Invasive Staphylococcus aureus Infections in Hospitalized Infants

Invasive methicillin-susceptible Staphylococcus aureus (S aureus) infection (MSSA) caused more infections and more deaths in hospitalized infants than invasive methicillin-resistant S aureus infection (MRSA), which suggests measures to prevent S aureus infections should include MSSA in addition to MRSA, according to an article published online by JAMA Pediatrics.1
P. Brian Smith, M.D., M.P.H., M.H.S., of the Duke University School of Medicine, Durham, N.C., and coauthors compared demographics and mortality of infants with MRSA and MSSA at 348 neonatal intensive care units (NICUs) around the United States to determine the annual proportion of S aureus infections that were MRSA and to contrast the risk of death after invasive MRSA and MSSA infections.
The authors identified 3,888 of 887,910 infants (0.4 percent) with 3,978 invasive S aureus infections. Infections were more commonly caused by MSSA (2,868 of 3,978 or 72.1 percent) than MRSA (1,110 of 3,978 or 27.9 percent).
Overall, invasive S aureus infections had an incidence of 44.8 infections per 10,000 infants, according to the results. The annual incidence of invasive S aureus infection increased from 1997 through 2006 and then declined modestly from 2007 through 2012.
The study indicates invasive S aureus infections were more common in infants born at less than 1,500 grams (3,061 of 136,797 or 223.8 per 10,000 infants) than in infants born at 1,500 grams or higher (915 of 748,715 or 12.2 per 10,000 infants).
More infants with invasive MSSA infections (n=237) died before hospital discharge than infants with invasive MRSA infections (n=110). However, the proportions of infants who died after invasive MSSA and MRSA infections were similar at 237 of 2,474 (9.6 percent) and 110 of 926 (11.9 percent). The adjusted risk of death before hospital discharge and the risk of death at seven and 30 days after invasive infection were similar between infants with invasive MSSA infection and invasive MRSA infection, the results indicate.
“The absolute numbers of infections and deaths due to MSSA exceed those due to MRSA. Consideration should be given to expanding hospital infection control efforts targeting MRSA to include MSSA as well. Future studies to better define the relationship between MSSA colonization and subsequent infection will help to clarify the importance of such interventions for preventing MSSA disease,” the study concludes.
In a related editorial,2 Pablo J. Sanchez, M.D., of the Nationwide Children’s Hospital, Ohio State University, Columbus, and coauthors write: “In conclusion, the key to minimizing morbidity and mortality from any organism (S aureus included) must be prevention of horizontal transmission that can result in NICU outbreaks. We know that horizontal transmission occurs via the hands of health care workers, so hand hygiene as part of standard and transmission-based precautions remains the mainstay of prevention. Hand hygiene is cost-effective and easy to perform. … The common goal must remain prevention of transmission, and the most effective prevention strategy is already in our hands.”
1. JAMA Pediatr. Published online October 19, 2015. doi:10.1001/jamapediatrics.2015.2380.
2. JAMA Pediatr. Published online October 19, 2015. doi:10.1001/jamapediatrics.2015.2980.