Comparison of microbiological results of superficial swab cultures vs deep tissue samples and aspiration fluids cultures in patients with chronic osteomyelitis and prosthetic joint infections

Abstract

Prosthetic joint infections and chronic osteomyelitis are hard to treat infections, generally requiring surgical intervention with a high morbidity and financial cost. Besides surgical interventions, at least six-eight weeks of antibiotherapy is required. The cost of antibiotherapy, hospitalization and side effects which are requiring laboratory studies are high. The real etiologic agent is to be identified as much as possible, providing rational therapy. Rational therapy, even, can effect the type of surgical intervention. In this study, microbiologic results of superficial swabs were compared with the results of deep tissue cultures (tru-cut biopsy and/or curettage materials). A total of 107 patients, 58 women (54%) and 49 men (46%), were included. Of 107 patients, 54 (50.5%) had prosthetic joint infection and 53 (49.5%) had chronic osteomyelitis. While in 77 patients the etiologic agent was identified, it was not identified in one third of the cases. Of the agents identified, 59 (76%) were Gram-positive cocci, 19 (24%) were Gram-negative bacilli. Gram-positive cocci were identified in 32 (86.5%) cases of prosthetic joint infection, and in 27 (65.8%) cases of chronic osteomyelitis. 93.2% of Gram-positive cocci was staphylococci. In 66 patients (61.7%) there was a discordance between the culture results of superficial swabs and deep tissue/pus materials. In 37 (34.6%) patients, an agent was identified in deep tissue/pus material, but not in superficial swab cultures. In nine (8.4%) patients, no agent was identified in tissue/pus culture but identified in superficial swab culture. In 20 (18.7%) patients, different isolates were identified between the deep tissue/pus material and superficial swabs. In 41 (28.4%) patients, the results were in accordance. Of these, in 19 (17.8%) patients, the same agent was obtained. In 22 patients (20.6%), no isolate was identified in superficial swab nor deep tissue/pus cultures. As a result, superficial swab cultures are not in accordance with the deep tissue/pus cultures. It would not be wise to direct the treatment via only superficial swab cultures.