Mycoplasma hyopneumoniae infection dynamics in naïve replacement gilts introduced to positive farms.

This study was designed to characterize the dynamics of infection of Mycoplasma hyopneumoniae in naïve replacement gilts after introduction to positive systems. Ninety-eight naïve gilts were monitored in three positive commercial farms (A, B, and C). The näive gilts were housed for 21 days in pens adjacently located to older gilt cohorts (named seeders), which have been naturally exposed to the positive farms. The infection dynamics was evaluated by PCR and ELISA, from laryngeal swabs and serum samples, respectively. Samples were collected at 150 (arrival), 165, 180, 210, 240, 270, 300 days of age (doa), and pre-farrowing. Infection occurred rapidly on farms A and B, taking 25.2 and 23.9 days for 95% of gilts to be PCR positive, respectively. There was no influence on the number of seeders at the time of exposure, but their absence (farm C) could explain the extended period it took for gilts to get infected (69.4 days). On average, it took 162.2 days after the first PCR detection for 85% of gilts to stop shedding the bacterium. The serology results were consistent with the herd infection curve. At pre-farrowing, 100% of gilts seroconverted and 36.7% remained PCR positive. A total of 1.33% of piglets were positive at weaning. Fifteen variants were detected among the three farms by MLVA. The acclimation protocol was efficient and easy to perform, and the presence of seeders was likely critical for early acclimation for M. hyopneumoniae.

Economic impact of chronic pleural lesions and consequent disqualification of carcasses for export during inspection in swine slaughterhouses / Impacto econômico de lesões pleurais crônicas e consequente desqualificação de carcaças para exportação durante inspeção em frigoríficos de suínos

Chronic pleuritis is the main reason for sending pig carcasses to the Department of Final Inspection (DIF), condemnation and led to economic losses to industries and producers. Most pleura lesions detected after slaughter are sequelae from bacterial infections by agents that do not pose risks to pork consumers. The objective of the present study was to generate science-based information for decision making in the evaluation and destination of chronic pleuritis by the Federal Inspection Service (SIF). Therefore, 200 carcasses, with and without pleurisy, from a swine slaughterhouse with SIF were assessed following the visual classification of the inspection agent. The study was carried out in two stages. In stage 1, 50 carcasses with pneumonic lesions adjacent to chronic pleuritis and 50 carcasses with only chronic pleuritis lesions were evaluated, through macroscopy, histopathology, and bacterial culture. In stage 2, 50 swine carcasses with chronic pleuritis and 50 without this lesion were sampled in the parietal pleura region to bacterial culture and PCR. The economic impact of not exporting these carcasses with chronic pleuritis was also assessed. Considering the stages of evolution of the lesions, the macroscopic examination showed high correlation with the histological examination. There was no bacterial isolation through pleural swabs, regardless of the presence or not of adjacent pulmonary lesions. Isolation was restricted to the adjacent pulmonary lesions of 70% samples, with Pasteurella multocida type A found in 48% of them, followed by P. multocida type D and Streptococcus suis in 12%, and Actinobacillus pleuropneumoniae in 3%. Only Streptococcus suis DNA was detected in 5/100 samples, with no correspondence to the isolation of viable bacteria. The reliability demonstrated in the macroscopic evaluation carried out during inspection, the absence of viable bacteria in the chronic pleural lesions, and the negative economic impact suggest that carcasses with chronic pleuritis can be submitted to pleura removal, with no need of sending to DIF.

