The effect of cobalt topdressing in preventing cobalt deficiency disease of lambs in southland

Environmental samples and samples of partially processed fish from a cold-smoked salmon processing and packing plant, and product samples purchased from retail outlets, were examined for the presence of Listeria monocytogenes and other Listeria spp., motile aeromonads and Yersinia enterocolitica. Listeria spp. were not isolated from rati fish but were a contaminant of processed and partially processed fish. Listeria spp. were also detected in 18.8% of surfaces in contact with fish. Unlike Listeria spp., motile aeromonads were isolated from the raw fish but not from the finished product. They were more frequently isolated from environmental sources than Listeria spp. Yersinia enterocolitica was not isolated from any of the samples tested. Little evidence was found to show a coincidence of motile aeromonads and Listeria spp., since only one subset of samples showed such a link. It is concluded that contamination by Listeria spp. was from environmental sources at the processing plant at, or beyond, the slicing stage. Reducing the number of wet areas and special cleaning and sanitation considerations for a contaminated site (the freezer seal) are suggested as ways of reducing contamination of the product.     

A survey for Listeria species, motile aeromonads and Yersinia enterocolitica on bovine and ovine carcasses

One hundred ovine and 100 bovine carcasses in two abattoirs were sampled just after dressing for the presence of Yersinia enterocolitica, Listeria monocytogenes and motile aeromonads. Yersinia enterocolitica was not isolated and only two samples were positive for Listeria spp. In both cases, the Listeria species were not normally pathogenic to man. In contrast, motile aeromonads were isolated from 81% of ovine and 35% of bovine carcasses.     

Prevalence of Campylobacter spp. and Yersinia spp. in the pig production

The aim of this study was to determine the prevalence of Campylobacter spp. and Yersinia spp. in a total of 1,040 faecal samples taken from animals at different ages from four farrowing and twelve fattening herds. In the farrowing unit, faeces were collected from 68 sows (faecal samples) and 256 suckling piglets (rectal swab samples). Further samples were collected from 362 growing and 354 finishing pigs (rectal swab samples). Additionally, 56 feed and environmental samples were collected. During the slaughtering process, 122 pigs and their carcasses respectively, were sampled three times. Finally, 86 meat and minced meat samples were taken from 34 retail stores. Campylobacter spp. were isolated in sows (33.8 %), piglets (80.9 %), growing (89.2 %) and finishing (64.7 %) pigs. Yersinia spp. were detected in growing (15.2 %) and finishing (13.3 %) pigs only. After twelve hours of chilling neither Campylobacter spp. nor Yersinia spp. were detected. In raw meat samples, Campylobacter spp. were isolated from one liver sample and Yersinia enterocolitica from two meat samples. Common slaughter techniques and hygiene procedures may be effective tools to reduce the risk of contamination and recontamination of meat products since Campylobacter spp. and Yersinia spp. were found only sporadically in raw meat samples.     

The bacteriological and serological prevalence of Campylobacter spp. and Yersinia enterocolitica in fattening pig herds in Lower Saxony

This article presents the results of a study on the occurrence of two bacteria that cause zoonoses, Campylobacter spp. and Yersinia enterocolitica. The study was carried out in 30 fattening herds in Lower Saxony, Germany, in 2004 and compares the results of bacteriological and serological methods of detection. Bacteriological findings of Campylobacter spp. in the faeces indicated that 69.7% of the fattening pigs were positive, but 81.2% tested positive serologically. All herds tested here were both bacteriologically and serologically positive for Campylobacter spp. Furthermore, only 8.4% tested positive for Yersinia enterocolitica in the faecal samples, but 66.8% of the animals were serologically positive for that bacterium. While bacteriological examination did not detect Yersinia enterocolitica in 56.7% of the herds tested, serological testing showed that only 16.7% of the units were without reacting animals. The great difference between the results of bacteriological and serological testing, especially in the case of Yersinia enterocolitica, can be explained by the intermittent intestinal excretion and predominance of this bacterium in the animals' tonsils. Low faecal excretion is also the reason for the low detection rate of 3.4% of Yersinia enterocolitica in the environmental samples, while that of Campylobacter spp. was 33.3%. These results indicate that the environment plays only a secondary role in the distribution of Yersinia enterocolitica in pig herds.     

