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1.
Wei Sheng Yan Jiu ; 49(4): 608-612, 2020 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-32928356

RESUMO

OBJECTIVE: To understand the contamination status of Staphylococcus aureus in food and processing. METHODS: From July 2017 to January 2018, raw/cooked meat products, aquatic products, soybean products and other foods for sale were collected from five districts and counties of Chengdu, and some processing samples were collected from school cantons, farms and slaughterhouses of Chengdu. Staphylococcus aureus in food and processing in Chengdu was detected by plate method and PCR method, staphylococcus aureus enterotoxin was determined by enzyme-linked fluorescence immunoassay, and Risk Ranger software was used for semi-quantitative Risk assessment. RESULTS: A total of 429 samples were collected from food and processing in Chengdu. 78 strains(18. 2%) of Staphylococcus aureus were detected by plate method, among which 76 strains were identified as Staphylococcus aureus by PCR. The highest detection rate was found in raw meat(34. 1%), and the highest detection rate was found in raw chicken(54. 2%). The detection rate of Staphylococcus aureus in samples from farmers' markets(34. 0%) was higher than that of supermarkets(28. 3%). Eighteen of the 78 strains produced enterotoxin, raw chicken and duck meat from supermarkets(9) and farmers' markets(6), and hand smears by school cafeteria workers(2). According to the risk score, the food safety risks are in descending order from raw meat products(55 points), soybean products(50 points), cooked meat products(43 points) and aquatic products(43 points). CONCLUSION: Raw meat and soybean products are high risk foods contaminated by S. aureus, cooked meat and aquatic products are medium risk foods.


Assuntos
Infecções Estafilocócicas , Staphylococcus aureus , Animais , Enterotoxinas , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Humanos , Carne
2.
Anal Chem ; 92(19): 13396-13404, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32867467

RESUMO

Rapid, accurate, reliable, and risk-free tracking of pathogenic microorganisms at the single-cell level is critical to achieve efficient source control and prevent outbreaks of microbial infectious diseases. For the first time, we report a promising approach for integrating the concepts of a remarkably large Stokes shift and dual-recognition into a single matrix to develop a pathogenic microorganism stimuli-responsive ratiometric fluorescent nanoprobe with speed, cost efficiency, stability, ultrahigh specificity, and sensitivity. As a proof-of-concept, we selected the Gram-positive bacterium Staphylococcus aureus (S. aureus) as the target analyte model, which easily bound to its recognition aptamer and the broad-spectrum glycopeptide antibiotic vancomycin (Van). To improve the specificity and short sample-to-answer time, we employed classic noncovalent π-π stacking interactions as a driving force to trigger the binding of Van and aptamer dual-functionalized near-infrared (NIR) fluorescent Apt-Van-QDs to the surface of an unreported blue fluorescent π-rich electronic carbon nanoparticles (CNPs), achieving S. aureus stimuli-responsive ratiometric nanoprobe Apt-Van-QDs@CNPs. In the assembly of Apt-Van-QDs@CNPs, the blue CNPs (energy donor) and NIR Apt-Van-QDs (energy acceptor) became close to allow the fluorescence resonance energy transfer (FRET) process, leading to a remarkable blue fluorescence quenching for the CNPs at ∼465 nm and a clear NIR fluorescence enhancement for Apt-Van-QDs at ∼725 nm. In the presence of S. aureus, the FRET process from CNPs to Apt-Van-QDs was disrupted, causing the nanoprobe Apt-Van-QDs@CNPs to display a ratiometric fluorescent response to S. aureus, which exhibited a large Stokes shift of ∼260 nm and rapid sample-to-answer detection time (∼30.0 min). As expected, the nanoprobe Apt-Van-QDs@CNPs showed an ultrahigh specificity for ratiometric fluorescence detection of S. aureus with a good detection limit of 1.0 CFU/mL, allowing the assay at single-cell level. Moreover, we also carried out the precise analysis of S. aureus in actual samples with acceptable results. We believe that this work offers new insight into the rational design of efficient ratiometric nanoprobes for rapid on-site accurate screening of pathogenic microorganisms at the single-cell level in the early stages, especially during the worldwide spread of COVID-19 today.


Assuntos
Bactérias/química , Infecções Bacterianas/diagnóstico , Infecções Bacterianas/microbiologia , Técnicas Biossensoriais/métodos , Corantes Fluorescentes/síntese química , Nanotecnologia/métodos , Antibacterianos/farmacologia , Aptâmeros de Nucleotídeos , Infecções por Coronavirus/complicações , Infecções por Coronavirus/microbiologia , Fluorescência , Transferência Ressonante de Energia de Fluorescência , Microbiologia de Alimentos/métodos , Humanos , Nanopartículas , Pandemias , Pneumonia Viral/complicações , Pneumonia Viral/microbiologia , Sensibilidade e Especificidade , Espectroscopia de Luz Próxima ao Infravermelho , Infecções Estafilocócicas/diagnóstico , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/química , Vancomicina/farmacologia
3.
Anal Chem ; 92(19): 13396-13404, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: covidwho-738932

