Severe Necrotizing Soft Tissue Infections-Is Wound Microbiology a Prognostic Factor for Clinical Outcome?

Necrotizing soft tissue infections (NSTIs) represent similar pathophysiological features, but the clinical course might range from subacute to a rapidly progressive, fulminant sepsis. Initial wound microbiology is the base for the Guiliano classification. The timeline of microbiological colonization has not been described during the clinical course. The role of the different microbiological pathogens on the outcome and mortality is unclear. One hundred eighty patients were included with septic inflammation response syndrome on admission. Initial wound microbiology and the changes in wound microbiology were analysed during the clinical course and correlated with outcome and risk indicators. Overall mortality was 35%. Higher age, a high Charlson Comorbidity Index or ASA score and truncal infections were highly prognostic for a lethal outcome. Microbiological findings revealed significant differences in the persistence of bacteria during the course of disease. Streptococci were only detectable within the first 5 days, whereas other bacteria persisted over a longer period of time. Initial microbiological findings correlated with better prognosis when no causative agent was identified and for gram-negative rods. Varying survival rates were observed for different Streptococci, Staphylococci, Enterococci and other bacteria. The highest odds ratio for a lethal outcome was observed for Enterococci and fungi. Microbiological colonization changes during the clinical course of NSTIs and some microbiologic pathogens are predictive for worsening the outcome and survival. Streptococcus pyogenes is only detectable in the very early phase of NSTI and after 6 days not anymore detectable. Later Enterococci and fungi showed the highest odds ratios for a lethal outcome. Enterococci bacteria and fungi have yet not been considered of clinical relevance in NSTI or even as indicator for worsening the outcome.