You might not know the name Staphylococcus aureus but you have probably heard of MRSA. Staphylococcus aureus is the bacterium and it is found in about one in every three people, mainly in the nose. Normally, it doesn't make you ill but if your resistance is low, it can cause an infection. The resistance of most patients in hospitals is very low. In addition, during their stay in hospital several procedures might be performed on them, which increase their chance of picking up a bacterium. For example, they might have surgery or have a catheter inserted. If a patient becomes infected by a bacterium while in hospital, we call it a hospital acquired infection, and there are two ways that this can happen. First, patients can be infected by bacteria from other patients, for example via the hands of health care workers, or by other people such as visitors. If the infection comes from another patient, this is called cross-infection. Second, patients can be infected by their own bacteria. Traditionally, the control of Staphylococcus aureus has been focused on preventing cross-infection between patients. However, it has been shown repeatedly that a large proportion of hospital acquired infections originate from the patient's own bacteria. Research has shown that having Staphylococcus aureus in their nose is a risk factor for subsequent infection in various groups of patients.
Intanasal antibiotic treatment with mupirocin ointment is often used to deal with this, by eradicating nasal Staphylococcus aureus. Trials have been done to look at whether this treatment does lead to fewer infections after surgery but, on their own, these did not provide a clear answer and we wondered if these studies might have looked at the wrong group of people, namely all patients. We wanted to focus on patients that were known to have Staphylococcus in their nose, because we think that these are the people who are at risk for getting a Staphylococcus aureus infection from their bacteria.  People who don't have this bacterium cannot infect themselves with it.
We did a literature search to find randomised trials that studied the effects of mupirocin nasal ointment on the number of Staphylococcus aureus infections. We wanted trials that had divided the patients into two treatment groups: those who would get treatment with mupirocin and those who would not be given this. In the last group, the “control” patients could receive a placebo or no treatment.
We identified nine eligible studies with a total of nearly 3400 participants, and we were able to pool the results of these studies in a meta-analysis to get an especially powerful statistical answer. If you are interested in the effect of mupirocin on time to infection, mortality, adverse events and number of infections caused by other micro-organisms than Staphylococcus aureus, you should definitely read the full review. But, in summary, we have found a real effect of mupirocin on the total number of Staphylococcus aureus infections, in a wide variety of patients. The number of people who got an infection was halved.
Up until now, although mupirocin is used for many patients, it is not routinely used in some hospitals. This is mainly because of concerns about the development of resistance to the antibiotic and the absence of convincing evidence that it really does reduce the infection rate. However, we have found that short-term use of intranasal mupirocin ointment does not seem to be associated with resistance, and that it does reduce infections. In our opinion, intranasal mupirocin should now be considered for use more widely, for patients who are known to be nasal carriers of Staphylococcus, who are in hospital for dialysis, surgery or other reasons.