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P. Serratore,A Piano,J. Galletti,M Trentini
Italian Journal of Food Safety , 2009, DOI: 10.4081/ijfs.2009.5.91
Abstract: The aim of this study was to assess the contamination levels of L. monocytogenes in retail smoked salmon of different geographical origin, comparing the performance of two isolation methods, ISO 11290-1 (qualitative) and ISO 11290-2 (quantitative), and also by molecular methods (16S rDNA sequencing, PCR with specific primers). Among 35 samples (7 batches, 5 samples per batch), only 1 sample from Denmark resulted positive for L. monocytogenes. The strains isolated on ALOA and Palcam Agar by the qualitative methods, were confirmed to the specie level (iap+, InlA+, InlB+), belonging to the serotype 1/2c - 3c (D2+), and positive for the virulence genes (InlC+ e InlJ+).
Using of PCR assay for identification of Listeria monocytogenes recovered from table eggs  [cached]
Mohammed Sayed,Moemen Abdel-Azeem,Mahmoud Farghaly,Rafaat Hassanein
Veterinary World , 2009,
Abstract: The purpose of this study was to determine the incidence of Listeria monocytogenes contaminating egg shells and contents of table eggs sold in Assiutcity, Egypt. A total of 300 fresh table eggs were collected randomly from different markets in which every 3 eggs from each market were represented as one egg pooled sample. Each of egg shell and content was subjected to procedures of isolation of L. monocytogenes followed by PCR assay for theprfA gene for identification. It was found that egg shells were contaminated by 7% while none of egg contents were contaminated, concluding that egg shell was more subjected to contamination with L. monocytogenes than egg content. The obtained results revealed the degree of contamination and public health hazard in the surroundings contacting eggs until reaching the markets and consequently the consumers. It can be concluded that it was uncomfortable result to find L. monocytogenes by this degree of contamination in table eggs and how extent the zoonotic view is meaningful. Future control strategies need to consider variations in the epidemiologies of food-borne zoonotic infections, and apply a quantitative risk analysis approach to ensure that the most cost-effective programs are developed. [Vet World 2009; 2(12.000): 453-455]
Occurrence of Listeria species in meat, chicken products and human stools in Assiut city, Egypt with PCR use for rapid identification of Listeria monocytogenes
Ashraf Mohamed Abd El-Malek,Sohaila Fathi Hassan Ali,Raafat Hassanein,Moemen, Abdelazeem
Veterinary World , 2010,
Abstract: The present research was conducted to check the presence of Listeria spp. in some meat and chicken products purchased from retail supermarkets in Assiut (Egypt). A total of 100 samples including 25 samples each of minced frozen beef, luncheon, frozen chicken legs and frozen chicken breast fillets were collected over a 7-month period between January and July 2009 and analyzed for the presence of Listeria spp. In addition, 28 stool cultures examined for Listeria spp. from hospitalized children resident in Assiut Pediatric University Hospital with diarrhea or fever. Out of the total 100 meat samples examined, Listeria spp. were detected in 8 (32%) of minced frozen beef, 8 (32%) of luncheon, 13 (52%) of frozen chicken leg and 14 (56%) of frozen chicken fillet samples analyzed, respectively. Regarding the examined 28 stool cultures from hospitalized children with underlying disease in Assiut Univ. hospital, 2 (7.14%) were found positive for Listeria spp. For identification of L. monocytogenes using polymerase chain reaction (PCR), two primers were selected to detect 217-pb fragment ofthe prfA (transcriptional activator of the virulence factor) gene for L. monocytogenes. 13 selected Listeria isolates displayed beta-haemolysis on sheep blood agar and positive CAMP test were further identified using PCR. PCR results showed that L. monocytogenes were confirmed in one of minced imported frozen meat examined, two of luncheon samples and two of frozen chicken legs with the total incidence of 5 isolates (5%) from the total 100 examined food samples. This suggests the presence of a significant public health hazard linked to the consumption of these meat and chicken products sold in Assiut city contaminated with L. monocytogenes. The public health significance of these pathogens as well as recommended sanitary measures was discussed. [Veterinary World 2010; 3(8.000): 353-359]
Prevalence of Listeria species in camel sausages from retail markets in Aydin province in Turkey and RAPD analysis of Listeria monocytogenes isolates
Gokben Ozbey, Hasan Ertas, Filiz Kok
Irish Veterinary Journal , 2006, DOI: 10.1186/2046-0481-59-6-342
