NICUs Seeing More Antibiotic-Resistant Staph Infections

The rate of methicillin-resistant Staphylococcus aureus (MRSA) infections in U.S. neonatal intensive care units (NICUs) has more than tripled in recent years, reports a study in the July issue of the Pediatric Infectious Disease Journal.

The study highlights the need for redoubled efforts to follow routine infection control steps to prevent MRSA transmission to infants in NICUs, according to Dr. Fernanda C. Lessa and colleagues of the Centers for Disease Control and Prevention (CDC).

Using a national database on hospital-acquired infections, the researchers analyzed data voluntarily reported by NICUs from 1995 through 2004. The analysis focused on "late-onset" infections, developing more than three days after birth. The study included information on nearly 5.9 million patient-days in 149 NICUs.

Of approximately 4,400 staph infections tested for antibiotic resistance, 23 percent were MRSA. From 1995 to 2004, the rate of late-onset MRSA infections increased by 308 percent: from less than one to about three infections for every 10,000 hospital days. The sharpest increase in MRSA infections occurred after 2002.

The smallest infants—those with very low birth weights of 1,000 grams (about 35 ounces)—had the sharpest increase in MRSA infections. However, the infection rate rose in all birth weight groups.

The types of MRSA infections did not change during the study period. About 30 percent were bloodstream infections; other common MRSA infections included pneumonia and eye infections (conjunctivitis).

The rising rate of MRSA is a worldwide public health problem, with staph bacteria developing resistance to commonly used antibiotics. In recent years, MRSA has moved out of hospitals and healthcare settings to spread in the community. In the new study, however, the MRSA strains found in NICUs were more similar to the strains responsible for hospital-acquired infections, rather than those which spread in the community.

In newborns, infections occurring during the first three days of life are generally transmitted during labor and delivery. In contrast, the late-onset infections like the ones evaluated in the new study are more likely transmitted by parents, health care personnel, and other contacts.

The study—the largest to date of MRSA in NICUs—emphasizes the need to reinforce infection control measures shown to be effective in limiting the spread of MRSA (hand washing, etc.) among infants in the NICU. The researchers also call for further studies to explore potential sources and routes of transmission of MRSA infection to critically ill newborns.

The characteristics of MRSA infections among infants in the NICU "may be more complex than in other types of populations," Lessa and colleagues write. "Further strategies to prevent MRSA transmission among NICU patients may need to be developed."