Piperacillin/tazobactam therapy for diabetic foot infection

Clinical efficacy of piperacillin/tazobactam in the treatment of complicated skin and soft tissue infections

INTRODUCTION

Complicated skin and soft tissue infections (cSSTIs) are skin and soft tissue infections (SSTIs) that involve deep soft tissue. cSSTIs often require surgical intervention and/or hospitalization. cSSTIs are associated with significant mortality and morbidity, and carry a significant burden on health care systems. Piperacillin/tazobactam has been regarded as a standard treatment for cSSTIs because of its antibiotic spectrum, safety and clinical efficacy. Several antibiotics, as compared to piperacillin/tazobactam, have been evaluated in the treatment of cSSTIs. Areas covered: This review summarizes randomized controlled trials (RCTs) evaluating the clinical efficacy of piperacillin/tazobactam for the treatment of cSSTIs. Expert opinion: Piperacillin/tazobactam, which covers most causative organisms in cSSTIs, is the drug of choice for the treatment of cSSTIs. Other options such as ertapenem and moxifloxacin may be reasonable where multiple daily dosing or intravenous administration is inappropriate. But in general, they should be avoided as an empirical treatment because of their highly association with resistant bacteria, which are becoming a global threat. Therefore, piperacilin/tazobactam is appropriate as an empirical therapy for the treatment of SSTIs and should be de-escalated as soon as causative organisms are identified, their drug-sensitivity results are available, and clinical condition becomes stable.

Pharmacotherapy of Diabetic Foot Ulcers

The incidence of diabetes and diabetic foot ulcers is increasing significantly in the United States. These ulcers and infections are the result of long-term complications of diabetes including neuropathy and vascular insufficiency. These infections can be classified into mild, limb threatening, and life threatening. This classification helps clarify the expected organisms involved and consequently appropriate, empiric antibiotic therapy. Mild infections are generally caused by Gram-positive organisms and can usually be treated as an outpatient with oral antibiotics. Antibiotics used for mild infections-include cephalexin, clindamycin, and amoxicillin/ clavulanate. Moderate to severe or limb-threatening infections are usually polymicrobial and frequently require hospitalization. These infections are typically treated with more broad-spectrum antibiotics including ampicillin/sulbactam, imipenem, or the combination of clindamycin and a fluoroquinolone. Severe or life-threatening infections also require broad-spectrum antibiotics. Other therapeutic options besides antibiotics include growth factors, such as becaplermin, and various skin substitutes.

Foot infections in diabetes (DFIs) in the out-patient setting: an Italian multicentre observational survey

AIMS

To conduct a multicentre observational study to describe management of foot infections in diabetes in the out-patient setting in Italy.

PATIENTS AND METHODS

Ten centres equally distributed nationwide were asked to collect, by means of a spreadsheet (Access/Excel Microsoft program), data concerning 30 consecutive diabetic patients with foot infections deemed suitable for antibiotic treatment in the out-patient setting. Centres with > or = 5 years' experience of out-patient management were selected. Data from 271 consecutive patients treated as out-patients were collected and analysed by the central coordinator. Statistical analysis was performed using the SPSS statistical software package.

RESULTS

Lesions were mainly located at the toes and midfoot (33.6 and 30.2%, respectively); 63 (23.2%) patients had multiple ulcers. Seventy (25.8%) patients also had concomitant osteomyelitis. Three hundred and four pathogens, including Gram-positive and Gram-negative aerobes and anaerobes, were isolated in 219/271 patients (80.8%) by culturing debrided tissue (71.2%) or purulent material (28.8%). Infections were polymicrobial in 33.8% of patients. The most common pathogens were Staphylococcus aureus (27.3%) and Pseudomonas spp. (20.4%); enterobacteriaceae, enterococci, streptococci and anaerobes accounted for 11.5, 7.6, 6.9 and 1.9%, respectively. Antibiotics were frequently administered by parenteral route and frequently in combination. Piperacillin/tazobactam was the parenteral antibiotic most frequently utilized (21.1%). Cure/improvement was observed in 93.4% of patients.

CONCLUSIONS

Foot ulcers in diabetes are common and serious; the aetiology is often polymicrobial, often including S. aureus and Pseudomonas spp. Treatment in the out-patient setting is safe and effective, and penicillins together with beta-lactamase inhibitors and fluoroquinolones are the most frequent choice.

