EVALUATION OF LETHAL ACTIVITY OF PSIDIUM GUAJAVA LINN. EXTRACTS ON BACTERIAL PATHOGENS CAUSING DIARRHEAL INFECTIONS

Abstract

Treatment of diarrheal infections is often challenged by development of drug resistance among the bacteria. The aim of this study was to investigate the antibacterial property of extracts of guava (Psidium guajava Linn.) leaves against diarrhea causing bacterial pathogens. Four extracts viz., ethanol, methanol, ethyl acetate and hot water extract of guava leaf were assayed for antibacterial activity against three selected bacterial pathogens along with four commercial antibiotics. The methanol extract exhibited substantial inhibitory activity (100%) against both kinds of bacteria with a MIC of >250 µg/ml in most cases. The ethanol extract demonstrated antibacterial activity ranging from 38% to 65% with the inhibition of clinical isolate of E. coli at concentrations >500 µg/ml and both strains of V. cholerae at >750 µg/ml respectively. The ethyl acetate and hot water extracts showed comparatively lesser response with MICs >750 µg/ml in some cases. The commercial antibiotic Chloramphenicol exhibited absolute inhibitory action on Salmonella sp. and clinical isolate of V. cholerae. While Tetracycline and Gentamycin caused complete bactericidal action on both the strains of E. coli and V. cholerae respectively, the clinical isolate of E. coli was totally susceptible to Erythromycin. On the other hand significant percentages of resistances to these antibiotics ranging from 63% to 88% were also recorded. Six phytochemical compounds presumed to possess pharmacological properties were detected from methanol extract. The findings suggest that the methanol extract of guava leaf could serve as a potential source to explore promising drugs to control diarrheal infections.