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

BackgroundThe investigation into virulence factors, clinical and molecular characteristics, and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in pediatric populations is currently inadequate.PurposeThis study aimed to investigate the virulence factors, clinical and molecular characteristics, and resistance mechanisms of 135 CRPA isolates in Shanghai, China.MethodsAnalysis 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.ResultsThe 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.ConclusionThis 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.