Tissue concentrations after a single-dose, orally administered ofloxacin in patients with diabetic foot infections

Classification, microbiology and treatment of diabetic foot infections

Diabetic foot ulcers (DFUs) are a common complication of type-1 and type-2 diabetes. About 10-15% of patients with diabetes develop foot ulcers. A validated foot ulcer classification system that will support the development of treatment strategis is necessary for clinicians managing DFUs. More than 10 classification systems have been described by researchers. Another important aspect of the management of DFUs is the proper identification of causative pathogens that trigger infections. While conventional diagnostic methods, such as swabs, cultures and biopsies are more widely used, novel molecular techniques have been exploring bacterial identification and quantification. Knowledge of the microbial aetiologies in diabetic foot infections, and understanding of antibiotic resistance, is critical for the effective management and treatment of these infected wounds. Initial antibiotic regimens are usually selected empirically. A set of common principles may help avoid selecting either an unnecessarily broad or inappropriately narrow antibiotic treatment regimen. In this review we provide a comprehensive summary and description of classification systems of diabetic foot infections, and a comprehensive discussion of microbiology.

Update on the Role of Infection and Biofilms in Wound Healing: Pathophysiology and Treatment

BACKGROUND

Chronic wounds, and among these infected diabetic foot ulcers, are a worldwide problem. The poor treatment outcomes result in high healthcare costs, amputations, a decreased quality of life, and an increased mortality. These outcomes are influenced by several factors, including biofilm formation. A biofilm consists of pathogenic bacteria that are encased in an exopolysaccharide layer and communicate through secretion of signaling molecules. Bacteria that live in a biofilm are refractory to host responses and treatment.

METHODS

We performed a nonsystematic review of the currently published to-date medical biofilm literature. The review summarizes the evidence of biofilm in chronic wounds, the role of biofilm in wound healing, detection of biofilm, and available antibiofilm treatments. Articles containing basic science and clinical research, as well as systematic reviews, are described and evaluated. The articles have variable levels of evidence. All articles have been peer reviewed and meet the standards of evidence-based medicine.

RESULTS

Both animal and human studies have identified biofilm in chronic wounds and have suggested that healing might be influenced by its presence. A promising development in biofilm detection is rapid molecular diagnostics combined with direct microscopy. This technique, rather than classic culture, might support individualized treatment in the near future. A wide range of treatments for chronic wounds also influence biofilm formation. Several agents that specifically target biofilm are currently being researched.

CONCLUSIONS

Biofilm formation has a substantial role in chronic wounds. Several diagnostic and therapeutic methods against biofilm are currently being developed.

Antibacterial activity of moxifloxacin on bacteria associated with periodontitis within a biofilm

The activity of moxifloxacin was compared with ofloxacin and doxycycline against bacteria associated with periodontitis within a biofilm (single strain and mixed population) in vitro. MICs and minimal bactericidal concentrations (MBCs) of moxifloxacin, ofloxacin and doxycyline were determined against single strains and mixed populations in a planktonic state. Single-species biofilms of two Porphyromonas gingivalis and two Aggregatibacter actinomycetemcomitans strains and a multispecies biofilm consisting of 12 species were formed for 3 days. The minimal biofilm eradication concentrations (MBECs) were determined after exposing the biofilms to the antibacterials (0.002-512 µg ml(-1)) for 18 h, addition of nutrient broth for 3 days and subsequent subcultivation. Photographs were taken using confocal laser-scanning microscopy and scanning electron microscopy. The MICs and MBCs did not differ between ofloxacin and moxifloxacin against A. actinomycetemcomitans, whilst moxifloxacin was more active than the other tested antibacterials against anaerobes and the mixed population. The single-species biofilms were eradicated by moderate concentrations of the antibacterials, and the lowest MBECs were always found for moxifloxacin (2-8 µg ml(-1)). MBECs against the multispecies biofilms were 128, >512 and >512 µg ml(-1) for moxifloxacin, ofloxacin and doxycycline, respectively. In summary, moxifloxacin in a topical formulation may have potential as an adjunct to mechanical removal of the biofilms.

Diagnosis and management of infection in the diabetic foot

Foot infections are common in persons with diabetes mellitus. Most diabetic foot infections occur in a foot ulcer, which serves as a point of entry for pathogens. Unchecked, infection can spread contiguously to involve underlying tissues, including bone. A diabetic foot infection is often the pivotal event leading to lower extremity amputation, which account for about 60% of all amputations in developed countries. Given the crucial role infections play in the cascade toward amputation, all clinicians who see diabetic patients should have at least a basic understanding of how to diagnose and treat this problem.

