The Japanese oyster Crassostrea gigas is commercially grown in bays and estuaries of the Pacific Northwest. The oyster's complex, ciliated, plicate gill is responsible for removing particles from surrounding waters for ingestion. In order to determine how this is accomplished, structural interrelationships of gill components were investigated using scanning electron microscopy and light microscopy. Particle movement was observed directly on both isolated gill sections and intact gills. Feeding data were obtained by comparing initial to final concentration and size of algal particles in a Coulter counter.

Ilex paraguariensis, is used in the preparation of a widely popular tea beverage (Yerba Mate) mainly produced and consumed in the countries of Uruguay, Paraguay, Argentina and Brazil. Dialyzed aqueous extracts were screened for antimicrobial activity against Escherichia coli O157:H7, Staphylococcus aureus, methicillin-resistant S. aureus and S. pseudintermedius, and Pseudomonas syringae pv. tomato. Using a concentrated extract, S. aureus was found to be the more sensitive to extracts than E. coli O157:H7. Minimum inhibitory concentration (MIC) was defined as the lowest concentration of extract tested that did not allow bacterial growth (inhibition) above the original inoculums of approximately 5.0-6.0 log CFU/ml after 24 hr. The minimum bactericidal concentration (MBC) was defined as the lowest concentration tested where bacterial death (inactivation) was observed after 24 hr. MBCs were determined to be ca. 0.150- 0.800 mg protein equivalent/ml and 0.025-0.050 mg protein equivalent/ml against E. coli O157:H7 and S. aureus respectively. Using a lyophilized extract, MICs were determined to be 5 mg/ml for two strains of E. coli O157:H7 and MBCs 5 mg/ml for E. coli O157:H7 strain ATCC 43894 and 10 mg/ml for E. coli O157:H7 strain ‘Cider’ in microbiological media. An approximately >4.5 log reduction was observed for E. coli O157:H7 treated with 40 mg/ml extract in modified apple juice, which approximate to the requirements of the United States Code of Federal Regulations (21 CFR part 120). We demonstrated antimicrobial effectiveness of aqueous extracts after 24 hr at 1 and 2 mg/ml against all strains of methicillin-resistant S. pseudintermedius and of S. aureus tested respectively. An approximately >5 log reduction was observed in all strains at all concentrations after 24 hr. Methicllin-resistant Staphylococcus aureus (MRSA) strains appeared more susceptible to the extract than methicillin-resistant Staphylococcus pseudintermedius (MSRP) strains. It was concluded that aqueous extracts of Yerba Mate demonstrated broad activity against foodborne, human, animal and plant pathogenic bacteria, including strains demonstrating resistance to certain antibiotics.

The focus of this study was to look at relationship between polydispersity caused by high pressure homogenization and molecular weight dependent antimicrobial activity of chitosan. It has been shown that chitosan has antimicrobial activity against bacteria, fungi, and viruses. Chitosan is obtained by partial de-N-acetylation of chitin which, consists of a ß 1-4 copolymer of glucosamine and N-acetylglucosamine residues. In this experiment we compared chitosan of sixteen different molecular weights after being processed through a high pressure homogenizer. Processed chitosan (420 kDa average molecular weight, 30% of acetylation) was dissolved in a 1% (v/v) acetic acid in water to a final concentration of 1% (w/v) and apparent viscosity of 183 MPa. The chitosan solution was passed through a high pressure homogenizer with 0-5 passes at pressure levels 0, 100, 200, and 300 MPa. After processing, the chitosan acetate was investigated to determine the effect on polydispersity in terms of molecular weight and the antimicrobial properties of chitosan at different molecular weights. All compounds were tested against Escherichia coli K-12 to determine antimicrobial activity. There is growing interest in the application of chitosan in food industry due to its wide range of desirable properties including being non-toxic and biodegradability. However, as a hydrophobic material, it is very challenging to work with. Though chitosan is a challenge to work my findings indicated a strong antimicrobial relationship with chitosan at 1% concentration with a molecular weight of 200 kDa and lower against E. coli. In conclusion chitosan has viable application with a variety of foods and can be used as a preservative that decrease bacterial activity below detection level’s and helps to prolong shelf-stable products.

