Pasteurella multocida causes atrophic rhinitis in swine and fowl cholera in birds, and is a secondary agent in respiratory syndromes. Pathogenesis and virulence factors involved are still poorly understood. The aim of this study was to detect 22 virulence-associated genes by PCR, including capsular serogroups A, B and D genes and to evaluate the antimicrobial susceptibility of P. multocida strains from poultry and swine. ompH, oma87, plpB, psl, exbD-tonB, fur, hgbA, nanB, sodA, sodC, ptfA were detected in more than 90% of the strains of both hosts. 91% and 92% of avian and swine strains, respectively, were classified in serogroup A. toxA and hsf-1 showed a significant association to serogroup D; pmHAS and pfhA to serogroup A. Gentamicin and amoxicillin were the most effective drugs with susceptibility higher than 97%; however, 76.79% of poultry strains and 85% of swine strains were resistant to sulphonamides. Furthermore, 19.64% and 36.58% of avian and swine strains, respectively, were multi-resistant. Virulence genes studied were not specific to a host and may be the result of horizontal transmission throughout evolution. High multidrug resistance demonstrates the need for responsible use of antimicrobials in animals intended for human consumption, in addition to antimicrobial susceptibility testing to P. multocida.

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Feed supplied to pigs is considered an important vehicle for Salmonella enterica subsp. enterica introduction on farm. Salmonella can be able to form biofilm on several abiotic surfaces, which may contribute to environmental persistence. This study aimed to evaluate the biofilm formation capacity in Salmonella strains isolated from four Brazilian feed mills. The biofilm formation was assessed in 54 Salmonella isolates belonging to different serovars by phenotypic assays: i. expression of curli fimbriae and cellulose in Luria-Bertani agar supplemented with Congo red, Coomassie brilliant blue and calcofluor; ii. adhesion on 96-well polystyrene microtiter plates. The results showed that all isolates presented the rdar morphotype (read, dry and rough colonies) on agar incubated at 28° C. From the total of isolates displaying rdar-morphotype, 14.8% (8/54) showed to be weakly adherent on polystyrene microtiter plates, and were thus considered presumptively biofilm producers. These strains were originated from ingredients and equipment samples, and were distributed among the following serovars: Montevideo (n=2), Senftenberg (n=2), Tennessee (n=1), Orion (n=1), Morehead (n=1), and S. enterica O: 16 (n=1). In this sense, biofilm formation might have played a role in Salmonella colonization of equipment in feed mills, and should be further investigated.