Showing papers in "Letters in Applied Microbiology in 1999"
TL;DR: The results of this study confirmed the possibility of using thyme essential oils or some of their components in food systems to prevent the growth of foodborne bacteria and extend the shelf‐life of processed foods.
Abstract: Essential oils and their components are becoming increasingly popular as naturally occurring antimicrobial agents. In this work the chemical composition and the antimicrobial properties of Thymus essential oils and of their main components were determined. Three essential oils obtained from different species of Thymus growing wild in Sardinia and a commercial sample of Thymus capitatus oil were analysed. The essential oil components were identified by GC/MS analysis. The antimicrobial activity of the oils and components was determined against a panel of standard reference strains and multiple strains of food-derived spoilage and pathogenic bacteria, using a broth microdilution method. The GC/MS analysis showed that the major constituents of the oils were monoterpene hydrocarbons and phenolic monoterpenes, but the concentration of these compounds varied greatly among the oils examined. The results of the antimicrobial assay showed that essential oils extracted from Sardinian Thymus species have an antimicrobial activity comparable to the one observed in other thyme oils. It seems also confirmed that the antimicrobial properties of thyme essential oils are mainly related to their high phenolic content. Among the single compounds tested carvacrol and thymol turned out to be the most efficient against both reference strains and food-derived bacteria. The results of this study confirmed the possibility of using thyme essential oils or some of their components in food systems to prevent the growth of foodborne bacteria and extend the shelf-life of processed foods.
1,043 citations
TL;DR: The use of the m–PCR in combination with the culture method allowed reliable detection and identification of C. jejuni and C. coli.
Abstract: Multiplex PCR assay (m-PCR) with three sets of primers was developed for simultaneous identification of Campylobacter jejuni and C. coli. Poultry faecal samples were enriched in Preston broth for 24 h and streaking on selective media was performed before and after enrichment. m-PCR was applied on bacterial cultures harvested from media plates. The data showed a selective effect of Preston broth which favoured the growth of C. coli. Identification of the species by the hippurate hydrolysis test and by the m-PCR was performed on 294 isolates of Campylobacter. The efficiency of the identification by the biochemical test is only 34% in comparison to 100% efficiency with the PCR. The use of our m-PCR in combination with the culture method allowed reliable detection and identification of C. jejuni and C. coli within 3-4 d.
347 citations
TL;DR: These inhibitory effects of essential oils are interesting in connection with the prevention of mycotoxin contamination in many foods and they could be used instead of synthetic antifungal products.
Abstract: Inhibitory effects of essential oils of oregano (Origanum vulgare), mint (Menta arvensis), basil (Ocimum basilicum), sage (Salvia officinalis) and coriander (Coriandrum sativum), on the mycelial growth and ochratoxin A production by Aspergillus ochraceus NRRL 3174 were studied. Cultures were incubated on yeast extract-sucrose (YES) broth, at concentrations of 0, 500, 750 and 1000 p.p.m. of essential oils during 7, 14 and 21 d at 25 degrees C. At 1000 p.p.m., oregano and mint completely inhibited the fungal growth and ochratoxin A production up to 21 d, while basil was only effective up to 7 d. At 750 p.p.m., oregano was completely effective up to 14 d, whereas mint allowed fungal growth but no ocratoxin A production up to 14 d. At 500 p.p.m., no evident inhibition could be in observed with any of the essential oils under analysis. Sage and coriander showed no important effect at any of the concentrations studied. These inhibitory effects are interesting in connection with the prevention of mycotoxin contamination in many foods and they could be used instead of synthetic antifungal products.
228 citations
TL;DR: There is a need to better understand and promote effective hygiene procedures for the domestic kitchen according to a prescribed routine for Salmonella and Campylobacter spp.
Abstract: Thirteen sites in each of 60 domestic kitchens were examined for Salmonella and Campylobacter spp. following the preparation of a chicken for cooking and the application of different hygiene regimes. During food preparation bacteria became widely disseminated to hand and food contact surfaces. Where cleaning was carried out with detergent and hot water using a prescribed routine there was no significant decrease in the frequency of contaminated surfaces. Where hypochlorite was used in addition, a significant reduction in the number of contaminated sites was observed. The study suggests that there is a need to better understand and promote effective hygiene procedures for the domestic kitchen.