Managing diabetic foot infection in India

The burden of diabetic foot complications, in terms of both physical and socioeconomical constraints, poses a heavy challenge both to the patient and the physician, especially in developing countries, where the number of people living with diabetes is increasing at an alarming rate compared with the developed world. In developing countries like India, there are specific causes and risk factors that increase the burden of diabetic foot infections (DFIs), for example, sociocultural risk factors such as barefoot walking, using improper footwear, poor knowledge of foot care practices, lack of adequate and timely access to podiatry services, and poor health care resources. Management of DFI in light of these limitations is quite a challenge to health care professionals. Several techniques and strategies are required to address this problem and should be combined with a multidisciplinary team effort to reduce the burgeoning epidemic of diabetic foot disease. This review is intended to address some of the major aspects of management of DFI in India.

2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections

Foot infections are a common and serious problem in persons with diabetes. Diabetic foot infections (DFIs) typically begin in a wound, most often a neuropathic ulceration. While all wounds are colonized with microorganisms, the presence of infection is defined by ≥2 classic findings of inflammation or purulence. Infections are then classified into mild (superficial and limited in size and depth), moderate (deeper or more extensive), or severe (accompanied by systemic signs or metabolic perturbations). This classification system, along with a vascular assessment, helps determine which patients should be hospitalized, which may require special imaging procedures or surgical interventions, and which will require amputation. Most DFIs are polymicrobial, with aerobic gram-positive cocci (GPC), and especially staphylococci, the most common causative organisms. Aerobic gram-negative bacilli are frequently copathogens in infections that are chronic or follow antibiotic treatment, and obligate anaerobes may be copathogens in ischemic or necrotic wounds. Wounds without evidence of soft tissue or bone infection do not require antibiotic therapy. For infected wounds, obtain a post-debridement specimen (preferably of tissue) for aerobic and anaerobic culture. Empiric antibiotic therapy can be narrowly targeted at GPC in many acutely infected patients, but those at risk for infection with antibiotic-resistant organisms or with chronic, previously treated, or severe infections usually require broader spectrum regimens. Imaging is helpful in most DFIs; plain radiographs may be sufficient, but magnetic resonance imaging is far more sensitive and specific. Osteomyelitis occurs in many diabetic patients with a foot wound and can be difficult to diagnose (optimally defined by bone culture and histology) and treat (often requiring surgical debridement or resection, and/or prolonged antibiotic therapy). Most DFIs require some surgical intervention, ranging from minor (debridement) to major (resection, amputation). Wounds must also be properly dressed and off-loaded of pressure, and patients need regular follow-up. An ischemic foot may require revascularization, and some nonresponding patients may benefit from selected adjunctive measures. Employing multidisciplinary foot teams improves outcomes. Clinicians and healthcare organizations should attempt to monitor, and thereby improve, their outcomes and processes in caring for DFIs.

Expert opinion on the management of infections in the diabetic foot

This update of the International Working Group on the Diabetic Foot incorporates some information from a related review of diabetic foot osteomyelitis (DFO) and a systematic review of the management of infection of the diabetic foot. The pathophysiology of these infections is now well understood, and there is a validated system for classifying the severity of infections based on their clinical findings. Diagnosing osteomyelitis remains difficult, but several recent publications have clarified the role of clinical, laboratory and imaging tests. Magnetic resonance imaging has emerged as the most accurate means of diagnosing bone infection, but bone biopsy for culture and histopathology remains the criterion standard. Determining the organisms responsible for a diabetic foot infection via culture of appropriately collected tissue specimens enables clinicians to make optimal antibiotic choices based on culture and sensitivity results. In addition to culture-directed antibiotic therapy, most infections require some surgical intervention, ranging from minor debridement to major resection, amputation or revascularization. Clinicians must also provide proper wound care to ensure healing of the wound. Various adjunctive therapies may benefit some patients, but the data supporting them are weak. If properly treated, most diabetic foot infections can be cured. Providers practising in developing countries, and their patients, face especially challenging situations.

