Comparison of two commercial methods with PCR restriction fragment length polymorphism of the tuf gene in the identification of coagulase‐negative staphylococci

Abstract

Aims: Two commercial methods for the identification of coagulase‐negative staphylococci (CNS) were compared with the restriction fragment length polymorphism (RFLP) of the amplified tuf gene, which served as the reference method.

Methods and Results: One hundred and forty‐five CNS were evaluated using the API 32 Staph ID and the Crystal GP/ID BBL systems. The PCR‐RFLP of the tuf gene served as the reference method. The APIStaph and the GP/ID BBL had an overall rate of agreement with the molecular method of 58·6% and 46·2% respectively, with the inability of the GP/ID BBL to characterize 11·7% of the isolates. The APIStaph showed higher sensitivity and better agreement than the GP/ID BBL with the PCR‐RFLP, except for Staphylococcus hominis and Staphylococcus capitis.

Conclusions: Neither of the commercial systems was as reliable as the PCR‐RFLP method for identifying isolates of CNS. Overall the APIStaph had better agreement with the PCR‐RFLP than the GP/ID system.

Significance and Impact of the Study: The results indicate that the PCR‐RFLP method is more reliable than the two commercial systems tested, suggesting that it is more reliable for routinely identifying CNS.

APIStaph, coagulase‐negative staphylococci, Crystal GP/ID, identification, PCR restriction fragment length polymorphism