Pleurite crônica é a principal causa do desvio de carcaças de suínos para o Departamento de Inspeção Final (DIF), podendo causar condenação e prejuízos econômicos às indústrias e produtores. A maioria das lesões de pleura detectadas após o abate são sequelas de infecções bacterianas por agentes que não oferecem riscos aos consumidores de carne suína. O objetivo do presente estudo foi gerar informações científicas para a tomada de decisão na avaliação e destino da pleurite crônica pelo Serviço de Inspeção Federal (SIF). Para tanto, 200 carcaças, com e sem pleurisia, provenientes de um frigorífico de suínos com SIF foram avaliadas seguindo a classificação visual do agente fiscalizador. O estudo foi realizado em duas etapas. No estágio 1, 50 carcaças com lesões pneumônicas adjacentes à pleurite crônica e 50 carcaças apresentando somente lesões de pleurite crônica foram avaliadas macroscopicamente, por histopatologia e cultura bacteriana. No estágio 2, 50 carcaças suínas com pleurite crônica e 50 sem esta lesão foram amostradas na região da pleura parietal para cultura bacteriana e PCR. O impacto econômico de não exportar essas carcaças com pleurite crônica também foi avaliado. Considerando os estágios de evolução das lesões, o exame macroscópico apresentou alta correlação com o exame histológico. Não houve isolamento bacteriano por meio de swabs pleurais, independentemente da presença ou não de lesões pulmonares adjacentes. O isolamento foi restrito às lesões pulmonares adjacentes de 70% das amostras, sendo Pasteurella multocida tipo A encontrado em 48% delas, seguido por P. multocida tipo D e Streptococcus suis em 12%, e Actinobacillus pleuropneumoniae em 3%. Apenas DNA de Streptococcus suis foi detectado em 5/100 amostras, sem correspondência com o isolamento de bactérias viáveis. A confiabilidade demonstrada na avaliação macroscópica realizada durante a inspeção, a ausência de bactérias viáveis nas lesões pleurais crônicas e o impacto econômico negativo sugerem que carcaças com pleurite crônica podem ser submetidas à remoção da pleura, sem necessidade de envio para DIF.

Insights about the epidemiology of Salmonella Typhimurium isolates from different sources in Brazil using comparative genomics.

BACKGROUND: Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is an important zoonotic agent worldwide. The aim of this work was to compare genetically 117 S. Typhimurium isolated from different sources over 30 years in Brazil using different genomics strategies. RESULTS: The majority of the 117 S. Typhimurium strains studied were grouped into a single cluster (≅ 90%) by the core genome multilocus sequence typing and (≅ 77%) by single copy marker genes. The phylogenetic analysis based on single nucleotide polymorphism (SNP) grouped most strains from humans into a single cluster (≅ 93%), while the strains isolated from food and swine were alocated into three clusters. The different orthologous protein clusters found for some S. Typhimurium isolated from humans and food are involved in metabolic and regulatory processes. For 26 isolates from swine the sequence types (ST) 19 and ST1921 were the most prevalent ones, and the ST14, ST64, ST516 and ST639 were also detected. Previous results typed the 91 S. Typhimurium isolates from humans and foods as ST19, ST313, ST1921, ST3343 and ST1649. The main prophages detected were: Gifsy-2 in 79 (67.5%) and Gifsy-1 in 63 (54%) strains. All of the S. Typhimurium isolates contained the acrA, acrB, macA, macB, mdtK, emrA, emrB, emrR and tolC efflux pump genes. CONCLUSIONS: The phylogenetic trees grouped the majority of the S. Typhimurium isolates from humans into a single cluster suggesting that there is one prevalent subtype in Brazil. Regarding strains isolated from food and swine, the SNPs' results suggested the circulation of more than one subtype over 30 years in this country. The orthologous protein clusters analysis revealed unique genes in the strains studied mainly related to bacterial metabolism. S. Typhimurium strains from swine showed greater diversity of STs and prophages in comparison to strains isolated from humans and foods. The pathogenic potential of S. Typhimurium strains was corroborated by the presence of exclusive prophages of this serovar involved in its virulence. The high number of resistance genes related to efflux pumps is worrying and may lead to therapeutic failures when clinical treatment is needed.

Investigation of Listeria monocytogenes, Salmonella enterica and Yersinia enterocolitica in pig carcasses in Southern Brazil / Pesquisa de Listeria monocytogenes, Salmonella enterica and Yersinia enterocolitica em carcaças de suínos no sul do Brasil

The intensification of pig production and advances in the sanitary control of herds profoundly changed the profile of risk attributed to pork consumption. In the actual scenario, most microorganisms related to macroscopic lesions observed in the post mortem inspection are not transmitted by food, while foodborne bacteria of importance to consumer health do not cause macroscopic lesions. In Brazil, the "Ministério da Agricultura, Pecuária e Abastecimento" requested a scientific opinion on the prioritizing of pathogens potentially transmitted by unprocessed pork. After conducting a qualitative risk assessment, only Salmonella enterica was classified as of high risk to consumers. The present study was part of the validation step of the risk assessment and aimed to investigate the frequency of S. enterica, Yersinia enterocolitica and Listeria monocytogenes and hygienic-sanitary indicators in pig carcasses of pigs rose under intensive production and slaughtered under the Federal Inspection System in three slaughterhouses located in Southern Brazil. Additionally, the antimicrobial resistance profile of the isolated pathogens was also investigated. A total of 378 carcasses were sampled by superficial sponges before the chilling step in three slaughterhouses. Samples were investigated for the presence of the three aforementioned pathogens and subjected to enumeration of Colony Formation Units (log CFU.cm-1) of total aerobic mesophiles (TAM) and Enterobacteriaceae. Salmonella strains were tested by disc diffusion test for resistance to eleven antimicrobials. There were significantly statistical differences (p<0.0001) on the median counts of both indicators between the slaughterhouses. The median of TAM was very close for Slaughterhouses A and B: 1.573 log CFU.cm-1 and 1.6014 log CFU.cm-1, respectively. While in Slaughterhouse C, a higher TAM median was detected (2.216 log CFU.cm-1)...(AU)

