Background:    Osteomyelitis is painful condition for patients and frustrating their doctors.  The key to successful management is early diagnosis, including bone sampling for microbiological and pathological examination to allow targeted and long-lasting antimicrobial therapy.  Sometime we can not find the causative organism from the tissue culture and require clinical data to select the empirical antibiotics.

Purpose:   To report the incidence of causative organism of osteomyelitis and determine such risk factors as well as clinical features of gram negative osteomyelitis in the Northeast region of Thailand.

Materials and Methods:   Between January 1999 and December 2004, 135 patients were diagnosed with musculoskeletal infection at Sakolnakorn Hospital, Sakolnakorn, Thailand.  Eighty-seven patients were excluded from the study, leaving forty-eight, who made up the study population.  Thirteen patients were diagnosed with gram-negative Osteomyelitis on the basis of gram stain or culture of bone from OPD or IPD records.  The signs and symptoms, the bone that were involved, the patient occupation, the duration of symptoms, and any concurrent disease were recorded.

Study design: Descriptive analytic study 

Setting:  Sakolnakorn Hospital, Sakolnakorn, Thailand

Results:   Seven men and nine women had gram-negative osteomyelitis.  The mean age (and standard deviation) was 53.75±14.18 years in the group with gram-negative osteomyelitis and 31.17±26.15 years in the group with gram-positive osteomyelitis.  The most common gram-negative organism was Pseudomonas auriginosa (5/16).  The most common gram-positive organism was Staphylococcus aureus.  The odds of a patients having gram-negative osteomyelitis was 6.9 times greater when he or she had concurrent diabetes mellitus than when he or she did not.  Six (37.5%) of the patients with gram-negative osteomyelitis and 3 (9%) of the patients with gram-positive osteomyelitis had involved the bone of foot, so the odds ratio that an infection in the bone of foot was caused by gram-negative organism was 5.3 (95% confidence interval, 1.54 to 35.73; P=0.02).

Discussion and Conclusion:  In conclusion, we have shown that diabetes mellitus and involvement of bone of foot were the risk factors of gram-negative osteomyelitis.  The physician should select the empirical antibiotic that covered gram-negative organism in this group of patients and pay attention in the patients who are old age with concurrent disease.