Objects:

Methicillin-resistant Staphylococcus aureus (MRSA) has become an important nosocomial pathogen in our neonatal intensive care units (NICUs) and accounts for almost 100% of all S. aureus clinical isolates. To assess the relatedness of these MRSA strains, we conducted this molecular surveillance study.

Materials and methods:

During 1998 and 2000, a total of 125 MRSA clinical isolates, 10 isolates in 1998, 59 isolates in 1999 and 56 isolates in 2000, from 107 infants hospitalised in our NICUs were collected. Fifteen infants were with multiple isolates (two to four isolates). The sources of specimens included blood (75), pus (23), sputum (15), body fluids (3), and catheter tip (9). The genotyping method used was pulsed-field gel electrophoresis with Sma I digestion.

Results

A total of six genotypes with 23 type-subtypes were identified. Subtypes could be identified in genotypes A, C and D. There were two genotypes in 1998, five genotypes in 1999 and four genotypes in 2000. Seventy-seven isolates (61.6%) were shown to belong to a major type (Genotype A, 7 type-subtypes), while 43 isolates (34.4%) belonged to genotype C (11 type-subtypes). Both types could be identified in each year and were the two predominant clones in each year. The other four types were minor. Among the 15 infants with multiple isolates, the genotype was usually same if the isolates were from the same episode of MRSA infection, while the genotype was different if the isolates were from distinct episodes.

Conclusion:

There were two predominant MRSA clones prevailing in our NICUs between 1998 and 2000. Infection control measures should be implemented to try to control the spread of MRSA.