Abstract:
Drug resistance is a serious threat to human existence today. This study investigated
sensitivity of selected pathogenic microorganisms to antibiotic extracts from soils of
Menengai crater geothermal vents in Kenya. Antibiotic producing actinomycetes
were isolated from geothermal vents and identified using colony characteristics and
biochemical means. Sensitivity of selected pathogenic microorganism was carried
out using primary and secondary screening techniques. Four actinomycetes coded
PAN 9, PAN 18, PAN 117 and PAN 138 were selected for further analysis based on
the size of zone of inhibition and broad spectrum of activity. Extraction of antibiotics
was carried out using ethyl acetate. Sensitivity test of the pathogens to the extracts
was done using Karby Bauer disk diffusion technique and Cytotoxicity of antibiotic
extracts carried out using Brine shrimp lethality test and sheep blood hemolytic
bioassays. Isolates presented typical actinomycetes characteristics. A total of 20
actinomycete isolates showed antagonism against the test pathogenic
microorganisms. Selected actinomycetes inhibited growth of Gram positive and
negative bacterial and fungal pathogens in both primary and secondary sensitivity
tests. There was a significant difference in the diameters of zones of inhibition
produced by the test pathogens when subjected to antibiotic metabolites from the
selected actinomycetes (F = 6.6046 P = 0.001338). The minimum inhibitory
concentration and minimum bactericidal concentration/minimum fungicidal
concentration did not vary significantly (F=0.4503, P = 0.7187). The LC50 values of the
antibiotic extracts varied from 2.438±0.47µg in PAN 9 to 9.3455±0.41µg in PAN 138.
PAN 19 and PAN 117 showed partial hemolysis while PAN 9 and PAN 138
exhibited complete hemolysis of sheep erythrocytes. There is need to purify and
conduct structural elucidation of these antibiotics to determine whether or not the
observed hemolysis resulted from the said antibiotics or other compounds in the
extract.
