RESUMEN
Natural whey cultures (NWC) are undefined multiple-strain bacterial starter communities that can be affected by even small changes along the entire dairy chain. We applied a multidisciplinary approach to investigate how the addition of 2 mycotoxin-detoxifying agents [sodium smectite and lignocellulose-based material (B1); leonardite and betaine (B2)] to cow diets modified the microbiota of the NWC in manufacture of a Grana-like cheese. Microbiological and flow cytometry analyses showed that the content and viability of lactic acid bacteria (LAB) and the total whey microbiota were not affected by the detoxifying agents, and Streptococcus thermophilus, Lactobacillus helveticus, and Limosilactobacillus fermentum were the dominant taxa. Random amplified polymorphic DNA-PCR fingerprinting and metagenomic analysis highlighted differences in the bacterial community of the NWC and in the relative abundance of Bacteroidetes that increased when B1 and B2 were included in the diet. Two of 6 St. thermophilus biotypes were detected only in control samples; conversely, none of the Lb. helveticus biotypes found in control samples were isolated from B1 and B2. In vitro tests showed that the 2 binders did not significantly affect the development of St. thermophilus, but they stimulated the growth of Lb. helveticus strains recovered only from B1 and B2 NWC. The addition of binders in cow feed can affect the LAB biotypes present in NWC.
Asunto(s)
Queso , Lactobacillus helveticus , Micotoxinas , Alimentación Animal/análisis , Animales , Biodiversidad , Bovinos , Queso/análisis , ADN Bacteriano/análisis , Microbiología de Alimentos , Micotoxinas/análisis , Suero Lácteo/química , Proteína de Suero de Leche/análisisRESUMEN
BACKGROUND: Human milk is a vehicle for bioactive compounds and beneficial bacteria which promote the establishment of a healthy gut microbiome of newborns, especially of preterm infants. Pasteurized donor human milk (PDHM) is the second-best option when preterm mother's own milk is unavailable. Since pasteurization affect the microbiological quality of donor milk, PDHM was inoculated with different preterm milk samples and then incubated, in order to evaluate the effect in terms of bacterial growth, human milk microbiome and proteolytic phenomena. METHODS: In an in-vitro study PDHM was inoculated at 10% v/v using ten preterm milk samples. Microbiological, metataxonomic and peptidomic analyses, on preterm milk samples at the baseline (T0), on PDHM and on inoculated milk (IM) samples at T0, after 2 h (T1) and 4 h (T2) of incubation at 37 °C, were conducted. RESULTS: IM samples at T2 showed a Total Bacterial Count not significantly different (p > 0.01) compared to preterm milk samples. At T2 lactic acid bacteria level was restored in all IM. After inoculation, metataxonomic analysis in IM samples showed that Proteobacteria remained the predominant phylum while Firmicutes moved from 3% at T1 to 9.4% at T2. Peptidomic profile of IM resembled that of PDHM, incubated for the same time, in terms of number and type of peptides. CONCLUSION: The study demonstrated that inoculation of PDHM with mother's own milk could restore bacterial growth and personalize human milk microbiome in PDHM. This effect could be beneficial because of the presence of maternal probiotic bacteria which make PDHM more similar to mother's own milk.
Asunto(s)
Leche Humana , Madres , Femenino , Humanos , Lactante , Recién Nacido , Recien Nacido Prematuro , Pasteurización , Donantes de TejidosRESUMEN
The comprehension of atmospheric pollution levels worldwide is a crucial issue for assessing the health consequences from human exposure to polluted air, and for identifying emission reductions that will be effective for minimizing the potential risks. Advanced interconnected sensors are required that could monitor on real-time toxic gaseous concentration. The success of these instruments depends on the reliability of these devices to quantify and disseminate the pollution levels to nearby citizens. Metal-oxide semiconductors are widely used as functional materials for gas sensing because of their chemo-resistive effect when interacting with gases. Mixed oxides are usually considered for the superior performances shown with respect to the single oxides. In this work, tungsten-tin mixed oxides with different Sn molar fraction (0.0018, 0.12, 0.33 and 0.89 named WS-1, WS-2, WS-3 and WS-4) were synthesized by sol-gel co-precipitation. The powders were characterized by ICP-OES analysis, specific surface area measurements, electron microscopy, X-ray diffraction, UV-Vis-NIR and FT-IR spectroscopies. The powders were also deposited through screen-printing technology, obtaining thick film gas sensors, on which measurements of conductance as a function of temperature, surface potential barrier and dynamical responses in the presence of oxidizing or reducing gases were carried out. Based on the studied properties, the mixed oxides can be divided into two groups: the WO3-like samples (WS-1, WS-2, WS-3) and the SnO2-like sample (WS-4). All samples present pure crystalline structures: this is a new result for the WO3-like samples. There is no literature data reporting about the introduction of so high Sn content in a WO3 structure. The combination of spectroscopic and electrical characterizations allowed the definition of an interpretative model that correlates the deepness of defect levels in the band gap of these materials to the values of the surface potential barrier in air and, as a consequence, to the electrical responses to oxidizing and reducing gases.
