Pseudomonal Diabetic Foot Infections: Vive la Différence?

Objective

To assess the outcomes of diabetic foot infections (DFIs) due to Pseudomonas aeruginosa.

Patients and Methods

From April 24, 2013 to July 31, 2016, we analyzed data from patients prospectively enrolled in our clinical pathway of DFIs, comparing those with infection due to Pseudomonas with those without infection due to Pseudomonas.

Results

Overall, we assessed 1018 cases of DFIs: 392 with osteomyelitis and 626 with only soft tissue infections. The prevalence of P aeruginosa in deep wound cultures was 10% (104/1018); of the 1018 cultures, 22 were monomicrobial, 82 were polymicrobial, and 46 were with osteomyelitis. Overall, the patients were treated with a median of 1 surgical debridement and a total of 20 days of antibiotic therapy. In a comparison of crude groups, the proportion of clinical failures was significantly higher with Pseudomonas than with other pathogens (36/104 [35%] vs 218/914 [24%], respectively; P=.02). A multivariate analysis showed that pseudomonal DFIs did not recur more often than nonpseudomonal DFIs (hazard ratio, 1.0; 95% confidence interval, 0.6-1.7). Among the 104 cases of pseudomonal DFIs, there was no association between failure of treatment and the total duration of antibiotic therapy, duration of intravenous therapy, duration of combined antibiotic therapy with more than 1 agent, or duration of oral (fluoroquinolone) therapy. Among 15 cases of pseudomonal recurrence, 2 (13%) developed resistance to the antibiotic agent used for the index episode.

Conclusion

For DFIs caused by P aeruginosa, other than choosing an antibiotic agent that is active against the organism, it does not appear necessary to treat with a different therapeutic regimen compared with the treatment of nonpseudomonal DFIs. There is no difference!

Is routine measurement of the serum C-reactive protein level helpful during antibiotic therapy for diabetic foot infection?

Clinicians frequently monitor serum C-reactive protein (CRP) levels during therapy for diabetic foot infections (DFIs), but evidence supporting this is unclear. Using a database from prospective controlled DFI trials, with fixed duration of antibiotic therapy, we correlated the CRP levels at study enrolment and at end of therapy (EOT). Among 159 DFI episodes, 93 involved the bone and 66 the soft tissues. Overall, treatment cured 122 infections (77%), while 37 episodes (23%) recurred after a median of 53 days. The median CRP in the groups with cure versus failure differed minimally at enrolment (median 67 vs. 81 mg/L) or EOT (7 vs. 10 mg/L). Similarly, there was negligible difference in the percentage of CRP levels that normalized at EOT (39% vs. 35%). In our prospective cohorts, a blunt iterative monitoring of CRP during DFI treatment, without correlation with clinical findings, failed to predict treatment failures.

X-Ray Versus Magnetic Resonance Imaging in Diabetic Foot Osteomyelitis: A Clinical Comparison

OBJECTIVE

Radiographic imaging is an important diagnostic tool in diabetic foot osteomyelitis (DFO). It is unknown whether DFO cases diagnosed with conventional X-ray versus positive Magnetic Resonance Imaging (MRI) differ regarding epidemiology and treatment outcome. Theoretically, signs of inflammation on MRI without bone lesions might be easier to treat.

METHODS

Our clinical pathway for diabetic foot infections discourages the use of MRI for the diagnosis of DFO. We compared the epidemiology and therapy of non-amputated DFO with positive features on conventional X-ray, MRI, or both. Radiology specialists interpreted the images. The intraoperative aspect of bone during amputation and the results of bone cultures were considered the gold standard for DFO diagnosis.

RESULTS

We prospectively followed 390 DFO episodes in 186 adult patients for a median of 2.9 years and performed 318 conventional X-rays (median costs 100 Swiss Francs; 100 US$) and 47 (47/390; 12%) MRI scans (median 800 Swiss Francs; 800 US $). Among them, 18 episodes were associated with positive MRI findings but lacked bone lesions on X-ray. After debridement, the median duration of systemic antibiotics was 28 days for MRI-only episodes and 30 days for X-ray-positive cases (Wilcoxonranksum- test; p=0.26). The corresponding median numbers of surgical debridements were 1 and 1; and recurrence was witnessed in 25% and 28%, respectively. In multivariate logistic regression analysis, MRI-only episodes did not alter the remission rate (odds ratio 0.5, 95%CI 0.1-5.2).

CONCLUSION

According to our clinical pathway, DFO episodes with positive MRI findings only did not differ epidemiologically from the remaining DFO cases and did not influence the choice of therapy nor remission rate.

