Quantitative tracheal bacteriologic and cytologic studies in patients with long-term tracheostomies

Area of Science:

• Microbiology
• Pulmonology
• Critical Care Medicine

Background:

• Tracheostomies are common in clinical practice, necessitating understanding of lower airway microbial dynamics.
• The microbial flora in the lower airways of patients with stable tracheostomies is not well-characterized.
• Distinguishing colonization from infection is crucial for appropriate antibiotic use.

Purpose of the Study:

• To quantitatively characterize the bacterial flora in tracheal aspirates of clinically stable tracheostomized patients.
• To assess the relationship between upper and lower airway flora.
• To evaluate the utility of quantitative bacterial cultures and cytology in differentiating colonization from infection.

Main Methods:

• Quantitative aerobic and anaerobic cultures of tracheal aspirates from 16 patients.
• Collection of saliva and throat swabs for comparison.
• Cytologic analysis of tracheal aspirates.
• Repeat cultures to assess flora changes over time.

Main Results:

• An average of six bacterial isolates per specimen with a mean concentration of 10^6.9 organisms/mL.
• Predominantly aerobic and facultative gram-negative bacilli were identified.
• Anaerobic bacteria were infrequent (32%) and in low concentrations.
• Significant flora changes occurred over 30-60 days, though dominant species often persisted.
• Little correlation between upper and lower airway flora; no correlation between polymorphonuclear leukocytes and bacterial counts.

Conclusions:

• Tracheal aspirates from stable tracheostomized patients contain a complex, predominantly aerobic flora.
• This flora is dynamic and shows limited relationship to upper airway microbiota.
• Quantitative bacterial cultures and cytologic analysis are insufficient for distinguishing colonization from infection requiring antibiotics.