Detection of Listeria spp. in faeces from animals,in feeds,and in raw foods of animal origin

Thirty-nine samples of feeds and 79 faecal samples were collected at seven different dairy farms, at some of which the cows were suffering from Listeria mastitis. Faecal samples were also collected from poultry on a dairy farm and from cages used for transportation of poultry to slaughter. Also neck-skin samples were taken from 17 carcasses of dressed poultry, and five samples of scalding and chilling water at a poultry slaughterhouse. Finally, 67 samples of minced beef were collected from retail shops. The overall results show that approximately 82% of the feed samples harboured Listeria spp. and 62% Listeria monocytogenes. The faecal samples showed that 67% harboured Listeria spp. and 51% L. monocytogenes. In the minced beef samples, Listeria spp. could be demonstrated in 67% and L. monocytogenes in 28%. Of the faecal samples from poultry, 33% harboured Listeria spp. and also 33% L. monocytogenes. Listeria spp. were detected in 94% of the poultry neck-skin samples, and L. monocytogenes in 47%. Almost all L. monocytogenes from faeces and feeds agglutinated Listeria antisera against serotypes 1–4, while only 71% of the strains from minced beef agglutinated the same antisera. The high prevalence of positive findings indicates that the isolation method used is suitable for detection Listeria spp. in heavily contaminated material as well as in foods with low bacterial counts.     

Prevalence, characterization and sources of Listeria monocytogenes in blue crab (Callinectus sapidus) meat and blue crab processing plants

Seven blue crab processing plants were sampled to determine the prevalence and sources of Listeria spp. and Listeria monocytogenes for two years (2006–2007). A total of 488 raw crabs, 624 cooked crab meat (crab meat) and 624 environmental samples were tested by standard methods. Presumptive Listeria spp. were isolated from 19.5% of raw crabs, 10.8% of crab meat, and 69.5% of environmental samples. L. monocytogenes was isolated from 4.5% of raw crabs, 0.2% of crab meat, and 2.1% of environmental samples. Ninety-seven percent of the isolates were resistant to at least one of the ten antibiotics tested. Eight different serotypes were found among 76 L. monocytogenes isolates tested with the most common being 4b, 1/2b and 1/2a. Automated EcoRI ribotyping differentiated 11 ribotypes among the 106 L. monocytogenes isolates. Based on ribotyping analysis, the distribution of the ribotypes in each processing plant had a unique contamination pattern. A total of 92 ApaI and 88 AscI pulsotypes among the 106 L. monocytogenes isolates were found and distinct pulsotypes were observed in raw crab, crab meat and environmental samples. Ribotypes and serotypes recovered from crab processing plants included subtypes that have been associated with listeriosis cases in other food outbreaks. Our findings suggest that molecular methods may provide critical information about sources of L. monocytogenes in crab processing plants and will augment efforts to improve food safety control strategies such as targeting specific sources of contamination and use of aggressive detergents prior to sanitizing.     

The Elimination of Listeria Monocytogenes Attached to Stainless Steel or Aluminum Using Multiple Hurdles

Ready‐to‐eat luncheon meats sliced in retail delis have been found to pose the greatest risk of foodborne illness from Listeria monocytogenes among all ready‐to‐eat foods. Slicers used in delis have many removable parts that are connected with seals and gaskets, with spaces, cracks and crevices that are difficult to clean adequately and may provide a niche for L. monocytogenes survival. Standard cleaning and sanitizing practices used by deli employees may not eliminate Listeria in these niches. Moist heat is known to be more effective against L. monocytogenes than dry heat at the same temperature and time. The study reported here investigated the effects of moist heat combined with quaternary ammonium compounds (5 or 10 ppm), chlorine (10 or 25 ppm) or peracetic acid (10 or 25 ppm) on inactivating L. monocytogenes attached to stainless steel or aluminum coupons cut from commercial deli meat slicer components. All sanitizers when used alone resulted in a 2‐ to 3‐log reduction of L. monocytogenes on stainless steel or aluminum surfaces, while moist heat alone resulted in a 3‐ to 4‐log reduction. When combined with heat the quaternary ammonium was used at 5 ppm, peracetic acid at 10 ppm and chlorine at 10 ppm. When the 2 lethal treatments were combined there was a 5‐ to7‐log reduction as compared to initial inoculation.     

