In Vitro Activity of Chloroquine Phosphate on the Antibacterial Potency of Ciprofloxacin Hydrochloride on the Clinical Isolates of Some Gram-Negative Microorganisms

The in vitro activity of chloroquine on the antibacterial effect of ciprofloxacin on some Gram-negative organisms was investigated using the in vitro standardized method of the National Committee for Clinical Laboratory Standard (NCCLS). The study showed that three of the four strains of Pseudomonas aeruginosa (PA1, PA2, and PA4) and the strain of Klebsiella pneumoniae (KP) isolates were sensitive to ciprofloxacin hydrochloride alone as well as in combination with chloroquine phosphate. However a strain of Pseudomonas aeruginosa (PA3) was sensitive to ciprofloxacin hydrochloride alone, but the sensitivity to ciprofloxacin hydrochloride was lost in the presence of chloroquine even at the lowest concentration of 1μg/ml. The two strains of Escherichia coli used were not sensitive to ciprofloxacin alone and in combination with chloroquine. There were no significant pharmacodynamic interaction between chloroquine and ciprofloxacin on the PA1, PA4 and KP strains used in vitro (p>0.05). On the other hand, a significant enhancement of in vitro antibacterial activities of ciprofloxacin by chloroquine on the strain PA2 at the various concentrations was observed (p<0.05). The inhibition, enhancement or lack of effect of chloroquine phosphate on the ciprofloxacin hydrochloride observed in this study depends on the type and strain of microorganism involved.