Mycobacteria and the new quinolones

A review of the antimicrobial activity of the fluoroquinolones

The evolution of the fluoroquinolones is described, and structure-activity relationships outlined. The in-vitro antimicrobial activities of ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin against a wide range of organisms are critically reviewed. In-vitro factors influencing fluoroquinolone activity are discussed. Reports of the acquisition of resistance to the fluoroquinolones are evaluated. Finally, possible future directions for this group of antibiotics are discussed.

A case of resistant tuberculosis

We report a case of multiple drug-resistant pulmonary tuberculosis, in which treatment with two second line chemotherapy regimens was inadequate. Despite in-vitro sensitivity to ciprofloxacin the patient remained sputum positive with Mycobacterium tuberculosis after 11 months.

Intracellular bactericidal activity of ciprofloxacin and ofloxacin against Mycobacterium tuberculosis H37Rv multiplying in the J-774 macrophage cell line

Among new fluoroquinolone derivatives, the N-cyclopropylanalogs Ciprofloxacin (CIPRO) and ofloxacin (OFLO) have recently been found to have a high in vitro activity against a variety of mycobacteria (2). In this study, we have investigated their action against intracellularly growing Mycobacterium tuberculosis. For this purpose, the J-774 macrophage cell line was infected with the H37Rv type strain of M. tuberculosis, and drugs (at their serum level concentrations obtainable in healthy individuals (= 5 micrograms/ml; 8) were added after 2 days of intracellular growth of the bacteria. The bacterial growth during the experimentation was followed both electron microscopically and also by lysing the macrophages at various time intervals, and enumerating the bacterial viable counts after plating the lysate on appropriate media. Both drugs at the concentrations used did not affect macrophage viability (as assessed by trypan blue staining), and were highly bactericidal against the virulent tubercle bacilli multiplying in our J-774 macrophage model.

Effect of ofloxacin combined with Lactobacillus casei against Mycobacterium fortuitum infection induced in mice

Multiple injections of ofloxacin (subcutaneous or oral) in combination with a Lactobacillus casei preparation, LC9018 (subcutaneous), in mice infected intravenously with Mycobacterium fortuitum led to a marked delay in the incidence of spinning disease, a lowered incidence of gross renal lesions, and an increase in the rate of elimination of organisms from the kidneys. This indicates synergism in the therapeutic efficacy of the two agents. When the antimicrobial ability of peritoneal macrophages (M phi s) against M. fortuitum was measured in medium with or without ofloxacin, growth of the organisms was more markedly inhibited by ofloxacin in LC9018-induced M phi s than in normal M phi s. Synergism in the therapeutic activity of oxfloxacin plus LC9018 is assumed to be mediated in part by host M phi s, that is, functional stimulation of host M phi s by LC9018 treatment results in the synergistic effects of the two agents.

Urinary Mycobacterium fortuitum infection

Mycobacterium fortuitum, a common saprophyte usually found in water and soil, can also be isolated from sputum and gastric secretions of healthy carriers. Under certain conditions, significant clinical infections due to M. fortuitum do occur. Urinary tract infections are rarely caused by atypical mycobacteria. This report describes a urinary tract infection caused by M. fortuitum in a 73-year-old patient treated with corticosteroids for bronchial asthma, who was successfully treated with ofloxacin.

Influence of N substitution on antimycobacterial activity of ciprofloxacin

Ciprofloxacin analogs with various substitutions on the piperazine nitrogen were tested against several mycobacteria. In contrast to what has been found with other gram-positive and gram-negative bacteria, alkyl analogs such as N-isopropylciprofloxacin were shown to be significantly more active than ciprofloxacin. MICs of 0.125 microgram/ml against Mycobacterium tuberculosis were found.

Comparative in vitro activities of 20 fluoroquinolones against Mycobacterium leprae

The in vitro activities of 20 fluoroquinolones against Mycobacterium leprae were evaluated by using the BACTEC 460 system. M. leprae was incubated in BACTEC 12B medium at 33 degrees C under reduced oxygen for 2 to 3 weeks in the presence of fluoroquinolones at 0.31 to 5 micrograms/ml. Activity was determined by a reduction in 14CO2 evolution compared with that of drug-free controls. Of the commercially available agents, ofloxacin was most active, while enoxacin and norfloxacin were inactive. However, a number of newer fluoroquinolones (AT-4140, OPC-17100, OPC-17066, PD-117596, PD-124816, PD-127391, and WIN-57273), all containing a cyclopropyl group at R-1 and, with the exception of WIN-57273, either a halogen or methyl group at R-8, were more active than ofloxacin in vitro. Further in vivo evaluations of these agents should help determine their potential for use against leprosy.

Ofloxacin: a review

Ofloxacin is a new fluorinated quinolone antibiotic with a broad spectrum of activity against a variety of gram-positive and -negative bacteria including Enterobacteriaceae, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. In addition, ofloxacin has significant activity against Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycobacterium tuberculosis and this may give rise to new indications for the class of quinolone antibiotics. Clinical trials to date have demonstrated the efficacy of ofloxacin in the treatment of lower respiratory tract infections, urinary tract infections, and sexually transmitted diseases. Adverse effects to ofloxacin are usually mild and include gastrointestinal, central nervous system, and hypersensitivity reactions. Significant drug interactions with ofloxacin have not been reported.