A method for the rapid detection of methicillin-sensitive and -resistant Staphylococcus aureus (MSSA and MRSA, respectively) and methicillin-resistant coagulase-negative staphylococci (MRCoNS) with a straightforward sample preparation protocol of blood cultures using an automated homogeneous polymerase chain reaction (PCR) assay, the GenomEra™ MRSA/SA (Abacus Diagnostica Oy, Turku, Finland), is presented. In total, 316 BacT/Alert (bioMérieux, Marcy l'Etoile, France) and 433 BACTEC (Becton Dickinson, Sparks, MD, USA) blood culture bottles were analyzed, including 725 positive cultures containing Gram-positive cocci in clusters (n = 419) and other Gram stain forms (n = 361), as well as 24 signal- and growth-negative bottles. Detection sensitivities for MSSA, MRSA, and MRCoNS were 99.4 % (158/159), 100.0 % (9/9), and 99.3 % (132/133), respectively. One false-positive MRSA result was detected from a non-staphylococci-containing bottle, yielding a specificity of 99.8 %. The lowest detectable amount of viable cells in the blood culture sample was 4 × 10(4) CFU/mL. The results were available within one hour after microbial growth detection and the two-step, time-resolved fluorometric (TRF) measurement mode employed by the GenomEra CDX™ instrument showed no interference from blood, charcoal, or culture media. The method described lacks all sample purification steps and allows reliable and simplified pathogen detection also in clinical microbiology laboratory settings without specialized molecular microbiology competence.

A new automated closed tube PCR assay, the GenomEra(™) MRSA/SA Diagnose (Abacus Diagnostica Oy, Finland) was evaluated for rapid confirmation of methicillin-resistant Staphylococcus aureus (MRSA) from cultured screening specimens. The ability of the assay to detect genotypically different MRSA strains was studied with a collection of 304 MRSA isolates covering 68 spa types. The specificity was investigated with a collection of 146 non-MRSA staphylococcus isolates. The usefulness of the assay for clinical purposes was assessed by a sequential combination of MRSA screening culture and confirmation of the colonies with the GenomEra MRSA/SA Diagnose assay. A total of 145 suspected MRSA colonies on chromogenic plates were analyzed this way. All MRSA isolates from the culture collection and from the clinical screening specimens were confirmed as MRSA with the GenomEra MRSA/SA Diagnose assay and none of the non-MRSA staphylococci caused false-positive results, which indicates both sensitivity and specificity of 100%. The combination of GenomEra MRSA/SA Diagnose with preceding culture on selective MRSA agar permitted MRSA confirmation within 24 h. This practice offers a reliable and quick detection of MRSA that is also suitable in areas where several strain types cause epidemics.