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1.
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.  相似文献   

2.
The aim of the present study was to survey the prevalences of the enteric pathogens Brachyspira hyodysenteriae, Brachyspira pilosicoli and Lawsonia intracellularis in Swedish growing pigs and in the Swedish wild boar population and to relate these findings to clinical signs. The study included 105 randomly selected herds, constituting approximately one third of Swedish herds with a herd size of >100 sows. The herds were located all over the country. In these herds, growth promoters were not used and pigs sampled were not subjected to any medication. From each herd, samples were taken from 10 growing pigs aged 8-12 weeks, corresponding to approximately 2.5% of all growing pigs present in the herd at the sampling occasion. If possible, the samples were taken from pigs with diarrhoea. Forty-eight faecal samples and 71 rectal swabs were also taken from free-living wild boars (31 piglets, 19 growers and 21 adult animals) at shooting. The samples were analysed by culture and biochemical tests for the presence of Brachyspira spp. and by nested PCR for the presence of L. intracellularis. Brachyspira hyodysenteriae was not demonstrated in any sample. Brachyspira intermedia was detected in 22 samples originating from 15 herds, Brachyspira innocens/Brachyspira murdochii was detected in 370 samples from 82 herds and B. pilosicoli was detected in 134 samples originating from 34 herds. In 21 herds and in 534 samples, no Brachyspira spp. were detected. Lawsonia intracellularis was demonstrated in 285 samples from 50 herds. Further, 418 samples from conventional herds were negative with respect to L. intracellularis and in 345 samples the PCR had been inhibited. All samples from the wild boars were negative for Brachyspira spp., 12 of 48 samples were negative for L. intracellularis, and in 36 wild boar samples, the PCR was inhibited.  相似文献   

3.
The aim of this study was to investigate faecal shedding and transmission of Campylobacter spp. in cohorts of cattle within a feedlot, to assess subsequent contamination of carcasses with this pathogen and to identify risk factors associated with faecal shedding of Campylobacter spp. A cohort of 133 heifers housed in four adjacent pens was examined over a five and a half month period, from entering the feedlot to slaughter. A parallel investigation of individual rectal faecal samples and pen environmental samples were taken at monthly intervals from November to February. The entire outer and inner surfaces of a carcass side of each animal were swabbed immediately following slaughter. Campylobacter spp. were isolated from 322 (54%) of the 600 rectal faecal samples. Campylobacter jejuni and C. coli accounted for 69 and 29.7% of the isolate recovered, respectively. A total of 159 environmental samples were examined, of these Campylobacter spp. was isolated from 46 samples (29%). Campylobacter jejuni and C. coli accounted for 35 and 59% of these isolates, respectively. Campylobacter spp. was not isolated from any of the dressed carcasses. Logistic regression indicated prevalence of Campylobacter spp. faecal shedding within pens was positively correlated to the pen, the month of sampling and the Campylobacter spp. contamination status of the pen dividing bars and the water trough surface. Campylobacter spp. should be considered as a pathogen shed in the faeces of a substantial proportion of feedlot cattle. However, with good hygienic practice during harvest, a very low level of this pathogen can be achieved on dressed carcasses.  相似文献   

4.
In this work, faecal samples were collected from 15 pig farms to determine the Campylobacter prevalences at different times during the rearing period and to visualize the exchange of strains among the pig population by genotyping specific isolates. All isolated strains were identified as C. coli. Whereas no Campylobacter were detectable in the faeces of piglets at the day of birth, the Campylobacter incidence rose within days to 32.8%. After transfer to the nursery unit the prevalence increased to 56.6%. Approximately two-thirds of the pigs remained C. coli shedders in the fattening unit. In contrast to most farms, one farm expressed a very low Campylobacter incidence during the whole rearing period. Amplified fragment length polymorphism (AFLP) analysis was performed on all C. coli isolates of one farm. Clonal strains were identified from the brood sows and their offsprings or neighbouring piglets. After moving to the nursery unit, new genotypes appeared in that pig group but the original C. coli strains largely remained within that group. C. coli genotypes, identified during the fattening period, replaced the previously isolated genotypes. Transportation to the abattoir had no significant influence on the shedding rate of C. coli. The detection rate before transportation was 79.1% and decreased slightly to 78.2% (n=330). Additionally, eleven of 1474 environmental samples from different sources of the pig farms were positive for C. coli. This study demonstrates the importance of pigs as a reservoir for C. coli. Maternal C. coli strains are the primary source of infection but non-related genotypes from different sources appear during the rearing period and these latter strains constitute largely the final C. coli flora.  相似文献   

