Microbiology S. aureus is a pathogen in more than half of cases of contiguous-focus osteomyelitis. However, in contrast to hematogenous osteomyelitis, these infections are often polymicrobial and are more likely to involve gram-negative and anaerobic bacteria. Hence a mixture of staphylococci, streptococci, enteric organisms, and anaerobic bacteria may be isolated from a diabetic foot infection or pelvic osteomyelitis underlying a decubitus ulcer. Aerobic and anaerobic bacteria cause osteomyelitis following surgery or soft tissue infection of the oropharynx, paranasal sinuses, gastrointestinal tract, or female genital tract. A human bite may result in mixed infection of the hand, with anaerobes included among. | Chapter 120. Osteomyelitis Part 3 Microbiology S. aureus is a pathogen in more than half of cases of contiguous-focus osteomyelitis. However in contrast to hematogenous osteomyelitis these infections are often polymicrobial and are more likely to involve gram-negative and anaerobic bacteria. Hence a mixture of staphylococci streptococci enteric organisms and anaerobic bacteria may be isolated from a diabetic foot infection or pelvic osteomyelitis underlying a decubitus ulcer. Aerobic and anaerobic bacteria cause osteomyelitis following surgery or soft tissue infection of the oropharynx paranasal sinuses gastrointestinal tract or female genital tract. A human bite may result in mixed infection of the hand with anaerobes included among the etiologic agents. S. aureus is the principal cause of postoperative infections coagulase negative staphylococci are common pathogens after implantation of orthopedic appliances and these organisms as well as gram-negative enteric bacilli atypical mycobacteria and Mycoplasma may cause sternal osteomyelitis after cardiac surgery. Infection with P. aeruginosa is frequently associated with puncture wounds of the foot especially when a nail passes through a sneaker and Pasteurella multocida infection commonly follows cat bites. Chronic Osteomyelitis With prompt treatment 5 of cases of acute hematogenous osteomyelitis progress to chronic osteomyelitis. Chronic infection is more likely to develop in contiguous-focus than in hematogenous osteomyelitis. The presence of a foreign body makes establishment of chronic infection especially likely. A protracted clinical course long periods of quiescence and recurrent exacerbations are characteristic of chronic osteomyelitis. Sinus tracts between bone and skin may drain purulent material and occasionally pieces of necrotic bone. An increase in drainage pain or swelling signals an exacerbation which is usually accompanied by increases in CRP level and ESR. Fever is unusual except when obstruction .
