ANTIMICROBIAL ACTIVITIES OF PLANTS USED BY Rattus norvegicus IN MAKING ITS NEST ON SELECTED HUMAN AND SKIN PATHOGENS

Abstract

The antimicrobial activities of the plants used by Rattus norvegicus in the construction of its nest were studied. The study reveals the use of Bidens pilosa and Tridax procumbens leaves by R. norvegicus to constructing its nest. Hence, the antimicrobial activities of the ethanolic, aqueous and chloroform extracts of these plants at different concentrations of 25 mg/mL, 50 mg/mL and 100 mg/mL were evaluated on the organisms isolated from soil samples in R. norvegicus environs and nest. Antimicrobial activities of the extracts were also screened on clinical skin pathogens and their corresponding type cultures at concentrations of 50 mg/mL, 100 mg/mL and 200 mg/mL respectively using agar well diffusion method. The extracts obtained from T. procumbens exhibited broad spectrum activities on all the organisms except Pseudomonas chlororaphis and Bacillus brevis. The diameter zones of inhibition ranged from 5.06±0.15 to 18.36±0.37 mm on isolated organisms at 100 mg/mL. However, the extracts obtained from Bidens pilosa exhibited broad spectrum activities on all the isolated organisms except Ps. aeruginosa, Ps. chlororaphis, B. subtilis, B. brevis and P. italicum. The zones of inhibition ranged from 3.73±0.15 to 12.73±0.25 mm on the isolated organisms at 100 mg/mL. It was observed that the Gram positive bacteria were more susceptible to the extracts than the Gram negative organisms. The zones of inhibition of T. procumbens extracts on the test bacteria and fungi at the concentration of 200mg/mL ranged from 5.00±0.00 to 15.20±0.20 mm, the lowest effect was observed on P. aeruginosa, while the highest was observed on Staphylococcus aureus ATCC 43300. The ethanolic extract of T. procumbens had antifungal activities on Trichophyton mentagrophyte and T. mentagrophyte ATCC 9533 with the zones of inhibition of 8.00±0.00 mm and 11.26±0.15 mm diameter respectively at 200 mg/mL while A. flavus and A. flavus ATCC 9643 were both resistance to the extract at all concentration tested. The results of the synergistic antibacterial activities of T. procumbens and B. pilosa on the selected clinical and typed organisms were more effective in inhibiting the isolates than when used separately. Ethanolic extract of these plants were more effective in antimicrobial activities on the test organisms compared with chloroform and aqueous extracts of these plants. It was observed that the type organisms were more susceptible to the extracts than the clinical pathogens. The metabolites obtained from Bacillus brevis isolated from the nest exhibited antagonistic activities against S. aureus and P. aeruginosa isolated from the soil samples with the inibition zones of 22.13±0.32 mm and 18.20±0.10 mm respectively. The sensitivity test of commercial antibiotics 3 on the isolated organisms displayed broad spectrum activities on the bacterial isolates with the zones of inhibition ranging from 3.46±0.15 mm to 18.70±0.10 mm diameter. The lowest potency was observed on E. coli while the highest was observed on S. aureus; however, all the isolates were resistance to augmentin and cloxacillin. The plasmid profile analysis of B. brevis revealed the presence of plasmid (16588 bp) which could be responsible for its multi-drug resistance pattern displayed. The minimum inhibitory concentration (MIC) of the ethanolic, aqueous and chloroform extracts of these plants determined by tube dilution method ranged between 25 to 250 mg/mL for clinical organisms subjected to T. procumbens and B. pilosa extracts and 12.5 to 250mg/ml for typed organisms with S. aureus having the least MIC value. The phytochemicals screening revealed the presence of tannins, alkaloids, flavonoids, saponins and cardiac glycosides in both plants. The histopathological analysis of an orograstically dosed albino rats with S. aureus showed that the synergistic effect of B. pilosa and T. procumbens were more effective in the treatment of the pathological effects caused to the organs of the rats than when used singly. The results of this study support the use of these plants selected by R. norvegicus in controlling pathogenic microorganisms from its environment especially skin-related infectious microorganisms such as Staphylococcus aureus. It is also noteworthy that this study can serve as a basis for controlling the effect of these pathogens in humans too when applied or used in a purified state.