5.
The present study focused on Mycoplasma hyopneumoniae (M. hyopneumoniae) detection by nPCR in nasal swabs of 507 suckling pigs. These animals came from 69 sows (from 1 to 8 parity number) of a farrow-to-finish herd with Enzootic Pneumonia (EP) problems at finishing stages. At 1 and 3 weeks of age (still in the farrowing units), nasal swabs and blood samples were taken from all piglets. Moreover, from these 507 animals, 37 randomly selected pigs were necropsied at 3 weeks of age. From those necropsied pigs, M. hyopneumoniae presence was tested in bronchial and tonsillar swabs. At 1 week post-farrowing, blood samples from sows were collected and used to detect M. hyopneumoniae antibodies. From the 69 analysed sows, 19 (27.5%) were seropositive. Global percentage of pigs with M. hyopneumoniae detection in nasal swabs at 1 and 3 weeks of age was 1.5% (8 out of 507) and 3.8% (19 out of 507), respectively. From these nPCR positive pigs, 89% (24 out of 27) were seronegative and 11% were seropositive. From necropsied animals, the pathogen DNA was detected in two pigs at bronchus level and in another pig at tonsil. In this study, sow parity was not statistically related with sow seropositivity and piglet colonization. These results confirm that M. hyopneumoniae infection may be detected not only in nasal cavities of naturally infected suckling piglets but also at their low respiratory tract airways. Our results suggest that M. hyopneumoniae detection in lower and upper respiratory tract could be an indicator that respiratory problems associated to EP may start relatively early in the production system. In consequence, sow-to-piglet and/or piglet-to piglet transmission in farrowing barns should not be underestimated.  相似文献   

6.
Campylobacteriosis is the most commonly notified illness in New Zealand. Whilst the importance of commercial poultry in campylobacteriosis is well established, little is known about the possible role of chickens kept at home as a direct animal/faecal contact or consumption exposure pathway. The aim of this study was to determine the prevalence and genetic diversity of Campylobacter spp. in domestic backyard chicken flocks in the Canterbury region of New Zealand. Poultry faecal samples were collected from 35 domestic 'backyard' poultry flocks from urban and rural properties around the Canterbury Region of New Zealand. A total of 291 samples were collected and tested for the presence of thermotolerant Campylobacter spp. and positive isolates were analysed using pulsed-field gel electrophoresis (PFGE) using both SmaI and KpnI enzymes. There was a high prevalence of Campylobacter spp. with 86% of flocks testing positive. Campylobacter jejuni alone, Campylobacter coli alone and both C. jejuni and C. coli were detected in 20 (57%), 2 (6%) and 8 (23%) of the flocks respectively. SmaI/KpnI PFGE analysis identified 50 different genotypes across the 35 flocks. Genotype diversity richness was highest on the lifestyle block and farm properties with 43 different genotypes isolated, whilst urban properties displayed the least richness with 12 genotypes isolated. Rural flocks tended to have more different genotypes in a given flock than urban flocks. Comparison of the genotypes with the PulseNet Aotearoa Campylobacter database showed that 28 of the genotypes had previously been isolated from human cases of campylobacteriosis. Many of these were also indistinguishable from Campylobacter spp. previously isolated from retail chicken. Therefore, contact with backyard poultry or their faecal material is a potential additional infection pathway outside of exposure to the established pathways associated with the consumption of Campylobacter-contaminated commercial meat or foods cross-contaminated from contaminated poultry.  相似文献   

