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During cefoxitin-based nasal screening, phenotypically categorized methicillin-resistant Staphylococcus aureus (MRSA) was isolated and tested negative for the presence of the mecA and mecC genes as well as for the SCCmec-orfX junction region. The isolate was found to carry a mecB gene previously described for Macrococcus caseolyticus but not for staphylococcal species. The gene is flanked by β-lactam regulatory genes similar to mecR, mecI, and blaZ and is part of an 84.6-kb multidrug-resistance plasmid that harbors genes encoding additional resistances to aminoglycosides (aacA-aphD, aphA, and aadK) as well as macrolides (ermB) and tetracyclines (tetS). This further plasmidborne β-lactam resistance mechanism harbors the putative risk of acceleration or reacceleration of MRSA spread, resulting in broad ineffectiveness of β-lactams as a main therapeutic application against staphylococcal infections.

We report the first known case of a device-related bloodstream infection involving Staphylococcus lugdunensis small-colony variants. Recurrent pacemaker-related bloodstream infection within a period of 10 months illustrates the poor clinical and microbiologic response even to prolonged antimicrobial drug therapy in a patient infected with this staphylococcal subpopulation.

To the Editor: Methicillin-resistant Staphylococcus aureus (MRSA) represents a major cause of hospital-, community- and livestock-acquired infections that are increasingly difficult to manage (1–3). Detection and identification of MRSA by culture and nucleic acid–based methods is challenged by heterogeneous penicillin-binding protein 2a (PBP2a) expression and variability of the staphylococcal cassette chromosome (SCCmec) elements. Recently, a new SCCmec element (XI) carried in bovine and human isolates was described (4,5). This SCCmec element contains a novel mecA homolog, designated mecALGA251, that is not detectable by usual mecA-specific PCR approaches and PBP2a agglutination tests. Garcia-Alvarez et al. reported this novel mecA homolog exhibited 70% identity at DNA level to the mecA gene, and suggested these strains were transmitted from livestock to humans (4).

To the Editor: Bacteria belonging to the former genus Micrococcus, the so-called micrococci, are usually regarded as contaminants from skin and mucous membranes. Nevertheless, micrococci have been reported as emerging pathogens in immunocompromised patients and have been described in severe infections (1–4). We describe what is, to our knowledge, the first case of prosthetic valve endocarditis caused by the newly described micrococcal species, Kytococcus schroeteri. Accurate identification of this species is of particular importance as kytococci—in contrast to other micrococcal species—are frequently resistant to penicillin and oxacillin (5).