Monitoring Salmonella, Campylobacter, Escherichia coli and Staphylococcus aureus in traditional free-range 'Label Rouge' broiler production: a 23-year survey programme

AIM

'Label Rouge' broiler free-range carcasses have been monitored since 1991, and broiler flocks since 2010, for contamination by the main foodborne zoonotic bacteria.

METHODS AND RESULTS

Initially, the monitoring plan mainly focused on the surveillance of Salmonella, and on indicators of the overall microbiological quality of free-range broiler carcasses such as Staphylococcus aureus and coliforms, but was extended in 2007 to include Campylobacter enumeration on carcasses and in 2010, to Salmonella in the environment of live birds. Salmonella contamination of free-range broiler carcasses rose to a peak of 16% in 1994 but less than 1% of carcasses are now regularly found to be positive. Indicators of the overall microbiological quality of carcasses are also improving. These results correlate with the low prevalence of Salmonella in free-range broiler breeding and production flocks, and with the continuous improvement of hazard analysis and critical control points in slaughterhouses, the implementation of a good manufacturing practice guide since 1997 and the application of EU regulations on Salmonella since 1998 in France. Regarding Campylobacter counts on carcasses, the situation has been improving continuously over the last few years, even if 2·5% of the carcasses are still contaminated by more than 1000 Campylobacter per g of skin.

CONCLUSIONS

Although the current control system focusing on Salmonella is based on firm epidemiologic data and offers effective means of control (e.g. slaughtering of positive breeder flocks), existing information on Campylobacter makes it more difficult to formulate an effective control plan for free-range broilers, due to their particular exposure to environmental contamination.

SIGNIFICANCE AND IMPACT OF THE STUDY

This long-term surveillance programme provided an extended view of the evolution of the contamination of free-range broilers and a direct measurement of the impact of mandatory and profession-driven interventions on the microbiological quality of carcasses.

Distribution of serotypes and genotypes of Salmonella enterica species in French pig production

The population of Salmonella found at various stages of pig production in France was characterised to analyse the distribution and spread of Salmonella in the pig production chain. We serotyped and genotyped by PFGE 174 isolates collected from breeding pigs from breeding farms, 163 collected from breeding pigs from production farms, and 325 collected from fattening pigs. Forty-seven serovars and 110 genotypes were identified. The major serovars were S Derby (263 isolates) and S Typhimurium (162 isolates). The percentage of S Derby isolates decreased slightly through the production system (44.3, 41.1 per cent and 36.5 per cent) and 79.1 per cent of the S Derby isolates were distributed in the five genotypes common to all three stages. The percentage of S Typhimurium isolates was high for slaughter pigs (40.8 per cent) and 43 of the 46 S Typhimurium genotypes were only identified at this stage. Distributions of S Derby and S Typhimurium between breeding and fattening pigs were different. S Derby was found throughout the pig production pyramid, suggesting that this serotype may be transmitted by the transfer of animals between herds. The presence of multiple S Typhimurium genotypes in fattening pigs suggests that there were many sources of contamination at this stage, with fattening pigs having higher levels of exposure and/or sensitivity to this serotype.

Biosecurity-based interventions and strategies to reduce Campylobacter spp. on poultry farms

The prevention and control of Campylobacter colonization of poultry flocks are important public health strategies for the control of human campylobacteriosis. A critical review of the literature on interventions to control Campylobacter in poultry on farms was undertaken using a systematic approach. Although the focus of the review was on aspects appropriate to the United Kingdom poultry industry, the research reviewed was gathered from worldwide literature. Multiple electronic databases were employed to search the literature, in any language, from 1980 to September 2008. A primary set of 4,316 references was identified and scanned, using specific agreed-upon criteria, to select relevant references related to biosecurity-based interventions. The final library comprised 173 references. Identification of the sources of Campylobacter in poultry flocks was required to inform the development of targeted interventions to disrupt transmission routes. The approach used generally involved risk factor-based surveys related to culture-positive or -negative flocks, usually combined with a structured questionnaire. In addition, some studies, either in combination or independently, undertook intervention trials. Many of these studies were compromised by poor design, sampling, and statistical analysis. The evidence for each potential source and route of transmission on the poultry farm was reviewed critically, and the options for intervention were considered. The review concluded that, in most instances, biosecurity on conventional broiler farms can be enhanced and this should contribute to the reduction of flock colonization. However, complementary, non-biosecurity-based approaches will also be required in the future to maximize the reduction of Campylobacter-positive flocks at the farm level.

A Selective Chromogenic Plate, YECA, for the Detection of Pathogenic Yersinia enterocolitica: Specificity, Sensitivity, and Capacity to Detect Pathogenic Y. enterocolitica from Pig Tonsils

A new selective chromogenic plate, YECA, was tested for its specificity, sensitivity, and accuracy to detect pathogenic Y. enterocolitica from pig tonsils. We tested a panel of 26 bacterial strains on YECA and compared it to PCA, CIN, and YeCM media. Detection of pathogenic Y. enterocolitica was carried out on 50 pig tonsils collected in one slaughter house. Enrichment was done in PSB and ITC broths. Streaking on YECA and CIN was done in direct, after 24H incubation of ITC, after 48H incubation of PSB and ITC. All the plates were incubated at 30°C during 24 hours. Presence of typical colonies on CIN and YECA was checked, and isolates were biotyped. Pathogenic Y. enterocolitica strains showed an important growth on YECA with small and red fuchsia colonies while biotype 1A exhibited very few violet colonies. Enrichment in ITC during 48H gave the best performance for detecting positive samples in pathogenic Y. enterocolitica, and YECA could detect directly pathogenic Y. enterocolitica strains (2, 3, and 4). Use of YECA in combination with ITC generates a time-saver by giving a positive test in 72H.

