Outer Membrane Vesicles Associated With the Delivery of Amoxicillin Resistance in Glaesserella parasuis

Glasser's disease is caused by Glaesserella parasuis, a common bacterium in the upper respiratory tract of pigs. Antibiotics are widely used to control this disease. A G. parasuis isolate with amoxicillin (AMX) resistance was identified in our previous study. Outer membrane vesicles (OMVs) are naturally released by G. parasuis and contain many compounds. To reveal the underlying mechanisms associated with AMX resistance delivery, OMVs from G. parasuis were successfully isolated and identified by transmission electron microscopy. In particular, we found that beta-lactamase existed in OMVs using label-free analysis, and further verified that OMVs carry beta-lactamase by Western blotting. The minimal inhibitory concentration and growth rate were determined to evaluate the beta-lactamase activity in G. parasuis OMVs. Moreover, the effect of different concentrations of OMVs from aHPS7 on the growth rate of AMX sensitive strains was examined. Our results further confirmed that OMVs isolated from aHPS7 contain beta-lactamase, which can prevent AMX-susceptible strains from killing by hydrolyzing AMX. Our results first showed that OMVs of G. parasuis play an important role in the spread of antibiotic resistance, which seriously hampered the prevention of this disease by the delivery of OMVs in different strains.