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Background <p><i>Pseudomonas aeruginosa</i> is an opportunistic pathogen and a major cause of healthcare-associated infections globally. Understanding the distribution and interaction of its virulence factors in under-investigated regions is crucial for surveillance and targeted interventions. This study aimed to comprehensively characterize the phenotypic and genotypic virulence profiles of <i>P. aeruginosa</i> clinical isolates in Bushehr, Iran. A total of 103 <i>P. aeruginosa</i> clinical isolates were collected from three hospitals in Bushehr between October 2017 and June 2019. Phenotypic assays were used to assess the production of lipase, protease, lecithinase, gelatinase, hemolysin, pigment, DNase, and biofilm. The presence of <i>exoT</i>, <i>exoA</i>, <i>exoY</i>, <i>exoS</i>, <i>exoU</i>, <i>lasB</i>, <i>aprA</i>, <i>algD</i>, <i>plcH</i>, and <i>nan1</i> genes was investigated using PCR and sequencing.</p> Results <p>Protease, lecithinase, hemolysin, and pigment production were observed in 98% of isolates, while 93.2% were gelatinase-positive, and 39.8% produced lipase. None exhibited DNase activity. Biofilm formation was detected in 98% of isolates, with 67% classified as strong biofilm producers. Core virulence genes such as <i>algD</i> (99%), <i>lasB</i> (98%), <i>aprA</i> (98%), <i>plcH</i> (96.1%), and <i>exoA</i> (93.2%) were highly prevalent. The high prevalence of algD in our isolates supports its contribution to biofilm formation. Among Type III secretion system effectors, <i>exoY</i> was found in 90.3%, <i>exoT</i> in 75.7%, <i>exoU</i> in 62.1%, and <i>exoS</i> in 38.8% of isolates. The cytotoxic virulotype (<i>exoU</i>+/<i>exoT</i>+) was identified in 43.7%, while the invasive virulotype (<i>exoS</i>+/<i>exoT</i>+/<i>exoY</i>+) was found in 32%. The high prevalence of <i>exoU+</i> genotype in Bushehr notably exceeds rates reported in other regions of Iran and globally.</p> Conclusion <p>This study highlights a high burden of virulence-associated <i>P. aeruginosa</i> strains in Bushehr, particularly those harboring the <i>exoU</i>-positive genotype, which has previously been shown to be associated with severe outcomes. These findings emphasize the importance of continuous molecular surveillance and infection control strategies and highlight the need for future studies correlating genotypic profiles with clinical outcomes.</p>

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Comprehensive characterization of virulence factors in Pseudomonas aeruginosa clinical isolates from Bushehr, Iran: High proportion of exoU-positive isolates

  • 期刊论文

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  • 发表日期：

    2026年4月24日

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  • Hamid Pournabi,
  • Saeed Tajbakhsh,
  • Mohammad Rayani,
  • Mohammad Doroudian,
  • Azam Askari,
  • Forough Yousefi

摘要

Background

Pseudomonas aeruginosa is an opportunistic pathogen and a major cause of healthcare-associated infections globally. Understanding the distribution and interaction of its virulence factors in under-investigated regions is crucial for surveillance and targeted interventions. This study aimed to comprehensively characterize the phenotypic and genotypic virulence profiles of P. aeruginosa clinical isolates in Bushehr, Iran. A total of 103 P. aeruginosa clinical isolates were collected from three hospitals in Bushehr between October 2017 and June 2019. Phenotypic assays were used to assess the production of lipase, protease, lecithinase, gelatinase, hemolysin, pigment, DNase, and biofilm. The presence of exoT, exoA, exoY, exoS, exoU, lasB, aprA, algD, plcH, and nan1 genes was investigated using PCR and sequencing.

Results

Protease, lecithinase, hemolysin, and pigment production were observed in 98% of isolates, while 93.2% were gelatinase-positive, and 39.8% produced lipase. None exhibited DNase activity. Biofilm formation was detected in 98% of isolates, with 67% classified as strong biofilm producers. Core virulence genes such as algD (99%), lasB (98%), aprA (98%), plcH (96.1%), and exoA (93.2%) were highly prevalent. The high prevalence of algD in our isolates supports its contribution to biofilm formation. Among Type III secretion system effectors, exoY was found in 90.3%, exoT in 75.7%, exoU in 62.1%, and exoS in 38.8% of isolates. The cytotoxic virulotype (exoU+/exoT+) was identified in 43.7%, while the invasive virulotype (exoS+/exoT+/exoY+) was found in 32%. The high prevalence of exoU+ genotype in Bushehr notably exceeds rates reported in other regions of Iran and globally.

Conclusion

This study highlights a high burden of virulence-associated P. aeruginosa strains in Bushehr, particularly those harboring the exoU-positive genotype, which has previously been shown to be associated with severe outcomes. These findings emphasize the importance of continuous molecular surveillance and infection control strategies and highlight the need for future studies correlating genotypic profiles with clinical outcomes.