictory. While some have reported greater microbial counts in fresh produce from organic production, other studies do not. This manuscript provides a brief review of the current knowledge and summarizes data on the occurrence of pathogenic microorganisms in vegetables from organic production.

Microbiology of organic and conventionally grown fresh produce

ABSTRACT Fresh produce is a generalized term for a group of farm-produced crops, including fruits and vegetables. Organic agriculture has been on the rise and attracting the attention of the food production sector, since it uses eco-agricultural principles that are ostensibly environmentally-friendly and provides products potentially free from the residues of agrochemicals. Organic farming practices such as the use of animal manure can however increase the risk of contamination by enteric pathogenic microorganisms and may consequently pose health risks. A number of scientific studies conducted in different countries have compared the microbiological quality of produce samples from organic and conventional production and results are contradictory. While some have reported greater microbial counts in fresh produce from organic production, other studies do not. This manuscript provides a brief review of the current knowledge and summarizes data on the occurrence of pathogenic microorganisms in vegetables from organic production.

Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: Application in the control of Listeria monocytogenes in fresh Minas-type goat cheese

Listeria monocytogenes is a pathogen frequently found in dairy products. Its control in fresh cheeses is difficult, due to the psychrotrophic properties and salt tolerance. Bacteriocinogenic lactic acid bacteria (LAB) with proven in vitro antilisterial activity can be an innovative technological approach but their application needs to be evaluated by means of in situ tests. In this study, a novel bacteriocinogenic Lactococcus lactis strain (Lc. lactis DF4Mi), isolated from raw goat milk, was tested for control of growth of L. monocytogenes in artificially contaminated fresh Minas type goat cheese during storage under refrigeration. A bacteriostatic effect was achieved, and counts after 10 days were 3 log lower than in control cheeses with no added LAB. However, this effect did not differ significantly from that obtained with a non-bacteriocinogenic Lc. lactis strain. Addition of nisin (12.5 mg/kg) caused a rapid decrease in the number of viable L. monocytogenes in the cheeses, suggesting that further studies with the purified bacteriocin DF4Mi may open new possibilities for this strain as biopreservative in dairy products.

Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: characterization of the bacteriocin

Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its antimicrobial activity. The bacteriocin presented a broad spectrum of activity, was sensitive to proteolytic enzymes, resistant to heat and pH extremes, and not affected by the presence of SDS, Tween 20, Tween 80, EDTA or NaCl. Bacteriocin production was dependent on the components of the culture media, especially nitrogen source and salts. When tested by PCR, the bacteriocin gene presented 100% homology to nisin Z gene. These properties indicate that this L. lactis subsp. lactis DF4Mi can be used for enhancement of dairy foods safety and quality.

Bacteriocinogenic Lactococcus lactis subsp: lactis DF04Mi isolated from goat milk: Evaluation of the probiotic potential

Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its probiotic potential. Lc. lactis DF4Mi was resistant to acidic pH and oxbile, presented co-aggregation with Listeria monocytogenes, and was not affected by several drugs from different generic groups, being sensitive to most tested antibiotics. These properties indicate that this Lc. lactis strain can be used for enhancement of dairy foods safety and quality, in combination with potential probiotic properties.

Characterization of class 1 integrons and antibiotic resistance genes in multidrug-resistant Salmonella enterica isolates from foodstuff and related sources

