Common Pathogens Found in Wounds
Staph. aureus, Beta hemolytic Strep. (S. pyogenes, S. agalactiae), E. coli, Proteus, Klebsiella, Pseudomonas, Acinetobacter, Stenotrophomonas, anaerobic bacteria
Wound Infection Progress and Gram Test Results
Particular types of bacteria may be suspected based on the age of the wound and the gram test results.
Early Acute Wound: Normal skin flora, followed by Staph. Aureus and Beta-hemolytic Strep.; mostly gram positive bacteria
About Four Weeks: facultative anaerobic gram negative rods such as Proteus, E. coli, and Klebsiella
Longer Term Wound: Anaerobic bacteria become more common
Long Term Chronic Wound: Often contain more anaerobic bacteria than aerobic bacteria - aerobic gram negative rods also seen; Examples include Pseudomonas, Acinetobacter, Stenotrophomonas
Common Culture Media
The following culture media can be used to isolate specific types of organisms:
Mannitol Salt Agar: Use to isolate Staphylococci and Micrococci
Phenylethyl Alcohol Agar: Use to isolate gram positive bacteria
Blood Agar: Use to grow most bacteria
Chocolate Agar: Used to isolate Neisseria and Haemophilus
Common Enzymatic Tests
Catalase: Positive - Staphylococci; Negative - Streptococci and most anaerobes
Coagulase: Positive - Staphylococcus aureus
Oxidase: Positive - most gram negative bacteria
*Please also see the first reference listed below, which shows a detailed flowchart for the identification of bacteria based on differential culture media, enzymatic tests, and resistance patterns.
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