Possible misinterpretation of penicillin susceptibility in Staphylococcus aureus blood isolate due to in vitro loss of the blaZ gene

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We describe a case of recurrent catheter-related blood stream infections (BSI) with Staphylococcusaureus, in which the first isolate tested susceptible to penicillin, while subsequent isolates were resistant. Phenotypic susceptibility correlated with the absence/presence of the blaZ gene. The in vitro stability of penicillin resistance was investigated by subculturing single colonies. In two out of five colonies, phenotypical resistance was lost after a single subculture, which correlated with loss of the blaZ gene. This in vitro phenomenon probably resulted in a very major error in the microbiology report of the first BSI, where penicillin had been recommended as treatment.

Original languageEnglish
JournalEuropean Journal of Clinical Microbiology and Infectious Diseases
Issue number1
Pages (from-to)163-167
Number of pages5
Publication statusPublished - 2022

Bibliographical note

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

    Research areas

  • blaZ, In vitro susceptibility testing, PSSA PRSA, Staphylococcus aureus

ID: 313705552