Abstract
Skin infections caused by the USA300 clone of a highly virulent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) have recently increased. The surveillance of Panton-Valentine leukocidin (PVL)–positive strains and CA-MRSA was conducted among patients with cutaneous bacterial infections who visited dermatological institutions in Yokohama between November 2021 and October 2022 due to signs of an epidemic in Yokohama City. From 396 collected specimens, 245 S. aureus strains were isolated, of which 31.0% were MRSA; the isolation rate from patients with furuncles and carbuncles was high. Moreover, 59.2% of MRSA and 8.9% of methicillin-susceptible S. aureus cases were PVL-positive, and the proportion of patients with furuncles and carbuncles was particularly high. Genotyping of PVL-positive MRSA cases showed that the USA300 clone accounted for 3.3% and the ΨUSA300 clone, a mutation of the USA300 clone that appeared in Japan, comprised 36.7%. Furthermore, the ST22-PT clone, which produces both PVL and toxic shock syndrome toxin-1, which has spread rapidly in Japan in recent years, was detected in 20.0% of cases. The isolation rate of ST22-PT was significantly higher than that of the 2021 nationwide surveillance. (>4.4%; P<0.05) These results suggest that ST22-PT may be endemic in Yokohama City. The epidemic strain has replaced the conventional USA300 clone is being replaced by the ΨUSA300 clone and ST22-PT.
