Prevalence and level of Listeria monocytogenes and other Listeria species in selected retail ready-to-eat foods in the United Kingdom.

Although listeriosis is a rare cause of human disease in the United Kingdom, an increase in the number of cases has been observed since 2001, almost exclusively in persons older than 60 years. This increase prompted this study on the microbiological safety of ready-to-eat (RTE) foods, which included those types potentially linked to cases of listeriosis. Between May 2006 and April 2007, 6,984 RTE foods were sampled (2,168 sliced meats, 1,242 hard cheese, 1,088 sandwiches, 878 butter, 725 spreadable cheese, 515 confectionery products containing cream, and 368 probiotic drinks). The food types with the highest prevalence of Listeria monocytogenes were sandwiches (7.0%) and sliced meats (3.7% within shelf life, 4.2% end of shelf life). L. monocytogenes at > 100 CFU/g (exceeding the European Commission's food safety criteria limit) only occurred in sandwiches (0.4%) and sliced meats (0.7% within shelf life, 1.0% end of shelf life). Contamination with L. monocytogenes at >100 CFU/g was more frequent in meats that were prepacked and/or of pack size > or = 300 g and in sandwiches that were supplied prepacked that contained salad vegetables as an ingredient. Satisfactory microbiological quality was associated with premises on which the management was trained in food hygiene and those that complied with hazard analysis and critical control point principles. This study provides important information about the microbiological safety of RTE foods and demonstrates that the control of L. monocytogenes in such foods, and in particular sandwiches and sliced meats, is essential in order to minimize the risk of this bacterium being present at levels hazardous to health at the point of consumption.

Assessment of the microbiological safety of dried spices and herbs from production and retail premises in the United Kingdom.

A study of dried spices and herbs from retail and production premises to determine the microbiological status of such products was undertaken in the UK during 2004. According to EC Recommendation 2004/24/EC and European Spice Association specifications, 96% of 2833 retail samples and 92% of 132 production batches were of satisfactory/acceptable quality. Salmonella spp. were detected in 1.5% and 1.1% of dried spices and herbs sampled at production and retail, respectively. Overall, 3.0% of herbs and spices contained high counts of Bacillus cereus (1%, > or =10(5) cfu g(-1)), Clostridium perfringens (0.4%, > or =10(3) cfu g(-1)) and/or Escherichia coli (2.1%, > or =10(2) cfu g(-1)). Ninety percent of samples examined were recorded as being 'ready-to-use', 96% of which were of satisfactory/acceptable quality. The potential public health risk of using spices and herbs as an addition to ready-to-eat foods that potentially undergo no further processing is therefore highlighted in this study. Prevention of microbial contamination in dried herbs and spices lies in the application of good hygiene practices during growing, harvesting and processing from farm to fork, and effective decontamination. In addition, the importance of correct food handling practices and usage of herbs and spices by end users cannot be overemphasised.

Microbiological quality of retail cheeses made from raw, thermized or pasteurized milk in the UK.

Two studies of retail fresh, ripened and semi-hard cheeses made from raw, thermized or pasteurized milk were undertaken in the UK during 2004 and 2005 to determine the microbiological quality of these products. Using microbiological criteria in European Commission Recommendations 2004/24/EC and 2005/175/EC, 2% of both raw, thermized (37/1819 samples) and pasteurized (51/2618 samples) milk cheeses were of unsatisfactory quality. Raw or thermized milk cheeses were of unsatisfactory quality due to levels of Staphylococcus aureus at 10(4)cfu g(-1), Escherichia coli at 10(5)cfu g(-1), and/or Listeria monocytogenes at 10(2)cfu g(-1), whereas pasteurized milk cheeses were of unsatisfactory quality due to S. aureus at 10(3)cfu g(-1) and/or E. coli at 10(3)cfu g(-1). Salmonella was not detected in any samples. Cheeses were of unsatisfactory quality more frequently when sampled from premises rated as having little or no confidence in management and control systems, and stored/displayed at above 8 degrees C. Raw or thermized milk cheeses were also more likely to be of unsatisfactory quality when they were unripened types, and pasteurized milk cheeses when they were: semi-hard types; from specialist cheese shops or delicatessens; cut to order. These results emphasize the need for applying and maintaining good hygiene practices throughout the food chain to prevent contamination and/or bacterial growth. Labelling of cheeses with clear information on whether the cheese was prepared from raw milk also requires improvement.

