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Listeria Spp. (listeria + spp)
Selected AbstractsMethods for the isolation and identification of Listeria spp. and Listeria monocytogenes: a reviewFEMS MICROBIOLOGY REVIEWS, Issue 5 2005Uta Gasanov Abstract Listeria monocytogenes is an important food-borne pathogen and is widely tested for in food, environmental and clinical samples. Identification traditionally involved culture methods based on selective enrichment and plating followed by the characterization of Listeria spp. based on colony morphology, sugar fermentation and haemolytic properties. These methods are the gold standard; but they are lengthy and may not be suitable for testing of foods with short shelf lives. As a result more rapid tests were developed based on antibodies (ELISA) or molecular techniques (PCR or DNA hybridization). While these tests possess equal sensitivity, they are rapid and allow testing to be completed within 48 h. More recently, molecular methods were developed that target RNA rather than DNA, such as RT-PCR, real time PCR or nucleic acid based sequence amplification (NASBA). These tests not only provide a measure of cell viability but they can also be used for quantitative analysis. In addition, a variety of tests are available for sub-species characterization, which are particularly useful in epidemiological investigations. Early typing methods differentiated isolates based on phenotypic markers, such as multilocus enzyme electrophoresis, phage typing and serotyping. These phenotypic typing methods are being replaced by molecular tests, which reflect genetic relationships between isolates and are more accurate. These new methods are currently mainly used in research but their considerable potential for routine testing in the future cannot be overlooked. [source] Listeria monocytogenes in spontaneous abortions in humans and its detection by multiplex PCRJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007S. Kaur Abstract Aim: To assess the extent of Listeria monocytogenes in causation of human spontaneous abortions by isolation methods and PCR analysis for the presence of virulence-associated genes. Methods and Results: A total of 305 samples comprising blood, urine, placental bits, faecal and vaginal swabs were collected from 61 patients with spontaneous abortions. Listeria spp. were isolated from 10 samples collected from nine (14·8%) patients. Confirmation of these isolates was based on biochemical tests, haemolysis on blood agar, CAMP test, phosphatidylinositol-specific phospholipase C (PI-PLC) assay followed by in vivo pathogenicity tests and multiplex PCR to detect virulence-associated genes (prfA, plcA, hlyA, actA and iap). Three isolates were confirmed as L. monocytogenes. Of these, two isolates turned out to be pathogenic and found to posses all five genes. However, the remaining two haemolytic L. monocytogenes isolates lacking the plcA gene and activity in the PI-PLC assay were found to be nonpathogenic by in vivo tests. Conclusions: The occurrence of pathogenic L. monocytogenes in cases of spontaneous abortions was 3·3%. It seems that the plcA gene and its expression have an important role as essential virulence determinants in pathogenic Listeria spp. Significance and Impact of the Study: The recovery of pathogenic L. monocytogenes isolates from cases of spontaneous abortion indicates the significance of listeric infection in pregnant women. [source] PREVALENCE AND ANTIMICROBIAL RESISTANCE OF LISTERIA SPECIES IN FOOD PRODUCTS IN BANGKOK, THAILANDJOURNAL OF FOOD SAFETY, Issue 1 2010SIRIPORN STONSAOVAPAK ABSTRACT A total of 380 meat and meat products, dairy and dairy products, fresh vegetables, fresh seafood, and ready-to-eat food samples from supermarkets in Bangkok, Thailand were collected and analyzed for the occurrence of Listeria spp. and of Listeria monocytogenes. The overall incidence of Listeria spp. was 16.8%, most of them were isolated from raw meat and vegetables. L. monocytogenes was isolated from 18 (4.7%) out of 380 studied samples. Other species isolated were L. innocua (6.6%), L. ivanovii (0.8%), L. seeligeri (0.5%), L. grayi (1.6%) and L. welshimeri (2.6%). The antimicrobial susceptibilities of the 64 isolate of Listeria spp. were also examined by the standard disk diffusion method. Listeria spp. were resistant to penicillin (6.3%), chloramphenicol (3.1%) and tetracycline (1.6%), but sensitive to amoxicillin, vancomycin, ampicillin, rifampicin and sulfamethoxazole. PRACTICAL APPLICATIONS Listeria monocytogenes prevalence in food products in Bangkok has been documented. More studies on the occurrence of L. monocytogenes are needed to establish microbiological criteria of foods in the country. The findings of our study, increases in antibiotic resistance among Listeria spp. will provide useful information for the development of public health policy in the use of antimicrobials in food animal production. [source] OCCURRENCE OF LISTERIA SPECIES IN THE PROCESSING STAGES OF FROZEN PEPPERJOURNAL OF FOOD SAFETY, Issue 2 2007SOLMAZ LEE ABSTRACT The occurrence of Listeria