Occurrence of Erysipelothrix rhusiopathiae on pork and in pig slurry, and the distribution of specific antibodies in abattoir workers

Strains of Erysipelothrix rhusiopathiae isolated at 19 pig farms serving a certain abattoir, and on pork and in workers of this abattoir were studied. Mouse-pathogenic E. rhusiopathiae was found in pig slurry from two farms (11%). The strains belonged to serotypes 7 and 16 (both from the same farm) or were untypable. In pig slurry from the abattoir lairage only serotype 2 strains were found and all were pathogenic to mice. Mouse-pathogenic E. rhusiopathiae strains of serotype 2 were also recovered from 25 pork lions (25%). A mouse-pathogenic E. rhusiopathiae (serotype 2) strain was isolated from one of the 16 hand infections of slaughterhouse workers. The E. rhusiopathiae strains were phenotypically grouped by the API 50 CH system. Variations were demonstrated for the different serotypes. In 20 of 138 workers antibodies against E. rhusiopathiae were found; 14 had increased levels of IgG antibodies, seven had increased levels of IgM antibodies and one had an increased level of both.     

2012–2015年江淮地区猪丹毒杆菌分离株血清型、spaA基因遗传进化及PFGE基因型分析

【目的】了解2012–2015年江淮地区猪丹毒杆菌分离株血清型分布、spaA基因遗传进化关系和基因分型特征。【方法】收集临床分离鉴定的42株猪丹毒杆菌,应用琼脂扩散沉淀实验、PCR扩增和序列分析技术、脉冲场凝胶电泳分型技术(PFGE)分别测定分离株的血清型、spaA基因遗传变异性及PFGE基因型。【结果】42株猪丹毒杆菌分离株血清型均为1a型;spaA基因与猪丹毒杆菌国内外参考株核苷酸序列相似性为98.5%–100%,分离株在第609 bp处出现T突变为G、769 bp处C突变为A,对应的氨基酸第203位Ile突变为Met、第257位Leu突变为Ile,为Met-203、Ile-257型;分离株形成8个PFGE基因型,相似度达88.8%–100%,优势基因型为ER2 (54.8%),弱毒疫苗G4T10和GC42株独立为同一个基因型。【结论】江淮地区致病猪丹毒杆菌流行血清型为1a型,spaA基因相似性高,分离株变异小、源于同一克隆系,Met-203、Ile-257型菌株致病力强,是江淮地区猪丹毒发生与流行的主要致病菌型。     

The detection and recovery of Erysipelothrix spp. in meat and abattoir samples in Western Australia

AIMS: To investigate the occurrence of Erysipelothrix rhusiopathiae and other Erysipelothrix spp. in abattoir and meat samples in Western Australia. METHODS AND RESULTS: Samples were collected from various parts of pig and sheep carcasses, as well as different sections of slaughtering line, pen soil and effluent. Previously evaluated culture methods were applied for the isolation of Erysipelothrix spp., in conjunction with phenotypic and genotypic detection and identification procedures. Of 109 samples from the two abattoirs, 35 (32.1%) were Erysipelothrix genus-specific PCR-positive. These came from swabs of animal exterior surfaces and joints, slaughtering areas, pig pen soil and abattoir effluent. Four samples (3.7%) from sheep arthritic joints and pig abattoir effluent were also E. rhusiopathiae species-specific PCR-positive. Of 123 carcass washing samples, 12 (9.8%) were genus-specific PCR-positive, and these came from all five kinds of meat samples tested, including beef, lamb, mutton, pork and chicken. Four of them (3.3%) were also species-specific PCR-positive. A total of 25 isolates was recovered from the samples, of which seven were identified as E. rhusiopathiae, seven were consistent with E. tonsillarum, and the remaining 11 were other species of Erysipelothrix. CONCLUSIONS: Erysipelothrix spp. can still be isolated and identified from specimens of animal origin with relative ease, provided that appropriate cultural and molecular procedures are used. Clinical microbiology laboratories may need to improve their diagnostic protocols. SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirms that E. rhusiopathiae and other species of Erysipelothrix continue to colonize and contaminate farmed animals and animal products. Erysipelothrix infection still poses a potential threat to the economy of the farmed animal industry, as well as being a potential human public health hazard.     