226 citations
TL;DR: Polymerase chain reaction primers which are specific for each of these species based on differences in the V1 region of the 16S rRNA gene are developed.
Abstract: Lactobacillus casei, Lact. paracasei and Lact. rhamnosus form a closely related taxonomic group within the heterofermentative lactobacilli. These three species are difficult to differentiate using traditional fermentation profiles. We have developed polymerase chain reaction primers which are specific for each of these species based on differences in the V1 region of the 16S rRNA gene. Sixty-three Lactobacillus isolates from cheese were identified using these primers. The 12 Lact. rhamnosus and 51 Lact. paracasei identified in this way were also differentiated using a randomly amplified polymorphic DNA (RAPD) primer.
218 citations
TL;DR: Due to their broad antimicrobial activities, the essential oils of the above plants growing in Eastern Cape may have preservative potential for the food and cosmetic industries.
Abstract: Essential oils are frequently used for flavour and fragrance in the perfume, pharmaceutical, cosmetic and food industries. The antimicrobial activities of the essential oils of Artemisia afra, Pteronia incana and Rosmarinus officinalis were tested against 41 microbial strains. The test organisms were selected on the basis of their significance as food spoilage and/or poisoning, common human and plant pathogens. The agar diffusion assay was performed using nutrient agar and antibiotic medium. All the oils tested displayed some antimicrobial activities. However, the efficiency differed and depended both on the type and concentration of the oil, as well as the test microbial strain. Artemisia afra and R. officinalis showed similar and higher antimicrobial activity than P. incana. Due to their broad antimicrobial activities, the essential oils of the above plants growing in Eastern Cape may have preservative potential for the food and cosmetic industries.
209 citations
TL;DR: Addition of lysozyme as a third preservative factor increased the synergistic effect between nisin and carvone, especially in the last part of the exposure period.
Abstract: Nisin, a small antimicrobial protein, was tested for its bactericidal action against Listeria monocytogenes and Bacillus cereus and a typical biphasic reduction of the viable count was observed. The reduction was most fast during the first 10 min of exposure, while the viable count remained stable in the last part of the exposure period. Bacillus cereus was more sensitive towards nisin than L. monocytogenes and the inhibitory effect of nisin was stronger towards cells cultivated and exposed at 8 °C than towards cells cultivated and exposed at 20 °C. Combining nisin with sublethal doses of carvacrol resulted in an increased reduction in the viable count of both organisms, indicating synergy between nisin and carvacrol. Addition of lysozyme as a third preservative factor increased the synergistic effect between nisin and carvone, especially in the last part of the exposure period.
195 citations
TL;DR: Arcobacter butzleri was found to be sensitive to chlorine inactivation and was designated as aerotolerant Campylobacter.
Abstract: Arcobacter butzleri was isolated from a contaminated ground water source. These organisms, previously designated as aerotolerant Campylobacter, were capable of surviving in the ground water environment. Specific DNA probes were used to characterize the isolates in the initial identification and survival studies. Arcobacter butzleri was found to be sensitive to chlorine inactivation.
166 citations
TL;DR: Aqueous extracts from leaves of 30 higher plants, collected from different localities, were screened in vitro for antibacterial activity against different pathovars of the phytopathogenic bacterium, Xanthomonas campestris.
Abstract: Aqueous extracts from leaves of 30 higher plants, collected from different localities, were screened in vitro for antibacterial activity against different pathovars of the phytopathogenic bacterium, Xanthomonas campestris. Eight plant species showed antibacterial activity, based on the zone of inhibition in a diffusion assay. Significant antibacterial activity was observed in the aqueous extracts of Prosopis juliflora, Oxalis corniculata and Lawsonia inermis. The susceptibility of different pathovars of X. campestris to these plant extracts varied. The antibacterial activity of extracts of a few plants was comparable with that of the synthetic antibiotics, bacterimycin and streptocycline. The study indicates the potential of these plant extracts in the management of diseases caused by X. campestris in several important crop plants.
153 citations
TL;DR: The production of a water‐insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H.pylori in vivo.
