Vancomycin heteroresistance in Staphylococcus haemolyticus: elusive phenotype

Abstract

Aim: To determine the presence of vancomycin heteroresistance in Staphylococcus haemolyticus. Materials & methods: A total of 48 rifampicin-resistant S. haemolyticus isolates from bloodstream infections were included. Vancomycin heteroresistance was determined using the population analysis profile-area under curve (PAP-AUC) method. All the isolates were screened for the presence of mecA gene, mutations in the rpoB gene, staphylococcal cassette chromosome  mec and multilocus sequence types. Results: Fifteen isolates were identified as heteroresistant vancomycin-intermediate S. haemolyticus using PAP-AUC method. Dual rpoB mutations (D471E and I527M) contributed for the rifampicin resistance. The sequence types of heteroresistant vancomycin-intermediate S. haemolyticus were highly diverse. Conclusion: These findings illustrate the potential of  S. haemolyticus to develop heteroresistance, which emphasizes the need for routine surveillance of S. haemolyticus isolated from intensive care units for infection control practices.