REPELLENT POTENTIAL OF MICROBIAL METABOLITES EXTRACTED FROM HUMAN SKIN MICROFLORA AGAINST Anopheles gambiae

Abstract

The study is carried out to determine the repellency activity of microbial metabolites extracted from human skin microflora against adult Anopheles gambiae. Skin surface of one hundred and fourteen (114) consented participants were swabbed at different locations (elbow, neck, and knee) on the body and examined for the microbial diversities using standard microbiological methods. Socio-demographic characteristics, knowledge and awareness of malaria and mosquito control among the participants were evaluated with the use of multiple choice questionnaire. Resident skin flora was selected by triglyceride oil degradation and mineral salt medium for the production of secondary metabolite. The metabolite were separated from the culture by centrifuge at 1500 rpm for ten minutes, and partially purified from the supernatant using 70% ethyl-acetate. The repellent efficacy of different concentration of the metabolite against the mosquitoes under laboratory condition was determined.The metabolite was analyzed for its chemical and structural composition using furrier transform infrared spectroscopy (FTIR) and Gas Chromatography-Mass spectrophotometry (GCMS). Majority of the participants were aged 31-40 years.Male and female participants were 67(58.8%) and 47(41.2%) respectively. All the participants have heard of malaria, while 60(52.6%) of them have been diagnosed of malaria in the last 6 months, 28.9% of the participants have their personal mosquito repellant as at the time of this investigation while 71.1% did not have mosquito repellant. Bacterial counts (Log10 CFU/cm2) ranged from 5.70±0.13 (neck) to 6.51±0.05 (knee fold) while the highest fungal counts (Log10 SFU/cm2) was observed in knee fold (2.80±0.07) followed by inner-elbow (2.61±0.04) and neck (1.91±0.05). Ten (10) bacterial and nine (9) different fungal species were identified, the most occurred bacterial genus in the skin of the neck, inner-elbow and knee fold were Staphylococcus (49.36%), Bacillus (42.23%) and Staphylococcus (43.75%) respectively while the most occurred fungal genus were Aspergillus (36.54%), Aspergillus vi (50%) and Alternaria (18.92%) in the neck, inner-elbow and knee fold skin respectively. C. xerosis, S. aureus, P. aeruginosa, S. epidermidis,M. furfur, E. dermatididis andA. niger degraded the triglyceride oil significantly (p≤0.05) and were used for secondary metabolite production. Metabolite of S. epidermidis and A. nigerhad the highest (100%) repellency activity at 100%, 60% and 20% concentration after 10 minutes post-application. Metabolite of S. epidermidis showed extended repellency activity at 100% till 90 minutes. Fourteen different functional groups were detected in metabolite of S. epidermidis and the most abundant compound were glutamic acid,1-Pentanone, 1-(4-methoxyphenyl)- oxim,bornyl acetate, phenol, 2,6-dimethoxy, benzoic acid, 4-hydroxy-3,5-dimethoxy and 3,5-dimethyl-1-phenyl-4- nitrosopyrazole while metabolite of A. nigerhas fifteen different functional groups and the most abundant compound were glutamic acid; 1,2,3-Benzenetriol; propane, 1,1-diethoxy-; hexane, 2,2- dimethyl-; paraldehyde and glutaric acid, tridec-2-yn-1-yl 4-acetylphenyl ester. The results of the study showed that metabolite of S. epidermidis was potential agent for confirming protection on the exposed parts of human body against Anopheles gambiae for at least 90 min and as such can be included in integrated vector management to reduce malaria infection in endemic areas.