Three versus six weeks of antibiotic therapy for diabetic foot osteomyelitis: A prospective, randomized, non-inferiority pilot trial

BACKGROUND

In patients with diabetic foot osteomyelitis (DFO) who underwent surgical debridement, we investigated whether a short (3 weeks), compared with a long (6 weeks) duration of systemic antibiotic treatment is associated with non-inferior results for clinical remission and adverse events (AE).

METHODS

In this prospective, randomized, non-inferiority, pilot trial, we randomized (allocation 1:1), patients with DFO after surgical debridement to either a 3-week or a 6-week course of antibiotic therapy. The minimal duration of follow-up after end of therapy was two months. We compared outcomes using Cox regression and non-inferiority analyses (25% margin, power 80%).

RESULTS

Among 93 enrolled patients (18% females; median age 65 years), 44 were randomized to the 3-week arm and 49 to the 6-week arm. The median number of surgical debridement was 1 (range, 0-2 interventions). In the intention-to-treat (ITT) population, remission occurred in 37 (84%) of the patients in the 3-week arm compared to 36 (73%) in the 6-week arm (p=0.21). The number of AE was similar in the two study arms (17/44 vs. 16/49; p=0.51), as were the remission incidences in the per-protocol (PP) population (33/39 vs. 32/43; p=0.26). In multivariate analysis, treatment with the shorter antibiotic course was not significantly associated with remission (for the ITT population, hazard ratio 1.1, 95%CI 0.6-1.7; for the PP population hazard ratio 0.8, 95%CI 0.5-1.4).

CONCLUSIONS

In this randomized, controlled pilot trial, a post-debridement systemic antibiotic therapy course for DFO of 3-weeks gave similar (and statistically non-inferior) incidences of remission and AE to a course of 6 weeks.

Characterization of Proangiogenic Monocytes from Blood in Patients with Chronic Ischemic Diabetic Foot Ulcers and Controls

Many persons with diabetes mellitus have limb ischemia, which is a major clinical problem. A subset of human monocytes that expresses TIE-2 may enhance neovascularization. We performed 179 phlebotomies on 142 patients (or donors), including 61 patients/donors without diabetes or ischemia (controls), 39 diabetic nonischemic patients (controls), and 42 diabetic patients with severe limb ischemia requiring amputation. We compared these groups for the presence of TIE-2-positive proangiogenic monocytes. The proportion of proangiogenic monocytes in the venous blood (on hospital admission) was significantly increased in diabetic patients without ischemia (9.22% ± 1.19%), compared to controls (6.53% ± 0.58%) or ischemic diabetic patients (5.44% ± 0.56%) (P < 0.05). In this pilot evaluation, we succeeded in extracting potential proangiogenic TIE-2 monocytes from the blood of diabetic patients without ischemia, but less in patients with ischemia. The implications for therapeutic neoangiogenesis require further studies.

Oral amoxicillin-clavulanate for treating diabetic foot infections

AIM

To assess amoxicillin-clavulanate (AMC) for the oral therapy of diabetic foot infections (DFIs), especially for diabetic foot osteomyelitis (DFO).

METHODS

We performed a retrospective cohort analysis among 794 DFI episodes, including 339 DFO cases.

RESULTS

The median duration of antibiotic therapy after surgical debridement (including partial amputation) was 30 days (DFO, 30 days). Oral AMC was prescribed for a median of 20 days (interquartile range, 12-30 days). The median ratio of oral AMC among the entire antibiotic treatment was 0.9 (interquartile range, 0.7-1.0). After a median follow-up of 3.3 years, 178 DFIs (22%) overall recurred (DFO, 75; 22%). Overall, oral AMC led to 74% remission compared with 79% with other regimens (χ² -test; P = 0.15). In multivariate analyses and stratified subgroup analyses, oral AMC resulted in similar clinical outcomes to other antimicrobial regimens, when used orally from the start, after an initial parenteral therapy, or when prescribed for DFO.

CONCLUSIONS

Oral AMC is a reasonable option when treating patients with DFIs and DFOs.

Stopping antibiotics after surgical amputation in diabetic foot and ankle infections-A daily practice cohort

OBJECTIVE

The appropriate duration of antibiotic therapy for diabetic foot infections (DFI) after surgical amputations in toto is debated. There are discrepancies worldwide.

METHODS

Using a clinical pathway for adult DFI patients (retrospective cohort analysis), we conducted a cluster-controlled Cox regression analysis. Minimum follow-up was 2 months.