RESUMO

Rapid, accurate, reliable, and risk-free tracking of pathogenic microorganisms at the single-cell level is critical to achieve efficient source control and prevent outbreaks of microbial infectious diseases. For the first time, we report a promising approach for integrating the concepts of a remarkably large Stokes shift and dual-recognition into a single matrix to develop a pathogenic microorganism stimuli-responsive ratiometric fluorescent nanoprobe with speed, cost efficiency, stability, ultrahigh specificity, and sensitivity. As a proof-of-concept, we selected the Gram-positive bacterium Staphylococcus aureus (S. aureus) as the target analyte model, which easily bound to its recognition aptamer and the broad-spectrum glycopeptide antibiotic vancomycin (Van). To improve the specificity and short sample-to-answer time, we employed classic noncovalent π-π stacking interactions as a driving force to trigger the binding of Van and aptamer dual-functionalized near-infrared (NIR) fluorescent Apt-Van-QDs to the surface of an unreported blue fluorescent π-rich electronic carbon nanoparticles (CNPs), achieving S. aureus stimuli-responsive ratiometric nanoprobe Apt-Van-QDs@CNPs. In the assembly of Apt-Van-QDs@CNPs, the blue CNPs (energy donor) and NIR Apt-Van-QDs (energy acceptor) became close to allow the fluorescence resonance energy transfer (FRET) process, leading to a remarkable blue fluorescence quenching for the CNPs at ∼465 nm and a clear NIR fluorescence enhancement for Apt-Van-QDs at ∼725 nm. In the presence of S. aureus, the FRET process from CNPs to Apt-Van-QDs was disrupted, causing the nanoprobe Apt-Van-QDs@CNPs to display a ratiometric fluorescent response to S. aureus, which exhibited a large Stokes shift of ∼260 nm and rapid sample-to-answer detection time (∼30.0 min). As expected, the nanoprobe Apt-Van-QDs@CNPs showed an ultrahigh specificity for ratiometric fluorescence detection of S. aureus with a good detection limit of 1.0 CFU/mL, allowing the assay at single-cell level. Moreover, we also carried out the precise analysis of S. aureus in actual samples with acceptable results. We believe that this work offers new insight into the rational design of efficient ratiometric nanoprobes for rapid on-site accurate screening of pathogenic microorganisms at the single-cell level in the early stages, especially during the worldwide spread of COVID-19 today.


Assuntos
Bactérias/química , Infecções Bacterianas/diagnóstico , Infecções Bacterianas/microbiologia , Técnicas Biossensoriais/métodos , Corantes Fluorescentes/síntese química , Nanotecnologia/métodos , Antibacterianos/farmacologia , Aptâmeros de Nucleotídeos , Infecções por Coronavirus/complicações , Infecções por Coronavirus/microbiologia , Fluorescência , Transferência Ressonante de Energia de Fluorescência , Microbiologia de Alimentos/métodos , Humanos , Nanopartículas , Pandemias , Pneumonia Viral/complicações , Pneumonia Viral/microbiologia , Sensibilidade e Especificidade , Espectroscopia de Luz Próxima ao Infravermelho , Infecções Estafilocócicas/diagnóstico , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/química , Vancomicina/farmacologia
4.
Am J Disaster Med ; 15(2): 113-128, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804391

RESUMO

During the 2017-2018 listeriosis outbreak in South Africa (SA), the total number of cases reached 1,060. In this study, the disaster management response to the 2017-2018 South Africa listeriosis outbreak is analyzed. The hazard was in part the contamination of a brand of a ready-to-eat (RTE) "polony" with a strain of Listeria monocytogenes ST6. The initial phase of the 2017-2018 listeriosis outbreak was characterized by a rapid increase in the number of detected human cases. The listeriosis outbreak was officially proclaimed in December 2017, resulting in listeriosis being added to the list of notifiable diseases in SA. The delay between onset and proclamation was a result of the difficulty in identifica-tion of the actual number of cases of listeriosis in the country. The response to the disaster included the coordination of the National Department of Health, the National Institute of Communicable Diseases (NICD), businesses/producers of the contaminated brand of RTE products, and the public. Some of these activities led to the removal of the contami-nated products from the retail sector in March 2018, resulting in a decrease in the number of cases found in SA. In re-sponse to the outbreak, the National Department of Health formed a multisector incidence response team and imple-mented the Emergency Response Plan. Impacts of future listeriosis outbreaks could be mitigated by the adoption of international listeriosis guidelines such as the WHO/FAO and FDA. Practical steps in this context should include setting a limit of L. monocytogenes in RTE products. WHO/FAO and FDA listeriosis policies which are described "zero toler-ance" where a limit of < 100 L. monocytogenes cells/g at the moment of consumption is acceptable can be adopted. Additional resources must be provided for research into infectious doses and the various routes of human exposure.


Assuntos
Surtos de Doenças/prevenção & controle , Guias como Assunto , Legislação como Assunto , Listeria monocytogenes , Listeriose/epidemiologia , Formulação de Políticas , Desastres , Notificação de Doenças , Microbiologia de Alimentos , Humanos , Listeriose/diagnóstico , África do Sul
5.
Waste Manag ; 117: 42-47, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32805600

