Occurrence, genetic characterization, and antibiotic susceptibility of Cronobacter spp. isolated from low water activity functional foods in Brazil.

Cronobacter spp. are bacterial pathogens isolated from a wide variety of foods. This study aims at evaluating the occurrence of Cronobacter spp. in low water activity functional food samples, detect the presence of virulence genes, and determine the antibiotic susceptibility of strains. From 105 samples, 38 (36.2%) were contaminated with Cronobacter spp. The species identified by polymerase chain reaction (PCR) and sequencing analyses (rpoB and fusA genes, respectively) were C. sakazakii (60.3%), C. dublinensis (25.4%), C. turincensis (9.5%), and C. malonaticus (4.8%). Nineteen fusA alleles were identified, including four new alleles. The virulence genes were identified by PCR and all isolates were positive for ompX and sodA genes, 60.3% to cpa gene, and 58.7% to hly gene. Using the disk diffusion method, antibiotic susceptibility to twelve antibiotics was assessed twice, separated by a 19-month period. In the first test, the isolates showed diverse antibiotic susceptibility profiles, with nineteen isolates (30.2%) being multi-drug resistant (resistant to three or more antibiotic classes), in the second, the isolates were susceptible to all antibiotics. Cronobacter spp. in functional foods demonstrates the need for continued investigation of this pathogen in foods, and further research is needed to clarify the loss of resistance of Cronobacter strains.

Aeromonas spp. in drinking water and food: Occurrence, virulence potential and antimicrobial resistance.

Aeromonas sp. is a Gram-negative, non-spore-forming, rod-shaped, oxidase-positive, facultative anaerobic bacterium and a natural contaminant found in aquatic environments. Some species can invade, colonize, and damage host cells due to the presence of virulence factors, such as flagella, elastase, hemolysins, aerolysins, adhesins, enterotoxins, phospholipases and lipases, that lead to pathogenic activities. Consequently, can cause many health disorders that range from gastrointestinal problems, enteric infections, and ulcers to hemorrhagic septicemia. Aeromonas has been isolated and identified from a variety of sources, including drinking water and ready-to-eat foods (fish, meat, fresh vegetables, dairy products, and others). Some species of this opportunistic pathogen are resistant to several commercial antibiotics, including some used as a last resort for treatment, which represents a major challenge in the clinical segment. Antimicrobial resistance can be attributed to the indiscriminate use of antibiotics by society in aquaculture and horticulture. In addition, antibiotic resistance is attributed to plasmid transfer between microorganisms and horizontal gene transfer. This review aimed to (i) verify the occurrence of Aeromonas species in water and food intended for human consumption; (ii) identify the methods used to detect Aeromonas species; (iii) report on the virulence genes carried by different species; and (iv) report on the antimicrobial resistance of this genus in the last 5 years of research. Additionally, we present the existence of Aeromonas spp. resistant to antimicrobials in food and drinking water represents a potential threat to public health.

Incidence, evaluation of detection and identification methods, and antimicrobial resistance of Aeromonas spp. in ready-to-eat foods.

