Evaluation of citric acid and clove oil as safe anti-virulence and resistance-modifying agents against problematic klebsiella clinical isolates in Egypt

Abstract

Klebsiella species are regarded as terrifying pathogens that threaten different healthcare systems. These pathogens possess a variety of virulence factors which markedly account for their pathogenicity. Three virulence factors (capsule formation, hypermucoviscosity and biofilm formation) were screened, phenotypically and genotypically, among selected Egyptian Klebsiella clinical isolates. Two safe edible agents, clove oil and citric acid, were tested for their effect on bacterial capsules using the Anthony capsular staining method and the transmission electron microscopy. The antibiotic-resistance modifying activity of both agents was studied against selected troublesome isolates showing resistance to amikacin, meropenem and cefotaxime. Molecular docking of citric acid and eugenol with NDM-1, as well as the docking of citric acid with AAC(6′)-Ib and CTX-M-15 were carried out to explain the resistance modifying activity of the tested agents. Capsule formation was the most prominent virulence factor that was detected in all isolates. Both citric acid and clove oil could effectively reduce the size of the formed bacterial capsules. Citric acid showed promising synergistic effects when combined with the studied antibiotics against all the tested isolates. However, clove oil showed a synergistic effect only against 50% of the tested isolates when combined with meropenem. Relying on their binding efficiency mode obtained from molecular docking studies, the tested agents were recognized as promising inhibitors of the studied enzymes. In conclusion, both citric acid and clove oil are auspicious anti-virulence and resistance-modifying agents that can be combined with conventional antibiotics to combat virulent and multidrug resistant Klebsiella isolates.