Effects of chlorogenic acid on antimicrobial, antivirulence, and anti-quorum sensing of carbapenem-resistant Klebsiella pneumoniae

Abstract

The rise in infections caused by the hypervirulent carbapenem-resistant <i>Klebsiella pneumoniae</i> (hv-CRKP) is an emergent threat to public health. We assessed the effects of chlorogenic acid (CA), a natural phenolic compound, on antibacterial, antivirulence, and anti-quorum sensing (QS) of hv-CRKP. Five hv-CRKP were selected for antimicrobial susceptibility test and confirmed to carry virulence genes and carbapenem-resistant genes by polymerase chain reaction (PCR). Subsequently, a series of time-kill assay, determinations of protease activity and capsule content, biofilm-related experiment, scanning electron microscopy (SEM) and transmission electron microscope (TEM) observation, <i>G. mellonella</i> infection model, quantitative real-time PCR (qRT-PCR) of QS-related genes and biofilm formation genes, as well as AI-2 binding test were conduct to verify the effect of CA on hv-CRKP. Five CRKP strains showed varying degrees of resistance to antibacterial agents. All strains carried the <i>bla</i> _<i>KPC</i>-2 gene, primarily carrying <i>rmpA2</i>, <i>iucA</i>, and <i>peg-344</i>. CA showed no effect on CRKP growth at the 1/2 minimum inhibitory concentration (MIC), 1/4 MIC, and 1/8 MIC, CA could reduce the production of extracellular protease and capsular polysaccharides, and improve the survival rate of larvae in <i>Galleria mellonella</i> (<i>G. mellonella</i>) infection model. By means of crystal violet staining and scanning electron microscopy experiments, we observed that CA can inhibit the formation of CRKP biofilm. On the quantitative real-time PCR analysis, the expression of the <i>luxS</i>, <i>mrkA</i> and <i>wbbm</i> genes in most CRKP strains appeared downregulated because of the CA treatment. Besides, CA significantly inhibited the effect of AI-2 activity of BB170. Our study suggests that CA can be an effective antimicrobial, antivirulent compound that can target QS in hv-CRKP infections, thus providing a new therapeutic direction for treating bacterial infections.