Risk factors associated withSalmonella entericasubsp.entericacontamination of chicken carcases in Senegal

The objective of this study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was administered to the slaughterers and samples of breast skin were taken to assess the Salmonella spp. status of chicken carcases. Results showed that 43.3% of the chicken batches were contaminated with Salmonella spp., with Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella spp. contamination of the live birds before slaughtering was related to contamination of the carcases after slaughtering. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of Salmonella contamination. One individual worker for each slaughtering stage was also associated with a decreased risk of Salmonella contamination. Using scalding water for plucking increased the risk of contamination. These results will help slaughterers to produce safer products for local consumers.

Effect of four antibiotic additives on the Salmonella contamination of chicks protected by an adult caecal flora

Avoparcin (10 mg/kg feed), bacitracin (50 mg/kg), flavomycin (5 mg/kg) and virginiamycin (20 mg/kg) were tested for their synergy or antagonism on the protective effect of an adult caecal flora administered to 1-day-old chicks. The chicks were challenged experimentally per os with 10(4) to 10(5)Salmonella typhimurium (a rifampicin-resistant strain) when aged 2 days. Chicks receiving avoparcin continuously in the feed had significantly more Salmonella in their caeca than control birds given feed containing no antibiotics; those receiving flavomycin had similar numbers to the controls whereas the groups fed on a diet supplemented with bacitracin or virginiamycin exhibited the lowest level of Salmonella carriage.

Prevalence and growth of Listeria monocytogenes in naturally contaminated cold-smoked salmon

AIM

To investigate Listeria monocytogenes contamination and behaviour in naturally contaminated French cold-smoked salmon (CSS).

METHOD AND RESULTS

Between 2001 and 2004, L. monocytogenes was detected in 104 of 1010 CSS packs, produced by nine French plants, with different prevalence (from 0% to 41%). The initial contamination, measured with a sensitive filtration method, was low (92% of contaminated products below 1 CFU g(-1)) and growth was limited.

CONCLUSION

Growth was consistent with results of a predictive model including microbial competition.

SIGNIFICANCE AND IMPACT OF THE STUDY

To be included in a quantitative risk assessment.

Risk factors for Campylobacter spp. colonization in French free-range broiler-chicken flocks at the end of the indoor rearing period

The aim of this cross-sectional survey was to identify risk factors for Campylobacter spp. colonization in French free-range broiler flocks at the end of the indoor rearing period (between 35 and 42 days old). Seventy-three broiler farms were studied from March 2003 to March 2004 in France. A questionnaire was administered to the farmers and samples of fresh droppings were taken to assess the flocks'Campylobacter status by bacteriology. Campylobacter species were determined by PCR. A logistic regression analysis was used to assess the influence of various factors on flocks'Campylobacter status. 71.2% of the sampled flocks excreted Campylobacter spp. before going out on the range. The risk of a flock being colonized with Campylobacter was increased in the spring/summer period (RR=1.8, p=0.02) and autumn (RR=2.2, p=0.02) compared to winter, on total freedom rearing farms (RR=3.3, p=0.04) in comparison with farms with a fenced run, when the first disinfection of the poultry-house was performed by the farmer (RR=2.4, p=0.04) instead of a hygiene specialist, when rodent control was carried out by a contractor (RR=1.8, p<0.01) and not by the farmer and when the farmer came into the house twice a day as opposed to three time a day or more (RR=1.5, p=0.02). Use of a specific gate for chick placement decreased the risk of a flock being colonized with Campylobacter (RR=0.5, p=0.01) in comparison with using the gate for manual disposure or the door of the change room.

Genetic characterization and antibiotic resistance of Campylobacter spp. isolated from poultry and humans in Senegal

AIMS

The main objectives of this study were to investigate the diversity of Campylobacter genotypes circulating in Senegal and to determine the frequency of antibiotic resistance.

METHODS AND RESULTS

Strains of Campylobacter jejuni isolated from poultry (n = 99) and from patients (n = 10) and Campylobacter coli isolated from poultry (n = 72) were subtyped by pulsed-field gel electrophoresis (PFGE). The pulsotypes obtained after digestion by SmaI and KpnI revealed a significant genetic diversity in both species, but without any predominant pulsotypes. However, farm-specific clones were identified in the majority of poultry houses (76.5%). Human and poultry isolates of C. jejuni had common PFGE patterns. High quinolone-resistance rates were observed for C. jejuni (43.4%) and C. coli (48.6%) isolates obtained from poultry.

CONCLUSIONS

The results showed a genetic diversity of Campylobacter between farms indicating multiple sources of infection; but specific clones had the ability to colonize the broiler farms. The antimicrobial resistance patterns were not related to any specific PFGE pattern suggesting that resistance was due to the selective pressure of antibiotic usage. Campylobacter with similar genotypes were circulating in both human and poultry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is important for the understanding of the epidemiology of Campylobacter in broiler farms in Senegal. It also emphasizes the need for a more stringent policy in the use of antimicrobial agents in food animals.

Evaluation of a French ELISA for the detection of Salmonella Enteritidis and Salmonella Typhimurium in flocks of laying and breeding hens

In France, the regular and compulsory detection of Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) in flocks of breeding and laying hens is based on bacteriological examination of environmental swabs and faeces samples. The aim of this study was to compare this bacteriological examination with a serological method (ELISA) developed in our laboratory. This ELISA was first evaluated by use of artificially infected hens. During these experimental infection studies, several groups of hens were inoculated with SE, ST, different vaccines and different Salmonella serovars to calculate the experimental parameters of our ELISA. Then, in a field study, 43 flocks were followed monthly using two bacteriological samples (environmental swab and pool of faeces) and 20 serological samples (sera or yolks). Twenty-seven flocks without SE or ST gave a negative serological response throughout their surveillance. Among the 10 various serovars different from SE and ST isolated in this study, S. Heidelberg, S. Agona and S. Hadar gave seropositive results in seven flocks. Consequently, this ELISA was not specific of SE and ST as it detected serovars sharing or not common antigens with SE and ST. Seropositive results were also obtained each month for two flocks where no Salmonella could be isolated. Finally, in seven flocks found infected with SE or ST, the positive ELISA results appeared later than the bacteriological detection. Therefore, for the detection of chicken flocks recently infected with SE or ST, bacteriological examination currently used in France seems to be more appropriate than this ELISA.

