Clinical Features of Heteroresistant Vancomycin-Intermediate Staphylococcus aureus Bacteremia versus Those of Methicillin-Resistant S. aureus Bacteremia

Background. Heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) infections are emerging, but their clinical significance remains unclear. Our objective was to compare patients who had hVISA bacteremia with patients who had methicillin-resistant S. aureus (MRSA) bacteremia. Methods. A total of 27 case patients with hVISA bacteremia were compared with 223 control patients with MRSA bacteremia. Medical records of all patients were reviewed, and factors independently associated with infection-related mortality were assessed by logistic regression. Results. Patients with hVISA bacteremia were not significantly different from those with MRSA bacteremia with respect to age, comorbidities, duration of hospital stay, and infection-attributable mortality. However, the median duration of bacteremia among patients with hVISA was significantly longer than that among patients with MRSA (12 vs. 2 days; P = .005), and patients with hVISA had a greater prevalence of complications, such as endocarditis (18.5% vs. 3.6%; P = .007) and osteomyelitis (25.9% vs. 7.2%, respectively; P = .006). Rifampin resistance emerged more frequently among hVISA isolates than among MRSA isolates (44% vs. 5.9%; P < .001). Factors independently associated with infection-related mortality in all patients were age, Charlson comorbidity index, female sex, and being bedridden. Conclusions. hVISA bacteremia was significantly associated with prolonged bacteremia duration, greater rates of complications, and emergence of rifampin resistance, compared with MRSA bacteremia. However, no significant difference in mortality existed between patients with hVISA bacteremia and those with MRSA bacteremia.