Puerperal mastitis caused by limited community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clones

Yu-Cheng Lin; Yu-Lin Lee; Yi-Hsin Chen; Shih-Ming Tsao; Wei-Yao Wang

doi:10.3389/fmed.2024.1378207

Puerperal mastitis caused by limited community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clones

Front Med (Lausanne). 2024 Apr 19:11:1378207. doi: 10.3389/fmed.2024.1378207. eCollection 2024.

Authors

Yu-Cheng Lin¹, Yu-Lin Lee^{2

3}, Yi-Hsin Chen^{4

5

6}, Shih-Ming Tsao^{2

3}, Wei-Yao Wang^{2

3}

Affiliations

¹ Department of Internal Medicine, Show Chwan Memorial Hospital, Changhua, Taiwan.
² School of Medicine, Chung Shan Medical University, Taichung, Taiwan.
³ Department of Internal Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan.
⁴ Department of Nephrology, Taichung Tzu Chi Hospital, Taichung, Taiwan.
⁵ School of Medicine, Tzu Chi University, Hualien, Taiwan.
⁶ Department of Artificial Intelligence and Data Science, National Chung Hsing University, Taichung, Taiwan.

Abstract

Objective: To outline the epidemiology of puerperal mastitis caused by methicillin-resistant Staphylococcus aureus (MRSA) and evaluate the effect of an infection control bundle on its incidence.

Methods: A surge in MRSA puerperal mastitis was noted in a community hospital in September 2009. MRSA samples from mastitis cases and the environment underwent typing using multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec), gene encoding surface protein A (spa), accessory gene regulator (agr), and pulsed-field gel electrophoresis (PFGE). The phenotypic characteristics, including superantigen toxin profiles, gene encoding Panton-Valentine leucocidin (pvl), and minimal inhibitory concentration (MIC) against vancomycin, were ascertained. Subsequently, an infection control bundle emphasizing contact precautions was introduced, and mastitis incidence rates pre- and post-intervention were compared.

Results: The majority of cases occurred within 6 weeks post-delivery in first-time mothers. Of the 42 S. aureus isolates (27 from mastitis and 15 from colonized staff and environmental sources), 25 (92.6%) clinical and 3 (20%) colonized MRSA were identified as ST59-SCCmecV_T-spa t437-agr group I with a vancomycin MIC of 1 mg/L, pvl-positive, and predominantly with a consistent toxin profile (seb-selk-selr). PFGE revealed 13 patterns; pulsotype B exhibited clonal relatedness between two clinical and three colonized MRSA samples. Post-intervention, the incidence of both mastitis and MRSA mastitis notably decreased from 13.01 to 1.78 and from 3.70 to 0.99 episodes per 100 deliveries, respectively.

Conclusion: Distinct community-associated MRSA (CA-MRSA) clones were detected among puerperal mastitis patients and colonized staff. The outbreak was effectively controlled following the implementation of a targeted infection control bundle.

Keywords: CA-MRSA; MLST; PFGE; SCCmec; infection control bundle; puerperal mastitis.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This project was supported by Chung Shan Medical University (grant number: CSMU-TSMH-104-02). This funding source played no role in study design or conduction, data collection, analysis or interpretation, writing of the manuscript, or decision to submit it for publication.