RESUMO

Poultry litter is used as soil amendment or organic fertilizer. While poultry litter is enriched with organic matter suitable for land, the presence of pathogens such as Salmonella in poultry litter is a concern. To investigate the effect of gaseous ozone on pathogen reductions in poultry litter, this study conducted a series of experiments that involved understanding of Salmonella Typhimurium and Escherichia coli O157:H7 inactivation at various doses of Ozone (O3) in wet and dry poultry litter conditions. Previously, ozone treatment has been shown to disinfect the surface of foods and plant materials including fruits, juices, and wastewater, however, additional research are needed to better understand the impacts of ozone on treatment of soil amendments. Sanitizing methods capable of eliminating pathogens of soil amendments are crucial to mitigate disease outbreaks related with litter/manure-based fertilizers. In this study, a bench scale continuous ozone treatment system was designed to produce O3 gas, with a range O3 concentrations (7.15-132.46 mg·L-1), monitor ozone concentrations continuously, and control the ozone exposure time (15 to 90 mins) to understand the effectiveness of O3 in eliminating S. Typhimurium and E. coli O157:H7 in poultry litter. Results showed that 7.15 mg·L-1 did not reduce the counts of S. Typhimurium until exposure to O3 for 90 min. The O3 concentrations of 43.26 ~ 132.46 mg·L-1 exposure reduced the bacterial counts. Furthermore, the moisture content of poultry litter was found to be an influencing factor for pathogen reduction. The pathogen reduction rates were reduced when the moisture content was increased. At higher moisture content, high concentrations of O3 (132.46 mg·L-1) were needed for pathogen reductions. The moisture content of 30% or lower was found to be more effective for controlling pathogen levels in poultry litter. Our study demonstrates that gaseous O3 treatment could be used as an additional decontamination technique to ensure the certain degree of microbiological safety of poultry litter based soil amendment.


Assuntos
Escherichia coli O157 , Ozônio , Animais , Microbiologia de Alimentos , Esterco , Aves Domésticas , Salmonella typhimurium
6.
PLoS One ; 15(8): e0237886, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32810191

RESUMO

Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) causes gastroenteritis in many countries. However, in Brazil there are few studies that have conducted a virulence characterization of this serovar. The aim of this study was to evaluate the virulence potential of S. Typhimurium strains isolated in Brazil. Forty S. Typhimurium strains isolated from humans (n = 20) and food (n = 20) from Brazil were studied regarding their invasion and survival in human epithelial cells (Caco-2) and macrophages (U937). Their virulence potential was determined using the Galleria mellonella larvae model combined with the analysis of virulence genes by whole genome sequencing (WGS). A total of 67.5% of the S. Typhimurium studied (32.5% isolated from humans and 35% isolated from food) invaded Caco-2 epithelial cells at levels similar to or greater than the S. Typhimurium SL1344 prototype strain. In addition, 37.5% of the studied strains (25% isolated from humans and 12.5% isolated from food) survived in U937 human macrophages at levels similar to or greater than SL1344. S. Typhimurium strains isolated from humans (40%) and food (25%) showed high or intermediate virulence in G. mellonella larvae after seven days exposure. Approximately, 153 virulence genes of chromosomal and plasmidial origin were detected in the strains studied. In conclusion, the ability of the S. Typhimurium to invade Caco-2 epithelial cells was strain dependent and was not related to the source or the year of isolation. However, S. Typhimurium strains isolated from humans showed greater survival rates in U937 human macrophages, and presented higher proportion of isolates with a virulent profile in G. mellonella in comparison to strains isolated from food suggesting that this difference may be related to the higher frequency of human isolates which contained plasmid genes, such as spvABCDR operon, pefABCD operon, rck and mig-5.


Assuntos
Microbiologia de Alimentos , Salmonella typhimurium/genética , Salmonella typhimurium/isolamento & purificação , Animais , Brasil , Células CACO-2 , Sobrevivência Celular , Células Epiteliais/microbiologia , Genes Bacterianos , Genótipo , Humanos , Macrófagos/microbiologia , Mariposas/microbiologia , Fenótipo , Plasmídeos/genética , Salmonella typhimurium/patogenicidade , Células U937 , Virulência/genética
7.
PLoS One ; 15(8): e0236807, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760141

RESUMO

Listeria monocytogenes is the etiological agent of listeriosis, a major foodborne disease and an important public health concern. Contamination of meat with L. monocytogenes occurs frequently at the slaughterhouse. Our aims were; 1) to investigate the distribution of L. monocytogenes in the processing areas of four swine slaughterhouses; 2) to describe the diversity of L. monocytogenes strains by pulsed-field gel electrophoresis; 3) to identify persistent L. monocytogenes strains and describe their distribution; 4) to investigate the associations between persistence of strains and their following characteristics: detection in food isolates, detection in human clinical isolates, and the presence of benzalkonium chloride (BAC) resistance genes. Various operation areas within the four swine slaughterhouses were sampled on four occasions. A total of 2496 samples were analyzed, and L. monocytogenes was successfully isolated from 243 samples. The proportion of positive samples ranged from 32 to 58% in each slaughterhouse and from 24 to 68% in each operation area. Fifty-eight different pulsotypes were identified and eight pulsotypes, present in samples collected during 4 visits, were considered persistent. The persistent pulsotypes were significantly more likely to be detected in food (P < 0.01, exact χ²) and human clinical cases (P < 0.01, exact χ²), respectively. Among pulsotypes harboring the BAC bcrABC resistance cassette or the emrE multidrug transporter gene, 42.8% were persistent compared to 4.5% for pulsotypes without these resistance genes (P < 0.01, exact χ²). Our study highlights the importance of persistent L. monocytogenes strains in the environmental contamination of slaughterhouses, which may lead to repeated contamination of meat products. It also shows that the presence of disinfectants resistance genes is an important contributing factor.


