Does microbial colonisation of a neck drain predispose to surgical site infection: clean vs clean-contaminated procedures.

PURPOSE: The study was designed to assess the difference in microbiological colonisation and growth that may occur in drains, in the setting of clean-contaminated compared to clean head and neck surgery.
METHODS: A prospective observational cohort study was performed. Surgical drain tips upon removal were sent for bacterial culture and the culture results were compared between clean-contaminated and clean procedures using mixed effects logistic regression. In all statistical analyses, a priori, p < 0.05 (two-tailed) was calculated to indicate statistical significance.
RESULTS: One hundred and ten drains were examined in both clean-contaminated and clean procedures. Drains from clean-contaminated procedures had a significantly longer time in situ (11 vs 5 days, p < 0.001). Overall, significant evidence was seen for an association between procedure type and drain growth rates: 68% of clean-contaminated procedures; and 45% of clean procedures. Although not statistically significant, there was an increase in normal skin flora contaminated drains in clean-contaminated procedures (41 vs 25%). Rates of pathogenic skin organisms (15 vs 16%) and pathogenic oropharyngeal organisms (2.9 vs 0%) were similar for clean-contaminated vs clean procedure patients.
CONCLUSION: This preliminary study demonstrated a higher rate of microbial contamination of neck drains that were placed during procedures that involved continuity with the upper aero-digestive tract and neck. Retrograde migration of skin flora along the drain is common but of no clinical significance. Similar rates of pathogenic microbial growth have been demonstrated thus far. However, selection of nosocomial pathogens due to extended antibiotic prophylaxis may pose a risk for infection. LEVEL OF EVIDENCE: 1b.