A intensificação da produção de suínos e os avanços no controle sanitário dos rebanhos alterou de forma importante o perfil de risco do consumo de carne suína. No cenário atual, a maioria dos microrganismos causadores de lesões macroscópicas detectáveis na inspeção post mortem não são transmissíveis por alimentos, enquanto bactérias de importância como causadoras de doenças transmitidas por alimentos não causam lesões macroscópicas. No Brasil, o Ministério da Agricultura, Pecuária e Abastecimento solicitou uma opinião científica sobre a priorização de patógenos potencialmente transmitidos pela carne suína in natura. Após conduzir uma avaliação de risco qualitativa, apenas Salmonella enterica foi classificada como de alto risco para o consumidor. O presente estudo foi parte da etapa de validação da avaliação de risco e objetivou: investigar a frequência de S. enterica, Yersinia enterocolitica e Listeria. monocytogenes; e enumerar indicadores higiênico-sanitários em carcaças de suínos abatidos sob inspeção federal em frigoríficos dedicados ao abate de suínos sob sistema intensivo de criação no sul do Brasil. Além disso, o perfil de resistência a antimicrobianos dos patógenos isolados foi investigado. A superfície de um total de 378 carcaças foi amostrada por esponjas, na etapa de pré-resfriamento em três matadouros frigoríficos (A, B, C). As amostras foram investigadas quanto à presença dos três patógenos acima mencionados e quanto à enumeração de Unidades Formadoras de Colônia (log UFC.cm-1) de mesófilos aeróbios totais (MAT) e Enterobacteriaceae. As cepas isoladas de Salmonella foram testadas quanto à resistência a onze antimicrobianos pela técnica de disco difusão. As medianas de contagem de ambos os indicadores apresentaram diferença significativa (p<0,0001) entre matadouros-frigoríficos. A mediana de MAT foi bastante próxima para A e B (1,573 log UFC.cm-1 e 1,6014 log UFC.cm-1, respectivamente),...(AU)

Investigation of Listeria monocytogenes, Salmonella enterica and Yersinia enterocolitica in pig carcasses in Southern Brazil / Pesquisa de Listeria monocytogenes, Salmonella enterica and Yersinia enterocolitica em carcaças de suínos no sul do Brasil

