Identification of slide coagulase positive, tube coagulase negative Staphylococcus aureus by 16S ribosomal RNA gene sequencing

Aims-To ascertain the clinical importance of a strain of slide coagulase po sitive but tube coagulase negative staphylococcus species isolated from the blood culture of a 43 year old patient with refractory anaemia with excess ive blasts in transformation who had neutropenic fever. Methods-The isolate was investigated phenotypically by standard biochemical methods using conventional biochemical tests and two commercially availabl e systems, the Vitek (GPI) and API (Staph) systems. Genotypically, the 16S ribosomal RNA (rRNA) gene of the bacteria was amplified by the polymerase c hain reaction (PCR) and sequenced. The sequence of the PCR product was comp ared with known 16S rRNA gene sequences in the GenBank by multiple sequence alignment. Results-Conventional biochemical tests did not reveal a pattern resembling a known staphylococcus species. The Vitek system (GPI) showed that it was 9 4% S simulans and 3% S haemolyticus, whereas the API system (Staph) showed that it was 86.8% S aureus and 5.1% S warneri. 16S rRNA gene sequencing sho wed that there was a 0 base difference between the isolate and S aureus, 28 base difference between the isolate and S lugdunensis, 39 base difference between the isolate and S schleiferi, 21 base difference between the isolat e and S haemolyticus, 41 base difference between the isolate and S simulans , and 23 base difference between the isolate and S warneri, indicating that the isolate was a strain of S aureus. Vancomycin was subsequently prescrib ed and blood cultures taken four days after the start of treatment were neg ative. Conclusions-16S rRNA gene sequencing was useful in ascertaining the clinica l importance of the strain of slide coagulase positive but tube coagulase n egative staphylococcus species isolated from blood culture and allowing app ropriate management.