Molecular And Virulence Characteristics Of Carbapenem-resistant Klebsiella Pneumoniae In Nosocomial Infection

Purpose: In recent years,with the widespread use of carbapenem antibiotics,the detection rate of carbapenem-resistant Klebsiella pneumonia(CRKP)in clinical microbiological lab has increased dramatically.It has become another important pathogen in hospital infections worldwide after Acinetobacter baumannii.Carbapenemresistant hypervirulent Klebsiella pneumonia(CR-hvKP)poses a great threat to people’s health due to its combination of high antibiotic resistance and high virulence.However,data reports on its virulence and infection characteristics in hospital-acquired infections(HAI)are still lacking.The purpose of this study is to understand the antibiotic resistance features,as well as molecular and virulence characteristics of CRKP isolated in our hospital.Methods: The CRKP that caused HAI isolated from the clinical microbiological lab of our hospital in 2018 were collected.The isolates were identified and tested for antibiotic sensitivity using the VITEK 2 Compact and MALDI-TOF MS.Modified carbapenem inactivation method and carbapenemase gene amplification were used to detected the main resistance mechanism against carbapenem of the isolates;String test,virulence gene profils,capsular antigen,and multilocus sequence typing(MLST)were used to understand the virulence characteristics and homology of the isolates.The virulence of isolates containing virulence genes were evaluate through Galleria mellonella model;The hospitalization datas were collected from medical records,and then were analysised and comparised.Results: In 2018,905 Klebsiella pneumoniae strains were isolated from the clinical microbiological lab of our hospital(905 non-repetitive isolates).Among them,125 strains of CRKP were collected from not the same location of the same patient(13.8%).By consulting case datas,we found 62 strains of CRKP that caused HAI in 125 CRKP.ST11 KPC-2 producing CRKP accounts for 79.0% of all the HAI CRKP(49/62 isolates);According to virulence genes,62 strains of CRKP were divided into virulence-containing group(41 isolates)and non-virulence groups(21 isolates),CRKP containing virulence genes has higher KPC-2 expression than CRKP without virulence genes(39/41 isolates,95.0% and 10/21 isolates,47.6%,respectively,p < 0.001),and is less sensitive to levofloxacin(resistance rate 41/41 isolates,100.0% and 11/21 isolates,52.4%,respectively,p<0.001).29 strains of CR-hvKP were found through Galleria mellonella model,the MLST,capsular serotype,enzyme production and quantity were: ST11-K64 KPC-2 producing strains 15,ST11-K64 non KPC,NDM or IMP producing strain 1,ST11-K47 KPC-2 producing strains 10,ST11-untyped KPC-2 producing strains 2,and ST2928-K54 IMP-4 producing strain 1.These CR-hvKPs were mainly derived from surgery(19/29 isolates,65.5%),followed by ICU(7/29 isolates,24.1%)and internal medicine(3/29 strains,10.4%).CR-hvKP mainly caused lung infections(11/29 cases,37.9%)and abdominal infections(9/29 cases,31%),followed by biliary tract related infections(4/29 cases,13.8%),bloodstream infections(3/29 cases,10.4%)and Surgical incision infection(2/29 cases,6.9%).Compared with the clinical characteristics of patients infected with non hypervirulenct CRKP,it was found that patients infected with CR-hvKP were more likely having prior carbapenem exposure(15/29 cases,51.7% and 1/12 cases,8.3%,respectively,p=0.013).The mortality rate of CR-hvKP infected patients(5/29 deaths,17.2%)was not significantly different from the mortality rate of non hypervirulenct CRKP infected patients(2/29 deaths,16.7%)(p=1.000).Conclusion: Among the CRKPs that cause HAI,ST11 producing KPC-2 strains is the most popular.A new type of ST2928 CR-hvKP is found.CRhv KP has a higher proportion of CRKPs that cause HAI,mainly causing lung infections and abdominal infections;There is a certain correlation between the virulence genes and the production of carbapenemase.It is found that the capsular serotypes of KPC-2 CR-hvKP produced by ST11 in our hospital are mainly K64 and K47,which are rarely reported;HAI caused by CR-hvKP is more likely to occur in hospitalized patients with a history of carbapenem antibiotic exposure before infection,there is no significant difference in infection mortality compared with HAI caused by non hypervirulenct CRKP.