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Published on: May 8, 2013
The Prevalence and Determinants of Fusidic Acid Resistance Among Methicillin-Resistant Staphylococcus aureus Clinical
Huilin Zhao1, Xinyi Wang1, Bingjie Wang1
1Department of Clinical Laboratory, Shanghai Pulmonary Hospital, School of Medicine, Tongji University, Shanghai, China.
Abstract:
The significant increase in resistance of methicillin-resistant Staphylococcus aureus (MRSA) to fusidic acid (FA) is a worrying public concern. However, the data on the prevalence of FA-resistant MRSA isolates in China is still limited. This study aims to investigate the prevalence of FA resistance and resistance determinants among MRSA isolates from six tertiary hospitals in different regions of China between 2016 and 2020. The antimicrobial susceptibility of MRSA isolates was performed by disk diffusion test and broth microdilution method. Whole-genome sequencing was conducted to evaluate the determinants of FA resistance and molecular characterization of FA-resistant MRSA isolates. In this study, a total of 74 (74/457, 16.2%) isolates were identified to be FA-resistant among 457 non-duplicate MRSA isolates. The prevalence of 74 FA-resistant isolates was as follows: Hubei (28/70, 40%), Shanghai (18/84, 21.4%), Jiangxi (7/58, 12.1%), Inner Mongolia Autonomous Region (6/38, 15.8%), Guangdong (12/112, 10.7%), and Sichuan (3/95, 3.2%). The mutations in fusA were present in 79.7% (59/74) of FA-resistant MRSA isolates, with 54 (54/74, 73%) having L461K mutation and conferring high-level resistance [Minimum Inhibitory Concentration (MIC)>128 μg/ml]. Acquired gene, fusB, with low-level resistance (MIC <16 μg/ml) was found in 20.3% (15/74) FA-resistant MRSA isolates. ST5-MRSA-II-t2460 was the most prevalence clone with high-level resistance, accounting for 51.4% (38/74), which was distributed in Hubei (24/28, 85.7%), Inner Mongolia Autonomous Region (4/6, 66.7%), Shanghai (7/18, 38.9%), and Guangdong (3/12, 25%). ST630-t4549 MRSA isolates with low-level resistance were the most common in Jiangxi (3/7, 42.9%) and Sichuan (2/3, 66.7%). In brief, the prevalence of FA resistance among MRSA isolates in China was relatively high with geographic differences. High-level FA resistance was associated mostly with fusA mutations, especially the L461K mutation, whereas fusB usually conferred the low-level resistance to FA. The spread of ST5-MRSA-II-t2460 clone with high-level resistance to FA contributed greatly to the increase of FA-resistant MRSA isolates in most regions, especially in Hubei.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) shows increasing resistance to fusidic acid (FA) in China, with significant geographic variations. High-level FA resistance is linked to fusA mutations, while fusB confers low-level resistance.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Rising global concern over methicillin-resistant Staphylococcus aureus (MRSA) resistance to fusidic acid (FA).
- Limited data on FA-resistant MRSA prevalence in China necessitates urgent investigation.
Purpose of the Study:
- To determine the prevalence of FA resistance in MRSA isolates across China.
- To identify the genetic determinants and molecular characteristics of FA-resistant MRSA.
Main Methods:
- Antimicrobial susceptibility testing using disk diffusion and broth microdilution.
- Whole-genome sequencing for resistance determinant identification and molecular typing.
- Analysis of MRSA isolates from six tertiary hospitals (2016-2020).
Main Results:
- Overall prevalence of FA-resistant MRSA was 16.2% (74/457), with significant regional differences (Hubei 40%, Sichuan 3.2%).
- fusA mutations, particularly L461K, were found in 79.7% of resistant isolates, conferring high-level resistance.
- The ST5-MRSA-II-t2460 clone was the predominant high-resistance strain, especially in Hubei.
Conclusions:
- FA resistance in Chinese MRSA isolates is relatively high and geographically varied.
- fusA mutations (especially L461K) are key drivers of high-level FA resistance.
- The ST5-MRSA-II-t2460 clone significantly contributes to the spread of FA-resistant MRSA.
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