We screened forty crude extracts of twenty Cameroonian medicinal plants commonly used to treat bacterial infections for broad spectrum antibacterial activity, as a more affordable alternative against resistant organisms. The extracts were screened on common pathogenic gram negative and gram positive bacteriainitially by the disc diffusion method followed by the tube dilution method. Using discs containing 30µg of extract,
Escherichia coli
coli showed sensitivity to 23 extracts with diameter of zone of inhibition ranging from 7 – 19mm, fifteen of which were up to or > 10mm.
Pseudomonas aeruginosa
was sensitive to 11 extracts, whereas
Salmonella typhimurium
and
Staphylococcus aureus
were not sensitive to any of the extracts. Based on the zones of inhibition the activity of the extracts were equivalent to 30 to 138 % efficacy of the standard antibiotic discs. The lowest Minimum Inhibitory Concentration (MIC) recorded was 2 mg/ml for
Euphorbia hirta
against
S. aureus and
P. aeruginosa and the lowest Minimum Bactericidal Concentration (MBC) was 6 mg/ml for six extracts from
Ageratum conyzoides
,
Aframomum citratum
,
Euphorbia hirta,
Momordica charantia
,
Mangifera indica
and
Khaya senegalensis
against three bacterial species. Three extracts had broad spectrum bacteriostatic activity (MICs ≤ 4 mg/ml) while in terms of MBCs none of the extracts showed broad spectrum bactericidalactivity. We conclude that most of the tested plants used as traditional antibacterials have a bacteriostatic effect on gram-negative pathogenic bacteria.
