Effect of time in lairage on caecal and carcass salmonella contamination of slaughter pigs

A longitudinal study of the effect of time spent in lairage on salmonellas in the caecum and on the skin surface of 450 slaughter pigs from a single producer was conducted. Pigs were tested in 6 groups at 2 abattoirs, with one-third of a group being slaughtered after 18 h, one-third after 42 h and one-third after 66 h spent in lairage. The salmonella isolation rate from caeca and carcass surfaces increased significantly with increasing time spent in lairage. Salmonellas were isolated from the caeca of 18.5% of pigs held less than 24 h in lairage, 24.1% of pigs held a further 24 h and 47.7% of pigs held for 66 h in lairage before slaughter. The salmonella isolation rates from carcasses were 9.3%, 12.8% and 27.3% for the same groups. Thirteen salmonella serotypes were isolated from the caecal contents and carcasses over the 6 weeks of the trial. One abattoir had a higher salmonella isolation rate from pigs than the other and this was probably related to lairage management. It appeared that lairage is an important factor in the manipulation of the salmonella contamination of pig carcasses.     

Salmonella in pig carcasses for human consumption in Hong Kong: a study on the mode of contamination.

A very high proportion (75%) of the pigs slaughtered in Hong Kong were found to be infected with salmonellas. Seven serotypes including Salmonella choleraesuis were isolated but the majority (91%) were S. anatum and S. derby. These serotypes, especially S. anatum and S. derby, had been isolated frequently from clinical cases, symptomless carries and in this study from abattoir workers, suggesting that the pig was a significant source for human salmonella infection. The majority of pigs slaughtered are imported and the high level of apparent infection was thought to be due to cross-infection during transport of the pigs under stress. S. anatum and S. derby were also isolated from pigs at 60 degreesC for 5 min caused no great reduction in the degree of superficial contamination. The two predominant serotypes were isolated from the tank and from drain swabs, and also from the latter held under scalding tank conditions. Thus, in spite of the introduction of hygienic slaughter under modernized conditions employing an automatic conveyance system 55% of the carcases were superficially contaminated after dressing before despatch to customers. Control of infection before slaughtering would appear crucial and a more thorough rinsing or washing of the dressed carcasses desirable.     

河南省肉鸡养殖和屠宰加工过程中沙门菌污染监测

目的了解河南省肉鸡养殖和屠宰过程中沙门菌的污染状况,为食品安全风险评估提供数据支持。方法选择肉鸡产品销量占河南省市场60%以上的养殖场和屠宰场,于2010年6~10月份在肉鸡养殖环节采集成年鸡肛拭子、在屠宰环节采集鸡酮体按照GB4789.4-2010进行沙门菌定性或/和定量检测。结果共检测368只鸡肛拭子,沙门氏菌检出率8.7%;186份鸡酮体,检出率24.2%。鸡肛拭子检出率最高的月份是7、8月、鸡酮体检出率较高的月份分布在6、8月份;两类样本检出沙门菌血清型前3位一致,均为印第安纳、肠炎和哈达尔沙门菌。鸡酮体沙门菌污染量较低,91.1%在10MPN/g以下。检出沙门菌均具有invA基因。肉鸡胴体和活鸡肛拭子分离沙门菌均具有严重的多重耐药现象,活鸡肛拭子沙门菌较胴体沙门菌耐药严重。结论肉鸡沙门菌的污染取决于肉鸡携带沙门菌和养殖环境中沙门菌的污染状况,并通过屠宰过程使污染扩大化和复杂化。宰后酮体鸡沙门菌的含量不高,但是沙门菌的存在将对食品安全造成潜在危害。分离沙门菌菌株耐药现象严重,提示政府要加大监测力度,养殖部门要合理使用抗生素。     

Salmonella in the intestinal tract and associated lymph nodes of sheep and cattle.

The distribution of salmonellas along the gastrointestinal tract and in associated lymph nodes were studied in 100 sheep and 100 cattle at slaughter. Animals were chosen from those slaughtered on the first day of the week, since this meant that they were likely to have been held at the abattoir for several days and thus to be at high risk of salmonella infection. The contents of the rumen, abomasum, ileum, caecum and rectum were sampled, together with the lymph nodes draining each of these sites. Of the cattle, 77 were carrying salmonellas, including 61 with infected lymph nodes, whereas only 43 sheep were infected, 14 of them with infections in the nodes. The lower prevalence in sheep than in cattle might be explained by a shorter time between leaving the property and slaughter. In both species, within the gastrointestinal tract salmonellas were most frequently found in the caecum and rectum and least frequently in the abomasum. In cattle salmonellas were frequently present, usually in large numbers, in the lymph nodes draining the ileum, caecum and colon, but rarely in the ruminal and abomasal nodes; however this difference was not apparent in sheep. Over 70% of infected animals yielded more than one serotype, the maximum number isolated from any one animal being ten.     

