Methicillin-resistant Staphylococcus aureus bacteremia in neonatal intensive care units: Genotyping analysis and case-control study

To assess the relatedness of methicillin-resistant Staphylococcus aureus (MRSA) isolates and to identify the risk factors for the acquisition of MRSA bacteremia in infants hospitalized in neonatal intensive care units (NICUs), 21 bloodstream isolates from 21 infants were genotyped and other 21 infants without MRSA bacteremia were matched for a case-control study. Two genotypes (A and C) were identified by pulsed-field gel eletrophoresis and three genotypes (I, II and III) by infrequent-restriction-site polymerase chain reaction. Genotype C-III in 9 isolates and genotype A-I in 7 isolates were the two most common genotypes. The presence of skin infection at onset, prolonged prior duration of central venous catheter indwelling and prolonged hospital stay were significantly associated with MRSA bacteremia in these infants. With multiple logistic regression analysis, the presence of skin infection at onset was the only significant risk factor of MRSA bacteremia, with an odds ratio of 20.8 (95% CI 2.95-145.4, p =.002). Conclusively, two major clones of MRSA prevailed in our NICUs, and the presence of skin infection at onset was the risk factor for the acquisition of MRSA bacteremia in these infants.