A recent study evaluated the effectiveness of the antibiotic mupirocin in preventing Staphylococcus aureus infections in babies admitted to neonatal intensive care units (NICUs).
Staphylococcus aureus (SA) is a species of bacteria described for the first time in the late 1800s and has been known as a threat to human health since then. These germs are commonly present on our skin and mucous membranes such as nose and throat. SA establishes itself on these body surfaces through a process called colonization. Colonization makes an individual more likely to develop an infection when the conditions for the germs become optimal. The presence of an open wound, for example, will favor the entrance of these bacteria in our body and cause disease.
The most common conditions caused by SA are skin and soft tissue infections. When SA infections become recurrent, there is a higher chance that the bacteria will reach areas of the body they normally do not have access to, such as the bloodstream. This condition is known as bacteremia and can lead to severe complications such as sepsis and endocarditis.
SA infections in NICU babies are a growing issue
Historically, the discovery and use of antibiotics proved to be effective against SA. It may seem surprising that SA infections are actually a growing source of concern in spite of the constant advances in patient care methods. These bacteria are highly adaptable. Over time, SA developed resistance to antibiotics commonly used in clinical practice such as methicillin. This problem is especially relevant in NICU babies.
Because the immune system of premature and very-low birth weight babies is not fully developed, these patients are at higher risk of infection. One challenge in controlling the diffusion of these bacteria is their ability to survive for a long time on environmental surfaces. Health care workers, family members and visitors that have been colonized by SA but do not develop any symptoms might also unknowingly spread these germs.
A five-day course of mupirocin successfully eliminated SA colonization
Mupirocin is an antibiotic used as part of a strategy to prevent SA infections NICU babies. Despite its use, little data is available to back up this type of treatment. A recent clinical trial evaluated the efficacy and safety of mupirocin in eliminating SA colonization from NICU babies. The results were published in the journal Pediatrics.
The researchers selected 155 babies for the study. All the participants were infants less than two years old with a positive record of colonization with SA, and with an anticipated stay in the intensive care unit of at least 14 days. The young patients were then randomly assigned to two groups. One group began a five-day course of mupirocin. The nursing staff applied the antibiotic in the form of a cream every eight hours to the nostrils and to the periumbilical and perianal regions. The other group did not receive treatment and served as control. This study did not include the use of a placebo because applying even simple oil ointments may increase the risk of infection in premature babies. The scientists evaluated the efficacy of the treatment by testing for the presence of SA after eight and 22 days from the start of the study.
The results showed that using mupirocin led to decolonization at day-8 in 94% of the treated NICU babies in comparison to 5% in the control group. After 22 days, 46% of the treated infants were still decolonized compared to only 2% of the control group. It also appeared that antibiotic treatment reduced the number of infections before day 22, but this result did not reach statistical significance to make claims of disease prevention.
No serious safety concerns regarding the topical antibiotic
In terms of safety, the scientists did not find any serious concerns. Rash was the only side effect that occurred more often in the treated group in comparison to the control group. Most episodes of rash were mild and did not lead to major complications. Resistance to mupirocin did not emerge from this study. At the same time, there was a slight increase in the number of patients colonized with mupirocin-resistant SA at the time of enrollment during the course of the study. These babies resulted colonized right after admission to the hospital. Whether they acquired the resistant bacteria as a result of clinical practices or from a different source is unknown.
One limitation of the study is due to its own design. The lack of a placebo meant that the nurses knew which patients received treatment and which ones did not. This notion could have introduced a bias when the same health care workers had to report events such as the emergence of a rash. The number of participants in this study was very low (155) compared to the number of pre-screened babies (1140). The small group size is a consequence of the very stringent requirements of the study design.
Supplemental strategies might reduce recolonization after mupirocin treatment
In conclusion, this clinical trial demonstrated that mupirocin is a safe and effective antibiotic treatment in obtaining SA decolonization in NICU babies. However, the scientists also observed that recolonization happened to many infants remaining hospitalized after two to three weeks. In light of these results, supplemental strategies should be considered to limit the persistent presence of SA in the environment and to reduce the risk of transmission from health care workers and family members.
Written by Raffaele Camasta, PhD
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