Abstract: Helicobacter pylori NCTC 11637 produces a water-insoluble biofilm when grown under defined conditions with a high carbon:nitrogen ratio in continuous culture and in 10% strength Brucella broth supplemented with 3 g l−1 glucose. Biofilm accumulated at the air/liquid interface of the culture. Light microscopy of frozen sections of the biofilm material showed few bacterial cells in the mass of the biofilm. The material stained with periodic acid Schiff’s reagent. Fucose, glucose, galactose, and glycero-manno-heptose, N-acetylglucosamine and N-acetylmuramic acid were identified in partially purified and in crude material, using gas chromatography and mass spectrometry. The sugar composition strongly indicates the presence of a polysaccharide as a component of the biofilm material. Antibodies (IgG) to partially purified material were found in both sero-positive and sero-negative individuals. Treatment of the biofilm material with periodic acid reduced or abolished immunoreactivity. Treatment with 5 mol l−1 urea at 100 °C and with phenol did not remove antigenic recognition by patient sera. The production of a water-insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H. pylori in vivo.
147 citations
TL;DR: A Multiplex PCR‐based assay (m‐PCR) with three sets of primers was developed for the detection of all serotypes of Salmonella enterica and the identification ofSalmonella Enteritidis and Salmoneella Typhimurium.
Abstract: A Multiplex PCR-based assay (m-PCR) with three sets of primers was developed for the detection of all serotypes of Salmonella enterica and the identification of Salmonella Enteritidis and Salmonella Typhimurium. This method was evaluated against a bacteriological method for the analysis of environmental swabs of poultry houses. Samples were preenriched in phosphate-buffered peptone water for 24 h and subjected to three different protocols prior to PCR: (i) an immunomagnetic separation using Dynabeads anti-Salmonella (Dynal); (ii) a DNA extraction procedure using the Instagene matrix; (iii) an additional step of culture on an MSRV medium. With protocols 1 and 2, eight positive results were found by PCR and 20 with the bacteriological method. Protocol 3 combining MSRV and PCR gave similar results to those obtained from bacteriological methods and allowed Salmonella detection within 2 days.
TL;DR: An improved qualitative cell cytotoxicity assay for the detection of Bacillus cereus emetic and enterotoxin is described and there were pronounced strain differences in the amount of toxin produced by the B. cereus isolates.
Abstract: An improved qualitative cell cytotoxicity assay for the detection of Bacillus cereus emetic and enterotoxin is described. The presence of toxin in culture supernatant fluids was detected by measurement with the tetrazolium salt MTT, as it adversely affects the metabolic status of cultured CHO cells. Psychrotrophic B. cereus isolates (65) were assessed for toxin production using the cytotoxicity assay, and 91% of culture supernatant fluids were cytotoxic. Toxin assessment using BCET-RPLA and ELISA immunoassays indicated that 51% and 85% of the cultures, respectively, were toxigenic. There were pronounced strain differences in the amount of toxin produced by the B. cereus isolates. Some isolates of B. circulans, B. laterosporus/cereus, B. lentus, B. licheniformis, B. mycoides, B. subtilis and B. thuringiensis were also toxigenic.
TL;DR: A multiplex‐PCR‐based assay was developed for the detection of Salmonella and for the identification of the two serotypes Enteritidis and Typhimurium and had a better sensitivity and agreement rate than the bacteriological method.
Abstract: A multiplex-PCR-based assay (m-PCR) was developed for the detection of Salmonella and for the identification of the two serotypes Enteritidis and Typhimurium. Three sets of primers selected from different genomic sequences amplified a 429 bp fragment specific for the genus Salmonella within a randomly cloned sequence, a 559 bp target specific for Salmonella Typhimurium within the fliC gene and a 312 bp fragment specific for Salmonella Enteritidis within the sefA gene. The m-PCR-based assay was used for detecting Salmonella from 1078 environmental swabs of poultry houses. Prior to PCR, these swabs were pre-enriched in phosphate-buffered peptone water for 18-20 h and then sub-cultured on a Modified Semi-solid Rappaport Vassiliadis medium (MSRV) for 18-20 h. The m-PCR combined with MSRV had a better sensitivity (95%) than the bacteriological method (92.5%). The MSRV-m-PCR assay and the bacteriological method had an agreement rate of 95.6%.
