[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]
A New Local Variant (ST764) of the Globally-Disseminated ST5 Lineage of Hospital-Associated Methicillin-Resistant Staphylococcus aureus (MRSA), Carrying the Virulence Determinants of Community-Associated MRSA
Tomomi Takano, Wei-Chun Hung, Michiko Shibuya, Wataru Higuchi, Yasuhisa Iwao, Akihito Nishiyama, Ivan Reva, Olga E. Khokhlova, Shizuka Yabe, Kyoko Ozaki, Misao Takano and Tatsuo Yamamoto*
Author Affiliations: Division of Bacteriology, Department of Infectious Disease Control and International Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
The ST5 lineage of methicillin-resistant Staphylococcus aureus (MRSA) is one of the most globally-disseminated hospital-associated MRSA (HA-MRSA). We isolated a new local variant (designated ST764) over at least five years that causes invasive infections, including necrotizing fasciitis, and is carried by medical students as well as household members. Analysis of the genome sequence of one isolate, compared to that of the reference ST5 strain, revealed that ST764 had acquired virulence traits similar to those of community-associated MRSA (CA-MRSA) through the acquisition of two new mobile genetic elements, ACMEII and SaPInn54, which carried ACME-arcA and staphylococcal enterotoxin B gene (seb), respectively, and through enhanced expression of cytolytic peptide genes, although ST764 was negative for Panton-Valentine leukocidin. Other differences between ST764 and ST5 included the acquisition of ACMEII-related cassette (cJR1), prophage ϕ2NN54, and streptococcal Tn5251 and decreased copies of Tn554. For superantigen genes, although the two possessed seg, sei, sem, sen, and seo, ST764 lacked tst, sec, sel, and sep. The data suggest that ST764 MRSA is a novel hybrid variant of ST5 HA-MRSA with the characteristics of CA-MRSA, and the evolution of ST764 includes multiple steps, e.g. acquisition of novel or non-staphylococcal mobile elements.
*Corresponding author. Mailing address: Division of Bacteriology, Department of Infectious Disease Control and International Medicine, Niigata University Graduate School of Medical and Dental Sciences, 757 Ichibanchou, Asahimachidori, Niigata, Japan. Phone: (81) (25) 227-2050. Fax: (81) (25) 227-0762. E-mail: email@example.com
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