In recent years, an increase in the occurrence of antimicrobial resistance among Salmonella enterica has been observed in several countries, which is worrisome because S. enterica is one of the most common causes of human gastroenteritis worldwide. The aim of this study was to characterize class 1 integrons and antibiotic resistance genotypes in Salmonella enterica isolates recovered from foodstuff and related sources. Nineteen multidrug-resistant (MDR) Salmonella enterica isolates were recovered. Higher resistance rates to tetracycline (90 percent), streptomycin (80 percent), sulfamethoxazole-trimethoprim (80 percent), ampicillin (60 percent) and nalidixic acid (70 percent) were related to the presence of the tetA, aadA, sul1/sul2, blaTEM-1 genes, and a codon mutation at position 83 of the gyrA gene, respectively. Class 1 integrons harboring aadA, blaTEM-1, sul1 or dhfr1 genes were detected in nine (45 percent) Salmonella enterica strains belonging to serotypes Brandenburg, Panama, Agona, Mbandaka and Alachua. Finally, clonal dissemination of S. Panama, S. Derby and S. Mbandaka was confirmed by PFGE. Detection of clonally related MDR Salmonella enterica suggests that endemic serotypes can be supported by class 1 integron-borne gene cassettes and/or mutations in drug targets. Emergence and dissemination of multidrug-resistant Salmonella enterica can have a major public health impact in an environment where large-scale suppliers ship their products.

Behaviour of L. monocytogenes in sliced, vacuum-packed mortadella / Comportamento de L. monocytogenes em mortadelas fatiadas e embaladas a vácuo

This study evaluated the growth of naturally occurring L. monocytogenes in sliced, vacuum-packed mortadella samples during storage at 5ºC until the expiration date. Tukey's test indicated that counts of L. monocytogenes on 0, 10, 20, 30 and 40 days of storage were significantly different (p<0.05), indicating growth during shelf life. In three trials, the mean increase was 1.72 log cycles. Vacuum packing and storage under refrigeration were not effective in controlling the growth of L. monocytogenes in sliced mortadella, indicating that good manufacturing practices and implemented HACCP programs are essential to assure safety of this product.

O presente trabalho avaliou a multiplicação de L. monocytogenes naturalmente presente em mortadelas fatiadas, embaladas a vácuo e estocadas a 5ºC durante sua vida de prateleira. O teste Tukey indicou que as populações de L. monocytogenes nos tempos 10, 20, 30 e 40 dias diferiram significativamente (p<0,05) indicando multiplicação durante o armazenamento. Em três repetições, o aumento médio foi de 1,80 ciclos log. A embalagem a vácuo e estocagem sob refrigeração não foram suficientes para o controle da multiplicação de L. monocytogenes em mortadelas fatiadas, indicando que as boas práticas de fabricação e um sistema HACCP implantado são fundamentais para assegurar a segurança desse produto.

Performance of two ready-to-use systems for enumeration of aerobic mesophilic microorganisms in frozen goat milk

Foi demonstrado que a enumeracão de microrganismos aeróbios em leite bovino brasileiro pasteurizado utilizando-se as placas PetrifilmTM AC e SimplateTM TPC pode ser influenciada pela microbiota autóctone. O presente estudo foi conduzido para se determinar se o mesmo ocorreria com leite de cabra pasteurizado. Foram analisadas 62 amostras de leite pasteurizado e congelado, vendidas no comércio varejista de São Paulo, SP. As amostras foram submetidas à contagem de microrganismos aeróbios mesófilos utilizando-se placas PetrifilmTM AC e SimplateTM TPC, comparando-se os resultados com a semeadura em profundidade. Um índice de correlacão acima de 0,90 foi classificado como excelente, entre 0,80 e 0,89 como bom, entre 0,79 e 0,50 como fraco, e abaixo de 0,50, como ruim. O índice de correlacão para as contagens em placas PetrifilmTM AC foi bom, mas foi ruim quando se usou as placas SimplateTM TPC. A comparacão entre os resultados obtidos com as placas PetrifilmTM AC e SimplateTM TPC também produziu um índice de correlacão ruim. Os resultados sugerem que a microbiota autóctone têm pouca ou nenhuma influência sobre a performance destes dois sistemas, pois boas correlacões foram obtidas com o uso das placas PetrifilmTM AC.