The incidence of Listeria species in retail foods in Japan.

Meat, fish and vegetable products obtained at retail shops in or around Tokyo were examined for Listeria contamination. Listeria spp. were isolated from 43 (56.6%) out of 76 samples of meat products. L. monocytogenes occurred in 26 (34%) of the samples, L. monocytogenes was isolated from 7 (6.1%) out of 114 samples of fish and fish products including 'ready-to-eat' foods. Listeria was not isolated from any of 21 samples of vegetable and vegetable product including 'ready-to-eat' foods investigated.     

The occurrence of Listeria monocytogenes in cheese from a manufacturer associated with a case of listeriosis

A case of listeriosis was associated with the consumption of a soft cheese produced in England. Goats cheese and other products from the same food manufacturer were examined for the presence of Listeria over the following 11 months. Listeria monocytogenes was isolated from 16 of 25 cheese samples on retail sale, 12 of 24 cheese samples obtained directly from the factory, and from shelving within the plant. Phage-typing of 68 isolates of L. monocytogenes from cheese samples and the factory showed that 66 (97%) were indistinguishable from the strain isolated from the patient's cerebrospinal fluid and stool. L. monocytogenes was not isolated from seven goats milk or two yoghurt samples. Listeria innocua was isolated from 10 cheese samples, two of which contained no other species of Listeria. Levels of L. monocytogenes shortly after production were low (<10/g), but were higher (10⁵–10⁷ cfu/g) in six of the 16 cheese samples obtained from retail outlets. Multiplication of L. monocytogenes was demonstrated in cheeses contaminated at the factory and held at 4°C in the laboratory.     

High prevalence,low counts and uncommon serotypes of Listeria monocytogenes in linguiça, a Brazilian fresh pork sausage

Linguiça is a highly popular and appreciated pork product in Brazil, frequently consumed undercooked. Aiming at collection of data for a future risk assessment, this study evaluated the prevalence and counts of Listeria monocytogenes in linguiça samples collected at retail level in Sao Paulo, SP, Brazil. ISO methods were used for detection and enumeration of the pathogen (11290-1 and 11290-2, respectively). Isolates were submitted to Simplex-PCR for hlyA gene and those with biochemical features of L. monocytogenes and hlyA positive were serotyped using a Multiplex PCR. Ninety percent of the samples were positive for Listeria spp., and L. monocytogenes was detected in 42% of the samples, with counts below 10² CFU/g in all samples. A prevalence of uncommon serotypes 4a and 4c was observed.     

Low prevalence of Listeria monocytogenes in foods from Italy

Listeria monocytogenes is an important foodborne pathogen that causes gastrointestinal disorders, and, especially in immunocompromised people, serious extraintestinal diseases, such as septicemia and meningitis, as well as abortion in pregnant women. Many foods, from both plant and animal origin, have been involved in listeriosis outbreaks. This article reports the results of a 12-year survey (1993 through 2004) on the presence of L. monocytogenes in several kinds of food marketed in Italy. Of 5,788 analyzed samples, 121 (2.1%) were contaminated with L. monocytogenes. The highest prevalence was found in smoked salmon (10.6%) and in poultry meat samples (8.5%) and the lowest in red meat (0.3%). L. monocytogenes was not found in 154 samples of fresh seafood products. Fifty-two isolates were also serotyped by the agglutination method. The most common serotypes detected in the 52 strains tested were 1/2a (36.5%), followed by 1/2c (32.8%), 1/2b (13.5%), 4b (11.5%), 3a (3.8%), and 3b (1.9%). The results of the present study showed low levels of L. monocytogenes in the analyzed samples. A total of 61.5% of the 52 L. monocytogenes strains analyzed belonged to serotypes 1/2a, 1/2b, and 4b, namely the serovars that are most commonly involved in extraintestinal human listeriosis outbreaks. In the ready-to-eat samples, these three serotypes were 40.0% (1/2a), 17.1% (1/2b), and 14.3% (4b). This finding highlights the need to implement strict hygienic measures during the production, distribution, and sale of foods to reduce the risk of foodborne listeriosis in humans to an acceptable level.     

