Assessment of antibiotics production potentials in four actinomycetes isolated from aquatic environments of the Eastern Cape Province of South Africa

Crude extracts of four actinomycetes species belonging to Actinoplane [NB 034],Streptomyces [TR 007] and Actinopolyspora [NB 069 and TR 008] genera were screened for antibacterial activities against a wide range of bacterial strains. The extracts showed antibacterial activities against both Gram-negative and Gram-positive test bacteria with zones of inhibition ranging between 2 and 27 mm (NB 034); 9 and 15 mm (TR 007); 8 and13 (NB 069) and 2 and 12 mm (NB 069). The minimum inhibitory concentration (MIC) of the extracts against the test bacteria ranged from 0.039 - 5 mg/ml, while the minimum bactericidal concentrations (MBC) ranged from 5 to >10 mg/ml. The extracts exhibited concentration-time dependent killing of Staphylococcus aureus OKOH2A and Staphylococcus scuiri OKOH2B with a 0.73log10 and 0.88log10reduction in viable counts respectively, while a re-growth phenomenon was exhibited byKlebsiella pneumonia ATCC 4352 and Escherichia coli ATCC 25922 at MIC, 2 × MIC and 4 × MIC of Streptomyces (TR 007) Actinopolyspora (TR 008) extracts. All the active extracts exhibited bacteriostatic activities.   Key words: Actinoplane, Streptomyces, Actinopolyspora, antibiotic production.