Clonal relationships among Escherichia coli serogroup 06 isolates from human and animal infections

The clonal relationship of thirty E. coli strains of 0 antigen serotype 06 isolated from human, dog, pig or cow infections were investigated. Two main clones with serotypes 06 : H1 or 06 : H31, H- were identified. Isolates from humans, dogs, pigs and cows were found in both clones, indicating that animals are a possible source for human extraintestinal Escherichia coli strains. Two human ETEC (06 : H16) and two pig isolates (06 : H10) were not related to the 06 : H1 or 06 : H31, H- E. coli clones.     

Occurrence and strain diversity of thermophilic campylobacters in cattle of different age groups in dairy herds

AIMS: To investigate the occurrence and numbers of thermophilic campylobacters excreted by cattle in dairy herds, and to assess the strain diversity within herds. METHODS AND RESULTS: Faecal samples from 15 animals at each of 24 cattle farms were cultured quantitatively for thermophilic campylobacters and 23% of animals and 83% of farms were positive for Campylobacter jejuni. Young animals had a higher prevalence and higher faecal concentration than older animals. Serotyping and pulsed field gel electrophoresis (PFGE) of isolates showed that the most common serotypes were 2, 4-complex and 11. Serotype 2 was especially prevalent among calves (68% of the positive calves). In eight of the 20 positive herds, all isolates had the same sero- and PFGE type while, in the other herds, two to five different types were isolated. CONCLUSIONS: Significant differences were found between age groups in relation to the prevalence and numbers of excreted campylobacters, serotype distribution and strain diversity. The relatively few different strains in each herd indicate that transmission between animals is common. SIGNIFICANCE AND IMPACT OF THE STUDY: The high prevalence on cattle farms of the human pathogen C. jejuni and the wide distribution of serotype 2, the most common serotype among Danish patients, indicate that cattle might be an important reservoir for human infections. The ability of this serotype to colonize calves in high numbers further indicates that serotype 2 strains may have an advantage over other serotypes.     

山东省某地区奶牛源大肠埃希菌的血清型、耐药特性及分子特性

【目的】旨在对从山东省某地区4个健康奶牛养殖场分离到的大肠埃希菌进行优势血清型、耐药特性、Ⅰ类整合子基因盒携带情况以及系统进化群分析。【方法】采集194份来自山东省某地区4个规模化奶牛场奶牛新鲜粪便样品,进行大肠埃希菌分离和鉴定,利用常用大肠埃希菌诊断血清进行血清型鉴定;利用10%的绵羊血平板检测溶血性;利用K-B法检测对14种常规抗菌药物的敏感性;利用聚合酶链式反应(PCR)检测革兰阴性菌常见的6大类24种耐药基因、Ⅰ类整合子基因盒结构并对目的条带测序分析;利用细菌多位点序列分型(Multilocus sequence typing,MLST)技术分析大肠埃希菌的ST型并使用eBURST v3软件分析菌株之间的克隆关系。【结果】从194份新鲜粪便样品中分离到171株大肠埃希菌,其中主要为致病性(19.9%)和侵袭性大肠埃希菌(17.0%),优势血清型分别为O128:K67(12/171)和O143:K7(12/171)。另外,具有溶血性的大肠埃希菌阳性率为9.4%(16/171);药敏试验结果显示多重耐药菌株的比率为22.2%,其中对氨苄西林耐药率最高为33.9%,四环素次之,为24.0%;PCR检测耐药基因和整合子结果显示,59.1%的菌株携带β-内酰胺类耐药基因blaTEM,59.1%的菌株携带氨基糖苷类耐药基因ant(2′),未检测到四环素耐药基因tetA和tetB;Ⅰ类整合子的阳性率为4.1%(7/171),dfrA12-aadA2-sul1为优势基因盒结构(4/171);MLST将大肠埃希菌分为8种ST型,其中,ST155(10/171)和ST58(45/171)形成一个克隆复合物且没有发现新的ST型。【结论】本研究证实,从该地区规模化健康奶牛场新鲜粪便中分离到的大肠埃希菌优势血清型为O128:K67和O143:K7;少部分大肠埃希菌具有溶血性;仅对氨苄西林、四环素等具有较高的耐药率;优势基因盒结构为dfrA12-aadA2-sul1;MLST分型显示不同奶牛场分离出亲缘关系较近的菌株,其分布具有多态性,血清型与ST型之间无相关性。本研究表明源自表观健康的奶牛的大肠埃希菌存在多重耐药现象,具有食品公共卫生安全隐患,该研究对于提升规模化奶牛场奶制品的安全生产与质量评估具有一定的理论指导意义。     

