Impact of Reporting Gram Stain Results from Blood Culture Bottles on the Selection of Antimicrobial Agents

Yuki Uehara, MD, PhD; Michiko Yagoshi, MT; Yumiko Tanimichi, MT; Hiroko Yamada, MT; Kazuo Shimoguchi, MT; Sachiyo Yamamoto, MT; Mitsuru Yanai, MD, PhD; Kazunari Kumasaka, MD, PhD


Am J Clin Pathol 

In This Article

Abstract and Introduction


We assessed the usefulness of reporting direct blood Gram stain results compared with the results of positive blood cultures in 482 episodes and monitored impact on selection of antimicrobial treatment. We found that the reporting groups "Staphylococcus spp," "Pseudomonas spp and related organisms," and "yeasts" identified in this way matched perfectly with later culture identification. When the report indicated Staphylococcus spp or Pseudomonas spp and related organisms, physicians started or changed antimicrobials suitable for these bacteria more frequently than when "other streptococci" and "family Enterobacteriaceae" were reported (P < .05). Incorrect recognition of Acinetobacter spp as Enterobacteriaceae family is still the most challenging problem in this context. Gram stain results that definitively identify Staphylococcus spp, Pseudomonas spp and related organisms, and yeasts reliably can be rapidly provided by clinical laboratories; this information has a significant impact on early selection of effective antimicrobials. Further investigation is needed to assess the clinical impact of reporting Gram stain results in bacteremia.


Clinically significant bacteremia is an important cause of serious morbidity and mortality. In a previous report of 843 episodes of positive blood cultures from 707 patients, bacteremia-associated mortality was 17.5%.[1] In another report of 955 bacteremic episodes, mortality due to unidentified organisms was 44%, and even when the organisms were known, mortality was still as high as 25%.[2]

To reduce mortality and morbidity in bacteremic patients, it is necessary to initiate effective antimicrobial therapy as soon as possible. Many reports indicate a relationship between inadequate antimicrobial therapy and unsatisfactory outcome.[3–8] Bacteremia frequently causes sepsis and septic shock. Because prompt institution of therapy active against the causative pathogen is one of the most important predictors of outcome, physicians must establish a system for rapid administration of a rationally chosen drug or combination of drugs.[9]

The clinical microbiology laboratory has an important role in the management of bacteremia. Detecting pathogenic microorganisms in blood cultures and testing antimicrobial susceptibility always assists in selecting the appropriate antimicrobial agent. The most important and primary test to perform on any positive blood culture is Gram stain,[10] which is the most rapid and simplest test to characterize microorganisms. It is therefore highly likely that the information provided by the Gram stain will help to assess the adequacy of antimicrobial therapy selected after collecting blood culture specimens and before final identification of the microorganism.[11] In recent reports, the impact of Gram stain results on patient mortality has been documented.[12–15] On the other hand, there remains the possibility that Gram stain results do not match with the final identification of microorganisms. This would carry a risk leading to inadequate antimicrobial therapy and potentially affecting patients' clinical course and mortality.

The aim of our study was to assess the advantages and disadvantages of reporting Gram stain results for selecting antimicrobial agents and correlating these results with the patients' hospital courses.


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