RESULTS

We followed 482 amputated DFI episodes for a median of 2.1 years after the index episode. The DFIs predominately affected the forefoot (n = 433; 90%). We diagnosed osteomyelitis in 239 cases (239/482; 50%). In total, 47 cases (10%) were complicated by bacteremia, 86 (18%) by abscesses and 139 (29%) presented with cellulitis. Surgical amputation involved the toes (n = 155), midfoot (280) and hindfoot (47). Overall, 178 cases (37%) required revascularization. After amputation, the median duration of antibiotic administration was 7 days (interquartile range, 1-16 days). In 109 cases (25%), antibiotics were discontinued immediately after surgery. Overall, clinical failure occurred in 90 DFIs (17%), due to the same pathogens in only 38 cases. In multivariate analysis, neither duration of total postsurgical antibiotic administration (HR 1.0, 95% CI 0.99-1.01) nor immediate postoperative discontinuation altered failure rate (HR 0.9, 0.5-1.5).

CONCLUSION

According to our clinical pathway, we found no benefit in continuing postsurgical antibiotic administration in routine amputation for DFI. In the absence of residual infection (ie, resection at clear margins), antibiotics should be discontinued.

Remission in diabetic foot infections: Duration of antibiotic therapy and other possible associated factors

AIM

To determine the most appropriate duration of antibiotic therapy for diabetic foot infections (DFIs).

METHODS

Using a clinical pathway for adult patients with DFIs (retrospective cohort analysis), we created a cluster-controlled Cox regression model to assess factors related to remission of infection, emphasizing antibiotic-related variables. We excluded total amputations as a result of DFI and DFI episodes with a follow-up time of <2 months.

RESULTS

Among 1018 DFI episodes in 482 patients, we identified 392 episodes of osteomyelitis, 626 soft tissue infections, 246 large abscesses, 322 episodes of cellulitis and 335 episodes of necrosis; 313 cases involved revascularization. Patients underwent surgical debridement for 824 episodes (81%), of which 596 (59%) required amputation. The median total duration of antibiotic therapy was 20 days. After a median follow-up of 3 years, 251 of the episodes (24.7%) were followed by ≥1 additional episode(s). Comparing patients with and without additional episodes, risk of recurrence was lower in those who underwent amputation, had type 1 diabetes, or underwent revascularization. On multivariate analysis including the entire study population, risk of remission was inversely associated with type 1 diabetes (hazard ratio [HR] 0.3, 95% confidence interval [CI] 0.2-0.6). Neither duration of antibiotic therapy nor parenteral treatment affected risk of recurrence (HR 1.0, 95% CI 0.99-1.01 for both). Similarly, neither >3 weeks versus <3 weeks of therapy, nor >1 week versus <1 week of intravenous treatment affected recurrence. In stratified analyses for both soft tissue DFIs or osteomyelitis separately, we did not observe associations of antibiotic duration with microbiological or clinical recurrences of DFI. The HRs were 1.0 (95% CI 0.6-1.8) for an antibiotic duration >3 weeks overall and 0.6 (95% CI 0.2-1.3) for osteomyelitis cases only. Plotting of duration of antibiotic therapy failed to identify any optimal threshold for preventing recurrences.

CONCLUSIONS

Our analysis found no threshold for the optimal duration or route of administration of antibiotic therapy to prevent recurrences of DFI. These limited data might support possibly shorter treatment duration for patients with DFI.

A randomized, controlled study to investigate the efficacy and safety of a topical gentamicin-collagen sponge in combination with systemic antibiotic therapy in diabetic patients with a moderate or severe foot ulcer infection

BACKGROUND

An adjunctive topical therapy with gentamicin-sponges to systemic antibiotic therapy might improve the healing of infected diabetic foot ulcers (DFUI).

METHODS

Single-center, investigator-blinded pilot study, randomizing (1:1) the gentamicin-sponge with systemic antibiotic versus systemic antibiotics alone for patients with DFUI.

RESULTS

We included 88 DFUI episodes with 43 patients in the gentamicin-sponge arm and 45 in the control arm. Overall, 64 (64/88; 73%) witnessed total clinical cure, 13 (15%) significant improvement, and 46 (52%) showed total eradication of all pathogens at the final visit. Regarding final clinical cure, there was no difference in favour of the gentamicin-sponges (26/45 vs. 31/43; p = 0.16). However, the gentamicin-sponge arm tended to a more rapid healing. In multivariate analysis adjusting for the case-mix, the variable "gentamicin-sponge" was not significantly associated with "cure and improvement". Gentamicin-sponges were very well tolerated, without any attributed adverse events.

