spread to adjacent structures may result in osteomyelitis. Cellulitis infrequently occurs as a
result of bacteremia. Uncommonly, pneumococcal cellulitis occurs on the face or limbs in
patients with diabetes mellitus, alcohol abuse, systemic lupus erythematosus, nephritic
syndrome, or a hematological cancer (22). Meningococcal cellulitis occurs rarely, although it
may affect both children and adults (33). Bacteremic cellulitis due toV. vulnificuswith
hemorrhagic bullae may follow the ingestion of raw oysters by patients with cirrhosis,
hemachromatosis, or thalassemia. Cellulitis caused by gram-negative organisms usually
occurs through a cutaneous source in an immunocompromised patient but can also develop
through bacteremia.Cryptococcus neoformans,Fusarium,Proteus, andPseudomonasspp. have
been associated with bloodstream infections. Immunosuppressed patients are particularly
susceptible to the progression of cellulitis from regional to systemic infections. The distinctive
features including the anatomical location and the patient’s medical and exposure history
should guide appropriate antibiotic therapy. Periorbital cellulitis involves the eyelid and
periocular tissue and should be distinguished from orbital cellulitis because of complication of
the latter: decreased ocular motility, decreased visual acuity, and cavernous-sinus thrombosis.
A variety of noninfectious etiologies resembling cellulitis in appearance should be
distinguished from it. Sweet syndrome associated with malignancy consists of tender
erythematous pseudovesiculated plaques, fever, and neutrophilic leukocytosis, which can
mimic cellulitis. Cutaneous metastasis (tumor emboli) from solid tumors ranging from 0.7% to
9% can mimic cellulitis (34–36) (Fig. 3).
Diagnostic Studies
Diagnosis is generally based on clinical and morphological features of the lesion. Culture of
a needle aspirate is not generally indicated because of a low yield. Among 284 patients, a
likely pathogen was identified in 29%. Of 86 isolates, only 3 represented mixed culture.
Gram-positive organisms (mainlyS. aureus, group A or B streptococci, andEn. faecalis)
accounted for 79% of cases; the remainder was caused by gram-negative bacilli (Enter-
obacteriaceae,Haemophilus influenzae, Pasteurella multocida, Pseudomonas aeruginosa,and
Acinetobacterspp.) (26). Bacteremia is uncommon in cellulitis with only 2% to 4% yielding a
pathogen (26). Blood cultures appear to be positive more frequently with cellulitis
superimposed on lymphedema. Radiography and computed tomography are of value
when the clinical setting suggests a subjective osteomyelitis or there is clinical evidence to
suggest adjacent infections such as pyomyositis or deep abscesses. When it is difficult to
differentiate cellulitis from NF, a magnetic resonance imaging (MRI) may be helpful, though
surgical exploration for a definite diagnosis should not be delayed when the latter condition
is suspected.
Figure 2 Cellulitis of the left thigh in a alcoholic patient, blood cultures grew group BStreptococcus.
Severe Skin and Soft Tissue Infections in Critical Care 299