Aeromonas spp. are opportunistic and ubiquitous bacteria considered emerging pathogens that can cause infections in animals, especially fish, as well as humans. In humans, these bacteria are associated with gastroenteritis but can also be related to extraintestinal diseases. Its main infection route is through water, but it has been increasingly associated with foods. Their association with ready-to-eat foods may be a concern, especially because these products are for immediate consumption. This study aimed to investigate the prevalence of Aeromonas spp. in ready-to-eat foods (temakis, cheeses and minimally processed fruits) and to characterize the virulence profile and antimicrobial resistance of the isolates. The species A. hydrophila, A. caviae and A. veronii were identified using polymerase chain reaction (PCR), which was later compared with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). The performance of two isolation selective agars (starch-ampicillin agar-SAA and Aeromonas agar-AA) was also evaluated. Aeromonas spp. was isolated in 66.67 % (20/30) of temaki, 3.23 % (1/31) of fruits and none (0/30) of cheeses, observing high microorganism counts from <102 to 2.6 × 105 CFU/g. A. caviae (26.39 %) was the most prevalent species, followed by A. hydrophila (20.83 %) and A. veronii (8.34 %), and 44.44 % were classified as Aeromonas sp. The performance analysis between PCR and MALDI-TOF/MS for Aeromonas identification was not statistically significant, and the Kappa index showed moderate agreement (p < 0.01 and Kappa = 0.718). The SAA selective medium performed better than AA. We identified seventeen virulence profiles, and 59.72 % of the isolates had some of the genes studied. The aerA gene (47.2 %) was the most abundant, followed by act (41.7 %), hlyA and alt (38.9 %), and ast (18.1 %). A. hydrophila was the species most associated with these genes. The antimicrobial susceptibility test showed that 90 % of the isolates were resistant to amoxicillin-clavulanic acid, 17 % to tetracycline, 10 % to imipenem and 3 % to aztreonam. The results showed that temakis are carriers of potentially pathogenic Aeromonas spp. and therefore should be avoided by children, elderly individuals, pregnant women, and immunocompromised people. We also found strains resistant to antimicrobials, meaning that these microorganisms need constant monitoring.

Cronobacter spp. in foods of plant origin: occurrence, contamination routes, and pathogenic potential.

Cronobacter is an emerging bacterial pathogen associated with infections such as necrotizing enterocolitis, sepsis, and meningitis in neonates and infants, related to the consumption of powdered infant formula. In addition, this bacterium can also cause infections in adults by the ingestion of other foods. Thus, this review article aims to report the occurrence and prevalence of Cronobacter spp. in foods of plant origin, as well as the possible sources and routes of contamination in these products, and the presence of pathogenic strains in these foods. Cronobacter was present in a wide variety of cereal-based foods, vegetables, herbs, spices, ready-to-eat foods, and foods from other categories. This pathogen was also found in cultivation environments, such as soils, compost, animal feces, rice and vegetable crops, as well as food processing industries, and domestic environments, thus demonstrating possible contamination routes. Furthermore, sequence types (ST) involved in clinical cases and isolates resistant to antibiotics were found in Cronobacter strains isolated from food of plant origin. The identification of Cronobacter spp. in plant-based foods is of great importance to better elucidate the vehicles and routes of contamination in the primary production chain and processing facility, until the final consumption of the food, to prevent infections.

Virulence and DNA sequence analysis of Cronobacter spp. isolated from infant cereals.

Cronobacter spp. is an opportunistic pathogen that causes severe infections, affecting newborns and infants, and is also an emerging cause of hospital-acquired infection in elderly populations. These infections are mainly associated with the consumption of infant formulas, even though these bacteria have been isolated from other foods as well. Cronobacter spp. invades epithelial cells and escapes the immune response mechanisms, multiplying inside macrophages. However, the pathogenesis and virulence factors of these bacteria have not been fully elucidated and need to be further studied. Therefore, this study aimed to evaluate the ability of Cronobacter spp. strains isolated from infant cereals to invade and survive within macrophages, investigate the virulence phenotype using the Galleria mellonella model, and identify possible genes involved in bacterial pathogenesis through pan-genome analysis. All the isolates were able to invade macrophages and the survival of bacteria decreased over a 72 h period, with bacterial cell counts reaching up to 106 CFU/ml. Cronobacter sakazakii isolate 112 exhibited a similar mortality rate (40-70%) to the ATCC BAA 894 strain (Cronobacter sakazakii) in G. mellonella assay. In addition, some unique virulence genes (isolate 7, ada_2, tcmA_1, acrB_3; isolate 78, ampC_2, rihC_1 and isolate 112, fimH, ylpA, gtrA) were identified within isolates with the invasive profile in the in vivo and in vitro assays. Furthermore, isolates from different species were grouped into seven distinct clusters in the pan-genome analysis. The most virulent isolates (7, 78, and 112) were grouped in distinct subclusters in the cladogram. This work revealed potential Cronobacter spp. pathogenic strains recovered from infant cereals.

