Original Articles
Early Access
https://doi.org/10.4081/ejtm.2025.14261
Antimicrobial resistance and virulence gene patterns of Staphylococcus aureus in infectious mastitis: implications for inflammatory myopathies of the lactating breast
Publisher's note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.
Received: 18 August 2025
Accepted: 1 September 2025
Published: 12 November 2025
Accepted: 1 September 2025
Published: 12 November 2025
532
Views
151
Downloads
With the present work, we aimed to investigate antimicrobial resistance and virulence gene patterns of Staphylococcus aureus in lactating patients with infectious mastitis and evaluate their potential impact on inflammatory myopathies of the lactating breast. Between January 2021 and April 2024, 158 lactating patients with culture-confirmed infectious mastitis were treated at Hangzhou Linping District Maternal and Child Health Hospital. Among these, 119 isolates were identified as S. aureus (82 MRSA, 37 MSSA). Antimicrobial susceptibility and virulence genes were analyzed. Muscle involvement was inferred indirectly from clinical presentation, including marked local induration, tenderness extending to deeper breast tissue, and reduced breast mobility. No imaging or biopsy was performed to confirm myopathic changes directly. S. aureus was the predominant pathogen. Both MRSA and MSSA showed high resistance to penicillin G, erythromycin, and Clindamycin, while all isolates were susceptible to nitrofurantoin, linezolid, vancomycin, and rifampicin. MRSA exhibited higher resistance than MSSA (p<0.05). Frequent resistance genes included aac(6’)/aph(2’’), blaZ, mecA, aph(3’)-III, and qacA/B. Virulence genes hla, clfA, clfB, and fnbA were common; pvl was less frequent in MRSA (p<0.05). MRSA infections were associated with stronger local inflammation and increased clinical markers possibly related to muscle involvement, raising the possibility of an association with myopathic changes in lactating breast tissue. S. aureus, particularly MRSA, is the main pathogen in lactating mastitis. Specific virulence genes may influence the severity of local inflammation and myopathic changes, highlighting implications for inflammatory myopathies in the lactating breast.
Downloads
Download data is not yet available.
1. Tobore TO. On maternal Post-Partum/Natal depression. A global underrecognized problem and the need for better treatment strategies. Psychiatry Res 2020;290:160-3. DOI: https://doi.org/10.1016/j.psychres.2020.113163
2. Rodriguez Z, Cabrera VE, Hogeveen H, et al. Economic impact of subclinical mastitis treatment in early lactation using intramammary nisin. J Dairy Sci 2024;107:4634-45. DOI: https://doi.org/10.3168/jds.2023-24311
3. Hussein Hany A, Fouad A, Mohammed T, et al. Study on prevalence and bacterial etiology of mastitis, and effects of subclinical mastitis and stage of lactation on SCC in dairy goats in Egypt. Trop Anim Health Pro 2020;52:46-9. DOI: https://doi.org/10.1007/s11250-020-02331-5
4. Mitchell KB, Johnson HM, Rodriguez JM, et al. Academy of Breastfeeding Medicine clinical protocol #36: the mastitis spectrum, revised 2022. Breastfeed Med 2022;17:360-76. DOI: https://doi.org/10.1089/bfm.2022.29207.kbm
5. Olga L, Vervoort J, Van Diepen JA, et al. Associations between breastmilk intake volume, macronutrient intake and infant growth in a longitudinal birth cohort: the Cambridge Baby Growth and Breastfeeding Study (CBGS-BF). Br J Nutr 2023;30:56-64. DOI: https://doi.org/10.1017/S0007114522003178
6. Rimoldi SG, Pileri P, Mazz I, et al. The role of Staphylococcus aureus in mastitis: a multidisciplinary working group experience. J Hum Lact 2020;36:503-9. DOI: https://doi.org/10.1177/0890334419876272
7. Li Y, Zhu F, Manna AC, et al. Gp05, a prophage-encoded virulence factor, contributes to persistent methicillin-resistant Staphylococcus aureus endovascular infection. Microb Spect 2023;11:39-42. DOI: https://doi.org/10.1128/spectrum.00600-23
8. Imanishi I, Nicolas A, Caetano ACB, et al. Author Correction: Exfoliative toxin E, a new Staphylococcus aureus virulence factor with host-specific activity. Sci Rep 2020;10:21-4. DOI: https://doi.org/10.1038/s41598-020-59360-1
9. Wang Q, Ning P, Ma XJ, et al. Chinese clinical guidelines for the diagnosis and treatment of lactational mastitis. Chinese J Breast Dis 2020;14:10-4.
10. Medical Administration of the Ministry of Health of the People's Republic of China. National Clinical Laboratory Procedures. 3rd ed. Nanjing: Southeast University Press, 2006:126-37.
11. Clinical and Laboratory Standards Institute (CLSI). Performance standards for antimicrobial susceptibility testing; Fifteenth informational supplement. CLSI document M100-S15. CLSI, 2005;25:1-167.
