Pseudomonas aeruginosa is an opportunistic pathogen infecting human population. The pathogen is becoming a serious health problem due to its ability to evade normal immune response of the host and multiple drug resistance to many antibiotics. The pathogen has 2 major virulence systems of which the type III secretion system (T3SS) is of major concern to humans. A third system, type 2 secretion system (T2SS), is common to bacteria and used to secrete exotoxin A (ExoA) responsible for human cell destruction. To help bypass the drug resistance, a strategy to block the T2SS based on a low similarity between human ATPases and the essential ATPases of the T3SS and T2SS of P. aeruginosa, was used. An in silico-optimized inhibitor of T3SS, made directly from the computer-optimized of previously published compounds and their combinatorial libraries, showed IC50 = 1.3 +/- 0.2 mu M in the T2SS ExoA secretion blocking test. The compound was non-toxic to human lung epithelial cell line A549 and could block cellular destruction of those cells in a cell infection model at 200 mu M for at least 24 h. The compound could be a lead candidate for the development of T2SS virulence blockers of Pseudomonas aeruginosa. (C) 2019 Elsevier Inc. All rights reserved.