Parenchymal infection of the mammary glands is a rare antepartum complication but is estimated to develop in up to a third of breast feeding women (Barbosa-Cesnik, 2003). Excluding breast engorgement, in our experiences, as well as that of Lee and associates (2010), the incidence of mastitis is much lower and probably approximates 3 percent. No evidence supports any of several prophylactic measures to prevent breast infection (Crepinsek, 2012). Risk factors include diiculties in nursing, cracked nipples, and oral antibiotic therapy (BranchElliman, 2012; Mediano, 2014). Symptoms of suppurative mastitis seldom appear before the end of the first week postpartum and, as a rule, not until the third or fourth week. Infection almost invariably is unilateral, and marked engorgement usually precedes inlammation. Symptoms include chills or actual rigors, which are soon followed by fever and tachycardia. Pain is severe, and the breast(s) becomes hard and red (Fig. 37-8). Approximately 10 percent of women with mastitis develop an abscess. Detection of fluctuation may be diicult, and sonography is usually diagnostic.
Staphylococcus au reus, especially MRSA, is the most commonly isolated organism in breast infections. Matheson and coworkers (1988) found it in 40 percent of women with mastitis. Other commonly isolated organisms are coagulase-negative staphylococci and viridans streptococci. The immediate source of organisms that cause mastitis is almost always the infant's nose and throat. Bacteria enter the breast through the nipple at fissures or small abrasions. he infecting organism can usually be cultured from milk. Toxic shock syndrome from mastitis caused by S aureus has been reported (Demey, 1989; Fujiwara, 2001).
FIGURE 37-8 Puerperal mastitis with breast abscess. A.Photograph shows indurated, erythematous skin overlying area of right breast infection. B. Sonographic picture of this 5-cm abscess. (Used with permission from Dr. Emily Adhikari.)
At times, suppurative mastitis reaches epidemic levels among nursing mothers. Such outbreaks most often coincide with the appearance of a new strain of antibiotic-resistant staphylococcus. A contemporaneous example is CA-MRSA, which has rapidly become the most commonly isolated staphylococcal species in some areas (Berens, 2010; Klevens, 2007). At Parkland Hospital from 2000 to 2004, Laibl and associates (2005) reported that a fourth of CA-MRSA isolates were from pregnant or postpartum women with puerperal mastitis. Hospital-acquired MRSA may cause mastitis when the newborn becomes colonized ater contact with nursery personnel who are colonized (Centers for Disease Control and Prevention, 2006). Staford and colleagues (2008) found a higher incidence of recurrent abscess in those with CA-MRSA-associated mastitis.
Provided that appropriate therapy for mastItiS is started before suppuration begins, the infection usually resolves within 48 hours. As discussed, abscess formation is more common with Saureus infection (Matheson, 1988). Most recommend that milk be expressed from the afected breast onto a swab and cultured before therapy is begun. Bacterial identification and antimicrobial sensitivities provide information mandatory for a successful program of nosocomial infection surveillance (Lee, 2010).