Background: CoNS are common blood culture (BCx) contaminants resulting in unnecessary antibiotic therapy. Species reporting of CoNS is now possible in many medical centers due to new technology. When CoNS are isolated from multiple BCx, factors such as different susceptibility patterns and/or different species might suggest contamination. The purpose of this study is to characterize antibiotic usage attributable to CoNS positive BCx and to determine if reporting of CoNS species could help reduce unnecessary antibiotics.
Methods: Inpatients from Jan-June 2017 at our institution were screened retrospectively. During the study period, CoNS species were not reported (except S. lugdunensis). Patients (pts) ≥18 years old with ≥1 BCx positive for CoNS were included. Pts who were neutropenic, treated with staphylococcal antibiotics (SAbx) for a non-CoNS infection, or treated for CoNS with an antibiotic other than the defined SAbx were excluded. Pts were categorized into pre-defined groups: single positive BCx (Group 1), ≥2 positive BCx with different (Group 2) or same (Group 3) susceptibilities. A random sample of pts was screened until 50 Group 1 pts met study criteria. Additional data were collected on all remaining Group 2 and 3 pts in the study period, including species name obtained from lab database. The primary outcome was attributable use of SAbx among pts in each group. Additional analyses were performed to compare the use of SAbx among Groups 2 and 3.
Results: 102 pts were included. In the random sample (n=76), 34% had ≥2 positive BCx. S. epidermidis was isolated more frequently in Groups 2 & 3 than in Group 1 (69% vs 52%, p=0.03). 74% of pts received at least 1 SAbx (97% vancomycin). Attributable use of SAbx was greater among Groups 2 and 3 (p<0.001, Figure). Differing susceptibilities occurred in 24/52 (46%) patients but did not impact SAbx use (p=0.57 for DOTs, p=0.35 for DDDs). 17 (33%) of patients with ≥2 positive BCx had different species.
Conclusion: Significantly more SAbx were prescribed when ≥2 BCx were positive for CoNS. Since differences in susceptibilities has little effect, future studies should evaluate the impact of reporting CoNS species on appropriate antibiotic prescribing.
*P<0.001 for Group 1 vs 2 and Group 1 vs 3 (DOTs and DDDs). P=NS for Group 2 vs 3.
J. Beardsley, None
J. Johnson, None
C. Ohl, None
V. Luther, None
J. Williamson, None