Instability of characteristics amongst coagulase-negative staphylococci causing endocarditis

Centre National de RéAféAerence des Staphylocoques, FacultéA de MéAdecine Alexis Carrel * Centre d'Etudes et de Recherches BactéAriologiques, Institut Pasteur de Lyon, rue Guillaume Paradin, 69372 Lyon CéAdex 08; Laboratoire de Biologie Pulmonaire, Hospital Louis Pradel, 69394 Lyon CedéAx 3, France Received August 3, 1989 Accepted November 16, 1989 Variation in typing of clinically significant isolates of coagulase-negative staphylococci (CNS) was determined by five typing methods with 143 isolates obtained from 19 patients over periods from 2 days to 1 year. In only one case did all isolates give exactly the same typing pattern by all five tests. No single method, or simple combination, provided a ready means of confirming the relatedness of separate isolates. The most frequently useful tests were antibiotic susceptibility and extrachromosomal DNA banding patterns. However, the results of biotyping, serotyping and phage typing were also helpful in showing the relationship between different isolates from a given patient. In most cases a core pattern varying by the gain or loss of a small number of features, characterised a given patient's isolates. In two cases, apparently radical changes in the infecting organism were observed, and confirmed by restriction endonuclease analysis. Care should be taken when successive isolates of CNS show distinct typing differences in deciding their clinical relevance.