The effect of time in lairage on the frequency of salmonella infection in slaughtered pigs.

Groups of pigs were brought to an abattior by truck and approximately 25 were killed on each of the next 3 days. While the pigs were in lairage they were given water but were not fed. After slaughter the caecal contents of all pigs were cultured to detect Salmonella spp. The organism was isolated from 70% of 145 pigs killed after 1 day in lairage, 49% of 143 pigs that had been in lairage for 2 days and 41% of 135 pigs that had been held for 3 days.     

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.     

Rapid infection of pigs following exposure to environments contaminated with different levels of Salmonella typhimurium

Pigs reared in an environment free of Salmonella species or on farms with low levels of infection may acquire infection during transport to the abattoir or while held in lairage. We designed a study to determine if pigs could become infected with S. Typhimurium when placed in a contaminated environment similar to that observed in commercial lairage. In addition, quantitative examination of salmonellae in all environmental and animal samples was undertaken. In order to simulate a naturally contaminated environment, animals experimentally infected with a challenge strain of S. Typhimurium (PT12) were used to seed the trial pen environment with salmonellae. In trial 1, pigs were exposed to a highly contaminated environment (5.4 log(10) CFU/100 cm(2)) for 2, 3, or 24 hours. Following these exposure periods, pigs were euthanized and samples including gastrointestinal and associated lymphoid tissue were analyzed for the challenge strain. S. Typhimuirum PT12 was detected in at least one sample type analyzed from each pig after exposure for > or =2 hours. The most frequently contaminated samples were tonsils (100% positive), followed by segments of the ileocecal junction (94.4% positive) and cecal contents (89% positive). Quantitative analysis conducted on cecal contents and ilocaecal junction segments revealed that similar numbers of organisms (1.1-2 log (10) /g) were isolated at all timepoints. In trial 2, pigs were exposed to a less contaminated environment (2.65 log (10) CFU/100 cm(2)) for periods of 1, 3, 6, or 24 hours. S. Typhimuirum PT12 was not detected in any sample from pigs euthanized after exposure of 1 hour. The challenge strain was recovered from the cecal contents of pigs after exposures of 3, 6, and 24 hours, and from the tonsil of one pig after exposure for 6 hours. These results highlight the need to reduce the environmental load of Salmonella spp. in lairage holding pens in order to reduce the numbers of infected pigs entering the slaughter process.     

Further research into the possibility of salmonella-free fattening and slaughter of pigs.

At a pig-fattening farm in the south-western Veluwe which was infected with salmonellas it was sought to achieve salmonella-free fattening in a specially adapted piggery. The test piggery was thoroughly cleaned and disinfected and measures were taken to exclude birds, insects and rodents. An attempt was also made to obtain salmonella-free piglets. Clean clothing, special footwear and disinfectants were used when entering the piggery. During the experiment an infection was detected in the test piggery caused by the same salmonella serotypes as had only been found immediately before the test at the breeding farm. Other salmonella serotypes occurring at the fattening farm did not find their way into the test piggery, and therefore it can be concluded that after the pigs had been brought in all the hygienic barriers functioned adequately. The test showed that the hygienic measures taken had a beneficial effect on growth performance, even though salmonellas were not entirely excluded. After fattening the pigs were slaughtered in two groups. The first group was slaughtered in the usual way, but with the second group extra care was taken with the individual singeing of the carcasses and the careful removal of the intestines. Tests on the carcasses showed that 46% of the pigs in the first group were contaminated with salmonellas as against only 7% in the second. From this it can be concluded that slaughter need not lead to further contamination by salmonellas present in the intestines; indeed, carefully carrying out the slaughter process can even reduce the contamination of the surface of pig carcasses by salmonellas.     