monocytogenes and other Listeria spp. in a frozen vegetable processing factory was investigated. From May to October 2002, four separate visits were made to the plant and during all of these visits, a total of 216 samples were collected at different stages of the cube and strip pepper processing line. Additionally, 28 swabs were taken from equipment and food-related contact surfaces. The cube and strip pepper processing lines include raw materials, washing, conveyor belt, scalding, cutting, sieving (drying), and the interior sieve of individually quick frozen (IQF), IQF and finished products. Swab samples were taken from the scalding tank, cooling tank, conveyor belt to IQF, interior part of IQF, mixing shovel of IQF, transport saddles and packaging materials. No Listeria spp. were isolated from the strip pepper processing stages, however, 26 out of 108 (24.1%) samples taken from the cube pepper processing stages were found to be contaminated with Listeria spp. Among these isolates, L. monocytogenes was not identified; however, Listeria welshimeri, Listeria innocua and Listeria ivanovii species were identified in 15, 6 and 5 of the tested samples, respectively. L. welshimeri and L. ivanovii were also isolated from three swab samples. These indicate that even though L. monocytogenes was not isolated, the presence of other Listeria species, particularly L. innocua, in the processing line would be an important criterion for eventual L. monocytogenes contaminations. Thus, periodic controls and application of general hygiene and sanitation principles are necessary in the prevention of possible contaminations. [source] HYGIENIC PARAMETERS, TOXINS AND PATHOGEN OCCURRENCE IN RAW MILK CHEESESJOURNAL OF FOOD SAFETY, Issue 3 2002K. DE REU ABSTRACT In total, 71 samples of retail raw milk cheeses produced or imported in Belgium and samples of Belgian farmhouse cheeses were examined for cotiforms, ,-glucuronidase positive Escherichia coli, Escherichia coli O157, Staphylococcus aureus, Salmonella spp., Listeria spp. and Listeria monocytogenes. The presence of staphylococcal enterotoxins was investigated on samples with S. aureus counts higher than 103 cfu/g. The incidence of coliforms, ,-glucuronidase positive E. coli and S. aureus was higher in soft than in blue veined, semi-hard, hard and fresh cheeses. Four mold-ripened soft cheeses were positive for E. coli O157. One of the 4 cheeses was positive for verotoxin VT2. Staphylococcal enterotoxins were detected in 1 soft redsmear cheese, which was positive for L. monocytogenes. L. monocytogenes was also detected in one fresh cheese. Salmonella was not detected in any of the 71 raw milk cheeses. [source] Antibiotic resistance in Listeria species isolated from catfish fillets and processing environmentLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010B.-Y. Chen Abstract Aims:, To investigate the susceptibility of 221 Listeria spp. (86 Listeria monocytogenes, 41 Listeria innocua and 94 Listeria seeligeri-Listeria welshimeri-Listeria ivanovii) isolated from catfish fillets and processing environment to 15 antibiotics. Methods and Results:,Listeria isolates were analysed by disc-diffusion assay for their resistance to 15 drugs. All isolates were resistant to cefotaxime and clindamycin but were sensitive to ampicillin, cephalothin, chloramphenicol, erythromycin, gentamycin, kanamycin, rifampin, streptomycin, sulfamethoxazole/trimethoprim and vancomycin. Unlike L. monocytogenes and L. seeligeri-L. welshimeri-L. ivanovii isolates, 22% of L. innocua isolates displayed tetracycline/oxytetracycline resistance. Screening of tet genes by PCR identified tet(M) gene in the chromosome of all tetracycline/oxytetracycline-resistant L. innocua. However, this gene was not associated with the integrase gene of Tn1545. Repetitive extragenic palindromic- and enterobacterial repetitive intergenic consensus-PCR typing methods showed no genotype-specific tetracycline resistance in the tet(M)-positive strains. Conclusions:, Catfish fillets and processing environment were currently free of L. monocytogenes resistant to antibiotics commonly used in human listeriosis treatment. However, the presence of tet(M) gene in L. innocua raises the possibility of future acquisition of resistance by L. monocytogenes. Significance and Impact of the Study:, These data will be helpful in improving background data on antibiotics resistance strains isolated from food and processing environment. [source] Glycopeptide-resistance transferability from vancomycin-resistant enterococci of human and animal source to Listeria spp.LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2004S. de Niederhäusern Abstract Aims:, The glycopeptide-resistance transferability from vancomycin-resistant enterococci (VRE) of clinical and animal origin to different species of Listeria was investigated. Methods and Results:, Of 36 matings, performed on membrane filter, the glycopeptide resistance was successfully transferred in six attempts, five with donors of animal origin and only one with donors from clinical source. The acquired glycopeptide resistance in Listeria