Factors Affecting Gentamicin Penetration in Lower Extremity Ischemic Tissues With Ulcers

The aims of the study were to analyze the penetration of gentamicin in foot ulcers in patients with different severities of peripheral arterial disease (PAD) and to determine significant parameters affecting lower limb tissue concentrations. Patients undergoing debridement of a wound or an amputation procedure were included. All patients received a 120 mg or 240 mg intravenous dose of gentamicin prior to the procedure. Patients were classified according to the degree of PAD. Tissue and serum samples were collected at the time of intervention, and gentamicin concentrations were determined by fluorescence polarization immunoassay. Blood and tissue samples were taken from 61 patients, 41 males and 20 females with a mean age of 66 years. Nineteen patients had nil or borderline PAD, 9 patients had mild or moderate PAD, and 26 patients had severe PAD. Forty-eight patients had type 2 diabetes, 8 patients had type 1 diabetes, and 5 patients were nondiabetic. The concentration of gentamicin in peripheral skeletal muscle tissue was dependent on the serum concentration, degree of PAD, gender, and age. For patients with ischemic lower extremity wounds (patients with mild, moderate, and severe PAD), the concentration of gentamicin was significantly lower ( P = .010) than the concentration in nonischemic wounds, and the concentration in female patients was also significantly lower than in male patients ( P = .047). The concentration in peripheral subcutaneous tissue was 0.663 times the concentration in skeletal muscle tissue ( P < .00001). Gentamicin showed greatest penetration in male patients without PAD. For patients with severe PAD, higher doses of gentamicin may be required to achieve the same effect.

Fluoroquinolone antibiotics having the potential to interfere with fluorescence-based diagnosis

Fluorescence, both intrinsic and exogenously induced, is being used for diagnosis of abnormal tissue. Excitation wavelengths used by these methods range from 320 to 450 nm. The presence of absorbing or fluorescing drugs is rarely taken into account by practitioners of fluorescence diagnosis and has the potential to yield false-positive or false-negative results. Our aim is to quantify this potential by (1) comparing the quantum yield of fluoroquinolone antibiotics to those of known tissue fluorophores and (2) taking into account drug concentrations in the tissue during treatment. Quantum yields are determined relative to a working standard of Rhodamine 6G in ethanol. The working standard was calibrated against a fluorescein standard. We concentrated our initial efforts on (1) the fluoroquinolone antibiotics, ciprofloxacin, norfloxacin and ofloxacin and (2) the intrinsic tissue fluorophores, NADH, FAD and protoporphyrin IX. When ciprofloxacin, norfloxacin and ofloxacin were excited at wavelengths 310-390 nm, emission occurred from 350 to 650 nm with quantum yields ranging from 0.03 to 0.3. Quantum yields for intrinsic fluorophores excited at their peak absorption wavelengths were 0.02 (NADH, 340 nm), 0.035 (FAD, 450 nm) and 0.087 (protoporphyrin IX, 408 nm). A review of the literature shows that these fluoroquinolones have a large volume of distribution and can be found in high concentrations in almost every organ during a treatment regimen. The product of the drug tissue concentration and quantum yield, which we term the fluorescence effective concentration, is such that it is likely these fluoroquinolones will interfere during fluorescence diagnosis techniques.

Osteomyelitis in the diabetic foot: diagnosis and management

Neuropathic ulcerations and altered immune function place the diabetic patient at increased risk for polymicrobial osteomyelitis of the foot and ankle. The optimal method for evaluation and management of this difficult condition is controversial, and further studies are needed. Infected ulcers with exposed or palpable bone can be assumed to have underlying osteomyelitis. Although plain film should be ordered in each case, MRI is most often used for evaluation and surgical planning. Difficult cases, such as those associated with Charcot osteoarthropathy, may require labeled leukocyte scanning or bone biopsy to arrive at the diagnosis. A multidisciplinary team approach is best, allowing optimal treatment of all associated conditions that commonly affect patients with diabetes mellitus. Vascular evaluation and intervention are critical in the presence of vascular insufficiency or ischemia. Empiric, usually broad-spectrum antibiotics and meticulous local wound care may achieve remission of mild to moderately severe infections and should be included in all treatment regimens. Severe, infections, ischemia, or sepsis requires an aggressive surgical approach. Bone resection, correction of deformity, or amputation often are necessary and should be done with the goal of salvaging a functional foot.

