Infection and Drug Resistance (Jul 2022)
The Anti-Virulence Effect of Sub-Minimal Inhibitory Concentrations of Levofloxacin on Hypervirulent Klebsiella pneumoniae
Abstract
Xuejiao Ma,1,* Li Zhang,1,* Chengcheng Yue,1 YanYan Liu,2,3 Jiabin Li1– 4 1Department of Infectious Diseases, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China; 2Institute of Bacterium Resistance, Anhui Medical University, Hefei, People’s Republic of China; 3Anhui Center for Surveillance of Bacterial Resistance, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China; 4Department of Infectious Disease, Chaohu Hospital of Anhui Medical University, Hefei, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jiabin Li, Department of Infectious Diseases, The First Affiliated Hospital of Anhui Medical University, Jixi Road no. 218, Hefei, 230022, People’s Republic of China, Tel/Fax +86-551-62922713, Email [email protected] YanYan Liu, Anhui Center for Surveillance of Bacterial Resistance, Jixi Road no. 218, Hefei, 230022, People’s Republic of China, Tel/Fax +86-551-62922713, Email [email protected]: Hypervirulent Klebsiella pneumoniae (hvKp) is best described as a virulent pathogen and generally associated with the hypermucoviscosity phenotype. Increased capsule and aerobactin production are established important hvKp-specific virulence factors. Although hvKp strains have been relatively susceptible to antimicrobials, given the high morbidity and mortality, there is a critical need for alternative strategies for the treatment of hvKp infections. Thus, the anti-virulence therapy has been targeted for the hvKp development of therapeutics.Materials and Methods: Four hvKp isolates with hypermucoviscous phenotype were used in our experiments. Mucoviscosity of the capsule can be assessed by low-speed centrifugation of cultures. CPS amount was determined by glucuronic acid content. The capsule thickness was measured under microscope after ink staining. The transcriptions of gene were measured by quantitative real-time PCR (qRT-PCR). The effect of levofloxacin on the resistance of K. pneumoniae to phagocytosis by macrophages and mouse lethality assay was observed.Results: Our data revealed that sub-Minimal Inhibitory Concentrations (sub-MIC) of LVX reduce mucoviscosity and CPS production of hvKp. Microscopic observations demonstrated that the capsule of hvkp bacteria became thinned after treatment with LVX. qRT-PCR showed decreased transcript levels of rmpA, wzi, magA, iroN and icuA genes. Down-regulation of these virulence genes occurred leading to increased susceptibility to phagocytosis by macrophages. Mouse lethality assay revealed that the wild strain had the LD50 of 103 CFU, while the sub-MIC LVX-treated bacteria had the LD50 of 105 CFU.Conclusion: Our data suggested that LVX may serve as a potential anti-virulence agent for refractory infection by hvKp.Keywords: hypervirulent Klebsiella pneumoniae, hypermucoviscous, capsular polysaccharide, levofloxacin, anti-mucoviscous, anti-virulence agent
