Application of the antibiotic batumin for accurate and rapid identification of staphylococcal small colony variants

<p>Abstract</p> <p>Background</p> <p><it>Staphylococcus aureus</it> is a major human pathogen causing significant morbidity and mortality. The <it>S. aureus</it> colonies in osteomyelitis, in patients with cystic fibrosis and patients with endoprosthesis rejection frequently have an atypical morphology, i.e. staphylococcal small-colony variants, which form a naturally occurring subpopulation of clinically important staphylococci. Identification of these small colony variants is difficult, because of the loss of typical phenotypic characteristics of these variants.</p> <p>We wanted to improve and simplify the diagnosis of staphylococcal infection using a diagnostic preparation, consisting of 5 μg batumin paper disks. Batumin possesses a unique selective activity against all studied <it>Staphylococcus</it> spp., whereas all other species tested thus far are batumin resistant. We assessed the efficacy of the batumin diagnostic preparation to identify staphylococcal small colony variants, isolated from osteomyelitis patients.</p> <p>Findings</p> <p>With the batumin diagnostic preparation, all 30 tested staphylococcal small-colony variants had a growth inhibition zone around the disk of minimum 25 mm, accordant with the inhibition zones of the parent strains, isolated from the same patients.</p> <p>Conclusions</p> <p>The batumin diagnostic preparation correctly identified the small-colony variants of <it>S. aureus</it>, <it>S. haemolyticus</it> and <it>S. epidermidis</it> as belonging to the genus <it>Staphylococcus</it>, which differ profoundly from parental strains and are difficult to identify with standard methods. Identification of staphylococcal small-colony variants with the batumin diagnostic preparation is technically simple and can facilitate practical laboratory work.</p