7.
OBJECTIVE: To enumerate the prevalence of Campylobacter isolates in the intestinal tract of market-weight swine raised in an integrated swine operation in Texas. SAMPLE POPULATION: Samples of cecal contents were collected from 595 pigs (mean body weight, 110 kg [242 lb]) at time of slaughter. Pigs were off-spring of Yorkshire-Landrace sows and Duroc or Hampshire boars. Pigs originated from 4 farrow-to-finish farms. PROCEDURE: During a 9-month period, visits were made to a slaughter plant to remove cecal contents from market-weight hogs. Samples were obtained from 50 pigs/visit from designated farms so that samples were obtained 3 times from pigs of each of 4 farms. Isolation of Campylobacter spp was accomplished by use of enrichment broth and restrictive media, using microaerophilic conditions. RESULTS: Campylobacter spp were isolated from 70 to 100% of the pigs, depending on the farm and the date the samples were collected. Campylobacter coli was isolated from 20 to 100% (mean, 60%) of samples, and C jejuni was isolated from 0 to 76% (mean, 31%) of samples. Campylobacter lari was isolated from 2 pigs. Concentrations of C coli or C jejuni ranged from 10(3) to 10(7) colony-forming units/g of cecal content. CONCLUSIONS AND CLINICAL RELEVANCE: Campylobacter coli generally is accepted as a common inhabitant of the intestinal tract of swine. However, analysis of results of this study suggests that a relatively high prevalence of C jejuni may be found in pigs raised on specific farms.  相似文献   

8.
The aim of the present study was to investigate feed allowances, body weight (BW), haematocrit, haemoglobin, plasma ionised calcium (iCa), sodium, potassium, pH and glucose concentration and faecal K/Na ratio in local growing pigs, sows and piglets kept by small-holder farmers in Laos. Starting hypotheses were that (1) local pigs are under fed, (2) BW is higher in pigs receiving supplementary feed and (3) the blood profile of pigs subjected to very poor nutrition is outside the normal range. On 54 pig-keeping smallholdings in Borikhamxay province, Lao PDR, daily feed allowances were weighed and BW recorded for 27 lactating sows, 54 piglets and 27 growing pigs. Blood samples were collected from the vena jugularis in all pigs. Feed supplementation did not affect BW, but plasma iCa concentration was outside the normal range for all pigs. There was a tendency for lower faecal K/Na ratio in Na-supplemented sows. The results confirm that local pigs in small-scale production systems in Laos suffer from poor nutrition. The most important challenge for farmers appears to be provision of more feed, particularly feed with a high Ca content.  相似文献   

9.
A survey was conducted to establish the prevalence of Campylobacter in pigs from an integrated commercial hog farm. This study was carried out in four different groups of pigs: 1) adult gilts (50); 2) pregnant sows (9); 3) piglets at day-of-birth (73); 4) weaned piglets (20). Rectal and/or caecal samples were collected from each pig. Campylobacter was cultured and enumerated from such samples using Bolton enrichment broth and Campy-Cephex agar plates. Both biochemical and serological tests were used to determine Campylobacter species. Gilts had a 76 per cent incidence of Campylobacter with a mean of 76.3 per cent for C. jejuni, 21 per cent for C. coli and 2.6 per cent for C. lari. Pregnant sows had a 100 per cent incidence of Campylobacter with a mean of 87 per cent for C. jejuni and 13 per cent for C. coli. Newborn piglets had a 57. 8 per cent incidence of Campylobacter, rising to 100 per cent by the time of weaning. Thus it appears that pigs, from the day of birth, are highly susceptible to colonisation by Campylobacter.  相似文献   

10.
Control of Isospora suis-induced coccidiosis on a swine farm   总被引:6,自引:0,他引:6  
Results of a program designed to control neonatal porcine coccidiosis on a total confinement, farrow-to-finish swine farm are reported. The control program consisted of washing, phenol disinfection, and steam cleaning of farrowing houses and treatment of sows with amprolium HCl before and after farrowing. Before initiation of the control program, 88.9% of the sows examined in the farrowing house were negative for coccidian oocysts, 9.9% were positive for Eimeria spp, and 1.2% were positive for Isospora suis. Most pigs nursing on sows before initiation of the control program had diarrhea at 5 to 10 days of age, which led to dehydration and weight loss. Morbidity was high, and mortality was moderate. Composite fecal samples from these litters were all positive (100%) for I suis. After initiation of the control program, 99.6% of the sows examined in the farrowing house were negative for coccidian oocysts and 0.4% were positive for Eimeria spp. Clinical signs of coccidiosis were rarely present in nursing pigs examined after the control program was initiated; however, I suis was still present in 19.8% of the composite fecal samples from pigs examined. An association between oocyst production in sows and I suis infections in pigs was not found in the present study. Oocysts of Eimeria spp were not found in the feces from the pigs.  相似文献   

