MICROBIOLOGICAL ASSAY OF COLISTIN SULFATE ANTIBIOTIC IN PHARMACEUTICAL FORMULATIONS

Document Type : Original Article

Authors

1 Department of Microbiology and Immunology, Faculty of Medicine, Assiut University, Assiut 71526, Egypt

2 CID Company, Assiut, Egypt

Abstract

A simple, sensitive and specific agar cup diffusion bioassay for the antibacterial Colistin
sulfate was developed. Using a strain of Escherichia coli ATCC 8739 as the test organism,
Colistin sulfate at concentrations ranging from 100 to 1600 μg/ml could be measured in
pharmaceuticals. A prospective validation of the method showed that the method was linear
(r2= 0.999), precise (RSD< 2.8%) and accurate (percent recovery ranges between 98-102%).
The method shows that results confirm its precision, not differing significantly from the other
method described in the literature. We conclude that microbiological assay is satisfactory using
Escherichia coli ATCC 8739 for quantitation of in-vitro antibacterial activity of Colistin sulfate.