Need for appropriate specimen for microbiology diagnosis of chronic osteomyelitis

Chronic osteomyelitis (COM) is a common infection, especially in developing countries. An adequate bone biopsy specimen processed with appropriate microbiology culture methods for isolation and identification of the causative organisms is considered as the gold standard for the diagnosis of osteomyelitis.

The present study is a retrospective microbiology analysis of the specimen from 219 clinically diagnosed cases of COM between January 2013 and April 2016.

The overall culture positivity was 111/219 (50. 6%), colonization was seen in 22/219 (10.5%), while the rest 86/219 (39.3%) were culture-negative specimen; culture positivity was highest from tissue specimen (71/113, 62.8%). Among the swabs, 40/106 (37.7%) were culture positive. About 28/40 (70%) culture-positive swabs showed significant growth of Gram-positive organisms. Colonization with skin flora such as diphtheroids and Coagulase-negative Staphylococci was seen in 22/106 (20.7%) of the swabs. Sterile cultures (44/106, 41.6%) were high among the swab specimen. Gram-positives were most common (75/111, 67.56%). Staphylococcus aureus was the predominant organism isolated in 70/111 (63%) cases. Gram-negative bacilli showed a high level of antibiotic resistance.

As per our data, the culture yield from wound swabs was low or contaminated with normal skin flora, as compared to the biopsy or tissue specimen. Hence, an appropriate sampling of the infected bone using recommended protocols is highly essential for improving microbiological yield and the outcome of COM.