Molecular epidemiological analysis of the Acinetobacter baumannii isolates from blood and sputum specimens of patients with ventilator-associated pneumonia / 中国感染与化疗杂志

ABSTRACT

Objective To investigate the molecular epidemiological characteristics of the Acinetobacter baumannii strains isolated from blood and sputum samples of patients with ventilator-associated pneumonia (VAP) in ICU.Methods The patients were analyzed in two groupsGroup A,A.baumannii was isolated from both blood and sputum,and Group B,A.baumannii was isolated only from sputum.Clinical data of the patients were collected,including the results of antimicrobial susceptibility test.Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed for the strains.Results During the study period from June 2015 to December 2105,28 nonduplicate A.baumannii strains were collected from 14 patients in group A and 28 nonduplicate strains from 28 patients in group B.The 56 A.baumannii strains were multidrug-resistant (MDR).More than 80％ of the strains were resistant to carbapenem,third-generation cephalosporins or aminoglycoside,but highly sensitive to tigecycline.No significant difference was found for the resistance rates between group A and group B.The nonduplicate A.baumannii isolates from blood and sputum samples of the same patient in group A were all homologous strains confirmed by PFGE.Six pulsotypes were identified from the 28 strains in Group A and 9 pulsotypes in Group B.Five pulsotypes were shared between the two groups.MLST analysis showed that there were 9 ST types (ST195,ST208,ST229,ST369,ST373,ST457,ST836 and two new phenotypes ST N2,ST N5) in Group A and 8 ST types (ST195,ST208,ST381 and 5 new phenotypes ST N1,ST N2,ST N3,ST N4,ST N5) strains in group B.There was no significant difference in the proportion of the main ST types between the two groups.eBURST analysis indicated that ST195,ST208,ST457,ST369,ST N1,ST N2,ST N51 belonged to CC92 prevalent strain.Conclusions The antimicrobial susceptibility profile and genotype of A.baumannii isolates from blood and sputum samples are similar.There was CC92 prevalent strain in the ward.There is no direct relation between the risk factors for bloodstream infection in VAP patients and the genotype of A.baumannii strain.It is particularly important to reinforce infection control for prevention and treatment ofA.baumannii bloodstream infections.