Analysis Of Risk Factors And Detection Of Molecular Markers Of Carbapenem-resistant And Cephalosporin-susceptible Pseudomonas Aeruginosa

PurposeThe aim of this study was to investigate the antibiotic resistance of carbapenem-resistant and cephalosporin-susceptible Pseudomonas aeruginosa(Carb-R/Ceph-S P.aeruginosa)strains,and to assess the molecular markers,risk factors and clinical impact of Carb-R/Ceph-S P.aeruginosa bacteremia on mortality so as to contribute to the development of a better approach reducing Carb-R/Ceph-S P.aeruginosa bacteremia.Methods1.Clinical analysis of Carb-R/Ceph-S P.aeruginosa: We conducted a retrospective case-case-control study of risk factors of hospitalized patients with Carb-R/Ceph-S P.aeruginosa bacteremia from the First Affilitated Hospital of Chongqing Medical University from January 2011 to December2017.According to the antibiotics susceptibility,case I was defined as patients with Carb-R/Ceph-S P.aeruginosa bacteremia,case II withcarbapenem-susceptible and cephalosporin-susceptible P.aeruginosa(Carb-S/Ceph-S P.aeruginosa)bacteremia and controls with no bacteremia were compared.Analysis of the clinical outcomes of patients with P.aeruginosa bacteremia and the potential predictors for mortality.2.Dectection of molecular markers of Carb-R/Ceph-S P.aeruginosa:extended spectrum β-lactamases(ESBLs)-encoding genes and carbapenemase-encoding genes were detected by PCR method;Using RT-PCR method to detect the expression of AmpC,OprD,and efflux pump systems.Results1.Clinical characteristics and risk factors of Carb-R/Ceph-S P.aeruginosa bacteremia:1.1 According to the antibiotics susceptibility,We collected 63 patients with Carb-R/Ceph-S P.aeruginosa bacteremia from 203 patients with P.aeruginosa bacteremia during the study period,most patients came from surgical ward(57.1%).Hepatobiliary disease,hematologic malignancy,and gastrointestinal disease were the most frequent underlying diseases.1.2 Risk factors analysis indicated that 30-day readmission,central venous catheters,and exposure to carbapenems were unique independent predictors for acquiring Carb-R/Ceph-S P.aeruginosa bacteremia.Additionally,hematologic malignancy was a peculiar predictor for Carb-S/Ceph-S P.aeruginosa bacteremia.Notably,total parenteral nutritionwas the only common factor of both Carb-R/Ceph-S and Carb-S/Ceph-S groups compared to controls.1.3 The overall 30-day mortality rate of Carb-R/Ceph-S P.aeruginosa bacteremia was 27.0 %,which was significant higher than case II groups(12.7 %,8/63).The analysis of the clinical outcomes showed that ICU admission and septic shock were the independent predictors for mortality.2.The results of molecular markers of Carb-R/Ceph-S P.aeruginosa:none of these isolates possessed carbapenemase or ESBLs-encoding genes by using PCR.RT-PCR analysis showed that 4 Carb-R/Ceph-S P.aeruginosa isolates decreased expression of OprD,overexpression of MexB was observed in 3 isolates,and overexpression of MexD was observed in 2 isolates.In constrast,overexpression of AmpC,MexF,or MexY was rarely found.Conclusions30-day readmission,central venous catheters,total parenteral nutrition,and exposure to carbapenems were unique independent predictors for acquiring Carb-R/Ceph-S P.aeruginosa bacteremia.The results of detection showed that decreased expression of OprD,and overexpression of MexB 、 MexD of Carb-R/Ceph-S P.aeruginosa.Exposure to carbapenems could be associated with the phenotype of Carb-R/Ceph-S P.aeruginosa.