Epidemiological analysis of Salmonella enterica ssp. enterica serovars Hadar, Brancaster and Enteritidis from humans and broiler chickens in Senegal using pulsed-field gel electrophoresis and antibiotic susceptibility

AIMS

Salmonella Hadar, Salmonella Brancaster and Salmonella Enteritidis are the main Salmonella enterica ssp. enterica serovars isolated from poultry in Senegal. Our objective was to analyse the pulsed-field gel electrophoresis (PFGE) and antibioresistance patterns of strains belonging to these serovars and to assess the significance of broiler-chicken meat as a source of human infection.

METHODS AND RESULTS

A total of 142 Salmonella isolates were analysed: 79 were isolated from Senegalese patients with sporadic diarrhoea (11 S. Hadar, nine S. Brancaster and 59 S. Enteritidis) and 63 from poultry (30 S. Hadar, 17 S. Brancaster and 16 S. Enteritidis). The PFGE of XbaI- and SpeI-digested chromosomal DNA gave 20 distinct profiles for S. Hadar, nine for S. Brancaster and 22 for S. Enteritidis. Each serovar was characterized by a major pulsotype which was X3S1 in 42% of S. Hadar, X8S1 in 53.8% of S. Brancaster and X1S2 in 43% of S. Enteritidis isolates. Human and poultry isolates of Salmonella had common PFGE patterns. Antibiosensitivity tests showed multiresistance (more than two drugs) was encountered in 14.5% of S. Hadar and in 5% of S. Enteritidis isolates. Resistance to quinolones was considered to be of particular importance and 14.5% of S. Hadar isolates were found to be resistant to nalidixic acid. CONLCUSIONS: The sharing of similar PFGE profiles among isolates from humans and poultry provided indirect evidence of Salmonella transmission from contaminated broiler meat. But most of the Salmonella isolates remained drug sensitive.

SIGNIFICANCE AND IMPACT OF THE STUDY

Efforts are needed to eliminate Salmonella from poultry meat intended for human consumption. This study has also highlighted the importance of continuous surveillance to monitor antimicrobial resistance in bacteria associated with animals and humans.

Genomic diversity of Campylobacter coli and Campylobacter jejuni isolates recovered from free-range broiler farms and comparison with isolates of various origins

In many industrialized countries, the incidence of campylobacteriosis exceeds that of salmonellosis. Campylobacter bacteria are transmitted to humans mainly in food, especially poultry meat products. Total prevention of Campylobacter colonization in broiler flocks is the best way to reduce (or eliminate) the contamination of poultry products. The aim of this study was to establish the sources and routes of contamination of broilers at the farm level. Molecular typing methods (DNA macrorestriction pulsed-field gel electrophoresis and analysis of gene polymorphism by PCR-restriction fragment length polymorphism) were used to characterize isolates collected from seven broiler farms. The relative genomic diversity of Campylobacter coli and Campylobacter jejuni was determined. Analysis of the similarity among 116 defined genotypes was used to determine clusters within the two species. Furthermore, evidence of recombination suggested that there were genomic rearrangements within the Campylobacter populations. Recovery of related clusters from different broiler farms showed that some Campylobacter strains might be specifically adapted to poultry. Analysis of the Campylobacter cluster distribution on three broiler farms showed that soil in the area around the poultry house was a potential source of Campylobacter contamination. The broilers were infected by Campylobacter spp. between days 15 and 36 during rearing, and the type of contamination changed during the rearing period. A study of the effect of sanitary barriers showed that the chickens stayed Campylobacter spp. free until they had access to the open area. They were then rapidly colonized by the Campylobacter strains isolated from the soil.

Use of avilamycin for growth promotion and avilamycin-resistance among Enterococcus faecium from broilers in a matched case–control study in France

We assessed the putative link between avilamycin-resistant Enterococcus faecium carriage and avilamycin consumption in broilers. As part of the French programme of monitoring for antimicrobial resistance, broilers sampled at slaughterhouse in 1999 and 2000 and carrying avilamycin-resistant E. faecium were matched by slaughterhouse, slaughter month and production type (free-range, standard, light) with control broilers carrying avilamycin-susceptible strains. History of antibiotics consumption (either for growth promotion or therapeutic purpose) in the broiler flocks sampled was collected from the monitoring programme and consumption of each antibiotic class was screened as a potential risk factor. Avilamycin was a risk factor for avilamycin-resistant E. faecium carriage: OR=2.3.

Risk factors for contamination of ready-to-eat street-vended poultry dishes in Dakar, Senegal

Our objective was to investigate the Salmonella and Campylobacter contamination of traditional ready-to-eat street-vended poultry dishes and to assess the association of some restaurant characteristics and cooking practices with the contamination of these meals. One hundred and forty-eight street-restaurants were studied from January 2003 to April 2004 in Dakar. A questionnaire was submitted to the managers, and samples of ready-to-eat poultry dishes were taken. Salmonella spp. was isolated in 20.1% of the 148 street-restaurants studied and in 10.1% samples of poultry dishes. The most prevalent serovars isolated were Salmonella hadar, Salmonella enteritidis and Salmonella brancaster. Campylobacter jejuni was detected in only 3 restaurants and 3 poultry dishes. Not peeling and not cleaning vegetables and other ingredients during meal preparation (OR=3.58), dirty clothing for restaurant employees (OR=4.65), reheating previously cooked foods (OR=5.2), and no kitchen and utensils disinfection (OR=3.47) were associated with an increasing risk of Salmonella contamination. Adequate cooking procedures decreased the risk of Salmonella contamination (OR=0.15).

