Virulence factors, molecular characteristics, and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa isolated from pediatric patients in Shanghai, China.

Abstract

Background: The investigation into virulence factors, clinical and molecular characteristics, and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in pediatric populations is currently inadequate.

Purpose: This study aimed to investigate the virulence factors, clinical and molecular characteristics, and resistance mechanisms of 135 CRPA isolates in Shanghai, China.

Methods: Analysis of virulence-associated genes and multilocus sequence typing (MLST) provided epidemiological and molecular insights into the isolates. Resistance mechanisms were identified via PCR, sequencing, and qRT-PCR.

Results: The predominant resistance mechanism to carbapenems was the decreased production of outer membrane porin OprD (75.6%), accompanied by mutational inactivation of the oprD (87.4%). However, elevated production of AmpC (7.4%) and mexB overexpression (5.2%) were uncommon. Thirty-five sequence types (STs) were identified, with clonal complex 244 (CC244;59.3%) representing the majority of infections. Sixteen virulence factor genes were detected, with a significant portion of isolates (40.7%) concurrently possessing Toxin A (toxA), Elastase B (lasB), Exoenzyme S (exoS), staphylolysin (lasA), and Pilin (pilA). Almost all CC244 isolates carried toxA (100%), exoS (100%), pilA (100%), lasB (98.6%), and lasA (82.5%) while all ST2100, ST274, ST1129, ST446, and ST2069 isolates contained exoY. CC244 + isolates exhibited significantly increased antibiotic resistance, and the isolates from diseased or discharged patients showed comparatively higher resistance than others, except against gentamicin. Most patients (71.9%) received combination therapy, with 65.2% achieving clinical cure or improvement.

Conclusion: This study predominantly identified OprD-mediated carbapenem resistance in pediatric patients. The CRPA isolates were characterized by a variety of STs and a widespread distribution of virulence-associated genes. CC244 demonstrated significantly higher resistance, with potential outbreaks occurring in 2018 and 2019. These findings could aid in managing nosocomial CRPA infections and enhancing clinical practices.