The use of “double coverage” (two antibiotics used to provide coverage for the same organism) is based upon the following assumptions:
The combination provides a broad spectrum of coverage for empiric treatment, before you know the identification and susceptibility of the offending pathogen.
The combination may provide additive or synergistic effects against the pathogen.
The combination of antibiotics may decrease or prevent the emergence of resistant bacteria.
Contemporary data do not support the use of “double coverage” for the latter two indications.
Inappropriate initial therapy has been shown to cause increased morbidity and mortality, specifically related to Gram-negative infections (usually Pseudomonas and Acinetobacter spp.).
Thus, double coverage serves the purpose of providing broad spectrum initial empiric coverage until susceptibility data are known
However, once susceptibility data are known, double coverage does not need to be continued.
No evidence exists to support the superiority of combination therapy over monotherapy for Gram negative infections once susceptibilities are known.
Thus, once culture identification and susceptibilities have been reported, de-escalation to a single agent is strongly recommended.
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