INCIDENCE OF LISTERIA MONOCYTOGENES IN RETAIL CHICKEN MEAT AND ESTABLISHING RELATIONSHIP WITH SOME BACTERIA BY LOGISTIC REGRESSION

ABSTRACT

The objective of this study was to determine the contamination of retail poultry meat in Erzurum (Turkey) by Listeria monocytogenes and to evaluate its relationship with indicator bacteria using logistic regression. The incidence of L. monocytogenes was 32.76%, found in 38 of 116 samples. The application of logistic regression showed Enterobacteriaceae, Pseudomonas spp. and Brochothrix thermosphacta populations have positive, and yeast and mold population have negative relationship with L. monocytogenes presence. The results of this study demonstrate that there is a serious risk in raw poultry meat for consumer health in Erzurum, because of the high incidence of L. monocytogenes in the samples of the present study. Hygienic conditions described in HACCP program should still be enforced in order to minimize L. monocytogenes in poultry meat during the processing.

PRACTICAL APPLICATIONS

Listeria monocytogenes and other Listeria species have been isolated from many different types of raw and processed food, but the main sources and routes of contamination are still not fully understood. There is a need for more knowledge, and data are needed for risk assessment and for improved preventive measures. In order to prevent and control contamination of the environment and food products with this pathogen, it is important to detect the most important sources of contamination and to understand the mechanisms of growth, including relationships with other bacteria. The main concern with raw poultry meat is the incidence of L. monocytogenes in raw chicken because of cross‐contamination with other foods in the home and the possibility of the microorganism surviving in processed chicken. Application of logistic regression was used to identify the main hazards associated with the presence of microorganisms, as well as for applications in predictive food microbiology, modeling binomially distributed data that involve the use of probability models, where the response variable is a “presence/absence” observation of whether or not growth will occur.     

THE INCIDENCE AND LEVEL OF LISTERIA SPP. AND LISTERIA MONOCYTOGENES CONTAMINATION IN PROCESSED POULTRY AT A POULTRY PROCESSING PLANT

To estimate the incidence and levels of Listeria spp. in an industrial poultry processing plant, samples of chicken breast meat, livers, surfaces of saws and tables, hands and gloves were analyzed. Forty percent of the breast samples presented Listeria: L. monocytogenes, L. innocua and L. grayi. Liver samples were contaminated by L. innocua and L. grayi. High levels of Listeria monocytogenes were found on saws (<30–2400 MPN/equipment) and tables (<30–11,000 MPN/equipment). Hands were contaminated by L. monocytogenes, L. innocua and L. grayi and gloves with L. innocua and L. grayi. The levels of Listeria on hands and gloves were low (<110 MPN/hand). L. monocytogenes serotypes were 1/2a, 1/2b, 1/2c and 4b. Overall, the study demonstrated the high prevalence of Listeria spp. and specifically L. monocytogenes in chicken breast meat, equipment and hands. Improvements and innovations at the poultry processing plant may effectively reduce final production contamination with Listeria.     

Prevalence and characterization of antimicrobial resistance of foodborne Listeria monocytogenes isolates in Hebei province of Northern China, 2005-2007