RESUMEN
The ingredients of Pharmaceuticals and Personal Care Products (PPCPs) persist in water and conventional treatment plants are not able to remove them efficiently. Sonochemical treatment is insufficient to mineralize organics such as ibuprofen into CO2 and H2O. TiO2 degrades ibuprofen (IBP) under UV light; however, it does not reach a high grade of conversion. Here, we investigated the mineralization of ibuprofen to CO2 by TiO2 UV-C photocatalysis. We replaced nano-sized P25 (the standard catalyst) with a micro-sized commercial sample of TiO2 to preclude the use of nanoparticles which are dangerous for human health and because typical filtration systems are expensive and inefficient. We deposited micro-TiO2 on glass Raschig rings to ensure an easy recovery and reuse of the photocatalyst and we studied its performance both with a batch and a continuous reactor. Micro-TiO2 mineralized 100% of IBP in 24â¯h. TiO2-coated glass Raschig rings degraded 87% of IBP in 6â¯h of UV-C irradiation in a continuous reactor, with a mineralization of 25%. Electronspray ionization mass spectrometer (ESI-MS, positive mode) analyses identified 13 different byproducts and we hypothised a degradration pathway for IBP degradation.
Asunto(s)
Ibuprofeno/efectos de la radiación , Fotólisis , Titanio/química , Contaminantes Químicos del Agua/efectos de la radiación , Vidrio , Ibuprofeno/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/químicaRESUMEN
Cholesterol-lowering activity is one of the most promising properties of lactic acid bacteria with probiotic characteristics. In the present study, 58 potentially probiotic lactic acid bacteria were tested for their ability to survive in vitro digestion and reduce cholesterol in a medium containing cholesterol and bile acids. The best-performing strains (Lactobacillus casei VC199, Lactobacillus paracasei ssp. paracasei SE160 and VC213, Lactobacillus plantarum VS166 and VS513, Enterococcus faecium VC223, and Enterococcus lactis BT161) resulted in a 42 to 55% reduction of the cholesterol level in broth and were further tested in cheese manufacture. The cholesterol content in all the cheeses decreased with ripening. All the strains were present in the cheese at levels higher than 107 cfu/g until 60 d of ripening, the highest reductions (up to 23%) being obtained when Lb. paracasei ssp. paracasei VC213 and E. lactis BT161 were added during the cheese-making. The adjunct cultures had no negative effect on the sensory characteristics of the cheese. Thus, these strains with proven in vitro properties are good candidates for novel probiotic-containing formulations and could be used to functionalize foods such as dairy fermented products.
Asunto(s)
Colesterol/análisis , Productos Lácteos/microbiología , Lactobacillales/fisiología , Animales , Queso/análisis , Digestión , Enterococcus/fisiología , Fermentación , Manipulación de Alimentos/métodos , Microbiología de Alimentos/métodos , Lacticaseibacillus casei/fisiología , Lactobacillus plantarum/fisiología , ProbióticosRESUMEN
We looked for the active hydrogen species in a highly dispersed and very homogeneous 5 wt% Pt/C industrial catalyst (Pt particle mean diameter of 2.0 ± 0.5 nm) for hydrogenation reactions, by coupling H2 adsorption measurements with Inelastic Neutron Scattering (INS). Taking advantage of the enormous progress undergone by INS instruments, we succeeded in collecting INS spectra of unprecedented quality that allowed us to: (1) demonstrate that the Pt nanoparticles are mainly located at the regular edges of the sp2 graphitic domains on the activated carbon; (2) validate that most of the H2 physisorbed on the carbon is side-on adsorbed; (3) detect for the first time H2 molecules adsorbed on hydride-covered Pt nanoparticles; (4) observe Pt-hydrides (on the Pt/C catalyst with the lowest Pt loading among those investigated by INS so far) and (5) provide evidence for the occurrence of spillover of atomic hydrogen from the Pt surface to unsaturated reactive sites located at the irregular borders of the sp2 domains on the activated carbon.
