Failure of phenotypic characteristics to distinguish between carrier and invasive isolates of Staphylococcus...

Thirty carrier and 29 invasive Staphylococcus epidermidis isolates were analysed for production of slime, extracellular enzymes and antibiotic resistance. Evaluation of slime production was by two methods which gave differing results, but both showed no difference between the two groups of isolates. Exoenzyme production by the two groups of isolates was also similar, and the only differences were shown in resistance to some antibiotics; carrier isolates were more resistant to novobiocin and cephalothin, but resistance to chloramphenicol, tunicamycin, teicoplanin, penicillin, ampicillin and tetracycline was similar in both groups. Cluster analysis based on exoenzyme production showed no consistent difference between invasive and carrier isolates, with the lowest similarity coefficient over 88% (except for one isolate). Consequently, none of the characteristics studied was useful in differentiating potentially invasive isolates.