Antimicrobial resistance, biofilm formation and virulence reveal Actinobacillus pleuropneumoniae strains' pathogenicity complexity.

Porcine pleuropneumonia is an important cause of lowered productivity and economic loss in the pig industry worldwide, associated primarily with Actinobacillus pleuropneumoniae infection. Its colonization and persistence within the upper respiratory tract of affected pigs depends upon interactions between a number of genetically controlled virulence factors, such as pore-forming repeats-in-toxin exoproteins, biofilm formation, and antimicrobial resistance. This study investigated correlations between biofilm-forming capacity, antimicrobial resistance, and virulence of A. pleuropneumoniae obtained from clinical outbreaks of disease, using a Galleria mellonella alternative infection model. Results suggest that virulence is diverse amongst the 21 strains of A. pleuropneumoniae examined and biofilm formation correlated with genetic control of antimicrobial resistance.

Physiological alterations in Bradybaena similaris (Stylommatophora: Bradybaenidae) induced by the entomopathogenic nematode Heterorhabditis indica (Rhabditida: Heterorhabditidae) strain LPP1.

Heterorhabditis is a nematode found in the soil that is used as an important biological control agent against various organisms. However, few studies have been performed of its use against snails and the present study is the first to investigate the effect of experimental exposure of Bradybaena similaris to Heterorhabditis indica LPP1. Two groups of 16 snails were formed: the control group (not exposed) and the treatment, which was exposed for three weeks to infective juveniles (J3) of H. indica LPP1. The entire experiment was conducted in duplicate, using a total of 64 snails. After this period, the snails were dissected to collect the hemolymph to evaluate the possible physiological alterations, namely total proteins, uric acid and hemolymph urea, as well as the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as a result of the infection. The terrariums were analyzed on alternate days throughout the experiment to count the dead snails. Intense proteolysis was observed in the infected snails. An increase in the level of uric acid and reduction of the hemolymph urea content indicated that the infection by H. indica results in the inversion of the excretion pattern of the host snail. Variations in the aminotransferase activities were also observed, with the infected group presenting significantly higher values (p<0.05) than the control group for both ALT and AST. The exposure to H. indica LPP1 caused 55% mortality, with the highest rate observed in the first week after exposure (30%). These results suggest that the use of H. indica LPP1 is a feasible alternative for the biological control of B. similaris.