Methicillin-resistant Staphylococcus aureus bacteria, often referred to as MRSA, has become a significant infection problem both in hospitals and in the general community. It is a type of staph that is resistant to methicillin and other commonly used antibiotics in the same class, including penicillin, amoxicillin, and oxacillin. While MRSA is of concern to everyone, patients with a variety of primary immune deficiencies (PID) may be at increased risk.