Objective To study the relationship between erythromyein sensitivity and ermB gene in 143 Ureaplasma urealyticum (Uu) clinical isolates. Methods We detected the minimum inhabit concen-trations (MICs) of Uu to erythromycin by broth dilution method and MIC≥8 μg/ml was used as standard concentration of resistance to erythromycin. Polymerase chain reaction was used to detect the ermB gene and biotype Uu with primers based on multi-band antigen gene. Results The MICs, MIC50 MIC90 of Uu to erythromycin were ≤0. 125 μg/ml to ≥128 μg/ml, 16 μg/ml, and ≥128 μg/ml, respectively, with a high resistance rate of 64.38%. ermB gene, which was mainly detected in Uu with MIC≥8 μg/ml, was positively detected in 40 out of 143 Uu strains (27.97%). No significant differences of the resistance to erythromycin and positive rate of ermB gene were found between the two biovars in the study . Conclusion ermB gene may probably be one of the important genes conferring resistance to erythromycin in Uu. Further studies are needed to discover the difference of resistance and mechanism of erythromycin between the two bi-ovars.

Objective To study the resistance mechanism of Ureaplasma urealyticum (Uu) to erythromycin.Methods The susceptibility of 73 clinical isolates of Uu to erythromycin was evaluated by using broth dilution techniques. PCR and DNA sequencing were carried out to screen hot spot mutations at the variable region of 23S ribosomal RNA in erythromycin-resistant strains of Uu. Moreover, erythromycin resistance methylase genes (ermA, ermB, ermC) and efflux pump genes (mefA/E, msrA/B, mreA) were screened by using PCR with specific primers. Results There were 35 (47.95%) resistant Uu strains out of the 73 isolates, and the minimal inhibitory concentration varied from 8 to 32 mg/L among these resistant strains. The ermB gene was detected in 19 (54.29%) resistant strains, and msrA/B gene in 9 (25.71%) resistant strains. Two resistant strains harbored both ermB gene and msrA/B gene. No mutation at 23S ribosomal RNA or amplification of resistance-associated genes was noted in sensitive or reference strains of Uu. Conclusion The ermB and msrA/B genes may be responsible for the erythromycin resistance of Uu.

Objective To detect the msr gene which confers resistance to erythromycin, and ana-lyze its distributing difference between the two biovars of Ureaplasma urealyticum. Methods Broth dilution method was used to determine the minimum inhibitory concentrations (MIC) to erythromycin among 72 U. urealyticum clinical isolates. The msrA, msrB, msrC and msrD genes detection and biotyping of U. urea-lyticum were conducted using PCR. Results The MICs of 72 U. urealyticum isolates to erythromycin ranged from ≤0. 125 μg/ml to ≥128 μg/ml. MIC_(50) was 32 μg/ml and MIC_(50) was ≥128 μg/ml. Biotyping showed that biovar Parvo had 51 strains (51/72, 70.83%) and biovar T960 had 21 (21/72, 29.17%) strains.The msrA, msrB, msrC and msrD genes were obtained in 1, 12, 0 and 24 strains, respectively, with five strains carrying the msrB and msrD genes, and one strain carrying the msrA, msrB and msrD genes. There was no resistance difference to erythromycin between the two biovars when the MIC≥8 μg/ml was considered resistance to eryt hromycin. But the msrB gene was predominantly detected in biovar T960. Conclusion U. urealyticum clinical isolates harbeur the msrA, msrB and msrD genes, and the predominantly detected msrB gene is of biovar T960.