Detection of Exotoxins and Antimicrobial Susceptibility Pattern in Clinical Pseudomonas aeruginosa Isolates

Background: Pseudomonas aeruginosa is a common opportunistic pathogen that causes nosocomial infection in immunocompromised patients. Among different virulence factors, the type III secretion system (TTSS) is an important agent in virulence and development of antimicrobial resistance in P. aeruginosa. Previous studies have shown that production of TTSS proteins was correlated with increasing virulence and resistance to several antibiotics. In this study, the exotoxins genes (exoU and exoS) and pattern of antimicrobial susceptibility in clinical P. aeruginosa isolates were determined. Methods: A total of ۱۷۵ P. aeruginosa isolates were collected from patients hospitalized in Shahrekord and Chamran educational hospitals of Isfahan, Iran (during April to December ۲۰۱۵). Antimicrobial susceptibility test was performed by disk diffusion test. The presence of exotoxin genes was detected using multiplex polymerase chain reaction (PCR) of exoU and exoS genes. Results: The antibiotic resistance rate was higher than ۷۰% to many antibiotics. The highest rates of resistance (۱۵۵ and ۱۴۸) were related to Levofloxacin (۸۸.۶%) and Meropenem (۸۴.۶%), respectively. The exoU gene was found in ۷۵ (۴۲.۹%) isolates and ۱۳۶ (۷۷.۷%) isolates carried the exoS. In addition, ۳۶ (۲۰.۶%) of the isolates carried both genes. A statistical significance was observed between the presence of exoU gene and resistance to piperacillin (P = ۰.۰۱). Conclusions: The result of this study showed a high resistance rate to the most antibiotic classes and a specific relationship between the virulence genotype and antimicrobial resistance especially more virulent genotype of exoU+ . In order to prevent the spread of more virulent strains in health care facilities, molecular methods alongside antimicrobial susceptibility tests are suggested.