Detection and pathogenic potential of Clostridium difficile in commercial meat and meat products in Brazil.

The aims of this study were to evaluate the occurrence of Clostridium difficile in commercial raw meat and meat products commercialized in Brazil, and to determine the pathogenic potential and antimicrobial susceptibility of the isolates. After selective enrichment, the isolation of C. difficile involved plating with and without an alcohol shock treatment onto C. difficile moxalactam agar (CDMNA). The toxigenic profile was determined through PCR for detection of tcdA, tcdB, cdtA and cdtB genes and an enzyme-linked immunosorbent assay for toxin A/B. C. difficile was isolated from 8.9% (17 out of 192) of analyzed samples. Plating without alcohol treatment (sensitivity of 88.23%) was more efficient than with alcohol treatment (sensitivity of 29.41%) in C. difficile isolation. The profile A + B+CDT- was observed in 35.0% (28/80) of the isolates. The A/B toxin was tested in 44 isolates and 15.9% of them were positive. Resistance to clindamycin, ceftizoxime tetracycline, metronidazole, vancomycin, and ceftriaxone were observed among isolates. Multi-drug resistance was detected in 36.4% (8/22) of the isolates evaluated.

Incidence of Bacillus cereus, Bacillus sporothermodurans and Geobacillus stearothermophilus in ultra-high temperature milk and biofilm formation capacity of isolates.

The presence of mesophilic and thermophilic spore-forming bacteria in UHT milk, as well as biofilm formation in dairy plants, are concerning. The current study explored the spore-forming bacilli diversity in 100 samples of UHT milk (skimmed and whole). Through this work, a total of 239 isolates from UHT milk samples were obtained. B. cereus s.s. was isolated from 7 samples, B. sporothermodurans from 19 and, G. stearothermophilus from 25 samples. Genes encoding hemolysin (HBL), and non-hemolytic (NHE) enterotoxins were detected in B. cereus s.s. isolates. All isolates of B. cereus s.s. (12) B. sporothermodurans (38), and G. stearothermophilus (47) were selected to verify the ability of biofilm formation in microtiter plates. The results showed all isolates could form biofilms. The OD595 values of biofilm formation varied between 0.14 and 1.04 for B. cereus, 0.20 to 1.87 for B. sporothermodurans, and 0.49 to 2.77 for G. stearothermophilus. The data highlights that the dairy industry needs to reinforce control in the initial quality of the raw material and in CIP cleaning procedures; avoiding biofilm formation and consequently a persistent microbiota in processing plants, which can shelter pathogenic species such as B. cereus s.s.

Isolation, comparison of identification methods and antibiotic resistance of Cronobacter spp. in infant foods.

Cronobacter spp. are opportunistic pathogens that cause serious infections, especially in infants, elderly, and immunocompromised people. Dehydrated infant foods are the main vehicle associated with infections caused by these bacteria. Thus, this study aims to investigate the occurrence of Cronobacter spp. in 152 commercial samples of dehydrated infant formulas (77 samples) and dehydrated infant cereals (75 samples), as well as characterize the isolates. Polymerase Chain Reaction (PCR) and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF/MS) methods for isolate identification were used, and their results compared. Furthermore, the susceptibility to 11 antibiotics was tested, and DNA sequencing of one isolate with multi-drug resistance was analyzed. No contamination in the infant formula samples was found, whereas 17.33% (13/75) of the infant cereal samples presented contamination with Cronobacter sakazakii. The identification results by PCR and MALDI-TOF/MS were divergent for some isolates. The antimicrobial resistance results showed a high incidence of resistance to cefazolin (94.4%) besides resistance to amoxicillin (9.45%), cefpodoxime (5.55%), streptomycin (1.35%), and trimethoprim/sulfamethoxazole (1.35%). Whole genome sequencing of one multi-drug resistant isolate showed six genes associated with antimicrobial resistance and an 82% possibility of being a human pathogen based on the presence of virulence factors. The presence of Cronobacter spp. in infant foods represents a risk for the infant's health. Moreover, the presence of a pathogenic multi-drug resistant isolate in infant's food reinforces the necessity of improving food safety policies to protect young children.