Phenotypic and genotypic characterization of Salmonella spp. Isolated from pigs and their farm environment in Korea

This study's objective was to determine the prevalence of Salmonella spp. in pigs and their farm environments in Korea, and to investigate the relationship between the strains based on their phenotypic and genotypic characteristics. A total of 36 Salmonella spp. were isolated in this study: 18 isolates from 492 pigs (3.7%) and 18 isolates from 418 (4.3%) farmhouse environmental samples from 16 different pig farms. Of the Salmonella strains isolated from the numerous environmental samples, the highest prevalence was observed in slurry or manure, followed by partitions, farmer's hands, floors, water/ nipples, ventilation sources, and feed, respectively. All the Salmonella isolates originating from different farms were genetically distinct. In three farms, however, identical phage types and pulse-field gel electrophoresis patterns were observed among Salmonella isolates from pig feces and environmental samples. This study suggests that environments contaminated with Salmonella could pose an infection risk to pigs on pig farms.     

Multiyear study of sludge application to farmland: prevalence of bacterial enteric pathogens and antibody status of farm families

We describe our experience with the isolation of salmonellae from sewage sludge from four treatment plants in different geographic areas of Ohio. Over 3 years, we isolated salmonellae 50 times from 311 sludge samples. Most isolations were made after enrichment in Selenite broth (BBL Microbiology Systems, Cockeysville, Md.). The largest proportion of isolations came from the plant serving the population of Columbus, a large metropolitan area. A significantly greater number of isolations from this plant were made during the first quarter of the year. Twenty-one different serotypes were isolated, along with five untypable strains. The most frequently isolated serotype was Salmonella infantis. Five of the strains were multiply resistant to antibiotics. We also describe the prevalence of antibodies to salmonellae in members of the families residing on the farms in the study. It was found that antibodies to group C salmonellae predominated.     

Multiyear study of sludge application to farmland: prevalence of bacterial enteric pathogens and antibody status of farm families.

We describe our experience with the isolation of salmonellae from sewage sludge from four treatment plants in different geographic areas of Ohio. Over 3 years, we isolated salmonellae 50 times from 311 sludge samples. Most isolations were made after enrichment in Selenite broth (BBL Microbiology Systems, Cockeysville, Md.). The largest proportion of isolations came from the plant serving the population of Columbus, a large metropolitan area. A significantly greater number of isolations from this plant were made during the first quarter of the year. Twenty-one different serotypes were isolated, along with five untypable strains. The most frequently isolated serotype was Salmonella infantis. Five of the strains were multiply resistant to antibiotics. We also describe the prevalence of antibodies to salmonellae in members of the families residing on the farms in the study. It was found that antibodies to group C salmonellae predominated.     

一种新的人兽共患传染病——狐阴道加德纳氏菌病的研究 V.狐阴道加德纳氏菌菌株的血清分型研究

将我国6个省(区)、13个主要狐场分离的145株狐阴道加德纳氏菌,进行抗原性、免疫原性测定,从每场分离菌中选出1～3个优良株进行血清型研究。凝集素交叉吸收试验证实,选出的26株菌可划分为3个血清型,以此3个血清型代表株制备因子血清,余下119株菌中,108株在所划分的3个血清型内,11株未能定型。在3个血清型中,Ⅰ型菌株数占定型菌数的79.1％,因而确定,Ⅰ型菌是国内狐场狐阴道加德纳氏菌主要流行型。试验还明确了从貉分离的5株、水貂分离的4株、犬分离的2株阴道加德纳氏菌也属于血清Ⅰ型。将3个血清型代表菌株制成超声抗原,经免疫琼脂扩散试验证实,各型抗原与同型或异型免疫血清均可形成一条明显的融合沉淀线,表明各型菌间有共同抗原成分。同型菌免疫琼脂扩散试验表明,各株菌形成的沉淀线完全融合,从而证实了血清分型的可靠性。     