Experimental mixed infection of rabbits with Yersinia enterocolitica and Listeria monocytogenes

Experimental mixed infection was reproduced in rabbits after per os infection with Yersinia enterocolitica serotype 0:3 cells. Four days later some of animals were re-infected orally with Listeria monocytogenes serotype 4b cells. A third group of healthy rabbits was also infected per os with Listeria monocytogenes. The infectious process was followed dynamically from days 1-28. The experimental animals were examined for clinical, paraclinical and morphological findings. Augmentation of body temperature and alveolar macrophage number, a decreased number of peritoneal macrophages, leucopenia as well as purulent meningoencephalitis, catarrhal pneumonia, lienitis, lymphadenitis and enteritis were detected after experimental mixed infection. Both types of macrophages demonstrated a weak bactericidal activity against Yersinia enterocolitica and a highly expressed killing effect against Listeria monocytogenes. Yersinia and Listeria cells were isolated from the viscera and brain. Both species of bacteria were established intracellularly in the macrophages by electron-microscopic examination. The data received showed that mixed Yersinia enterocolitica 0:3 and Listeria monocytogenes 4b infection of rabbits runs with transitory hyperthermia as a generalized infection and is similar to the Listeria mono-infection. The immunosuppressive effect induced by oral Yersinia enterocolitica infection of rabbits promotes the expression of listerious agents.     

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.     

Epidemiological study of Yersinia enterocolitica in swine herds in Québec

The objectives of this study were the identification of the different contamination sources of Yersinia enterocolitica, as well as the determination of the prevalence and the distribution of the different genotypes in swine herds. The owners of 20 farms, located in the Richelieu-Yamaska region, agreed to participate in the study. Each farm was visited a minimum of 5 times between May and October 1997, and, at each visit, 20 environmental and 10 fecal samples were collected. Yersinia enterocolitica isolates were identified, serotyped, and submitted to a genetic characterization by pulsed-field gel electrophoresis. The correlation coefficient (0.61) between prevalence in environment and in feces was significant (P = 0.004). Among the 153 positive samples, 93.5% belonged to serotype 0:3. The comparison of PFGE profiles revealed that all environmental Y. enterocolitica isolates had a profile identical to that of isolates recovered in feces from the corresponding farms. Also, when the genetic profiles of isolates recovered from feces collected at the first visit were compared with the profiles of isolates obtained from the subsequent visits, the same profile was observed on every farm. We concluded that environment does not represent the main source of contamination of swine by Y. enterocolitica and that, in most instances, the same strain persists in a barn from one production lot to another.     

Survey on the Listeria contamination of ready-to-eat food products and household environments in Vienna, Austria

Qualitative and quantitative contamination of ready-to-eat food-stuffs with the pathogen Listeria monocytogenes was studied in 1586 samples collected from 103 supermarkets (n = 946) and 61 households (n = 640) in Vienna, Austria. Seventeen groups of ready-to-eat foods were classified into three risk categories for contamination (CP1-CP3). Three to four samples were randomly collected at the retail level from each CP. Regarding the households, the sampling procedure was started with food items of CP1, and if not available, was continued with sampling of food items of CP2 and finally of CP3. Additionally, 184 environmental samples (swabs from the kitchen area, dust samples from the vacuum cleaner) and faecal samples (household members and pet animals) were included. One-hundred and twenty-four (13.1%) and 45 (4.8%) samples out of 946 food samples collected from food retailers tested positive for Listeria spp. and L. monocytogenes, respectively, with five smoked fish samples exceeding the tolerated limit of 100 CFU/g food. Food-stuffs associated with the highest risk of contamination were twice as frequently contaminated with L. monocytogenes as food-stuffs associated with a medium risk of contamination. Products showing the highest contamination rate were fish and seafood (19.4%), followed by raw meat sausages (6.3%), soft cheese (5.5%) and cooked meat products/patés (4.5%). The overall contamination rate of foods collected at the household level was more than two times lower. Only 5.6% and 1.7% of 640 food-stuffs analysed tested positive for Listeria spp. and L. monocytogenes, respectively. However, CP1 foods were rarely collected. Pulsed-field gel electrophoresis (PFGE) typing of the collected L. monocytogenes isolates revealed a high degree of diversity between the isolates, with some exceptions. PFGE typing of isolates harvested from green-veined cheese revealed a match among strains, although the manufacturer seemed to be distinguishable. Typing of household strains revealed an epidemiological link within one family. In this case, food-stuffs and the kitchen environment were contaminated by an indistinguishable isolate. In addition, the same isolate was collected from a pooled faecal sample of the household members suggesting that consumption of even low contaminated food items (<100 CFU/g) results in Listeria shedding after the passage through the gut.     