RESUMEN
This study presents the characterization and antibacterial activity of nanostructured Si by plasma treatment method using a tetrafluoromethane (CF4) and hydrogen (H2) mixture. Nanostructured-Si is a synthetic nanomaterial that contains high aspect ratio nanoprotrusions on its surface, produced through a reactive-ion etching process. We have shown that the nanoprotrusions on the surfaces produce a mechanical bactericidal effect. Nanostructured-Si exhibited notable activity against three different microorganisms: Gram-negative (Escherichia coli), Gram-positive (Staphylococcus aureus) and spore-forming bacteria (Bacillus cereus) producing a > 5 log10 reduction after 24h of incubation. Scanning electron microscopy was used to analysis the structure and morphology character of different surfaces evidencing the physical bactericidal activity of the Nanostructured-Si. These results provide excellent prospects for the development of a new generation of antibacterial surfaces.
Asunto(s)
Nanoestructuras , Antibacterianos , Bacillus cereus , Escherichia coli , Fluorocarburos , Pruebas de Sensibilidad Microbiana , Staphylococcus aureusRESUMEN
Prototheca species have increasingly been reported to be opportunistic pathogens that cause mastitis in dairy herds, and it poses an emergent problem because at present, there are no effective therapies for the treatment of protothecal mastitis. This study investigated the in vitro algicidal effect of guanidine on 75 Prototheca zopfii genotype 2 strains isolated from 75 cases of clinical and subclinical bovine mastitis. All strains were susceptible to guanidine in vitro with minimal algaecide concentrations ranging from 0·001 to 0·035%. Guanidine is known to have a high microbicidal effect and is considered to be a new generation microbicidal compound. It is not toxic to human mucous membranes and conjunctivas at low concentrations and has been used as a disinfectant in swimming pools and as an antiseptic for human wounds. The algicidal action of guanidine at low concentrations indicates that it could be an alternative disinfectant or antiseptic for cleaning of the dairy environment and milking equipment, in pre- and postdipping solutions, in the chemical dry therapy of bovine teats and even in the intramammary therapy of P. zopfii infections. This is the first report of the in vitro algicidal effect of guanidine on P. zopfii strains of animal origin. SIGNIFICANCE AND IMPACT OF THE STUDY: Prototheca zopfii genotype 2 is an opportunistic pathogen of bovine mastitis. To date, no effective therapies against protothecal mastitis have been developed. The in vitro algicidal effect of guanidine on 75 P. zopfii genotype 2 strains isolated from cows revealed that all of the isolates were susceptible to the compound at low concentrations, which indicates that guanidine may be used as an antiseptic/disinfectant for dairy milking equipment, in pre- and postdipping solutions, and as a chemical dry therapy or an intramammary therapy. This study describes the in vitro algicidal effect of guanidine on P. zopfii for the first time.