The incidence and level of contamination of British fresh sausages and ingredients with salmonellas

A five-tube most probable number (MPN) method, with the pre-enrichment and enrichment stages, was used in a study of the incidence of salmonella contamination of British fresh sausages and the ingredients used in their manufacture. All samples were taken from a large factory in the course of routine production. There was an incidence of 65% contamination of pork (n = 20) and 55% (n = 20) in pork and beef sausages. The incidences of contamination of uncooked ingredients varied from 95% for mechanically recovered meat (n = 20) to 10% for another type of meat. Cooked and/or dried ingredients were rarely contaminated with these organisms, and when contamination occurred, coliforms were also important. The numbers of salmonellas isolated ranged from 7-40 for pork sausages, from 8-24 for beef and pork sausages and from 0.8-378 organisms/g for ingredients. The following salmonella serotypes were isolated (ranked in descending order or incidence): S. derby, S. dublin, S. newport, S. stanley. S. typhimurium, S. heidelberg, S. infantis and S. agona.     

The incidence and level of contamination of British fresh sausages and ingredients with salmonellas.

A five-tube most probable number (MPN) method, with the pre-enrichment and enrichment stages, was used in a study of the incidence of salmonella contamination of British fresh sausages and the ingredients used in their manufacture. All samples were taken from a large factory in the course of routine production. There was an incidence of 65% contamination of pork (n = 20) and 55% (n = 20) in pork and beef sausages. The incidences of contamination of uncooked ingredients varied from 95% for mechanically recovered meat (n = 20) to 10% for another type of meat. Cooked and/or dried ingredients were rarely contaminated with these organisms, and when contamination occurred, coliforms were also important. The numbers of salmonellas isolated ranged from 7-40 for pork sausages, from 8-24 for beef and pork sausages and from 0.8-378 organisms/g for ingredients. The following salmonella serotypes were isolated (ranked in descending order or incidence): S. derby, S. dublin, S. newport, S. stanley. S. typhimurium, S. heidelberg, S. infantis and S. agona.     

The herring gull Larus argentatus as a carrier of salmonella.

The proportion of salmonella carriers among town-nesting herring gulls increased significantly from 2.1% in 1975-6 to 8.4% in 1979. The range of serotypes carried by herring gulls was similar to that causing infection in man, and it is likely that the gulls ingest these serotypes when feeding at untreated sewage outfalls on the coast. This is supported by the proportion of salmonella carriers being higher among first-year birds (9.7%) than among older birds (2.0%), as it is known that higher proportions of immature herring gulls feed on the coast. Herring gulls carrying salmonellas appeared healthy at the time of capture and at a later date it was assumed that they were not themselves infected. However, their habit of congregating in large numbers on reservoirs and rubbish tips and also at resting sites on farmland often far from feeding and roosting areas, multiplies the pollution problem and increases the potential health hazard for both man and farm stock. Herring gulls feed at a variety of sites and fly many miles from food source to food source and from feeding areas to the roost. Thus, even within the same day, there is the possibility of the transfer of salmonellas over a much wider area than previously considered.     

Cockroaches (Blatta and Periplaneta species) as reservoirs of drug-resistant salmonellas

A total of 221 cockroaches (Blatta and Periplaneta spp.), collected in hospitals, houses, animal sheds, grocery stores and restaurants, in various parts of South Kanara District, a south-west coastal region of India, were studied bacteriologically for the presence of various salmonellas. Salmonellas were isolated from 4.1% of these cockroaches. Nine strains of salmonellas were recovered, belonging to five serotypes--Salmonella bovismorbificans, S. oslo, S. typhimurium, S. mbandaka and S. braenderup, the former two being the commonest serotypes. All salmonellas were resistant to one or other of 11 antibacterial drugs used in the susceptibility test. Isolation of salmonellas from cockroaches collected from the livestock premises and human dwellings suggested that they may act as significant reservoirs of salmonella in nature. Recovery of serotypes, phage types and R-types that were commonly isolated from humans and animals of this locality, suggested a transmission role for cockroaches. By harbouring potentially pathogenic, drug-resistant salmonellas, these wandering arthropods may pose dangerous infective hazards to humans and animals.     

Observations on environmental contamination in a microbiological laboratory.

