Phenotypic and genotypic characterization of metallo-ß-lactamase producing Pseudomonas aeruginosa isolated from burn patients.

Pseudomonas aeruginosa is an opportunistic pathogen associated with many nosocomial infections. This study aimed to detect blaIMP and blaVIM genes and their common subtypes, including bla IMP-1, bla IMP-2, bla VIM-1, and bla VIM-2, among imipenem-resistant Pseudomonas aeruginosa strains. In this study, 117 P. aeruginosa strains were isolated from clinical samples of burn wound patients in Velayat hospital, Rasht, Iran, between 2018 and 2019. These isolates were tested for antimicrobial susceptibilities by disk diffusion and Metallo-ß-Lactamase (MßL) activity. The polymerase chain reaction (PCR) test was applied to detect MßLs encoding genes in MßL-producing strains. The resistance rates were as follows: Tobramycin (59%), Gentamicin (57%), Piperacillin (52%), Ciprofloxacin (51%), Ceftazidime (32%), and Amikacin (26%). Among 27 (23%) imipenem-resistant isolates, 13 (48%) produced the MßL enzyme. PCR results of imipenem-resistant isolates showed that five and four isolates contained the blaVIM (4 blaVIM1, 2 blaVIM2) and blaIMP (4 blaIMP1, 2 blaIMP2) genes, respectively. In addition some of isolates had more than one gene. In this study, 48% of imipenem-resistant strains produced the MßL enzyme. Therefore, systematic surveillance to detect MßL-producing bacteria and rational prescription and use of carbapenems could be helpful to prevent the spread of carbapenem resistance.

High incidence of type III secretion system associated virulence factors (exoenzymes) in Pseudomonas aeruginosa isolated from Iranian burn patients.

OBJECTIVE: The present study aimed to determine the prevalence of virulence factors and antimicrobial resistance profile of Pseudomonas aeruginosa strains isolated from Iranian burn patients. RESULTS: This cross-sectional study performed on 100 P. aeruginosa isolates which were recovered from burn wound specimens in 2014-2015. All presumptive isolates were identified by standard microbiologic tests. Antimicrobial susceptibility test was carried out by disk diffusion method. The presence of virulence genes was determined by PCR method. Antibiotic susceptibility results revealed that the isolates were mostly susceptible to amikacin (61%), ceftazidime (60%), and imipenem (55%). Moreover, 59% of the isolates were multi-drug resistance (MDR). The most prevalent MDR pattern was aminoglycosides-penicillins-fluoroquinolones-carbapenems (15%). The presence of exoT, exoY, exoS and exoU genes was detected in 100%, 100%, 59%, and 41% of the tested isolates, respectively. Results points out the pattern of MDR and genetic diversity of type III secretion system among P. aeruginosa strains isolated from the burn population. Overall, the association of MDR and the presence of the specific virulence genes can be a predictive marker for the persistence of these isolates in the hospitals and subsequently a worse clinical condition for the affected patients.