No description available.

The incidences of diarrhoeal episodes in infants and children have mostly been associated with the consumption of contaminated weaning foods. This is especially true in developing countries where factors such as the lack of sanitation systems and electricity have been found to contribute to an increase in the incidence of microbiologically contaminated weaning foods. The process of fermentation has been found to reduce the amount of microbiological contamination in such foods as a result of the production of antimicrobial compounds such as organic acids, peroxides, carbon dioxide and bacteriocins. In this study, microbiological surveys were conducted on sorghum powder samples and their corresponding fermented and cooked fermented porridge samples collected from an informal settlement of the Gauteng Province of South Africa. The process of fermentation was found to result in significant decreases (P>0.05) in Gram-negative counts and spore counts, while aerobic plate counts decreased slightly. Lactic acid bacteria counts, however, increased significantly (P>0.05). The cooking process was found to result in further significant decreases (P>0.05) in all counts. Sorghum powder samples and fermented porridge samples were found to be contaminated with potential foodborne pathogens, including Bacillus cereus, Clostridium perfringens and Escherichia coli, however, none of the pathogens tested for were detected in any of the cooked fermented porridge samples. SDS-PAGE and phenotypic analysis of 180 lactic acid bacteria isolated from sorghum powder samples and their corresponding fermented and cooked fermented porridge samples showed that a majority of the isolates were lactobacilli and leuconostocs, however, some isolates were identified as pediococci and lactococci. These results demonstrated the heterogeneity of the lactic acid bacteria isolates that were associated with fermentation processes in this study. Of the lactic acid bacteria identified, Lactobacillus plantarum and Leuconostoc mesenteroides strains were found to have the highest distribution frequencies, being distributed in 87% and 73% of the households, respectively. Analysis of Lactobacillus plantarum (58) and Leuconostoc mesenteroides (46) strains isolated from sorghum powder samples and corresponding fermented and cooked fermented porridge samples by AFLP fingerprinting showed that they originated from a common source, which was sorghum powder. There was, however, evidence of strains that may have been introduced at household level. Antimicrobial activity of selected lactic acid bacteria was found to be mainly due to a decrease in pH in fermented and cooked fermented porridge samples. None of the lactic acid bacteria tested seemed to produce bacteriocins.

Made available in DSpace on 2014-06-11T19:27:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-25Bitstream added on 2014-06-13T19:55:47Z : No. of bitstreams: 1 silva_bl_me_botib.pdf: 198846 bytes, checksum: ff23adb2c290d1b6ce0ce5d4e1ddfa11 (MD5) / Os alimentos minimamente processados surgiram como uma interessante alternativa para o consumidor que procura por produtos de boa qualidade, saudáveis e de fácil preparo e consumo. No entanto, micro-organismos patogênicos podem estar presentes desde a produção ou serem introduzidos através de equipamentos e utensílios mal higienizados ou pela manipulação inadequada. Sendo assim, o objetivo desse trabalho foi a avaliação microbiológica de hortaliças, legumes e frutas minimamente processados, em relação aos parâmetros microbiológicos descritos na legislação brasileira, que permite até 102/g de coliformes termotolerantes para hortaliças e até 5 x 102/g, para frutas, na ausência de Salmonella em 25 gramas do produto. Entretanto, a legislação não contempla a pesquisa de Staphylococcus aureus, bactéria potencialmente produtora de enterotoxinas, cujo habitat é a mucosa nasal e que pode ser transmitida aos alimentos pela intensa manipulação. Dentro do mesmo gênero, existem as espécies de estafilococos coagulase negativa (ECN), que apresentam grande potencial patogênico, por possuírem os mesmos genes para a produção de enterotoxinas, encontrados em S. aureus. Assim, o trabalho também objetivou o