Diagnosis and treatment of diabetic foot infections

EXECUTIVE SUMMARY: 1. Foot infections in patients with diabetes cause substantial morbidity and frequent visits to health care professionals and may lead to amputation of a lower extremity. 2. Diabetic foot infections require attention to local (foot) and systemic (metabolic) issues and coordinated management, preferably by a multidisciplinary foot-care team (A-II). The team managing these infections should include, or have ready access to, an infectious diseases specialist or a medical microbiologist (B-II). 3. The major predisposing factor to these infections is foot ulceration, which is usually related to peripheral neuropathy. Peripheral vascular disease and various immunological disturbances play a secondary role. 4. Aerobic Gram-positive cocci (especially Staphylococcus aureus) are the predominant pathogens in diabetic foot infections. Patients who have chronic wounds or who have recently received antibiotic therapy may also be infected with Gram-negative rods, and those with foot ischemia or gangrene may have obligate anaerobic pathogens. 5. Wound infections must be diagnosed clinically on the basis of local (and occasionally systemic) signs and symptoms of inflammation. Laboratory (including microbiological) investigations are of limited use for diagnosing infection, except in cases of osteomyelitis (B-II). 6. Send appropriately obtained specimens for culture before starting empirical antibiotic therapy in all cases of infection, except perhaps those that are mild and previously untreated (B-III). Tissue specimens obtained by biopsy, ulcer curettage, or aspiration are preferable to wound swab specimens (A-I). 7. Imaging studies may help diagnose or better define deep, soft-tissue purulent collections and are usually needed to detect pathological findings in bone. Plain radiography may be adequate in many cases, but MRI (in preference to isotope scanning) is more sensitive and specific, especially for detection of soft-tissue lesions (A-I). 8. Infections should be categorized by their severity on the basis of readily assessable clinical and laboratory features (B-II). Most important among these are the specific tissues involved, the adequacy of arterial perfusion, and the presence of systemic toxicity or metabolic instability. Categorization helps determine the degree of risk to the patient and the limb and, thus, the urgency and venue of management. 9. Available evidence does not support treating clinically uninfected ulcers with antibiotic therapy (D-III). Antibiotic therapy is necessary for virtually all infected wounds, but it is often insufficient without appropriate wound care. 10. Select an empirical antibiotic regimen on the basis of the severity of the infection and the likely etiologic agent(s) (B-II). Therapy aimed solely at aerobic Gram-positive cocci may be sufficient for mild-to-moderate infections in patients who have not recently received antibiotic therapy (A-II). Broad-spectrum empirical therapy is not routinely required but is indicated for severe infections, pending culture results and antibiotic susceptibility data (B-III). Take into consideration any recent antibiotic therapy and local antibiotic susceptibility data, especially the prevalence of methicillin-resistant S. aureus (MRSA) or other resistant organisms. Definitive therapy should be based on both the culture results and susceptibility data and the clinical response to the empirical regimen (C-III). 11. There is only limited evidence with which to make informed choices among the various topical, oral, and parenteral antibiotic agents. Virtually all severe and some moderate infections require parenteral therapy, at least initially (C-III). Highly bioavailable oral antibiotics can be used in most mild and in many moderate infections, including some cases of osteomyelitis (A-II). Topical therapy may be used for some mild superficial infections (B-I). 12. Continue antibiotic therapy until there is evidence that the infection has resolved but not necessarily until a wound has healed. Suggestions for the duration of antibiotic therapy are as follows: for mild infections, 12 weeks usually suffices, but some require an additional 12 weeks; for moderate and severe infections, usually 24 weeks is sufficient, depending on the structures involved, the adequacy of debridement, the type of soft-tissue wound cover, and wound vascularity (A-II); and for osteomyelitis, generally at least 46 weeks is required, but a shorter duration is sufficient if the entire infected bone is removed, and probably a longer duration is needed if infected bone remains (B-II). 13. If an infection in a clinically stable patient fails to respond to 1 antibiotic courses, consider discontinuing all antimicrobials and, after a few days, obtaining optimal culture specimens (C-III). 14. Seek surgical consultation and, when needed, intervention for infections accompanied by a deep abscess, extensive bone or joint involvement, crepitus, substantial necrosis or gangrene, or necrotizing fasciitis (A-II). Evaluating the limb's arterial supply and revascularizing when indicated are particularly important. Surgeons with experience and interest in the field should be recruited by the foot-care team, if possible. 15. Providing optimal wound care, in addition to appropriate antibiotic treatment of the infection, is crucial for healing (A-I). This includes proper wound cleansing, debridement of any callus and necrotic tissue, and, especially, off-loading of pressure. There is insufficient evidence to recommend use of a specific wound dressing or any type of wound healing agents or products for infected foot wounds. 16. Patients with infected wounds require early and careful follow-up observation to ensure that the selected medical and surgical treatment regimens have been appropriate and effective (B-III). 17. Studies have not adequately defined the role of most adjunctive therapies for diabetic foot infections, but systematic reviews suggest that granulocyte colony-stimulating factors and systemic hyperbaric oxygen therapy may help prevent amputations (B-I). These treatments may be useful for severe infections or for those that have not adequately responded to therapy, despite correcting for all amenable local and systemic adverse factors. 18. Spread of infection to bone (osteitis or osteomyelitis) may be difficult to distinguish from noninfectious osteoarthropathy. Clinical examination and imaging tests may suffice, but bone biopsy is valuable for establishing the diagnosis of osteomyelitis, for defining the pathogenic organism(s), and for determining the antibiotic susceptibilities of such organisms (B-II). 19. Although this field has matured, further research is much needed. The committee especially recommends that adequately powered prospective studies be undertaken to elucidate and validate systems for classifying infection, diagnosing osteomyelitis, defining optimal antibiotic regimens in various situations, and clarifying the role of surgery in treating osteomyelitis (A-III).

