Monday, October 13, 2014

Sour Milk: Antibiotic Coverage For a Breast Abscess

Clinical scenario:  

Your patient is a middle-aged female who was brought in from home for altered mental status.  As EMS is moving her over to the stretcher, they say: "this lady has some kind of infection on her breast ... I saw it when I went to do her EKG".  The patient is febrile to 39.3, tachycardic in the 120’s, but maintaining a blood pressure of 150’s/80’s.  She has a large, right- sided breast abscess with some spontaneous drainage.  Clearly, this patient has severe sepsis and she needs IVF, antibiotics, and source control.



Clinical Question:  

What is the most appropriate antibiotic choice for coverage of a breast abscess?  Obviously, the patient needs an I&D, but in the meantime, what typically is growing in there?  Should anaerobic coverage be routine?




The Literature:
There are several articles that address culture results from breast abscesses in the era of community acquired MRSA.  Here are two:
One article [1]  reports the culture results of 189 drained  breast abscesses from both lactating (LA) and non-lactating (NL) women at a single center from 2003-2006. In both cases, Staph aureus was the most commonly isolated organism (67.7% from LA, 30.5% from NL, and 42.6% of all cultures overall)  The majority of these S. aureus  isolates were MSSA not MRSA (39 vs. 3.7%).  Importantly, the second most commonly isolated class of bacteria were mixed anaerobes (13.7% overall), followed by anaerobic cocci (6.3% overall).  The authors, therefore strongly suggested that anaerobic coverage be a component of all initially empiric coverage for breast abscesses.
A second article [2] similarly tracked the culture results of 46 drained breast abscesses in a community setting. Staphylococcus aureus was  again the most common aerobic organism, present in 12 cultures (32%).  In contrast to the previous article,  58% of the S. aureus  isolates  were MRSA. The remaining positive cultures yielded Coag-negative Staph (16%), diphtheroids (16%), and Pseudomonas aeruginosa (8%).    This study was severely limited for estimating the prevalence of infection with anaerobic bacteria, as only 8/46 abscesses had swabs sent for anaerobic culture. Of these 2/8 (25%) grew anaerobes.

Take-home:

In addition to arranging for I&D, cover for at least Staph aureus (MRSA if you suspect it) and Anaerobes when treating breast abscesses.  

- If the person is sick and septic like our clinical scenario, cover broadly for MRSA, anaerobes and pseudomonas as well.  Possible options include:
               Inpatient - Vancomycin & Zosyn OR Vancomycin & Unasyn.
               Outpatient - Augmentin (if nursing) OR Bactrim/Flagyl if MRSA suspected. 

References:
[1] Dabbas, N., Chand, M., Pallett, A., Royle, G. T., & Sainsbury, R. (2010). Have the Organisms that Cause Breast Abscess Changed With Time?––Implications for Appropriate Antibiotic Usage in Primary and Secondary Care. The breast journal, 16(4), 412-415.
[2] Moazzez, A., Kelso, R. L., Towfigh, S., Sohn, H., Berne, T. V., & Mason, R. J. (2007). Breast abscess bacteriologic features in the era of community-acquired methicillin-resistant Staphylococcus aureus epidemics. Archives of Surgery, 142(9), 881-884.

Contributed by Maia Dorsett, PGY-3
Faculty Reviewed by Stephen Liang

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