Competitive and/or Cooperative Interactions of Listeria monocytogenes With Bacillus cereus in Dual-Species Biofilm Formation.

Microorganisms in dairy industries can form monospecies, dual-species, or multispecies biofilms, showing cooperative or competitive behaviors, which might contribute to the reduction of efficiency of cleaning and sanitization processes and eventually turn into a potential source of contamination. This study proposes to evaluate the behavior of Listeria monocytogenes in monospecies biofilms, cocultured with Bacillus cereus. The isolates were of dairy origin, and the selection occurred after studies of competition among species. The biofilm formations on AISI 304 stainless steel at 25°C in a stationary culture were analyzed to observe the cooperative or competitive interactions among species, as well as the effect of pre-adhered cells. Biofilm formation assays were performed in four experiments: Experiment 1: in the presence of strains of antagonistic substance producer B. cereus (+); Experiment 2: extract of the antagonistic substance of B. cereus; Experiment 3: pre-adhered cells of B. cereus; and Experiment 4: pre-adhered cells of L. monocytogenes. Subsequently, cooperative behavior was observed by scanning electron microscopy. The L. monocytogenes monospecies biofilm counts of greater than 5 log colony-forming units (CFU)/cm2 were also observed in dual-species biofilms in the presence of B. cereus (non-producers of antagonist substance), showing cooperative behavior between species. However, in the presence of antagonistic substance produced by B. cereus, the counts were lower, 1.39 and 1.70 log CFU/cm2 (p > 0.05), indicating that the antagonistic substance contributes to competitive interactions. These data are relevant for the development of new studies to control L. monocytogenes in the dairy industry.

Avaliação microscópica de superfícies de aço inoxidável usados em ensaios de biofilmes / Microscopic evaluation on stainless steel surfaces used in biofilm assays

Superfícies de aço inoxidável com especificações determinadas pela American Society for Testing and Materials (ASTM) são usadas em testes in vitro para simular a formação e a remoção de biofilmes. Muitas vezes estas superfícies são reutilizadas nos ensaios de formação de biofilmes. O objetivo deste trabalho foi avaliar se cupons de aço inoxidável anteriormente utilizados para formação de biofilmes multiespécies podem ser reutilizados em novos ensaios. Assim, cupons submetidos a diferentes procedimentos de higienização foram analisados por microscopia eletrônica de varredura (MEV) e perfilometria . A reutilização das superfícies em novos experimentos deve ser realizada com cautela, aplicando procedimentos que removam as células bacterianas e a substância polimérica extracelular (EPS) aderidas na superfície. Além disso, observações da superfície (topografia e rugosidade) devem ser avaliadas, comprovando as especificações da ASTM.

Bacillus cereus e Geobacillus stearothermophilus em leite ultra alta temperatura (UAT) / Bacillus cereus and Geobacillus steartothermophilusin ultra high temperature (UHT) milk

O objetivo deste trabalho foi avaliar a presença de B. cereus e G. stearothermophilus em 100 amostras de leite UAT (integral e desnatado). O isolamento dos esporos e das células vegetativas seguiu metodologias oficiais, com pequenas modificações. B. cereus foi isolada de 7% amostras de leite UHT, de 6 diferentes marcas. As contagens máximas de células vegetativas e esporos de B. cer eus foram de 3,54 Log UFC/mL e 3,93 Log esporos/mL, respectivamente. A presença dos genes codificadores de enterotoxina não hemolítica (NHE) foi observada em 33% dos isolados e da hemolisina (HBL ) em 100% dos isolados. O gene hblA foi encontrado em 91,6 % dos isolados, porém nenhum isolado apresentou os 3 genes do complexo HBL. G. stearothermophilus foi identificada em 22,8% (34/149) dos isolados de esporo altamente resistente ao calor (HRRS), representando 18% das amostras de leite UAT e as contagens de esporos variaram de < 1Log a 3,40 Log esporos/mL.

