Green tea, a water extract of non-fermented leaves of Camellia sinensis L., is one of the nonalcoholic beverages in China. It is becoming increasingly popular worldwide, because of its refreshing, mild stimulant and medicinal properties. Here we examined the quorum sensing inhibitory potentials of tea polyphenols (TP) as antivirulence compounds both in vitro and in vivo. Biosensor assay data suggested minimum inhibitory concentrations (MICs) of TP against selected pathogens were 6.25 ~ 12.5 mg/mL. At sub-MIC, TP can specifically inhibit the production of violacein in Chromobacterium violaceum 12472 with almost 98% reduction at 3.125 mg/mL without affecting its growth rate. Moreover, TP exhibited inhibitory effects on virulence phenotypes regulated by QS in Pseudomonas aeruginosa. The total proteolytic activity, elastase, swarming motility and biofilm formation were reduced in a concentration-dependent manner. In vivo, TP treatment resulted in the reduction of P. aeruginosa pathogenicity in Caenorhabditis elegans. When its concentration was 3.125 mg/mL, the survival rate reached 63.3%. In the excision wound infection model, the wound contraction percentage in treatment groups was relatively increased and the colony-forming units (CFU) in the wound area were significantly decreased. These results suggested that TP could be developed as a novel non-antibiotic QS inhibitor without killing the bacteria but as an antivirulence compound to control bacterial infection.
Co-occurrence of hypervirulence and KPC-2 carbapenem resistant phenotypes in a highly-transmissible ST11 clone of
Klebsiella pneumoniae
has elicited deep concerns from public health stand point. To address this puzzle, we conducted a large-scale epidemiological, clinical and genomic study of
K. pneumonia
ST11 clones with both hypervirulence and carbapenem resistance in two tertiary hospitals in Zhejiang province. Most of the patients (15/23) were diagnosed with exclusively carbapenem-resistant
K
.
pneumoniae
(CRKP) infections. Ten death cases were reported, some of which are due to the failure of antibiotic therapies. As a result, we identified one new rare sequence types (ST449) to KPC-2-producing CRKP, in addition to the dominant ST11. These clinical isolates of
K. pneumoniae
are multi-drug resistant and possess a number of virulence factors. Experimental infections of wax moth larvae revealed the presence of hypervirulence at varied level, suggesting the complexity in bacterial virulence factors. However, plasmid curing assays further suggested that the
rmpA2
-virulence plasmid is associated with, but not sufficient for neither phenotypic hypermucoviscosity nor virulence of
K
.
pneumoniae
. Intriguingly, all the
rmpA2
genes were found to be inactive due to genetic deletion. In total, we reported 21 complete plasmid sequences comprising 13
rmpA2
-positive virulence plasmids and 8
bla
KPC-2
-harboring resistance plasmids. In addition to the prevalent pLVKP-like virulence plasmid variants (~178kb), we found an unexpected diversity among KPC-2-producing plasmids whose dominant form is IncFII-IncR type (~120kb), rather than the previously anticipated version of ~170kb. These findings provide an updated snapshot of convergence of hypervirulence and carbapenem resistance in ST11
K. pneumoniae.
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