How should a lactating mother with clinical mastitis be managed in the emergency department, including antibiotic selection and breastfeeding recommendations?

Mastitis Management in the Emergency Department

Antibiotic Selection and Breastfeeding Education

Continue breastfeeding on the affected breast while taking antibiotics—this is safe for the infant and essential for resolving mastitis. 1, 2

First-Line Antibiotic Therapy

Dicloxacillin 500 mg orally four times daily for 7 days is the preferred first-line agent, targeting methicillin-susceptible Staphylococcus aureus, which causes the majority of infectious mastitis cases. 1, 2

Cephalexin 500 mg orally four times daily for 7 days is an equally effective alternative, particularly useful for patients with non-severe penicillin allergy. 1, 2

• Both dicloxacillin and cephalexin are safe during breastfeeding with minimal transfer to breast milk. 2
• The usual treatment duration is 7 days, adjusted based on clinical response. 1

Alternative Antibiotics for Penicillin Allergy

For patients with true penicillin allergy, clindamycin 300-450 mg orally three times daily is appropriate, though it may increase gastrointestinal side effects in the infant. 1, 2

MRSA Coverage Indications

Consider MRSA-targeted therapy if: 2

• High local MRSA prevalence exists
• Patient has previous MRSA infection
• No clinical improvement within 48-72 hours of first-line beta-lactam therapy

For MRSA coverage:

• Clindamycin 300-450 mg orally three times daily (if isolate is clindamycin-susceptible) 1
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets orally twice daily plus a concurrent beta-lactam to cover Streptococcus species 1
  • Critical caveat: Avoid TMP-SMX in infants ≤28 days old, those with jaundice, prematurity, or G6PD deficiency due to risk of bilirubin displacement and hemolytic anemia. 2

Severe Cases Requiring Hospitalization

Admit patients with systemic symptoms suggesting sepsis risk, such as high fever, chills, or signs of systemic toxicity. 2, 3

Intravenous therapy for severe cases:

• Vancomycin 1 g IV every 12 hours (preferred for MRSA or severe infection) 1
• Cefazolin 1 g IV every 8 hours (for penicillin-allergic patients without anaphylaxis risk) 1
• Clindamycin 600 mg IV every 8 hours (alternative MRSA coverage) 1

Critical Patient Education on Breastfeeding

Mothers must continue breastfeeding or expressing milk from the affected breast during antibiotic treatment. 1, 2, 3

• All recommended antibiotics (dicloxacillin, cephalexin, clindamycin, amoxicillin/clavulanic acid, macrolides) are compatible with breastfeeding. 2
• Regular breast emptying through continued breastfeeding is essential for treatment and prevents worsening of mastitis. 2, 3
• Discontinuing breastfeeding risks breast engorgement, blocked ducts, and progression to abscess formation. 1
• Expressing and discarding breast milk is illogical and contraindicated—women after cesarean section breastfeed immediately despite similar drug exposure. 1

Follow-Up and Red Flags

Reevaluate within 48-72 hours if symptoms worsen or fail to improve to rule out abscess formation, which occurs in approximately 10% of mastitis cases. 1, 2

• Breast abscess requires drainage (surgical or needle aspiration), but breastfeeding can continue on the affected side as long as the infant's mouth does not contact purulent drainage. 3, 4
• Symptoms persisting beyond 1 week of appropriate antibiotics may indicate inflammatory breast cancer and warrant urgent evaluation with ultrasound and possible biopsy. 2

Special Pathogen Considerations

While S. aureus is most common, be aware that Streptococcus pyogenes can cause severe invasive mastitis, particularly if the infant or household contacts have recent streptococcal pharyngitis or scarlet fever. 5, 6