Objectives
To review the clinical and microbiologic features of isolates among patients with puerperal mastitis requiring hospitalization.
Study Design
Between January 2000 and December 2008, postpartum patients who were hospitalized for mastitis were enrolled. The clinical characteristics, microbiologic results, management, and outcomes were reviewed.
Results
One hundred twenty-seven cases were enrolled . Seventy-six patients (59.9%) underwent incision and drainage for abscess drainage, all of whom discontinued breastfeeding. Staphylococcus aureus and coagulase-negative staphylococci were the most common isolates. Among 81 isolates of S aureus , 52 (64.2%) were resistant to oxacillin. Patients undergoing incision and drainage were more likely to discontinue breastfeeding, had a longer duration of symptoms, a longer hospitalization, a higher platelet count and higher rates of infection caused by S aureus and oxacillin-resistant S aureus .
Conclusion
Oxacillin-resistant S aureus has emerged in patients with puerperal mastitis during the past decade, and often necessitates incision and drainage, which results in discontinuation of breastfeeding.
Puerperal mastitis, an acute inflammation of the interlobular connective tissue within the mammary glands, frequently occurs among breastfeeding women, and potentially has a negative impact on continued breastfeeding. Up to 25% of parturients have experienced at least 1 episode of mastitis and 4-8.5% of parturients have had recurrent episodes of mastitis. Mastitis occurs most commonly during the first 3 months after delivery. Symptoms usually begin as malaise and fever, followed by erythema and tenderness in the affected breast. The triad of unilateral breast pain, erythema, and fever in a breastfeeding woman is a classic presentation, but variations exist. Supportive care, such as hot compresses, breast massage, a change in breastfeeding patterns, and a breast pump, are often advised. Few patients require inpatient treatment, most often because of refractory breast engorgement, persistent fever, or abscess formation. The incidence of puerperal mastitis requiring hospitalization and mastitis with abscess formation is 6.7 and 2.6 per 10,000 deliveries, respectively.
As with other soft tissue infections, mastitis is often caused by Staphylococcus aureus , coagulase-negative staphylococci (CNS) , Streptococcus species, and Escherichia coli . In the past, staphylococci were usually susceptible to oxacillin or methicillin; however, it has recently been reported that approximately 60% of staphylococci (nosocomial or community acquired) are resistant to oxacillin. A recent study on puerperal mastitis has shown oxacillin-resistant S aureus (ORSA) to be a primary pathogen, thus often necessitating surgical incision and drainage (I&D). The morbidity and adverse effects of surgical I&D on breastfeeding, however, have not been thoroughly evaluated.
The purpose of this study was to describe the presentation, management, and outcomes (including continued breastfeeding) of patients with puerperal mastitis requiring hospitalization during a 9-year period. We also reviewed the cultures of the specimens obtained from these patients to update the microbiologic profile and to elucidate the antimicrobial susceptibilities in the era of emerging bacterial resistance.
Materials and Methods
Between Jan. 1, 2000, and Dec. 31, 2008, parturients who were hospitalized for puerperal mastitis at a tertiary medical center in southern Taiwan were enrolled. Cases were identified based on a discharge diagnosis of mastitis and screened by a history of nursing or a recent delivery before admission. Mastitis was diagnosed by clinical presentation, such as unilateral breast tenderness and erythema, fever, or a palpable breast abscess. The demographic characteristics, clinical features, and microbiologic findings of specimens were recorded by chart review.
Cultures of milk and abscesses were collected with sterile dacron swabs. Blood cultures were obtained during a febrile episode. Specimens were transported and processed using standardized methods. The identification of microorganisms was based on the morphology of colonies and biochemistry reactions. Antimicrobial susceptibility was determined using disk diffusion methods, according to the description by the Clinical and Laboratory Standard Institute.
Data analysis was performed using the Statistical Package for the Social Sciences for Windows (SPSSWIN, version 13.0; SPSS, Inc, Chicago, IL). Continuous data, expressed as the mean ± standard deviation, were compared by the Student t test or Mann-Whitney U test. Categorical variables, expressed as numbers and percentages, were compared by the χ 2 or Fisher’s exact test. The level of statistical significance was set at .05.
Results
One hundred twenty-seven charts were available for review. There were 6 cases each year from 2000-2002, 11 in 2003, 16 in 2004, 13 in 2005, 26 in 2006, 22 in 2007, and 21 in 2008. The crude incidence increased from <0.5% in 2000 to >2.0% after 2006. The clinical features of the 127 cases are summarized in Table 1 . More than 90% of cases occurred during the first 3 months after delivery, with the highest occurrence during the second month after delivery (52 cases; 41.9%). Three patients had comorbidities; specifically, 1 patient had pneumonia during pregnancy and was hospitalized during the 28th gestational week, but recovered before delivery, 1 patient had idiopathic thrombocytopenia, and 1 patient had a history of systemic lupus erythematosus. Obstetric conditions or complications were recorded in 13 patients, including pregnancy-induced hypertension in 3 patients, postpartum hemorrhage in 2 patients, a twin pregnancy in 2 patients, preterm premature rupture of membranes in 2 patients, and placenta previa, antepartum hemorrhage, a cervical laceration, and a fourth-degree perineal laceration, each occurring in 1 patient.
