Background and Aim:Pseudomonas aeruginosa, an important human pathogen, is a significant cause of acute and chronic infections in patients with compromised host defenses. Outer membrane vesicles (OMVs) secreted by P. aeruginosa play an important role in virulence and host-pathogen interaction. Recently Escherichia coli OMVs were revealed as potentially genotoxic. therefore in this study, we investigated the genotoxic effects of OMVs secreted by P. aeruginosa on human blood lymphocytes. Methods:OMVs were prepared as described by Siadat et al. Human lymphocytes were treated in vitro by OMV with doses of 5,10 and 15 µg/ml. Cytokinesis-blocked lymphocytes were harvested 72 hours post culture initiation. After slide preparation and staining by Giemsa, mononuclear cells, binucleated cells without micronucleus and binucleated cells with micronucleus were scored. The data were analyzed using SPSS software and analysis of variance (ANOVA) at the level of P <0.05 Results:The data showed that OMVs were able to significantly induce Micronucleus frequency in lymphocytes. The increase in micronucleus frequency were dose-dependent. So that the micronucleus frequency were 1.06% in dose 5 and 1.7% in dose 15 as the highest dose compared to the control group(0.06%). Conclusion:Above findings indicated that OMVs are able to increase the frequency of micronucleus in human lymphocytes and induce a genotoxic response.

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