The Interaction Between Gentamicin and Floroquinolones Against ESBL Producing Clinical Isolates of Escherichia coli

The present study evaluated the antimicrobial effect of different combinations of gentamicin and floroquinolones (ciprofloxacin, ofloxacin, perfloxacin and gatifloxacin) against extended spectrum beta lactamase (ESBL) positive E. coli isolates using checkerboard method. One hundred and four clinical isolates of E. coli obtained from urine (26), blood (24), stool (20), sputum (19) and semen (14) were investigated for ESBL production. Fifteen (14.4%) were positive for ESBL production in the following order 4(3.8%) from urine, 3(2.8%) from blood, 3(2.8%) from stool, 3(2.8%) from sputum and 2(1.9%) from semen. Five representative ESBL positive isolates, one from each specimen, were investigated for their susceptibility patterns to different gentamicin and floroquinolone combinations. The combinations of gentamicin and ciprofloxacin, perfloxacin and gatifloxacin, respectively at different ratios were predominantly synergistic in activity while gentamicin and ofloxacin combinations were primarily indifference in activity. These results may have some therapeutic significance in the management of ESBL infections especially in areas of the world where ESBL organisms are either emerging or re-emerging.