SKIN AND SOFT TISSUE INFECTIONS IN INJECTION DRUG USERS
The mechanism by which infection is established probably relates to tissue trauma, direct
effects of drugs, tissue ischemia, and inoculation of bacteria. As a result of repeated injections
into a single site, skin and surrounding tissue are damaged, develop local ischemia and
necrosis, and become susceptible to infection. Opiates suppress T-cell functions and also
inhibit phagocytosis, chemotaxis, and killing by neutrophils and macrophages. Infection
ranges from cellulitis to skin and soft tissue abscesses, and occasionally fasciitis and
pyomyositis. The most common sites of involvement correspond to injection sites: the upper
and lower extremities, the groin and antecubital fossa, with the microbiology being
monomicrobial or polymicrobial, involvingS. aureus,Str. viridans, Str. pyogenes, Str. anginosus
group, Ei. corrodens; anaerobic organisms likeClostridiumspp. and Prevotella; and gram-
negative enteric organisms includingE. coli, Klebsiella,Proteus mirabilis, Pseudomonas, and
Enterobacter(71–73). Black tar heroin use has resulted in outbreaks ofC. botulism, C. tetaniand
C. sordelliin IV drug users (74) (for treatment refer to Table 2).
Figure 7 (A) Limb-threatening left diabetic foot ulcer (B) Rapid progression to gas gangrene. Patient underwent
below knee amputation. Operative cultures grew group GStreptococcus, MRSA, Streptococcus viridans,
Enterococcusspp., andBacteroides fragilis.
Severe Skin and Soft Tissue Infections in Critical Care 309