CONCLUSIONS

The gentamicin-sponge was very well tolerated, but did not significantly influence overall cure.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT01951768 ). Date 2 April 2013.

A randomized controlled trial of the safety and efficacy of a topical gentamicin-collagen sponge in diabetic patients with a mild foot ulcer infection

Objectives

The initial phase of infection of a foot ulcer in a person with diabetes is often categorized as mild. Clinicians usually treat these infections with antimicrobial therapy, often applied topically. Some experts, however, believe that mild diabetic foot ulcer infections will usually heal with local wound care alone, without antimicrobial therapy or dressings.

Methods

To evaluate the potential benefit of treatment with a topical antibiotic, we performed a single-center, investigator-blinded pilot study, randomizing (1:1) adult patients with a mild diabetic foot ulcer infection to treatment with a gentamicin-collagen sponge with local care versus local care alone. Systemic antibiotic agents were prohibited.

Results

We enrolled a total of 22 patients, 11 in the gentamicin-collagen sponge arm and 11 in the control arm. Overall, at end of therapy, 20 (91%) patients were categorized as achieving clinical cure of infection, and 2 (9%) as significant improvement. At the final study visit, only 12 (56%) of all patients achieved microbiological eradication of all pathogens. There was no difference in either clinical or microbiological outcomes in those who did or did not receive the gentamicin-collagen sponge, which was very well tolerated.

Conclusion

The results of this pilot trial suggest that topical antibiotic therapy with gentamicin-collagen sponge, although very well tolerated, does not appear to improve outcomes in mild diabetic foot ulcer infection.

A randomized controlled trial of the safety and efficacy of a topical gentamicin-collagen sponge in diabetic patients with a mild foot ulcer infection

Objectives:

The initial phase of infection of a foot ulcer in a person with diabetes is often categorized as mild. Clinicians usually treat these infections with antimicrobial therapy, often applied topically. Some experts, however, believe that mild diabetic foot ulcer infections will usually heal with local wound care alone, without antimicrobial therapy or dressings.

Methods:

To evaluate the potential benefit of treatment with a topical antibiotic, we performed a single-center, investigator-blinded pilot study, randomizing (1:1) adult patients with a mild diabetic foot ulcer infection to treatment with a gentamicin–collagen sponge with local care versus local care alone. Systemic antibiotic agents were prohibited.

Results:

We enrolled a total of 22 patients, 11 in the gentamicin–collagen sponge arm and 11 in the control arm. Overall, at end of therapy, 20 (91%) patients were categorized as achieving clinical cure of infection, and 2 (9%) as significant improvement. At the final study visit, only 12 (56%) of all patients achieved microbiological eradication of all pathogens. There was no difference in either clinical or microbiological outcomes in those who did or did not receive the gentamicin–collagen sponge, which was very well tolerated.

Conclusion:

The results of this pilot trial suggest that topical antibiotic therapy with gentamicin–collagen sponge, although very well tolerated, does not appear to improve outcomes in mild diabetic foot ulcer infection.

Are antibiotic-resistant pathogens more common in subsequent episodes of diabetic foot infection?

BACKGROUND

After antibiotic therapy of an initial diabetic foot infection (DFI), pathogens isolated from subsequent episodes might become more resistant to commonly prescribed antibiotics. If so, this might require a modification of the current recommendations for the selection of empiric antibiotic therapy. This study investigated whether the Infectious Diseases Society of America (IDSA) DFI guideline recommendations should be modified based on the number of past DFI episodes.

METHODS

This was a single-centre retrospective cohort survey of DFI patients seen during the years 2010 to 2016.

RESULTS

A total 1018 episodes of DFI in 482 adult patients were identified. These patients were followed-up for a median of 3.3 years after the first DFI episode. The total number of episodes was 2257 and the median interval between recurrent episodes was 7.6 months. Among the recurrent DFIs, the causative pathogens were the same as in the previous episode in only 43% of cases (158/365). Staphylococcus aureus was the predominant pathogen in all episodes (range 1 to 13 episodes) and was not more prevalent with the increasing number of episodes. DFIs were treated with systemic antibiotics for a median duration of 20 days (interquartile range 11-35 days). Overall, there was no significant increase in the incidence of antibiotic resistance to methicillin, rifampicin, clindamycin, or ciprofloxacin over the episodes (Pearson's Chi-square test p-values of 0.76, 1.00, 0.06, and 0.46, respectively; corresponding p-values for trend of 0.21, 0.27, 0.38, and 0.08, respectively).

