Introduction
Surgical infection is an infection that needs surgical management or develops after an operation, injury or invasive procedure. This topic covers how surgical infections are classified, which microorganisms cause them, and acute purulent infection, with the abscess as its typical localised form. Phlegmon and chronic purulent infection are covered in the next topic.
Classification of surgical infection
Surgical infections are classified by several complementary criteria. In an oral answer, name the criteria, give the types for each and one example.
Causative agents of surgical infections
Most surgical infections are mixed or polymicrobial. The likely agent depends on the site, whether the infection was community-acquired or hospital-acquired, and whether the bowel or another mucosal surface was opened. Cultures and sensitivity testing guide definitive therapy.
- Staphylococcus aureus: the most common cause of skin and soft tissue abscesses; methicillin-resistant strains (MRSA) are important in hospitals and the community.
- Streptococcus pyogenes (group A): spreading soft tissue infections and phlegmon.
- Enterobacteriaceae (Escherichia coli, Klebsiella, Proteus): Gram-negative rods typical of intra-abdominal, pelvic and urinary-source infections.
- Pseudomonas aeruginosa: hospital-acquired infections of wounds, burns and catheters.
- Enterococcus faecalis: intra-abdominal and urinary infections, often resistant to many antibiotics.
- Anaerobes such as Bacteroides fragilis and peptostreptococci: abscesses arising from bowel, mouth or pelvic sources, often with foul-smelling pus and gas.
- Clostridium species: gas-forming infections that need urgent recognition and separate management.