苏北地区规模化猪场产肠毒素大肠杆菌的分离鉴定及灭活疫苗效果评估

[目的]产肠毒素大肠杆菌(Enterotoxigenic Escherichia coli,ETEC)是引起仔猪腹泻的重要病原菌,本研究通过调查苏北地区规模化猪场ETEC的流行情况,分析其生物学特性,研制具有免疫保护效果的优势血清型菌株的灭活疫苗,以期对苏北地区ETEC的防控提供参考。[方法]从苏北地区规模化猪场采集3-30日龄的仔猪新鲜粪样、肛拭子及小肠组织样,分离出ETEC,对分离菌株进行血清型鉴定、耐药性测定、小鼠致病力测定;最后通过动物免疫试验研究优势血清型菌株灭活疫苗对小鼠的免疫保护效果。[结果]从21个规模化猪场采集病料562份,通过PCR鉴定及测序得到141株ETEC;血清凝集试验鉴定出85株菌的O抗原血清型,其中08、0101和0128为优势血清型,占定型菌株的61.2%(52/85),其他血清型包括09、03、020、0148、0149等;分析141株ETEC对14种常见抗生素的耐药情况,得出分离株对新霉素、红霉素、四环素、庆大霉素、强力霉素、阿莫西林、甲氧苄啶/磺胺甲恶唑高度耐药,耐药率均高达80%以上;对恩诺沙星敏感性较高,敏感率达50.4%(71/141);对多粘菌素B和头孢噻肟中介耐药,占比分别为66%(93/141)和51.8%(73/141);多重耐药现象严重,其中10重耐药的菌株占比最大,为19%(27/141);小鼠攻毒试验测得08血清型强毒株YC-6的半数致死量(median lethal dose,LD50)为1.4×10^7 CFU/只,最低致死量(minimum lethal dose,MLD)为3×10^7 CFU/只;08血清型强毒株YC-6和0101血清型强毒株LYG-3制备的单价灭活疫苗对小鼠的保护率均达到100%,因此利用08血清型强毒株YC-6和0101血清型强毒株LYG-3研制二价灭活疫苗,结果显示该二价疫苗对感染不同血清型ETEC小鼠的保护率在83%以上。[结论]本研究通过对苏北地区ETEC的流行病学调查,得出其优势血清型,并研制出针对对优势血清型免疫保护效果较好的二价灭活疫苗,给临床ETEC的监测和防控提供参考。     

Opsonic and protective activity of five human IgM monoclonal antibodies reactive with lipopolysaccharide antigen of Pseudomonas aeruginosa

Abstract International Antigen Typing Schema (IATS) serotypes 1, 2, 5, 6, 8 and 11 comprise approximately vn80% of Pseudomonas aeruginosa strains isolated from blood, wounds and respiratory specimens. Five human immunolgobulin M (IgM) monoclonal antibodies (MAbs) reactive with lipopolysaccharide O antigens of these IATS serotypes were studies in an opsonophagocytic assay. The assay employed human polymorphonuclear leukocytes, 2% guinea pig serum as the complement source and MAb. Each MAb promoted killing of inoculum of the homologous LPS serotype. The opsonic activity of each MAb was complement-dependent. In a murine model of Pseudomonas burn wound sepsis the LD₅₀ of five strains of P. aeuruginosa was increased ≥ 22-fold by MAb-treatment (1.0 mg/kg). The mean effective dose of the five MA0bs in mice challenged with approximately 10 LD₅₀ of the homologous LPS serotype ranged from < 0.01 mg/kg to 1.00 mg/kg.     

Opsonic and protective activity of five human IgM monoclonal antibodies reactive with lipopolysaccharide antigen of Pseudomonas aeruginosa

International Antigen Typing Schema (IATS) serotypes 1, 2, 5, 6, 8 and 11 comprise approximately 80% of Pseudomonas aeruginosa strains isolated from blood, wounds and respiratory specimens. Five human immunoglobulin M (IgM) monoclonal antibodies (MAbs) reactive with lipopolysaccharide O antigens of these IATS serotypes were studied in an opsonophagocytic assay. The assay employed human polymorphonuclear leukocytes, 2% guinea pig serum as the complement source and MAb. Each MAb promoted killing of inoculum of the homologous LPS serotype. The opsonic activity of each MAb was complement-dependent. In a murine model of Pseudomonas burn wound sepsis the LD50 of five strains of P. aeruginosa was increased greater than or equal to 22-fold by MAb-treatment (1.0 mg/kg). The mean effective dose of the five MAbs in mice challenged with approximately 10 LD50 of the homologous LPS serotype ranged from less than 0.01 mg/kg to 1.00 mg/kg.     