CONCLUSIONS

After the successful treatment of a DFI, recurrent episodes are frequent. A history of a previous DFI episode did not predict a greater likelihood of any antibiotic-resistant isolate in subsequent episodes. Thus, broadening the spectrum of empiric antibiotic therapy for recurrent episodes of DFI does not appear necessary.

Which Orthopaedic Patients Are Infected with Gram-negative Non-fermenting Rods?

Background: 1^st and 2^nd generation cephalosporins used for perioperative prophylaxis in orthopaedic surgery do not cover non-fermenting Gram-negative rods (NFR).

Methods: Epidemiological cohort study of adult patients operated for orthopedic infections between 2004 and 2014 with perioperative cefuroxim or vancomycin prophylaxis. Exclusion of polyneuropathic ischemic foot infections and septic bursitis cases.

Results: Of the total 1840 surgical procedures in the study, 430 grew Gram-negative pathogens (23%), of which 194 (11%) were due to NFR and 143 (8%) to Pseudomonas aeruginosa. Overall, 634 episodes (35%) involved orthopaedic implants (321 arthroplasties, 135 plates, 53 nails, and others). In multivariate analysis and group comparisons, especially preoperative antibiotic use (124/194 vs. 531/1456; p<0.01) was significantly associated with NFR.

Conclusions: Overall proportion of NFR oscillated between 9% and 13% among our orthopaedic infections. Variables associated with NFR were antibiotic use prior to hospitalization. The low infection rate of NFR following elective surgery and the community-based epidemiology, has led us to keep our standard perioperative prophylaxis unchanged.

Clinical features of anaerobic orthopaedic infections

Some patient populations and types of orthopaedic surgery could be at particular risk for anaerobic infections. In this retrospective cohort study of operated adult patients with infections from 2004 to 2014, we assessed obligate anaerobes and considered first clinical infection episodes. Anaerobes, isolated from intra-operative samples, were identified in 2.4% of 2740 surgical procedures, of which half (33/65; 51%) were anaerobic monomicrobial infections. Propionibacterium acnes, a penicillin and vancomycin susceptible pathogen, was the predominantly isolated anaerobe. By multivariate analysis, the presence of fracture fixation plates was the variable most strongly associated with anaerobic infection (odds ratio: 2.1, 95% CI: 1.3-3.5). Anaerobes were also associated with spondylodesis and polymicrobial infections. In contrast, it revealed less likely in native bone or prosthetic joint infections and was not related to prior antibiotic use. In conclusion, obligate anaerobes in our case series of orthopaedic infections were rare, and mostly encountered in infections related to trauma with open-fracture fixation devices rather than clean surgical site infection. Anaerobes were often co-pathogens, and cultures most frequently recovered P. acnes. These observations thus do not support changes in current practices such as broader anaerobe coverage for perioperative prophylaxis.

[Microbiology and antibiotic treatment of diabetic foot infection]

In diabetic patients, foot ulcer is a common problem which prevalence during life is about 25%. Infection occurs as a complication in almost 50% of cases, is associated with significant morbidity and a reduced quality of life and is sometimes the trigger leading to amputation. Ulcers and infections occur among patients with predisposing factors such as peripheral neuropathy and arterial insufficiency, and require a multi-disciplinary care system. The knowledge of the microbiology of diabetic foot infection is necessary for a wise use of empirical and targeted antibiotic therapy. This article will focus on the definition and diagnosis of diabetic foot infection, on the main aspects of its microbiology and antibiotic treatment.

The role of anaerobes in diabetic foot infections

Diabetic foot infections (DFI) are a common cause of morbidity and, on occasion, even mortality. Infection can be either mono- or polymicrobial, with a wide variety of potential pathogens. Anaerobes may be involved, particularly in wounds that are deeper or more chronic, and are more frequently identified when using modern molecular techniques, such as 16s PCR and pyrosequencing. It remains unclear whether the presence of anaerobes in DFI leads to more severe manifestations, or if these organisms are largely colonizers associated with the presence of greater degrees of tissue ischemia and necrosis. Commonly used empiric antibiotic therapy for diabetic foot infections is generally broad-spectrum and usually has activity against the most frequently identified anaerobes, such as Peptostreptococcus and Bacteroides species. Adequate surgical debridement and, when needed, foot revascularization may be at least as important as the choice of antibiotic to achieve a successful treatment outcome.