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Objective To investigate the resistance of ureaplasma urealyticum (Uu) isolated from infertile patients to fluoroquinolones, and explore the correlation between quinolone resistance determining regions (QRDR) mutations in topoisomerase gene and antimicrobial resistance. Methods Clinical strains of ureaplasma isolated and cultured from the genitourinary tract of infertile patients who were admitted between December 2019 and January 2022 were collected, and validated by 16SrRNA sequencing. Two conserved genes, UU295 and UUR10_0588, were subsequently adopted to classify the strains into ureaplasma parvum (UPA) and ureaplasma urealyticum (UUR). In addition, the minimum inhibitory concentrations of ciprofloxacin, levofloxacin, sparfloxacin and moxifloxacin were determined by broth dilution method. The resistant strains were subsequently screened according to CLSI M43-A (2011 edition) standard, topoisomerase gene QRDR was amplified by PCR, and the sequencing results were analyzed using DNASTAR Lasergene. Finally, the homology models of parC S83L and gyrB R523E mutations were performed by Swiss-model homology modeling server. Results A total of 184 clinical strains were isolated, including 173 UPA (94.0%), 8 UUR (4.4%), and 3 of co-existing (1.6%). The resistance rates of the 3 groups to levofloxacin and moxifloxacin were UPA (80.4%, 2.2%), UUR (50%, 0), and UPA+UUR (66.7%, 33.3%), respectively. The incidence of QRDR amino acid variants was parC S83L (85.3%), gyrB R523E (11.4%), parC L127P (7.1%), gyrA L176F (2.2%), gyrA S174Q (1.6%), and parE L408I (1.1%), among which parE L408I is a newly discovered mutation. Homology modeling revealed that the parC S83L mutation interferes with the normal binding of quinolones by forming spatial hindrance, leading to fluoroquinolone resistance. Conclusion The resistance rate of Uu strains to fluoroquinolones in infertile patients is rather high, which is closely related to the amino acid variation caused by the mutation of topoisomerase gene parC S83L base. |