The intensification of pig production and advances in the sanitary control of herds profoundly changed the profile of risk attributed to pork consumption. In the actual scenario, most microorganisms related to macroscopic lesions observed in the post mortem inspection are not transmitted by food, while foodborne bacteria of importance to consumer health do not cause macroscopic lesions. In Brazil, the "Ministério da Agricultura, Pecuária e Abastecimento" requested a scientific opinion on the prioritizing of pathogens potentially transmitted by unprocessed pork. After conducting a qualitative risk assessment, only Salmonella enterica was classified as of high risk to consumers. The present study was part of the validation step of the risk assessment and aimed to investigate the frequency of S. enterica, Yersinia enterocolitica and Listeria monocytogenes and hygienic-sanitary indicators in pig carcasses of pigs rose under intensive production and slaughtered under the Federal Inspection System in three slaughterhouses located in Southern Brazil. Additionally, the antimicrobial resistance profile of the isolated pathogens was also investigated. A total of 378 carcasses were sampled by superficial sponges before the chilling step in three slaughterhouses. Samples were investigated for the presence of the three aforementioned pathogens and subjected to enumeration of Colony Formation Units (log CFU.cm-1) of total aerobic mesophiles (TAM) and Enterobacteriaceae. Salmonella strains were tested by disc diffusion test for resistance to eleven antimicrobials. There were significantly statistical differences (p<0.0001) on the median counts of both indicators between the slaughterhouses. The median of TAM was very close for Slaughterhouses A and B: 1.573 log CFU.cm-1 and 1.6014 log CFU.cm-1, respectively. While in Slaughterhouse C, a higher TAM median was detected (2.216 log CFU.cm-1). A similar profile was observed regarding to Enterobacteriaceae, and medians were calculated as follow: -0.426 log CFU.cm-1 in Slaughterhouse A; 0.2163 log CFU.cm-1 in B; and 0.633 log CFU.cm-1 in C. Regarding the pathogens investigated, L. monocytogenes was not detected and only one carcass from Slaughterhouse C was positive for Y. enterocolitica. Thus, the results suggest a very low prevalence of L. monocytogenes and Y. enterocolitica in the sampled population. A total of 65 (17.2%) carcasses were positive for S. enterica, with a difference in frequencies between slaughterhouses and slaughter days. The prevalence of Salmonella positive carcasses was higher in the Slaughterhouse C (25.4%; CI 95% 19-32%) in comparison with A (9.5%; CI 95% 9-14%) and B (18.3%; CI 95% 12-24%). There was no significantly statistical association between Enterobacteriaceae counts and Salmonella isolation on carcass surface (p=0.69). The slaughtering day, nested within the slaughterhouse, explains 31.3% of Salmonella prevalence variability. S. Typhimurium (38.1%) was the most prevalent, followed by S. Infantis (30.1%). Among the 61 Salmonella strains tested for resistance to antimicrobials, 18 (31.6%) were full-susceptible. No strain displayed resistance to azithromycin, ceftazidime, cefotaxime and meropenem. The highest resistance frequency was displayed to tetracycline (54.1%), followed by ampicillin (50.82%), nalidixic acid (42.62%) and chloramphenicol (42.62). Multi-resistance was detected in 52.54% of the, strains. In conclusion, S. enterica is more prevalent in pre-chill pig carcasses than Y. enterocolitica and L. monocytogenes and thus should be prioritized in monitoring and control programs at slaughter. Salmonella serovars varied among slaughterhouses and present significant differences in their resistance to antimicrobials. Slaughterhouses that present higher medians of TAM or Enterobacteriaceae in a monitoring period may have higher S. enterica prevalences as well. However, there is a high variation of S. enterica prevalence among slaughter days, which cannot be always related to the hygienic indicators counts observed on a given day.(AU)