Assuntos
Microbiologia de Alimentos , Listeria monocytogenes/fisiologia , Listeriose/diagnóstico , Carne/microbiologia , Matadouros , Animais , Compostos de Benzalcônio/farmacologia , Farmacorresistência Bacteriana/genética , Eletroforese em Gel de Campo Pulsado , Manipulação de Alimentos , Humanos , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/isolamento & purificação , Listeriose/microbiologia , Testes de Sensibilidade Microbiana , Sorogrupo , Suínos
8.
PLoS One ; 15(8): e0232806, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785265

RESUMO

There is an increasing consumer demand for minimally processed, preservative free and microbiologically safe food. These factors, combined with risks of antibiotic resistance, have led to interest in bacteriocins produced by lactic acid bacteria (LAB) as natural food preservatives and as potential protein therapeutics. We previously reported the discovery of plantacyclin B21AG, a circular bacteriocin produced by Lactobacillus plantarum B21. Here, we describe the cloning and functional expression of the bacteriocin gene cluster in the probiotic Lactobacillus plantarum WCFS1. Genome sequencing demonstrated that the bacteriocin is encoded on a 20 kb native plasmid, designated as pB21AG01. Seven open reading frames (ORFs) putatively involved in bacteriocin production, secretion and immunity were cloned into an E. coli/Lactobacillus shuttle vector, pTRKH2. The resulting plasmid, pCycB21, was transformed into L. plantarum WCFS1. The cell free supernatants (CFS) of both B21 and WCFS1 (pCycB21) showed an antimicrobial activity of 800 AU/mL when tested against WCFS1 (pTRKH2) as the indicator strain, showing that functional expression of plantacyclin B21AG had been achieved. Real-time PCR analysis revealed that the relative copy number of pB21AG01 was 7.60 ± 0.79 in L. plantarum B21 whilst pCycB21 and pTRKH2 was 0.51 ± 0.05 and 25.19 ± 2.68 copies respectively in WCFS1. This indicates that the bacteriocin gene cluster is located on a highly stable low copy number plasmid pB21AG01 in L. plantarum B21. Inclusion of the native promoter for the bacteriocin operon from pB21AG01 results in similar killing activity being observed in both the wild type and recombinant hosts despite the lower copy number of pCycB21.


Assuntos
Bacteriocinas/genética , Microbiologia de Alimentos , Lactobacillus plantarum/genética , Probióticos , Mapeamento Cromossômico , Clonagem Molecular , Conservantes de Alimentos , Dosagem de Genes , Genes Bacterianos , Humanos , Família Multigênica , Plasmídeos/genética
9.
PLoS One ; 15(8): e0233665, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804955

RESUMO

Oligomycins are macrolide antibiotics, produced by Streptomyces spp. that show antagonistic effects against several microorganisms such as bacteria, fungi, nematodes and the oomycete Plasmopara viticola. Conidiogenesis, germination of conidia and formation of appressoria are determining factors pertaining to pathogenicity and successful diseases cycles of filamentous fungal phytopathogens. The goal of this research was to evaluate the in vitro suppressive effects of two oligomycins, oligomycin B and F along with a commercial fungicide Nativo® 75WG on hyphal growth, conidiogenesis, conidial germination, and appressorial formation of the wheat blast fungus, Magnaporthe oryzae Triticum (MoT) pathotype. We also determined the efficacy of these two oligomycins and the fungicide product in vivo in suppressing wheat blast with a detached leaf assay. Both oligomycins suppressed the growth of MoT mycelium in a dose dependent manner. Between the two natural products, oligomycin F provided higher inhibition of MoT hyphal growth compared to oligomycin B with a minimum inhibitory concentration of 0.005 and 0.05 µg/disk, respectively. The application of the compounds completely halted conidial formation of the MoT mycelium in agar medium. Further bioassays showed that these compounds significantly inhibited MoT conidia germination and induced lysis. The compounds also caused abnormal germ tube formation and suppressed appressorial formation of germinated spores. Interestingly, the application of these macrolides significantly inhibited wheat blast on detached leaves of wheat. This is the first report on the inhibition of mycelial growth, conidiogenesis, germination of conidia, deleterious morphological changes in germinated conidia, and suppression of blast disease of wheat by oligomycins from Streptomyces spp. Further study is needed to unravel the precise mode of action of these natural compounds and consider them as biopesticides for controlling wheat blast.


Assuntos
Magnaporthe/efeitos dos fármacos , Magnaporthe/patogenicidade , Oligomicinas/farmacologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Triticum/microbiologia , Agentes de Controle Biológico/farmacologia , Grão Comestível/microbiologia , Microbiologia de Alimentos , Fungicidas Industriais/farmacologia , Hifas/efeitos dos fármacos , Hifas/crescimento & desenvolvimento , Magnaporthe/crescimento & desenvolvimento , Micélio/efeitos dos fármacos , Micélio/crescimento & desenvolvimento , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento
10.
Biomed Environ Sci ; 33(6): 385-395, 2020 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-32641201

