Staphylococcus aureus Bacteremia: Description of a Previously Undescribed Clinical Entity">
117. The "Skip Phenomenon" in Blood Culture Positivity in Patients with Staphylococcus aureus Bacteremia: Description of a Previously Undescribed Clinical Entity
Session: Oral Abstract Session: Coming Soon to a Bloodstream Near You
Thursday, October 27, 2016: 11:15 AM
Room: 275-277
Background: Staphylococcus aureus bacteremia (SAB) has mortality rates of 20-40%. The most recent IDSA guidelines state that a single set of negative blood cultures is sufficient to demonstrate clearance of SAB. However, anecdotal experiences in which SAB cleared and then recurred, despite appropriate antibiotics, suggested that S. aureus might exhibit fluctuating blood culture positivity, something that has heretofore not been described in the literature, which we have labeled as the “skip phenomenon” (SP). Our objectives were to determine the prevalence of SP in a cohort of inpatients with SAB and to determine whether certain clinical characteristics were associated with the phenomenon.

Methods: We performed a nested case-control study, using a previous cohort of 804 adult inpatients at Mayo Clinic between July, 2006 and June, 2011 with ≥3 days of SAB. Blood culture data was reviewed for all patients, with SP defined as ≥1 day of negative blood cultures following documented SAB and preceding recurrence of SAB. Each case of SAB with SP was matched to 2 to 4 controls based on age, gender, and duration of bacteremia (DB). The association of clinical characteristics (including preexisting diseases, implanted devices, bacterial susceptibility, and treatment regimen) with SP was analyzed via conditional logistic regression.

Results: Of the 804 patients in the SAB cohort, 29 (4%) had SP. Remarkably, 26 (90%) patients were male. The median age was 69.4 years (interquartile range [IQR] 58.7 to 80.3). Despite an attempt to match for DB, there was a statistically longer duration in patients with SP as compared to the controls, (median [IQR], 10 [7-12] days, vs 8 [6-10] days; P=0.015). Accordingly, DB was adjusted for in the regression models. Notably, 26 (90%) patients in the SP group were on chronic immunosuppression, as compared to 69 (79%) patients in the control, though no significant difference was found between the SP and control groups for this (P=0.427), or any other clinical characteristic included in the logistic regression.

Conclusion: This is the first study to describe the SP. Though pathogenesis is not defined, predominance of older males with immunosuppression is remarkable and prompts consideration of a practice change to obtain serial negative blood cultures to insure SAB clearance in this subpopulation.

Justin Fiala, MD, Internal Medicine, Mayo Clinic, Rochester, MN, Bharath Raj Palraj, MBBS, Department of Medicine, Division of Infectious Diseases, Mayo Clinic, Rochester, MN, Muhammad R. Sohail, MD, FIDSA, 200 First Street SW, Mayo School of Graduate Medical Education, Rochester, MN, Brian Lahr, MS, Biomedical Statistics and Informatics, Mayo Clinic, College of Medicine, Rochester, MN and Larry M. Baddour, MD, FIDSA, Infectious Diseases, Mayo Clinic, Rochester, MN

Disclosures:

J. Fiala, None

B. R. Palraj, None

M. R. Sohail, None

B. Lahr, None

L. M. Baddour, None

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