The emerging threat of methicillin-resistantStaphylococcus aureus(MRSA) clone ST22-PT, carrying both Panton–Valentine leucocidin and toxic shock syndrome toxin 1 genes

Abstract

Objectives Some MRSA strains produce Panton–Valentine leucocidin (PVL) and/or toxic shock syndrome toxin 1 (TSST-1), which are associated with severe infectious diseases. Although PVL- or TSST-1-positive strains have been isolated worldwide, strains carrying both PVL and TSST-1 genes are rare and sporadic. The objective of this study was to characterize these strains from Japan. Methods A total of 6433 MRSA strains isolated in Japan between 2015 and 2021 were analysed. Molecular epidemiological and comparative genomic analyses were conducted on PVL- and TSST-1-positive MRSA strains. Results A total of 26 strains from 12 healthcare facilities were PVL positive and TSST-1 positive, and all were classified as clonal complex (CC) 22. These strains exhibited similar genetic features to each other and were named as ST22-PT according to a previous report. Twelve and one of the ST22-PT strains were identified in patients with deep-seated skin infections and toxic shock syndrome-like symptoms, which are typical clinical features of PVL-positive and TSST-1-positive Staphylococcus aureus, respectively. Whole-genome comparative analysis revealed that the ST22-PT strains were highly similar to PVL- and TSST-1-positive CC22 strains isolated in several countries. Evaluation of the genome structure showed that ST22-PT possessed ΦSa2 harbouring PVL genes and a unique S. aureus pathogenicity island harbouring the TSST-1 gene. Conclusions ST22-PT strains have recently emerged from several healthcare facilities in Japan, and ST22-PT-like strains have been identified in several countries. Our report highlights that the risk of international spread of PVL- and TSST-1-positive MRSA clone ST22-PT needs to be further investigated.

The clinical characteristics and molecular epidemiology of methicillin‐resistant Staphylococcus aureus (MRSA) among very elderly people in Japan

“…According to this report, 46.2% of patients with the ST22-PT strain developed deep-seated skin infections, such as furuncles and skin abscesses, and 34.6% experienced recurrences. 25 In the present study, ST22-PT MRSA was detected in a male patient in his 40s with no underlying disease. The patient developed cellulitis of the buttocks, which was initially treated with MINO but recurred.…”

“…Because ST22-PT might be highly pathogenic and could cause invasive diseases, careful attention to the spread of this strain is required. 25 In total, 86 SCCmec type IV/CC1/sea+ MRSA strains were detected mainly in the sputum, skin, and soft tissues. However, only one of them was from blood cultures, and only three strains were determined to be the cause of infection and were treated with anti-MRSA drugs.…”

Whole genome sequencing of methicillin-resistant Staphylococcus aureus clinical isolates from Terengganu, Malaysia, indicates the predominance of the EMRSA-15 (ST22-SCCmec IV) clone

“…In addition, the lukED genes were not found in the ST22 isolates, which was consistent with a previous study 52 . Despite recent findings which described the emergence of hypervirulent ST22 strains carrying both PVL and tst genes 53 , 54 , the HSNZ ST22 isolates notably lacked these virulence factors. Interestingly, PVL- and TSST-1-positive ST22 strains were associated with SCC mec IVa 53 , 54 , whereas the HSNZ isolates belonged to the SCC mec IVh subtype, suggesting a genetic makeup distinctive from the hypervirulent strains despite their shared ST22 lineage.…”

“…Despite recent findings which described the emergence of hypervirulent ST22 strains carrying both PVL and tst genes 53 , 54 , the HSNZ ST22 isolates notably lacked these virulence factors. Interestingly, PVL- and TSST-1-positive ST22 strains were associated with SCC mec IVa 53 , 54 , whereas the HSNZ isolates belonged to the SCC mec IVh subtype, suggesting a genetic makeup distinctive from the hypervirulent strains despite their shared ST22 lineage. The PVL-encoded gene lukFS were identified only in the genomes of ST88 (SauR233), two ST772 (SauR37 and SauR68), and two ST1 (SauR127 and SauR209) isolates.…”

“…The ST22-SCC mec IV (EMRSA-15) clone was predominant in HSNZ ( n = 61/88; 69.3%), reflecting other studies done in Malaysia and Singapore in the past ten years 11 , 19 , 20 , 23 , 24 . Despite their relative susceptibility to antibiotics, the success of the ST22-SCC mec IV clone in displacing the more resistant ST239-SCC mec III clone warrants vigilance, particularly with the recent rise of hypervirulent ST22-SCC mec IV subclones that harbor the pvl and tst toxin genes in China and Japan 53 , 54 . The emergence of the Indian-origin clones ST772, and particularly ST672 in 2020 highlights their potential to spread and affirms the need for continuous monitoring by WGS.…”