The In Vitro and In Vivo Activity of Ciprofloxacin
The third generation quinolones represent a new development and a possible alternative to the more conventional B-lactam and aminoglycosides for the management of difficult nosocomial infections. This study compared the in vitro and in vivo antibacterial activity of ciprofloxacin, a new fluroquinolone. The in vitro antibacterial activity of ciprofloxacin was compared with three quinolones, three aminoglycosides and three cephalosporins against 500 clinical isolates, including 100 gentamicin and 30 nalidixic acid resistant gram negative organisms. The latter were also tested against amifloxacin, ofloxacin and enoxacin. Minimum inhibitory concentration (MICs) were performed by agar dilution method using a final inoculum of 104 colony forming units (CFU)/ml. The results showed that ciprofloxacin was the most active drug against aerobic gram negative bacteria. Aminoglycoside and cephalosporin resistance did not affect the MIC 90, however resistance to nalidixic acid showed a four fold increase in MIC 90 of all the quinolones. The efficiency and safety of ciprofloxacin was determined in an open prospective study in 57 hospitalized patients with injections caused by multi-resistant gram-negative bacteria. A variable dosage was used, dependent on the site of infection. Clinical and bacteriological success occurred in 49 patients which included 12 bacteremias. Eight patients were classed as failures; although clinical improvement occurred, the organisms persisted to the end of therapy. Persistence was associated with presence of prostheses. Two patients had minor side effects. We conclude that ciprofloxacin has good in vitro and in vivo activity against a wide range of aerobes including multi-resistant gram negative bacteria.
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