Food safety in raw milk production: risk factors associated to bacterial DNA contamination

While human illness from milkborne pathogens may be linked to contamination of the product after pasteurization or improper pasteurization, such diseases are usually associated with consumption of raw milk or its by-products. Molecular biology tools were applied to investigate contamination by Listeria monocytogenes, Salmonella spp., some pathogenic strains of Escherichia coli, and Campylobacter jejuni in 548 raw milk samples from 125 dairy farms established in two regions from southern Brazil. Moreover, 15 variables were evaluated for their association with raw milk contamination levels, and the risk factors were determined by multiple regression analysis. Salmonella spp. were more frequently detected, followed by pathogenic E. coli. There was difference in contamination index between the regions, in which risk factors such as temporary cattle confinement, low milk production, low milking machine cleaning frequency, and milk storage area without tile walls were identified. The risk factors were specific to each region studied. Nevertheless, the data can be used to improve milk quality of dairy farms/herds with similar management practices.     

The occurrence of Listeria in the production of processed meat, salami and mettwurst

In six Swiss meat-processing plants 206 samples of cured and air-dried beef (Bündnerfleisch), salami and Mettwurst were analyzed for the presence of Listeria spp. Samples were taken during the fabrication, fermentation and drying of the products. Out of 44.7% of all samples Listeria spp. could be detected. 6.8% turned out to be L. monocytogenes, 37.4% L. innocua and 0.5% L. seeligeri. Listeria spp. were found in all production stages of the tested foods. The concentration of L. monocytogenes was always less than or equal to 20 MPN/g. 86% of the isolated strains formed part of the serogroup 1/2 and 14% of the serogroup 4. Listeria spp. could only be found on the surface of Bündnerfleisch. Both, L. monocytogenes and L. innocua were able to survive the maturation process of salami, even when the initial concentration was very low. The ripening was more often survived by L. innocua than by L. monocytogenes. It appeared that Mettwurst had the highest contamination rate of Listeria spp. (94.4%), followed by salami (46.7%) and Bündnerfleisch (23.1%). The corresponding proportions for L. monocytogenes were 8.0% (salami), 5.8% (Bündnerfleisch) and 0% (Mettwurst). Listeria spp. positive samples were found in every examined plant, L. monocytogenes in five of therm. The Listeria spp. contamination rates moved from 10.0% to 86.2%, those of L. monocytogenes from 0% to 12.1%.     

Isolation of Listeria monocytogenes from the skin of slaughtered beef cattle

We attempted to isolate Listeria monocytogenes from skin, contents of large intestines and carcasses of cattle introduced to a slaughterhouse in order to identify source of contamination for this pathogen. Sixty skin samples, 60 samples of the contents of large intestines and 30 carcass samples were colleted in June, August and November 2003 for use in this study. Listeria spp. and L. monocytogenes were isolated from 30 (50%) and 3 (5%) of the cattle skin samples, respectively. However, no Listeria spp., including L. monocytogenes, were isolated from intestinal contents or carcasses. Seven isolates were obtained, of which five and two strains were serotypes 1/2a and 1/2b, respectively. Genetic analysis suggested that there was persistent inhabitation of the pathogen around the area investigated in this study.     

Immuno-magnetic separation and agar layer methods for the isolation of freeze-injured Yersinia enterocolitica O:8 from water

To develop an effective method to isolate an injured pathogenic Yersinia enterocolitica O:8 organism from environmental samples, we compared the isolation of freeze-injured and non-injured Y. enterocolitica O:8 and found that the isolation was more successful when immuno-magnetic separation (IMS) with anti-Y. enterocolitica O:8 antibody was used. Plating onto cefsulodin-irgasan-novobiocin (CIN) agar and Virulent Yersinia enterocolitica (VYE) agar by means of the agar layer method was found to be effective in isolating the injured cells. The alkali treatment which is generally used for selective detection of Yersinia organism failed to isolate freeze-injured pathogenic Y. enterocolitica O:8 cells. Recovery methods without using the alkali treatment were superior for detecting freeze-injured Y. enterocolitica O:8. Our results demonstrate that the IMS and the agar layer methods should be used to isolate injured pathogenic Yersinia organisms from environmental samples such as water.     