RESUMO

Objective: This study aimed to evaluate the genetic diversity, virulence, and antimicrobial resistance of Aeromonas isolates from clinical patients, tap water systems, and food. Methods: Ninety Aeromonas isolates were obtained from Ma'anshan, Anhui province, China, and subjected to multi-locus sequence typing (MLST) with six housekeeping genes. Their taxonomy was investigated using concatenated gyrB-cpn60 sequences, while their resistance to 12 antibiotics was evaluated. Ten putative virulence factors and several resistance genes were identified by PCR and sequencing. Results: The 90 Aeromonas isolates were divided into 84 sequence types, 80 of which were novel, indicating high genetic diversity. The Aeromonas isolates were classified into eight different species. PCR assays identified virulence genes in the isolates, with the enterotoxin and hemolysin genes act, aerA, alt, and ast found in 47 (52.2%), 13 (14.4%), 22 (24.4%), and 12 (13.3%) of the isolates, respectively. The majority of the isolates (≥ 90%) were susceptible to aztreonam, imipenem, cefepime, chloramphenicol, gentamicin, tetracycline, and ciprofloxacin. However, several resistance genes were detected in the isolates, as well as a new mcr-3 variant. Conclusions: Sequence type, virulence properties, and antibiotic resistance vary in Aeromonas isolates from clinical patients, tap water systems, and food.


Assuntos
Aeromonas , Água Potável/microbiologia , Farmacorresistência Bacteriana , Microbiologia de Alimentos , Variação Genética , Infecções por Bactérias Gram-Negativas/microbiologia , Aeromonas/efeitos dos fármacos , Aeromonas/genética , Aeromonas/isolamento & purificação , Aeromonas/patogenicidade , Antibacterianos/farmacologia , China , Especificidade da Espécie , Virulência
11.
PLoS One ; 15(6): e0235472, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32603372

RESUMO

Refrigerated ready-to-eat (RTE) dips often have pH and water activity combinations conducive to the proliferation of foodborne pathogens, including Listeria monocytogenes. This study conducted product assessments of five refrigerated RTE dips: baba ghanoush, guacamole, hummus, pesto, and tahini, along with individual dip components including avocado, basil, chickpeas, cilantro, eggplant, garlic, and jalapeno pepper. Dips and dip components were inoculated with 2 log CFU/g of L. monocytogenes and stored at 10°C for 28 days. The pathogen was enumerated throughout storage and growth rates were determined using the DMFit program to compute the time required for L. monocytogenes to achieve a 1 log CFU/g increase in population. Survival and growth rates varied significantly between the refrigerated RTE dips and dip components assessed in this study. For dips, L. monocytogenes progressively decreased in baba ghanoush, pesto, and tahini. In contrast, the pathogen proliferated in both hummus and guacamole and the highest growth rate was observed in guacamole (0.34±0.05 log CFU/g per day) resulting in a 1 log CFU/g increase in population in 7.8 days. L. monocytogenes proliferated in all dip components with the exception of eggplant and garlic. The pathogen achieved the highest growth rate in chickpeas (2.22±1.75 log CFU/g per day) resulting in a computed 1 log CFU/g increase in only 0.5 days. Results from this study can aid in understanding how L. monocytogenes behaves in refrigerated RTE dips and dip components and data can be utilized in understanding product formulations and in risk assessments.


Assuntos
Fast Foods/microbiologia , Listeria monocytogenes/crescimento & desenvolvimento , Cicer/microbiologia , Qualidade de Produtos para o Consumidor , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Conservação de Alimentos/métodos
12.
PLoS One ; 15(7): e0233945, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32701964

RESUMO

The survival of Listeria (L.) monocytogenes in foods and food production environments (FPE) is dependent on several genes that increase tolerance to stressors; this includes competing with intrinsic bacteria. We aimed to uncover genes that are differentially expressed (DE) in L. monocytogenes sequence type (ST) 121 strain 6179 when co-cultured with cheese rind bacteria. L. monocytogenes was cultivated in broth or on plates with either a Psychrobacter or Brevibacterium isolate from cheese rinds. RNA was extracted from co-cultures in broth after two or 12 hours and from plates after 24 and 72 hours. Broth co-cultivations with Brevibacterium or Psychrobacter yielded up to 392 and 601 DE genes, while plate co-cultivations significantly affected the expression of up to 190 and 485 L. monocytogenes genes, respectively. Notably, the transcription of virulence genes encoding the Listeria adhesion protein and Listeriolysin O were induced during plate and broth co-cultivations. The expression of several systems under the control of the global stress gene regulator, σB, increased during co-cultivation. A cobalamin-dependent gene cluster, responsible for the catabolism of ethanolamine and 1,2-propanediol, was upregulated in both broth and plate co-cultures conditions. Finally, a small non-coding (nc)RNA, Rli47, was induced after 72 hours of co-cultivation on plates and accounted for 50-90% of the total reads mapped to L. monocytogenes. A recent study has shown that Rli47 may contribute to L. monocytogenes stress survival by slowing growth during stress conditions through the suppression of branch-chained amino acid biosynthesis. We hypothesize that Rli47 may have an impactful role in the response of L. monocytogenes to co-cultivation by regulating a complex network of metabolic and virulence mechanisms.