Rapid detection of Salmonella in foods using a combination of 'SPRINT POT TM`, 'MSRV POT TM` and Salmonella Latex 'TEST POT TEM`

A new procedure for rapid detection of Salmonella in foods, based on the combination of 'SPRINT POT.TM`, 'MSRV POT.TM` and Samonella Latex 'TEST POT.TM`, was evaluated. 'SPRINT POT.TM` is a system to reduce the preenrichment and selective enrichment steps to 24 hours. 'MSRV POT.TM`is semi-solid selective media for detection of motile Salmonella. Salmonella Latex 'TEST POT.TM` is a rapid latex agglutination test for Salmonella. Using the three systems in combination, the total time for detection of Salmonella in a food sample is 48h...

Inactivation of Escherichia coli O157: H7 in hamburgers by gamma irradiation

Escherichia coli O157:H7 causes bloody diarrhoea, haemorrhagic colitis and life-threatening complications like haemolytic uremic syndrome and thrombotic thrombocitopenic purpura. Among foods associated with outbreaks caused by this pathogen, hamburger is the most common one. The aim of this research was to determine the radiation dose to reduce the population of E. coli O157:H7 in hamburgers to non-detectable levels in order to render a safer product. Hamburgers, inoculated with Escherichia coli O157:H7, were exposed to gamma radiation (60Co) treatment, with doses ranging from 0 to 0.7 kGy. The average temperature during the process was 5.6§C. Non-inoculated hamburgers were submitted to sensory evaluation after being exposed to irradiation doses of 0.8 kGy and 1.0 kGy. The D10 for the pathogen varied from 0.17 kGy to O.27 kGy in hamburger. Considering the highest D10 value in hamburger, a dose of 1.08 kGy would be sufficient to reduce E. coli O157:H7 contamination in 4 log cycles, without affecting the sensory attributes of the product.

Biochemical characteristics of typical and atypical "Staphylococcus aureus" in mastitic milk and environmental samples of brazilian dairy farms

This study results on the biochemical characteristics of 274 "Staphylococcus aureus" strains isolated from mastitic milk, hands of milkmen and milking machines. Features included colony morphology on Baird Parker agar (BPA), catalase, coagulase, and thermonuclease tests. API-Staph (BioMérieux, France) was used as reference identification system. 39.4(per cent) of the colonies on BPA identified as "S. aureus" were atypical. They were more frequent in milk samples (94.4(per cent)). All "S. aureus" strains were coagulase positive but intensify of the test varied according to the source: enviromental strains were 3+ or 4+, while 17.1(per cent) of strains isolated from milk presented only 1+ or 2+ results. The majority of atypical "S. aureus" strains presented a 4+ coagulase result. 2.2(per cent) of "S. aureus" strains were thermonuclease negative. Sixteen thermonuclease positive and coagulase positive strains were identified as "S. hyicus"

Occurrence of emerging pathogenic vibrio spp in seafood consumed in Säo Paulo city, Brazil

Várias espécies de Vibrio, outras além do V.cholerae e V.parahaemolyticus, podem causar doenças no homem. Cem (100) amostras de alimentos de origem marinha, sendo 56 de ostras (Crassostrea gigas), 20 de mexilhöes (Perna perna) e 24 de camaröes (Penaeus spp.), foram analisadas empregando a metodologia padräo para a pesquisa desses microrganismos. Espécies potencialmente patogênicas como V. vulnificus, V. mimicus e V. cholerae näo foram isoladas de 89 por cento de amostras de ostras, 50 por cento de mexilhöes e 17 por cento de camaröes. Devido à alta incidência desses microrganismos, pode-se concluir que os consumidores estäo expostos a alimentos que representam risco à populaçäo

Doenças microbianas de origem alimentar provocadas por enteropatógenos / Foodborne diseases cauded by enteropathogens

Os alimentos de origem animal ou vegetal podem veicular diversos microrganismos patogênicos. A ingestäo desses microrganismos ou de suas toxinas poderá causar gastrenterite, no caso de enteropatógenos, botulismo e listeriose caracterizada por aborto e menigoencefalite. Seräo abordadas apenas as doenças microbianas provocadas por enteropatógenos veiculados por alimentos

