The aim of this study was to examine the Salmonella serovars and antimicrobial resistance within an animal-based agriculture river system. The study area consisted of a 1,345 ha upper part of Pinhal catchment. A total of 384 samples were collected in four years of monitoring. Salmonella was isolated from 241 samples (62.7%), resulting in 324 isolates. The highest number of Salmonella sp. occurred in samples associated with sites with high stoking density animal unit per hectare. It was possible to demonstrate the variability of serovars in the study area: 30 different serovars were found and at least 11 per monitoring site. Thirty-three potentially related isolates were genotyped by PFGE, one major clone was observed in serovar Typhimurium, which occurred in animal feces (swine and bovine), and different sites and samplings proving the cross-contamination and persistence of this specific clone. Among 180 isolates submitted to an antimicrobial susceptibility test, 50.5% were susceptible to all 21 antimicrobials tested and 54 different profiles were found. In the current study, 49.5% of the tested isolates were resistant to at least one antimicrobial, and multi-resistance occurred in 18% of isolates. Results indicate a close interaction between animal-based agriculture, Salmonella, and antimicrobial resistance.
Os aspectos relacionados a biossegurança, limpeza e desinfecção são os principais componentes de programas de controle da infecção por Salmonella sp. em rebanhos suínos. Dessa forma, a eleição de um desinfetante eficaz deve ser a primeira etapa do protocolo de controle. A partir disso, esse trabalho teve por objetivo avaliar a atividade de seis desinfetantes comerciais (amônia quaternária, glutaraldeído, iodóforo, hipoclorito de sódio (1 e 0,1%), fenol e ácido peracético) frente a amostras de Salmonella sp. isoladas de suínos. O trabalho foi conduzido em duas etapas: na primeira, os desinfetantes foram testados frente a uma amostra padrão de Salmonella Typhimurium, na presença e ausência de matéria orgânica, sob duas diferentes temperaturas, em tempo de contato de 15 minutos. Na segunda etapa os desinfetantes foram avaliados frente a 8 amostras de Salmonella Typhimurium, com diferentes perfis de resistência a antimicrobianos, por um tempo de contato de 5 minutos. Todos os desinfetantes foram eficazes na ausência de matéria orgânica e nas duas temperaturas testadas. Entretanto, quando na presença de matéria orgânica, somente o hipoclorito de sódio (1%), fenol e o ácido peracético foram eficazes. Da mesma forma, os desinfetantes a base de hipoclorito de sódio (1%), fenol e ácido peracético foram os mais eficazes frente a todas amostras testadas após cinco minutos de contato. As observações indicam que a eficácia dos desinfetantes frente às amostras de Salmonella sp. esteve mais relacionada com as condições de utilização, principalmente quanto à presença de matéria orgânica e tempo de exposição, do que com o perfil de resistência apresentado pelas diferentes linhagens.
Salmonella control programs require the classification of positive herds according with the prevalence of infected pigs. This must be based on diagnostic methods that are reliable, accurate and cost effective. Since serological methods fulfill most of these prerequisites, many countries have adopted indirect ELISA tests to discriminate herds, based on their seroprevalence. In view of that, an in-house indirect ELISA test (ELISA-Typhimurium) previously developed proved to be able to detect sera antibodies against the most prevalent serovars of Salmonella found in Brazilian pig farms. This study aimed to assess different cut-off values of the ELISA-Typhimurium in terms of their correlation with Salmonella isolation results at the herd level. Blood and mesenteric lymph node or rectal swabs were taken from 56 slaughter and 14 grower batches from different farms. Serum was tested using the ELISA-Typhimurium at different cut-off points (OD: 6.87%-40%). A total of 55 slaughter batches had at least one Salmonellapositive sample, and the within-herd prevalence was 64.9% (SE±24.8). All 14-grower batches were negative on Salmonella isolation. The logistic regression demonstrated that at 20% OD the ELISATyphimurium test is the best model to predict Salmonella isolation frequency at the herd level. At this cut-off point, the test may be a helpful tool for discriminating Salmonella infected herds.
Salmonella control programs have been implemented in the swine industry by several countries. These programs require rapid, efficient and low cost methods in order to classify herds according to the risk of slaughter line and carcass contamination. In this sense, ELISA-LPS tests to detect antibodies against Salmonella sp. in serum or muscle fluid samples are valuable tools for the herd monitoring. In this study, the muscle fluid was evaluated as a substitute of serum in the ELISA-LPS test developed in Brazil, by comparing the results obtained with both kinds of sample collected from 671 slaughter swines. In parallel, the carrier status at slaughter was evaluated by the isolation of Salmonella sp. from mesenteric lymph nodes. The expected amplification of the infection during the finish period was confirmed by seroconversion and Salmonella isolation. The comparison of results obtained with both types of muscles tested (diaphragm muscle and pork shoulder) demonstrated a correlation R=0.859 and Kappa=0.689, considered a good agreement. The correlation coefficient between the results of serum and the muscle fluid tests was low, R=0.42 for diaphragm muscle and R=0.33 for pork shoulder. Similarly, the agreement was weak, with Kappa=0.28 and 0.22, respectively. Adjusting the ELISA cut-off to obtain a better agreement between tests, improved Kappa indexes of 0.377 for diaphragm muscle and 0.363 for the pork shoulder, in OD=0.100 and OD=0.090, respectively, were achieved. The adoption of those new cut-offs resulted in a better sensitivity, but in a lower specificity of the muscle fluid tests. The correlation between serum and meat-juice tests was also improved, but the agreement between tests remained still at low level. Therefore, the adoption of muscle fluid as samples for antibodies detection against Salmonella using the ELISA-LPS test developed in Brazil can not be indicated.
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