Earlier identification of single positive blood culture growing gram-positive cocci did not significantly influence prescribing patterns of vancomycin, according to an investigation on the effect of a rapid blood culture identification panel (BCID) on vancomycin-prescribing patterns and patient outcomes for single positive blood culture (PBC) growing gram-positive cocci published in the European Journal of Clinical Microbiology & Infectious Diseases.

Investigators compared 2 groups of adult patients: patients with single-positive blood culture growing gram-positive cocci with conventional organism identification (pre-BCID) and patients with organism identification by blood culture identification panel (post-BCID). An Antimicrobial Stewardship Program (ASP) review of positive blood culture was performed in both groups and vancomycin prescribing patterns were studied.

In total, 86 pre-BCID and 102 post-BCID patients were included in the study. Organism identification occurred 21 hours sooner in the post-BCID group (P <.001). The most commonly isolated organisms were coagulase-negative staphylococci (73%), although researchers noted that 98% of these isolates were deemed contaminants. Although a similar number of patients in each group was identified as warranting vancomycin (29% in both groups), vancomycin was used in 52% of the pre-BCID group, compared with 41% of the post-BCID group. In the 133 patients in whom vancomycin was not deemed necessary vancomycin use (51% pre-BCID vs 36% post-BCID; P =.09) and time from culture positivity to vancomycin discontinuation (1.5 vs. 1.7 days; P =.92) did not differ between groups. Investigators also found no differences in the development of nephrotoxicity, length of stay, readmission, mortality, or hospital costs between groups.

Researchers noted that it is possible that the opportunity for detectable improvements in the post-BCID group in this analysis was lessened due to the baseline antimicrobial stewardship review of positive blood cultures that was present in both groups. Further, the lack of improvement in prescribing patterns in the post-BCID group may be a result of “judicious use of vancomycin in the pre-BCID group.” However, this end point could not be investigated because whether antimicrobial changes were made by ASP or independently by the treatment team was not consistently documented.

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The study investigators concluded that, “our observations support that earlier organism identification of likely blood culture contaminants in conjunction with ASP intervention appears to limit the duration of unnecessary vancomycin therapy, but not in a significant manner compared with ASP intervention alone.” They also recommended that larger studies accounting for the impact of ASP intervention be conducted to determine the values of each component.

Reference

MacVane SH, Raux BR, Smith TT.  Evaluation of rapid polymerase chain reaction-based organism identification of gram-positive cocci for patients with a single positive blood culture [published online May 11 2019]. Eur J Clin Microbiol Infect Dis. doi:10.1007/s10096-019-03574-3