Chronologic appearance and characteristics of organisms in burns

Organism, chronology	Characteristics
Commensal skin organisms (gram positive) result in early colonization of burns	Streptococcus and Staphylococcus species primarily Other sources are upper respiratory tract and environment Topical antimicrobials help decrease colonization
Gram-negative species dominant >5 days	2 to 4 days post-burn, gram-negative bacteria colonize wound Patient skin, upper respiratory tract, gastrointestinal tract, and hospital environment are typical sources Pseudomonas aeruginoasa, Acinetobacter baumannii, Escherichia Coli, Klebsiella pneumoniae, Enterobacter cloacae
If gram-negative cover is initiated, yeast often appears	Yeast and fungi colonization follows Majority are Candida species, other fungi are increasing in frequency
Finally, more resistant bacteria and fungi invade the wound	MRSA, VRE, multi-drug-resistant Pseudomonas and Acinetobacter species, and fungi Usually secondary to broad-spectrum antibiotics, or inadequate host response or therapeutic measures (excision burn, topical and systemic antibiotics) Transition from colonization to invasion

MRSA: methicillin-resistant Staphylococcus aureus, VRE: vancomycin-resistant Enterococcus

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