THROAT INFECTIONS

Abstract

This study evaluated the antibacterial efficacy of Garcinia kola seeds (commonly called bitter kola) and honey against bacteria involved in throat infections. Throat swab specimens were collected from patients at the Ear, Nose and Throat (ENT) department of University of Medical Sciences Teaching Hospital, Akure and cultured on nutrient, blood, chocolate and MacConkey agar. Bacterial isolates were identified using morphological, biochemical and molecular characteristics. Typed isolates of bacteria involved in throat infections were obtained from Federal Institute of Industrial Research, Oshodi, Lagos State. Fresh seeds of G. kola and honey were obtained commercially from the main market, Akure. Garcinia kola seeds were extracted using ethanol, methanol, ethyl acetate, acetone, cold water and hot water as extraction solvents. Proximate analysis was done on honey using standard method. Quantitative and qualitative phytochemical analyses were carried out on both the G. kola seed extracts and honey. Structural elucidation of G. kola seeds ethyl acetate extract was done using gas chromatography-mass spectroscopy analysis. Assays on antibacterial efficacy, minimum inhibitory and bactericidal concentrations of extracts from G. kola seeds, honey and conventional antibiotics were carried out on clinical and typed bacterial isolates using agar well diffusion method. Mechanisms of action and time-kill kinetics of extracts from G. kola seeds on susceptible bacterial isolates were investigated using standard methods. The synergistic antibacterial potential of mixtures of G. kola seeds extract and honey (ratios 1:1, 1:2 and 2:1) and mixtures of G. kola seeds extract, honey and ciprofloxacin (ratios 1:1:1, 1:2:1 and 2:1:1) were determined using agar well diffusion method. The prevalence of the bacterial isolates were: Streptococcus pneumoniae (28%), S. pyogenes (23%), Staphylococcus aureus (21%), Klebsiella pneumoniae (15%), Enterobacter bugandensis (9%) and Escherichia coli (4%). The typed isolates collected were S. pyogenes ATCC 12384, S. aureus NCTC 6571, E. coli ATCC 25922 and K. pneumoniae ATCC 13888. Acetone extract of G. kola seeds had the highest extraction yield of 12.2% while methanol had the lowest yield (3.4%). Carbohydrate was the most abundant in the honey sample from the proximate composition obtained. Cardiac glycosides were present in all the extracts and honey while phlobatannins were absent. Gallic and p-Coumaric acids among others were found in ethyl acetate extract of G. kola seeds. S. aureus was resistant to gentamycin (30 μg), according to clinical and laboratory standards institute. At 100 mg/ml, purified ethyl acetate extract of G. kola seeds was most effective against S. pneumoniae with 30±0.58 mm zone of inhibition while purified hot water extract was least effective with 6.00±0.58 mm against S. pyogenes. Honey sample (100%) was most effective against E. coli with 15.67±0.33 mm and least effective against K. pneumoniae with 9.33±0.33 mm. Ethyl acetate extract showed the lowest MIC and MBC at 6.25 mg/ml and 12.5 mg/ml respectively against S. aureus. The mechanisms of action of ethyl acetate extract from G. kola seeds against tested bacteria are protein, sodium and potassium ions leakages. The highest leakages of Na + and K + was observed in K. pneumoniae at 350 mol/kg and 82 mol/kg respectively while the highest leakage of proteins was observed in S. aureus at 88.55±5.34 mg/ml concentration. The number of S. pneumoniae cells reduced from 607 colony forming unit (cfu) to 528 cfu when treated with G. kola seeds ethyl acetate extract and incubated at an interval of 30 minutes from the initial incubation time. In conclusion, synergism between G. kola seeds ethyl acetate extract and honey was observed in S. pyogenes ATCC 12384, S. pyogenes, E. coli ATCC 25922, E. coli and K. pneumoniae ATCC 13888 with fractional inhibitory concentrations of 0.313, 0.375, 0.250, 0.375 and 0.313 respectively. Therefore, G. kola seeds and honey may be used either singly or in combination for the treatment of throat infections.