Bacteriology of moderate-to-severe diabetic foot infections and in vitro activity of antimicrobial agents

As part of a United States-based multicenter clinical trial, conducted from 2001 to 2004, that compared ertapenem to piperacillin-tazobactam for the treatment of moderate-to-severe diabetic foot infections (DFIs), we obtained 454 pretreatment specimens from 433 patients. After debridement, the investigators collected wound specimens, mostly by curettage or biopsy, and sent them to the R. M. Alden Research Laboratory for aerobic and anaerobic culture. Among the 427 positive cultures, 83.8% were polymicrobial, 48% grew only aerobes, 43.7% had both aerobes and anaerobes, and 1.3% had only anaerobes. Cultures yielded a total of 1,145 aerobic strains and 462 anaerobic strains, with an average of 2.7 organisms per culture (range, 1 to 8) for aerobes and 2.3 organisms per culture (range, 1 to 9) for anaerobes. The predominant aerobic organisms were oxacillin-susceptible Staphylococcus aureus (14.3%), oxacillin-resistant Staphylococcus aureus (4.4%), coagulase-negative Staphylococcus species (15.3%), Streptococcus species (15.5%), Enterococcus species (13.5%), Corynebacterium species (10.1%), members of the family Enterobacteriaceae (12.8%), and Pseudomonas aeruginosa (3.5%). The predominant anaerobes were gram-positive cocci (45.2%), Prevotella species (13.6%), Porphyromonas species (11.3%), and the Bacteroides fragilis group (10.2%). Pure cultures were noted for 20% of oxacillin-resistant Staphylococcus aureus cultures, 9.2% of Staphylococcus epidermidis cultures, and 2.5% of P. aeruginosa cultures. Two or more species of Staphylococcus were present in 13.1% of the patients. Ertapenem and piperacillin-tazobactam were each active against >98% of the enteric gram-negative rods, methicillin-sensitive S. aureus, and anaerobes. Among the fluoroquinolones, 24% of anaerobes, especially the gram-positive cocci, were resistant to moxifloxacin; 27% of the gram-positive aerobes but only 6% of the members of the family Enterobacteriaceae were resistant to levofloxacin. Moderate-to-severe DFIs are typically polymicrobial, and almost half include anaerobes. Our antibiotic susceptibility results can help to inform therapeutic choices.

An infectious disease update on antibiotics: emerging resistance

Podiatric physicians often encounter infectious processes in the lower extremity in inpatient and outpatient settings. Bacterial resistance to antibiotics is a growing concern for clinicians treating these infections, especially in complex patients who have immune compromise such as diabetes. Although a number of antibiotic options are available for the treatment of lower-extremity soft tissue and bone infections, a careful examination of bacterial susceptibilities, drug resistance, and treatment efficacy can result in better patient care and limb salvage.

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).

Ertapenem versus piperacillin/tazobactam for diabetic foot infections (SIDESTEP): prospective, randomised, controlled, double-blinded, multicentre trial

BACKGROUND

Diabetic foot infections are a common and serious problem, yet few randomised trials of adequate quality have compared the efficacy of the various antibiotic regimens available for their treatment. Our aim was to assess the efficacy and safety of ertapenem versus piperacillin/tazobactam for foot infections.

METHODS

We did a randomised, double-blinded, multicentre trial in adults (n=586) with diabetes and a foot infection classified as moderate-to-severe and requiring intravenous antibiotics. We assigned patients intravenous ertapenem (1 g daily; n=295) or piperacillin/tazobactam (3.375 g every 6 h; n=291) given for a minimum of 5 days, after which oral amoxicillin/clavulanic acid (875/125 mg every 12 h) could be given for up to 23 days. Investigators retained the option to administer vancomycin to patients in either group to ensure adequate coverage for potentially antibiotic resistant Enterococcus spp and meticillin-resistant Staphylococcus aureus (MRSA). Our primary outcome was the proportion of patients with a favourable clinical response (cure or improvement) on the day that intravenous antibiotic was discontinued. Analyses were by an evaluable-patient only approach. This study is registered with , number NCT00229112.

FINDINGS

Of the 576 patients treated, 445 were available for assessment at the end of intravenous therapy. Both baseline characteristics and favourable clinical response rates were similar for the 226 who received ertapenem and the 219 who received piperacillin/tazobactam (94%vs 92%, respectively; between treatment difference 1.9%, 95% CI -2.9 to 6.9). Rates of favourable microbiological responses (eradication rates and clinical outcomes, by pathogen) and adverse events did not differ between groups.

INTERPRETATION

Clinical and microbiological outcomes for patients treated with ertapenem were equivalent to those for patients treated with piperacillin/tazobactam, suggesting that this once-daily antibiotic should be considered for parenteral therapy of diabetic foot infections, when deemed appropriate.

