Begando, J. | Search bioRxiv

bioRxiv2026

Pseudomonas aeruginosa Exotoxin A is not essential for corneal disease severity or bacterial survival

Pseudomonas aeruginosa produces multiple toxins and exoenzymes that contribute to its survival and ability to cause disease. As prior studies reported an important role for type III-secretion in the severity of corneal disease in P. aeruginosa keratitis, we examined if there is a requirement for the type II-secreted cytotoxin Exotoxin A (ToxA) in bacterial persistence and disease severity in infected murine corneas. Using independently generated {Delta}toxA mutants and complemented strains, we found that ToxA is expressed in vivo, but ToxA deletion did not significantly affect bacterial replication, neutrophil recruitment or disease severity. These findings contrast with an earlier study identifying a critical role for ToxA.

microbiology↗

bioRxiv2025

Alpha hemolysin polymorphisms in methicillin-resistant Staphylococcus aureus clinical isolates regulate ADAM10-dependent neutrophil IL-1 beta secretion

Staphylococcus aureus -hemolysin (Hla) is a major virulence factor that utilizes cell surface ADAM10 to oligomerize and form a functional heptameric pore. We show here that Hla from strain USA300 is required to induce IL-1{beta} secretion by neutrophils and to cause severe corneal disease in mice. We also demonstrate that in contrast to USA300 and other clonal complex 8 (CC8) methicillin resistant S. aureus (MRSA) isolated from the skin, CC5 Hla from corneas of infected patients have single nucleotide polymorphisms (SNP) that result in two amino acid substitutions, D208E (Asp-Glu) and I275T (Ile-Thr). Structural modeling predicts CC5 Hla self-assembly and altered binding to ADAM10 that is distinct from CC8 Hla. The ADAM10 inhibitor GI254023X blocked neutrophil IL-1{beta} secretion induced by Hla-expressing CC8, but not by CC5 conditioned media, indicating that these Hla polymorphisms play an important role in Hla receptor binding and neutrophil IL-1{beta} secretion, and affect corneal disease severity.

microbiology↗