Caracterização fenotípica e genotípica de Enterococcus spp. isolados de ambiente de processamento de queijo Minas Frescal / Phenotypic and genotypic characterization of Enterococcus spp. isolated from Minas Frescal cheese processing line

O objetivo deste trabalho foi identificar as fontes de contaminação de Enterococcus spp. em uma linha de processamento de queijo Minas Frescal e caracterizar estes micro-organismos quanto à capacidade proteolítica e lipolítica bem como quanto as características de patogenicidade. A partir dos resultados, pode-se verificar que os Enterococcus spp. estavam presentes em amostras de matéria-prima, ambiente e produto final, com destaque para o equipamento de ordenha que apresentou a maior contagem de Enterococcus spp. (5 log UFC/cm2) e a maçaneta que apresentou contaminação persistente ao longo das coletas. Aproximadamente 47% dos isolados apresentaram atividade proteolítica e lipolítica. Além disso, os isolados testados apresentaram resistência múltipla a antibióticos e possuíram múltiplos genes de virulência.

Modelagem da formação de biofilmes de Pseudomonas fluorescens e Pseudomonas aeruginosa em aço inoxidável através da metodologia de superfície de resposta / Modeling Pseudomonas luorescens and Pseudomonas aeruginosa biofilm formation on stainless steel by response surface methodology

O objetivo deste trabalho foi verificar a influência do tempo e da temperatura na formação de biofilmes de P. fluorescens e P. aeruginosa em superfície de aço inoxidável através de um delineamento composto central rotacional (DCCR). Os biofilmes foram avaliados nas temperaturas de 7; 13; 27; 41 e 47 °C e nos tempos de contato de 0; 1,2; 4; 6,8 e 8 dias. As superfícies de resposta mostraram que P. fluorescens foi capaz de formar biofilme entre 0,9 e 8 dias em temperaturas entre 9,8 e 47 °C. P. aeruginosa foi capaz de formar biofilme entre0,7 a 8 dias e entre 11 e 47 °C. É importante destacar que estas condições são frequentemente encontradas durante todo o processamento de queijo Minas frescal, comprometendo a segurança do alimento.

Quorum sensing in Enterococcus faecium, Enterococcus faecalis and Bacillus cereus strains isolated from ricotta processing / Quorum sensing em cepas de Enterococcus faecium, Enterococcus faecalis e Bacillus cereus isoladas do processamento de ricota

ABSTRACT: The quorum sensing phenomenon is a process of intra- and inter-species microbial communication involving the production and detection of extracellular signaling molecules. The autoinducer AI-2 has been proposed to serve as a 'universal signal' for interspecies communication. This study aimed to evaluate the capability of Enterococcus faecium, Enterococcus faecalis, and Bacillus cereus strains isolated from ricotta processing to produce quorum sensing signalling molecules (AI-2). The strains were evaluated for the presence of the luxS gene using the polymerase chain reaction. AI-2 quorum sensing signalling molecules were measured in relative light units (RLUs) using a luminometer. A total of 74% of E. faecium, 91% of E. faecalis, and 95% of B. cereus isolates were positive for luxS gene. In addition, the induced bioluminescence in Vibrio harveyi BB170 was observed in all strains, indicating the presence of the AI-2 autoinducer.

RESUMO: O fenômeno quorum sensing corresponde a um processo de comunicação intra e interespécies microbianas e é mediado por sinais químicos extracelulares, denominados moléculas sinalizadoras ou auto indutoras (AI). A molécula AI2 está envolvida na comunicação interespécies, denominada sistema "universal" de comunicação. Este estudo teve como objetivo avaliar a capacidade de Enterococcus faecium, Enterococcus faecalis e Bacillus cereus isolados do processamento de ricota em produzir moléculas sinalizadoras de Quorum sensing (AI-2). Os isolados foram avaliados quanto à presença do gene luxS utilizando a reação em cadeia da polimerase (PCR). As moléculas sinalizadoras (AI-2) foram medidas em unidades relativas de luz (RLU) através de um luminômetro. Um total de 74% dos isolados de E. faecium, 91% de E. faecalis e 95% de B. cereus foram positivos para o gene luxS. Além disso, todos os isolados apresentaram capacidade de induzir o fenômeno de bioluminescência em Vibrio harveyi BB170, indicando a presença de auto indutores AI-2.