TL;DR: Nine strains of the genus Lactococcus were examined for their probiotic properties, such as adherence to human enterocyte‐like Caco‐2 cells and tolerance to acid and bile, and the highest adhesion was observed with Lactcoccus lactis ssp.
Abstract: There have been few studies on the probiotic activity of Lactococcus strains although they are commonly used as starter bacteria in manufacturing many kinds of fermented dairy products. Nine strains of the genus Lactococcus were examined for their probiotic properties, such as adherence to human enterocyte-like Caco-2 cells and tolerance to acid and bile. Six strains were adhesive and the highest adhesion was observed with Lactcoccus lactis ssp. lactis NIAI527. This strain adhered to the microvilli of cells as observed by scanning electron microscopy and also tolerated low pH and bile. These properties should make strain 527 a potential new probiotic strain.
TL;DR: In vivo activities of components of polysubstrate monooxygenase were decreased at idiophase, concomitant with decreased activities of enzymes involved in free radical scavenging, lipid peroxidation and maintenance of redox potential.
Abstract: Eugenol inhibited aflatoxin production by Aspergillus parasiticus NRRL 2999 in a dose-dependent manner up to a concentration of 0.75 mmol l-1 without inhibiting growth. When the mould was grown for 3 d in the presence of 0.45 mmol l-1 eugenol (concentration inhibiting aflatoxin production by 50%), in vivo activities of components of polysubstrate monooxygenase were decreased at idiophase, concomitant with decreased activities of enzymes involved in free radical scavenging, lipid peroxidation and maintenance of redox potential. These results indicate that antiaflatoxigenic actions of eugenol may be related to inhibition of the ternary steps of aflatoxin biosynthesis involving lipid peroxidation and oxygenation.
TL;DR: Results suggest that the probes are equivalent for detection of the V. parahaemolyticus tlh gene.
Abstract: The biochemical identification and enumeration of Vibrio parahaemolyticus as described in the FDA Bacteriological Analytical Manual is expensive and labour-intensive. To reduce the time and effort necessary to verify the identity of V. parahaemolyticus, the use of a thermolabile haemolysin (tlh) gene probe is proposed. An alkaline phosphatase (AP)-labelled probe was evaluated for specificity against 26 strains of V. parahaemolyticus, 88 strains of other Vibrio species and 10 strains of non-vibrio species. Of the 124 isolates tested, the probe hybridized only with the 26 strains of V. parahaemolyticus, indicating species specificity. Two hundred and six suspect V. parahaemolyticus isolates from oysters were tested by this probe and API-20E diagnostic strips; there was 97% agreement between results. A digoxigenin (DIG)-labelled probe for detection of the tlh gene fragment was prepared by PCR and compared with the AP-labelled probe. When tested on 584 suspect V. parahaemolyticus isolates, results obtained with the AP- and DIG-labelled probes were in 98% agreement. These results suggest that the probes are equivalent for detection of the V. parahaemolyticus tlh gene.
TL;DR: It is suggested that defaunation and coconut oil independently and additively suppress rumen methanogenesis.
Abstract: Diets containing either coconut oil or rumen-protected fat (54 g kg−1 dry matter each) were supplied to Rumen Simulation Technique fermenters filled with faunated and defaunated rumen fluid in a 2 × 2 factorial design. Defaunation immediately reduced methane formation by about 40% with each diet. With coconut oil, methane gradually declined in faunated and defaunated rumen fluid. Finally, the extent of methane suppression was similar, both with coconut oil and with defaunation. Independently of the status of protozoa, the population of methanogens in rumen fluid was significantly reduced by coconut oil. The results suggest that defaunation and coconut oil independently and additively suppress rumen methanogenesis.
TL;DR: It is suggested that tap water is a potential transmission route for fungi both in hospitals and the community in the examined region and may pose a health hazard mainly for the immunocompromised host.
