Prevalence of Virulence Genes Carried on Plasmids versus Chromosomes in Enterobacter cloacae Isolated from Various Clinical Samples

Document Type : New and original researches in the field of Microbiology.

Authors

1 Department of Pathological Analysis Sciences, College of Science, University of Thi-Qar, Thi-Qar, 64001, Iraq

2 Department of Pathological Analysis, College of Science, University of Thi-Qar, Thi-Qar, 64000, Iraq

Abstract

Background: Enterobacter cloacae is a common cause of Hospital-Acquired Infections. Its resistance and virulence are often associated with stable chromosomal regions or mobile genetic elements such as plasmids. Objective: This study aims to investigate the role of bacterial plasmids in contributing to clinical diseases in the Thi-Qar Governorate, Iraq. Methodology: Thirty E. cloacae isolates were collected from blood, urine, wound, and stool samples. Bacterial identification was performed using both conventional and automated methods. Antibiotic susceptibility was assessed using the disc diffusion method. PCR assays were employed to detect the presence of selected virulence genes: fepA, aac(6’)-Ib, and csgA. Results: The fepA gene was significantly more prevalent in chromosomal DNA (56.67%) compared to plasmid DNA (40.0%). The aac(6’)-Ib gene showed a prevalence of 66.67% in chromosomal DNA versus 53.33% in plasmid DNA. Additionally, the csgA gene, which encodes curli fimbriae, was detected in 60.0% of chromosomal samples and 36.67% of plasmid samples. The differences in distribution for all three genes were statistically significant (p < 0.05). Conclusion: The higher prevalence of virulence genes in chromosomal DNA suggests a stable integration that may enhance environmental adaptability and long-term resistance. These findings highlight the importance of gene location in understanding the persistence of antibiotic resistance and bacterial virulence.

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