Prevalence and level of Listeria monocytogenes and other Listeria species in retail pre-packaged mixed vegetable salads in the UK.

As part of the European Commission (EC) co-ordinated programme for 2005, a study of pre-packaged ready-to-eat (RTE) mixed salads containing meat or seafood ingredients from retail premises was undertaken in the UK to determine the frequency and level of Listeria monocytogenes in these products. Almost all (99.8%; 2682/2686) samples were of satisfactory/acceptable microbiological quality. Two (0.1%) samples exceeded EC legal food safety criteria due to the presence of L. monocytogenes in excess of 100 cfu g(-1) (1.7 x 10(2), 9.9 x 10(2)cfu g(-1)) while another two (0.1%) were unsatisfactory due to L. welshimeri levels over 100 cfu g(-1) (1.2 x 10(3), 6.0 x 10(3) cfu g(-1)). Overall contamination of Listeria spp. and L. monocytogenes found in samples of mixed salads in the UK was 10.8% and 4.8%, respectively. Almost twice as many salad samples with meat ingredients were contaminated with Listeria spp. and L. monocytogenes (14.7% and 6.0%, respectively) compared to samples with seafood ingredients (7.4% and 3.8%, respectively). Pre-packaged mixed salads were contaminated with Listeria spp. and L. monocytogenes more frequently when: collected from sandwich shops; not packaged on the premises; stored or displayed above 8 degrees C. This study demonstrates that the control of L. monocytogenes in food manufacturing and at retail sale is essential in order to minimize the potential for this bacterium to be present in mixed salads at the point of consumption at levels hazardous to health.

Public health investigations of Salmonella Enteritidis in catering raw shell eggs, 2002-2004.

AIMS: In response to a dramatic change in the epidemiology of Salmonella Enteritidis in England and Wales thought to be associated with raw shell eggs, the Health Protection Agency initiated public health investigations to establish the incidence of Salmonella contamination and origin of eggs used by catering premises implicated in outbreaks of Salm. Enteritidis. METHODS AND RESULTS: Between October 2002 and November 2004, 16 971 eggs were sampled and Salmonella were recovered from 3.4%. Salmonella was isolated from 5.5% and 6.3% of Spanish and eggs of unknown origin, respectively, used in catering premises linked to outbreaks, a level significantly higher than that (1.1%) found in nonLion Quality UK eggs sampled. The small sample of UK Lion Quality eggs tested (reflecting their lack of use in premises visited) did not contain Salmonella. Several phage types of Salm. Enteritidis other than phage type 4 (PT 4) were identified with nonUK eggs. CONCLUSIONS: Eggs from Spain were implicated as a major source of infection. Eggs were contaminated more frequently with Salmonella when shells were dirty and/or cracked, and stored at above 8 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of Spanish eggs by the catering sector has been identified as a consistent significant factor in many of the outbreaks caused by Salm. Enteritidis nonPT4 in England and Wales during 2002-2004. Advice to caterers and hospitals that raw shell eggs should not be used in food that will either not be cooked or only lightly cooked should be reinforced.

Microbiological safety of retail vacuum-packed and modified-atmosphere-packed cooked meats at end of shelf life.

