Report of hypervirulent capsular serotypes of Klebsiella pneumoniae clones groups with enhanced virulence and antimicrobial resistance

Abstract

Objective To study the prevalence, virulence and antimicrobial resistance of some hypervirulent capsular serotypes of Klebsiella pneumoniae in the First Affiliated Hospital of Nanchang University. Methods Retrospective study. One hundred and seventy five Klebsiella pneumoniae clinical isolates from all specimens in our hospital from January to August 2014 were collected. All isolates were assessed for six hypervirulent capsular serotypes, sequence type, 8 virulence genes and 17 common antimicrobial resistance genes. Hypermucoviscosity phenotype (HM) of all strains was determined by string test. Virulence scores were compared between groups by Rank-sum test, while the rates of groups were compared by Chi-square test or Fisher exact test. Results Out of 175 strains of Klebsiella pneumoniae, the detection rate of hypervirulent capsular serotypes was 32.6%. The 57 isolates were divided into capsular serotype K1, K2, K5, K20, K54, and K57, accounting for 42.1%, 31.6%, 1.8%, 8.8%, 3.5%, and 12.3%, respectively. The virulence scores (number of virulence genes) P50 were 7, 5, 5, 5, 5.5, and 7, respectively. ST23 and ST29 isolates belonging to serotype K1 exhibited virulence genes up 8. The virulence scores of serotype K1 were significantly different from that of serotype non-K1 (U=48.500, P<0.01). Strains of K1-ST23 were the most common isolates, accounting for 24.6% of the overall isolates. The serotype K1 isolates exhibited lower antimicrobial resistance to 17 kinds of antimicrobials than non-K1 isolates. The positive rate of ESBLs-producing strains was 42.1%(24/57). The results of PCR showed that among the 57 strains of hypervirulent capsular serotypes of Klebsiella pneumoniae, 30 were positive for blaSHV (accounting for 52.6%), 29 positive for blaTEM (accounting for 50.9%), 27 positive for blaCTX-M (accounting for 47.4%). The sequencing results were as follows: TEM-1, a variety of CTX-M and SHV. The positive rate of HM was 61.4%(35/57). In addition, there were 15 strains positive to the PMQR genes and 3 strains positive to the 16S rRNA methylases genes, accounting for 26.3%(15/57) and 5.3%(3/57), respectively. Conclusion It is important to pay attention to high prevalence of some hypervirulent capsular serotypes of Klebsiella pneumoniae conal groups with enhanced virulence and (or) antimicrobial resistance in our hospital.(Chin J Lab Med, 2015, 38: 286-290) Key words: Klebsiella pneumoniae; Virulence; Drug Resistance, Microbial; Retrospective Studies; Sequence Analysis