Tissue and serum levofloxacin concentrations in diabetic foot infection patients

OBJECTIVES

Levofloxacin has a high bioavailability and a broad antibacterial spectrum which covers the common pathogens found in acute and chronic diabetic foot infections. The purpose of our study was to determine the serum and tissue concentrations of levofloxacin when administered orally in patients with infected diabetic foot ulcers and to compare these values with microbiological findings.

PATIENTS AND METHODS

Ten outpatients with diabetes and ulcerations of the lower extremity were included. All patients received oral levofloxacin therapy at a dose of 500 mg once daily. Wound tissue and serum samples were collected and levofloxacin concentrations determined by HPLC with fluorescence detection. Additionally, microbiological cultures were performed from swabs and debrided wound tissue, both before and after treatment. MICs of levofloxacin for all bacterial isolates were determined using the Etest.

RESULTS

Following oral treatment with levofloxacin for an average of 10 +/- 3.8 days, all patients received debridement at the affected limbs. The levofloxacin concentrations in necrotic wound tissue were between 2.33-23.23 mg/kg and between 0.12-6.41 mg/L in serum. Tissue-to-serum ratios of levofloxacin concentrations for each patient were >1.0. The MIC values for all 17 initially isolated bacteria were < or = 2 mg/L. In half of our patients, fluoroquinolones were one of the few oral monotherapy options where the spectrum covered all initially isolated pathogens.

CONCLUSION

Our data showed good tissue penetration of levofloxacin in diabetic foot ulcers. In combination with adequate surgical debridement, levofloxacin seems well suited to the treatment of skin structure infections of diabetics caused by susceptible organisms.

Diagnosis and treatment of diabetic foot infections

Diabetic foot infections frequently cause morbidity, hospitalization, and amputations. Gram-positive cocci, especially staphylococci and also streptococci, are the predominant pathogens. Chronic or previously treated wounds often yield several microbes on culture, including gram-negative bacilli and anaerobes. Optimal culture specimens are wound tissue taken after debridement. Infection of a wound is defined clinically by the presence of purulent discharge or inflammation; systemic signs and symptoms are often lacking. Only infected wounds require antibiotic therapy, and the agents, route, and duration are predicated on the severity of infection. Mild to moderate infections can usually be treated in the outpatient setting with oral agents; severe infections require hospitalization and parenteral therapy. Empirical therapy must cover gram-positive cocci and should be broad spectrum for severe infections. Definitive therapy depends on culture results and the clinical response. Bone infection is particularly difficult to treat and often requires surgery. Several adjuvant agents may be beneficial in some cases.

The effect of diabetes and severe ischaemia on the penetration of ceftazidime into tissues of the limb

AIMS

To determine the effect of diabetes and of different degrees of ischaemia on the penetration of ceftazidime into different tissues.

METHODS

Sixteen patients (10 with diabetes mellitus) undergoing lower extremity amputation for severe ischaemia (in 12 in combination with infection), received 2000 mg ceftazidime intravenously as a bolus 30 min prior to the operation. Skin perfusion was determined by transcutaneous oxygen pressure measurements (TcPO2) on the dorsal side of the midfoot. After amputation bone, skin and muscle samples were obtained from the forefoot, midfoot and proximal tibia. Tissue and plasma concentrations were determined by HPLC. The tissue concentrations were corrected for blood contamination.

