RESUMO.-[Detecção de genes associados à virulência em cepas de Salmonella Enteritidis isoladas de frangos na região sul do Brasil.] Salmonella spp. estão entre os principais agentes causadores de doenças transmitidas por alimentos, e o sorovar Salmonella Enteritidis é o mais frequentemente isolado no mundo. A virulência de Salmonella spp. e a sua interação com o hospedeiro são processos complexos que envolvem fatores de virulência para sobreviver às defesas do hospedeiro. O objetivo deste estudo foi detectar genes de virulência em cepas de S. Enteritidis isoladas a partir de fontes avícolas no sul do Brasil. Ensaios de PCR foram desenvolvidos para a detecção de nove genes (lpfA, agfA, sefA, invA, hilA, avrA, sopE, sivH are considered the main agents of foodborne disease and Salmonella Enteritidis is one of the most frequently isolated serovars worldwide. The virulence of Salmonella spp. and their interaction with the host are complex processes involving virulence factors to overcome host defenses. The purpose of this study was to detect virulence genes in S. Enteritidis isolates from poultry in the South of Brazil. PCR-based assays were developed in order to detect nine genes (lpfA, agfA, sefA, invA, hilA, avrA, sopE, sivH and spvC) associated with the virulence in eighty-four isolates of S. Enteritidis isolated from poultry. The invA, hilA, sivH, sefA and avrA genes were present in 100% of the isolates; lpfA and sopE were present in 99%; agfA was present in 96%; and the spvC gene was present in 92%. It was possible to characterize the isolates with four different genetic profiles (P1, P2, P3 and P4), as it follows: P1, positive for all genes; P2, negative only for spvC; P3, negative for agfA; and P4, negative for lpfA, spvC and sopE. The most prevalent profile was P1, which was present in 88% of the isolates. Although all isolates belong to the same serovar, it was possible to observe variations in the presence of these virulence-associated genes between different isolates. The characterization of the mechanisms of virulence circulating in the population of Salmonella Enteritidis is important for a better understanding of its biology and pathogenicity. The frequency of these genes and the establishment of genetic profiles can be used to determine patterns of virulence. These patterns, associated with in vivo studies, may help develop tools to predict the ability of virulence of different strains.

Eighty Salmonella Enteritidis strains isolated from broiler carcasses between May 1995 and April 1996 in the State of Rio Grande do Sul, Brazil, were tested for antibiotic susceptibility using the disk diffusion method. Resistance to colistin, novobiocin, erythromycin and tetracycline was observed in 100% of the isolates. The strains showed intermediate resistance at different levels to kanamycin (1.25%), enrofloxacin (3.75%), neomycin (3.75%), fosfomycin (20%), sulphonamides (86.25%) and nitrofurantoin (90%). Resistance to ciprofloxacin, norfloxacin, gentamicin, polymyxin B, sulphametrim and sulphazotrim was not found. Since resistance to antibiotics especially those introduced in the last decades, was detected, it is recommended that their use must be based on the results of resistance tests or minimum inhibitory concentration tests.

Salmonella spp. remain among the most important agents of foodborne diseases worldwide. The importance of Salmonella spp. in public health is linked to their wide range of antimicrobial resistance and to their pathogenicity and virulence in both human and animal hosts. The aim of this study was to determine the antimicrobial resistance patterns for Salmonella serotypes isolated from poultry sources in Brazil and to detect virulence-associated genes and verify their association with specific serotypes. A total of 163 strains of Salmonella enterica isolated from poultry sources in Southern Brazil were selected, and each belonged to one of 11 different serotypes. They were tested against ten antibiotics and examined for the presence of 26 virulence-associated genes by PCR. S. Typhimurium, S. Bredeney, S. Schwarzengrund and S. Tennessee showed the highest overall resistance rates. Approximately 18% of Salmonella strains were classified as multidrug-resistant strains. Our results indicate associations between antimicrobial resistance and specific serotypes. Most of the investigated genes presented a high frequency and a regular distribution, regardless of the serotype. Eight genes are positively or negatively associated with at least one serotype. The observed associations between antimicrobial resistance and specific serotypes are useful in developing specific control and treatment measures for each serotype. Despite the virulence genes being evenly distributed among the serotypes, some of these genes are associated with specific serotypes, and sefA, sopEand lpfA were selected as possible markers of Salmonella serotypes.

A preocupação com a segurança alimentar tem mudado a forma como os consumidores vêem os produtos

1. Although the poultry industry uses state-of-the-art equipment and up-to-date services, in Brazil it generally makes decisions involving all its production variables based on purely subjective criteria. This paper reports the use of artificial neural networks to estimate performance in production birds belonging to a South Brazilian poultry farm. 2. Recorded data from 22 broiler production breeder flocks were obtained, from April, 1998 to December, 1999, which corresponded to 689 data lines of weekly recordings. 3. These data were processed by artificial neural networks using the software NeuroShell 2 version 4.0 (Ward Systems Group). The artificial neural network models generated were compared and selected based on their largest determination coefficient (R2), lowest Mean Squared Error (MSE), as well as on a uniform scatter in the residual plots. The authors conclude that it is possible to explain the performance variables of production birds, with the use of artificial neural networks. 4. The method allows the decisions made by the technical staff to be based on objective, scientific criteria, allows simulations of the consequences related to these decisions, and reports the contribution of each variable to the variables under study.