In Vitro Antibacterial Activities of Fluoroquinolones and Macrolides Against Ureaplasma urealyticumin

Objective To determine the susceptibilities of clinical Ureaplasma urealyticum(Uu)isolates to fluoroquinolones and macrolides,and to explore the effects of medium pH on MIC of macrolides against Uu in vitro.Methods Seven antimicrobial MICs against 72 strains of Uu,and MIC50 of four macrolides in pH at 6.0,6.5 and 6.9 were assessed by broth microdilution method.Results The resistant rates of 72 strains of Uu were:levofloxacin 4.2%,erythromycin 15.3%,roxithromycin 2.7%,while jatifloxacin,sparfloxacin,azithromycin,and josamycin showed no resistance to them.Among the seven agents,josamycin and sparfloxacin were the most active.When pH increased from 6.0 to 6.9,the MIC50 of erythromycin,roxithromycin,azithromycin and josamycin decreased significantly by 8,4,16 and 8 respectively.Conclusions The degree of resistance rate of Uu to levofloxacin,rythromycin and roxithromycin varied.New fluoroquinolones such as sparfloxacin and jatifloxacin show greater activity against Uu than levofloxacin;the 16-membered macrolides such as josamycin are more active against Uu than 15-membered macrolides(azithromycin) and 14-membered macrolides(erythromycin and roxithromycin).Moreover,the results suggest that the MICs of macrolides to Uu decrease significantly as the culture medium pH increases from 6.0 to 6.9.