Variable abattoir conditions affect Salmonella enterica prevalence and meat quality in swine and pork

Research suggests that abattoir holding pens pose significant Salmonella enterica risk to swine immediately preharvest. The goal of this study was to evaluate those factors related to holding that increased the prevalence of S. enterica in swine at slaughter. To accomplish this goal, we focused on holding time and flooring. Our objectives were to (1) compare Salmonella enterica prevalence among pigs held for short (15-45 min) versus long (up to 4 h) periods before slaughter; and (2) determine the impact of flooring (slatted vs. concrete) as it relates to the prevalence of S. enterica. The study consisted of seven repetitions at a large volume (11,000 head/day) Midwest abattoir. Each repetition consisted of one truck load of pigs (n = 170) sorted into one of three groups: (1) animals held for a short time (15-45 min) on solid floors (short-hold); (2) animals held for 4 +/- 0.5 h on slatted floors; and (3) animals held for 4 +/- 0.5 h on solid concrete floors. At slaughter, samples were collected from 30 pigs in each group. Cecal contents (20 mL), feces (20 g), and the ileocecal lymph node were cultured for S. enterica. Additionally, the effect of holding time on meat quality parameters (loin pH at 35 min and 6 h, color, drip loss) was evaluated for the first four replicates. The proportion of S. enterica-positive samples was highest (p < 0.05) in the cecum of pigs held on solid concrete floors (72.4%), and slightly less for pigs held on slatted floors (63.3%). Animals held for less than 45 min before slaughter demonstrated the lowest proportion of S. enterica-positive samples (52.9%). The pig prevalence, as measured by any one of the three samples being positive, was significantly different (p < 0.05) between animals held on solid floors (81%) and those animals held for 45 min or less before slaughter (69%). Meat quality, as measured by multiple parameters, was adversely affected by lack of a rest period. The mean 24-h pH was significantly lower for the short-hold group compared to the other two groups. The mean Minolta L and the drip loss were significantly higher in the short-hold group. From this and other studies, it appears that elimination of the holding process is not feasible S. enterica control option, given current U.S. harvesting systems.     

Salmonella in slaughter pigs of German origin: An epidemiological study

The Salmonella prevalence in slaughter pigs of German origin was determined in seven abattoirs located in different regions of the country between February and June 1996. A total of 11,942 pigs delivered to the abattoirs in 752 batches, most of them comprised of pigs from individual finishing farms, was investigated by the bacteriological examination of faecal and gut lymph node samples, as well as of surface swabs taken from the carcasses. Salmonellae were isolated from 3.7% of the faecal samples, 3.3% of the lymph nodes and 4.7% of the surface swabs. The estimated overall prevalence of Salmonellae was 6.2% in the slaughter pigs, ranging between 1.9% and 12% in individual abattoirs. In the samples taken from carcasses, the estimated prevalence of Salmonellae reached 10.3%. 648 out of 752 batches could be included in a statistical analysis. No Salmonellae were detected in nearly 70 percent of the batches included in this analysis (n = 648). High Salmonella prevalences of more than 50 percent positive animals were detected only in 13 batches (2.0%). A statistically significant influence of the duration of the transport of slaughter pigs to the abattoirs or the waiting period in the abattoirs prior to slaughter could not be detected.     

Quantitative examination of Salmonella spp. in the lairage environment of a pig abattoir

One of the initial sources of Salmonella spp. and other bacterial pathogens at the abattoir is the carrier pig. In the absence of effective cleaning and disinfection measures, such animals may contaminate the lairage environment, which may act as a significant source of infection for incoming non-infected animals. The objectives of this study were to quantify the levels of Salmonella spp. in the lairage of a large pig abattoir and to compare the effect on environmental contamination levels with Salmonella spp. of the cleaning procedures carried out daily to those undertaken weekly. A total of 359 swabs were collected from lairage pen floors at three timepoints throughout the course of two slaughter days. All samples were analyzed quantitatively. On day 1, Monday, following weekly cleaning and disinfection, 6% of the 179 floor swabs taken were positive for Salmonella spp. On day 2, Thursday, at the end of the slaughter week, when lairage pens were subjected to high-pressure cold water washing between batches of pigs, 44% of the 180 floor swabs taken were positive for Salmonella spp. Quantitative analysis revealed that the median numbers of salmonellae detected following weekly cleaning and disinfection were approximately 1.8 organisms/100 cm(2). The numbers of salmonellae detected on day 2 were approximately 8 organisms/100 cm(2). The most prevalent serotype isolated in this study was S. Typhimurium (42%). Phage types DT12, DT104b, and U302 comprised the majority of phage types identified. These results highlight the need to develop effective intervention measures to control the spread of Salmonella spp. in the preslaughter environment.     