A total of 2177 food samples collected from nine cities in northern China during 2005 to 2007 were screened for the presence of Listeria monocytogenes. All L. monocytogenes isolates were subjected to serotyping, antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), as well as PCR screening to identify genes responsible for tetracycline resistance [tet(L), tet(M), tet(K), tet(S) and tet(B)], transposon Tn916, and class 1 integron. Contamination with L. monocytogenes was detected in 4.13% (90/2177) of the total samples representing various food products. The pathogen was mainly isolated from frozen food made of wheat flour or rice products (26/252, 10.32%) and raw meat products (46/733, 6.28%). Besides, 3.31% (10/302) of cooked meat, 1.17% (4/343) of seafood, 0.98% (2/204) of non-fermented bean products and 0.62% (2/323) of vegetables samples were contaminated by this bacterium. The L. monocytogenes isolates belonged to five serotypes (1/2a, 1/2b, 1/2c, 4b, and 3a), with serotype 1/2a being dominant (48.88%). Antimicrobial resistance was most frequently observed for ciprofloxacin (17.8%), tetracycline (15.6%) and streptomycin (12.2%). Overall, resistance was observed against 14 out of 18 antimicrobials tested while multiple resistances occurred among 18.9% (17/90) isolates. Interestingly, two isolates were resistant to more than five antimicrobials. Among 14 tetracycline-resistant isolates, 13 carried tet(M) gene including nine possessing Tn916, and one harbored tet(S) gene. PFGE analysis revealed genetic heterogeneity among individual serotypes as well as scattered occurrence of some genotypes without any clear-cut correlation to source or food type. The widespread distribution of epidemiologically important serotypes (1/2a, 1/2b and 4b) of L. monocytogenes, and their resistance to commonly used antibiotics indicate a potential public health risk. Our data also indicate that L. monocytogenes could act as a reservoir of mobile tet genes along the food chain.     

Effect of Filling Type and Heating Method on Prevalence of Listeria species and Listeria monocytogenes in Dumplings Produced in Poland

The count of Listeria monocytogenes was determined, before and after heat treatment, in 200 samples of dumplings of 9 brands and with different types of stuffing. Analyses were conducted according to ISO 11290–1 standard and with real‐time PCR method. The highest count of L. monocytogenes was found in meat dumplings (10² to 10⁴ CFU/g), whereas products with white cheese‐potato stuffing and vegetable‐mushroom stuffing contained significantly less Listeria, 20 to 80 and 5 to 32 CFU/g, respectively. In cooled meat dumplings the extent of contamination depended significantly on the producer. In addition, a significant (P < 0.05) correlation was determined between contamination level and meat content in the stuffing (rho = 0.418), especially in stuffing containing pork meat (0.464), contrary to beef‐containing stuffing (0.284). Heating dumplings in boiling water for 2 min completely eliminated L. monocytogenes in meat dumplings. In contrast, the microwave heating applied for 2 min at 600 W only reduced the count of L. monocytogenes by 1 to 2 logs. Hence, the microwave heating failed to reduce the risk of infection with this pathogen below the level permissible in the EU regulation, especially in the most contaminated samples. In this case, the efficacy of microwave heating was significantly (P < 0.05) affected by the initial count of L. monocytogenes (rho = 0.626), then by meat content in the stuffing (0.476), and to the lowest extent—by the type of meat (0.415 to 0.425). However, no Listeria sp. and L. monocytogenes were isolated from cooked dumplings with fruits (strawberries or blueberries).     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Listeria monocytogenes in retail establishments: Contamination routes and control strategies

In the past two decades, serious outbreaks of foodborne disease were caused by Listeria monocytogenes, a pathogen frequently found in delicatessens at retail. Although the prevalence of listeriosis is not high, the severity of disease is significant, with high hospitalization and mortality rates. Potential sources of L. monocytogenes and food contamination routes in retail and food service operations include incoming raw materials, food products, food handlers, customers, vendors, and environmental sources. Risk mitigation strategies for L. monocytogenes should be based on integrated control along the food chain continuum, from farm to retail establishment.     

Incidence of Listeria ssp. in Retail Meat Roasts

Interior muscle cores from 50 beef, 50 pork, and 10 lamb roasts, purchased at retail, were assayed for Listeria ssp., which was isolated from three beef roasts and three pork roasts, but not from lamb roasts. Five isolates of serotype la Listeria monocytogenes were obtained from the roasts, together with one strain each of Listeria innocua and Listeria welshimeri. Twice, L. monocytogenes was present at 10 CFU/ g; all other isolations of Listeria spp. required enrichment (<10 CFU/ g). The presence of listeriae in cores of whole-muscle meat roasts is probably not a result of environmental contamination, and may be due to antemortem exposure of the animal to Listeria.     

