Cross-resistance of Three Macrolide Antibiotics against Ureaplasma urealyticum

Objective:To study the cross-resistance of erythromycin,josamycin and azithro- mycin against Ureaplasma urelyticum (Uu) in vitro.Methods:Multiple-proportional broth mi- crodilution method was applied to detect the MICs of drugs mentioned above against 35 clinically i- solated Uu strains at pH 6.5,cross-resistance was also analyzed.Results:The resistance rate, middle sensitivity rate,high sensitivity rate for erythromycin,azithromycin and josamycin were 71.43%/28.57%/0,2.86%/57.14%/40% and 0/94.29%/5.71%,respectively.There was only 1 strain with cross-resistance between erythromycin and azithromycin.No cross-resistance was found between erythromycin and josamycin.Among erythromycin resistant strains,17 of them had middle sensitivity to azithromycin and 25 to josamycin.Conclusion:Uu has a high resistance to erythromycin.Cross-resistance among erythromycin,azithromycin and josamycin was rare. The middle sensitivity rate to azithromycin and josamycin increase markedly among those resisting to erythromycin.