Dynamics of Salmonella transmission on a British pig grower-finisher farm: a stochastic model

Previous modelling studies have estimated that between 1% and 10% of human salmonella infections are attributable to pig meat consumption. In response to this food safety threat the British pig industry have initiated a salmonella monitoring programme. It is anticipated that this programme will contribute to achieving a UK Food Standards Agency target for reducing salmonella levels in pigs at slaughter by 50% within 5 years. In order to better inform the monitoring programme, we have developed a stochastic transmission model for salmonella in a specialist grower-finisher pig herd, where data from a Danish longitudinal study have been used to estimate some of the key model parameters. The model estimates that about 17% of slaughter-age pigs will be infected with salmonella, and that of these infected pigs about 4% will be excreting the organism. In addition, the model shows that the most effective control strategies will be those that reduce between-pen transmission.     

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。     

Prevalence of Salmonella in finishing swine raised in different production systems in North Carolina,USA.

We compared the prevalence of salmonella in faecal samples from finishing pigs and in feed samples from swine herds in North Carolina, USA. Farms were either finishing sites using all-in/all-out management of buildings in multiple-site systems (14 farms) or farrow-to-finish systems using continuous flow management of finishing barns (15 farms). The two groups of herds differed with respect to several management variables. Salmonella were isolated from 565 of 2288 (24.6%) faecal samples and from at least 1 faecal sample on 24 of 29 (83%) farms. Predominant serotypes were S. derby, S. typhimurium (including copenhagen), S. heidelberg, S. worthington and S. mbandaka. Fewer farrow-to-finish farms were detected as positive compared with all-in/all-out farms. Prevalence was lower for pigs raised on slotted floors compared with all other floor types, and was highest for pigs raised on dirt lots. Modern methods of raising pigs in multiple-site production systems, using all-in/all-out management of finishing pigs, appear to have no benefit in reducing the prevalence of salmonella compared with conventional farrow-to-finish systems.     

Influence of multiple plating from fluid media on salmonella isolation from animal feeding stuffs.

The influence of multiple plating of fluid cultures on salmonella isolation from animal feeding stuffs was examined. Four plating were made from broth culture after 24 h at 37 degrees C and four platings from selenite enrichment from 24 h at 43 degrees C. Selenite enrichment followed broth culture which was used as a pre-enrichment stage. Brilliant green MacConkey agar plates were employed for broth subculture and brilliant green MacConkey and desoxycholate citrate agars for selenite subculture. The eight brilliant green plates subcultured from broth and selenite were examined for salmonellas after incubation for 24 h at 37 degrees C. The four desoxycholate citrate agars after 24 h at 37 degrees C were used for motility enrichment. The food sample size was a single 100 g instead of 4 x 25 g cultured in an earlier study. This pooling of samples aimed at technical economy. Quadruple plating played an important part in salmonella isolation from 100 g specimens. The combination of multiple plating with motility enrichment was the most successful technique used.     

The virulence of trimethoprim-resistant thymine-requiring strains of Salmonella.

A thymine-requiring (thy-), trimethoprim-resistant (tmpr) mutant isolated from the faeces of chickens experimentally infected with salmonella typhimurium and treated with mixture of trimethoprim and sulphadiazine was less virulent for chickens than the parent strain and a thy+tmps revertant prepared in vitro from the mutant. The difference in chicken-virulence was more noticeable when the strains were administered orally than when they were administered subcutaneously. All tmpr mutants prepared in vitro from four other salmonella strains were also thy-; those tested were less virulent for chickens and mice than their parent strains. After oral infection, thy- salmonella organisms were found much less commonly in the alimentary tract of chickens then were thy+ organisms. This was especially so in the caeca, the principal site of colonization of both the thy+ and thy- organisms. Relatiely high concentrations of thymine or related compounds were found in the contents of all regions of the alimentary tract of chickens except the caeca; the caeca usually contained low or undetectable concentrations. The thy- salmonella strains would not grow on one brand of briliant green agar because of its deficiency in thymine; their colonial and appearance on other kinds of media used for isolating salmonellae from clinical material was often 'un-salmonella-like'.     

