Acinetobacter Baumannii-related Osteomyelitis: Clinical and Epidemiological Characterization

Acinetobacter baumannii is an opportunist pathogen that has become increasingly important over recent years as a cause of nosocomial infections. Ventilator-associated pneumonia, central line-associated bloodstream infection and bone and soft tissue infections secondary to open fractures are among the conditions most associated with this agent . Attention is drawn not only to the increasing incidence of this agent over the last few years but also to the rapid worsening of its susceptibility to antimicrobial agents, including carbapenems. Few therapeutic options are available for treating pan-resistant strains: colistin and tigecycline has been used, but resistance to these options frequently emerges in clinical practice. Taking into account the fact that fewer new antimicrobial agents are being validated and introduced into clinical practice, the growing prevalence of isolates with these high levels of resistance is becoming a matter of increasing concern. Certain risk factors have also been correlated with infection related to A. baumannii. The most important are prolonged hospitalization in intensive care units and use of invasive devices. Another important risk factor is severe trauma: A. baumannii is associated with invasive infections, including osteomyelitis following open fracture reduction. Studies that included military personnel and civilians involved in the recent conflicts in Iraq and Afghanistan have shown high prevalence of A. baumannii as causative agent in cases of osteomyelitis secondary to traumatic injuries. Also, in Brazil, a retrospective study that analyzed 101 cases of osteomyelitis due to Gram-negative bacilli showed that A. baumannii was the second most prevalent agent and that it had a high degree of antimicrobial resistance, particularly to carbapenems. The objectives of this retrospective study are: 1. clinically and epidemiologically characterize 241 patients with osteomyelitis related to A. baumannii who were admitted at the Institute of Orthopedics and Traumatology, Hospital das Clínicas, University of São Paulo; 2. to describe the antimicrobial susceptibility profile of A. baumannii strains isolated; 3. to evaluate the patients' outcomes (remission, recurrence, limb amputation or death) according to the antimicrobial treatment used, including tigecycline; 4. to compare efficacy and safety profiles of tigecycline, colistin and ampicillin-sulbactan among patients with carbapenem-resistant A. baumannii related osteomyelitis.