SHORT TIME KILLING RATE OF COMBINATIONS OF SELECTED ANTIBIOTICS ON TWO STRAINS OF E. COLImn

Abstract

The killing kinetics of ciprofloxacin and gentamicin against Extended Spectrum β-lactamase (ESBL) positive and negative strains of E. coliwere investigated in the Pharmaceutical Microbiology laboratory, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Agulu Campus between March and May 2012. The minimum inhibitory concentrations (MICs) of the drugs were determined using the broth dilution method. The killing rate constant of each drug and their combinat ions was determined at double the MICs of the drugs singly and in combination using pour plate method. The result was that both antibiotics had activity on the two strains of the E. coli when used alone and better activity when used in combination. Also, gentamicin had equal activity on the two strains with the MIC of 3.125µg/ml, while ciprofloxacin had more effect on ATCC strain with MICs of 3.125µg/ml and 6.25µg/ml for ATCC and ESBLs strain respectively. The conclusion is that combining gentamicin and ciprofloxacin in ESBL cases have an advantage of faster microbial death over using each of the drugs alone especially in acute cases where rapid killing or eradication of the infecting organism is needed. Rapid bacterial eradication of pathogenic bacteria is a favourable characteristic of an antibiotic because it minimizes the spread of the disease with tremendous socio-economic impact.