Synergistic effects of alum and guava (Psidium guajava) leaf extracts on some pathogens from clinical samples

The study investigates the synergistic effects of Guava (Psidium guajava) aqueous and methanolic leaf extracts in combination with potassium aluminum sulphate (Alum) respectively. The various concentrations (0.5, 1.0, 1.5 and 2.0%) of these combinations; methanolic leaf extract plus Alum (MLE+Alum) and aqueous leaf extract plus Alum (ALE+Alum) were tested respectively for antibacterial activity on some bacterial pathogens isolated from clinical samples. These were compared with an antibiotic standard, Chloramphenicol as positive control. Antibacterial activity was assessed using both disc diffusion method (DDM) and agar well diffusion method (AWDM) respectively. Of these combinations, ALE+Alum concentrations exhibited the largest mean diameter of inhibitory zone (DIZ) values of 12.0-21.0mm and 8.5-15.0mm on the test bacteria using AWDM and DDM respectively. In contrast, there was no inhibition with MLE+Alum concentrations by AWDM whereas DIZ values ranged from 8.0-13.5mm by DDM. The susceptibility of these pathogens to the combinations were much more pronounced against the Gram-negative bacteria, Pseudomonas aeruginosa (21.0mm) and Escherichia coli (20.0mm) than Gram-positive, Staphylococcus aureus and Bacillus subtilis (19.0mm) respectively, thus, indicative of broad spectrum activity particularly using the AWDM. This result is almost comparable with Chloramphenicol which exhibited the overall largest mean DIZ values. However, the activity of Chloramphenicol was marginally influenced by the methodology of antibacterial assessment which reinforces the fact that purified and tested antibiotics should be used as the drug of choice for treatments. The synergistic effects of the P. guajava leaf extracts plus Alum against test bacteria reveals that they can be used as a novel antibacterial agent against infections and/or diseases caused by these pathogens.