Intensive care unit patients are among the most ill patients in the hospital. Not only do they have a disease, but their immune system is compromised. Thus, they are unable to fight new infections. Among the most common bacterial infections are MRSA (methicillin-resistant staph aureus), Streptococcus and Pseudomonas. These infections require a strong and complex immune system to fight back. However, many ICU patients have their immune system weakened; either from multiple organs failing and/or from the medications (such as steroids, chemotherapy) that they are on. As a result, ICU patients are susceptible to bacterial infections.