Contamination of a laboratory environment with pathogenic or non-pathogenic micro-organisms may be relevant to safety of technicians and quality of technical performance. Two widely separated incidents in 1968 and 1974 initiated a study of aspects of the laboratory environment. Water-baths, water of syneresis and portions of salmonella cultures spurting out of the sterilizing flame were examined. The water of water-baths was shown to be contaminated from the fluid cultures incubated in them. This raised questions of potential cross-contamination and reporting of false positives. Water of syneresis was sometimes contaminated with salmonellas. A few quantitative counts were made. The range of counts varied between 16 salmonellas per ml. and 13,000,000 salmonellas per ml. Five hundred portions of salmonella cultures and 571 portions of Shigella sonnei cultures which had spurted from the sterilizing flame were examined. All these samples failed to grow salmonellas or shigellas. Precautions necessary to avoid environmental contamination are briefly discussed.     

Importation of beef from countries infected with foot and mouth disease: a review of risk mitigation measures.

Risk mitigation measures to reduce the risks associated with importing beef from countries affected by foot and mouth disease (FMD) consist of controls at the farm of origin, inspection of slaughterhouses and maturation and deboning of carcasses. This assessment evaluates the effect of these measures on the mitigation of the risks presented by meat from cattle with FMD, for each of the different stages of the disease. The four disease stages considered are the incubation period, the period of clinical signs, convalescence and the carrier stage. Efficient animal health systems, disease surveillance, and ante-mortem and post-mortem inspection of all cattle effectively reduce the risk of FMD transmission from cattle slaughtered during the period of clinical signs or convalescence. These measures fail if the cattle are slaughtered during the incubation period, because of the absence of clinical signs. Cattle in this stage of the infection are likely to be viraemic, with FMD virus present in the skeletal muscles. Maturation of the carcasses of viraemic cattle reduces the risk of virus presence in the beef. In addition, deboning and removal of the principal lymph nodes and large blood vessels eliminate a source of FMD contamination of the beef. However, the slaughter of viraemic cattle creates an additional hazard of gross environmental viral contamination of the slaughterhouse facilities. Therefore, the maturation process may create a false sense of security, and the emphasis should instead be placed on disease surveillance within the infected zone and on the farms of origin, to prevent the slaughter of herds that are incubating FMD. Cattle slaughtered during the carrier stage do not pose a risk for the international beef trade.     

The serological relationship between Brucella spp., Yersinia enterocolitica serotype IX and Salmonella serotypes of Kauffmann-White group N.

The serological relationship between Brucella spp., Yersinia enterocolitica IX, and the group N salmonella serotypes S. godesberg, S. landau, S. morehead, S. neusdorf, S. soerenga and S. urbana was examined using agglutination, antiglobulin, complement fixation, immunodiffusion and fluorescent antibody methods. Antisera to the group N salmonella serotypes all reacted to significant titres in agglutination and complement fixation, but not antiglobulin or immunodiffusion tests with smooth brucella antigens. These antisera also reacted in agglutination, but not antiglobulin, tests with Y. enterocolitica IX. They did not react significantly in any tests with rough brucella antigens. Conversely, antisera to smooth Brucella spp. agglutinated group N salmonellas to low titre and Y. enterocolitica IX to titres similar to those given against the homologous strain. Antiserum to Y. enterocolitica IX on the other hand reacted with smooth brucella antigens to high titre in agglutination, complement fixation and antiglobulin tests, and with the group N salmonella antigens to substantial titres in agglutination tests. In direct fluorescent antibody tests, smooth Brucella strains and Y. enterocolitica IX reacted strongly with FITC-labelled antibody to Br. abortus whereas the group N salmonella strains reacted weakly. In tests with monospecific antisera to the A and M determinants of Br. abortus and Br. melitensis respectively, Y. enterocolitica IX reacted only with the antiserum to the A determinant whereas group N salmonellas reacted to low titre with both A and M antisera. The results of cross-absorption tests confirmed this relationship and suggested that the O30 antigens of group N salmonella serotypes contained antigenic determinants similar to, but not identical with, the antigenic structure shared by smooth Brucella spp. and Y. enterocolitica IX.     

Salmonellosis in two dairy herds associated with a sewage farm and water reclamation plant

Two dairy herds, situated on a sewage farm, were monitored for the presence of salmonellas following outbreaks of Salmonella dublin infection. In addition an S. dublin control scheme, which involved examination of adult animals and calf vaccination, was instigated. During the period 1975-84, 12 salmonella serotypes and 10 phage types of S. typhimurium were isolated from the cattle and their environment although their presence was seldom associated with disease. Two adult S. dublin excreters were detected but it was concluded that none of the tests employed to examine the adult animals was sensitive enough. The prevalence of disease in the calves was low and although vaccination may have been beneficial it did not eradicate S. dublin infection. Thus S. dublin persisted in adults and calves during the 8-year period but its presence was seldom associated with disease. The results are discussed with regards the disease risk to animals from the agricultural use of sewage sludge and the public health aspects.     

