Abstract
Background
Daptomycin (dap) has been approved and successfully used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. However, reports of daptomycin nonsusceptible (DNS) MRSA strains have emerged over the recent years. This study describes the clinical characteristics of patients with DNS MRSA bloodstream infections (BSIs) with the objective of identifying risk factors and outcomes.
Methods
This is a retrospective case–control study in a tertiary healthcare system in southeast Michigan. Cases included 34 patients with DNS MRSA BSI between September 24, 2005 and March 31, 2018. Cases were matched with controls with MRSA BSI based on age, source of BSI, and time-period of BSI in a 1:1 ratio. Charts were reviewed for clinical and laboratory data. Vancomycin (van) and dap minimum inhibitory concentrations (MICs) were determined by E-test. DNS was defined as an MIC >1.0 µg/mL. Chi-square test, Fisher’s exact test, and t-test were used to determine statistical significance.
Results
In the case cohort, the source of BSI was endovascular in 11(32%) patients, central-line associated in 3(9%), secondary BSI in 13(38%), and unknown in 7(21%). Table 1 is a summary of the results.
Table 1. Clinical Characteristics and Outcomes of Cases and Controls
| Cases | Controls | ||
|---|---|---|---|
| N = 34(%) | N = 34(%) | P-value | |
| Mean age (SD) | 63.5 (12.0) | 61.9 (11.2) | 0.572 |
| Male | 18 (52.9) | 21 (61.8) | 0.462 |
| Mean bacteremia duration in days (SD) | 4.4 (3.2) | 5.9 (4.9) | 0.195 |
| Mean LOS in days (SD) | 19.5 (13.6) | 18.4 (14.6) | 0.751 |
| Mean van MIC (SD) | 2.04 (1.19) | 1.39 (0.36) | 0.003 |
| Mean dap MIC (SD) | 2.69 (1.32) | 0.57 (0.24) | <0.0001 |
| Epidemiologic acquisition | |||
| Community-acquired | 0 (0) | 9 (26.5) | 0.002 |
| Healthcare-associated | 21 (63.6) | 22 (64.7) | 0.927 |
| Hospital-acquired | 12 (36.4) | 3 (8.8) | 0.007 |
| 90-day prior dap exposure | 23 (82.1) | 3 (9.7) | <0.0001 |
| Mean dap exposure in days | 23.6 (21.0) | 2.68 (10.6) | <0.0001 |
| 90-day prior van exposure | 25 (89.3) | 9 (29) | <0.0001 |
| Mean van exposure in days | 13.0 (14.7) | 4.19 (12.7) | 0.020 |
| 30-day mortalitya | 10 (32.3) | 6 (18.8) | 0.218 |
| Mean Charlson Comorbidity Index (SD) | 5.7 (3.07) | 4.4 (2.9) | 0.077 |
| 90-day MRSA BSI recurrencea | 8 (44.4) | 2 (9.5) | 0.025 |
aFrom date of index BSI.
Conclusion
Prior exposure to dap and van, and higher van MIC in MRSA isolates are risk factors for DNS MRSA BSI. DNS is associated with significantly higher risk of 90-day MRSA BSI recurrence.
Disclosures
All authors: No reported disclosures.
Session: 137. Healthcare Epidemiology: MSSA, MRSA and Other Gram Positive Infections
Friday, October 5, 2018: 12:30 PM