Heteroresistant vancomycin-intermediate Staphylococcus aureus is associated to recurrent bacteraemia with the same strain

Abstract number: P1463

Daskalaki M., Rodriguez-Aranda A., Sanz F., Otero J.R., Chaves F.

Objectives: Recurrence of bacteraemia caused by Staphylococcus aureus appears despite administration of antibiotics active in vitro and can lead to increase in patient morbidity and mortality. The aim of study was to report the prevalence rate of recurrent bacteraemia due to S. aureus in our institution and to define the clinical and epidemiologic characteristics of relapse [isolates with the same Pulsed Field Gel Electrophoresis (PFGE) pattern] and reinfection (different PFGE pattern). Furthermore, to investigate whether relapse with S. aureus meticillin-resistant (MRSA) was associated with heteroresistance to vancomycin.

Patients and Methods: A retrospective study was conducted between Jan 2001 and Dec 2006. It included all patients who presented at least two episodes of S. aureus bacteraemia and recovered after a full course of antibiotic therapy of the first clinical episode. All isolates underwent a PFGE. A Etest macromethod (BHI agar with an inoculum of 2McF) was performed on the isolates of the first episode of MRSA bacteraemia and on the isolates of the control group of patients with no recurrence. MICleqslant R: less-than-or-eq, slant8 mg/L defined heteroresistance to vancomycin.

Results: During the study period, 883 patients had at least one episode of S. aureus bacteraemia. Forty three patients had a recurrence with 90 episodes. The recurrence rate was 5%. The PFGE method indicated that of the 45 episodes of recurrence, 34 (75.5%) were relapse and 11 (24.5%) reinfection. All reinfections were caused by S. aureus meticillin-susceptible (MSSA) whereas a 58.8% of relapses were caused by MRSA. According to the univariate analysis, MRSA bacteraemia was a risk factor for relapse (p < 0.001). Comparing MRSA relapses with the control group, we found that diabetes, haemodialysis and Etest macromethod with MICleqslant R: less-than-or-eq, slant8 mg/L to vancomycin, were associated with an increased risk of recurrence. From the multivariate logistic regression, only the Etest macromethod with a MIC geqslant R: gt-or-equal, slanted 8 mg/L to vancomycin was a predictor of recurrence (OR=4.4, CI 95% (1.03–19.3) p < 0.044.

Conclusions: MRSA is primarily associated with relapse whereas MSSA is more associated with reinfection. Diabetes and haemodialysis are risk factors for recurrent bacteraemia. Although we think that recurrent bacteraemia occurs as a result of multiple factors, heteroresistance to vancomycin seems to be a probable predictor of relapse. A result of MICleqslant R: less-than-or-eq, slant8 mg/L to vancomycin could keep us alarmed of heteroresistance and furthermore of a possible relapse.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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