Molecular Characteristics And Virulence Compared Of Ccarbapenem-resistant Klebsiella Pneumoniae And Hypervirulent Klebsiella Pneumoniae

Klebsiella pneumonia is considered as a common opportunistic pathogen with abilities to adapt to environments and to produce resistance to antibiotics.It is wildly found in hospitals,especial in intensive care units,and responsible for nosocomial infections.In recent years,a distinctive syndrome of community-acquired invasive infections has emerged in humans,primarily in the form of pyogenic liver abscesses.Hypervirulent Klebsiella pneumonia strains have mucoid phenotypes and have higher virulence than common Klebsiella pneumonia.The infections can cause liver abscess,meningitis,necrotizing fasciitis,endophthalmitis and severe pneumonia,which characterized by fast progress,poor prognosis and life-threatening.Furthermore,the detectable rate of Carbapenem-resistant Klebsiella pneumonia(CRKP)has been rising gradually by Shanghai Antimicrobial Resistance Surveillance System.For a long time,CRKP has been carrying few virulence factors and not been considered as hypervirulent strains.The research is to investigate the molecular epidemiology of CRKP and HVKP,to determine the main epidemic strains and detect the carbepenemases genes,to compare bacterial virulence genes.We will also compare the infection characters and virulence among CRKP,HVKP,and CR-HVKP by methods of murine bacteremia models.This will be helpful to nosocomial infection control and treat the infection and investigate the relationship between virulence and resistance of KP.Part One The molecular epidemiology study and virulence of Carbapenem-resistant klebsiella pneumoniae and Hypervirulent Klebsiella Pneumoniae.To investigate the epidemiological characters and virulence of carbapenem-resistant klebsiella pneumoniae(CRKP)and hypervirulent klebsiella pneumoniae(HVKP).Identification and antibiotic sensitivity test were be used in 84 CRKP and 67 HVKP isolates which are isolated from clinic in 2015.We detected the carbepenemases genes,virulence genes and Capsular type of the isolates by methods of PCR.The isolates were be genetic typed by using multilocus sequence typing(MLST).The results demonstrated that CRKP isolates showed high antibiotic resistance and most of them were isolated from intensive care unit(ICU).Among the CRKP isolates,90.5% were identified as KPC positive,and ST11(84%)were predominant sequence types.HVKP isolates were sensitive to common antibiotics and most of them were isolated from departments of surgery,outpatient and emergency.Among the HVKP isolates,ST65(19%),ST23(12%)and ST86(12%)were predominant sequence types.The major Capsular types of HVKP isolates were serotype K1(19%)and K2(45%).All the The Capsular types of ST23 isolates were K1,meanwhile ST65 and ST86 isolates were K2.The carrier rate of virulence genes including magA,allS,iutA,rmpA,kfu and Ytbs,were significantly higher in HVKP isolates compared with CRKP(p<0.001).The results indicated that CRKP were considered as the most frequent pathogen responsible for nosocomial infections,the major epidemic isolate was KPC-ST11.Most of HVKP isolates were lead to community acquired infections and showed more sensitive to common antibiotics.It was suggested that HVKP isolates are more virulent than CRKP isolates as may more virulence genes be carried in them.Part Two Comparation of Infection Characters and Virulence between Carbapenem-resistant Pneumoniae and Hypervirulent Klebsiella Pneumoniae in Murine Bacteremia ModelsTo realize and compare infection characters and virulence between Carbapenem-resistant Pneumoniae(CRKP)and Hypervirulent Klebsiella Pneumoniae(HVKP),several strains contain 10 in group CRKP,10 in group HVKP and 8 in group CR-HVKP were be used to set murine bacteremia models.We investigated differences between the three groups by survival analysis,bacterial CFU counts in blood,liver and kidney of mice,as well as gran stain and pathological sections.The results indicated that the survival rate of mice infected with HVKP was significantly higher compared with CRKP or CR-HVKP(p <0.001)and the bacterial CFU in blood,liver and kidney of mice 24 h after infection by HVKP was significantly more than CRKP and CR-HVKP(p <0.001).More gram-negative bacilli were observed in the liver and kidney of HVKP infected mice compared with CRKP or CR-HVKP.In the liver of HVKP infected mice,several infected foci were be found in the liver of HVKP infected mice by histological examination which were not significant in CRKP or CR-HVKP.The murine bacteria models experiments showed that HVKP strains exhibited far more virulence in vivo compared with CRKP and CR-HVKP strains.Meanwhile,that there was no difference of statistics between CRKP and CR-HVKP.In conclusion,most predominant sequence types of the 84 CRKP were ST11 producing KPC which has widely spreaded in the world.This kind of KP were resistant to multiple drugs and most of them were isolated from intensive care units.The types of the 67 HVKP were more spread and we found higher rate of virulence genes in them.Among HVKP,CRKP and CR-HVKP,we found HVKP was the most virulent in vivo.We also found the virulence of CR-HVKP was same to CRKP,much lower than HVKP,though the isolates of CR-HVKP had high mucoid phenotypes.The results provided basis for further research about the relationship between resistance and virulence of KP.