Challenges in the microbiological diagnosis and management of hVISA infections

To highlight the challenges involved in diagnosing and managing complicated heterogeneous vancomycin intermediate Staphylococcus aureus (hVISA) infections and to improve clinical recognition of such infections.

A retrospective review of patients with proven hVISA infections was undertaken in two major referral centres of North Queensland from 2006 to 2010. All isolates had population analysis profiling (PAP) done along with hVISA screening performed by the macro-Etest (MET).

Five patients were identified, two of whom died of hVISA-related sepsis. Their population analysis profiling-area-under-the-curve ratio (PAP-AUC) ranged between 0.96 and 1.43.

The identification of hVISA isolates in the diagnostic laboratory presents specific challenges. Clinical failure with vancomycin or MICs to vancomycin of ≥2 mg/L should alert the laboratory to proceed with the more specific methods of MET and PAP to identify hVISA or VISA isolates. Alternatives to vancomycin are limited and not always efficacious or tolerated.