Evaluation of bacterial and protozoal contamination of commercially available raw meat diets for dogs

OBJECTIVE: To evaluate bacterial and protozoal contamination of commercially available raw meat diets for dogs. DESIGN: Prospective longitudinal study. SAMPLE POPULATION: 240 samples from 20 raw meat diets for dogs (containing beef, lamb, chicken, or turkey), 24 samples from 2 dry dog foods, and 24 samples from 2 canned dog foods. PROCEDURE: Each product was purchased commercially on 4 dates approximately 2 months apart. Three samples from each product at each sampling period were evaluated via bacterial culture for non-type-specific Escherichia coli (NTSEC), Salmonella enterica, and Campylobacter spp. Antimicrobial susceptibility testing was performed on selected isolates. Polymerase chain reaction assays were used to detect DNA from Cryptosporidium spp, Neospora spp, and Toxoplasma spp in samples obtained in the third and fourth sampling periods. RESULTS: One hundred fifty-three of 288 (53%) samples were contaminated with NTSEC. Both raw and prepared foods contained NTSEC during at least 1 culture period. Salmonella enterica was recovered from 17 (5.9%) samples, all of which were raw meat products. Campylobacter spp was not isolated from any samples. In 91 of 288 (31.6%) samples, there was no gram-negative bacterial growth before enrichment and in 48 of 288 (16.7%) samples, there was no aerobic bacterial growth before enrichment. Susceptibility phenotypes were variable. Cryptosporidium spp DNA was detected in 3 samples. CONCLUSIONS AND CLINICAL RELEVANCE: Bacterial contamination is common in commercially available raw meat diets, suggesting that there is a risk of foodborne illness in dogs fed these diets as well possible risk for humans associated with the dogs or their environments.     

Contamination of raw milk by Listeria monocytogenes on dairy farms

Possible sources of exogenous contamination of raw milk by Listeria monocytogenes were examined on four dairy farms of different size and type of animal housing during morning milking. Feeds, including hay and concentrates, were found to be major sources of both pathogenic and nonpathogenic species of Listeria on the barns. L. innocua was the only species isolated from the grass silage, which was of good quality on all the farms. The numbers of Listeria were below 10(2)/g in all feed samples. Fecal shedding of listeriae was detected in 11.9% of the cows and the prevalences of L. monocytogenes among farms ranged from no detections to 8.7%. The number of Listeria isolations from constructions inside the barns and from the milking environment varied between the farms. Listeriae were detected almost everywhere on one of the farms whereas on another farm the only isolations were from feed passages and floors. 13.6% of the swab samples taken from the teats before washing and drying were Listeria positive, whereas no isolations were made after cleaning the udder. Good milking and barn hygiene is considered important for diminishing the risks of exogenous contamination of raw milk by listeriae.     

Epidemiological studies on the occurrence of Listeria monocytogenes in the feces of dairy cattle

Seasonal variation in the fecal shedding of Listeria spp. in dairy cattle was examined by collecting a total of 3,878 fecal samples during a period of two years. The prevalences of Listeria spp. and L. monocytogenes were higher during the indoor season (12.7% and 9.2%, respectively) than in samples collected from the animals on pasture (5.3% and 3.1%, respectively). The highest frequencies of Listeria spp. (19.4%) and L. monocytogenes (16.1%) were detected in December. Listeriae were isolated from at least one of the dairy cows from 45.8% of the 249 herds examined. 2.9% of the 314 milk samples collected from the farm bulk tanks on 80 dairy farms on four different occasions yielded L. monocytogenes. The seasonal occurrence of these bacteria in milk reflected the frequencies of Listeria in the fecal material but not those in the main roughage used; grass silage and pasture grass. Fecal material is considered to be a potential source of contamination of raw milk by L. monocytogenes. Investigation of the numbers of viable Listeria organisms in different animal fodders is considered essential in further epidemiological studies of these bacteria.     

Occurrence of Listeria spp. in captive antelope herds and their environment.

Two juvenile scimitar-horned oryx (Oryx dammah) at the Wild Animal Park Planckendael died from acute septicemia caused by Listeria monocytogenes serovar 4b. Subsequently, Listeria spp. were isolated from the feces, food, and environment of seven antelope species and examined using a two-stage enrichment procedure in Fraser Broth, followed by isolation on PALCAM agar. A total of 40/170 samples (23.5%) was positive for Listeria spp. No organisms were cultured in 83/170 samples (48.8%), and 47 samples (27.6%) were overgrown with Bacillus spp. Nonpathogenic Listeria spp. were isolated from 16/70 fecal samples, 22/40 soil samples, and 2/60 feed samples. Listeria monocytogenes serovar 1/2b was isolated from two soil samples collected in the enclosure of the scimitar-horned oryx.     