Risk factors associated with Salmonella enterica subsp. enterica contamination of chicken carcases in Senegal

This study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was answered by the slaughterers, and samples of breast skin were taken to assess the Salmonella status of chicken carcases. Results showed that 43.3% of the batches were contaminated with Salmonella, indicating Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella contamination of the carcases after slaughtering was related to contamination of the live birds. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of contamination. One individual worker for each slaughtering stage was also associated with a decreasing risk of contamination. Using scalding water for plucking the chicken carcases increased contamination risk. These results will help slaughters to produce safer products for local consumers.

Risk factors for Salmonella enterica subsp. enterica shedding by market-age pigs in French farrow-to-finish herds

Fattening-pigs carriers of Salmonella enterica are believed to be a main source of carcass and pork contamination at the later steps of the meat process. We did a prospective study in 2000-2001 in 105 French farrow-to-finish pig farms. In each farm, a batch of contemporary fattening pigs housed in the same room was followed throughout the fattening period. Salmonella shedding was assessed on environmental samples of faecal material (taken by means of pairs of gauze socks) analysed by classical bacteriological methods. 36.2% of the batches studied had at least one contaminated environmental sample and therefore were classified as Salmonella-shedding batches. Logistic regression was used to assess the association between managerial and hygiene practices and health status and the shedding risk at the end of the finishing period. Emptying the pit below the slatted floor after the previous batch of sows was removed and frequent removal of sow dung during the lactation period were protective. Presence of residual Salmonella contamination of the floor and pen partitions in the fattening rooms before loading the growing pigs also was a risk factor. The risk for Salmonella shedding at the end of the fattening period was increased when dry feed (versus wet feed) was provided during the fattening period. Lastly, Lawsonia intracellularis seroconversion and PRRSV seropositivity during the fattening period also was a risk factor for Salmonella shedding.

Risk assessment strategies for Europe: integrated safety strategy or final product control: Example of Listeria monocytogenes in processed products from pork meat industry

The European regulation 2160/2003 of November 17th, 2003 clearly shows the European strategy of zoonosis monitoring and control as an integrated approach, including the entire food production chain with a first application to Salmonella control in different animal species. This regulation is the consequence of a risk assessment performed with a "farm to fork" philosophy. European strategy is scarcely different from the American strategy, despite the fact that both were achieved by a quantitative risk assessment, as for instance, in the USA the control of Salmonella in eggs is supposed to be completed by refrigeration. Nevertheless, the EU will still have a final product control approach towards future regulations on microbiological criteria for foodstuffs. The final production monitoring and control with HACCP (93/43/EC) and microbiological criteria is the only one available for L. monocytogenes in foodstuffs. The purpose of this paper is to discuss alternative control strategies for L. monocytogenes in pig production including integrated risk assessment. In France, most of the food-borne outbreaks associated with L. monocytogenes in delicatessen were due to one particular group of strains belonging to serovar 4b and presenting a particular RFLP/PFGE (Restriction Fragment Length Polymorphism/Pulsed Field Gel Electrophoresis) profile. The outbreak itself is always associated with the initial contamination of a RTE ("ready to eat") product and re-contamination by inappropriate handling after cooking. Consequently, in most cases the RTE product is subject to inadequate refrigeration during an excessive shelf-life. The responsibility of the food industry and the consumer is clearly engaged during this scenario of foodborne diseases. The question is how to avoid the introduction of this particular strain of L. monocytogenes in the food chain. In a study we tried to evaluate the risk of pig carcass contamination at slaughterhouse level and to identify the main risk factors associated with the infection of live pigs. In most cases inappropriate cleaning and disinfection of surfaces were associated with the contamination of raw meat, but in some cases the introduction of epidemic strains in the food chain was also associated with primary production. Feeding with soup in piggeries seemed to select a particular microbial ecology associated to L. monocytogenes contamination of live pigs. The possible strategies that may be used to control L. monocytogenes in live pig production are not yet developed sufficiently to be included in the EC regulation but should be discussed in more detail.

Influence of bird strain on competitive exclusion of Campylobacter jejuni in young chicks

1. Newly hatched chicks of either layer or broiler strain were treated orally at regular intervals with either homologous or heterologous gut-flora preparations from young donor birds, in an attempt to prevent subsequent colonisation with Campylobacter jejuni by 'competitive exclusion' (CE). 2. Donors of 3 to 10 d of age were chosen to correspond with the period in which intensively reared poultry are least likely to become colonised with Campylobacter. 3. In two separate trials, material from donor layer hens (ISA Brown) protected male chicks of the same strain against a low (195 to 360 cfu/bird) Campylobacter challenge, but the same kind of material was ineffective when administered to chicks of a broiler strain (JA957). 4. Two further trials involved treatment preparations from young broilers, which failed to prevent Campylobacter colonisation of broiler chicks, even when colonisation occurred relatively slowly from a challenge of 90 to 94 cfu/bird. 5. It was concluded that any CE effect observed was strongly dependent on bird strain.

Risk factors for Salmonella enterica subsp. enterica infection in senegalese broiler-chicken flocks

Our objective was to assess the association of managerial practices, general hygiene and Salmonella infection in Senegalese broiler flocks. Seventy broilers farms were studied from January 2000 to December 2001 around Dakar. A questionnaire was submitted to the farmers and samples of fresh broiler droppings were taken. A 28.6% of the flocks were infected by Salmonella (mainly Hadar and Brancaster serovars). Salmonella infection of the previous flock (OR = 6.82) and of day-old chicks (OR = 3.73), frequent poultry farmers' visits (OR = 5.38) and keeping sick birds inside the farm (OR = 5.32) increased the risk of Salmonella infection. But, using antibiotics on day-old chicks (OR = 0.17) and a detergent for cleaning (OR = 0.16) decreased the risk.

