title: The accuracy of Gram stain of respiratory specimens in excluding Staphylococcus aureus in ventilator-associated pneumonia.
abstract: OBJECTIVE
  To evaluate the Gram stain of deep tracheal aspirate as a tool to direct empiric antibiotic therapy, and more specifically as a tool to exclude the need for empiric antibiotic coverage against Staphylococcus aureus in ventilator-associated pneumonia (VAP).
  
  
  METHODS
  A prospective, single-center, observational, cohort study.
  
  
  METHODS
  All wards at a community hospital.
  
  
  METHODS
  Adult patients requiring mechanical ventilation, identified as having VAP in a 54-month prospective surveillance database.
  
  
  METHODS
  Sampling of lower airway secretions by deep endotracheal aspiration was taken from each patient who developed VAP. Samples were sent immediately for Gram stain and qualitative bacterial cultures. Demographic and relevant clinical data were collected; Gram stain, culture, and antibiotic susceptibility results were documented; and outcome was followed prospectively.
  
  
  RESULTS
  The analysis included 114 consecutive patients with 115 episodes of VAP from June 2007 to January 2012. Sensitivity of Gram stain compared with culture was 90.47% for gram-positive cocci, 69.6% for gram-negative rods, and 50% for sterile cultures. Specificity was 82.5%, 77.8%, and 79%, respectively. Negative predictive value was high for gram-positive cocci (97%) and sterile cultures (96%) but low for gram-negative rods (20%). Acinetobacter baumanii (45%) and Pseudomonas aeruginosa (38 %) were the prevailing isolates. S aureus was found in 18.3% of the patients. Most isolates were multiresistant.
  
  
  CONCLUSIONS
  Absence of gram-positive bacteria on Gram stain had a high negative predictive value. These data can be used to narrow the initial empiric antibiotic regimen and to avoid unnecessary exposure of patients to vancomycin and other antistaphyloccocal agents.
authors: Infectious Diseases Unit, E. Wolfson Hospital, Holon 58100, Israel.
authors: Tamar
authors: T
authors: Gottesman
authors: Infectious Diseases Unit, E. Wolfson Hospital, Holon 58100, Israel.
authors: Orit
authors: O
authors: Yossepowitch
authors: Microbiology Laboratory, E. Wolfson Hospital, Holon 58100, Israel.
authors: Evgenia
authors: E
authors: Lerner
authors: Microbiology Laboratory, E. Wolfson Hospital, Holon 58100, Israel.
authors: Orna
authors: O
authors: Schwartz-Harari
authors: Intensive Care Unit, E. Wolfson Hospital, Holon 58100, Israel.
authors: Arie
authors: A
authors: Soroksky
authors: Department of Statistics and Operations Research, Tel Aviv University, Tel Aviv, Israel.
authors: Daniel
authors: D
authors: Yekutieli
authors: Infectious Diseases Unit, E. Wolfson Hospital, Holon 58100, Israel; Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Electronic address: midan@post.tau.ac.il.
authors: Michael
authors: M
authors: Dan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D004396:Coloring Agents; D005260:Female; D005840:Gentian Violet; D016946:Gram-Negative Aerobic Rods and Cocci / Q000302:isolation & purification; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D006095:Gram-Positive Cocci / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D010619:Phenazines; D053717:Pneumonia, Ventilator-Associated / Q000382:microbiology*; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification*; D014640:Vancomycin
chemical_list: D000900:Anti-Bacterial Agents; D004396:Coloring Agents; C035863:Gram's stain; D010619:Phenazines; D014640:Vancomycin; D005840:Gentian Violet
keywords: Gram stain; Intensive care unit; Mechanical ventilation; Nosocomial infection; Staphylococcus aureus; Ventilator-associated pneumonia