Utility of Gram stain in the clinical management of suspected ventilator-associated pneumonia. Secondary analysis of a multicenter randomized trial.
OBJECTIVE
Gram stains of endotracheal aspirates (EA) and bronchoalveolar lavages (BAL) may guide empiric antibiotic therapy in critically ill patients with suspected ventilator-associated pneumonia (VAP). Previous studies differ regarding the ability of the Gram stain to predict final culture results. The aim of the present study was to evaluate the relationship between EA or BAL Gram stains and final culture results in intensive care unit patients with a suspected VAP.


METHODS
We retrospectively analyzed data from the Canadian multicenter VAP study to correlate EA or BAL Gram stain and final culture results. We categorized Gram stains as Gram positive (GP) and Gram negative (GN) if any GP or GN organisms respectively were seen on staining. Cultures were considered "positive" if they yielded pathogenic organisms on final results.


RESULTS
Seven hundred forty patients were enrolled in the study; 35 did not have a Gram stain done leaving 350 BALs and 355 EAs from 705 patients. Pooling BAL and EA results, we found the overall agreement between Gram stain class and pathogenic bacteria culture results to be poor (kappa = 0.36; 95% CI, 0.31-0.40). Among specimens with Gram stains showing no organisms, 99 (30%) of 331 grew pathogenic organisms. Among specimens with Gram stains showing no GN organisms, 113 (25%) of 452 grew pathogenic GN organisms. Among specimens with Gram stains showing no GP organisms, 45 (11%) of 428 grew pathogenic GP organisms.


CONCLUSIONS
Gram stains performed for clinically suspected VAP poorly predict the final culture result and thus have a limited role in guiding initial empiric antibiotic therapy in such patients.
Albert
M
M
Division of Critical Care, Department of Medicine, Université de Montréal, Montréal, Canada H3T 1J4.
Friedrich
J O
JO
Adhikari
N K J
NK
Day
A G
AG
Verdant
C
C
Heyland
Daren K
DK
D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D001999:Bronchoscopy; D002170:Canada; D016009:Chi-Square Distribution; D005840:Gentian Violet; D006801:Humans; D007362:Intensive Care Units; D010619:Phenazines; D053717:Pneumonia, Ventilator-Associated / Q000188:drug therapy* / Q000382:microbiology*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology*; D013396:Suction
D000900:Anti-Bacterial Agents; C035863:Gram's stain; D010619:Phenazines; D005840:Gentian Violet