Biofilm Formation in Klebsiella pneumoniae Bacteremia Strains Was Found to be Associated with CC23 and the Presence of wcaG.

Jin-Xin Zheng,Jia-Lin Jin,Xiang Sun,Duo-Yun Li,Di Qu,Zhi-Wei Lin,Chen Chen,Yang Wu,Zhi-Jian Yu,Qi-Wen Deng,Si-Yu Yang,Wei-Ming Yao,Zhong Chen,Fo-Jun Lin

doi:10.3389/fcimb.2018.00021

Abstract

Klebsiella pneumoniae bacteremia biofilm traits and distribution characteristics have not been clarified. This study aimed to determine the prevalence and characteristics of K. pneumoniae bacteremia biofilm formation (BF) and to explore the virulence factors associated with K. pneumoniae BF. A total of 250 K. pneumoniae bacteremia isolates were collected from patients in Shenzhen and Shanghai, China. Virulence genes in their genomes were detected by PCR. The isolates were subjected to multilocus sequence typing (MLST) and clonal complex (CC) classification based on housekeeping genes. Biofilms were detected by crystal violet staining. Greater BF was observed in isolates from young adults (<40 years old) than in those from seniors (≥65 years old; P = 0.002). MLST yielded 65 different sequence types (STs), with the most represented STs being ST11, ST23, and ST65, and the main CCs were CC23 and CC65; CC23 isolates exhibited greater BF than CC65 or ST11 isolates (both P < 0.001). BF was more pronounced among magA(K1), aero+, rmpA+, rmpA2+, allS+, wcaG+, and iutA+ isolates than in isolates that were negative for these virulence factors. Multivariate regression analysis revealed only wcaG as an independent risk factor for BF (odds ratio 11.426, P < 0.001), and BF was decreased when wcaG was silenced by antisense RNA. In conclusion, BF in K. pneumoniae bacteremia isolates was found to be associated with CC23 classification and the presence of the wcaG virulence factor gene.

Highlights

Klebsiella pneumoniae has been attracting increasing attention worldwide as an infectious microorganism due to the recent rise in the number of severe K. pneumoniae infections, antibiotic resistance, and growing difficulty with establishing effective treatments
The strains were identified with a Phoenix 100 automated microbiology system (BD, Franklin Lakes, NJ, USA), and after two subcultured generations re-identified with matrix-assisted laser desorption ionization-time of flight mass spectrometry (IVD MALDI Biotyper, Bruker, Bremen, Germany)
We found that biofilm formation (BF) was greater among isolates from young adults than among isolates from seniors

Summary

Introduction

Klebsiella pneumoniae has been attracting increasing attention worldwide as an infectious microorganism due to the recent rise in the number of severe K. pneumoniae infections, antibiotic resistance, and growing difficulty with establishing effective treatments. Relative to planktonic K. pneumoniae infections, infections with K. pneumoniae strains with the ability to form biofilms are more difficult to treat (Ribeiro et al, 2015). Diago-Navarro et al (2014) found that nearly half of 40 examined carbapenemresistant K. pneumoniae bacteremia strains were able to form obvious biofilms, including 13 that exhibited high levels of biofilm formation (BF). The antibiotic resistance of mature bacterial biofilm is 10–1,000 times that of planktonic bacteria, and bacteria in biofilms can resist phagocytosis, making them very challenging to eliminate (Lebeaux et al, 2014)

Objectives

Methods

Results