Comparative genomics of fatal ST308/O11 Pseudomonas aeruginosa from Egypt characterizes conserved resistance architecture, integron-associated multidrug resistance modules, and blaNDM-1 resistance islands.

Pseudomonas aeruginosa is a major cause of ventilator-associated pneumonia (VAP) and is increasingly associated with extensive antimicrobial resistance, limiting therapeutic options and contributing to poor clinical outcomes. The emergence of high-risk clones that combine multidrug resistance and virulence-associated traits represents a growing public health concern.In this study, 100 clinical P. aeruginosa isolates recovered from VAP patients were screened using culture-based identification and antimicrobial susceptibility testing. Two isolates exhibiting the most extensive resistance profiles, consistent with pandrug-resistant (PDR) phenotypes, and associated with fatal clinical outcomes were selected for whole-genome sequencing using Oxford Nanopore technology.Comprehensive genomic analyses were performed to characterize antimicrobial resistance determinants, chromosomal resistance mutations, virulence-associated genes, mobile genetic elements, genomic islands, and phylogenomic relationships. Both isolates were assigned to sequence type ST308 and serogroup O11, a globally disseminated high-risk lineage. Core-genome phylogenomic analysis of 52 genomes identified 144,617 informative SNPs across 5,085 shared core genes and showed that the two Egyptian isolates differed by only 74 core-genome SNPs while clustering within the international ST308 lineage.The isolates harbored an extensive resistome including blaNDM-1, blaOXA-10, blaOXA-488, qnrVC1, rmtF, sul1, sul2, floR, and msrE. High-confidence chromosomal resistance mutations were detected in gyrA (T83I), parC (S87L), oprD (Q402HfsTer99), nalC, nalD, and pmrB, supporting resistance to fluoroquinolones, carbapenems, and polymyxins. Two complete class 1 integrons and one In0 structure, all carrying the class 1 integrase IntI1, were identified, comprising integron-associated multidrug resistance modules containing qnrVC1, aadA11, aac(6')-II, dfrB5, sul1, qacEΔ1, rmtF, blaOXA-10, and blaPAC-1. In contrast, blaNDM-1 was located within a distinct ISVsa3-associated resistance island together with ble and msrE. Genomic island analysis further demonstrated the co-localization of key resistance determinants and the exoU virulence factor within predicted genomic islands.Both isolates carried a highly conserved virulome, including exoU, exoT, type VI secretion system components, iron-acquisition systems, and biofilm-associated genes. Collectively, these findings indicate the convergence of resistance islands, integron-associated multidrug resistance modules, chromosomal resistance mechanisms, and virulence-associated determinants within a globally disseminated ST308/O11 high-risk clone associated with fatal VAP cases in Egypt.To our knowledge, this study provides the first comprehensive genomic characterization of ST308/O11 P. aeruginosa exhibiting a pandrug-resistant phenotype based on the antimicrobial panel tested and associated with fatal ventilator-associated pneumonia in Egypt. Furthermore, by integrating cohort-level screening of 100 clinical isolates with comparative whole-genome analysis, this work provides additional insight into the genomic diversity of globally disseminated high-risk lineages through the accumulation of resistance and virulence determinants.