INCIDENCE OF LISTERIA SPECIES IN SEAFOOD PRODUCTS OF MYSORE, INDIA

Listeria monocytogenes is one of the most important foodborne pathogens causing illness in humans and animals. Thus, a study was undertaken to investigate the incidence of Listeria species in fresh and dry fish samples marketed in Mysore, India. A total of 164 fresh and dry fish samples collected from retail outlet shops of Mysore, South India, during the period August 2005 through August 2006 were examined for the presence of Listeria species by using ISO 11290 protocol. The incidence of Listeria species was positive in 62 samples (37.8%), and L. monocytogenes was isolated from only three (1.83%) fresh fish samples. Listeria species in seafood were predominant in the order of Listeria innocua (50) (30.49%), Listeria grayi (eight) (4.9%), L. monocytogenes (three) (1.83%) and Listeria seeligeri (one) (0.6%). All isolates of Listeria species were subjected to polymerase chain reaction (PCR) and confirmed with the genus‐specific set of primers, and special emphasis was given for detection of L. monocytogenes using a species‐specific set of primers. The specificity and sensitivity of PCR were in good correlation with the cultural methods. The results indicated a high incidence of Listeria species and L. monocytogenes in fresh fish samples. This warrants the need for appropriate control measures as this would pose a serious threat to human health.     

Inhibition of Listeria monocytogenes by Nisin Combined with Grape Seed Extract or Green Tea Extract in Soy Protein Film Coated on Turkey Frankfurters

The objective of this study was to evaluate the inhibitory effect of grape seed extract (GSE), green tea extract (GTE), nisin and their combinations (nisin with either GSE or GTE) against Listeria monocytogenes. The inhibitory effect of these natural compounds was evaluated in phosphate buffer solution (PBS) medium containing approximately 10⁹ colony‐forming units (CFU/mL) of L. monocytogenes. The effectiveness of these compounds in a meat model system was evaluated by surface inoculation (approximately 10⁶ CFU/g) of L. monocytogenes onto turkey frankfurters. The inoculated frankfurters were dipped into soy protein film‐forming solutions with and without the addition of antimicrobial agents (GSE 1% or GTE 1% or nisin 10000 IU or combinations). Samples were stored at either 4 °C or 10 °C. The inhibitory effects of edible coatings were evaluated on a weekly basis for 28 d. The greatest inhibitory effect was observed in the PBS medium containing GSE (1%) and nisin (10000 IU/mL), which caused a 9‐log cycle reduction of L. monocytogenes population after 3 h incubation at 37 °C. In the meat system, the L. monocytogenes population (7.1 CFU/g) was decreased by more than 2 log cycle after 28 d at 4 °C and 10 °C, in the samples containing nisin (10000 IU) combined with either GSE (1%) or GTE (1%). This research has demonstrated that the use of an edible film coating containing both nisin and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes on ready‐to‐eat meat products.     

Escherichia coli,Salmonella spp., and Staphylococcus aureus susceptibility to antimicrobials of human and veterinary importance in poultry sector of India

In India, little attention has been paid on antimicrobial resistance (AMR) in the context of developing “One Health” approach. Hence, utilizing multi-disciplinary approach, we assess the AMR level and dynamics/pattern of multi-drug resistance (MDR) in Escherichia coli, Salmonella spp., and Staphylococcus aureus circulating over the different stages of poultry in India. A total of 342 isolates including E. coli (n = 143), Salmonella spp. (n = 104), and S. aureus (n = 95) were recovered from fecal (n = 80) and cecal (n = 80) samples of chicken, collected across the different poultry-retail shops and poultry-farms located at urban and rural areas of Rajasthan, India, respectively. High rates of AMR to drugs that are critically/highly important both in human and veterinary medicine were observed among all the isolates. Upward trends in AMR prevalence was observed in poultry-retail shops than in poultry-farms. Notably, >90% of all the isolates were MDR, of particular, pattern/prevalence of MDR was substantially varied across the poultry-farms vs. poultry-retail shops. Our results indicate AMR including MDR to be common in E. coli, Salmonella spp., and S. aureus distributed frequently in poultry. The study encourages the formulation of national policy, programmes and further research with a “One Health” approach that can benefits to the human/animal and the environment.     

