Disease relevance of msrA

• Minimal functional system required for expression of erythromycin resistance by msrA in Staphylococcus aureus RN4220 [1].
• Two genes, stpA and smpA, were identified upstream from msrA on the original Staphylococcus epidermidis plasmid, encoding an ATP-binding protein and a hydrophobic TM protein, respectively [2].
• The polymerase chain reaction (PCR) was used to study the prevalence of the macrolide resistance genes ermA, ermB, ermC, msrA/msrB, ereA and ereB, in 851 clinical isolates of Staphylococcus aureus and 75 clinical isolates of Enterococcus faecium that were erythromycin resistant [3].

High impact information on msrA

• Additional resistance elements in the VRSA isolate included a multiresistance gene cluster, ermB-aadE-sat4-aphA-3, msrA (macrolide efflux), and the bifunctional aminoglycoside resistance gene aac(6')-aph(2")-Ia [4].
• None of the 42 S. aureus isolates or 18 CNS isolates containing only msrA and none of the erythromycin-susceptible isolates yielded positive disk approximation tests [5].
• The requirement for two S. aureus candidate sequences, stpC and smpC, highly similar to sequences adjacent to msrA on the original S. epidermidis plasmid was investigated [1].
• S. aureus strains carrying a delta(stpC-smpC) mutation showed an identical ErR phenotype to those arising from single crossover events and unmutated RN4220 containing msrA [1].
• A gene similar to msrA was not present in the S. aureus chromosome [2].

Biological context of msrA

• Computer analysis from database sequences indicated at least three additional ORFs downstream of msrA [6].
• The msrA transcription start site was mapped 25 nt upstream of the msrA start codon [6].

Associations of msrA with chemical compounds

• Transcription of msrA was increased by oxacillin; but not by a variety of other stresses including H2O2 [6].
• In the present study, the S. aureus msrA gene was cloned, overexpressed, purified as His-tagged MsrA and shown to have methionine sulfoxide reductase activity [6].

Other interactions of msrA

• Increased transcription of the msrA and groEL genes in response to cell wall-active antibiotics was also demonstrated [7].

Analytical, diagnostic and therapeutic context of msrA

• Northern blot analysis revealed that the size of the msrA transcript was 2.3 kb, considerably larger than the 531 nt msrA ORF [6].
• METHODS AND RESULTS: We developed an oligonucleotide microarray containing seven oligonucleotide probes (oligoprobes) for each of the six genes (ermA, ermB, ermC, ereA, ereB and msrA/B) that account for more than 98% of MLS resistance in Staphylococcus aureus clinical isolates [8].

References