| Characteristics | n | Range |
|---|---|---|
| Age, y | 29.2 ± 4.39 | (19–40) |
| Primiparas | 73 (64.6%) | |
| Duration of symptoms, d | 11.58 ± 18.94 | (1–30) |
| Highest temperature, °C | 38.14 ± 1.05 | (36.0–40.3) |
| Postpartum period, d (124 patients) | ||
| <30 | 31 (25.0%) | |
| 30-60 | 52 (41.9%) | |
| 69-90 | 29 (23.4%) | |
| 90-180 | 11 (8.9%) | |
| >180 | 1 (0.8%) | |
| Delivery method (79 cases) | ||
| Cesarean section | 23 (29.1%) | |
| Vaginal delivery | 56 (70.9%) | |
| Feeding methods (94 cases) | ||
| Direct feeding | 59 (62.7%) | |
| Pumping for bottle feeding | 14 (14.8%) | |
| Combined | 13 (13.8%) | |
| Weaning | 8 (8.5%) | |
| Intrapartum treatment with antimicrobials | 80 (63%) | |
| Discontinued breastfeeding | 93 (73.2%) | |
| Laboratory data | ||
| Leukocyte count (10 3 /μL) | 12.27 ± 4.75 | (4.2–5.2) |
| Bands, % | 4.99 ± 7.69 | (0–38) |
| Segments, % | 71.92 ± 13.40 | (31–94) |
| Platelet count (10 3 /μL) | 301.35 ± 106.97 | (14.5–544) |
| Hemoglobin, g/dL | 11.90 ± 1.36 | (7.5–15.4) |
| C-reactive protein, μg/mL | 64.63 ± 56.87 | (7–303) |
| Intervention | ||
| No surgical intervention | 47 (37.0%) | |
| Incision and drainage | 76 (59.9%) | |
| Aspiration | 4 (3.2%) | |
| Duration of hospitalization, d | 7.69 ± 6.04 | (1–34) |
Seventy-six patients (59.9%) underwent I&D for abscess drainage; all the patients discontinued breastfeeding. Four patients underwent needle aspiration and the remaining 47 patients received antimicrobial therapy only. Excluding the 4 patients who underwent needle aspiration, a comparison of the clinical characteristics between patients with and without I&D is summarized in Table 2 . Compared with patients who did not have an I&D, those who had an I&D had a longer duration of symptoms, a higher rate of discontinued breastfeeding, a lower peak body temperature, a higher platelet count, a higher rate of culture-proven S aureus and ORSA infection, and a longer hospitalization.
| Characteristics | No I&D (n=47) | I&D (n=76) | P value |
|---|---|---|---|
| Age, y | 29.12 ± 4.35 | 29.30 ± 4.69 | .833 |
| Parity (121 cases) | |||
| Primipara | 29 (61.7%) | 41 (54.0%) | .274 |
| Multipara | 16 (34.1%) | 35 (46.0%) | |
| Duration of symptoms, d | 2.90 ± 2.48 | 16.83 ± 22.73 | < .001 |
| Highest temperature, °C | 39.04 ± 0.68 | 37.68 ± 0.84 | < .001 |
| Postpartum period, d a | 44.56 ± 62.57 | 76.90 ± 82.41 | .037 |
| Delivery method (79 cases) | .625 | ||
| Cesarean section | 14 (32.6%) | 9 (25%) | |
| Vaginal delivery | 29 (67.5%) | 27 (75%) | |
| Feeding methods (94 cases) | |||
| Direct feeding | 16 (48.5%) | 43 (70.1%) | |
| Pumping then bottle feeding | 7 (21.2%) | 7 (11.5%) | |
| Combined | 9 (27.3%) | 10 (16.4%) | |
| Weaning | 1 (3.0%) | 1 (1.6%) | |
| Discontinued breastfeeding | 17 (60.3%) | 76 (100%) | < .001 |
| Intrapartum treatment with antimicrobials | 19 (40.4%) | 14 (18.4%) | .862 |
| Laboratory data | |||
| Leukocyte count (10 3 /μL) | 13.07 ± 24.65 | 12.00 ± 4.98 | .249 |
| Bands, % | 7.75 ± 9.42 | 3.35 ± 5.76 | .008 |
| Segments, % | 71.70 ± 18.39 | 70.95 ± 13.94 | .817 |
| C-reactive protein, μg/mL | 69.38 ± 60.03 | 59.28 ± 53.69 | .413 |
| Hemoglobin, g/dL | 14.86 ± 17.75 | 11.85 ± 1.19 | .315 |
| Platelet count (10 3 /μL) | 269.60 ± 89.18 | 316.29 ± 114.02 | .032 |
| Staphylococcus aureus | 19 (40.4%) | 61 (80.3%) | < .001 |
| Oxacillin-resistant S aureus | 10 (21.3%) | 42 (55.3%) | < .001 |
| Effective antimicrobials before admission | 15 (31.9%) | 22 (29.0%) | .161 |
| Effective antimicrobials after admission | 23 (48.9%) | 44 (57.9%) | .444 |
| Duration of hospitalization, d | 4.57 ± 1.90 | 9.94 ± 6.11 | < .001 |
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