Grand Rounds: When MRSA strikes your ob/gyn patient

Key Points

Staphylococcus aureus certainly is a busy little microbe. It is carried asymptomatically in 25% to 50% of the population, most commonly on the skin or in the nose; but it is also one of the most frequent causes of skin infections. While most people have no problems with these bacteria, when introduced through a cut or sore, the result can be painful furuncles, pneumonia, or even sepsis.¹

Methicillin-resistant staphylococcal aureus (MRSA) infection was first reported in the 1960s shortly after the introduction of methicillin.² Nosocomial or hospital-acquired MRSA (HA-MRSA) has been a well-known pathogen for over 40 years, affecting hospital patients and people in over-crowded conditions such as shelters or prisons (Table 1). Patients, healthcare workers, and the inanimate environment have all been shown to serve as asymptomatic carriers or reservoirs for HA-MRSA. Individuals may be colonized or harbor MRSA without manifesting signs of infection. The anterior nares is the areas of the body most frequently colonized with MRSA; other sites include the intact skin of the perineum, hands, infant umbilicus, and axilla, surgical wounds, decubitis ulcers, sputum, throat, urine, and IV catheters.

MRSA has also recently emerged as a common community-acquired pathogen. Risk factors associated with community-acquired MRSA (CA-MRSA) have included IV drug use, prior antibiotic use, and the presence of underlying diseases such as diabetes, malignancy, and chronic skin diseases.^1,3 But there are also reports of CA-MRSA infections in healthy patients without risk factors, with outbreaks in universities, schools, day-care centers, on a Naval ship, and among athletes on the same team and their contacts.^4-9

How does MRSA present?

HA-MRSA and CA-MRSA differ in clinical presentation. HA-MRSA is more common in older patients (30 vs. 70 years) and is typically reported in patients with burns, or after abdominal or vascular surgery.^11,12 The most common body sites involved are wounds, skin, and the bloodstream, as well as lower respiratory and urinary tracts. While there are no reviews of gynecologic surgically-associated MRSA, there is a case report of HA-MRSA described after a laparoscopic supracervical hysterectomy.¹³ The patient presented 40 days after her surgery with a vaginal discharge and was found to have lesions of the vaginal mucosa close to the cervix and one on the cervix that were culture positive for MRSA. The patient was treated successfully with topical mupirocin.

Mupirocin is unique because its mechanism of action is thought to involve the inhibition of bacterial protein and RNA synthesis. It has excellent gram-positive activity against Staphylococcus and Streptococcus. The drug is available as an ointment in a water-miscible base with polyethylene glycol (PEG) as the vehicle; however, while it's used topically, it is not recommended for prolonged use in extensive, large, open wounds because that may expose patients to toxic amounts of PEG.¹⁴