isolamento dessas bactérias, a pesquisa dos genes que codificam a produção de enterotoxinas clássicas e biofilme e, a partir da presença dos genes, foi pesquisada a produção in vitro desses fatores. A produção de biofilme foi verificada em plástico, aço inoxidável e vidro. Foram analisadas 200 amostras, e nenhuma apresentou contaminação por Salmonella, mas 157 (78,5%) estavam fora dos limites aceitáveis em relação à quantidade de coliformes termotolerantes. Em relação aos estafilococos, 50 amostras (25%) apresentaram contaminação por ECN e 7 (3,5%), por estafilococos coagulase... / Minimally processed foods emerged as an interesting alternative for the consumer that seeks for products with good quality, which are healthy, easy to prepare and to consume. Nevertheless, pathogenic microorganisms may be present in these products since production, or may be introduced by badly sanitized equipment and utensils, or by improper manipulation. Therefore, the objective of this work was the microbiological evaluation of minimally processed vegetables and fruits, regarding the microbiological parameters described in the Brazilian law, which allows for up to 10² thermotolerant coliforms in vegetables and up to 5 x 10² in fruits, in the absence of Salmonella in 25 grams of the product. However, the law does not consider the research of Staphylococcus aureus, bacteria that is a potential producer of enterotoxins, whose habitat is the nasal mucosa and that may be transmitted to food by the intense manipulation they are subjected. In the same genus, there are the coagulase-negative staphylococci species (CoNS), which presents huge pathogenic potential, for having the same genes for enterotoxin production found on S. aureus. Thus, this work also aims the isolation of these bacteria, the research of genes that codify for the production of classical enterotoxins and biofilm and, as from the presence of these genes, the research of the production in vitro of enterotoxins and biofilm. The biofilm production was tested on plastic, stainless steel and glass, which are the most used materials in equipments and utensils. 200 samples were analyzed, and none presented contamination by Salmonella, although 157 (78.5%) were outside the acceptable limits regarding the quantity of thermotolerant coliforms. From these 200 samples of minimally processed products, 50 (25%) presented coagulase-negative staphylococci (CoNS) and... (Complete abstract click electronic access below)

Orientador: Vera Lúcia Mores Rall / Banca: Ary Fernandes Junior / Banca: Maria Cecília de Arruda / Resumo: Os alimentos minimamente processados surgiram como uma interessante alternativa para o consumidor que procura por produtos de boa qualidade, saudáveis e de fácil preparo e consumo. No entanto, micro-organismos patogênicos podem estar presentes desde a produção ou serem introduzidos através de equipamentos e utensílios mal higienizados ou pela manipulação inadequada. Sendo assim, o objetivo desse trabalho foi a avaliação microbiológica de hortaliças, legumes e frutas minimamente processados, em relação aos parâmetros microbiológicos descritos na legislação brasileira, que permite até 102/g de coliformes termotolerantes para hortaliças e até 5 x 102/g, para frutas, na ausência de Salmonella em 25 gramas do produto. Entretanto, a legislação não contempla a pesquisa de Staphylococcus aureus, bactéria potencialmente produtora de enterotoxinas, cujo habitat é a mucosa nasal e que pode ser transmitida aos alimentos pela intensa manipulação. Dentro do mesmo gênero, existem as espécies de estafilococos coagulase negativa (ECN), que apresentam grande potencial patogênico, por possuírem os mesmos genes para a produção de enterotoxinas, encontrados em S. aureus. Assim, o trabalho também objetivou o isolamento dessas bactérias, a pesquisa dos genes que codificam a produção de enterotoxinas clássicas e biofilme e, a partir da presença dos genes, foi pesquisada a produção in vitro desses fatores. A produção de biofilme foi verificada em plástico, aço inoxidável e vidro. Foram analisadas 200 amostras, e nenhuma apresentou contaminação por Salmonella, mas 157 (78,5%) estavam fora dos limites aceitáveis em relação à quantidade de coliformes termotolerantes. Em relação aos estafilococos, 50 amostras (25%) apresentaram contaminação por ECN e 7 (3,5%), por estafilococos coagulase... