Objective:To characterize the minimal inhibitory concentration (MIC) of macrolides against clinical Mycoplasma pneumoniae (MP) isolates and to investigate the significance of 23S rRNA mutations. Methods:Cross-sectional study.A total of 288 clinical MP strains preserved in the laboratory from 2016 to 2021 were taken for macrolide resistance gene testing and the evaluation of in vitro susceptibility to Azithromycin and Erythromycin.MIC 50 and MIC 90 values were calculated separately for macrolide-susceptible and -resistant strains. Results:All 288 MP strains underwent the test of in vitro susceptibility to Azithromycin, while 86 of them were additionally tested for Erythromycin.Among these strains, 22 strains were Azithromycin-sensitive, and 266 strains were Azithromycin-resistant.A2063G mutations were detected in 260 (97.7%) strains, while A2064G mutations were detected in 6 (2.3%) strains.Azithromycin-resistant strains had an MIC 50 of 128.000 μg/mL and an MIC 90 of 512.000 μg/mL, with the MIC ranging between 16.000 and 512.000 μg/mL.Seven strains were sensitive and 79 strains were resistant to Erythromycin.Among Erythromycin-resistant strains, A2063G mutations were detected in 73 (92.4%) strains, while A2064G mutations were detected in 6 (7.6%) strains.Erythromycin-resistant strains had an MIC 50 of 256.000 μg/mL and an MIC 90 of 512.000 μg/mL, with the MIC ranging between 64.000 and 1 024.000 μg/mL. Conclusions:A2063G and A2064G mutations in the 23S rRNA gene of MP are associated with high-level in vitro resistance to Azithromycin and Erythromycin, significantly limiting the clinical effectiveness of these antibiotics.Early resistance gene testing is recommended for suspected MP patients, which can help optimize the treatment, improve prognosis, and prevent resistance spread.

Objective:To characterize the minimal inhibitory concentration (MIC) of macrolides against clinical Mycoplasma pneumoniae (MP) isolates and to investigate the significance of 23S rRNA mutations. Methods:Cross-sectional study.A total of 288 clinical MP strains preserved in the laboratory from 2016 to 2021 were taken for macrolide resistance gene testing and the evaluation of in vitro susceptibility to Azithromycin and Erythromycin.MIC 50 and MIC 90 values were calculated separately for macrolide-susceptible and -resistant strains. Results:All 288 MP strains underwent the test of in vitro susceptibility to Azithromycin, while 86 of them were additionally tested for Erythromycin.Among these strains, 22 strains were Azithromycin-sensitive, and 266 strains were Azithromycin-resistant.A2063G mutations were detected in 260 (97.7%) strains, while A2064G mutations were detected in 6 (2.3%) strains.Azithromycin-resistant strains had an MIC 50 of 128.000 μg/mL and an MIC 90 of 512.000 μg/mL, with the MIC ranging between 16.000 and 512.000 μg/mL.Seven strains were sensitive and 79 strains were resistant to Erythromycin.Among Erythromycin-resistant strains, A2063G mutations were detected in 73 (92.4%) strains, while A2064G mutations were detected in 6 (7.6%) strains.Erythromycin-resistant strains had an MIC 50 of 256.000 μg/mL and an MIC 90 of 512.000 μg/mL, with the MIC ranging between 64.000 and 1 024.000 μg/mL. Conclusions:A2063G and A2064G mutations in the 23S rRNA gene of MP are associated with high-level in vitro resistance to Azithromycin and Erythromycin, significantly limiting the clinical effectiveness of these antibiotics.Early resistance gene testing is recommended for suspected MP patients, which can help optimize the treatment, improve prognosis, and prevent resistance spread.

Objective To investgate prevalence and clinical significance of antiproteinase 3(PR3)an- tibodies in Wegener's granulomatosis(WG)and other vasculitis patients.Methods One hundred and eleven systemic vasculitis patients with WG(9 cases,including 21 serums of tracking WG patients)and other systemic vasculitis(102 cases),403 secondnary vasculitis CTD(SLE 213 cases,RA 135 cases),nephritis 62 cases,30 healthy subjects were examined for anti-PR3 and anti-MPO antibody by enzyme-linked immunosorbent assay (ELISA)and ANCA by indirect immunofluorescence(IIF)was performed.Result Anti-PR3 positive were 23 in 588 serums of patients.The prevalence of anti-PR3 positive was WG(16/21,71.4 %),other systemic vas- culitis were not found anti-PR3,SLE(6/213,2.8%),RA(1/135,0.7%).In particular,the prevalence of anti- PR3 and cANCA with WG tended to be higher in the patients with other systemic and secondnary vasculitis (P＜0.05).The sensitivity and specificity of anti-PR3 for diagnosis of WG were 71.42% and 98.58%.The sensi- tivity and specificity of combination anti-PR3 and cANCA were 61.90% and 99.82%.Anti-PR3 and cANCA are associated with treament of WG.Conclusion Anti-PR3 antibody has high specificity for diagnosis of RA. Detection of anti-PR3 and cANCA at the same time can improve the specificity considerably.As sensitive markers of WG,anti-PR3 antibody may be useful for diagonosis and early treament.Anti-PR3 also may be useful for activity and relapse of WG.