Dissemination of Enterococcus faecalis and Enterococcus faecium in a ricotta processing plant and evaluation of pathogenic and antibiotic resistance profiles.

In this work, the sources of contamination by Enterococcus spp. in a ricotta processing line were evaluated. The isolated strains were tested for virulence genes (gelE, cylA,B, M, esp, agg, ace, efaA, vanB), expression of virulence factors (hemolysin and gelatinase), and the resistance to 10 different antibiotics. Enterococcus faecium and Enterococcus faecalis were subjected to discriminatory identification by intergenic spacer region (ITS)-polymerase chain reaction and sequencing of the ITS region. The results showed that Enterococcus spp. was detected in the raw materials, environment samples and the final product. None of the 107 Enterococcus isolates were completely free from all virulence genes considered. A fraction of 21.5% of the isolates containing all of the genes of the cylA, B, M operon also expressed ß-hemolysis. Most of the isolates showed the gelE gene, but only 9.3% were able to hydrolyze gelatin. In addition, 23.5% of the observed Enterococcus isolates had the vanB gene but were susceptible to vancomycin in vitro. The dissemination of antibiotic-resistant enterococci was revealed in this study: 19.3% of the E. faecium samples and 78.0% of the E. faecalis samples were resistant to at least one of the antibiotics tested. Sequencing of region discriminated 5 and 7 distinct groups among E. faecalis and E. faecium, respectively. Although some similarity was observed among some of the isolates, all E. faecalis and E. faecium isolates had genetic differences both in the ITS region and in the virulence profile, which makes them different from each other.

Behavior of Listeria monocytogenes in a multi-species biofilm with Enterococcus faecalis and Enterococcus faecium and control through sanitation procedures.

The formation of mono-species biofilm (Listeria monocytogenes) and multi-species biofilms (Enterococcus faecium, Enterococcus faecalis, and L. monocytogenes) was evaluated. In addition, the effectiveness of sanitation procedures for the control of the multi-species biofilm also was evaluated. The biofilms were grown on stainless steel coupons at various incubation temperatures (7, 25 and 39°C) and contact times (0, 1, 2, 4, 6 and 8 days). In all tests, at 7°C, the microbial counts were below 0.4 log CFU/cm(2) and not characteristic of biofilms. In mono-species biofilm, the counts of L. monocytogenes after 8 days of contact were 4.1 and 2.8 log CFU/cm(2) at 25 and 39°C, respectively. In the multi-species biofilms, Enterococcus spp. were present at counts of 8 log CFU/cm(2) at 25 and 39°C after 8 days of contact. However, the L. monocytogenes in multi-species biofilms was significantly affected by the presence of Enterococcus spp. and by temperature. At 25°C, the growth of L. monocytogenes biofilms was favored in multi-species cultures, with counts above 6 log CFU/cm(2) after 8 days of contact. In contrast, at 39°C, a negative effect was observed for L. monocytogenes biofilm growth in mixed cultures, with a significant reduction in counts over time and values below 0.4 log CFU/cm(2) starting at day 4. Anionic tensioactive cleaning complemented with another procedure (acid cleaning, disinfection or acid cleaning+disinfection) eliminated the multi-species biofilms under all conditions tested (counts of all micro-organisms<0.4 log CFU/cm(2)). Peracetic acid was the most effective disinfectant, eliminating the multi-species biofilms under all tested conditions (counts of the all microorganisms <0.4 log CFU/cm(2)). In contrast, biguanide was the least effective disinfectant, failing to eliminate biofilms under all the test conditions.

Biofilms of Enterococcus faecalis and Enterococcus faecium isolated from the processing of ricotta and the control of these pathogens through cleaning and sanitization procedures.