A survey of Campylobacter in animals

A survey of Campylobacter species in the faeces or rectal contents of domestic animals was carried out using direct and enrichment culture methods. Campylobacters were isolated from 259 (31%) of 846 faecal specimens. The highest isolation rate was found in pigs (66%); lower rates were found in cattle (24%) and sheep (22%). In pigs all the isolates were C. coli, in sheep and cattle about 75% were C. jejuni. Only five isolations of C. fetus subsp. fetus were made, all from cattle. More pigs with diarrhoea had C. coli in their faeces than healthy pigs (77% vs 47%), but such a clear difference in isolation rate between sick and healthy animals was not seen in cattle or sheep. The enrichment method increased the total isolation rate of C. jejuni and C. coli by 33%, but for cattle specimens it increased it by 69% (from 6.5% to 21%). However, the enrichment method failed to detect 16% of positive specimens (mainly C. coli), so direct and enrichment methods should be used for the culture of campylobacters from animal faeces. The results show that cattle, sheep and pigs constitute a large potential source of campylobacter infection for man.     

A survey of Campylobacter in animals.

A survey of Campylobacter species in the faeces or rectal contents of domestic animals was carried out using direct and enrichment culture methods. Campylobacters were isolated from 259 (31%) of 846 faecal specimens. The highest isolation rate was found in pigs (66%); lower rates were found in cattle (24%) and sheep (22%). In pigs all the isolates were C. coli, in sheep and cattle about 75% were C. jejuni. Only five isolations of C. fetus subsp. fetus were made, all from cattle. More pigs with diarrhoea had C. coli in their faeces than healthy pigs (77% vs 47%), but such a clear difference in isolation rate between sick and healthy animals was not seen in cattle or sheep. The enrichment method increased the total isolation rate of C. jejuni and C. coli by 33%, but for cattle specimens it increased it by 69% (from 6.5% to 21%). However, the enrichment method failed to detect 16% of positive specimens (mainly C. coli), so direct and enrichment methods should be used for the culture of campylobacters from animal faeces. The results show that cattle, sheep and pigs constitute a large potential source of campylobacter infection for man.     

The carriage of Corynebacterium suis in male pigs.

This investigation was designed to determine the prevalence of Corynebacterium suis in the preputial diverticulum of pigs of various age groups, located in different parts of the U.K., and to demonstrate whether the organism is transmissible between male pigs. C. suis was isolated from almost 90% of 224 adult males, distributed among 25 pig units in widely separated regions of the country and in 96% of 66 pigs aged 5-6 months originating from six different herds in East Anglia. The rate of isolation of C. suis from younger pigs depended, at least in part, on the system of husbandry practised. Thus, in one herd, A, in which young pigs were maintained in comparative isolation, none of 26 pigs aged 5-8 weeks harboured C. suis; however, in the same herd, the organism was isolated from 77% of 64 pigs aged 9-15 weeks which were in close contact with male pigs aged up to 6 months. In another herd, B, in which individual litters were housed in the same pen from birth to 5 months of age, C. suis was isolated once from only one of 36 pigs in the age range 5-17 weeks, sampled on two occasions, with an interval of 5 weeks between each sampling.(ABSTRACT TRUNCATED AT 250 WORDS)     

The carriage of Corynebacterium suis in male pigs

This investigation was designed to determine the prevalence of Corynebacterium suis in the preputial diverticulum of pigs of various age groups, located in different parts of the U.K., and to demonstrate whether the organism is transmissible between male pigs. C. suis was isolated from almost 90% of 224 adult males, distributed among 25 pig units in widely separated regions of the country and in 96% of 66 pigs aged 5-6 months originating from six different herds in East Anglia. The rate of isolation of C. suis from younger pigs depended, at least in part, on the system of husbandry practised. Thus, in one herd, A, in which young pigs were maintained in comparative isolation, none of 26 pigs aged 5-8 weeks harboured C. suis; however, in the same herd, the organism was isolated from 77% of 64 pigs aged 9-15 weeks which were in close contact with male pigs aged up to 6 months. In another herd, B, in which individual litters were housed in the same pen from birth to 5 months of age, C. suis was isolated once from only one of 36 pigs in the age range 5-17 weeks, sampled on two occasions, with an interval of 5 weeks between each sampling.(ABSTRACT TRUNCATED AT 250 WORDS)     

