Detection of KPC carbapenem by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry / 中华微生物学和免疫学杂志

ABSTRACT

Objective To compare the capability of ertapenem-hydrolyzing in various concentrations in KPC-producing Enterobacteriaceae by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry( MALDI-TOF MS).Methods Nineteen KPC-producing Enterobacteriaceae including ten Proteus mirabilis isolates,three Enterobacter aerogenes isolates,two Serratia marcescens isolates,two Citrobacter freundii isolates,one Klebsiella pneumoniae isolate and one Enterobacter cloacae isolate were isolated from 2nd Affiliated Hospital of Zhejiang University; Seven KPC-producing Morganella morganii were isolated from Hangzhou Traditional Chinese Medicine Hospital; Eleven Escherichia coli transconjugants produced the KPC-2 carbapenemase gene were conjugated from seven M.morganii and four P.mirabilis.MALDI-TOF MS was used to detect the ertapenem-hydrolyzing capability in different KPC-producing Enterobacteriaceae.Results When the concentration of ertapenem was 0.1 g/L,ertapenem can be hydrolyzed by KPC carbapenem within 1.5 h and the sensitivity was 100％,all the three peaks produced by ertapenem disappeared; when the concentration of ertapenem raised to 0.3 g/L,the sensitivity fell to 70.3％ (26/37) within 1.5 h,followed with 89.2％ ( 33/37 ) within 2.5 h and 94.6％ (35/37) within 3.5 h; when the concentration of ertapenem raised to 0.5 g/L,the sensitivity was 48.6％ (18/37) within 1.5 h,83.8％ (31/37) within 2.5 h,94.6％ (35/37 ) within 3.5 h.Two independent samples tests indicated that 0.1 g/L of ertapenem group has significant difference with 0.3 g/L and 0.5 g/L group,while there was no significant difference between 0.3 g/L group and 0.5 g/L group; As for the bacteria groups,there are no significant differences between the bacteria groups except the group of P.mirabilis and E.coli.Conclusion MALDI-TOF MS was easy to operate; it can rapidly detect KPC-producing Enterobacteriaceae with high sensitivity and a low false positive rate.0.1 g/L of ertapenem was recommended to detect KPC carbapenem rather than 0.3 g/L and 0.5 g/L; The detection time is short and can be widely applied clinically.