Non-specific seroreactions against Brucella abortus in ruminants in New Zealand and the presence of Yersinia enterocolitica 0:9

The level of non-specific reactions found in the brucellosis serology of ruminants in New Zealand was very low until July 1992. This changed when, in an export consignment of 1071 deer, 35% reacted in the Brucella abortus tube agglutination test with titres varying from 50 to 200 IU. The reactors were also positive in the Rose-Bengal agglutination test and most of them reacted in the complement fixation test with titres varying from 10 to 80 IU. Yersinia enterocolitica 0:9 was later isolated from one deer of this consignment. It was the first isolate of this serotype recovered in New Zealand from an animal. Shortly after, false reactors occurred more frequently than before in sera from Brucella abortus accredited free cattle herds. As the involvement of Yersinia enterocolitica 0:9 was suspected in these cases, faecal samples from reactors and in-contact animals were cultured for this organism. Yersinia enterocolitica 0:9 was isolated from nine of 19 herds showing one or more false Brucella abortus seroreactions. Prior to 1990, Yersinia enterocolitica serotype 0:9 had not been isolated in New Zealand, despite the recovery of a number of other bio- or serotypes of the organism from humans and animals. From 1990 onward, serotype 0:9 began to be isolated from human faecal samples with increasing frequency. Since the first isolations from deer and cattle in 1992, it has now also been recovered from a cat and an alpaca and from cattle without any association with false positive Brucella abortus reactions. All serotype 0:9 isolates were of biotype 2.     

Biotypes and sensitivity screening Yersinia enterocolitica as an infective agent in man and swine in Nigeria.

Diarrhoeic faecal samples from 210 humans and 192 swine were screened for Yersinia enterocolitica in 1990. Ten and 8 Y. enterocolitica strains were isolated from pig and man, respectively. The isolates were found to belong to Wauter's biotypes 1, 2, 3 and 4. Biotype 2 was isolated mainly from human stool samples. Biotype 3 was found only in swine while biotypes 1 and 4 were isolated from both man and swine. All the 18 strains showed varying degrees of sensitivity to antibiotics used in this investigation. The organisms were consistent in their resistance to ampicillin and penicillin.     

哈尔滨市鲜肉中单核细胞增生性李斯特菌的分离鉴定及耐药性分析

为了解哈尔滨市单核细胞增生性李斯特茵(Lm)的污染状况及耐药状况.在哈尔滨市市场随机采集158份鲜肉样品,采用显色培养基分离,API试剂条和PCR鉴定等方法对样品中的Lm进行分离鉴定,并通过Kirby-Barer法测定分离菌株对24种抗生素的耐药性.结果从鲜肉中共分离到Lm 23株,检出率为14.56%,其中鲜猪肉检出率最高,达20.00%(14/70);23株分离菌株中耐药菌株为22株,耐药率高达95.65%.这表明哈尔滨市鲜肉中存在一定程度的Lm污染,并且分离菌株存在较严重的耐药现象.应加强控制动物饲料亚治疗抗生素的使用并严格遵守休药期,防止耐药菌株产生进而控制食源性疾病的发生.     

The role of wild birds and the environment in the epidemiology of Yersiniae in New Zealand

A survey was carried out to determine the prevalence of Yersiniae in wild passerines in the lower half of the North island of New Zealand over a period of 12 months. Samples of soil, water and foliage were also collected. Out of a total of 1370 avian samples, only two strains of Y. pseudotuberculosis were isolated and a total of 98 strains of environmental yersiniae were identified, including Y. enterocolitica biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia. No strains of Y. pseudotuberculosis were isolated from 1032 non-avian samples collected, which included 100 samples taken from wild mammals. From the non-avian samples, 51 strains of environmental Yersiniae were identified, of which the relative prevalence of Yersinia enterocolitica, biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia was similar to that in the rural passerines. The prevalence of Yersiniae in soil samples was greater in rural areas than in urban areas of the survey region. In both rural and urban passerine populations, the prevalence of Yersiniae was greater in the winter and early summer than at other times of the year.