In vitro properties of the newer quinolones

Table 5 summarizes the activity of the newer quinolones against various bacteria including intracellular bacteria and the other microorganisms. In this table, the overall MIC ranges of NFLX, ENX, OFLX, and CPFX, for susceptible isolates of each bacteria are schematically presented. The newer quinolones are considered to have sufficient activity against gram-negative enteric bacteria, N. gonorrhoeae, and H. influenzae and Legionella spp. Since OFLX and CPFX show only moderate activity against staphylococci, streptococci, and P. aeruginosa, improvement is expected. As shown in Table 3, TFLX and the recent investigational quinolones such as SPFX and KB-5246 show higher and promising activity against gram-positive bacteria. However, further studies are needed with longer periods to indicate whether these newer agents will be able to stop the increase of quinolone-resistant staphylococci. Furthermore, the activity of the newer quinolones against obligate anaerobes such as clostridia and bacteroides are considered to be insufficient for clinical use. Whether it will be possible to synthesize quinolones with anti-anaerobic activity sufficiently for clinical treatment is uncertain. Although Mycobacterium tuberculosis is susceptible to the newer quinolones, other mycobacteria are somewhat less susceptible to this class of agents. In addition, the newer quinolones have adequate activity against mycoplasma, chlamydia and rickettsia. From a microbiological viewpoint the prospects for the newer quinolones would be primarily to find agents that have higher anti-staphylococcal and anti-streptococcal activity. Secondly, agents possessing superior activity against obligate anaerobes such as Bacteroides spp. and Clostridium spp. are expected to synthesize. Furthermore, it may be possible to synthesize compounds that are sufficiently active for clinical use against atypical mycoplasma, chlamydia, and rickettsia.