摘要
Summary
Subpopulations of bacteria present several challenges to the clinician and the clinical laboratory. With S. aureus SCVs, the first challenge is finding and correctly identifying them as S. aureus. Next, the susceptibility testing must be done by agar dilution or by broth MIC methods because the slow growth of the organisms will not allow accurate susceptibility testing by disk diffusion or automated methods. Care must be given to conduct the susceptibility testing with medium that has low levels of thymidine and menadione. The laboratory should be particularly alert for S. aureus SCVs when samples come from patients that have received long term therapy or when the infection disease has been unusually persistent, antibiotic resistant, or recurrent. However, the host milieu can select for S. aureus SCVs which means that patients may have these variants even when they have received no antibiotic therapy. The presence of subpopulations of bacteria that are able to persist within host cells also re-emphasizes that MICs have major limitations in predicting efficacy of a drug. Finally, when these variant bacteria are established in stationary phase and adherent to surfaces, they are exceptionally resistant to antibiotics.
