Breast Abscess and Community-Acquired Resistant Staphylococcus aureus : Case Report and Literature Review

Introduction

Mastitis is a complication most often encountered in primiparous women and develops in 1%–24% of breastfeeding women. ¹ Breast abscesses develop as a complication of mastitis in 5%–11% of cases, generally in the first 12 weeks after birth or at the time of weaning. Most abscesses result from secondary bacterial infection from skin contamination; bacteria enter through a small skin laceration and proliferate in the stagnant lactiferous ducts.^1,2

Staphylococcus aureus is the most common pathogenic organism retrieved from breast abscesses; but there are other microorganisms (such as Staphylococcus epidermidis and Streptococcus pyogenes) and anaerobes (such as Peptostreptococcus and Bacteroides). ¹ Rarer breast infections have been reported secondary to mycobacteria, fungi, or parasite invasion. ³ A sterile culture with absent growth of bacteria has been reported in 21%–45% of samples, although these may have been false–negative findings from previous antibiotic treatments. ³

High-level resistance of S. aureus to β-lactams conferred by a mecA gene encoding a modified penicillin binding protein (PBP2a) was first observed in the early 1960s. Methicillin-resistant S. aureus (MRSA) has been responsible for both hospital acquired infections and, more recently, community acquired MRSA (CA-MRSA). A small number of human MRSA mastitis cases and outbreaks in maternity or neonatal units have been reported; these case are generally the result of CA-MRSA. ³ Toxic shock syndrome secondary to mastitis is seldom described. ⁴

Case

The patient was a 24-year-old, gravida 1, para 1, who had an uncomplicated spontaneous vaginal delivery 21 days prior to her first consultation regarding acute mastitis. She was exclusively breastfeeding and had presented at time afebrile with breast tenderness, mild redness on her right breast, and mastodynia. She was examined, diagnosed with mastitis, educated and instructed on good handwashing techniques and how to spot infection signs and symptoms of complications on her and on her newborn; and prescribed 500 mg of dicloxacillin every 6 hours for 10 days. After completing 2 days of therapy while continuing breastfeeding, she returned to because she was febrile (104.2°F), with chills, and increased mastalgia that was worsening. The presence of an abscess was noticed (Fig. 1). The patient was informed about the possibility of having CA-MRSA and transmitting it to her neonate through casual contact and through nursing. She was given options to continue nursing from her unaffected breast, to pump both breasts until the mastitis resolved, or to stop nursing altogether. The patient decided to stop nursing. She was then instructed to continue to pump both breasts on a weaning schedule to prevent engorgement. Her newborn's pediatrician was also notified.

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FIG. 1.

Breast abscess.

She was admitted to a hospital, started on intravenous therapy with vancomycin, at 1 g every 12 hours, in addition to appropriate analgesics. Incision and drainage were performed under local anesthesia and cultures were obtained. Her abscess cavity was approximately 4×4 cm. This patient was discharged the following day with instructions for wet-to-dry dressing changes, and she was given trimethoprim sulfamethoxazole to complete a 7-day course of antibiotics. Because of the proximity of the open wound to her nipple, she was instructed to pump and discard the milk in the affected breast, but was told she could nurse from the unaffected breast. The cultures subsequently revealed the presence of MRSA that was sensitive to the chosen antibiotics.

The patient returned 10 days later with complaints of worsening pain and induration in the same right breast but the problem was more medial and closer to the chest wall. An ultrasound was performed and a 5×3–cm abscess was detected. This was drained though two additional incisions under local anesthesia. The original wound was healing well and was closed primarily. Wound cultures from the new wounds were positive for MRSA and sensitive to trimethoprim sulfamethoxizole and levofloxacin. Oral levofloxacin was the chosen antibiotic for a 10-day course. The patient performed wet-to-dry dressing changes on the new wounds.

Results

This patient's mastitis finally resolved. Her newborn never showed any clinical signs of this infection and was not given any direct antibiotic treatment.

Discussion

The World Health Organization (WHO) recommends a continued breastfeeding technique for women with mastitis. The WHO advises ensuring proper neonate latching, frequent breastfeeding, and hand or pump milk expression for duct disengorgement, if necessary. ¹ Cessation of breastfeeding is necessary only when treatment with an antibiotic contraindicated for the newborn is prescribed (e.g., tetracycline, ciprofloxacin, or chloramphenicol) or if surgical drainage is performed. ¹ Good first-line antibiotic options include 500 mg of dicloxacillin, administered orally four times per day for 7–10 days. Alternatives are 300 mg of clindamycin administered four times per day for 7–10 days, 500 mg of erythromycin administered three times per day for 7–10 days, or 500 mg of cefazolin administered three times a day for 7–10 days. Some researchers suggest adding 500 mg of metronidazole administered three times per day for 7–10 days from the onset in the treatment of nonpuerperal abscesses.^1,2

Recurrent skin abscesses during pregnancy should prompt a rapid investigation for CA-MRSA. The most common site for a MRSA lesion in pregnancy is the extremities (44%), followed by the buttocks (25%), and breasts (mastitis) (23%). ³ Postoperative wound infection, cellulitis, and pustulosis have also been described ⁴ Comorbid conditions include human immunodeficiency virus and acquired immunodeficiency syndrome (13%), asthma (11%), and diabetes (9%). In comparison with the general obstetric population, patients with MRSA are more likely to be multiparous and to have had a cesarean delivery. ³

Infections caused by CA-MRSA are being increasingly observed in patients who do not have conventional risk factors. The route of transmission is usually not discovered: The results of surveillance cultures of samples obtained from employees of hospitals, hospital environments, and newborns are frequently negative for the outbreak strain. ⁴

All CA-MRSA cultured from breast abscesses are sensitive to clindamycin, trimethoprim-sulfamethoxazole, and linezolid, and 29% have been sensitive to levofloxacin. ² The bacteria could be sensitive to vancomycin and rifampin. Other antibiotics to which the isolates have been susceptible included gentamicin (98%) and levofloxacin (84%). ²

MRSA has become increasingly common in neonatal intensive care units and can lead to severe outcomes. Baby C, of a set of quadruplets, died of MRSA sepsis. The surviving siblings were colonized with MRSA. Expressed breast milk was fed to all infants; tested breast milk samples were all MRSA-positive. Pulsed field-gel electrophoresis results of isolates from the infants and breast milk were indistinguishable. ⁵

Conclusions

Recurrent skin abscesses during pregnancy should prompt a rapid investigation for CA-MRSA. Evaluating the current bacteriologic profile of breast abscesses is essential for determining the correct empirical antibiotic therapy and for minimizing breast-tissue damage.