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Minimally processed foods emerged as an interesting alternative for the consumer that seeks for products with good quality, which are healthy, easy to prepare and to consume. Nevertheless, pathogenic microorganisms may be present in these products since production, or may be introduced by badly sanitized equipment and utensils, or by improper manipulation. Therefore, the objective of this work was the microbiological evaluation of minimally processed vegetables and fruits, regarding the microbiological parameters described in the Brazilian law, which allows for up to 10² thermotolerant coliforms in vegetables and up to 5 x 10² in fruits, in the absence of Salmonella in 25 grams of the product. However, the law does not consider the research of Staphylococcus aureus, bacteria that is a potential producer of enterotoxins, whose habitat is the nasal mucosa and that may be transmitted to food by the intense manipulation they are subjected. In the same genus, there are the coagulase-negative staphylococci species (CoNS), which presents huge pathogenic potential, for having the same genes for enterotoxin production found on S. aureus. Thus, this work also aims the isolation of these bacteria, the research of genes that codify for the production of classical enterotoxins and biofilm and, as from the presence of these genes, the research of the production in vitro of enterotoxins and biofilm. The biofilm production was tested on plastic, stainless steel and glass, which are the most used materials in equipments and utensils. 200 samples were analyzed, and none presented contamination by Salmonella, although 157 (78.5%) were outside the acceptable limits regarding the quantity of thermotolerant coliforms. From these 200 samples of minimally processed products, 50 (25%) presented coagulase-negative staphylococci (CoNS) and... (Complete abstract click electronic access below) / Mestre

Doctor of Philosophy / Food Science Institute / Sara E. Gragg / Justin J. Kastner / Food safety is a public health issue that demands coordinated scientific and policy solutions. Despite advancements in interventions and surveillance, Shiga toxin-producing Escherichia coli (STEC) and Salmonella spp. continue to cause outbreaks in a wide variety of food products. In light of these public health urgencies, both microbiological and policy frameworks are needed to address and anticipate future food safety challenges related to these pathogens. Laboratory-based techniques are used to address (1) whether common processing stresses change the susceptibility of STEC and Salmonella to food-grade antimicrobials, (2) whether differences in STEC attachment to beef tissue can inform intervention strategies, and (3) the efficiency of a combined sanitizer approach to reduce Salmonella on spinach. Salmonella Montevideo, Newport, and Typhimurium, and STEC O26, O45, O103, O111, O145, and O157:H7 were subjected to salt, acid, heat, freeze-thaw, alkaline and no (control) stress, and then challenged with the antimicrobials lauric arginate, citric acid plus hydrochloric acid, peroxyacetic acid plus acetic acid and hydrogen peroxide, lactic acid plus citric acid, and lactic acid. Growth/inhibition/no-growth was determined by absorbance values. While differences (p≤0.05) were observed between some of the stressors and controls, the minimum inhibitory concentrations (MICs) observed for both STEC and Salmonella were below maximum concentrations permitted by the United States Department of Agriculture (USDA). STEC serogroups were grown in nutrient-dense or nutrient-limiting media and inoculated onto lean or adipose, pre-rigor (warm) or chilled beef tissue. Loosely and firmly attached cells were plated onto MacConkey agar at several time points. When grown in nutrient-dense media, time × sample type (buffer versus homogenized sample) and sample type × tissue type (adipose versus lean) were significant (p<0.001). For nutrient-limited cells, tissue type was a significant main effect (p=0.0134). Spinach was inoculated with 5.0 log CFU/g Salmonella, dried, and