Antibodies to selected viral and bacterial pathogens in European wild boars from southcentral Spain

Serum samples from 78 European wild boars (Sus scrofa) harvested during the 1999-2000 hunting season were tested for antibodies to Brucella spp., classical swine fever virus, Erysipelothrix rhusiopathiae, Haemophilus parasuis, Leptospira interrogans serovar pomona, Mycoplasma hyopneumoniae, pseudorabies virus (PRV), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus, Salmonella serogroups B, C, and D, Streptococcus suis, and swine influenza virus (SIV) serotypes H1N1 and H3N2. Samples were collected from Sierra Morena and Montes de Toledo in southcentral Spain. Antibodies were detected to PRV (36%), L. interrogans serovar pomona (12%), PPV (10%), E. rhusiopathiae (5%), SIV serotype H1N1 (4%), Salmonella serogroup B (4%), and Salmonella serogroup C (3%). Our results suggest that more research is needed to describe the epidemiology of infectious diseases of Spanish wild boars.     

Serotypes among Neisseria meningitidis serogroups B and C strains isolated in Canada

Antisera made to prototype serogroup B strains of Neisseria meningitidis were used to serotype, by agar gel double diffusion, 262 meningococcal serogroups B and C strains isolated in Canada. The strains included 93 from patients and 169 from carriers. Serotype 2 was associated with 39 of 75 (52%) of group B strains and 14 of 18 (77.8%) of group C strains isolated from patients. The group B strains were mainly (87.2%) serotype 2b, while the majority (92.2%) of group C strains was serotype 2a. Other serotypes (including a new provisional serotype) represented 25.3 and 5.5% of groups B and C strains, respectively. The new serotype accounted for 13% of the group B strains. Approximately 23% of the strains isolated from patients were nontypable. The distribution of serotype 2, nontype 2 (other serotypes), and nontypable strains isolated from carriers was 2.1, 36.6, and 61.3%, respectively, for group B meningococci and 22.2, 29.6, and 48.25, respectively, for group C meningococci. Serotype 11 was the most prominent of the strains isolated from carriers. Approximately 7% of all the strains were multiple serotypes. Serotype 2 is an important virulence marker associated with meningococcal groups B and C disease in Canada, with serotypes 2a and 2b being markedly associated with groups C and B meningococcal disease, respectively.     

The diversity of Escherichia coli serotypes and biotypes in cattle faeces

AIM: To study the diversity of commensal Escherichia coli populations shed in faeces of cattle fed on different diets. METHODS AND RESULTS: Thirty Brahman-cross steers were initially fed a high grain (80%) diet and then randomly allocated into three dietary treatment groups, fed 80% grain, roughage, or roughage + 50% molasses. Up to eight different E. coli isolates were selected from primary isolation plates of faecal samples from each animal. Fifty-two distinct serotypes, including nine different VTEC strains, were identified from a total of 474 E. coli isolates. Cattle fed a roughage + molasses diet had greater serotype diversity (30 serotypes identified) than cattle fed roughage or grain (21 and 17 serotypes identified respectively). Cluster analysis showed that serotypes isolated from cattle fed roughage and roughage + molasses diets were more closely associated than serotypes isolated from cattle fed grain. Resistance to one or more of 11 antimicrobial agents was detected among isolates from 20 different serotypes. Whilst only 2.3% of E. coli isolates produced enterohaemolysin, 25% were found to produce alpha-haemolysin. CONCLUSIONS: Diverse non-VTEC populations of E. coli serotypes are shed in cattle faeces and diet may affect population diversity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides new information on the serotype diversity and phenotypic traits of predominant E. coli populations in cattle faeces, which could be sources of environmental contamination.     