transconjugants was confirmed by the presence of the conjugative plasmid band and by the amplification of the 732-bp fragment of vanA gene in transferred plasmids. Conclusions:, Despite the lower number of bacteria used in this study, the source of enterococci influenced the outcome of mating. Moreover transferred VanA plasmid induced a different expression in Listeria transconjugants, suggesting that gene expression might be influenced by species affiliation of recipients. Significance and Impact of the Study:, Our data strengthen the opinion that enterococci are an important source of resistance genes for Listeria via the transfer of movable genetic elements. As these strains are commonly found in the same habitats, a horizontal spread of glycopeptide resistance in Listeria spp. could be possible. [source] Presence of Listeria and Salmonella spp. in retail chicken in Northern IrelandLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2003N. Soultos Abstract Aims: Retail packs of fresh chicken in Northern Ireland were sampled to determine the frequency with which they were contaminated with Salmonella and Listeria spp. Methods: Packs of chicken were chosen from supermarkets ensuring a diverse range of EU producer codes were sampled. Salmonellas were isolated using BS EN 12824: 1998 methodology, biotyped and serotyped whilst Listeria spp. were isolated based on EN ISO 11290-1: 1996 procedures and identified using a multiplex PCR system utilizing genus and species specific primers. Significance and Impact of the Study: Only three of 205 samples yielded Salmonella spp. indicating that measures undertaken by the poultry industry to control this pathogen have apparently been successful. However, Listeria spp. were present in 38 of 80 samples tested (48%) and 14 (18%) yielded Listeria monocytogenes. Thus Salmonella controls do not markedly affect this pathogen and retail packs of raw chicken must be considered a potential source of L. monocytogenes, and appropriate precautions taken to prevent infection. [source] Treatment of sanitary-important bacteria by bacteriocin substance V24 in cattle dung waterLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2000A. Lauková Quantification of sanitary-important bacteria (e.g. Enterobacteriaceae), as well as indicators of environmental contamination, was assessed in samples of cattle dung from 25 cattle farms in 15 north-eastern Slovakia districts. The inhibitory effect of crude bacteriocin extract CBE V24 from Enterococcus faecalis V24 against Listeria monocytogenes Ohio and Yersinia enterocolitica YE85 was examined in cattle dung water with the aim of finding a new way of eliminating the health risk of the animal slurry. The following bacterial groups were quantified: Salmonella spp., Shigella -like spp., Proteus spp., Enterobacter spp., Citrobacter spp., Pseudomonas spp., Escherichia coli, Listeria spp., staphylococci, streptococci and enterococci (the average count ranged from 102 up to 104 cfu ml,1). Antagonistic effect of the crude bacteriocin from Enterococcus faecalis V24 in the range of 100,600 Arbitrary units per ml (AU ml,1) was shown against the following bacteria: Enterobacter cloacae, Ent. asburiae, Proteus spp., Salmonella spp., Acinetobacter lwoffi, L. monocytogenes as well as Y. enterocolitica YE85. During tests performed to study the inhibitory effect of the crude bacteriocin CBE V24 (concentration 800, 1600 AU ml,1) against L. monocytogenes Ohio and Y. enterocolitica YE85 in experimentally contaminated cattle dung, a reduction of 2·03 and 1·44 log cfu ml,1, respectively, was already noted after 1 h after crude bacteriocin CBE V24 addition. [source] A new pathway for the synthesis of ,-ribazole-phosphate in Listeria innocuaMOLECULAR MICROBIOLOGY, Issue 6 2010Michael J. Gray Summary The genomes of Listeria spp. encode all but one of 25 enzymes required for the biosynthesis of adenosylcobalamin (AdoCbl; coenzyme B12). Notably, all Listeria genomes lack CobT, the nicotinamide mononucleotide:5,6-dimethylbenzimidazole (DMB) phosphoribosyltransferase (EC 2.4.2.21) enzyme that synthesizes the unique ,-linked nucleotide N1 -(5-phospho-,- d -ribosyl)-DMB (,-ribazole-5,-P, ,-RP), a precursor of AdoCbl. We have uncovered a new pathway for the synthesis of ,-RP in Listeria innocua that circumvents the lack of CobT. The cblT and cblS genes (locus tags lin1153 and lin1110) of L. innocua encode an ,-ribazole (,-R) transporter and an ,-R kinase respectively. Results from in vivo experiments indicate that L. innocua depends on CblT and CblS activities to salvage exogenous ,-R, allowing conversion of the incomplete corrinoid cobinamide (Cbi) into AdoCbl. Expression of the L. innocua cblT and cblS genes restored AdoCbl synthesis from Cbi and ,-R in a Salmonella enterica cobT strain. LinCblT transported ,-R across the cell membrane, but not ,-RP or DMB. UV-visible spectroscopy and mass spectrometry data identified ,-RP as the product of the ATP-dependent ,-R kinase activity of LinCblS. Bioinformatics analyses suggest that ,-R salvaging occurs in important Gram-positive human pathogens. [source] | ||||||||||