First report on USA300 outbreak in a neonatal intensive care unit detected by polymerase chain reaction-based open reading frame typing in Japan

• Published in: Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy 2019-05, Vol.25 (5), p.400-403
• Main Authors: Uehara, Yuki, Mori, Miki, Tauchi, Mutsuhiro, Nishimura, Shu, Sakurai, Hiroki, Murai, Takemi, Okazaki, Kaoru, Kinoshita, Kazue, Horikoshi, Yuho, Hiramatsu, Keiichi
• Format: Article
• Language: English
• Subjects: Methicillin-resistant Staphylococcus aureus; Neonatal intensive care unit; Polymerase chain reaction-based open reading frame typing; USA300
• ISSN: 1341-321X; 1437-7780
• DOI: 10.1016/j.jiac.2018.12.002

Outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) in the neonatal intensive care unit (NICU) have been reported worldwide. Some outbreaks were caused by USA300, which is a community-associated MRSA clone. In 2011, polymerase chain reaction-based open reading frame typing (POT) for the initial MRSA isolates from all inpatients was started at the Tokyo Metropolitan Children's Medical Center. From March 2014 to April 2015, a total of 131 MRSA strains were isolated, 104 of which were analyzed as healthcare-associated MRSA. Thirteen stains (12.5%) had a POT number of 106-9-93, which strongly suggested USA300; these included 6 from nasal swabs, 6 from blood cultures and 1 from subcutaneous pus. All the MRSA strains were isolated from patients in the NICU; were typed as sequence type 8, spa type t008, and staphylococcal cassette chromosome type mec IVa; and possessed the lukS-lukF and arginine catabolic mobile element-arcA gene. Pulsed-field gel electrophoresis of all the strains, with USA300-0114 as a reference, showed indistinguishable banding pattern. Based on these results, POT was useful in recognizing this first MRSA outbreak of USA300 in a Japanese NICU and was advantageous in terms of swiftness, less cost and monitoring change of the epidemic MRSA lineage.