Abstract: The prevalence of fungi was investigated in 126 potable water samples (84 hospital and 42 community samples), in parallel with the standard pollution indicator micro-organisms Filamentous fungi were isolated from 104 of 126 (825%) samples and yeasts from 14 (111%), whereas their mean counts were 366 and 44, respectively Fungi were isolated from 952% of community and 762% of hospital water samples, with the difference being statistically significant (P < 005), while yeasts were isolated from 95 and 119%, respectively Prevailing genera were Penicillium spp, isolated from 64, Aspergillus spp, from 53, and Candida, from nine of the examined samples Colony-forming units of yeasts were significantly correlated with those of total and faecal coliforms, whereas the counts of filamentous fungi were significantly correlated with total heterotrophic bacteria counts These results suggest that tap water is a potential transmission route for fungi both in hospitals and the community in the examined region and may pose a health hazard mainly for the immunocompromised host
TL;DR: The enzyme could hydrolyse fibrin, muscle, collagen, nail and hair and could produce leucine, threonine and tyrosine from feather and could be a useful enzyme for waste treatment by promoting hydrolysis of the above substances in the sewage, or it could be used for animal feed preparation.
Abstract: Keratinolytic activity was detected in the culture broth of feather-degrading thermophilic Streptomyces thermoviolaceus SD8 The crude enzyme was concentrated by precipitation with 80% saturation of ammonium sulphate and desalted by SephadexG-10–120 gel chromatography followed by lyophilization The specific activity of the enzyme was enhanced 50-fold PAGE analysis indicated a monomeric form with a molecular weight of 40 kDa The optimum pH and temperature for production of the enzyme were 8 and 55 °C, respectively The enzyme was stable at a pH range of 6·5–8·5 and up to 65 °C The enzyme could hydrolyse fibrin, muscle, collagen, nail and hair and could produce leucine, threonine and tyrosine from feather It could be a useful enzyme for waste treatment by promoting hydrolysis of the above substances in the sewage, or it could be used for animal feed preparation
TL;DR: In situ assessment of physiological activity by examining multiple targets permits a more comprehensive determination of the site and extent of injury in bacterial cells following sublethal disinfection with chlorine.
Abstract: A suite of fluorescent intracellular stains and probes was used, in conjunction with viable plate counts, to assess the effect of chlorine disinfection on membrane potential (rhodamine 123; Rh123 and bis-(1,3-dibutylbarbituric acid) trimethine oxonol; DiBAC4(3)), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity (5-cyano-2,3-ditolyl tetrazolium chloride; CTC) and substrate responsiveness (direct viable counts; DVC) in the commensal pathogen Escherichia coli O157:H7. After a 5 min exposure to the disinfectant, physiological indices were affected in the following order: viable plate counts > substrate responsiveness > membrane potential > respiratory activity > membrane integrity. In situ assessment of physiological activity by examining multiple targets, as demonstrated in this study, permits a more comprehensive determination of the site and extent of injury in bacterial cells following sublethal disinfection with chlorine. This approach to assessing altered bacterial physiology has application in various fields where detection of stressed bacteria is of interest.
TL;DR: Its sensitivity to gastric peptidases and activity against the food‐borne pathogens make this bacteriocin potentially useful as an antimicrobial agent in foods.
Abstract: A wild type micro-organism producing antibacterial substances has been isolated from a Chinese fermented soybean seasoning and identified as Bacillus subtilis. A crude antibacterial preparation (CABP) was obtained by ammonium sulphate precipitation. Isoelectric focusing assay revealed at least four antimicrobial components in the CABP. However, in SDS-PAGE analysis, only one peptide band displayed antimicrobial activity against pathogenic Bacillus cereus and Listeria monocytogenes. This inhibitory peptide had a molecular weight of approximately 3.4 kDa and a pI value of approximately 4.7. Results of this study suggest that at least one antimicrobial substance produced by this wild type strain of B. subtilis may be a new bacteriocin. Its sensitivity to gastric peptidases and activity against the food-borne pathogens make this bacteriocin potentially useful as an antimicrobial agent in foods.
TL;DR: The reported inhibitory range for lacticin is extended to include methicillin‐resistant Staphylococcus aureus, vancomycin‐resistant Enterococcus faecalis, penicillin-resistant Pneumococcus, Propionibacterium acne and Streptococcus mutans, suggesting that the bacteriocin may have potential as a therapeutic agent in the treatment of human infections.