Abstract: A wide variety of meats and meat products, including fermented sausages, can be contaminated with Listeria spp [13]. L. monocytogenes is known to survive the commercial dry sausage manufacturing process [12]. In Turkey, Ciftcioglu [8] found Listeria spp in 11% of sausages, with L. monocytogenes in 2% and L. innocua in 8%. A subsequent study by Guven and Patir [11] found Listeria spp in 16.3% of sausages, with L. monocytogenes in 11.9% and L. innocua in 11.3%.Several molecular genotyping methods have been used to type L. monocytogenes, such as DNA restriction endonuclease analysis [18], multilocus enzyme electrophoresis [3], ribotyping [2] and pulsedfield gel electrophoresis (PFGE) [1]. However, these methods are not well suited for routine use in laboratories and are time-consuming. PFGE is very discriminative, but it is labour-intensive and requires expensive apparatus [10]. RAPD typing is suitable for differentiation of the most commonly found serotypes and for screening large panels of strains [7].The aims of this study were to determine the prevalence of Listeria spp in camel sausages at different retail markets in Aydin provience in the south-west of Turkey, to analyse genetic variability among L. monocytogenes isolates by RAPD using a random primer and to enquire whether there is a public health risk of acquiring listeriosis from consumption of camel sausage.Samples were taken from 100 camel sausages obtained from the different retail markets in Aydin province, in the south-west of Turkey.For microbiological analysis, the sausage casing was removed aseptically. A 25 g sample from each sausage was added to 225 ml of Listeria Enrichment Broth (LEB, Oxoid) and homogenised in a stomacher (Interscience, 78860 St Nom-France) at high speed, for one minute at room temperature and incubated at 37°C for 24 hours (primary enrichment). Then, an aliquot of 0.1 ml of the culture was transferred into tubes containing 10 ml LEB. The tubes were incubated for 24 hours to 48 hou
Listeria monocytogenes en vegetales mínimamente procesados
de Curtis,María Luisa; Franceschi,Olgamar; De Castro,Norma;
Archivos Latinoamericanos de Nutrición , 2002,
Abstract: listeria monocytogenes in vegetables minimally processed ready-to-use. the demand of vegetables minimally processed (ready-to-use) has increased partly due to the frequent use of the food services, where the salads are always included in the daily menus. the use of new technologies for processing and packaging has made possible to obtain a product ready to serve. nevertheless the associated risk of the presence of emergent pathogens, such as listeria monocytogenes seems to be involved. the aim of this work was to assess the microbiological quality of this kind of food. 120 samples of vegetables minimally processed ready-to-use were analyzed for their content of aerobic mesophilic bacteria, total and fecal coliforms and e. coli, and the presence of shigella spp, vibrio cholerae and listeria monocytogenes. the tecra? uniquetm listeria, the bcmò listeria monocytogenes and the api listeria systems, and the methods of molecular detection accuprobetm and gene-trak? were used for isolation and identification. e. coli was detected in approximately 30,3% of the vegetables used in this study. the genus listeria was evidenced in 25% of the samples; 30% corresponded to l. monocytogenes. shigella spp and vibrio cholerae were not isolated. the findings of this study suggest the need of the microbiological control of the vegetables minimally processed ready-to-use to assure their quality and safety.
Identification and Role of Regulatory Non-Coding RNAs in Listeria monocytogenes  [PDF]
Benjamin Izar,Mobarak Abu Mraheil,Torsten Hain
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12085070
Abstract: Bacterial regulatory non-coding RNAs control numerous mRNA targets that direct a plethora of biological processes, such as the adaption to environmental changes, growth and virulence. Recently developed high-throughput techniques, such as genomic tiling arrays and RNA-Seq have allowed investigating prokaryotic cis- and trans-acting regulatory RNAs, including sRNAs, asRNAs, untranslated regions (UTR) and riboswitches. As a result, we obtained a more comprehensive view on the complexity and plasticity of the prokaryotic genome biology. Listeria monocytogenes was utilized as a model system for intracellular pathogenic bacteria in several studies, which revealed the presence of about 180 regulatory RNAs in the listerial genome. A regulatory role of non-coding RNAs in survival, virulence and adaptation mechanisms of L. monocytogenes was confirmed in subsequent experiments, thus, providing insight into a multifaceted modulatory function of RNA/mRNA interference. In this review, we discuss the identification of regulatory RNAs by high-throughput techniques and in their functional role in L. monocytogenes.
Isolation of listeria monocytogenes in neural forms of listeriosis and abortions in ruminants
Vidi? Branka,Milanov Dubravka,Bugarski D.