Differences in the population structure of invasive Streptococcus suis strains isolated from pigs and from humans in The Netherlands

Streptococcus suis serotype 2 is the main cause of zoonotic S. suis infection despite the fact that other serotypes are frequently isolated from diseased pigs. Studies comparing concurrent invasive human and pig isolates from a single geographical location are lacking. We compared the population structures of invasive S. suis strains isolated between 1986 and 2008 from human patients (N?=?24) and from pigs with invasive disease (N?=?124) in The Netherlands by serotyping and multi locus sequence typing (MLST). Fifty-six percent of pig isolates were of serotype 9 belonging to 15 clonal complexes (CCs) or singleton sequence types (ST). In contrast, all human isolates were of serotype 2 and belonged to two non-overlapping clonal complexes CC1 (58%) and CC20 (42%). The proportion of serotype 2 isolates among S. suis strains isolated from humans was significantly higher than among strains isolated from pigs (24/24 vs. 29/124; P<0.0001). This difference remained significant when only strains within CC1 and CC20 were considered (24/24 vs. 27/37,P?=?0.004). The Simpson diversity index of the S. suis population isolated from humans (0.598) was smaller than of the population isolated from pigs (0.765, P?=?0.05) indicating that the S. suis population isolated from infected pigs was more diverse than the S. suis population isolated from human patients. S. suis serotype 2 strains of CC20 were all negative in a PCR for detection of genes encoding extracellular protein factor (EF) variants. These data indicate that the polysaccharide capsule is an important correlate of human S. suis infection, irrespective of the ST and EF encoding gene type of S. suis strains.     

Rapid Serodiagnosis of Mycobacterium avium-intracellulare Complex Infection by ELISA with Cord Factor (Trehalose 6, 6′-Dimycolate), and Serotyping Using the Glycopeptidolipid Antigen

Mycobacterium avium-intracellulare complex (MAC) is one of the most important opportunistic pathogens, particularly in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to determine whether an enzyme-linked immunosorbent assay (ELISA) using trehalose 6,6′-dimycolate (TDM) as an antigen can be used for the rapid serodiagnosis of MAC infection. We also identified MAC serotypes by ELISA using serotype-specific glycopeptidolipid (GPL) antigen. To confirm our findings, the thin-layer chromatographic (TLC) behavior of serotype-specific GPL of the strains isolated from MAC-infected patients was also tested. Forty patients infected with MAC and 30 healthy controls were tested. Thirty-two of the 40 MAC-infected patients had higher titers of serum antibodies against MAC TDM than against MTB TDM, while all 30 healthy control sera were unreactive to MAC TDM and MTB TDM. Results of the GPL ELISA indicated that 20 of the 40 MAC-infected patients' sera were reactive against serotype 4 GPL, 3 against serotype 8 GPL, and 1 against serotype 16 GPL. A TLC analysis of the GPL of the 40 MAC isolates showed that 16 strains were of serotype 4, 5 of serotype 8, and 2 of serotype 16. Results of the GPL ELISA were in good accord with those of the TLC analysis for most patients. Our findings suggest that ELISA using TDM is useful for rapid serodiagnosis of MAC infection, and that complementary ELISA testing using serotype-specific GPL gives additional detailed information concerning MAC serotypes.     

Phenotypic and molecular typing of Salmonella strains reveals different contamination sources in two commercial pig slaughterhouses

This study aimed to define the origin of Salmonella contamination on swine carcasses and the distribution of Salmonella serotypes in two commercial slaughterhouses during normal activity. Salmonellae were isolated from carcasses, from colons and mesenteric lymph nodes of individual pigs, and from the slaughterhouse environment. All strains were serotyped; Salmonella enterica serotype Typhimurium and Salmonella enterica serotype Derby isolates were additionally typed beyond the serotype level by pulsed-field gel electrophoresis (PFGE) and antibiotic resistance profiling (ARP); and a subset of 31 serotype Typhimurium strains were additionally phage typed. PFGE and ARP had the same discriminative possibility. Phage typing in combination with PFGE could give extra information for some strains. In one slaughterhouse, 21% of the carcasses were contaminated, reflecting a correlation with the delivery of infected pigs. Carcass contamination did not result only from infection of the corresponding pig; only 25% of the positive carcasses were contaminated with the same serotype or genotype found in the corresponding feces or mesenteric lymph nodes. In the other slaughterhouse, 70% of the carcasses were contaminated, and only in 4% was the same genotype or serotype detected as in the feces of the corresponding pigs. The other positive carcasses in both slaughterhouses were contaminated by genotypes present in the feces or lymph nodes of pigs slaughtered earlier that day or from dispersed sources in the environment. In slaughterhouses, complex contamination cycles may be present, resulting in the isolation of many different genotypes circulating in the environment due to the supply of positive animals and in the contamination of carcasses, probably through aerosols.