11.
Chen Z  Mi R  Yu H  Shi Y  Huang Y  Chen Y  Zhou P  Cai Y  Lin J 《Veterinary parasitology》2011,181(2-4):113-119
A survey on prevalence of Cryptosporidium spp. in pigs at 12 farms in 8 suburban districts and 1 county of Shanghai was conducted under Sheather's sucrose flotation protocol and modified acid-fast stain methods from 2006 to 2009. A total of 2323 faecal samples were collected and Cryptosporidium spp. oocysts were detected in 800 samples (34.4%). Cryptosporidium was found in all 12 pig farms. Significant variations of prevalence were observed in different farms ranging from 14.1% to 90.6%. A follow-up survey on a positive pig farm for 13 consecutive months revealed that the most serious infection of Cryptosporidium spp. in pigs happened in winter and spring, and the lowest infection season was summer. Cryptosporidium spp. infection was mainly found in piglets within 2 months and no infection was found among those pigs of 90-180 days of age. The genotype analyses were carried out through PCR-RFLP and partial sequences analysis of small subunit ribosomal RNA (SSU rRNA) in some of the positive samples. Cryptosporidium suis (57/69, 82.6%), Cryptosporidium pig genotype II (6/69, 8.7%) and mixed infection of above two species/genotype (6/69, 8.7%) were found to be the main species/genotype in pigs in Shanghai area.  相似文献   

12.
A longitudinal study of Salmonella enterica infection was carried out in five Italian farrow-to-finish swine herds previously known to be infected by Salmonella. Five litters were randomly selected from each herd and in each litter six piglets were randomly selected and individually identified. Thus, the study included 30 pigs from each farm. At weaning, individual blood samples were collected for serological examination from all selected piglets and on the same day from all sows in the farrowing unit. Piglets were bled again at approximately 60, 90, 150, 210 and 270 days of life whereas the last blood sample was collected at slaughtering. In one of the herds, in which the duration of productive cycle was about 12 months, the last blood samples were collected at 350 days of life. With the same time scheduling, five pen pooled faecal samples were collected from each herd for bacteriological examination. At slaughtering, mesenteric lymph nodes were collected from each ear-tagged pig. Sero-prevalence (cut off S/P ratio 0.25) in sows varied from 93.8% to 100%. In four herds, sero-prevalence in piglets showed a similar profile with complete decline of maternal antibodies at day 60 and clear sero-conversion between day 90 and day 150. In one herd, sero-conversion was observed earlier and 56% of piglets were positive at day 90. The peak of sero-prevalence was observed between day 210 and day 270. Sero-prevalence at slaughtering varied from 66% to 100%. Salmonella was isolated from faecal samples in four of five herds. No Salmonella was isolated from mesenteric lymph nodes at slaughter in two of the herds. Culture prevalence from mesenteric lymph nodes in the other three herds ranged from 3.3% to 30%. This longitudinal study provides original information about epidemiological dynamics of Salmonella enterica infection in Italian swine herds in consideration of the unique extended fattening period typical of the Italian production.  相似文献   

