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Background: Medicinal plants have always played an important role in human health. Many plants are traditionally used as drugs against microbial infections. In this study, a panel of seven methanol extracts from Cameroonian edible was assessed for their antibacterial potentiality against multidrug-resistant Gram-positive and Gram-negative bacteria. Methods: The microdilution technique using a 96-well plate was used to assess the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the crude extracts, as well as their potential to improve the antimicrobial activity of certain families of antibiotics. Phytochemical screening of the extracts was carried out according to the standard methods. Results: The most detected classes of pharmaceuticals were tannins, triterpenes, polyphenols, and steroids. Coffea arabica bark extract inhibited all 20 tested MDR bacteria strains; Coffea arabica leaf and seeds extracts, Adansonia digitata bark extract, Sechium edule leaf extract, all inhibited 95% (19/20) of the strains tested, Beilschmeidia louisii stem extract inhibited the growth of 85% (17/20) of the tested bacteria, while Hyphaene therbaica displayed 70% (14/20) bacterial inhibition. The MIC values of the plant extracts ranged from 256 to 2048 μg/mL. However, the best MIC value (256 μg/mL) was obtained with B. louisii stem extract against E. coli AG102 and S. aureus MRSA12. The leaf extract of S. edule improved the anti-bacterial activities of kanamycin, tetracycline, and Cloxacillin against the MDR strain P. stuartii 29916 by up to 16 times; furthermore, this extract improved the antibacterial effect of tetracycline, Cloxacillin, kanamycin, and doxycycline by 16 folds against the MDR strain E. coli AG100ATET; the bark extract of C. arabica improved the activities of ofloxacin, chloramphenicol the activities of ofloxacin, chloramphenicol, and doxycycline toward all the tested MDR Gram positive and Gram-negative bacteria with improvement activity factor (IAF) ranging from 2 to 16, while the leaf extract of B. louisii increased up to 8-fold the activity of Cloxacillin against P. aeruginosa PA 124. Conclusion: Coffea arabica, Adansonia digitata, Sechium edule, and Beilschmeidia louisii are the explorable sources of antibacterial agents usable alone or in combination with conventional antibiotics to tackle diseases caused by resistant bacterial phenotypes. Keywords: Bacterial infections; Cameroon; edible plants; Multidrug resistance; Antibiotic-potentiation.

Background: Bacterial infections, especially those caused by multidrug-resistant (MDR) Gram-negative bacteria, remain a global health concern. Previous studies have reported the antibacterial activities of the methanol extract of the leaves of Acacia polyacantha Willd. (Fabaceae) (APL) as well as some of its phytoconstituents. In this study, APL and its constituent, 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (GGOA) were evaluated on growth kinetics, bacterial membrane, and H+-ATPase proton pumps. The acute toxicity of APL was also studied. Methods: The effects of APL and GGOA on bacterial growth kinetics and the bacterial membrane was determined using spectrophotometric methods. Their effects on the bacterial H+-ATPase proton pumps were evaluated through the acidification of the bacterial external environment using a pH-meter. The acute toxicity of APL was determined using the standard limit test method described by the Organization for Economic Cooperation and Development (OECD) code 425. Results: APL and GGOA modified the bacterial kinetics of Providencia stuartii ATCC29916 with emphasis on the latent phase. They blocked the proton pumps of this bacterium and destroy the bacterial membrane. The medium lethal dose (LD50) of APL was greater than 5000 mg/kg body weight (b.w.). Conclusion: The results of the present study provide important and complementary information on APL and GGOA as good antibacterial candidates for combating infections due to MDR Gram-negative bacteria. Keywords: 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid; Acacia polyacantha; acute toxicity; Gram-negative bacteria; mode of action; multidrug resistance.

Chronic exposure of mosquito larvae to pesticide residues in agricultural areas is often associated with evolution of resistance to insecticides used for vector control. This presents a concern for the efficacy of clothianidin, an agricultural neonicotinoid qualified for Indoor Residual Spraying (IRS). Using standard bioassays, we tested if reduced susceptibility to clothianidin affects the efficacy of SumiShield® 50WG, one of the two newly approved formulations, which contains 50% clothianidin. We simultaneously monitored susceptibility to clothianidin and to SumiShield® 50WG, testing adults of Anopheles gambiae, An. coluzzii and Culex sp collected from urban, suburban and agricultural areas of Yaoundé. We found that the level of susceptibility to the active ingredient predicted the efficacy of SumiShield® 50WG. This formulation was very potent against populations that achieved 100% mortality within 72 h of exposure to a discriminating dose of clothianidin. By contrast, mortality leveled off at 75.4 ± 3.5% within 7 days of exposure to SumiShield® 50WG in An. gambiae adults collected from a farm where spraying of acetamiprid and imidacloprid is driving cross-resistance to clothianidin. These findings indicate that more potent formulations of clothianidin or different insecticides should be prioritized in areas where resistance is emerging.

The present study aimed to assess the in vitro antibacterial and antibiotic modifying activities of methanol extracts prepared from the leaf (APL) and bark (APB) of Acacia polyacantha, fractions (APLa-d) and compounds isolated from APL against a panel of multidrug resistant (MDR) Gram-negative bacteria. Leaf extract was subjected to column chromatography for compounds isolation; antibacterial assays were performed on samples alone and with an efflux pump inhibitor (EPI), respectively, and several antibiotics on the tested bacteria. The phytochemical investigation of APL led to the isolation of stigmasterol (1), β-amyrin (2), 3-O-β-D-glucopyranosylstigmasterol (3), 3-O-methyl-D-chiro-inositol (4), epicatechin (5), quercetin-3-O-glucoside (6), 3-O-[β-D-xylopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (7), and 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (8). APL and APB had minimal inhibitory concentration (MIC) values ≤ 1024 μg/mL on 73.3% and 46.7% of the tested bacteria, respectively. APLb and APLd were effective against 88.9% of tested bacterial species with compound 8 showing the highest activity inhibiting 88.9% of tested bacteria. The EPI, phenylalanine-arginine-β-naphthylamide (PAßN), strongly improved the activity of APL, APLb, APLd, and compound 8 on all tested bacteria. Synergistic effects were obtained when APL and compounds 7 and 8 were combined with erythromycin (ERY), gentamycin (GEN), ciprofloxacin (CIP), and norfloxacin (NOR). The present study demonstrates the antibacterial potential of Acacia polyacantha and its constituents to combat bacterial infections alone or in combination with EPI.