Bacillus cereus N-acyl homoserine lactonase and penicillin acylase II against Pseudomonas aeruginosa: An In silico and In vitro investigations exploring the effects of gamma radiation on their quorum quenching activity

This study explored the quorum quenching (QQ) activities of ISM25 strain, sourced from an environmental setting, on pathogenic Pseudomonas aeruginosa isolates. The isolate ISM25 was first screened for the presence of both AiiA acyl homoserine lactonase and penicillin acylase II genes. The in silico investigation focused on examining the physiochemical properties and QQ activities in relation to both short (<C8) and long chain (>C12) homoserine lactones (HSLs) utilizing AutoDock Vina docking tests. Potential interactions between the acylase II enzyme and carbapenem antibiotics were also investigated during the in silico docking tests. Afterwards, the in vitro QQ activity of ISM25 crude protein extract was assessed against the biofilm index, AHLs molecules, and meropenem minimum inhibitory concentrations of pathogenic P. aeruginosa isolates. The findings from the in silico docking analysis were supported by the crude protein extract's capacity to hydrolyze AHLs generated by the pathogenic P. aeruginosa isolate, as well as the reference C12-HSL signal molecule. The notable decrease in biofilm indices (P < 0.05) following exposure to the crude ISM25 extract further corroborated the expression of both QQ enzymes by the ISM25 isolate and their in silico QQ activity. The crude extract from ISM25 lowered the MIC and sensitized P. aeruginosa to meropenem (P < 0.05), suggesting that ISM25 crude extract containing acylase II can be administered in conjunction with meropenem without affecting its efficacy. Finally, exposure of ISM25 to gamma radiation did not impair its QQ activity at doses below 100 Gy, however, QQ activity was nearly abolished at radiation dose ≥ 500 Gy.