EFFECTS OF COTTON PLANT (GOSSYPIUM HERBACEUM LINN.) EXTRACTS ON SOME VANCOMYCIN AND METHICILLIN-RESISTANT PATHOGENIC BACTERIA

Abstract

Bacterial resistance to antibiotics is a serious global problem, hence attention is being turned to plants as alternative source of antimicrobial to combat the menace of antibiotic resistance among pathogenic microorganisms. This study investigated the antibacterial properties of Gossypium herbaceum leaf extracts against a collection of vancomycin and methicillin-resistant pathogenic bacteria. Bacterial isolates of clinical sources were obtained from Don Bosco Catholic Laboratory, Akure, Nigeria and typed cultures from Microbiology and Parasitology department, Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria. The clinical isolates included Staphylococcus aureus, Streptococcus pyogenes, Streptococcus faecalis, Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli, Acinetobacter baumannii, and Salmonella typhi. Antibiotic sensitivity test was carried out on the bacterial isolates using the disc diffusion method. The antibiotic resistant organisms include P. aeruginosa, S. typhi, E. coli, S. aureus, S. faecalis, H.Streptococcus, Proteus mirabilis, K.pnuemoniae and A. baumannii. The antibiotic resistant organisms were further screened for the presence of plasmids and plasmid curing was carried out. Extracts from G. herbaceum Linn leaf was obtained by means of cold extraction using methanol and n-hexane as solvents. The phyto-constituents of the crude methanol and n-hexane extracts were qualitatively and quantitatively determined. The crude extracts were further screened for their antbacterial activity against the test bacteria. The methanol and n-hexane extracts were purified using column chromatography. The purified fractions were screened for their antibacterial properties against the test organisms. Infrared analysis of the bioactive fractions was then carried out to determine the functional groups present in them. The plasmid profiling revealed the presence of plasmid in P. aeruginosa and S. aureus. The phytochemical screening of the crude of both methanol and hexane extracts revealed the presence of flavonoids, steroids, tannins, terpenoids and glycosides. The methanol and n-hexane extracts of G.herbaceum Linn..exhibited antibacterial activity against vancomycin and methicillin resistant bacteria. The zone of inhibition of the leaf extract on the test organisms at concentration of 200mg/mL ranged between 21.35 – 4.10mm and 18.75 – 5.05mm for n- hexane and methanol extracts respectively. Minimum inhibitory concentrations (MIC) of n-hexane and methanol extracts on the test organisms ranged between 25mg/mL – 6.25 mg/mL and 50mg/mL – 6.25 mg/mL respectively. Fourier transform infra-red spectroscopy (FTIR) analysis of the fractions revealed that the methanol fraction of the extract has six distinct bioactive compounds belonging to alkenes, alcohol, amine, phenol, nitro compounds and alkanes. In conclusion, the demonstrated antibacterial activities of methanol and n-hexane leaf extracts in this study have given a preface of their potentials as antibacterial agents.