Isolamento de Yersinia sp. em alimentos diversos / Isolation of Yersinia sp. in foods

Yersinia sp. foi pesquisada em 138 amostras de alimentos, assim distribuídas: 30 amostras de leite cru, 33 de leite pasteurizado, 15 de carne moída, 15 de fígado de boi, 15 de fígado de suíno e 30 amostras de alface, todas coletadas ou adquiridas na regiäo da cidade de Araraquara, Estado de Säo Paulo. Foram isoladas: Y. enterocolitica de diferentes sorotipos e Y. intermedia 5,27/Xz em 9,1% das amostras de leite pasteurizado; em 3,3% das de alface, Y. intermedia NAG/Xz; em 20% das de carne moída Y. enterocolitica (celobiose, sacarose, sorbitol-, citrato+)/25/Xz e Y. intermedia de diversos sorotipos, e, em 13,3% das amostras de fígado bovino, Y. intermedia também de diferentes sorotipos. Näo se isolou Yersinia sp. de leite cru e fígado suíno. Apesar de nenhuma das cepas isoladas pertencer a sorogrupos reconhecidamente patogênicos, a presença dessa bactéria nesses alimentos, mantidos sob refrigeraçäo, deve ser vista com restriçäo, uma vez que cepas de sorotipos de Y. enterocolitica consideradas näo patogênicas estäo se adaptando ao homem

Condiçöes higiênico-sanitárias do charque comercializado en Säo Paulo, Brasil / Hygienic-sanitary conditions of charqui commercialized in Säo Paulo, Brazil

Foram avaliadas as condiçöes higiênico-sanitárias de 39 amostras de charque comercializado em Säo Paulo, através de quantificaçäo das bactérias mesófilas aeróbias e facultativas, das bactérias halófilas, dos coliformes totais e fecais e dos fungos. Foi também investigada a presença de Salmonella sp., Staphylococcus aureus, de clostrídios sulfito-redutores e de Bacillus cereus. Os resultados indicaram ausência de Salmonella e de clostrídio sulfito-redutores em todas as amostras. S. aureus foi detectado em 15,4% das amostras, em contagens inferiores a 10**2 UFC/g. B. cereus foi detectado em números significativos em 4 amostras, com contagens entre 10**4 e 10**6 UFC/g. Somente uma das amostras acusou presença de coliformes. Os mesófilos variaram entre 10**3 e 10**7 UFC/g, sendo que em 92% dos casos o nível de contaminaçäo foi superior a 10**4 UFC/g. Resultados bastante próximos a estes foram obtidos na enumeraçäo de halófilos. Entre os fungos, verificou-se predominância de leveduras, que variaram entre 10**1 e 10**4 UFC/g

Análise microbiológica de alimentos infantis / Microbiological analysis of infant foods

Realizou-se exame microbiológico em 54 amostras de alimentos infantis destinados a crianças de 0 a 2 anos de idade, sendo 23 amostras de produtos industrializados adquiridos em supermercados e 16 amostras de sopas e 15 mamadeiras, coletadas em creches da cidade de Araraquara, no Estado de Säo Paulo. Realizaram-se as seguintes análises: contagens de bactérias aeróbicas ou facultativas mesófilas e termófilas, de Staphylococcus aureus, de Bacillus cereus, de organismos anaeróbios clostrídios sulfito-redutores, de bolores e leveduras, pesquisa de Salmonella e Yersinia enterocolitica e a determinaçäo do Número Mais Provável de coliformes totais e fecais. Näo foram encontrados S. aureus, Salmonella, Y. enterocolitica, clostrídios sulfito redutores em nenhuma das amostas. Em proporçöes variáveis foram encontrados, nos três tipos de alimentos analisados, B. cereus, microrganismos aeróbios ou facultativos mesófilos e bolores e leveduras. Coliformes totais e fecais foram constatadas em amostras de mamadeiras