Botanicals from the flowers of Vernonia calvoana and the leaves of Senna spectabilis showed anti-Klebsiella activity and potentiated the activity of antibiotics against multidrug-resistant phenotypes overexpressing efflux pumps

Background: The alarming trend of infectious diseases in public health is mainly due to bacterial multidrug resistance, the emergence of which is partly caused by the inappropriate use of antibiotics. Bacteria of the Klebsiella genus have acquired a priority level of resistance to antibiotics, reducing their effectiveness. The aim of this study was to evaluate the anti-Klebsiella activity of methanol extracts of Vernonia calvoana flowers and Senna spectabilis leaves against multidrug-resistant Klebsiella phenotypes overexpressing efflux pumps. Methods: The antibacterial activity of Vernonia calvoana and Senna spectabilis extracts alone, in combination with Phenylalanine-Arginine β-Naphthylamide (PAβN) and antibiotics, was assessed using the liquid medium microdilution method. Qualitative phytochemical composition was determined according to reference experimental protocols. Results: Phytochemical screening of the different methanol extract revealed the presence of alkaloids, triterpenes, polyphenols, flavonoids and saponins. These extracts had inhibition spectra of 93.75%, with MICs ranging from 32 to 1024 µg/mL for Vernonia calvoana flower extract and from 16 to 1024 µg/mL for Senna spectabilis leaves. The excellent activity with a MIC value of 32 µg/mL against K. oxytoca isolate (KO95) and 64 µg/mL against K. pneumonia isolate (KP203) was observed in Vernonia calvoana flower extract. However, Senna spectabilis leaf extract showed an excellent activity, with MIC values of 16 µg/mL against K. pneumoniae (KP175) and 64 µg/mL against K. pneumoniae (K2) and K. oxytoca (KO107) strains. The anti-Klebsiella activity of Vernonia calvaona flower extract and Senna spectabilis leaf extract was improved by 87.5% and 100% respectively in the presence of PAβN, with activity improvement factor (AIF) values ranging from 2 to 256. Both extracts modulated the activity of antibiotics with activity modulator factor (AMF) values ranging from 2 to 128. The activity of ceftriaxone and tetracycline was enhanced to at least 75% at MIC/2 and MIC/4, imipenem and cefixime were modulated to 50% at MIC/2 and MIC/4 respectively, and levofloxacin to 62.5% at MIC/2. Conclusion: Extracts from Vernonia calvaona flowers and Senna spectabilis leaves can be used alone or in combination with the usual antibiotics against Klebsiella phenotypes overexpressing efflux pumps, but further investigation is needed to identify the active compounds responsible for the observed activity. Keywords: antibacterial; antibiotics; efflux pumps; multidrug resistance; Klebsiella species; Senna spectabilis; Vernonia calvaona