Increase in SCCmec type IV strains affects trends in antibiograms of meticillin-resistant Staphylococcus aureus at a tertiary-care hospital

Abstract

The prevalence of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) strains has become a serious problem worldwide. The aim of this study was to investigate the annual transitions of MRSA strains with the CA-MRSA feature, which were identified as SCCmec type IV or V, in a hospital setting in Japan. Between 2005 and 2012, MRSA strains were collected from a tertiary-care hospital in Tokyo, Japan, and SCCmec typing, detection of the virulence factors and antimicrobial susceptibility testing were conducted. The rate of detection of type II SCCmec, which is found mainly in healthcare-associated MRSA, significantly decreased from 90.0 (2005)(2006) [2005][2006] to 2.1 % (2011-2012) (P,0.01). The resistance rates of cefotaxime, levofloxacin, clarithromycin and minocycline decreased every year. The resistance rates of these antimicrobial agents for the SCCmec type IV or V strains were significantly lower than those for the SCCmec type I or II strains (P,0.01, respectively). Therefore, these results suggest that the annual transitions of the virulence factors and antibiograms in MRSA are closely related to the increase of SCCmec type IV/V strains.

Clonal change of methicillin‐resistant Staphylococcus aureus isolated from patients with impetigo in Kagawa, Japan

“…All strains were cultured on tryptone soy agar (Oxoid, Hampshire, UK) under aerobic conditions at 35°C for 24 h. S. aureus was identified by Gram staining, proliferation on mannitol salt agar (Oxoid), production of coagulase (PS LATEX; Eiken Chemical, Tokyo, Japan) and detection of the nuc gene . MRSA isolates were identified using by polymerase chain reaction (PCR)‐based detection of the mecA gene …”

“…Polymerase chain reaction assays for the detection of mecA , ET genes ( eta , etb and etd ), SE genes ( sea , seb , sec , sed , see , seg , seh , sei and sej ), TSST‐1 gene ( tst ), PVL genes ( lukS/F‐PV ), ACME genes ( arcA and opp‐3C ), macrolide‐resistance genes ( ermA and ermC ) and aminoglycoside‐resistance gene ( aacA‐aphD ) were carried out as described previously . SCC mec typing was conducted as described elsewhere . Isolates not identified as SCC mec types I–V were classified as non‐typeable.…”

“…20 MRSA isolates were identified using by polymerase chain reaction (PCR)-based detection of the mecA gene. 8…”

“…In Japan, the main HA‐MRSA strains consist of SCC mec type II, whereas the main CA‐MRSA strains are SCC mec types IV or V . Nevertheless, SCC mec type IV strains have been increasing in prevalence in Japanese hospitals …”

“…4,5 In Japan, the main HA-MRSA strains consist of SCCmec type II, whereas the main CA-MRSA strains are SCCmec types IV or V. 6,7 Nevertheless, SCCmec type IV strains have been increasing in prevalence in Japanese hospitals. 3,8,9 In general, HA-MRSA strains manifest high-level resistance to multiple non-b-lactam antimicrobial agents such as quinolones, aminoglycosides and macrolides. 10 By contrast, CA-MRSA strains are usually susceptible to non-b-lactams but produce various virulence and colonization factors, such as ET, PVL and arginine catabolic mobile element (ACME).…”