Table 3.
Microbiologic clues for the diagnosis and management of VAT, VAP or VARI
| EA | Clues & Interpretation |
|---|---|
| Gram stain smear | |
| Polymorphonuclear leukocytes (PMNL/LPF) | |
| Rare: <1 | No infection |
| Few: 1–10 | Unlikely infection |
| Moderate: 10–25 | Suggests infection |
| Many: >25 | Suggests infection |
| Bacteria–gram stain color | |
| Blue | Gram positive (G+) |
| Red | Gram negative (G−) |
| Bacteria–morphology | |
| Round | G+ cocci in chains: streptococci or clusters: staphylococci |
| Rods | G− bacilli: eg, Escherichia coli or Pseudomonas aeruginosa |
| Number of bacteria | |
| None or rare | Colonization |
| Moderate to many | Suggests infection, consider therapy |
| Culture data | |
| Semiquantitative culture (SQ-EA): | |
| Rare (+), few (++) colonies | Colonization, observe |
| Moderate (+++), many (++++) colonies | Possible infection, consider therapy |
| Quantitative (Q-EA): | |
| <105 cfu/mL | Colonization, observe |
| ≥105-6 cfu/mL | Infection, consider therapy |
Note differences in Gram stain and culture criteria for EA sputum samples examined by quantitative (Q-EA) and semi-quantitative (SQ-EA) methods and diagnostic criteria for samples obtained by bronchoscopic (B) and non-bronchoscopic (N) bronchoalveolar lavage (BAL) and protected specimen brush (PSB).
Abbreviations: cfu, colony forming units; Ea, endotracheal aspirate; HPF, high power field of microscope; LPF, Low power field of microscope; VAP, ventilator-associated pneumonia; VARI, ventilator-associated respiratory infection; VAT, ventilator-associated tracheobronchitis.