Investigating the anti-growth, anti-resistance, and anti-virulence activities of Schoepfia schreberi J.F.Gmel. against the superbug Acinetobacter baumannii

Abstract

Schoepfia schreberi has been used in Mayan folk medicine to treat diarrhea and cough. This study aimed to determine the anti-growth, anti-resistance, and/or anti-virulence activities of S. schreberi extracts against Acinetobacter baumannii, a pathogen leader that causes healthcare-associated infections with high rates of drug-resistant including carbapenems, the last line of antibiotics known as superbugs, and analyze their composition using HPLC-DAD. Ethyl acetate (SSB-3) and methanol (SSB-4) bark extracts exhibit antimicrobial and biocidal effects against drug-susceptible and drug-resistant A. baumannii. Chemical analysis revealed that SSB-3 and SSB-4 contained of gallic and ellagic acids derivatives. The anti-resistance activity of the extracts revealed that SSB-3 or SSB-4, combined with imipenem, exhibited potent antibiotic reversal activity against A. baumannii by acting as pump efflux modulators. The extracts also displayed activity against surface motility of A. baumannii and its capacity to survive reactive oxygen species. This study suggests that S. schreberi can be considered a source of antibiotics, even adjuvanted compounds, as anti-resistant or anti-virulence agents against A. baumannii, contributing to ethnopharmacological knowledge and reappraisal of Mayan medicinal flora, and supporting the traditional use of the bark of the medicinal plant S. schreberi for the treatment of infectious diseases.

Keywords: Acinetobacter baumannii; Anti-resistance; Anti-virulence; Drug-resistance; Mayan medicinal plant; Phenolic acids; Superbug.

Fig. 1

Chemical structures of gallic (1) and ellagic acids (2).

Fig. 2

HPLC-DAD chromatograms of SSB-3 and SSB-4 as well as UV spectra at 340 nm. (a) HPLC-DAD chromatogram of SSB-3. (b) HPLC-DAD chromatogram of SSB-4. (c) HPLC-DAD chromatogram of standard EA®, as well as UV spectra at 340. (d) HPLC-DAD chromatogram of standard GA®, as well as UV spectra at 340 nm. (e) UV spectra at 340 of derivatives of EA and GA from SSB-3. (f) UV spectra at 340 of derivatives of EA and GA from SSB-4. SSB-3: EtOAc S. schreberi bark extract, SSB-4: MeOH S. schreberi bark extract, GA: gallic acid, EA: ellagic acid. *Derivatives of EA. †Derivatives of GA.

Fig. 3

Flowchart of this research. Aq: aqueous; Hex: n-hexane; EtOAc: ethyl acetate; MeOH: methanol; SSL: S. schreberi leaves extract; SSB: S. schreberi bark extract; GA: gallic acid; EA: ellagic acid.

Fig. 4

Effect of extracts of S. schreberi and phenolic acids on the biofilm formation of UIMY-ABA-81. SSB-3: EtOAc bark extract of S. schreberi; SSB-4: MeOH bark extract of S. schreberi bark; GA: gallic acid; EA: ellagic acid. EDTA: ethylenediaminetetraacetic acid. One-way ANOVA was performed, and Tukey's post hoc test (P ≤ 0.05) was conducted to compare the % of biofilm-formation inhibition in the different groups. Different letters indicated significant differences. In addition, the control group (EDTA) was compared to experimental groups (*P ≤ 0.0001).

Fig. 5

(a) Images of agar plates images showing the effects of SSB-3, SSB-4, GA, and EA on the surface motility of UIMY-ABA-205 at 250 μg/mL. (b) Effect of SSB-3, SSB-4, GA, and EA on surface motility of UIMY-ABA-205 at 250 μg/mL. (c) Effect of SSB-3 and SSB-4 at three concentrations (250, 125, and 62.5 μg/mL) on surface motility of UIMY-ABA-205. SSB-3: EtOAc bark extract of S. schreberi; SSB-4: MeOH bark extract of S. schreberi bark; GA: gallic acid; EA: ellagic acid. Azt: Azithromycin. One-way ANOVA was performed, and the Tukey's post-hoc test (P ≤ 0.05) was conducted to compare the % of motility in the different groups. Different letters indicate significant differences between groups. In addition, the control group (Azt) was compared to experimental groups (*P < 0.0041, **P < 0.0013, ***P < 0.006, ****P ≤ 0.0001, ¥: not significant).

Fig. 6

Effect of SSB-3, SSB-4, GA, and EA on UIMY-ABA-205 after treatment with H₂O₂. SSB-3: EtOAc bark extract of S. schreberi; SSB-4: MeOH bark extract of S. schreberi bark; GA: gallic acid; EA: ellagic acid. One-way ANOVA was performed, and Tukey's post-hoc test (P < 0.05) was conducted to compare the % of mortality among the different groups. Different letters indicate significant differences.