AUTHOR=Lin Yu-Cheng , Lee Yu-Lin , Chen Yi-Hsin , Tsao Shih-Ming , Wang Wei-Yao 

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

JOURNAL=Frontiers in Medicine

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2024.1378207

DOI=10.3389/fmed.2024.1378207

ISSN=2296-858X

ABSTRACT=<sec id="sec1"><title>Objective</title><p>To outline the epidemiology of puerperal mastitis caused by methicillin-resistant <italic>Staphylococcus aureus</italic> (MRSA) and evaluate the effect of an infection control bundle on its incidence.</p></sec><sec id="sec2"><title>Methods</title><p>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 <italic>mec</italic> (SCC<italic>mec</italic>), gene encoding surface protein A (<italic>spa</italic>), accessory gene regulator (<italic>agr</italic>), and pulsed-field gel electrophoresis (PFGE). The phenotypic characteristics, including superantigen toxin profiles, gene encoding Panton-Valentine leucocidin (<italic>pvl</italic>), 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.</p></sec><sec id="sec3"><title>Results</title><p>The majority of cases occurred within 6 weeks post-delivery in first-time mothers. Of the 42 <italic>S. aureus</italic> 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-SCC<italic>mec</italic>V<sub>T</sub>-<italic>spa</italic> t437-<italic>agr</italic> group I with a vancomycin MIC of 1 mg/L, <italic>pvl</italic>-positive, and predominantly with a consistent toxin profile (<italic>seb</italic>-s<italic>elk</italic>-<italic>selr</italic>). 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.</p></sec><sec id="sec4"><title>Conclusion</title><p>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.</p></sec>