Resistance genotype, capsular serotype and virulence gene of hypermucoviscous Klebsiella pneumoniae in Anhui Province

Abstract

Objective To investigate the resistance genotype, capsular serotype and virulence gene of hypermucoviscous Klebsiella pneumoniae (HMVKP). Methods A total of 698 strains of Klebsiella pneumoniae (non-repetitive strains) were collected from 35 hospitals of Anhui in September 2017. A total of 78 HMVKP strains were isolated and screened, and the phenotypes of hypermucoviscosity were identified by slime test. The minimum inhibitory concentrations (MIC) of 17 antibiotics drugs were determined by agar dilution method. The resistance related genes, serotype and virulence gene were determined by polymerase chain reaction (PCR). Molecular typing was performed with multi-locus sequence typing (MLST). The homology of major ST-sequence strains was analyzed by pulsed-field gel electrophoresis (PFGE). The carrying rate between HMVKP virulence gene rmpA positive group and the negative group were compared and analyzed. Chi-square test was used for rates comparison between two groups. Results The results showed that 66 strains among 78 strains of HMVKP were isolated from sputum samples. The HMVKP strains were sensitive to 17 antibiotics drugs but had slightly high resistance rates to chloramphenicol, ceftriaxone and ceftizoxime. Four strains produced extended-spectrum beta lactamase carried drug resistance genes including TEM (one strain), CTX-M1 (one strain) and CTX-M2 (two strains), and one strain was resistant to carbapenems, which carries the IMP resistance gene. K2 (30/78, 38.46%) and K1 (13/78, 16.67%) were the major capsular serotypes in 78 HMVKP. IroNB (71/78, 91.03%) and aerobactin (67/78, 85.90%) were the major virulence genes among the five tested virulence genes, and the highest detection rates of virulence gene were found in K2 serotype. A total of 28 ST-sequences were found in 78 strains of HMVKP, and the PFGE results indicated that the four major clones (ST23, ST65, ST86 and ST412) were divided into 16 types, and some of them had homology. In addition, statistical analysis found that the HMVKP virulence gene rmpA positive group (27/52, 51.92%) was more likely to carry the virulence gene kfu than the negative group (7/26, 26.92%). Conclusions The detection rate of drug resistance genotypes in HMVKP stains is not high. K2 and K1 are the major capsular serotypes in 78 HMVKP; iroNB and aerobactin have the highest carrying rate, and the highest detection rates of virulence genes are found in K2 serotype. Key words: Klebsiella pneumoniae; Drug resistance; Electrophoresis, gel, pulsed-field; Virulent gene; Hyper mucoviscous