Prevalence of the main food-borne pathogens in retail food under the national food surveillance system in Japan

The National Food Surveillance System in Japan was formed in 1998 to monitor the contamination of retail foods with bacterial pathogens. Approximately 2000–3000 samples were tested annually, and the data from food categories that had more than 400 samples collected during 1998–2008 were analysed. With regard to meat, the frequency of positive samples for Salmonella in chicken for raw consumption and ground chicken was 12.7% and 33.5%, respectively. Moreover, Shiga toxin-producing Escherichia coli (STEC) O157 was found in ground meat, organ meat and processed meat, although at a low frequency (0.1%). The prevalence of Campylobacter jejuni/coli was 13.3% and 20.9% in chicken for raw consumption and ground chicken, respectively. In vegetables and fruit, Salmonella was detected in cucumber, lettuce, sprout and tomato samples at a frequency of around 0.1–0.2%. With regard to seafood, Salmonella was found in 0.5% of oysters for raw consumption. Seafood was not contaminated with STEC O157 or Shigella. Serotype Infantis was the most frequently detected serotype of Salmonella in seafood, followed by the serotypes Typhimurium, Schwarzengrund and Manhattan. In ground chicken, 72.2% of the strains were identified as the serotype Infantis. E. coli, as an indicator of food hygiene, was detected in all food categories. The results show the prevalence of the above-mentioned pathogens in the retail food supplied in Japan; further, they indicate that consumption of raw food carries the risk of contracting food-borne infections.     

Listeria species in seafood: isolation and characterization of Listeria spp. from seafood in San Luis, Argentina

One hundred seafood samples (fish, squid and mussel) were collected from the Argentine Atlantic coast and screened for Listeria spp. The isolates were characterized by biochemical tests, serotyping, phage typing and macrorestriction enzymes analysis of DNA (pulsed-field gel electrophoresis). The overall frecuency (n=100) ofListeria spp. was 12%. Of the 12 isolated strains, three strains isolated from different squid samples were identified as L. monocytogenes and nine strains from fish, mussels and squid as L. innocua. All three L. monocytogenes strains belonged to serovar 4b; eight strains of L. innocua were serovar 6a and one strain of L. innocua was serovar 6b. All three L. monocytogenes strains, but only one of the nine L. innocua strains, were phage-typeable. One restriction profile was detected with Apa I and Asc I for L. monocytogenes strains and three with the same enzymes for L. innocua strains. The combination of these patterns allowed definition of four distinct groups within the 12 strains. The results of this study showed that phenotypic methods remain appropriate but that pulsed-field gel electrophoresis is useful for epidemiological purposes.     

Listeria monocytogenes and ready-to-eat seafood in Spain: Study of prevalence and temperatures at retail

The aim of this study was to obtain data from refrigerated ready-to-eat seafood products at retail in Spain (young eels, crabstick and smoked salmon), regarding prevalence and levels of Listeria monocytogenes, storage temperatures and the impact of transport conditions (type of bag) on the temperature of the product. The one-year surveillance period was carried out according to the EC Regulation No. 2073/2005, taking 5 units/batch and analyzing 250 samples following ISO 11290-1/A1 and ISO 11290-2/A methodologies. Low prevalence of L. monocytogenes was observed in surimi products, while 4.8% of smoked salmon samples were positive for Listeria with low levels (<10 cfu/g) and uneven pathogen distribution. A single company was responsible for 80% of the positive lots. All purchased products showed values higher than 4 °C at retail and an average increase of 2.5 °C or up to 6.2 °C was recorded when isothermal or plastic shopping bags were used for transport, respectively. To avoid noncompliance of the Food Safety Objective for L. monocytogenes in seafood RTE products more efforts from all stakeholders are needed, with special attention so as to improve control and maintenance of refrigerators at retail and to enhance consumer education regarding food safety practices.