submerged in a sodium bisulfate peroxyacetic acid (SBS-PAA) wash, a chlorine wash, or water for 2 min. Samples were stored for 0, 1, 3, 5, and 10 d, and populations were enumerated. When plated on xylose-lysine-tergitol 4 (XLT-4), SBS-PAA and chlorine washes achieved significant reductions (p≤0.05). When plated on XLT-4 plus tryptic soy agar (TSA) overlay, SBS-PAA was the most effective treatment, with a reduction of 1.77 log CFU/g (p<0.0001). Recognizing that microbiology studies ought to be combined with policy frameworks (and potential food safety solutions), policy analyses were performed to (1) evaluate and make recommendations about the resilience of the U.S. food system to catastrophic events and (2) thoughtfully—and innovatively—address so-called “unknown unknowns” (or disasters) and forecast future food safety vulnerabilities. The U.S. food system and its response to an intentionally-contaminated food product are analyzed through responsibilities of public, private, and third-sector actors. To address unknown unknowns and more strategically address future food safety problems, public and private actors ought to: (a) learn from the past (i.e., the German O104 outbreak), (b) target food groups of high and/or increasing consumption, (c) assess threats primarily rooted in other critical infrastructures, (d) borrow concepts and principles from meteorological forecasting, and (e) advocate multidisciplinary thinking.

Escherichia coli produtoras de toxina de Shiga (STEC) são patógenos veiculados por alimentos capazes de causar desde diarréia branda até severa e sanguinolenta e evoluir para complicações graves como colite hemorrágica, síndrome hemolítica urêmica e púrpura trombótica trombocitopênica. Esses microrganismos têm sido associados a numerosos surtos e vários casos esporádicos de infecções em todo o mundo devido ao consumo de alimentos contaminados. O sorogrupo O157 desse grupo de microrganismos é considerado o principal devido ao seu envolvimento em surtos de doença por STEC, entretanto, muitos casos vêm ocorrendo em todo o mundo devido a cepas patogênicas de STEC não-O157, como O26, O103, O111 e O145. Os objetivos do presente trabalho foram avaliar a ocorrência de STEC em três pontos da linha de abate de bovinos destinados à exportação e em cortes refrigerados de aves e de bovinos comercializados na região da Grande São Paulo; pesquisar a presença dos fatores de virulência dos isolados através dos genes stx1, stx2, eaeA e ehxA; identificar isolados de E. coli O157:H7 pela pesquisa dos genes uidA, rfbO157 e flicH7; verificar a citotoxicidade em células Vero; pesquisar a atividade enterohemolítica dos isolados; avaliar o perfil de suscetibilidade a antimicrobianos; identificar os sorotipos e avaliar a diversidade genética dos isolados de STEC obtidos. Na linha de abate, 201 animais foram amostrados, obtendo-se 603 amostras que compreenderam 201 amostras provenientes do couro, 201 de carcaça e 201 de meia carcaça. No varejo, foram analisadas 100 amostras de cortes de carne bovina e 100 de cortes de frango. A metodologia utilizada para detecção de E. coli sorogrupo O157 foi a preconizada pela ISO 16654, enquanto para os sorogrupos O26, O103, O111 e O145 foi empregada a metodologia descrita pelo \"Surveillance Group for Diseases and Infections of Animals\" (NRM 006). Os isolados obtidos foram confirmados como STEC pela técnica de PCR. Dos 201 animais amostrados, dois (1,0%) foram positivos para STEC, obtendo-se sete isolados (três do animal número 399 e quatro do animal 401) do couro. Não houve o isolamento do microrganismo nas amostras de carcaça e meia carcaça. Os sete isolados apresentaram o perfil stx2, uidA, eaeA, ehxA, rfbO157 e fliCH7 podendo, assim, ser considerados E. coli enterohemorrágica (EHEC) pertencentes ao sorotipo O157:H7. Na avaliação da atividade enterohemolítica, nenhum dos isolados expressou essa proteína e, com relação ao teste de suscetibilidade antimicrobiana, três (42,8%) isolados apresentaram resistência ao ácido nalidíxico e um (14,3%) ao cloranfenicol. O PFGE revelou que as sete cepas de STEC isoladas apresentaram dois perfis genéticos distintos, com similaridade entre eles de 75,3%. STEC não foi detectada nas amostras de carne bovina e