The biofilm formation of Enterococcus faecalis and Enterococcus faecium isolated from the processing of ricotta on stainless steel coupons was evaluated, and the effect of cleaning and sanitization procedures in the control of these biofilms was determined. The formation of biofilms was observed while varying the incubation temperature (7, 25 and 39°C) and time (0, 1, 2, 4, 6 and 8 days). At 7°C, the counts of E. faecalis and E. faecium were below 2 log10 CFU/cm(2). For the temperatures of 25 and 39°C, after 1 day, the counts of E. faecalis and E. faecium were 5.75 and 6.07 log10 CFU/cm(2), respectively, which is characteristic of biofilm formation. The tested sanitation procedures a) acid-anionic tensioactive cleaning, b) anionic tensioactive cleaning+sanitizer and c) acid-anionic tensioactive cleaning+sanitizer were effective in removing the biofilms, reducing the counts to levels below 0.4 log10 CFU/cm(2). The sanitizer biguanide was the least effective, and peracetic acid was the most effective. These studies revealed the ability of enterococci to form biofilms and the importance of the cleaning step and the type of sanitizer used in sanitation processes for the effective removal of biofilms.

Growth of enterotoxin producing Bacillus cereus in meat substrate at 10 ºC and 30 ºC

The behaviour of enterotoxin-producing Bacillus cereus in meat was investigated by inoculating spore suspensions of five cultures into meat substrate (pH 5.8) and incubating at 10ºC and 30ºC. The bacterial populations were evaluated after different times by plate counts in nutrient agar. All the cultures presented growth at 30ºC with the generation time varying from 28.8 to 36.0 minutes. Three cultures also presented growth at 10ºC with generation times between 10.16 and 28.38 h. Considering the results, it was concluded that meat kept at abusive temperatures would be subject to development of this microorganism.

Growth of enterotoxin producing Bacillus cereus in meat substrate at 10ºC and 30ºC.

The behaviour of enterotoxin-producing Bacillus cereus in meat was investigated by inoculating spore suspensions of five cultures into meat substrate (pH 5.8) and incubating at 10ºC and 30ºC. The bacterial populations were evaluated after different times by plate counts in nutrient agar. All the cultures presented growth at 30ºC with the generation time varying from 28.8 to 36.0 minutes. Three cultures also presented growth at 10ºC with generation times between 10.16 and 28.38 h. Considering the results, it was concluded that meat kept at abusive temperatures would be subject to development of this microorganism.

Qualidade microbiológica de ricotas comerciais e os riscos associados à presença de Listeria monocytogenes / Microbiological quality of marketed ricotta cheese and disease risks associated with Listeria monocytogenes contamination

No presente estudo foi avaliada a qualidade microbiológica de ricotas comercializadas na região de Campinas-SP e caracterizado o potencial patogênico das cepas isoladas de Listeria monocytogenes. Um total de 45 amostras de ricota foi submetido às análises de contagens de coliformes termotolerantes, estafilococos coagulase positiva, bolores, leveduras e detecção de Salmonella sp. e Listeria monocytogenes. Os resultados apontaram que 46,7 por cento (21/45) das ricotas estavam em desacordo com os padrões microbiológicos para alimentos estabelecidos pela Diretoria Colegiada da Agência Nacional de Vigilância Sanitária – Resolução RDC 12/2001. O número de amostras que apresentaram contagens acima das permitidas pela legislação em relação aos coliformes termotolerantes foi de 46,7 por cento e em relação a estafilococos coagulase positiva foi de 2,2 por cento, além de 6,7 por cento das amostras apresentaram Listeria monocytogenes. Não foi isolada Salmonella das amostras analisadas. Destaca-se a presença de L. monocytogenes em 6,7 por cento (3/45) das amostras com perfilgenético actA tipo 4 e hly tipo 1 e pertencente à linhagem I, potencialmente patogênico ao homem. Este estudo indica que o produto analisado merece maior atenção por parte da comunidade científica, bem como pelo setor produtivo e órgãos de vigilância sanitária com o intuito de empreender a melhoria da qualidade e consequente, segurança ao consumidor.