In vitro antimicrobial activity of Millettia laurentii De Wild and Lophira alata Banks ex C. F. Gaertn on selected foodborne pathogens associated to gastroenteritis

Abstract

This study aimed at evaluating the antimicrobial potential of aqueous, ethanolic and methanolic extracts of two Cameroonian plants against selected foodborne pathogens. Bioactive compounds were extracted from <i>Millettia laurentii</i> De Wild seeds and <i>Lophira alata</i> Banks ex. C. F. Gaertn leaves using distilled water, ethanol and methanol as solvents. The extracts were tested against <i>Escherichia coli</i> O157, <i>Bacillus cereus</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, <i>Proteus mirabilis</i>, <i>Moraxella morganii</i>, <i>Salmonella enteritidis</i>, <i>Klebsiella pneumoniae</i> and <i>Listeria monocytogenes</i> using the microdilution method. The results showed that distilled water extracted a more important mass of phytochemical compounds (18.0-24.60%) compared to ethanol (4.80-5.0%) and methanol (4.20-4.60%). All the extracts exhibited significant antimicrobial activity with MIC values ranging from 5 to 20 μg/mL for <i>M. laurentii</i> seeds extracts and from 1.0 to 20 μg/mL for <i>L. alata</i> leaves extracts. The different plant extracts were ten times less active than gentamicin. The most active extracts were obtained using ethanol as solvent and <i>K. pneumoniae</i> was the most resistant pathogen to all extracts (MBC>20 μg/mL). <i>M. laurentii</i> extracts were bactericidal against <i>L. monocytogenes</i> and <i>P. mirabilis</i> while the reference antibiotic (gentamicin) was bacteriostatic against these pathogens. The results obtained from this study suggest the studied local plant materials as a source of antimicrobial compounds which can be valorized in the medical field as substitute of antibiotics for which many microorganisms have nowadays developed resistance mechanisms. Further studies need to be performed in order to characterize and identify these antimicrobial active molecules.