Drug resistance characteristics of 350 strains of carbapenem-resistant Klebsiella pneumoniae based on combined drug susceptibility testing for ceftazidime-avibactam

OBJECTIVE To understand the drug resistance rates of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains and explore the combined drug susceptibility testing for the CRKP strains. METHODS Totally 350 strains of CRKP that were isolated from clinical specimens in Linyi People's Hospital were collected as the subjects. The characteristics of drug resistance of the strains were observed by means of full-automatic microbial analyzer, modified carbapenem inactivation method (mCIM), ethylene diamine tetraacetic acid (EDTA)-carbapenem inactivation method (eCIM), immunochromatography and polymerase chain reaction (PCR). The combined antimicrobial susceptibility testing for the NDM-producing strains based on ceftazidime-avibactam was performed by conventional disk diffusion method, disk enhancement method and microbroth dilution chessboard method. RESULTS The drug resistance rates of CRKP strains to tigecycline and polymyxin were 0.57% and 2.44%, respectively; the drug resistance rate of the 285 CRKP strains producing bla_KPC drug resistance genes to ceftazidime-avibactam was 0.35%, while the 12 strains producing bla_OXA gene were completely sensitive to it, and the 53 strains producing bla_NDM gene were totally resistant to it. The drug resistance rates of the strains producing bla_NDM gene to amikacin, aztreonam, ciprofloxacin, gentamicin and levofloxacin were lower than those of the strains producing bla_KPC drug resistance gene(P＜0.05). The result of the joint drug susceptibility testing showed that ceftazidime-avibactam combined with aztreonam had synergistic effect, and its combination with fosfomycin has the synergistic effect on only 1 strain; it did not have synergistic effect when it was combined with levofloxacin, tigecycline, amikacin or meropenem. CONCLUSIONS There are limited antibiotics for treatment of CRKP infections, ceftazidime-avibactam can be chosen for treatment of the infections with serine hydrolase-producing strains, ceftazidime-avibactam combined with aztreonam is recommended for treatment of the infections with metalloenzyme-producing strains. It is necessary to carry out the precise treatment and adjust the medication based on the result of clinical laboratory test.