Risk factors for Campylobacter spp. infection in Senegalese broiler-chicken flocks

Our objective was to identify the risk factors for Campylobacter infection in Senegalese broiler flocks. Seventy broiler farms were studied around Dakar from January 2000 to December 2001 around Dakar. A questionnaire was administered to the farmers, and samples of fresh droppings were taken to assess the flocks' Campylobacter status. About 63% of the flocks were infected by Campylobacter spp.; Campylobacter jejuni was the most-prevalent species (P < 0.05). An elevated risk of Campylobacter infection was associated with other animals (mainly laying hens, cattle and sheep) being bred in the farm, the farm staff not wearing their work clothing exclusively in the poultry houses, uncemented poultry-house floors and the use of cartons that transport chicks from the hatchery to the farm as feed plates (rather than specifically designed feed plates). Alternatively, thorough cleaning and disinfection of poultry-house surroundings and manure disposal outside the farm were associated with decreased flock risk.

Effect of two candidate genes on the Salmonella carrier state in fowl

Selection for increased resistance to Salmonella carrier-state (defined as the persistency of the bacteria 4 wk after inoculation) could reduce the risk for the consumer of food toxi-infections. The effects of two genomic regions on chromosomes 7 and 17 harboring two genes, NRAMP1 (SLC11A1) and TLR4, known to be involved in the level of chicken infection 3 d after inoculation by Salmonella were thus tested on a total of 331 hens orally inoculated at the peak of lay with 10(9) bacteria. The animals and their parents were genotyped for a total of 10 microsatellite markers mapped on chromosomes 7 and 17. Using maximum likelihood analysis and interval mapping, it was found that the SLC11A1 region was significantly involved in the control of the probability of spleen contamination 4 wk after inoculation. Single nucleotide polymorphisms (SNP) within the SLC11A1 and TLR4 gene were tested on those animals as well as on a second batch of 279 hens whose resistance was assessed in the same conditions. As the former was significantly associated with the risk of spleen contamination and the number of contaminated organs, SLC11A1 appears to be involved in the control of resistance to Salmonella carrier state. The involvement of the TLR4 gene was also highly suspected as a significant association between SNP within the gene, and the number of contaminated organs was detected.

Listeria spp. contamination in piggeries: comparison of three sites of environmental swabbing for detection and risk factor hypothesis

Listeria monocytogenes is a foodborne pathogen of major concern for public health in industrialized countries. Listeria carriage by pigs at the herd level could be a primary source for carcass contamination. Forty-seven finishing pig facilities were involved in the present study designed to compare three environmental swabbing sites in order to detect Listeria spp. in piggeries. Swabs were taken from the pen walls, the perianal regions of the pigs and the trough/feeder of the piggery premises. Listeria contamination of wet or dry feed given to the pigs was also investigated. The capacity of the various sampling sites for Listeria spp. detection were compared with a maximum likelihood estimation method. Listeria spp. were recovered in 74% of the pens studied and L. monocytogenes was detected in 15% of pens. With a specificity of 99%, sensitivity estimates (and 95% CI) of the Listeria spp. detection method were 93.4% (72.7-98.7) for pen walls, 73.1% (54.9-85.9) for pigs and 66.6% (48.6-80.7) for the trough/feeder. Listeria spp. were isolated from 84% of wet feed samples and 5% of dry feed samples. Listeria monocytogenes was found in 13% of wet feed samples. The type of feeding (wet versus dry) was associated (P < 0.001) with Listeria spp. contamination of both the pen and the feed. The results of this study confirm that Listeria spp., including L. monocytogenes, are present in pig facilities. Pen wall swabbing appears to be an effective way to assess Listeria spp. status of finishing pigs. The type of feeding (wet versus dry) could play a role in pig contamination.

Molecular epidemiology of Listeria monocytogenes isolates collected from the environment, raw meat and raw products in two poultry- and pork-processing plants

AIMS

In order to study the transmission of Listeria monocytogenes in a poultry and a pork meat plant, we analysed the contamination by this pathogen over several months.

METHODS AND RESULTS

Five hundred and two isolates of L. monocytogenes were collected and characterized by genotyping and serotyping. Thirty-seven genotypes were obtained by ApaI-restriction analysis-pulsed field gel electrophoresis (REA-PFGE) and 35 by SmaI-REA-PFGE and resulted in 50 combined genotypes. The tracing of the contamination in both plants showed that some clones were able to survive for several months. However, some other clones were found only during processing operations, were not detectable after cleaning and seemed to enter continuously into the plant.

CONCLUSIONS

Some L. monocytogenes strains may persist for a long period in the plant environment. Different genotypes can be associated with poultry as well as pork meat.

SIGNIFICANCE AND IMPACT OF THE STUDY

Listeria monocytogenes contamination can be due to contaminated raw materials, bacterial spread and also ineffective cleaning procedures.

Feasibility of fluorescent detection of pathogens on pork carcasses

The direct immunofluorescent detection of pathogens on pork skin is evaluated. Calibrate contamination of pork skin with Salmonella Typhimurium (ST) and Listeria monocytogenes (Lm) is developed in 2 h at 4 degrees C. Then a specific indirect immunofluorescent staining protocol is optimized in order to obtain specific and intensive signals able to be detected by electronic cameras (deported microscopy). Despite the individual staining of ST and Lm is possible on pork skin and is specific and bright, the deported microscopy failed to detect these particles. After respectively 3 and 6 h, we obtain micro-colonies of ST and Lm. Due to the limited power of the video camera used, only the microscope permits the detection on the skin. However, our work gives standard conditions to mime the pathogens contamination and staining directly on a biological matrix such as pork skin. This work is a first step in the development of direct and rapid detection of pathogens on biological matrix.