RESULTS

No differences were observed in skin, muscle or bone ceftazidime levels between diabetic and non-diabetic patients. Multiple regression analysis suggested that tissue perfusion was a major determinant of skin and bone ceftazidime concentrations, predicting 40-47% of the ceftazidime concentrations at several biopsy sites.

CONCLUSIONS

The present study suggests that tissue perfusion is the major determinant of the penetration of a third generation cephalosporin into the tissues of the ischaemic (diabetic) foot. Diabetes alone however, has no major effects upon this penetration.

Pharmacotherapy of lower limb diabetic ulcers

OBJECTIVE

To discuss the pathophysiology, microbiology, and pharmacotherapy of lower extremity (LE) diabetic ulcers.

DATA SOURCES

A MEDLINE search from 1966 to April 1999 was conducted. The search was limited to humans and English-language journals. Key search words included "diabetic ulcer," "fluoroquinolones," "beta-lactam," "hyperbaric oxygen," "diabetes mellitus," "diabetic foot," and "growth factor."

STUDY SELECTION

Randomized and nonrandomized studies were selected for review. Results of randomized, placebo-controlled studies were emphasized more than nonrandomized results.

DATA SYNTHESIS

LE ulcers are a common cause of hospitalization, and cause significant morbidity and mortality. Staphylococcus aureus is the most common pathogen in non-limb-threatening infections; Gram-negative bacteria and anaerobes are most prevalent in limb-threatening and life-threatening infections. Oral antibiotic therapy may be used in non-limb-threatening infections, if adequate response is achieved in 24-48 hours; otherwise, intravenous antibiotics should be started. Intravenous antibiotics should be the initial therapy for limb-threatening or life- threatening ulcers. Antimicrobial therapy of at least 10-14 days has been effective in treating LE ulcers in the absence of osteomyelitis. Growth factors offer another treatment alternative, although only becaplermin is currently approved for diabetic ulcers.

CONCLUSION

Antibiotic therapy has been effective for the treatment of LE diabetic ulcers. However, further studies are required to identify optimal antibiotics and dosage regimens. Growth factors may have a role but additional research is needed to determine when best to initiate this therapy.

Evidence-based antibiotic therapy of diabetic foot infections

In addition to proper cleansing, debridement and local wound care, foot infections in diabetic patients require carefully selected antibiotic therapy. Serious infections necessitate hospitalization for initial parenteral broad-spectrum antibiotic therapy. Appropriately selected patients with mild infections can be treated as outpatients with oral (or even topical) therapy. Initial antibiotic selection is usually empirical, but definitive therapy may be modified based on culture results and the clinical response. Therapy should nearly always be active against staphylococci and streptococci, with broader-spectrum agents indicated if Gram-negative or anaerobic organisms are likely. In infected foot tissues levels of most antibiotics, except fluoroquinolones, are often subtherapeutic. The duration of therapy ranges from a week (for mild soft tissue infections) to over 6 weeks (for osteomyelitis). Recent antibiotic trials have shown that several intravenously or orally administered agents are effective in treating these infections, with no one agent or combination emerging as optimal. Suggested regimens based on the severity of infection are provided.

A Current Approach to Diabetic Foot Infections

Foot infections are a common, complex, and serious problem in diabetic patients. Infections usually begin in foot ulcers, which are associated with neuropathy, vasculopathy, and various metabolic disturbances. These infections are potentially limb and sometimes life threatening. Etiologic agents are usually aerobic gram-positive cocci, but chronic or serious infections often contain gram-negative rods and anaerobes. Chronic infections can lead to contiguous bone infection. Diagnosing osteomyelitis may require imaging studies (especially magnetic resonance imaging) and occasionally bone biopsy. In addition to proper cleansing, debridement, and local wound care, diabetic foot infections require carefully selected antibiotic therapy. Serious infections necessitate hospitalization for initial parenteral broad-spectrum antibiotic therapy, but appropriately selected patients with mild infections can be treated as outpatients with oral (or even topical) agents. Initial antibiotic selection is usually empiric; modifications may be needed based on the results of properly obtained cultures and the clinical response. Therapy should be active against staphylococci and streptococci, with broader-spectrum agents indicated if polymicrobial infection is likely. Levels of most antibiotics, except fluoroquinolones, are often subtherapeutic in infected foot tissues. The duration of therapy ranges from a week (for mild soft tissue infections) to over 6 weeks (for osteomyelitis). No single antibiotic agent or combination has proven to be optimal. With appropriate local, surgical, and antimicrobial therapy, most diabetic foot infections can now be successfully treated.