Acta Veterinaria , 2006, DOI: 10.2298/avb0604343v
Abstract: L. monocytogenes is a food borne pathogen capable of causing serious invasive diseases in humans and animals, including abortion, septicemia, meningitis and meningoencephalitis. Isolation of the agent is the most accurate diagnostic method in all situations of suspected L. monocytogenes infection. Direct isolation of L. monocytogenes is relatively simple in cases when the number of organisms is very large, such as septicaemic disease forms. Isolation is quite difficult if the agent is present in very small quantities, such as in encephalitis, or if the sample is highly contaminated. In this paper we presented the isolation of L. monocytogenes from clinical samples by using selective media for enrichment and isolation, combined with the cold enrichment technique. In our investigation we isolated L. monocytogenes from 18 of the total of 46 investigated tissue samples originating from animals with clinical diagnosis of listeriosis. We also presented the basic differential-diagnostic procedure in relation to the mimicking bacterial species.
Development and validation of an antigen capture ELISA based on monoclonal antibodies specific for Listeria monocytogenes in food
Ottavio Portanti,Tiziana Di Febo,Mirella Luciani,Cinzia Pompilii
Veterinaria Italiana , 2011,
Abstract: A capture enzyme-linked immunosorbent assay (ELISA) for the identification of Listeria monocytogenes in food was standardised and validated. The assay was refined by analysing samples of meat, seafood, dairy products, pasta and flour. The method was found to be 100% specific for Listeria spp. tested, with a limit of sensitivity of 6.6 × 10(3) colony-forming units (cfu)/ml. Comparison of L. monocytogenes capture ELISA against the official International Organization for Standardization (ISO) method 11290-1:1996 for the isolation and identification of L. monocytogenes in food matrices produced a significant concordance index. The assay was validated on food matrices including meat, seafood and dairy products in line with ISO 16140:2003 concerning qualitative analytical methods. The assay was found to be accurate, specific, sensitive, selective, reproducible and fast, resulting in lower costs and faster turnaround in microbiological screening of foods.
Aislamiento e Identificación por Métodos Convencionales y PCR de Listeria Monocytogenes en Quesos Blancos Frescos Comercializados en Cumana, Venezuela.
Villalobos de B,Luz Bettina; Martínez N,Rosa E;
Revista Científica , 2007,
Abstract: the artisan venezuelan cheese is a food that does not have sanitary supervision during its elaboration and sale. this food has been associated with outbreaks of infections diseases in venezuela and especially listeriosis in north america and europe, thereby, it was investigated the presence of listeria monocytogenes in this kind of cheese that is commercialized in municipal and public markets of cumaná. sixty samples of fresh white cheese were analyzed to determine its nacl content and ph values. the isolation and biochemical characterization were carried out by fda standars and api listeria, and the molecular identification by pcr. the ph values were in the range 3.81-7.10, mean 5.87. the nacl percentages were in the range, 0.58-7.60 mean 2.20. ten samples of cheese were positive for listeria spp by biochemical test and api listeria pcr confirmation were identified 2 listeria monocytogenes, 2 l. welshimeri- l. selligeri- l ivanovii group, 5 l. innocua and one l grayi. the l. monocytogenes strains were positive for listeriolisin gene (hly). these results show evidence of failures in the elaboration of this artisan cheese due to great dispersion of nacl and ph values, and confirm the presence listeria monocytogenes in this kind of food.
Detec??o de Listeria monocytogenes pela técnica de PCR em leite contaminado artificialmente
Peres, N.D.;Lange, C.C.;Brito, M.A.V.P.;Brito, J.R.F.;Arcuri, E.F.;Cerqueira, M.M.O.P.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2010, DOI: 10.1590/S0102-09352010000400029
Abstract: the polymerase chain reaction (pcr) was used to detect listeria monocytogenes in inoculated milk samples after selective enrichment. samples of sterile skim milk and raw whole milk (with low, intermediate, and high counts of aerobic mesophilic microorganisms) were inoculated with several concentrations of l. monocytogenes. the results of pcr assays were compared to the results of culturing the samples using a standardized traditional method for isolation of l. monocytogenes. the pathogen was detected by pcr in listeria enrichment broth (leb) after 48h-incubation (sensitivity of 1cfu/ml) but not after 24h-incubation from the samples prepared with sterile skim milk. l. monocytogenes was not detected by pcr in leb after 24 and 48h-incubation from the samples prepared with raw whole milk. using the traditional method, the pathogen was detected in all experiments. however, sensitivity decreased in raw whole milk with high counts of aerobic mesophilic microorganisms (up to 7cfu/ml). best results were obtained when pcr was done to identify presumptive l. monocytogenes colonies directly from palcam and oxford media, after the enrichment step. this procedure allowed reducing to a few hours the period of several days usually needed to obtain the final identification of l. monocytogenes using phenotypic tests.
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