Journal Article

Emergence of New Strains of Methicillin-Resistant Staphylococcus aureus in a Neonatal Intensive Care Unit

Baker, Carol J., Hulten, Kristina G., Palazzi, Debra L., Campbell, Judith R., Healy, C. Mary

2004

Overview

Background. Genetically distinct strains of methicillin-resistant Staphylococcus aureus (MRSA) of community rather than hospital origin have emerged in many areas of the United States. We determined if MRSA strains causing bacteremia in infants treated from birth in a neonatal intensive care unit (NICU) demonstrated the genetic traits of community-associated MRSA. Methods. A retrospective cohort study was conducted among NICU infants with bacteremia due to MRSA during 2003 in a large tertiary care center NICU in Houston. MRSA isolates were characterized by antimicrobial susceptibility testing and staphylococcal cassette chromosome mec (SCCmec) typing by polymerase chain reaction. All MRSA cases were reviewed for clinical severity of infection and outcome. Results. During 2003, a total of 8 (47%) of 17 infants with bacteremia due to S. aureus had MRSA infection. Isolates from 6 (75%) of these 8 infants carried the SCCmec genes (class B mec and ccr2) that are characteristic of community MRSA; 4 isolates were type IVa. All 6 isolates were resistant to β-lactam antibiotics and erythromycin; 1 was also resistant to clindamycin. One isolate was nontypeable, and another carried the SCCmec type II gene (typical of hospital-associated strains) and was susceptible only to vancomycin. Seven (88%) of 8 infants presented in septic shock. Despite initial treatment with vancomycin, 3 (38%) died, and 3 survivors had complications requiring prolonged antimicrobial therapy; these 6 infants had MRSA isolates with genetic characteristics of isolates of community origin. Conclusions. Community-associated MRSA strains have emerged as a significant cause of sepsis in neonates hospitalized in NICU since birth and have caused disseminated infection with substantial morbidity and mortality.

• Publisher: The University of Chicago Press,University of Chicago Press
• Subject: Antibacterial agents / Antibiotics. Antiinfectious agents. Antiparasitic agents / Antimicrobials / Bacteremia / Bacteremia - epidemiology / Bacteremia - microbiology / Bacterial diseases / Bacterial sepsis / Biological and medical sciences / Cohort Studies / Human bacterial diseases / Humans / Infant, Newborn / Infants / Infections / Infectious diseases / Intensive Care Units, Neonatal / Major Articles / Medical genetics / Medical sciences / Methicillin Resistance / Methicillin resistant staphylococcus aureus / Neonatal intensive care / Neonatal intensive care units / Pharmacology. Drug treatments / Retrospective Studies / Sepsis / Staphylococcal Infections - epidemiology / Staphylococcal Infections - microbiology / Staphylococcal infections, streptococcal infections, pneumococcal infections / Staphylococcus aureus / Staphylococcus aureus - drug effects