Abstract：
OBJECTIVE: Staphylococcus aureus (S. aureus) spreads worldwide and occurrence of mastitis caused by it holds significant implications for public health. We aim to reveal the molecular typing, antibiotic resistance and virulence gene profile of S. aureus causing mastitis through investigation.
METHODS: A total of 200 isolates of S. aureus were collected from outpatients infected with mastitis in a hospital in Beijing from 2020.7 to 2021.7. The molecular characteristics were analyzed by MLST and spa typing, virulence genes were screened by PCR, antibiotic susceptible test was performed by VITEK® 2 Compact system and phylogenetic analysis was performed by MEGA11 and iTOL.
RESULTS: Nineteen sequence types (STs) belonging to 9 clone complexes (CCs) were identified. ST22 was the most dominant clone (77.0%, 154/200). MRSA accounted for 19.0% (38/200) and 89.5% (34/38) of MRSA isolates belonged to CC22 and CC59. The isolates had relatively low levels of antibiotic resistance, with the exception of β-lactams and macrolides with resistance rates above 50.0%. The carrying rate of pvl in the ST22-MRSA strains were 84.2% and the detection rates of seb and pvl in the MRSA isolates were significantly higher than those in the MSSA isolates, while the hlg, fnbA and sdrD showed opposite results. Whole genome sequenced specimens of MRSA strains X4 and B5 show the same evolutionary origin as ST22 EMRSA-15 (HE681097), which is popular in Europe.
CONCLUSIONS: The method based on molecular epidemiology is an important tool for tracking the spread of S. aureus infections. We need to be alert to the major MRSA clones CC22 and CC59 in the region and be vigilant to the possible pandemic and spread of ST22 EMRSA-15.
METHODS: A total of 200 isolates of S. aureus were collected from outpatients infected with mastitis in a hospital in Beijing from 2020.7 to 2021.7. The molecular characteristics were analyzed by MLST and spa typing, virulence genes were screened by PCR, antibiotic susceptible test was performed by VITEK® 2 Compact system and phylogenetic analysis was performed by MEGA11 and iTOL.
RESULTS: Nineteen sequence types (STs) belonging to 9 clone complexes (CCs) were identified. ST22 was the most dominant clone (77.0%, 154/200). MRSA accounted for 19.0% (38/200) and 89.5% (34/38) of MRSA isolates belonged to CC22 and CC59. The isolates had relatively low levels of antibiotic resistance, with the exception of β-lactams and macrolides with resistance rates above 50.0%. The carrying rate of pvl in the ST22-MRSA strains were 84.2% and the detection rates of seb and pvl in the MRSA isolates were significantly higher than those in the MSSA isolates, while the hlg, fnbA and sdrD showed opposite results. Whole genome sequenced specimens of MRSA strains X4 and B5 show the same evolutionary origin as ST22 EMRSA-15 (HE681097), which is popular in Europe.
CONCLUSIONS: The method based on molecular epidemiology is an important tool for tracking the spread of S. aureus infections. We need to be alert to the major MRSA clones CC22 and CC59 in the region and be vigilant to the possible pandemic and spread of ST22 EMRSA-15.
摘要：
目标：金黄色葡萄球菌（S.金黄色葡萄球菌）在全球范围内传播，由其引起的乳腺炎的发生对公共卫生具有重大影响。我们的目标是揭示分子分型，通过对引起乳腺炎的金黄色葡萄球菌的抗生素耐药性和毒力基因谱的调查。
方法：收集北京某医院2020.7-2021.7门诊感染乳腺炎的金黄色葡萄球菌200株。通过MLST和spa分型分析其分子特征,通过PCR筛选毒力基因，通过VITEK®2Compact系统进行抗生素敏感试验,并通过MEGA11和iTOL进行系统发育分析.
结果:鉴定了属于9个克隆复合物(CC)的19种序列类型(ST)。ST22是最主要的克隆(77.0%，154/200）。MRSA占分离株的19.0%(38/200)和89.5%(34/38)属于CC22和CC59。这些分离株的抗生素耐药性水平相对较低，除β-内酰胺类和大环内酯类耐药率高于50.0%外。ST22-MRSA菌株中pvl的携带率为84.2%,MRSA分离株中seb和pvl的检出率明显高于MSSA分离株,而hlg,fnbA和sdrD显示出相反的结果。MRSA菌株X4和B5的全基因组测序标本显示出与ST22EMRSA-15（HE681097）相同的进化起源，这在欧洲很受欢迎。
结论：基于分子流行病学的方法是追踪金黄色葡萄球菌感染传播的重要工具。我们需要警惕该地区主要的MRSA克隆CC22和CC59，并警惕ST22EMRSA-15可能的大流行和传播。
方法：收集北京某医院2020.7-2021.7门诊感染乳腺炎的金黄色葡萄球菌200株。通过MLST和spa分型分析其分子特征,通过PCR筛选毒力基因，通过VITEK®2Compact系统进行抗生素敏感试验,并通过MEGA11和iTOL进行系统发育分析.
结果:鉴定了属于9个克隆复合物(CC)的19种序列类型(ST)。ST22是最主要的克隆(77.0%，154/200）。MRSA占分离株的19.0%(38/200)和89.5%(34/38)属于CC22和CC59。这些分离株的抗生素耐药性水平相对较低，除β-内酰胺类和大环内酯类耐药率高于50.0%外。ST22-MRSA菌株中pvl的携带率为84.2%,MRSA分离株中seb和pvl的检出率明显高于MSSA分离株,而hlg,fnbA和sdrD显示出相反的结果。MRSA菌株X4和B5的全基因组测序标本显示出与ST22EMRSA-15（HE681097）相同的进化起源，这在欧洲很受欢迎。
结论：基于分子流行病学的方法是追踪金黄色葡萄球菌感染传播的重要工具。我们需要警惕该地区主要的MRSA克隆CC22和CC59，并警惕ST22EMRSA-15可能的大流行和传播。