de aves comercializadas no varejo. Estes resultados sugerem que, apesar de presente no couro dos animais, o emprego de medidas sanitárias eficientes ao longo da cadeia de produção da carne bovina até sua comercialização na forma de corte, contribui para que o isolamento de STEC nas etapas posteriores seja raro. / Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that can cause since mild or severe and bloody diarrhea to serious complications, such as hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. These microorganisms have been associated with numerous outbreaks and several sporadic cases worldwide due to consumption of contaminated food, especially meat. E. coli O157 is considered the main serogroup involved in disease outbreaks of STEC, however, many cases have been occurred worldwide due to non-O157, such as O26, O103, O111 and O145 strains. The aims of the present study were to determine the occurrence of STEC at three points of cattle slaughter for exporting and in refrigerated beef and poultry cuts commercialized in the Metropolitan area of Sao Paulo, Brazil; identify the genes that code for the virulence factors stx1, stx2, eaeA and ehxA; detect E. coli O157:H7 strains using uidA, rfbO157 and flicH7 genes; verify the citotoxicity in Vero cells and the enterohemolytic activity; evaluate the antimicrobial susceptibility profile; identify the STEC serotypes and evaluate the genetic diversity of STEC isolates. A total of 603 samples were collected from 201 animals at slaughter. The samples were taken from hide (201), carcass (201) and half-carcass (201) and were always collected from the breast region. At retail, 100 refrigerated beef cuts and 100 chicken cuts were analyzed. The detection of E. coli O157 samples were conducted according to the ISO methodology (16654) and for detection of O26, O103, O111 e O145 serogroups the Surveillance Group for Diseases and Infections of Animals methodology (NRM 006) was used. The isolates were confirmed as STEC by PCR technique. Among 201 animals sampled, two (1,0%) were positive for STEC, obtaining seven isolates from hide (three from animal number 399 and four from animal number 401). The microrganism was not detect in carcass and half carcass samples. The seven isolates carried stx2, uidA, eaeA, ehxA, rfbO157 and fliCH7 genes, so, they can be considered as enterohaemorrhagic E. coli (EHEC) O157:H7 serotype. None of the isolates produced the enterohemolytic activity and three (42,8%) isolates showed resistence to nalidixic acid and one (14,3%) to chloramphenicol. PFGE revealed that the seven STEC strains showed two distinct genetic profiles, with 75.3% of similarity between them. STEC was not detected from beef and poultry cuts commercialized at retail. These results suggest that, although present in animals hides, the STEC isolation at later stages of food chain was rare, probably due to effective sanitary measures to control contamination and transmission of this pathogen along the beef production chain until commercialization.

Antimicrobial optimization procedures use the most resistant bacterial culture that could be present in the food to determine the levels of treatment needed to ensure safety. These procedures usually only focus on one method of preparing these inoculums for testing despite prior research showing that the preparation of the culture can influence how the culture reacts to a treatment. In this work, planktonic cells grown in a liquid media and sessile cells grown on a similar solid media were subjected to identical emulsion based antimicrobial systems. The cultures were monitored over time and their numbers periodically enumerated. Weibullian destruction models were used to characterize bacterial death and the different inoculum preparations were separated using ANOVA statistical tests. Using these models highly significant differences between the different sessile and planktonic methods of growth were found. This difference was also found to not be related to the production of curli used in biofilm formation. These results suggest that the methods of inoculum preparation can be a significant factor in bacterial survival, a factor that should be included in food antimicrobial optimization procedures.