Staphylococcus aureus is a bacterium commonly found on the skin and in the nose of approximately one-third of the general population. While often existing without causing harm (colonization), it can cause a spectrum of infections. These infections range from minor skin issues, such as boils and abscesses, to severe, life-threatening conditions like pneumonia and sepsis. Because pregnancy alters the immune system and introduces unique risks to both the mother and the developing fetus, S. aureus infection requires prompt and careful medical management. Treatment decisions must balance eradicating the infection with ensuring the safety of the pregnancy.
Risks of Staphylococcus Aureus Infection During Pregnancy
An active S. aureus infection during gestation poses risks to the pregnant individual and the newborn. For the mother, infections commonly present as skin and soft tissue issues, including cellulitis or recurrent abscesses. More severe maternal complications include puerperal infections like chorioamnionitis and endometritis (infections of the placental membranes and uterine lining, respectively).
In the postpartum period, S. aureus frequently causes mastitis and breast abscesses, often complicating breastfeeding. Systemic infections, such as bacteremia or sepsis, are rare but carry a significant risk of severe illness and hospitalization. Untreated S. aureus infections pose a serious threat to the health of the pregnant individual and can lead to adverse fetal outcomes.
Concern increases when the infection involves Methicillin-resistant S. aureus (MRSA), a strain resistant to many common antibiotics, including penicillins. While the bacteria do not typically pass to the fetus in the womb, transmission to the baby during labor and delivery is possible. This can result in neonatal colonization or, less commonly, serious infection in the newborn.
Screening and Identifying S. aureus Infections
Confirming an S. aureus infection and determining its specific characteristics is required before treatment begins. Diagnosis starts by obtaining a sample from the suspected site, such as swabs from skin lesions, wounds, or a blood sample if a systemic infection is suspected. Swabs of the nasal passages and throat are also used to check for colonization, where the bacteria are present but not actively causing disease.
The collected sample is sent for laboratory culture to identify the bacteria. The laboratory then performs a sensitivity test to determine which antibiotics are effective against that specific strain. This testing distinguishes between Methicillin-Susceptible S. aureus (MSSA) and MRSA, which dictates the subsequent treatment plan.
Routine antenatal screening for S. aureus or MRSA colonization is not standard practice for all pregnant individuals. However, screening is often targeted for high-risk individuals, including those with a history of MRSA infection, diabetes, or women scheduled for an elective cesarean section. Identifying colonization in advance allows for decolonization treatment to minimize the risk of infection at delivery.
Safe and Effective Treatment Options During Gestation
The pharmacological management of S. aureus infection during pregnancy requires selecting antibiotics that are effective against the bacteria and safe for the developing fetus. Treatment depends on the infection’s severity, source, and whether the strain is MSSA or MRSA. For localized skin infections, simple drainage of an abscess may be the only intervention needed, often avoiding systemic antibiotics.
Treating MSSA Infections
When systemic medication is necessary for MSSA infections, penicillin derivatives are the preferred first-line treatment. Antibiotics such as dicloxacillin or oxacillin are commonly used due to their established safety during pregnancy. For those with a non-severe penicillin allergy, a cephalosporin like cephalexin is often a safe alternative.
Treating MRSA Infections
Treating MRSA is more challenging due to its resistance profile, but safe options exist for pregnant individuals. For non-severe MRSA infections, clindamycin is a common oral option, provided the strain is confirmed susceptible through laboratory testing. In cases of severe or invasive MRSA infection, the intravenous antibiotic vancomycin is the treatment of choice.
Antibiotic Safety Considerations
Antibiotic selection is guided by the Pregnancy and Lactation Labeling Rule (PLLR), which provides detailed information on fetal risk. Certain antibiotics are avoided during pregnancy due to potential harm to the fetus. For example, tetracyclines are contraindicated because they can affect fetal bone and tooth development.
Fluoroquinolones and trimethoprim-sulfamethoxazole are generally avoided, especially during specific trimesters, unless the potential benefit outweighs the known risks. Providers must weigh the risk of the untreated infection against the risk of the chosen medication. This careful assessment ensures the most appropriate antibiotic is used for the shortest necessary duration.
Non-systemic treatments are also used for localized issues or colonization. Topical antibiotics, such as mupirocin nasal ointment, are frequently used to treat nasal colonization. These treatments are often combined with an antiseptic body wash to reduce the bacterial load on the skin.
Preventing Infection and Managing Recurrence
Preventing the spread and recurrence of S. aureus infection relies on consistent hygiene practices and targeted decolonization when necessary.
Hygiene and Transmission Prevention
Simple measures help prevent transmission:
- Frequent hand washing with soap and water, especially after touching a wound or bandage.
- Keeping wounds, cuts, and scrapes clean and covered with dry, sterile bandages until healed.
- Not sharing personal items such as towels, washcloths, razors, and bedding.
- Washing linens and clothes that contacted an infected area separately in hot water and drying them completely.
Maintaining a clean home environment also reduces the chance of re-exposure, as S. aureus can survive on surfaces for extended periods.
Decolonization and Follow-Up
For individuals with recurrent S. aureus skin infections or colonization, a decolonization regimen is often implemented. This protocol typically involves a short course of intranasal mupirocin combined with bathing using an antiseptic cleanser. Since S. aureus often clusters within households, physicians may recommend decolonization for all household members to eliminate bacterial reservoirs and prevent reinfection.
Consistent communication with the healthcare team is important, especially if infections return or if signs of a new infection develop. Addressing recurring colonization or infection with a physician ensures the correct strategy is in place and that any new active infection is promptly treated.