Asunto(s)
Guanidina/farmacología , Mastitis Bovina/epidemiología , Prototheca/efectos de los fármacos , Animales , Antiinfecciosos/farmacología , Antiinfecciosos Locales/farmacología , Bovinos , Industria Lechera , Desinfectantes/farmacología , Femenino , Genotipo , Humanos , Mastitis Bovina/tratamiento farmacológico , Epidemiología Molecular , Prototheca/genética , Prototheca/aislamiento & purificaciónRESUMEN
In this study we investigated the circulation of methicillin-resistant Staphylococcus aureus (MRSA) in 2 dairy cattle farms (farm A and B), previously identified as MRSA-positive in bulk tank milk samples, and epidemiologically related to swine farms. Collected specimens included quarter milk samples and nasal swabs from dairy cows, pig nasal swabs collected at both the farm and slaughterhouse level, environmental dust samples, and human nasal swabs from the farms' owners and workers. The prevalence of MRSA was estimated at the herd level by testing quarter milk samples. The prevalence of MRSA was 4.8% (3/63; 95% confidence interval=0-10.2%) and 60% (33/55; 95% confidence interval=47.05-72.95) in farm A and B, respectively. In farm A, MRSA was also isolated from humans, pigs sampled at both farm and slaughterhouse level, and from environmental samples collected at the pig facilities. The dairy cattle facilities of farm A tested negative for MRSA. In farm B, MRSA was isolated from environmental dust samples in both the cattle and pig facilities, whereas nasal swabs collected from cows and from humans tested negative. Sixty-three selected MRSA isolates obtained from different sources in farm A and B were genetically characterized by multilocus sequence typing, spa-typing, ribosomal spacer-PCR, and also tested for the presence of specific virulence genes and for their phenotypical antimicrobial susceptibility by broth microdilution method. Different clonal complex (CC) and spa-types were identified, including CC398, CC97, and CC1, CC already reported in livestock animals in Italy. The MRSA isolates from quarter milk of farm A and B mostly belonged to CC97 and CC398, respectively. Both lineages were also identified in humans in farm A. The CC97 and CC398 quarter milk isolates were also identified as genotype GTBE and GTAF by ribosomal spacer-PCR respectively, belonging to distinct clusters with specific virulence and resistance patterns. The GTBE and GTAF clusters also included swine, environmental, and human isolates from both farms. A high heterogeneity in the genetic and phenotypic profiles was observed in environmental isolates, in particular from farm B. These results demonstrate the possibility of a dynamic sharing and exchange of MRSA lineages or genotypes between different species and farm compartments in mixed-species farms. The risk of transmission between swine and related dairy cattle herds should be considered. Our findings also confirm the zoonotic potential of livestock-associated MRSA and underline the importance of applying biosecurity measures and good hygiene practices to prevent MRSA spread at the farm level and throughout the food production chain.
Asunto(s)
Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Meticilina , Animales , Bovinos , Granjas , Femenino , Humanos , Ganado , Pruebas de Sensibilidad Microbiana , Infecciones Estafilocócicas/veterinaria , Staphylococcus aureus/genética , PorcinosRESUMEN
Bovine mastitis caused by Prototheca is a serious and complex problem that accounts for high economic losses in the dairy industry. The main objective of this study was to identify and characterize at genetic level different Prototheca strains and provide the most complete data about protothecal antibiotic resistance. The study involves 46 isolates from Italian (13 strains) and Brazilian (33 strains) mastitic milk. These strains were identified by multiplex PCR and single strand conformation polymorphism analysis and characterized by randomly amplified polymorphic DNA (RAPD)-PCR. Moreover, biofilm production and antibiotic susceptibility were evaluated. Forty-two strains resulted as Prototheca zopfii genotype 2, whereas 4 isolates could belong to a potential new Prototheca species. The RAPD-PCR, performed with 3 primers (M13, OPA-4, and OPA-18), showed a notable heterogeneity among isolates and grouped the strains according to the species and geographical origin. Biofilm production was species-dependent and P. zopfii genotype 2 strains were classified as strong biofilm producers. In vitro antibiotic susceptibility tests indicated that Prototheca strains were susceptible to antibacterial drugs belonging to aminoglycosides group; the highest activity against Prototheca strains was observed in the case of colistin sulfate, gentamicin, and netilmicin (100% of susceptible strains). It is interesting to note that all the Italian P. zopfii genotype 2 strains showed lower minimum inhibitory concentration values than the Brazilian ones. Nisin showed more efficacy than lysozyme and potassium sorbate, inhibiting 31% of the strains. Results obtained in this study confirmed that RAPD-PCR is a rapid, inexpensive, and highly discriminating tool for Prototheca strains characterization and could give a good scientific contribution for better understanding the protothecal mastitis in dairy herd.
