Molecular and Phylogenetic Study of (Tox A) Virulence Gene of Pseudomonas - Aeruginosa Isolated from Respiratory Infections of Cats in Baghdad city

Abstract

Background Pseudomonas aeruginosa is an opportunistic  Gram-negative pathogen whose virulence  strongly associated  with exotoxin A encoded by the ToxA gene. Aim the study To detect and molecularly characterize the  (ToxA) gene  of Pseudomonas aeruginosa isolated from respiratory infections in cats in Baghdad city, and determine the phylogenetic relationship of local isolates with global strains. Methodology A total of 30 bacterial isolates previously identified as Pseudomonas aeruginosa based on cultural characteristics, biochemical identification using the VITEK-2 system with molecular detection, Genomic DNA was extracted using a commercial kit. the DNA purity and concentration were measured using a Nanodrop. polymerase chain reaction amplification of the ToxA gene. positive polymerase chain reaction products were selected for sequencing and sent to for Sanger sequencing. Results polymerase chain reaction findings revealed that 29 Pseudomonas aeruginosa isolates were positive for the ToxA gene, producing a clear amplification band at 511 bp. These results confirmed the widespread presence of this virulence gene among isolates obtained from feline respiratory infections. The phylogenetic analysis of partial ToxA gene sequences demonstrated that Iraqi isolates clustered closely with reference strains from several countries. The short branch lengths indicated a high degree of genetic similarity and limited divergence among global isolates. Additionally, some Iraqi isolates formed closely related sub-clusters, suggesting possible local adaptation or common sources of infection. Conclusions The present study confirms that the ToxA gene is highly prevalent among Pseudomonas aeruginosa isolates recovered from respiratory infections in cats and highlights its critical role in bacterial pathogenicity and disease severity. Phylogenetic analysis revealed a close genetic relationship between local Iraqi isolates and global reference strains, indicating limited genetic variation in the ToxA gene.