13.
The objectives of this study were to determine the prevalence of antimicrobial resistance (AMR) in faecal Campylobacter spp. from lambs and adult sheep and associations between antimicrobial use (AMU) and AMR. A total of 275 faecal samples collected during initial and final visits from 51 sheep flocks, including one feedlot, across southern Ontario were tested for the presence of Campylobacter spp. Campylobacter jejuni was detected in 52% (143/275) of the faecal samples, Campylobacter coli in 7% (19/275), Campylobacter lari in 1% (2/275) and 2% (4/275) were non-speciated Campylobacter. Broth microdilution was used to test antimicrobial susceptibility of 162 isolates to nine antimicrobials. Campylobacter jejuni isolates (n = 142) were resistant to tetracycline (39%), ciprofloxacin (4%), nalidixic acid (4%) and telithromycin (1%). C. coli isolates (n = 19) were resistant to tetracycline (74%), and azithromycin, clindamycin, erythromycin, and telithromycin (5%). The C. lari isolate displayed resistance to nalidixic acid. No statistically significant associations were found between AMU and AMR during multivariate modelling in this study.  相似文献   

14.
Data were collected on the housing, management and disease factors in the weaning and finishing units of 49 integrated pig herds, 24 of them with a high incidence of arthritis at slaughter (case herds) and 25 with a low incidence (control herds). A median of 5.2 per cent (range 3.7 to 12.4 per cent) of the slaughtered pigs in the case herds had arthritis at meat inspection, compared with 2.2 per cent (range 0.3 to 2.8 per cent) in the control herds. In the farrowing units, high clinical sign scores for the lactating sows and piglets less than one week old and a low age at castration were associated with the case herds. In the weaning units, the herds with open partitions between the pens were 5.6 times more likely to be a case herd than the herds with solid walls. A higher age at weaning and moving the piglets at weaning from the farrowing pen instead of the sows decreased the likelihood of being a case herd. In the finishing units, a higher score for clinical signs, using a proper hospital pen, disinfecting the pens between the groups and using a feeding plan increased the likelihood of being a case herd. In total, 145 condemned joints, a median of four (up to six per herd), were collected at the slaughterhouse. In the case herds, 71 of 76 joints (93.4 per cent) had lesions related to osteochondrosis and in the control herds 66 of 69 joints (95.6 per cent) had such lesions. Only two of 11 joints from the case herds and one of 12 joints from the control herds that were examined bacteriologically were positive for Stapylococcus aureus and/or Streptococcus species.  相似文献   

15.
The aim of this study was to investigate faecal shedding and transmission of Campylobacter spp. in cohorts of cattle within a feedlot, to assess subsequent contamination of carcasses with this pathogen and to identify risk factors associated with faecal shedding of Campylobacter spp. A cohort of 133 heifers housed in four adjacent pens was examined over a five and a half month period, from entering the feedlot to slaughter. A parallel investigation of individual rectal faecal samples and pen environmental samples were taken at monthly intervals from November to February. The entire outer and inner surfaces of a carcass side of each animal were swabbed immediately following slaughter. Campylobacter spp. were isolated from 322 (54%) of the 600 rectal faecal samples. Campylobacter jejuni and C. coli accounted for 69 and 29.7% of the isolate recovered, respectively. A total of 159 environmental samples were examined, of these Campylobacter spp. was isolated from 46 samples (29%). Campylobacter jejuni and C. coli accounted for 35 and 59% of these isolates, respectively. Campylobacter spp. was not isolated from any of the dressed carcasses. Logistic regression indicated prevalence of Campylobacter spp. faecal shedding within pens was positively correlated to the pen, the month of sampling and the Campylobacter spp. contamination status of the pen dividing bars and the water trough surface. Campylobacter spp. should be considered as a pathogen shed in the faeces of a substantial proportion of feedlot cattle. However, with good hygienic practice during harvest, a very low level of this pathogen can be achieved on dressed carcasses.  相似文献   

16.
Ivermectin given in a single subcutaneous dose (300 micrograms/kg of body weight) was tested for activity against swine scabies (Sarcoptes scabiei). Efficacy was determined by recoveries of mites from ear scrapings and by observations of clinical signs. Treatment of infected sows 8 to 37 days before farrowing eliminated scabies from the sows and prevented its transmission to their offspring. Pigs farrowed by ivermectin-treated sows remained noninfected throughout the study regardless of whether they were treated with ivermectin at weaning. Placebo-treated sows remained infected and transmitted scabies to their offspring. Ivermectin treatment of pigs at weaning eliminated the infection, whereas placebo treatment did not. The placebo-treated pigs remained infected while in the nursery, but ivermectin treatment eliminated the infection when they were moved to the growing and finishing floor at 12 weeks of age. It appears that an effective control program for swine scabies using ivermectin could be based on a single treatment of the sows before farrowing. Any infection (epizootic) appearing in growing pigs could be controlled by a single treatment of all in-contact pigs.  相似文献   