Beef carcass contamination by Shiga toxin-producing Escherichia coli strains in an abattoir in Brazil: characterization and resistance to antimicrobial drugs

A survey was performed to estimate the frequency of Escherichia coli and Shiga toxin-producing E. coli (STEC) in carcasses obtained from an abattoir in Brazil between February 2006 and June 2007. A total of 216 beef carcasses were sampled at three stages of the slaughter process--preevisceration, postevisceration, and postprocessing--during the rain and dry seasons, respectively. Of the carcasses sampled, 58% were preevisceration E. coli positive, 38% were postevisceration positive, and 32% postprocessing positive. At the postprocessing stage, the isolation of E. coli was twice as high in the rain season. E. coli was isolated from 85 carcasses of which only 3 (1.4%) were positive for stx-encoding genes. No E. coli O157 serogroup isolates were detected. No antimicrobial resistance was found in nine of the isolates (10% of the total). The most frequent resistances were seen against cephalothin (78%), streptomycin (38%), nalidixic acid (36%), and tetracycline (30%). Multidrug resistance (MDR) to three or more antimicrobial agents was determined in 28 (33%) E. coli isolates. The presence of STEC and MDR strains among the isolates in the beef carcasses emphasizes the importance of proper handling to prevent carcass contamination.     

Direct feeding of microencapsulated bacteriophages to reduce Salmonella colonization in pigs

Salmonella shedding often increases in pigs after transportation and/or lairage. We previously showed that administering anti-Salmonella bacteriophages to pigs by gavage significantly reduced Salmonella colonization when the pigs were exposed to a Salmonella-contaminated holding pen. Here we tested whether a microencapsulated phage cocktail would remain effective if the treatment was administered to pigs in the feed. Pigs (n=21) were randomly placed into three groups: feed, gavage, and control. The feed group was direct-fed a microencapsulated phage cocktail daily for 5 days. On the fifth day, the gavage group received the same phage cocktail by gavage, whereas control pigs received a mock treatment containing no phage. All pigs were then orally challenged with Salmonella enterica serovar Typhimurium. Fecal swab samples were collected every 2?h. At 6?h postchallenge, all pigs were euthanized, and ileal and cecal contents and mesenteric lymph nodes were collected and analyzed for the challenge organism. Pigs in the feed group were less likely to shed Salmonella Typhimurium at 2?h (38.1%) and 4?h (42.9%) postchallenge than pigs in both the gavage (2?h: 71.4%; 4?h: 81.1%) and control (2?h: 71.4%; 4?h: 85.7%) groups (p<0.05). Likewise, concentrations of Salmonella Typhimurium in ileal (2.0 log(10) colony forming units [CFU]/mL [contents]) and cecal (2.7 log(10) CFU/mL) contents from feed pigs were lower than ileal (3.0 log(10) CFU/mL) and cecal (3.7 log(10) CFU/mL) contents from control pigs. High concentrations of anti-Salmonella phages were detected in ileal and cecal contents from both feed and gavage pigs (feed ileal: 1.4×10(6); feed cecal 8.5×10(6); gavage ileal 2.0×10(4); gavage cecal: 2.2×10(3)). It is concluded that direct feeding of microencapsulated phages is a practical and effective means of reducing Salmonella colonization and shedding in pigs.     

The epidemiological relationship between Salmonella isolated from poultry meat and sewage effluents at a long-stay hospital

Between February 1988 and March 1989 chicken carcases delivered to the kitchen of a long stay psycho-geriatric hospital were screened every week for salmonella contamination. While 214 of 477 (45%) individual carcases carried one or more salmonella types, every single consignment examined contained affected carcases. Simultaneously, sewers draining the residential accommodation and excluding kitchen effluent, were also monitored. Thirty out of 79 (38%) of Moore's swabs were positive for salmonella. There was a statistically significant association between the salmonella types isolated from chicken and those isolated from sewers the following week. Following a change in kitchen policy to order only cooked chicken there was a significant reduction in the isolation of salmonella from the sewers.