ANTIBACTERIAL ACTIVITIES OF HUMAN SERUM TO Staphylococcus aureus AND Escherichia coli

ABSTRACT

Two bacterial isolate, Escherichia coli and Staphylococcus aureus are involved in nosocomical and sometimes, community infections. They are therefore of public health importance. The study evaluated the antibacterial activities of human serum to Escherichia coli and Staphylococcus aureus. These organisms were obtained from the department of medical microbiology, UBTH, and were re-identified and confirmed using morphological, cultural and biochemical characteristics using standard methods. The antibacterial activity of serum for these organisms was carried out by the disc sensitivity method. Sterile paper disc were prepared and used. Each disc was inserted into the serum sample, allowed to drain off the excess serum and placed on the already streaked Muller-Hilton agar plates. This was incubated at 37oC for between 18 to 24 hr. and the zone of inhibition was taken for each bacterial isolate. It was observed that after 12 hr, the zone of inhibition was 4.2 mm for Escherichia coli and 6.0 mm for Staphylococcus aureus, but after 24 hr, no zone of inhibition was observed for both Escherichia coli and Staphylococcus aureus. This could be because, human serum has bacteriostatic effect on the organisms, hence the zone of inhibition observed after 12 hr. but the organism quickly overcame the bacteriostatic effect. This could be as a result of cell surface alterations that inhibit the activation or functioning of complements.