[Classification and microbiology of osteomyelitis]

The clinical presentation of osteomyelitis is multifarious. Therefore, patients are diagnosed and treated by various specialists with many different concepts of optimal management. Originally, only the acute and the chronic presentations were differentiated. The classification of Waldvogel, which is based on pathogenetic mechanisms, is more sophisticated. Diabetic foot is classified according to Wagner, who takes into account the continuous progression from sore to ulcer to osteomyelitis to gangrene. The staging according to Cierny-Mader is the most useful for the therapeutic management by surgeons. The spectrum of microorganisms is variable according to the type of osteomyelitis, epidemiology, age of the patient, co-morbidity, microbiological technique (culture, PCR), and duration of the infection. S. aureus is the leading pathogen in each type of osteomyelitis. Over the past 20 years, antimicrobial resistance has become an increasing problem. In case of osteomyelitis, standard susceptibility testing can be inaccurate. In case of device-related infection or in any type of chronic osteomyelitis, antimicrobial agents must be efficacious on stationary-phase and adhering microorganisms. Microbiologic culture and susceptibility testing should always be performed, in order to optimize the antimicrobial therapy.