Assuntos
Brevibacterium/metabolismo , Queijo/microbiologia , Etanolamina/metabolismo , Microbiologia de Alimentos , Regulação Bacteriana da Expressão Gênica , Listeria monocytogenes/genética , Propilenoglicol/metabolismo , Psychrobacter/metabolismo , Transcriptoma , Aclimatação , Ágar , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Técnicas de Cocultura , Meios de Cultura , Transporte de Elétrons/genética , Fermentação/genética , Listeria monocytogenes/metabolismo , Listeria monocytogenes/patogenicidade , Plasmídeos , RNA Bacteriano/biossíntese , RNA Bacteriano/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Pequeno RNA não Traduzido/biossíntese , Pequeno RNA não Traduzido/genética , Virulência/genética
13.
Food Chem ; 332: 127398, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32610260

RESUMO

Herein, a label-free and dual-readout immunochromatographic test strip (ITS) for the sensitive detection of Escherichia coli (E. coli) O157:H7 by taking advantages of the strong capture ability of Fe3O4@CuS nanostructures (NSs) towards bacteria and their ultrahigh photothermal effects (PTEs) was reported. Especially, without the customarily antibody (Ab)-labeled probe, Fe3O4@CuS NSs could be adsorbed onto the surfaces of bacteria to form Fe3O4@CuS-bacteria conjugates and then trapped by immobilized Abs on the test line (T-line), forming a characteristic yellow band. After direct immunoreactions, the PTEs of Fe3O4@CuS NSs endowed T-line to be irradiated by an 808 nm infrared light, obtaining satisfactory sensitivity and accuracy. Under optimal conditions, E. coli O157:H7, as low as 103 and 102 CFU/mL, could be monitored in colorimetric and photothermal modes. Additionally, E. coli O157:H7 was successfully detected in beef, chicken, milk and honey samples by this proposed platform with a recovery of 80-120%.


Assuntos
Cromatografia de Afinidade/métodos , Cobre/química , Escherichia coli O157/isolamento & purificação , Compostos Férricos/química , Microbiologia de Alimentos/métodos , Animais , Anticorpos Monoclonais/imunologia , Bovinos , Galinhas/microbiologia , Cromatografia de Afinidade/instrumentação , Escherichia coli O157/imunologia , Microbiologia de Alimentos/instrumentação , Mel/microbiologia , Limite de Detecção , Leite/microbiologia , Fitas Reagentes/química , Carne Vermelha/microbiologia
14.
Int J Syst Evol Microbiol ; 70(8): 4544-4554, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32618559

RESUMO

The taxonomic status of six strains of Acinetobacter obtained from meat samples, collected from supermarkets in Porto, Portugal, was investigated using polyphasic analysis. Partial rpoB sequence similarities lower than 95 % to other Acinetobacter species with validly published names led to the hypothesis that these strains represented novel species. This was confirmed based on comparative multilocus sequence analysis, which included the gyrB, recA and 16S rRNA genes, revealing that these strains represented two coherent lineages that were distinct from each other and from all known species. The names Acinetobacter portensis sp. nov. (comprising four strains) and Acinetobacter guerrae sp. nov. (comprising two strains) are proposed for these novel species. The species status of these two groups was confirmed by low (below 95 %) whole-genome sequence average nucleotide identity values and low (below 70 %) digital DNA-DNA hybridization similarities between the whole-genome sequences of the proposed type strains of each novel species and the representatives of the known Acinetobacter species. Phylogenomic treeing from core genome analysis supported these results. The coherence of each new species lineage was supported by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry differentiation of the species at the protein level, by cellular fatty acid profiles, and by unique and differential combinations of metabolic and physiological properties shared by each novel species. The type strain of A. portensis sp. nov. is AC 877T (=CCUG 68672T=CCM 8789T) and the type strain of A. guerrae sp. nov. is AC 1271T (=CCUG 68674T=CCM 8791T).


Assuntos
Acinetobacter/classificação , Microbiologia de Alimentos , Carne/microbiologia , Filogenia , Acinetobacter/isolamento & purificação , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Genes Bacterianos , Tipagem de Sequências Multilocus , Hibridização de Ácido Nucleico , Portugal , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
15.
PLoS One ; 15(7): e0236889, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32730330

RESUMO

Australian rates of campylobacteriosis are among the highest in developed countries, yet only limited work has been done to characterize Campylobacter spp. in Australian retail products. We performed whole genome sequencing (WGS) on 331 C. coli and 285 C. jejuni from retail chicken meat, as well as beef, chicken, lamb and pork offal (organs). Campylobacter isolates were highly diverse, with 113 sequence types (STs) including 38 novel STs, identified from 616 isolates. Genomic analysis suggests very low levels (2.3-15.3%) of resistance to aminoglycoside, beta-lactam, fluoroquinolone, macrolide and tetracycline antibiotics. A majority (>90%) of isolates (52/56) possessing the fluoroquinolone resistance-associated T86I mutation in the gyrA gene belonged to ST860, ST2083 or ST7323. The 44 pork offal isolates were highly diverse, representing 33 STs (11 novel STs) and harboured genes associated with resistance to aminoglycosides, lincosamides and macrolides not generally found in isolates from other sources. Prevalence of multidrug resistant genotypes was very low (<5%), but ten-fold higher in C. coli than C. jejuni. This study highlights that Campylobacter spp. from retail products in Australia are highly genotypically diverse and important differences in antimicrobial resistance exist between Campylobacter species and animal sources.