Campylobacter contamination in French chicken production from farm to consumers. Use of a PCR assay for detection and identification of Campylobacter jejuni and Camp. coli

AIMS

Campylobacter contamination in French chicken production from the farm to the consumer was determined using a PCR assay for bacteria detection and identification.

METHODS AND RESULTS

Samples were bird droppings from poultry houses, neck skins, livers, hearts, gizzards, wings, legs and escalopes from slaughterhouses and gizzards, legs, drumstick, breast and escalopes from a supermarket. Bacterial DNA extraction was performed after an enrichment step in a broth and was followed by PCR. An internal control (IC) was used for both DNA extraction and PCR. Campylobacter were detected in 79.2% of poultry houses. Of the 303 samples, 201 were Campylobacter-positive (i.e. 66.3%) including 43.2% faecal samples, 5.6% slaughterhouse samples and 17.5% supermarket samples. There was no significant difference between the molecular method and the conventional culture technique for Campylobacter detection whatever the samples. The sensitivity was 5 UFC g(-1) of samples and 1.5 x 10(3) UFC ml(-1) of enrichment broth. The use of IC revealed PCR inhibition in 13 samples and problems in the DNA extraction in five samples.

CONCLUSION

Significant Campylobacter contamination affects all stages of French chicken production.

SIGNIFICANCE AND IMPACT OF THE STUDY

The understanding of Campylobacter contamination at different levels of chicken production and the determination of the best place(s) for intervention are important for significantly decreasing Campylobacteriosis. Our technique is rapid and can be used on different chicken samples for Campylobacter detection and identification.

Risk factors for Campylobacter spp. contamination in French broiler-chicken flocks at the end of the rearing period

Our objectives were to identify risk factors for contamination of French broiler flocks by Campylobacter. We used 75 broiler farms in western France. A questionnaire was administered to the farmers and samples of fresh droppings were taken to assess the Campylobacter status of the broiler flocks. 42.7% of the flocks were positive for Campylobacter spp. The risk of contamination of the broiler flocks by Campylobacter was increased in summer/autumn, in houses with static air distribution, when two or more people took care of the flock, in poultry farms with three or more houses and when the drinking water for the chickens was acidified. The presence of litter-beetles in the change room also increased the risk of contamination. The administration of an antibiotic treatment following a disease decreased the risk of a flock being contaminated by Campylobacter.

Tracing of Salmonella spp. in two pork slaughter and cutting plants using serotyping and macrorestriction genotyping

AIMS

The origin of Salmonella contamination of pork products is not well established. In order to further this knowledge, the transmission of Salmonella spp. from live pigs to pork cuts was investigated in two pork slaughter and cutting plants.

METHODS AND RESULTS

Salmonella spp. were isolated from both pork (pigs, carcasses, cuts) and the environment before and during slaughterhouse activities. Eight serotypes were identified. XbaI and SpeI macrorestriction distinguished 20 genotypes of Salmonella Typhimurium and 16 genotypes of Salmonella Derby. A major cluster of Salmonella Typhimurium genotypes was common to both plants and all pig-related genotypes, while a predominant pig-related Salmonella Derby genotype was common to both plants.

CONCLUSION

None of the Salmonella strains persisted for long periods in the pork-processing environments.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work shows that contaminated live pigs, because of bacterial spread due to the process and ineffective cleaning procedures, are involved in Salmonella contamination.

Some safety aspects of Salmonella vaccines for poultry: in vivo study of the genetic stability of three Salmonella typhimurium live vaccines

Live vaccine strains of Salmonella should be avirulent, immunogenic and genetically stable. Some isolates of three commercially available live vaccine strains of Salmonella typhimurium, sampled during a study on their persistence in a vaccinated flock of chickens, were analyzed for genetic stability using macrorestriction analysis of their genome. Two out of the three vaccine strains showed genetic instabilities. Two of the 51 isolates of Zoosaloral vaccine strain and nine of the 32 analyzed isolates of chi(3985), a genetically modified organism, were variants and showed different macrorestriction profiles.

Some safety aspects of salmonella vaccines for poultry: distribution and persistence of three Salmonella typhimurium live vaccines

The purpose of this study was to analyze the safety characteristics of three commercially available live Salmonella vaccine strains (vacT, Zoosaloral, and X3985) in relation to their persistence in individual animals but also within a flock and in the environment. In a first experiment, the digestive and systemic distributions in chickens were followed for 10 days in individually reared chickens that were orally inoculated at 1 day of age. Strain X3985 quickly disappeared from the digestive tract but remained in the liver until the end of this experiment, whereas strains vacT and Zoosaloral colonized the liver as well as the gut for 10 days. In the second trial, behavior of the vaccine strains was studied in groups of 20 chickens during 10 wk after a single oral administration to individual birds. Strain vacT remained in the environment of inoculated animals for 4-5 wk. Six weeks after the inoculation, vacT was not recovered from internal organs such as liver and spleen, and vacT disappeared from the digestive tract between the sixth and the 10th weeks. Comparatively, both Zoosaloral and X3985 vaccine strains persisted longer in the environment (8 wk at least). Of the vaccine strains, X3985 showed the greatest colonization of both systemic and digestive organs.