A study of retail modified-atmosphere-packed and vacuum-packed cooked ready-to-eat meats was undertaken from September through mid-November 2003 to determine the microbiological quality at the end of shelf life and to establish any risk factors in the production, storage, and display of this product. Examination of 2,981 samples using Microbiological Guidelines criteria revealed that 66% were of satisfactory or acceptable microbiology quality, 33% were of unsatisfactory quality mainly due to high aerobic colony counts and Enterobacteriaceae concentrations, and 1% were of unacceptable quality due to the presence of Listeria monocytogenes at 100 CFU/g or higher (27 samples; range of 10(2) to 106 CFU/g) and Campylobacter jejuni (1 sample), indicating a risk to health. All samples at the end of the shelf life had satisfactory (<20 CFU/g) and/or acceptable (<102 CFU/g) levels of Staphylococcus aureus and Clostridium perfringens, four samples (<1%) had unsatisfactory levels of Escherichia coli (range of 102 to 106 CFU/g) and 5.5% of the samples contained L. monocytogenes at <20 CFU/g (4.8%) or between 20 and 100 CFU/g (0.7%). More samples of chicken (45%; 224 of 495 samples), beef (43%; 160 of 371 samples), and turkey (41%; 219 of 523 samples) were of unsatisfactory or unacceptable quality compared with ham (23%; 317 of 1,351 samples) or pork (32%; 67 of 206 samples). Twelve different L. monocytogenes typing characters (serotype-amplified fragment length polymorphism type-phage type) were evaluated for isolates recovered from samples of unacceptable quality, and the 1/2-IX-NT type was recovered from almost half (48%) of these samples. Salmonella was not detected in any samples examined. Risk factors identified for cooked meats that were microbiologically contaminated more frequently included vacuum packaging, packaging on retail premises, slicing, temperature not monitored in display units, and no hazard analysis system in place. Results from this study also suggest that the shelf life assigned to some modified-atmosphere-packed and vacuum-packed meats may not be appropriate.

Microbiological quality of open ready-to-eat salad vegetables: effectiveness of food hygiene training of management.

During September and October 2001, a microbiological study of open, ready-to-eat, prepared salad vegetables from catering or retail premises was undertaken to determine their microbiological quality. The study focused on those salad vegetables that were unwrapped and handled either by staff or customers in the premises where the sample was taken. Examination of salad vegetables from food service areas and customer self-service bars revealed that most (97%; 2,862 of 2,950) were of satisfactory or acceptable microbiological quality, 3% (87) were of unsatisfactory microbiological quality because of Escherichia coli levels in the range of 10(2) to 10(5) colony-forming units per gram. One (<1%) sample was of unacceptable microbiological quality because of the presence of Listeria monocytogenes at 840 colony-forming units per gram. The pathogens E. coli O157, Campylobacter spp., and salmonellas were not detected in any of the samples examined. The display area for most food service and preparation areas (95%) and self-service salad bars (98%) that were visited was judged to be visibly clean by the sampling officer. Most self-service bars (87%) were regularly supervised or inspected by staff during opening hours, and designated serving utensils were used in most salad bars (92%) but in only a minority of food service areas (35%). A hazard analysis system was in place in most (80%) premises, and in 61%, it was documented. Most (90%) managers had received food hygiene training. A direct relationship was shown between increased confidence in the food business management and the presence of food safety procedures and the training of management in food hygiene.

Study of cleaning standards and practices in food premises in the United Kingdom.

A study was undertaken to determine the microbiological status of surfaces used in the preparation of ready-to-eat foods, and to assess cleaning standards and practices in food premises in the UK. A total of 6,533 environmental samples were examined from 1,502 catering (such as restaurants, cafés, and sandwich bars) or retail premises (such as butchers, delicatessens, and bakers): 2,033 samples from chopping/cutting boards, 2,009 from worktop surfaces, 1,359 from food containers, and 1,132 from cleaning cloths. Cleaning cloths were more heavily contaminated with bacteria (Aerobic Colony Count (ACC), Enterobacteriaceae, E. coli, and Staph. aureus) compared to surfaces sampled. Campylobacter spp. were detected in two (0.2%) and Salmonella spp. from one (0.1%) of the cleaning cloths. Surfaces that were visually dirty, wet, last cleaned over 24 hours ago, and boards that were scored or damaged were found to have higher levels of bacteria. A hazard analysis system was in place in most (70%) food premises visited, and in 52% it was documented. Most managers (89%) had received some form of food hygiene training. Documented cleaning schedules and cleaning records were only present in approximately half (55% and 44%, respectively) of the premises. Most did not have separate implements for cleaning raw and ready-to-eat food areas (67%), or stored cleaning equipment for high risk (ready-to-eat food) areas away from those used in low risk (raw, non ready-to-eat food) areas (70%). Deficiencies in the correct use of cleaning products, such as the minimum contact time for disinfectants, were identified. Surface samples (chopping/cutting boards, worktops, and food containers) and cleaning cloths with ACC levels in excess of 10(3) cfu/cm2, swab or ml were associated with premises that did not have management food hygiene training, hazard analysis, cleaning schedules or cleaning records in place, and with little or no confidence in the food business management of food hygiene as indicated by Local Authority Inspectors' Confidence in Management scores.