A intensificação da produção de suínos e os avanços no controle sanitário dos rebanhos alterou de forma importante o perfil de risco do consumo de carne suína. No cenário atual, a maioria dos microrganismos causadores de lesões macroscópicas detectáveis na inspeção post mortem não são transmissíveis por alimentos, enquanto bactérias de importância como causadoras de doenças transmitidas por alimentos não causam lesões macroscópicas. No Brasil, o Ministério da Agricultura, Pecuária e Abastecimento solicitou uma opinião científica sobre a priorização de patógenos potencialmente transmitidos pela carne suína in natura. Após conduzir uma avaliação de risco qualitativa, apenas Salmonella enterica foi classificada como de alto risco para o consumidor. O presente estudo foi parte da etapa de validação da avaliação de risco e objetivou: investigar a frequência de S. enterica, Yersinia enterocolitica e Listeria. monocytogenes; e enumerar indicadores higiênico-sanitários em carcaças de suínos abatidos sob inspeção federal em frigoríficos dedicados ao abate de suínos sob sistema intensivo de criação no sul do Brasil. Além disso, o perfil de resistência a antimicrobianos dos patógenos isolados foi investigado. A superfície de um total de 378 carcaças foi amostrada por esponjas, na etapa de pré-resfriamento em três matadouros frigoríficos (A, B, C). As amostras foram investigadas quanto à presença dos três patógenos acima mencionados e quanto à enumeração de Unidades Formadoras de Colônia (log UFC.cm-1) de mesófilos aeróbios totais (MAT) e Enterobacteriaceae. As cepas isoladas de Salmonella foram testadas quanto à resistência a onze antimicrobianos pela técnica de disco difusão. As medianas de contagem de ambos os indicadores apresentaram diferença significativa (p<0,0001) entre matadouros-frigoríficos. A mediana de MAT foi bastante próxima para A e B (1,573 log UFC.cm-1 e 1,6014 log UFC.cm-1, respectivamente), enquanto em C uma mediana de MAT mais elevada foi determinada (2,216 log CFU.cm-1). Um perfil semelhante foi observado em relação a Enterobacteriaceae, sendo as medianas calculadas para A, B e C, respectivamente: -0,426 log CFU.cm-1; 0,2163 log UFC.cm-1; e 0,633 log UFC.cm-1. Em relação aos patógenos investigados, L. monocytogenes não foi detectada e apenas uma carcaça, do Matadouro C, foi positiva para Y. enterocolitica. Portanto, os resultados sugerem uma prevalência muito baixa desses patógenos na população amostrada. Em um total de 65 (17,2%) carcaças houve isolamento de S. enterica, com diferença nas frequências observadas entre matadouros e dias de abate. A prevalência de carcaças positivas para S. enterica foi maior no Matadouro C (25,4%; IC95% 19-32%) em comparação com A (9,5%; IC95% 9-14%) e B (18,3%; IC95% 12-24%). Não houve associação estatística entre o número de Enterobacteriaceae e o isolamento de S. enterica na superfície das carcaças (p=0,69). O dia de abate agrupado por frigorífico explica 31,3% da variação na prevalência de Salmonella. O sorovar mais frequente de S. enterica foi Typhimurium (38,1%) seguido de S. Infantis (30,1%). Entre as 61 cepas de S. enterica testadas quanto à resistência a antimicrobianos, 18 (31,6%) foram totalmente suscetíveis aos antimicrobianos testados. Nenhuma cepa apresentou resistência a azitromicina, ceftazidima, cefotaxima e meropenem. As maiores frequências de resistência foram demonstradas contra tetraciclina (54,1%), ampicilina (50,8%), ácido nalidíxico (42,62%) e cloranfenicol (42,62%). Em 52,54% das cepas foi detectada multi-resistência. Em conclusão, S. enterica é mais prevalente em carcaças suínas no pré-resfriamento do que Y. enterocolitica e L. monocytogenes. Portanto, S. enterica deve ser priorizada em programas de monitoramento e controle ao abate. Os sorovares de Salmonella variam entre matadouros e apresentam diferenças significativas na resistência a antimicrobianos. Matadouros de suínos que apresentam medianas de MAT e Enterobacteriaceae num período de monitoramento podem apresentar também prevalências mais de altas de presença de S. enterica. Entretanto, há uma alta variabilidade na frequência de S. enterica entre dias de abate, e nem sempre há relação entre essa frequência e a contagem de indicadores higiênico-sanitários determinados num determinado dia.(AU)

Survey of Salmonella spp. in beef meat for export at slaughterhouses in Brazil / Pesquisa de Salmonella spp. em carcaças bovinas durante o processamento em abatedouros-frigoríficos exportadores

The aim of the present study was to investigate the presence of Salmonella spp. in samples collected from beef meat at three points of the slaughter line (after skinning, washing and cooling) at three slaughterhouses in Brazil that export meat. Detection was based on ISO 6579:2002 and confirmed by PCR and qPCR. The isolates were typified using slide agglutination tests and PFGE. The antibiotic sensitivity profile was determined using the disk diffusion method. Contamination was detected in only one slaughterhouse. The overall frequency of contamination by Salmonella spp. was 6.7% of carcasses (6/90) and 2.6% of carcass surface samples (7/270). All isolates were confirmed by PCR and qPCR. The serological analysis and the PFGE showed a single profile: Typhimurium. The strains demonstrated 100% susceptibility to ampicillin, cefotaxime, ciprofloxacin, chloramphenicol, gentamicin and tetracycline. Positive carcasses after cooling pose a direct risk to consumers, since the meat is considered ready to be marketed after this process.(AU)

O objetivo deste trabalho foi investigar a presença de Salmonella spp. em amostras coletadas de carcaças de bovinos, em três pontos da linha de abate (após a esfola, lavagem e refrigeração) de três frigoríficos exportadores no Brasil. A detecção foi realizada pela ISO 6579:2002, e confirmada por PCR e qPCR. Os isolados foram tipificados por testes de soroaglutinação e PFGE e avaliado o perfil de sensibilidade aos antibióticos pelo método de difusão em disco. A contaminação foi detectada em apenas um abatedouro-frigorífico. As contaminações das carcaças (n=90) e amostras de carne (n=270) por Salmonella spp. foram 6 (6,7%) e 7 (2,6%), respectivamente. Todos os isolados foram confirmados por PCR e qPCR. A análise sorológica e o PFGE mostraram um único perfil: Typhimurium. As cepas apresentaram 100% de suscetibilidade à ampicilina, cefotaxima, ciprofloxacina, cloranfenicol, gentamicina e tetraciclina. As carcaças positivas após a refrigeração apresentam um risco direto para o consumidor, uma vez que, após este processo, a carne está pronta para ser comercializada.(AU)