Salmonellosis in two dairy herds associated with a sewage farm and water reclamation plant.

Two dairy herds, situated on a sewage farm, were monitored for the presence of salmonellas following outbreaks of Salmonella dublin infection. In addition an S. dublin control scheme, which involved examination of adult animals and calf vaccination, was instigated. During the period 1975-84, 12 salmonella serotypes and 10 phage types of S. typhimurium were isolated from the cattle and their environment although their presence was seldom associated with disease. Two adult S. dublin excreters were detected but it was concluded that none of the tests employed to examine the adult animals was sensitive enough. The prevalence of disease in the calves was low and although vaccination may have been beneficial it did not eradicate S. dublin infection. Thus S. dublin persisted in adults and calves during the 8-year period but its presence was seldom associated with disease. The results are discussed with regards the disease risk to animals from the agricultural use of sewage sludge and the public health aspects.     

Salmonella infection in chicks following the consumption of artificially contaminated feed

Poultry feed was contaminated artificially with either Salmonella kedougou or S. livingstone using a two-stage mixing process. Intestinal infection became established in a small proportion of birds when feed containing between 0.1 and 0.3 salmonellas/g was given continuously for 2 or 3 weeks from the day of their purchase as 'day-olds' while nearly all birds became infected when the feed contained 100-300 salmonellas/g. Between these limits a dose response was demonstrated in that the proportion of birds becoming colonized with salmonellas increased as the numbers of salmonellas added to feed was increased. Nalidixic acid-resistant strains of both serotypes were used to facilitate the recovery of organisms. The isolation rate was higher from dilutions of caecal contents inoculated directly onto brilliant green agar supplemented with nalidixic acid than it was from swabs of cloacal faeces, even when an enrichment technique was used. This observation confirms that the incidence of salmonella carriage in flocks will be under-estimated if only cloacal faeces are cultured. Of the two serotypes used S. kedougou proved the more efficient colonizer although for both serotypes variation in infection rates was demonstrated in different groups of birds given feed containing comparable numbers of salmonellas.     

Survey of Trichinella spp. infection in pigs from commercial piggeries in Zimbabwe

Trichinella spp. infection has never been reported among domestic pigs in Zimbabwe. Given that Trichinella spp. occurs in a sylvatic cycle in Zimbabwe and particularly in the light of the recent notification of the presence of the infection in farmed crocodiles, a survey was undertaken to evaluate the present epidemiological situation on commercial pig farms. Carcasses of 7,446 fattener pigs (average 11.7% [+/- 0.2%] of those slaughtered from each farm) were investigated by artificial digestion of pooled diaphragm muscle samples. These carcasses originated from 70 commercial piggeries and were selected by stratification on a farm basis from 63,602 pigs slaughtered during the survey period. No Trichinella spp. larvae were found in any of the 7,446 diaphragm muscle samples. The results demonstrated no evidence of Trichinella spp. infection within the pig population of the commercial piggeries in Zimbabwe.     

Routes for salmonella contamination of poultry meat: epidemiological study from hatchery to slaughterhouse

Data were collected on the prevalence of salmonella at different stages during the life cycle of 18 broiler flocks on different farms as well as during slaughter in different poultry slaughterhouses. For the isolation of salmonella, the highest sensitivity (93.9%) was obtained by enrichment in the semi-solid agar Diasalm. The 'overshoe method' utilizing several pairs of overshoes provided the highest sensitivity for determining the salmonella status of the broilers during rearing. A clear decrease of the relative importance of the first production stages was demonstrated for the salmonella contamination of the end product, whereas horizontal transmission of salmonella to broilers during rearing and to broiler carcasses in the slaughterhouse was shown to be the main determinative factor. Ten of the 18 flocks received a salmonella positive status with the highest shedding occurring during the first 2 weeks of rearing. The shedding of the animals was significantly negatively influenced by the use of subtherapeutic or therapeutic doses of antibiotics. The intake of portable material in the broiler house was identified as the most important risk factor for horizontal transmission. Significant associations were found between the contamination level of a flock and hygiene of the broiler house, feed and water in the broiler house and both animal and non-animal material sampled in the environment. No correlation was found between contamination during the rearing period and contamination found after slaughtering. The presence of faecal material in the transport crates and predominantly the identity of the slaughterhouse seemed to be the determining factors for carcass quality. Improved hygiene management during transport of broilers and in some slaughterhouses could significantly reduce the risk of salmonella contamination of poultry meat.     