Microbiological study of ready-to-eat salad vegetables from retail establishments uncovers a national outbreak of salmonellosis.

The increasing availability of bagged prepared salad vegetables reflects consumer demand for fresh, healthy, convenient, and additive-free foods that are safe and nutritious. During May and June 2001 a study of retail bagged prepared ready-to-eat salad vegetables was undertaken to determine the microbiological quality of these vegetables. Examination of the salad vegetables revealed that the vast majority (3,826 of 3,852 samples; 99.3%) were of satisfactory or acceptable microbiological quality according to Public Health Laboratory Service microbiological guidelines, while 20 (0.5%) samples were of unsatisfactory microbiological quality. Unsatisfactory quality was due to Escherichia coli and Listeria spp. (not Listeria monocytogenes) levels in excess of 10(2) CFU/g. However, six (0.2%) samples were of unacceptable microbiological quality because of the presence of Salmonella (Salmonella Newport PT33 [one sample], Salmonella Umbilo [three samples], and Salmonella Durban [one sample]) or because of a L. monocytogenes level of 660 CFU/g, which indicates a health risk. In each case, the retailer involved and the UK Food Standards Agency were immediately informed, and full investigations were undertaken. Nineteen cases of Salmonella Newport PT33 infection were subsequently identified throughout England and Wales. The outbreak strain of Salmonella Newport PT33 isolated from the salad and from humans had a unique plasmid profile. Campylobacter spp. and E. coli O157 were not detected in any of the samples examined. The presence of Salmonella, as well as high levels of L. monocytogenes, is unacceptable. However, minimally processed cut and packaged salad is exposed to a range of conditions during growth, harvest, preparation, and distribution, and it is possible that these conditions may increase the potential for microbial contamination, highlighting the necessity for the implementation of good hygiene practices from farm to fork to prevent contamination and/or bacterial growth in these salad products.

Chitosan potentiates the antimicrobial action of sodium benzoate on spoilage yeasts.

AIMS: The objective of this study was to determine whether low concentrations of chitosan and benzoate in combination could be used to enhance the antimicrobial action of either compound alone against three spoilage yeasts in saline solutions. METHODS AND RESULTS: Saccharomyces exiguus, Saccharomycodes ludwigii and Torulaspora delbrueckii were suspended in 0.05 and 0.005% chitosan glutamate and 0.025% sodium benzoate, alone or in combination, in 0.9% saline solutions at pH 6.2 and 4.5. Survivor curves were constructed from viable counts determined periodically for up to 120 min. Chitosan at 0.005% almost doubled the extent of death caused by 0.025% benzoate alone, from about 1-2 log to about 2-4 log cfu ml(-1), depending on pH and target organism. CONCLUSIONS: Chitosan (0.005%) and 0.025% sodium benzoate acted synergistically against spoilage yeasts in saline solutions. SIGNIFICANCE AND IMPACT OF THE STUDY: These results suggest that the natural compound chitosan may be useful as an adjunct in the potentiation of the biocidal efficacy of antimicrobial compounds such as benzoates.

The microbiological examination of ready-to-eat organic vegetables from retail establishments in the United Kingdom.

AIMS: A microbiological study of uncooked ready-to-eat organic vegetables was undertaken to determine the microbiological quality of these vegetables on retail sale in the UK. METHODS AND RESULTS: Organic vegetables were collected and examined according to a standardized protocol. The majority (3185 of 3200; 99.5%) of samples were found to be of satisfactory/acceptable quality whilst only 15 (0.5%) were of unsatisfactory quality. Unsatisfactory results were due to Escherichia coli and Listeria spp. (not L. monocytogenes) levels in excess of 102 cfu g-1. CONCLUSIONS: The absence of pathogens (L. monocytogenes, Salmonella, Campylobacter and E. coli O157) and the low incidence (1.5%) of E. coli and Listeria spp. associated with these organic vegetables indicates that overall agricultural, hygiene, harvesting and production practices were good. SIGNIFICANCE AND IMPACT OF THE STUDY: There has been a significant expansion of the UK organic market since 1998/99. Of the various commodity sectors making up the organic market, fruit and vegetables is the largest sector and this has been reflected in an increased interest in their microbiological safety. This is the first study to provide information on the microbiological quality of organic vegetables.