17.
18.
Thirty nine pairs of full sibs were investigated over 6 parities in a long term study on the effects of late pregnancy feed allowance on the occurrence of agalactia post partum and on the performance of sows and piglets. A careful examination of all sows with a rectal temperature exceeding 39.5 degrees C was performed by a veterinarian within the first 48 h after farrowing. Milk-samples were taken from sows with elevated rectal temperatures and showing clinical symptoms of agalactia. During the last 15 days of gestation the sows in the control group were fed 3.4 kg daily and the sows in the experimental group 1.0 kg daily of a commercial type of diet. In 26.6% of the farrowings in the control group the sows were agalactic whereas the corresponding figure in the experimental group was 14.4%. On clinical examination udder changes were observed in a majority of the diseased sows in both groups. However, the agalactic sows in the control group were generally more affected, with lower water and feed consumption than in the experimental group. No effects of age of the sow (parity number) or length of the gestation period on the incidence of agalactia were demonstrated. The rectal temperature of agalactic sows was significantly higher than in the healthy sows already 1 day before farrowing. The agalactic sows farrowed a larger number of stillborn piglets, which indicates an early establishment of the disease. The number of weaned piglets at 6 weeks did not differ between agalactic and healthy animals. The interval from weaning to first oestrus was not influenced by agalactia in the preceding lactation.  相似文献   

19.
The spread of lactic acid bacterial strains to the environment and to newborn piglets was investigated after feeding of such strains to sows. Rifampicin resistant bacterial strains were fed to sows, 10(10) c.f.u. per day, during the period from 1 week before expected farrowing until 1 week after farrowing. Fecal samples from the sows and samples of litter were collected for bacteriological examination together with swabs from the pens, the skin of the sows, and from the rectum of the piglets. The test strains were only excreted in relatively low amounts in the feces of the sows, approximately 10(3)-10(6) c.f.u. per gram. They were not able to displace the normal lactic acid bacterial flora in the sows nor were they transmitted to the intestinal tract of the piglets to any significant extent. After the last administration the test strains disappeared from both feces, skin, and environment, indicating that no permanent colonization had taken place, although considerable differences in duration of persistence were noticed between test strains.  相似文献   

20.
The aim of this study was to evaluate the impact of the slaughter process on the Campylobacter (C.) coli prevalence on pig carcasses and finally pork. To detect C. spp., faecal samples, organ samples and surfaces of slaughter pigs were sampled. Additionally, various abattoir surfaces (n=208) and 227 pork and minced meat samples were included in our study.Whereas a high C. spp. prevalence (64.0%) was detectable in the faeces of slaughter pigs (all isolates were identified as C. coli), low detection rates were observed on pig carcasses after the slaughter process before the chilling period (21.1%).The impact of chilling reduced the detection rate of C spp. on pig carcasses even further to 0.8%. Only C. jejuni strains were isolated after the chilling process. Chilling and the associated drying of the skin are responsible for that massive reduction of C. spp prevalence. Significantly more C. spp. were isolated from livers compared to the corresponding carcasses. Only 5 out of 208 swab samples from different surfaces of the abattoir were C. coli positive. Bacteriological investigation could not detect any C. spp. strains from pork and minced pork meat.The low detection rates at the end of the slaughter and processing line indicate that pork may only play a minor role in the transmission of C. coli infections to humans. By genotyping C. coli-isolates from selected animals we were able to demonstrate three possible ways of contamination of the slaughter carcass surface. Genetically highly related strains were detectable on carcass surfaces of consecutively slaughtered animals. Faecal isolates and isolates from the carcass surface showed occasional high similarities. C. coli-genotypes from tonsils and genotypes from the corresponding slaughter carcasses formed a close cluster.  相似文献   

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