Asunto(s)
Biopelículas , Prototheca/genética , Técnica del ADN Polimorfo Amplificado Aleatorio , Animales , Antibacterianos , Brasil , Bovinos , Italia , Mastitis Bovina/microbiología , Tipificación MolecularRESUMEN
Chemical composition and structure of different types of macroparticles (specks, spots) and microparticles (microcrystals) present in hard and extra-hard cheeses were investigated. Light microscopy revealed that the small hard specks had the structure of crystalline tyrosine, as confirmed by amino acid analysis. Spots showed a complex structure, including several curd granules, cavities, and microcrystals, and were delimited by a dense protein layer. Spots contained less moisture and ash than the adjacent cheese area, and more protein, including significantly higher contents of valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine. Microcrystals were observed by light and electron microscopy and analyzed by confocal micro-Raman. Among others, calcium phosphate crystals appeared to consist of a central star-shaped structure immersed in a matrix of free fatty acids plus leucine and phenylalanine in free form or in small peptides. A hypothetical mechanism for the formation of these structures has been formulated.
Asunto(s)
Queso/análisis , Proteínas de la Leche/química , Aminoácidos/análisis , Aminoácidos/química , Animales , Fosfatos de Calcio/química , Cristalización , Ácidos Grasos no Esterificados/análisis , Manipulación de Alimentos , Microscopía Confocal , Microscopía ElectrónicaRESUMEN
AIM: People suffering from mental illness are exposed to stigma. However, only few tools are available to assess stigmatization as perceived from the patient's perspective. The aim of this study is to adapt and validate a French version of the Stigma Scale (King et al., 2007 [8]). This self-report questionnaire has a three-factor structure: discrimination, disclosure and positive aspects of mental illness. Discrimination subscale refers to perceived negative reactions of others. Disclosure subscale refers mainly to managing disclosure to avoid discrimination and finally positive aspects subscale taps into how patients are becoming more accepting, more understanding toward their illness. METHOD: In the first step, internal consistency, convergent validity and test-retest reliability of the French adaptation of the 28-item scale were assessed in a sample of 183 patients. Results of confirmatory factor analyses (CFA) did not confirm the hypothesized structure. In the light of the failed attempts to validate the original version, an alternative 9-item short-form version of the Stigma Scale, maintaining the integrity of the original model, was developed based on results of exploratory factor analyses in the first sample and cross-validated in a new sample of 234 patients. RESULTS: Results of CFA did not confirm that the data fitted well to the three-factor model of the 28-item Stigma Scale (χ(2)/df=2.02, GFI=0.77, AGFI=0.73, RMSEA=0.07, CFI=0.77 and NNFI=0.75). Cronbach's α was excellent for discrimination (0.84) and disclosure (0.83) subscales but poor for potential positive aspects (0.46). External validity was satisfactory. Overall Stigma Scale total score was negatively correlated with the score on Rosenberg's Self-Esteem Scale (r=-0.49), and each subscale was significantly correlated with a visual analogue scale that referred to the specific aspect of stigma (0.43≤|r|≤0.60). Intraclass correlation coefficients between 0.68 and 0.89 indicated good test-retest reliability. The results of the CFA demonstrated that the items chosen for the short version of the Stigma Scale have the expected fit properties (χ(2)/df=1.02, GFI=0.98, AGFI=0.98, RMSEA=0.01, CFI=1.0 and NNFI=1.0). Considering the small number (three) of items in each subscale of the short version of the Stigma Scale, α coefficients for discrimination (0.57), disclosure (0.80) and potential positive aspects subscales (0.62) are considered as good. CONCLUSION: Our results suggest that the 9-item French short version of the Stigma Scale is a useful, reliable and valid self-report questionnaire to assess perceived stigmatization in people suffering from mental illness. The time of completion is really short and questions are well understood and accepted by the patients.
Asunto(s)
Comparación Transcultural , Trastornos Mentales/psicología , Estigma Social , Encuestas y Cuestionarios , Adaptación Psicológica , Adulto , Femenino , Hospitales Universitarios , Humanos , Masculino , Trastornos Mentales/diagnóstico , Persona de Mediana Edad , Prejuicio/psicología , Servicio de Psiquiatría en Hospital , Psicometría/estadística & datos numéricos , Valores de Referencia , Reproducibilidad de los Resultados , Autorrevelación , Ajuste Social , TraducciónRESUMEN
Stigma is a "natural" social reaction, partly unconscious and automatic towards "different" and "vulnerable" populations. Suspicion of danger, unemployment, excluded from society, locked in hospital, assaulted or killed are the possible consequences of mental disorders' stigma. Despite advances in psychiatric treatments, the stigma of the "madness" remains a barrier to access to recovery. The stigmatization process is more complex than simple labeling, and leads to discrimination and loss of social power. Understanding the mechanisms of stigmatization can determine targets for effective interventions to fight stigma at the individual, institutional and political levels. The roles of patient and family associations, as well as the recovery model for the professionals, are essential. The aim of this article is to review the various aspects of mental disorders' stigma and to examine ways to cope with them.