Physicochemical surface properties of five Listeria monocytogenes strains from a pork-processing environment in relation to serotypes, genotypes and growth temperature

Physicochemical surface properties, related to electrostatic, van der Waals and Lewis acid-base interactions, of five Listeria monocytogenes strains isolated from pork-processing environments were determined after two subcultures at 37 degrees C and a final culture at three temperatures: 37, 10 and 4 degrees C. Three strains (Lm1, Lm114 and Lm191) were genetically related while two were unrelated (Lm25 and Lm74) according to ApaI-macrorestriction and pulsed-field gel electrophoresis (PFGE) typing. Listeria monocytogenes cell surfaces were generally negatively charged regardless of pH and tended to be hydrophilic due to a basic character. However, variable physicochemical surface properties of the five Listeria monocytogenes isolates were observed after growth at 37 degrees C. After growth at 10 degrees C, the three genetically related isolates exhibited similar surface properties and were slightly more hydrophilic and basic than the others. After growth at 4 degrees C, the five isolates displayed the same weak affinity for all kinds of solvents and low electrophoretic mobility values. A sharp decrease of temperature and subsequent growth of various Listeria monocytogenes strains resulted in loss of the physicochemical surface property variability, which may suggest the role of common chill adaptation mechanisms affecting surface properties.

Listeria monocytogenes in pork slaughtering and cutting plants. Use of RAPD, PFGE and PCR-REA for tracing and molecular epidemiology

In order to determine the origin of pork cuts contamination by Listeria monocytogenes, 287 isolates, collected from five French pork slaughtering and cutting plants, from live pigs to pork cuts, were characterised using three molecular typing methods: random amplification of polymorphic DNA (RAPD) carried out with five different primers, genomic macrorestriction using ApaI with pulsed-field gel electrophoresis (PFGE) and a PCR-restriction enzyme analysis (PCR-REA) based on the polymorphism existing within the inlA and inlB genes. Results obtained from RAPD and PFGE were closely related and distinguished respectively 17 RAPD types (r1-r17) and 17 PFGE types (a1-a17) among the 287 isolates, whereas the PCR-REA analysis only yielded two profiles (p1 and p2). Considering the combined results obtained with the three molecular typing methods, 19 Listeria monocytogenes genotypes (1-19) were distinguished. Serotyping led at least four serotypes being distinguished: 1/2a, 3a, 1/2c and 3c. The application of genotyping identified the predominance of a Listeria monocytogenes strain of type (1) and other very closely related ones (5, 9, 10, 12, 13, 14, 16 and 19) which were present on pork as well as in the environment within the five investigated plants. This study also pointed out the presence of these closely related Listeria monocytogenes strains over a 1-year period in the environments of two plants, even after cleaning and disinfection procedures. This highlights the possibility for some Listeria monocytogenes strains to persist in pork processing environments and raises the problem of the efficiency of cleaning and disinfection procedures used in pork slaughterhouses, chilling and cutting rooms.

Molecular characterization of the diversity of Campylobacter spp. isolates collected from a poultry slaughterhouse: analysis of cross-contamination

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.

Development of a m-PCR assay for simultaneous identification of Campylobacter jejuni and C. coli

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.

Identification by a multiplex PCR-based assay of Salmonella typhimurium and Salmonella enteritidis strains from environmental swabs of poultry houses

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%.

An immunoconcentration-PCR assay to detect Salmonella in the environment of poultry houses

An immunoconcentration-PCR assay was developed for the rapid and specific detection of Salmonella. This assay was evaluated against a conventional bacteriological method for the detection of Salmonella from environmental swabs of poultry houses. The 120 samples investigated were pre-enriched in phosphate buffered peptone water and Salmonella was separated by an immunoconcentration process using an automated system (VIDAS bioMérieux, Marcy l'Etoile, France) prior to PCR. The specificity of the assay was high as no false-positives were found. The sensitivity of the assay was 70%. The correlation between the ICS-PCR assay and the bacteriological method was 84%.

Evaluation of a multiplex PCR assay for simultaneous identification of Salmonella sp., Salmonella enteritidis and Salmonella typhimurium from environmental swabs of poultry houses

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.

Measurement of the residual contamination of post-weaning facilities for pigs and related risk factors

A survey was designed in France to assess residual contamination in post-weaning rooms within the 2 h prior to restocking when all the pigs of the previous batch had been removed (all in-all out) and after application of the 'in use' cleaning procedures. The protocol was based on the results of a pilot study and was considered 'a good compromise'. Special agar plates (Rodac plates) with a prominent agar medium surface were prepared and used to collect the bacteria. They were applied by impression onto the floors and the partitions between the pens. In all, 24 plates were applied per room. The culture medium was VRBG which mainly permits the growth of enterobacteria. The plates were incubated for 24 h (37 degrees C) and the Colony-Forming Units (CFU) counted. After sampling, measurements were made and information collected from the farmer to obtain potential explanations for the resulting microbiological data. The same scientist sampled 129 post-weaning rooms with slatted floors. Of the 3045 plates, 18.4% were negative and 12.8% were heavily colonized (> 300 CFU). A score combining six criteria based on the counts was produced, and indicated a wide spread of the rooms. The profile of circumstances associated with the different levels of the score was extracted. The following points should be respected to achieve low residual contamination: removal of the slurry from the pit below the slatted floor; damping to be started soon after pig removal; prolonged damping; thorough washing; disinfecting soon after washing; and attention to the recommended dosage of disinfectant. Smooth surfaces were found to be less contaminated than rough ones. It is concluded that cleaning and disinfecting operations must not be considered as minor tasks and should clearly be integrated into the process of pig production.

Development of a multiplex PCR gene fingerprinting method using gyrA and pflA polymorphisms to identify genotypic relatedness within Campylobacter jejuni species

The two genes gyrA and pflA, whose sequence variability had been previously described, were evaluated separately for their potential value in discriminating strains of Campylobacter jejuni. A single method was then developed by which the two loci were simultaneously amplified using a multiplex PCR procedure, and banding patterns were generated using a pre-selected set of restriction endonuclease enzymes. The method was applied to 18 strains of Camp. jejuni from different poultry sources varying in geographical origin and year of isolation. Results were combined and compared by means of numerical analysis with the classification obtained by flaA-typing and macrorestriction SmaI and KpnI. The usefulness of PCR fingerprinting of the gyrA/pflA genes for rapid ordering of strains by genotypic relatedness and providing additional information for estimating the degree of linkage between strains was demonstrated.