12. Lai BY, Yu BW, Chu A, et al. Risk factors for lactation mastitis in China: a systematic review and meta-analysis. PLoS One 2021;16:179-82. DOI: https://doi.org/10.1371/journal.pone.0251182
13. Aziz TA, Lafta IJ. Developing multiplex POR for the rapid and simultaneous detection of Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae associated with sheep respiratory tract infections. Biologia 2022;77:1415-21. DOI: https://doi.org/10.1007/s11756-022-01019-5
14. Surana K, Sagrule D, Lanjewar S, et al. Primary closure with suction drain of acute breast abscess after incision, drainage, and curettage. Indian J Surg 2020;82:129-33. DOI: https://doi.org/10.1007/s12262-019-01899-z
15. Chao YK, Yang YQ, Han B, et al. Fecal microbiome transplant from patients with lactation mastitis promotes mastitis in conventional lactating mice. Front Microbiol 2023;3:12-4. DOI: https://doi.org/10.3389/fmicb.2023.1123444
16. McDougall S, Clausen LM, Hussein HM, et al. Therapy of subclinical mastitis during lactation. Antibiotics 2022;11:3-7. DOI: https://doi.org/10.3390/antibiotics11020209
17. Yakovenko O, Yakovenko T, Akimov V, et al. Role of mini-invasive surgery in treatment of lactation mastitis. Surgical Practice 2021;3:73-6. DOI: https://doi.org/10.38181/2223-2427-2021-2-25-31
18. Wang LB, Yang L, Qu L, et al. Pathogen distribution and antibiotic resistance of acute lactational mastitis. Chinese J Maternal Child Health Res 2020;31:1030-4.
19. Zhu MH, Zhang YY, Zheng L, et al. Pathogen distribution and antibiotic resistance of pus specimens in lactational mastitis patients. Chinese J Health Laboratory Technol 2020;30:16-8.
20. Deepashree R, Khanum S, Sujatha SR, et al. Methicillin-Resistant Staphylococcus aureus (MRSA) carriage among healthcare personnel in non-outbreak settings in a tertiary care hospital in Mysore. Am J Infect Control 2021;49:1499-502. DOI: https://doi.org/10.1016/j.ajic.2021.06.013
21. Li Y, Ma XJ, He XP, et al. Clinical characteristics of lactational breast abscess caused by methicillin-resistant Staphylococcus aureus: a hospital-based study in China. Int Breastfeed J 2021;16:77-80. DOI: https://doi.org/10.1186/s13006-021-00429-6
22. Bojer MS, Frees D, Ingmer H, et al. SrrA in Staphylococci: an addition to the paradigm of membrane-localized, SOS-induced cell division inhibition in bacteria. Curr Genet 2020;66:495-9. DOI: https://doi.org/10.1007/s00294-019-01052-z
23. Da JY, Song Q, Shi JL, et al. Antimicrobial resistance and virulence gene detection of Staphylococcus aureus isolated from cows in Yinchuan. Progress Veterinary Med 2023;44:33-40.
24. Sobhy M, Ali SS, Khalil MA, et al. Exploring the potential of zinc oxide nanoparticles against pathogenic multidrug-resistant Staphylococcus aureus from ready-to-eat meat and its proposed mechanism. Food Control 2024;4:153-6. DOI: https://doi.org/10.1016/j.foodcont.2023.110117
25. Jia J, Ji YY, Gao S, et al. Investigation of virulence genes, agr typing, and biofilm formation of Staphylococcus aureus causing bloodstream infections. J Clin Lab 2023;41:117-22.
26. Olia AHG, Ghahremani M, Sharifi Y, et al. Comparison of biofilm production and virulence gene distribution among community- and hospital-acquired Staphylococcus aureus isolates from northwestern Iran. Infection 2020;62:957-61.
27. Crum NF. Bacterial pyomyositis in the United States. Am J Med 2004;117:420-8. DOI: https://doi.org/10.1016/j.amjmed.2004.03.031
28. Chiedozi LC. Pyomyositis: review of 205 cases in 112 patients. Am J Surgery 1979;137:255-9. DOI: https://doi.org/10.1016/0002-9610(79)90158-2
29. Touaitia R, Mairi A, Ibrahim NA, et al. Staphylococcus aureus: a review of the pathogenesis and virulence mechanisms. Antibiotics 2025;14:470. DOI: https://doi.org/10.3390/antibiotics14050470
30. Di Bella S, Marini B, Stroffolini G, et al. The virulence toolkit of Staphylococcus aureus: a comprehensive review of toxin diversity, molecular mechanisms, and clinical implications. Eur J Clin Microbiol Infect Dis 2025;44:1797816. DOI: https://doi.org/10.1007/s10096-025-05148-y
31. Lee AS, De Lencastre H, Garau J, et al. Methicillin-resistant Staphylococcus aureus. Nature Rev Dis Primers 2018;4:1-23. DOI: https://doi.org/10.1038/nrdp.2018.33
32. Cruz AR, Van Strijp JA, Bagnoli F, Manetti AG. Virulence gene expression of Staphylococcus aureus in human skin. Front Microbiol 2021;12:692023. DOI: https://doi.org/10.3389/fmicb.2021.692023
33. Radcliffe C, Gisriel S, Niu YS, et al. Pyomyositis and infectious myositis: a comprehensive, single-center retrospective study. Open Forum Infect Dis 2021;8:ofab098. DOI: https://doi.org/10.1093/ofid/ofab098
How to Cite
Antimicrobial resistance and virulence gene patterns of Staphylococcus aureus in infectious mastitis: implications for inflammatory myopathies of the lactating breast. (2025). European Journal of Translational Myology. https://doi.org/10.4081/ejtm.2025.14261
Copyright (c) 2025 the Author(s)
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
PAGEPress has chosen to apply the Creative Commons Attribution NonCommercial 4.0 International License (CC BY-NC 4.0) to all manuscripts to be published.