An open-label, randomized study comparing efficacy and safety of intravenous piperacillin/tazobactam and ampicillin/sulbactam for infected diabetic foot ulcers

BACKGROUND

Soft tissue and bone infections of the lower limb continue to be a frequent and serious complication in patients with diabetes mellitus. The best choice of antimicrobial for the empiric treatment of moderate to severe diabetic foot infections has not been established clearly.

METHODS

We conducted a prospective, randomized, open-label, multicenter trial comparing piperacillin/tazobactam (P/T) (4 g/0.5 g q8h) and ampicillin/sulbactam (A/S) (2 g/1 g q6h) as a parenteral treatment for 314 adult patients with moderate-to-severe infected diabetic foot ulcers. Patients with polymicrobial infections involving methicillin-resistant Staphylococcus aureus also received vancomycin 1 g q12h.

RESULTS

Clinical efficacy rates (cure or improvement) were statistically equivalent overall (81% for P/T vs. 83.1% for A/S), and median duration of treatment was similar in the clinically evaluable populations (nine days for P/T, 10 days for A/S). Drug-related adverse events for both study drugs were comparable in frequency and type.

CONCLUSIONS

Although both study drugs provide safe and effective empiric treatment for moderate-to-severe infected diabetic foot ulcers, piperacillin/tazobactam has the advantage of covering Pseudomonas aeruginosa (bacteriologic success rate of 85.7%), the most commonly isolated gram-negative pathogen in this study.

A systematic approach to diabetic foot infections

Foot infection is the most common reason for hospitalization and subsequent lower extremity amputation among persons with diabetes. Foot ulceration caused by diabetic neuropathy, trauma, and peripheral vascular disease can lead to a limbor life-threatening infection. The optimum treatment of these potentially devastating conditions depends on a multidisciplinary approach that addresses the related or underlying disorders and thus ensures proper wound healing and a positive outcome. In addition to antibiotic therapy, severe soft-tissue or bone infections may necessitate surgical treatment, including drainage, débridement, and vascular reconstruction. Initial (empiric) antibiotic therapy should provide coverage against staphylococci and streptococci and should be revised according culture results. Antibiotic therapy is not indicated in clinically noninfected wounds. The duration of antibiotic treatment can range from 1 week for mild infections to 6 weeks or more for residual osteomyelitis and severe deep tissue infections. Aggressive (and sometimes repeated or staged) surgical intervention and appropriate antibiotic therapy can reduce the likelihood of a major amputation and the duration of hospitalization.

Antimicrobial interventions for the management of diabetic foot infections

Foot infections are the most common cause of hospitalisations and amputations in diabetic patients. They occur after skin ulcers or trauma in patients with peripheral neuropathy, sometimes together with vascular disease. Narrow-spectrum antibiotic agents should be prescribed for minor recent infections, and broader-spectrum agents for severe or chronic infections. When indicated, antibiotic therapy should be started early and be tailored to the individual patient. Diabetic foot osteomyelitis is a particularly controversial condition, especially regarding the need for reliable cultures, the type and duration of treatment, and the role of surgery. Recent data indicates that a medical approach might be effective and could reduce foot amputations among diabetic patients. Interdisciplinary cooperation with infectious disease specialists and orthopaedic surgeons should be considered in such situations.

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.

Incidence of Neutropenia during Treatment of Bone-Related Infections with Piperacillin-Tazobactam

Of 41 patients with bone-related infections who were treated for > or =10 days with piperacillin-tazobactam, 14 (34%) developed neutropenia. Cumulative doses of piperacillin administered to neutropenic patients were higher than those administered to nonneutropenic ones (330 vs. 237 g; P=.008), and an inverse correlation was detected between the absolute neutrophil count at the end of treatment and the cumulative dose of piperacillin (r=-0.47, P=.002). Moreover, the incidence of piperacillin-tazobactam-induced neutropenia increased with an increase in the cumulative dose of piperacillin: 0% of patients in the first quartile of cumulative piperacillin doses, 33.3% in the second quartile, 40% in the third quartile, and 66.7% in the fourth quartile.

Diabetic foot infections and antibiotic therapy

Diabetic foot infections are associated with high morbidity and mortality rates as well as significant financial impact on the health care system. Improved patient outcomes and intelligent use of resources should determine the selection of diagnostic procedures and the therapeutic modalities used. Diabetic patients who develop lower extremity infections require a multidisciplinary approach in the management of their infections and other disorders. Aggressive surgical debridement and appropriate and adequate antibiotic therapy are necessary to successfully treat severe foot infections and permit faster recovery.

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.