Comparison of five typing methods for the epidemiological study of Listeria monocytogenes

Five typing methods were compared in a study designed to adapt a strategy for epidemiologically typing large numbers of Listeria monocytogenes strains. The methods studied were serotyping, electrophoretic typing of esterases (zymotyping), restriction fragment length polymorphism of ribosomal DNA (ribotyping), random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE). Data were analysed by computer-assisted statistical analysis. Included in the analysis were 35 strains of L. monocytogenes, including 14 epidemic strains isolated during outbreaks in France in 1992 and 1993, and 21 strains isolated from food and the environment. Five serotypes, eight zymotypes, ten ribotypes, 13 RAPD patterns and 12 PFGE patterns were identified among the 35 strains. The most discriminating combination of typing methods was ribotyping and PFGE typing [27 types, discriminatory index (D.I.) = 0.978]. A factorial analysis of correspondence for each method differentiated the epidemic strains from the environmental strains. This study shows that computer-assisted statistical treatment of the data, combined with the use of discriminating typing methods, is a powerful tool for the epidemiological analysis of Listeria monocytogenes.

Antimicrobial efficacy of AvGard carcase wash under industrial processing conditions

1. The efficacy of the AvGard Trisodium Phosphate (TSP) immersion carcase wash process was evaluated during 5 industrial trials against Salmonella, Enterobacteriaceae, thermotolerant coliforms and total aerobic count. The effect against Pseudomonas was also studied in the first 3 trials. 2. Dramatic reductions in Salmonella incidence were seen using a whole carcase rinse method. In 4 of the 5 trial sites, only one positive sample was found after AvGard treatment (average 0.5% incidence), in spite of an average control incidence of 57.7%. In the 5th site, a water-chilled broiler plant, an average control incidence of 74.0% was reduced to 9.4% after AvGard treatment. 3. In the latter case, Most Probable Number (MPN) analyses were performed on some of the Salmonella positive samples taken from the control and post-treatment series; the average MPN count per carcase on controls was 115, whereas for AvGard treated birds the figure was only 0.6 per carcase, a greater than 2 log reduction. 4. In addition, AvGard treatment gave average log reductions for all trials of: Enterobacteriaceae; 2.5 log; Coliforms; 2.7 log, and Total Aerobic Count; 1.1 log, leading to carcases substantially free of Gram negative pathogens. 5. Pseudomonas was reduced by an average of 1.7 log in the first 3 trials, dramatically reducing the carcase loading of this important spoilage organism.

Development of a new culture medium for the rapid detection of Salmonella by indirect conductance measurements

The main difficulties in conductance medium development are to allow Salmonella to grow and produce a conductance signal while impeding growth of related species such as Escherichia coli and Citrobacter freundii. Various selective agents were screened for these capacities and a new medium was derived, named KIMAN (Whitley Impedance Broth basal medium supplemented with three selective components: novobiocin, malachite green and potassium iodide). This medium supported the growth of Salmonella serotypes and inhibited non-salmonella strains in pure cultures.

Listeriosis outbreak associated with the consumption of rillettes in France in 1993

An outbreak of listeriosis involving 38 patients occurred in France between 18 June and 5 October 1993. The epidemic clone was characterized by serovar 4b, phagovar 2671:108:312, and DNA macrorestriction patterns 12 and 13. Thirty-one case-patients were materno-neonatal patients and 7 patients were nonpregnant adults. Preliminary analysis of a case-control study implicated a pork product, rillettes, of a particular brand (odds ratio, 18; 95% confidence interval, 2.2-208) as the vehicle of infection. Rillettes is a ready-to-eat food prepared with ham meat cooked with grease. The implicated lots of rillettes were recalled in mid-August, and the French authorities issued a warning to the general public. Microbiologic analysis of unopened plastic cans of rillettes confirmed the results of the case-control study 3 weeks after the recall. Final analysis showed that the rillettes was the major vehicle of the outbreak but suggested that other brand A meat products could also have been involved.

Effects of AvGard treatment on the microbiological flora of poultry carcases

1. The efficiency of the AvGard (or Assur-Rince in the USA) trisodium phosphate poultry carcase decontamination process was evaluated during both manual and industrial trials against total aerobic mesophilic count (TAMC), thermotolerant coliforms, Pseudomonas, Enterobacteriaceae, Campylobacter, Listeria monocytogenes and Salmonella. 2. The TSP treatment proved to have significant effects on the bacterial decontamination of poultry neck skin, lowering the contamination by a factor of about 10 for TAMC and of 100 for Coliform and Pseudomonas. 3. Numeration of Salmonella with an innovative miniaturised most probable number method has proved that the effect upon these micro-organisms was also close to 2 log10 reduction. 4. The effect of TSP treatment on the ecological balance of psychrotrophic bacterial flora was also investigated to study the origin of the shelf-life flora of treated carcases (Pseudomonas being reduced to the limit of detection) and to ascertain whether L. monocytogenes might gain a competitive advantage. In fact AvGard reduced the number of L. monocytogenes on poultry carcases. 5. As a consequence of the virtual elimination of the Pseudomonas usually present, Brochothrix thermosphacta became the main species responsible for putrefaction. 6. Because the growth rate of Brochothrix thermosphacta was greater than that of L. monocytogenes at refrigeration temperature, it was considered that putrefaction would occur before the emergence of large numbers of L. monocytogenes.