玉林市2010—2011年禽、畜养殖和屠宰过程专项监测分析

目的确定从生产到销售各环节中食源性致病菌的分布,人类传染病的可能传染源,制定公共卫生措施并评价其有效性,同时为微生物风险评估提供基础数据。方法按照2010—2011年《食源性致病菌监测工作手册》内部资料进行增菌和分离鉴定。结果 94份鸡肛拭子样本未检出沙门菌;94份鸡胴体样品检出16株沙门菌;45份鸡胴体检出2株空肠弯曲菌;45份猪胴体和45份猪肛拭子样本各检出3株沙门菌;45份猪鼻拭子检出6株金黄色葡萄球菌;12份鸡场环境样本均未检出沙门菌;17份猪场环境样本检出2株金黄色葡萄球菌,未检出沙门菌。结论玉林市的禽、畜肉沙门菌的污染主要发生在屠宰过程,而生猪及其养殖环境主要是受到金黄色葡萄球菌的污染。     

Salmonellas in pigs and animal feeding stuffs in England and Wales and in Denmark

A comparison has been made between the incidence of salmonellas in pigs and feeding stuffs in England and Wales and in Denmark. In Denmark there is veterinary legislation requiring the sterilization of imported and home produced feed ingredients of animal origin. There is no such legislation in England and Wales. In Denmark 0·3% of resterilized imported meat and bone meal was contaminated with salmonellas. This compared with 23% of meat and bone meal in England and Wales and 20-27% of other ingredients of animal origin. In England and Wales salmonellas were isolated from 7% of caecal samples and 6% of lymph node samples, while in Denmark they were isolated from 3% of caecal samples and 4% of lymph node samples. In England and Wales 25 serotypes were found in both pigs and feeds and these included nearly all the most prevalent human pathogens. In Denmark four of the six serotypes in pigs had been found in resterilized feed. One notable difference between the two studies was the very wide range of serotypes found in pigs in England and Wales and the narrow range in Denmark. A second was that Salmonella typhimurium formed 15% of all Salmonella strains isolated from pigs in England and Wales, and 60% of those in Denmark.     

Prevalence and serotypes of Listeria monocytogenes contamination in Chinese beef processing plants

The aim of this work was to study the epidemiology of Listeria spp., particularly Listeria monocytogenes, and to identify the serotypes present in contaminated samples from beef processing plants in China. A total of 439 samples were obtained from bovine feces, hides, and carcasses at three commercial processing plants. A standard protocol (ISO 11290-1) was followed to detect Listeria spp. and L. monocytogenes, and multiplex polymerase chain reaction was used to identify the various L. monocytogenes serotypes. The overall prevalences of Listeria spp. and L. monocytogenes were 65.6% and 26.4%, respectively, and the contamination was highest in the hide samples. The identified L. monocytogenes serotypes were 1/2c and 1/2a. The results of the current study indicate that Listeria spp. contamination is common in Chinese beef processing plants; specific measures should be taken to prevent and/or treat L. monocytogenes contamination of feces and hides in beef slaughter plants. Furthermore, because Listeria spp. contamination was found to be prevalent, it should, therefore, be studied further. The prevention of cases of sporadic listeriosis in China should also be addressed.     

Epidemiology of Campylobacter spp. at two Dutch broiler farms.

Broiler flocks on two Dutch poultry farms were screened weekly for the presence of campylobacter in fresh caecal droppings during eight consecutive production cycles. Hatchery and fresh litter samples were taken at the start of each new cycle. Water, feed, insects, and faeces of domestic animals, present on the farms were also included in the sampling. Penner serotyping of isolates was used to identify epidemiological factors that contribute to campylobacter colonization in the broiler flocks. Generally, broiler flocks became colonized with campylobacter at about 3-4 weeks of age with isolation percentages of 100%, and stayed colonized up to slaughter. A similar pattern of serotypes was found within the various broiler houses on one farm during one production cycle. New flocks generally showed also a new pattern of serotypes. Most serotypes isolated from the laying hens, pigs, sheep and cattle were different from those isolated from the broilers at the same time. Campylobacter serotypes from darkling beetles inside the broiler houses were identical to the ones isolated from the broilers. No campylobacter was isolated from any of the hatchery, water, feed or fresh litter samples. Conclusive evidence of transmission routes was not found, but results certainly point towards horizontal transmission from the environment. Horizontal transmission from one broiler flock to the next one via a persistent contamination within the broiler house, as well as vertical transmission from breeder flocks via the hatchery to progeny, did not seem to be very likely.