Low sensitivity of needle aspiration cultures in patients with cellulitis/erysipelas

Cellulitis is normally treated without knowledge of the responsible pathogen. Blood cultures are positive in about 2-4 %, and superficial swabs are of no value. Needle aspiration has been proposed with identifying the likely pathogen in up to 29 %, but these studies are of older date and the technique is not widely used.

We prospectively evaluated the sensitivity of needle aspiration cultures in all patients with erysipelas/cellulitis. Diagnosis was made clinically by the treating physician. Needle aspiration was done with a 1 ml syringe and a 26G needle. The needle was removed and the syringe brought to the microbiological laboratory and analysed according to standard procedures.

95 Patients were seen during a period of 22 month. 4 Patients were excluded, as diagnosis was not confirmed. Cellulitis was present in 10/91 and erysipelas in 81/91 patients. In the first 25 patients with needle aspiration from the margin, none was positive. In 8/66 (12 %) patients where needle aspiration was done at the site of maximum inflammation, the pathogen was identified. 4/8 Cultures were positive for S. aureus, 2/8 for streptococci and 2/8 for other bacteria. In 11/66 (16.6 %) patients, skin colonisation flora was detected. In the subgroup of patients without prior antibiotic treatment and needle aspiration from the site of maximum inflammation, sensitivity was slightly better 8/55 (14.5 %; 95 % CI 7.5-25.8 %).

Needle aspiration culture had a low sensitivity for detecting responsible pathogen in patients with cellulitis/erysipelas. No impact in antibiotic treatment could be observed.