Pyomyositis

Background

• Pus within an individual muscle group, often associated with tropical climates
• Risk factors include tropical climates, HIV, diabetes mellitus
• May have a firm woody feel
• CK often normal

Microbiology

• Staphylococcus aureus in 90%
• Group A Streptococcus and Enterobacterales are also possible

Investigations

• MRI establishes the diagnosis, though CT and US are useful
• Get blood cultures (positive in 5-30%)
• Repeat imaging if persistently bacteremic in order to find other infections

Management

• Needs incision and drainage
• Vancomycin or cefazolin is appropriate empiric therapy
• Add Gram-negative coverage if immunocompromised or open trauma
• Adjust based on microbiology
• Duration is with IV until better and not bacteremic, then oral to complete 2-3 weeks