Assuntos
Antibacterianos/farmacologia , Infecções por Campylobacter/microbiologia , Campylobacter coli/genética , Campylobacter jejuni/genética , Farmacorresistência Bacteriana/genética , Carne/análise , Animais , Infecções por Campylobacter/tratamento farmacológico , Infecções por Campylobacter/genética , Campylobacter coli/efeitos dos fármacos , Campylobacter coli/isolamento & purificação , Campylobacter jejuni/efeitos dos fármacos , Campylobacter jejuni/isolamento & purificação , Bovinos , Galinhas , DNA Bacteriano/genética , Microbiologia de Alimentos , Testes de Sensibilidade Microbiana , Carne Vermelha , Ovinos , Suínos , Sequenciamento Completo do Genoma
16.
PLoS One ; 15(7): e0235440, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32614915

RESUMO

BACKGROUND: Cholera remains a significant public health problem in more than one-third of the countries of the world. Cholera outbreak has become more common in Addis Ababa particularly in the rainy seasons; however, there is a paucity of data on risk factors associated with cholera outbreaks rendering interventions difficult. We investigated the outbreak to identify its etiology, source, risk factors and in order to control the outbreak. METHODS: We compared cases with health center-based unmatched controls (1:2). Cases were patients aged ≥5 years with acute watery diarrhea, with or without vomiting while controls were persons aged ≥5 years without history of acute watery diarrhea. We interviewed our study participants using structured questionnaire to collect demographic and cholera risk factors data. We described the outbreak over time, and then tested our hypotheses using unconditional logistic regression. RESULTS: The outbreak began on 7 September, 2017 reaching its peak on 23 September, 2017 and ended on 01 October, 2017. We identified a total of 25 cases (Median age: 38 years; IQR: 20 years) and recruited 50 controls (Median age: 35 years; IQR: 29 years). All case-patients had acute watery diarrhea and dehydration requiring intravenous fluids. All cases were admitted to cholera treatment center but there were no deaths. Stool and water samples yielded isolates of Vibrio cholerae O1 of serological subtype Ogawa. Consumption of contaminated holy water (AOR: 20.5, 95%CI: 3.50, 119.61) and raw vegetables (AOR: 15.3, 95%CI: 3, 81.51) were independent risk factors whereas washing hands with soap after visiting latrine (AOR: 0.04, 95%CI: 0.01, 0.25) was independent protective factor. CONCLUSION: Our findings demonstrated cholera foodborne transmission via consumption of raw vegetables, and its waterborne transmission via consumption of contaminated holy water. Washing hands with soap after visiting latrine was protective. We recommended cooking of vegetables and promoting hand washing.


Assuntos
Cólera/epidemiologia , Surtos de Doenças , Doenças Transmitidas por Alimentos/epidemiologia , Vibrio cholerae O1/isolamento & purificação , Estudos de Casos e Controles , Diarreia/epidemiologia , Diarreia/microbiologia , Água Potável/microbiologia , Etiópia , Fezes/microbiologia , Microbiologia de Alimentos , Desinfecção das Mãos , Fatores de Risco , Inquéritos e Questionários , Toaletes , Verduras/microbiologia , Verduras/envenenamento , Vômito/epidemiologia , Microbiologia da Água
17.
PLoS One ; 15(7): e0236190, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32702068

RESUMO

The quality of sourdough bread mainly depends on metabolic activities of lactic acid bacteria (LAB). The exopolysaccharides (EPS) produced by LAB affect positively the technological and nutritional properties of the bread, while phytases improve the bioavailability of the minerals by reducing its phytate content. In the present study, a pool of 152 cereal-sourced LAB were screened for production of phytases and EPS for potential use as sourdough starter cultures for the baking industry. There was large heterogeneity in the phytase activity observed among the screened isolates, with 95% showing the ability to degrade sodium phytate on plates containing Sourdough Simulation Medium (SSM). The isolates Lactobacillus brevis LD65 and Lactobacillus plantarum PB241 showed the highest enzymatic activity, while the isolates ascribed to Weissella confusa were characterized by low or no phytase activity. Only 18% of the screened LAB produced EPS, which were distinguished as ropy or mucoid phenotypes on SSM supplemented with sucrose. Almost all the EPS producers carried one or more genes (epsD/E and/or epsA) involved in the production of heteropolysaccharides (HePS), whereas the isolates ascribed to Leuconostoc citreum and W. confusa carried genes involved in the production of both HePS and homopolysaccharides (HoPS). Monosaccharide composition analysis of the EPS produced by a selected subset of isolates revealed that all the HePS included glucose, mannose, and galactose, though at different ratios. Furthermore, a few isolates ascribed to L. citreum and W. confusa and carrying the gtf gene produced ß-glucans after fermentation in an ad hoc formulated barley flour medium. Based on the overall results collected, a subset of candidate sourdough starter cultures for the baking industry was selected, including Lb. brevis LD66 and L. citreum PB220, which showed high phytase activity and positive EPS production.


Assuntos
Pão/microbiologia , Grão Comestível/microbiologia , Microbiologia de Alimentos , Indústrias , Lactobacillales/isolamento & purificação , 6-Fitase/metabolismo , Fermentação , Farinha , Genes Bacterianos , Hordeum , Lactobacillales/genética , Peso Molecular , Monossacarídeos/análise , Polissacarídeos Bacterianos/metabolismo , RNA Ribossômico 16S/genética , Especificidade da Espécie , beta-Glucanas/análise
18.
PLoS One ; 15(7): e0234999, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32702039

