Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_896_Библиотеки_им_академика_М_И_Перельмана

infection should be heightened if additional clinical factors that have been signicantly associated with foot infection are present. These include peripheral arterial disease with absent pulses or an ankle brachial index of <0.9; peripheral neuropa­thy leading to a loss of protective sensation; a history of recur­rent foot ulcers or prior amputation; foot ulcers of >30days of duration; a wound that extends to bone, i.e., a positive probe to bone test (see Osteomyelitis); and a traumatic wound [3–5]. Thereafter, infection is diagnosed clinically and to varying degrees supported by test results. Finding purulent drainage (pus) or two or more signs or symptoms of inammation (ery­thema, induration, swelling, pain, tenderness, or warmth) is indicative of infection. Clinical signs on occasion belie the signicance and severity of infection. A minimally inamed but deep ulceration may be associated with underlying osteo­myelitis [6]. Serious limb-threatening infection may not result in systemic toxicity. For example, among patients hospitalized for limb- threatening infection, only 12–35% have signicant fever [7, 8]; however, its presence may predict increased risk of amputation [9]. Fever higher than 102°F suggests infection involving deeper spaces in the foot with tissue necrosis and undrained pus, extensive cellulitis, or bacteremia with the potential for hematogenous seeding of remote sites. Laboratory studies may be supportive of the diagnosis of these infections but must be interpreted in the context of clinical ndings. White blood cell count may be normal in up to 50% of patients with deep foot infection [10–12]. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) may be normal in infected patients, and in those with peripheral neuropathy, ESR may have reduced utility in predicting osteomyelitis compared to CRP [13]. Elevated concentration of CRP and procalcitonin can help distinguish mild or moderately infected ulcers from those that are uninfected [14]. In addition to the presence of classic pathogens, foot ulcers are often contami­nated or colonized by commensal organisms that on occasion become pathogens. Consequently, cultures, while essential in the assessment of the microbiology of foot infections, do not in isolation establish the presence of infection. Unless the cul­tured material is obtained from deep tissue planes by surgical biopsy or percutaneous aspiration, the results of cultures must be interpreted in the clinical context.

are too complex for routine clinical use. Well- studied systems to classify the severity of infection have been developed by the Infectious Diseases Society of America (IDSA) and the International Working Group on the Diabetic Foot (IWGDF) [1, 2, 33, 34]. The schema has been broadly used since 2004 and is updated quadrennially. The IWGDF/IDSA schema classies wounds from having no infection to being severely infected. Infected wounds are then subdivided into mild, moderate, and severe infection by using the depth of a wound, presence of ischemia, presence and extent of infection, and presence of systemic toxicity (Table 20.1) [1, 2]. Increased severity in the IDSA/IWGDF classication schema (e.g., moderate and severe infection) correlates with the need for hospitalization and amputation [35, 36]. The IWGDF 2019 guideline includes an update to categorize moderate and severe infection including osteomyelitis with “(O)” after the grade number [1]. This reects the important diagnostic and treatment considerations for osteomyelitis as well as prognos­tic factors including increased risk of prolonged hospitaliza­tion and amputation when present [37, 38].

Enterobacterales, and Pseudomonas aeruginosa are the pre- dominant pathogens in these infections. Among the anaer­obes, Peptostreptococcus species, Prevotella species, and Bacteroides species are recovered frequently [52, 54–56]. Of note, Clostridium species are recovered infrequently. The reported isolation rates of anaerobes are variable across stud­ies due to varying specimen collection techniques; however, with optimal methods, these organisms can be recovered from 75 to 85% of limb-threatening infections [54]. The fre­quency of isolating anaerobic bacteria is greatest in those patients with the most severe infections, particularly those where infection involves necrotic gangrenous tissue and amputation is often required. Fetid infections suggest the presence of anaerobes; however, anaerobes including B. fra- gilis may be recovered from infections that are not particu­larly foul smelling. Hence, clinical clues beyond the major categorization of infections as non-limb-threatening or limb­threatening are not sufcient to predict the microbiology of foot infections.