Asunto(s)
Trastornos Mentales/psicología , Estigma Social , Estereotipo , Familia , Humanos , Trastornos Mentales/rehabilitación , Trastornos Mentales/terapia , Apoyo SocialRESUMEN
The study concerns 130 Staphylococcus aureus strains isolated from different raw-milk dairy products (122 isolates) and human samples (eight isolates). Four different typing techniques were applied: biochemical profiles (Biolog GP), restriction fragment length polymorphism of coagulase gene (coaRFLP), random amplified polymorphic DNA (RAPD) and multilocus variable number tandem repeat analysis (MLVA). Moreover multiplex-PCR was used to study the distribution of genes encoding staphylococcal enterotoxins. The results of this study reveal marked genomic and phenotypic variability among the tested S. aureus. The considered techniques were all found useful for strain typing, but, based on discriminatory power as the key parameter of the typing system, MLVA and Biolog GP were found to be the most powerful techniques. The methods showed little concordance in terms of discerning the clusters of related strains.
Asunto(s)
Técnicas de Tipificación Bacteriana/métodos , Productos Lácteos/microbiología , Polimorfismo de Longitud del Fragmento de Restricción , Staphylococcus aureus/genética , Animales , Bovinos , Coagulasa/genética , Dermatoglifia del ADN/métodos , Femenino , Humanos , Leche/microbiología , Reacción en Cadena de la Polimerasa/métodos , Polimorfismo de Longitud del Fragmento de Restricción/genética , Técnica del ADN Polimorfo Amplificado Aleatorio/métodos , Mapeo Restrictivo/métodos , Ovinos , Enfermedades de las Ovejas/microbiología , Infecciones Estafilocócicas/diagnóstico , Infecciones Estafilocócicas/veterinaria , Staphylococcus aureus/enzimología , Staphylococcus aureus/aislamiento & purificación , Secuencias Repetidas en Tándem/genéticaRESUMEN
AIMS: To verify to what degree reducing capacity is a characterizing parameter of a species, and of the strains themselves within a given species, of lactic acid bacteria. METHODS AND RESULTS: Eighty-eight strains belonging to 10 species of lactic acid bacteria (LAB) isolated from traditional Italian cheeses were studied for their reduction activity: Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Streptococcus thermophilus, Lactococcus lactis ssp. lactis, Lactobacillus paracasei ssp. paracasei, Lactobacillus plantarum, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus helveticus and Pediococcus pentosaceus. It was observed that the lactococci reached minimum redox potential before the lactobacilli. The reduction rate of Enterococcus spp. and L. lactis ssp. lactis was higher than that of the streptococci and Lactobacillus spp. All the P. pentosaceus strains had poor reduction activity compared with the other species. CONCLUSIONS: The evolution of the redox potential in milk over a time span of 24 h has been found to be a parameter that characterizes a species: the different courses corresponding to the species in question are clearly evident, and interesting differences can also be noted within the same species. SIGNIFICANCE AND IMPACT OF THE STUDY: The reduction aptitude of strains might be used to select and adapt appropriate strains for use as starters for dairy products.