RESUMO

Acid adaptation enhances survival of foodborne pathogens under lethal acid conditions that prevail in several food-related ecosystems. In the present study, the role of undissociated acetic acid in inducing acid resistance of Salmonella Enteritidis Phage Type 4 both in laboratory media and in an acid food matrix was investigated. Several combinations of acetic acid (0, 15, 25, 35 and 45 mM) and pH values (4.0, 4.5, 5.0, 5.5, 6.0) were screened for their ability to activate acid resistance mechanisms of pathogen exposed to pH 2.5 (screening assay). Increased survival was observed when increasing undissociated acetic acid within a range of sublethal concentrations (1.9-5.4 mM), but only at pH 5.5 and 6.0. No effect was observed at lower pH values, regardless of the undissociated acetic acid levels. Three combinations (15mM/pH5.0, 35mM/pH5.5, 45mM/pH6.0) were selected and further used for adaptation prior to inoculation in commercial tarama (fish roe) salad, i.e., an acid spread (pH 4.35 ± 0.02), stored at 5°C. Surprisingly and contrary to the results of the screening assay, none of the acid adaptation treatments enhanced survival of Salmonella Enteritidis in the food matrix, as compared to non-adapted cells (control). Further examination of the food pH value, acidulant and storage (challenge) temperature on the responses of the pathogen adapted to 15mM/pH5.0, 35mM/pH5.5 and 45mM/pH6.0 was performed in culture media. Cells adapted to 35mM/pH5.5 were unable to induce acid resistance when exposed to pH 4.35 (tarama salad pH value) at 37°C and 5°C, whereas incubation under refrigeration (5°C) at pH 4.35 sensitized 45mM/pH6.0 adapted cells against the subsequent acid and cold stress. In conclusion, pre-exposure to undissociated acetic acid affected the adaptive responses of Salmonella Enteritidis Phage Type 4 in a concentration- and pH-dependent manner, with regard to conditions prevailing during acid challenge.


Assuntos
Ácido Acético/farmacologia , Adaptação Fisiológica/efeitos dos fármacos , Bacteriófagos , Microbiologia de Alimentos , Salmonella enteritidis/virologia , Ácidos/farmacologia , Animais , Relação Dose-Resposta a Droga , Produtos Pesqueiros/microbiologia , Concentração de Íons de Hidrogênio , Refrigeração
19.
Int J Food Microbiol ; 331: 108749, 2020 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-32622259

RESUMO

As genetically modified microorganisms (GMM), commonly used by the food and feed industry to produce additives, enzymes and flavourings, are frequently harbouring antimicrobial resistance (AMR) genes as selection markers, health and environmental concerns were consequently raised. For this reason, the interest of the competent authorities to control such microbial fermentation products has strongly increased, especially since several recent accidental contaminations of unauthorized GMM, or associated recombinant DNA, in bacterial fermentation products intended for the European food and feed chain. However, no global screening strategy is currently available in enforcement laboratories to assess the presence of GMM harbouring AMR genes and/or the presence of full-length AMR genes. Moreover, the confidentiality of the related GMM dossiers strongly hampers the development of methods to perform such control. To overcome this issue, an analysis of related publicly available patents was performed in this study to identify all reported AMR genes. On this basis, the aminoglycoside adenyltransferase (aadD) gene, conferring a resistance to both kanamycin and neomycin, was identified as a key target to cover a large spectrum of GM bacteria. A real-time PCR method to screen for its potential presence as well as a nested-PCR method associated with a sequencing analysis to assess its full-length were developed to target this aadD gene. The performance of these new methods were successfully evaluated in terms of specificity, sensitivity and applicability, allowing their easy implementation in enforcement laboratories. Moreover, the integration of these newly developed methods to our very recently proposed strategy, initially targeting GMM carrying a chloramphenicol resistance gene, allows to drastically increase the detection spectrum of GM bacteria producing fermentation food and feed products. The data generated by the proposed strategy represents therefore a crucial support for the competent authorities, especially to evaluate potential risks for the food and feed safety.


Assuntos
Bactérias/genética , Farmacorresistência Bacteriana/genética , Microbiologia de Alimentos , Microrganismos Geneticamente Modificados/genética , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Fermentação , Microrganismos Geneticamente Modificados/efeitos dos fármacos , Reação em Cadeia da Polimerase em Tempo Real
20.
Int J Food Microbiol ; 331: 108689, 2020 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-32623291

RESUMO

Lactobacillus (L.) curvatus and L. sakei contain strains, which are assertive in sausage fermentation. Previous work has demonstrated differences in assertiveness at strain level within one species, and revealed either exclusion of competitors by complementary partner strains or their inhibition by single strains. This work addresses interspecies differences in the assertiveness of L. curvatus and L. sakei. Strain sets of L. curvatus and L. sakei were employed as starters in a fermented sausage model and their abundancy upon fermentation was determined by strain-specific MALDI-TOF MS identification. Generally, single or groups of L. sakei strains outcompeted L. curvatus strains. In multiple growth tests employing mMRS and mMSM it could be shown that assertive L. sakei strains can be predicted along their µ max in mMSM. Still, L. curvatus TMW 1.624 could suppress all L. curvatus and most L. sakei strains in competitive settings. This could be referred to its expression of several bacteriocins, which are active against all of the L. curvatus strains. Strain specific differences could be demonstrated in the susceptibility of L. sakei to bacteriocins, and in oxidative stress tolerance, which is higher in co-existing L. sakei strains than in the bacteriocin producer. This suggests that tolerance to bacteriocins and oxidative stress represent additional determinants for assertiveness, above previously reported bacteriocin production versus metabolic complementarism of partner strains.


Assuntos
Fermentação , Microbiologia de Alimentos , Lactobacillus sakei/metabolismo , Lactobacillus/metabolismo , Produtos da Carne/microbiologia , Interações Microbianas , Bacteriocinas/metabolismo , Reatores Biológicos
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