Abstract:

Objective To investigate the nasal carriage rate and molecular characteristics of Staphylococcus aureus(S. aureus) isolates among neonates in neonatal intensive care unit（NICU） of Beijing Children's Hospital. Methods Surveillance of nasal swabs from neonates were conducted in NICU of Beijing Children's Hospital from May to December of 2015.Bacterial culture was performed.Methicillin-resistant Staphylococcus aureus (MRSA) and Methillin-susceptible Staphylococcus aureus (MSSA) were identified by cefoxitin disc diffusion and detection of mecA.Isolates were analyzed by MLST,SCCmec,spa typing ,followed by detection of pvl，sasX and 21 toxin genes by PCR. Results Seventy-nine (18.4%) of 429 neonates had nasal carriage of S. Aureus. MRSA accounted for 27.8% .17 sequence types and 29 spa types were detected and the most frequent types were ST59（31.6%）and t189 （22.8%） respectively. The most common SCCmec type was Ⅳa （81.8%）among 22 MRSA strains. ST59-Ⅳa-t437(63.6%) and ST188-t189 (15.8%) were the most common clones of MSSA and MRSA, respectively. Of 79 isolates, seb-sek-seq(10.1%) was the most common virulence genotypes. seb、sek、seq and pvl gene were more associated with MRSA than with MSSA ,while sei gene was more associated with MSSA. Conclusion The nasal carriage rate of S. aureus was high among neonates in NICU of Beijing Children's Hospital. ST59-Ⅳa-t437 and ST188-t189 were the most common clones of MSSA and MRSA. The rate of toxin genes in carriage strains of S. aureus was high, and visible differences existed between MRSA and MSSA strains.