Asunto(s)
Queso/microbiología , Microbiología de Alimentos , Lactobacillaceae/aislamiento & purificación , Animales , Técnicas de Tipificación Bacteriana , Enterococcus/aislamiento & purificación , Enterococcus/metabolismo , Fermentación , Italia , Lactobacillaceae/metabolismo , Leche/microbiología , Oxidación-Reducción , Especificidad de la Especie , Streptococcus/aislamiento & purificación , Streptococcus/metabolismoRESUMEN
AIM: To develop an easy, rapid and efficient DNA extraction procedure for Staphylococcus aureus detection with a low number of steps and removing completely the PCR inhibitors, applicable to raw milk cheese samples, and to compare phenotypical and genotypical method to detect Staph. aureus isolates and staphylococcal enterotoxins (SEs) production. METHODS AND RESULTS: A total of 33 bovine and caprine raw milk cheese samples were analysed by means of both classic microbiological and molecular techniques. All samples were positive for Staph. aureus contamination. The DNA extraction protocol optimized was found to achieve a detection limit of 100 CFU g(-1) for Staph. aureus. None of the samples tested with immunological assays contained SEs but in 14 of 33 samples a mixture of se positive (sea, sec, sed, seg, sel, sej) isolates were identified. CONCLUSIONS: Staphylococcus aureus is a food-borne pathogen mainly detected in finished dairy products. The rapid and efficient detection of Staph. aureus isolates from dairy products is essential for consumer safety. The direct detection of pathogens from food is possible with careful attention to sample preparation and nucleic acid amplification optimization. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that raw milk cheese samples can be tested for Staph. aureus contamination with a rapid, simple and reproducible procedure.
Asunto(s)
Técnicas Bacteriológicas , Queso/microbiología , Enterotoxinas/biosíntesis , Reacción en Cadena de la Polimerasa/métodos , Staphylococcus aureus/aislamiento & purificación , Staphylococcus aureus/metabolismo , Animales , Bovinos , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , Enterotoxinas/genética , Cabras , Sensibilidad y Especificidad , Staphylococcus aureus/genéticaRESUMEN
Milk and dairy products are frequently contaminated with enterotoxigenic Staphylococcus aureus, which is often involved in staphylococcal food poisoning. The distribution of genes encoding staphylococcal enterotoxins (SE) in S. aureus isolated from bovine, goat, sheep and buffalo milk and dairy products was verified by the presence of the corresponding SE production. A total of 112 strains of S. aureus were tested for SE production by immuno-enzymatic (SEA-SEE) and reversed passive latex agglutination (SEA-SED) methods, while multiplex-PCR was applied for SE genes (sea, sec, sed, seg, seh, sei, sej and sel). Of the total strains studied, 67% were detected to have some SE genes (se), but only 52% produced a detectable amount of the classic antigenic SE types. The bovine isolates frequently had enterotoxin SEA, SED and sej, while SEC and sel predominated in the goat and sheep strains. The results demonstrated (i) marked enterotoxigenic S. aureus strain variations, in accordance with strain origin and (ii) the two methods resulted in different information but concurred on the risk of foodstuff infection by S. aureus.
Asunto(s)
Productos Lácteos/microbiología , Enterotoxinas/análisis , Contaminación de Alimentos/análisis , Leche/microbiología , Staphylococcus aureus/genética , Animales , Antígenos Bacterianos/análisis , Antígenos Bacterianos/genética , Búfalos , Bovinos , Recuento de Colonia Microbiana , Enterotoxinas/genética , Femenino , Microbiología de Alimentos , Genes Bacterianos , Cabras , Humanos , Pruebas de Fijación de Látex , Reacción en Cadena de la Polimerasa/métodos , Ovinos , Staphylococcus aureus/metabolismo , Staphylococcus aureus/patogenicidadRESUMEN
Efficient control against bovine mastitis requires sensitive, rapid, and specific tests to detect and identify the main bacteria that cause heavy losses to the dairy industry. Molecular detection of pathogenic microorganisms is based on DNA amplification of the target pathogen. Therefore, efficient extraction of DNA from pathogenic bacteria is a major step. In this study, we aimed to develop a specific, sensitive, and rapid method to extract DNA directly from the main gram-positive bacteria known to cause bovine mastitis (Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, and Streptococcus uberis) found in milk samples. The DNA extraction method is based on the lysing and nuclease-inactivating properties of the chaotropic agent, guanidinium thiocyanate, together with the nucleic acid-binding properties of the silica particles. An efficient protocol consisting of 6 basic steps (3 of which were done twice) was developed and applied directly to milk samples. Absence of PCR inhibitors and DNA quality were evaluated by PCR amplification of the species-specific DNA sequences of the target bacteria. The level of sensitivity achieved in our experiments is applicable to milk sample analysis without sample enrichment.