Survey of Salmonella spp. in beef meat for export at slaughterhouses in Brazil / Pesquisa de Salmonella spp. em carcaças bovinas durante o processamento em abatedouros-frigoríficos exportadores

The aim of the present study was to investigate the presence of Salmonella spp. in samples collected from beef meat at three points of the slaughter line (after skinning, washing and cooling) at three slaughterhouses in Brazil that export meat. Detection was based on ISO 6579:2002 and confirmed by PCR and qPCR. The isolates were typified using slide agglutination tests and PFGE. The antibiotic sensitivity profile was determined using the disk diffusion method. Contamination was detected in only one slaughterhouse. The overall frequency of contamination by Salmonella spp. was 6.7% of carcasses (6/90) and 2.6% of carcass surface samples (7/270). All isolates were confirmed by PCR and qPCR. The serological analysis and the PFGE showed a single profile: Typhimurium. The strains demonstrated 100% susceptibility to ampicillin, cefotaxime, ciprofloxacin, chloramphenicol, gentamicin and tetracycline. Positive carcasses after cooling pose a direct risk to consumers, since the meat is considered ready to be marketed after this process.(AU)

O objetivo deste trabalho foi investigar a presença de Salmonella spp. em amostras coletadas de carcaças de bovinos, em três pontos da linha de abate (após a esfola, lavagem e refrigeração) de três frigoríficos exportadores no Brasil. A detecção foi realizada pela ISO 6579:2002, e confirmada por PCR e qPCR. Os isolados foram tipificados por testes de soroaglutinação e PFGE e avaliado o perfil de sensibilidade aos antibióticos pelo método de difusão em disco. A contaminação foi detectada em apenas um abatedouro-frigorífico. As contaminações das carcaças (n=90) e amostras de carne (n=270) por Salmonella spp. foram 6 (6,7%) e 7 (2,6%), respectivamente. Todos os isolados foram confirmados por PCR e qPCR. A análise sorológica e o PFGE mostraram um único perfil: Typhimurium. As cepas apresentaram 100% de suscetibilidade à ampicilina, cefotaxima, ciprofloxacina, cloranfenicol, gentamicina e tetraciclina. As carcaças positivas após a refrigeração apresentam um risco direto para o consumidor, uma vez que, após este processo, a carne está pronta para ser comercializada.(AU)

Prevalence, distribution, and molecular characterization of Salmonella recovered from swine finishing herds and a slaughter facility in Santa Catarina, Brazil.

Swine can carry Salmonella strains that may be transmitted to humans by pork products. This investigation determined the distribution and types of Salmonella in 12 swine finishing herds and a slaughter facility in Santa Catarina, Brazil. A total of 1258 samples, consisting of environmental, feed, carcass, lymph node, and fecal material were collected and submitted to bacteriological isolation of Salmonella. From 487 positive samples, 1255 isolates were recovered and confirmed to be Salmonella. The distribution of positive samples was as follows: finishing pen floors 26% (16/61); feed 29% (42/143); feces 44% (52/119); pooled feces 59% (35/59); slaughter holding pens 90% (36/40); lymph nodes 46% (220/478); pre-chilled carcass surfaces 24% (24/98); and post-chilled carcass surfaces 24% (62/260). The most prevalent serovars were Typhimurium, Panama, Senftenberg, Derby, and Mbandaka. By pulsed-field gel electrophoresis, 1071 isolates were subtyped using XbaI, and duplicate isolates were removed. From the remaining 747 isolates, 163 macrorestriction profiles (pulsotypes) were identified. Six pulsotypes were considered very frequent, occurring in 33 isolates or more. The multiple correspondence analyses showed correlations between pulsotypes from shedding pigs (feces), herd environment (pen floors), and subiliac and prescapular lymph nodes and between lairage and carcass surface samples before and after chilling. All sources of Salmonella investigated contributed to the carrier state; however, pre-slaughter contamination at lairage was the variable most strongly associated with carcass contamination. A total of 59 different antimicrobial resistance profiles were observed in 572 Salmonella isolates. From these isolates, 17% (97/572) were susceptible to all 15 antibiotics tested, 83% (475/572) were resistant to at least one, and 43% (246/572) were resistant to four or more antibiotics (multi-resistant). The AmpGenKanTet profile was the most prevalent in carcass isolates and was associated with farm origin.