Abstract: Lacticin 3147 is a broad-spectrum bacteriocin produced by Lactococcus lactis subsp. lactis DPC3147, which has been shown to be active against a range of food-borne bacteria. The reported inhibitory range for lacticin is extended to include methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, penicillin-resistant Pneumococcus, Propionibacterium acne and Streptococcus mutans. This extended host range is not obvious from traditional agar plate-based methods, but reductions in bacterial cell numbers by up to 6 log10 cfu ml−1 was observed after 2 h in time-kill curve studies conducted in broth, suggesting that the bacteriocin may have potential as a therapeutic agent in the treatment of human infections.
TL;DR: The incidence of resistance to ampicillin, chloramphenicol, kanamycin, nalidixic acid, neomycin and streptomycin was significantly greater in native heterotrophic bacteria than in Escherichia coli isolated from a range of sites along the Yarra River in south‐eastern Australia.
Abstract: The incidence of resistance to ampicillin, chloramphenicol, kanamycin, nalidixic acid, neomycin and streptomycin was significantly greater (P < 0.001) in native heterotrophic bacteria than in Escherichia coli isolated from a range of sites along the Yarra River in south-eastern Australia. There was no significant difference in the incidence of resistance between native and faecal bacteria to tetracycline. Both groups were almost totally resistant to penicillin. Multivariate analyses indicated little clear spatial pattern in the incidence of resistance in native bacteria from upstream vs downstream sites along the Yarra River. In contrast, E. coli isolated from upstream (rural) sites tended to have a lower incidence of resistance than isolates from downstream (urban) sites. These findings have implications for the use of antibiotic resistance as a bacteriological water quality parameter.
TL;DR: Aspergillus flavus was the most powerful producer of extracellular keratinases, followed by Alternaria radicina, Trichurus spiralis and Stachybotrys atra.
Abstract: Almost 300 common fungi were screened for synthesis of extracellular keratinases. About 54% of the fungi grew on agar plates with soluble keratin and excreted the enzymes. Some representatives of Fusarium, Acremonium and Geotrichum were the most active. However, when cultivating the promising strains in submerged conditions in a medium with porcine nail as the sole source of carbon and nitrogen, other fungi proved to be potent. Aspergillus flavus was the most powerful producer of extracellular keratinases, followed by Alternaria radicina, Trichurus spiralis and Stachybotrys atra.
TL;DR: The ability of the white‐rot fungus Trametes hirsutus to degrade an insecticide, lindane, in liquid culture was investigated and compared with that of Phanerochaete chrysosporium, finding the mechanism of degradation appears to be the same in both.
Abstract: The ability of the white-rot fungus Trametes hirsutus to degrade an insecticide, lindane, in liquid culture was investigated and compared with that of Phanerochaete chrysosporium. Trametes hirsutus degraded lindane faster than P. chrysosporium but the mechanism of degradation appears to be the same in both. Two metabolites identified in both fungi were tetrachlorocyclohexane and tetrachlorocyclohexanol. The presence of lindane alone inside the mycelium ruled out the involvement of any intracellular enzyme(s) during the initial step of lindane degradation. Lindane at a concentration of 0·27 μmol l−1 exhibited no adverse effect on fungal growth.
TL;DR: It was concluded that a longer holding time is more likely to achieve the complete inactivation of Myco.
Abstract: Raw cow's milk spiked with 10(6) cfu ml-1 of Mycobacterium paratuberculosis was subjected to heat treatments of 72, 75, 78, 80, 85 or 90 degrees C for 15 s, and 72 degrees C for 20 and 25 s, using laboratory pasteurizing units. Three bovine strains of Myco. paratuberculosis were studied (NCTC 8578, B2 and DVL 943). Each strain was subjected to all the heat treatments indicated on three separate occasions. Although each of the heat treatments achieved a substantial (5-6 log10) reduction in numbers of viable Myco. paratuberculosis, small numbers of the organism (4-16 cfu 10 ml-1) survived in a proportion of the milk samples at each of the higher temperatures investigated, right up to 90 degrees C for 15 s. A longer holding time of 25 s at 72 degrees C was found to be more effective at inactivating Myco. paratuberculosis. Only one of the three strains studied, B2, yielded small numbers of survivors after heating at 72 degrees C for 20 s, but it was completely inactivated by extending the holding time at 72 degrees C by a further 5 s to 25 s. It was concluded that a longer holding time is more likely to achieve the complete inactivation of Myco. paratuberculosis in milk than a higher pasteurization temperature.
