An Unexpected Location of the Arginine Catabolic Mobile Element (ACME) in a USA300-Related MRSA Strain

Mette Damkjær Bartels,Lars Hestbjerg Hansen,Henrik Westh,Kit Boye,Søren J Sørensen,Michael Otto

doi:10.1371/journal.pone.0016193

Mette Damkjær Bartels, Lars Hestbjerg Hansen + Show 4 more

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https://doi.org/10.1371/journal.pone.0016193

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Journal: PloS one	Publication Date: Jan 25, 2011
Citations: 52	License type: CC BY 4.0

Affiliation: Hvidovre Hospital, University of Copenhagen

Abstract

In methicillin resistant Staphylococcus aureus (MRSA), the arginine catabolic mobile element (ACME) was initially described in USA300 (t008-ST8) where it is located downstream of the staphylococcal cassette chromosome mec (SCCmec). A common health-care associated MRSA in Copenhagen, Denmark (t024-ST8) is clonally related to USA300 and is frequently PCR positive for the ACME specific arcA-gene. This study is the first to describe an ACME element upstream of the SCCmec in MRSA. By traditional SCCmec typing schemes, the SCCmec of t024-ST8 strain M1 carries SCCmec IVa, but full sequencing of the cassette revealed that the entire J3 region had no homology to published SCCmec IVa. Within the J3 region of M1 was a 1705 bp sequence only similar to a sequence in S. haemolyticus strain JCSC1435 and 2941 bps with no homology found in GenBank. In addition to the usual direct repeats (DR) at each extremity of SCCmec, M1 had two new DR between the orfX gene and the J3 region of the SCCmec. The region between the orfX DR (DR1) and DR2 contained the ccrAB4 genes. An ACME II-like element was located between DR2 and DR3. The entire 26,468 bp sequence between DR1 and DR3 was highly similar to parts of the ACME composite island of S. epidermidis strain ATCC12228. Sequencing of an ACME negative t024-ST8 strain (M299) showed that DR1 and the sequence between DR1 and DR3 was missing. The finding of a mobile ACME II-like element inserted downstream of orfX and upstream of SCCmec indicates a novel recombination between staphylococcal species.

Highlights

The arginine catabolic mobile element (ACME) has been described in both coagulase negative staphylococci and methicillin resistant Staphylococcus aureus (MRSA)
The ACME II-like element of M1 was shorter than the ACME II described in S. epidermidis (Figure 2) M299 had no additional sequence between the orfX and staphylococcal cassette chromosome mec (SCCmec), but the SCCmec was identical to the M1 cassette and interestingly, it started with DR3 and not with the typical DR1 sequence (Figure 1)
The present study revealed recombination events in the J3 region of two MRSA SCCmec IVa and the presence of a sequence highly similar to the ACME composite island of S. epidermidis ATCC12228 in one isolate

Summary

Introduction

The arginine catabolic mobile element (ACME) has been described in both coagulase negative staphylococci and MRSA. In an attempt to study this phenomenon we discovered that PCR in the orfX region yielded no products by long range PCR and that the t024 isolates lacked the 2 kb downstream constant segment (dcs) [9] found in the J3 region of most SCCmec IV subtypes [10]. This suggested substantial changes in the J3 region and prompted us to sequence the entire genome of one ACME-positive and one ACME-negative t024 isolate. In this paper the SCCmec and the orfX near region of these two isolates are characterized

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Results

Conclusion