Oral Ciprofloxacin Therapy for Gram-negative Bacillary Osteomyelitis

Gram-negative osteomyelitis frequently responds poorly to conventional therapy. Ciprofloxacin displays excellent in vitro activity against gram-negative bacilli and offers the potential for outpatient therapy. In this ongoing study, ciprofloxacin therapy is being evaluated for the treatment of gram-negative osteomyelitis. Twenty-three patients (16 men and seven women) have been treated under the protocol (750 mg orally twice daily for 1.5 to six months), and 14 patients have completed therapy. All patients had either growth on bone cultures from an open or percutaneous biopsy, or an arthrocentesis to confirm the diagnosis. Involved sites included ankle or tibia (seven patients), vertebra (four patients), hip (five patients), metatarsal (four patients), phalanx (two patients), and metacarpal (one patient); 16 patients had chronic disease, and seven patients had acute disease. Patients had a total of 28 gram-negative bacilli, 12 gram-positive cocci, and one anaerobic gram-negative rod, for an average of 1.8 pathogens per patient. Eighteen of the 28 gram-negative bacilli were Pseudomonas species. The geometric mean minimal inhibitory concentration for all the gram-negative bacilli was 0.15 microgram/ml. The geometric mean minimal inhibitory concentration for the gram-positive isolates was 0.41 microgram/ml. All patients who completed therapy experienced a cure, with a mean follow-up of 6.1 months. Infections in all patients, except for two who are still taking ciprofloxacin, are resolving, both clinically and radiologically. One patient who was not eligible for the protocol experienced a superinfection with methicillin-resistant Staphylococcus aureus. Side effects have included urticaria, lethargy, nausea, and transient elevations of liver and renal function test results. Overall, ciprofloxacin therapy was well tolerated. This study suggests that ciprofloxacin holds promise for the outpatient treatment of gram-negative osteomyelitis.