TL;DR: To assess the hygienic quality of environmental samples from a variety of sources, 198 strains named faecal streptococci were isolated on the basis of conventional international tests used for Public Health purposes and only one isolate was identified as belonging to the Streptococcus genus.
Abstract: The recent revision of the taxonomy of 'faecal streptococci' prompted us to verify the importance of identifying the species of this group of cocci. During a study carried out to assess the hygienic quality of environmental samples from a variety of sources, we isolated 198 strains named faecal streptococci on the basis of conventional international tests (EVA broth multiple tube test) used for Public Health purposes. The predominant species were Enterococcus faecalis (39%) and Ent. faecium (29%), followed by Ent. durans/hirae, Ent. casseliflavus/gallinarum, Ent. raffinosus, with a different prevalence of the species depending on the source. Eighty-four per cent of isolates were true faecal species. Only one isolate was identified as belonging to the Streptococcus genus. The authors stress the opportunity to identify the species. This may help to clarify the ecological and epidemiological characteristics of intestinal enterococci and streptococci in the environment, in drinking and recreational waters and their meaning as indicators of faecal pollution. All isolates were tested for their susceptibility to some antimicrobial agents widely used in medical therapy and the pattern was compared with the pattern of isolates from clinical specimens.
TL;DR: Human ileostomy glycoproteins can be used as a model system to select potential probiotic strains to complement the adhesion test with intestinal cell lines, and the most adhesive strains were able to saturate the substratum.
Abstract: Human ileostomy glycoproteins were used as a model for small intestinal mucus to investigate the adhesion of 12 Lactobacillus strains, one Lactococcus strain and one Propionibacterium strain. Both probiotic and dairy strains were tested. Adhesive and non-adhesive Escherichia coli strains were used as controls. All the strains were also tested for their adhesion to polystyrene. Adhesion to ileostomy glycoproteins and to polystyrene varied significantly among the strains tested. Lactobacillus rhamnosus (human isolate), Lactobacillus GG, Lact. acidophilus 1 and P. freudenreichii adhered to ileostomy glycoproteins. Adhesion was concentration-dependent and the most adhesive strains were able to saturate the substratum. These results indicate that human ileostomy glycoproteins can be used as a model system to select potential probiotic strains to complement the adhesion test with intestinal cell lines.
TL;DR: Investigations of a free‐range broiler flock during the rearing period and at the slaughterhouse by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) of the flaA gene (flaA typing) have shown that poultry carcasses are contaminated by Campylobacter spp.
Abstract: Investigations of a free-range broiler flock during the rearing period and at the slaughterhouse by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the flagellin (flaA) gene (flaA typing) have shown that poultry carcasses are contaminated by Campylobacter spp. strains which were previously present in the poultry faces. Moreover, the investigation of the previous and the following batches in the processing plant using flaA typing have shown that cross-contamination between batches coming from different flocks occurs and is also a risk factor for the presence of Campylobacter spp. on poultry carcasses.
TL;DR: The results suggest that to mimic the processes of contamination in industry, predictive microbiology studies with L. monocytogenes should be performed with organisms cultured at low temperatures.
Abstract: The behaviour of Listeria monocytogenes under chilling processes was investigated. Growth kinetics were measured at 7 degrees C in TSBYE culture medium as a function of pH (7.2 and 6.2), pre-incubation temperatures (4 or 7 degrees C), cooling (0.05 or 0.1 degree C min-1) and freezing (0 and -5 degrees C) treatments. Growth curves generated were fitted by Gompertz and Baranyi functions. The Baranyi function gave better parameter estimation values than the Gompertz equation which over-estimated the specific growth rate values. Listeria monocytogenes grew at 7 degrees C without a lag phase, except when the sub-culture was performed at 37 degrees C, whereas the specific growth rate was affected by the chilling processes. In fact, L. monocytogenes grew slightly faster at 7 degrees C when a 4 degrees C pre-incubation treatment was applied than with a 7 degrees C pre-incubation treatment. These results suggest that to mimic the processes of contamination in industry, predictive microbiology studies with L. monocytogenes should be performed with organisms cultured at low temperatures.