A retrospective analysis of the microbiology of diabetic foot infections at a Scottish tertiary hospital

Dual Drug-Loaded Coaxial Nanofiber Dressings for the Treatment of Diabetic Foot Ulcer

Introduction

Diabetes mellitus is frequently associated with foot ulcers, which pose significant health risks and complications. Impaired wound healing in diabetic patients is attributed to multiple factors, including hyperglycemia, neuropathy, chronic inflammation, oxidative damage, and decreased vascularization.

Rationale

To address these challenges, this project aims to develop bioactive, fast-dissolving nanofiber dressings composed of polyvinylpyrrolidone loaded with a combination of an antibiotic (moxifloxacin or fusidic acid) and anti-inflammatory drug (pirfenidone) using electrospinning technique to prevent the bacterial growth, reduce inflammation, and expedite wound healing in diabetic wounds.

Results

The fabricated drug-loaded fibers exhibited diameters of 443 ± 67 nm for moxifloxacin/pirfenidone nanofibers and 488 ± 92 nm for fusidic acid/pirfenidone nanofibers. The encapsulation efficiency, drug loading and drug release studies for the moxifloxacin/pirfenidone nanofibers were found to be 70 ± 3% and 20 ± 1 µg/mg, respectively, for moxifloxacin, and 96 ± 6% and 28 ± 2 µg/mg, respectively, for pirfenidone, with a complete release of both drugs within 24 hours, whereas the fusidic acid/pirfenidone nanofibers were found to be 95 ± 6% and 28 ± 2 µg/mg, respectively, for fusidic acid and 102 ± 5% and 30 ± 2 µg/mg, respectively, for pirfenidone, with a release rate of 66% for fusidic acid and 80%, for pirfenidone after 24 hours. The efficacy of the prepared nanofiber formulations in accelerating wound healing was evaluated using an induced diabetic rat model. All tested formulations showed an earlier complete closure of the wound compared to the controls, which was also supported by the histopathological assessment. Notably, the combination of fusidic acid and pirfenidone nanofibers demonstrated wound healing acceleration on day 8, earlier than all tested groups.

Conclusion

These findings highlight the potential of the drug-loaded nanofibrous system as a promising medicated wound dressing for diabetic foot applications.

L-arginine supplementation abrogates hypoxia-induced virulence of Staphylococcus aureus in a murine diabetic pressure wound model

Diabetic foot ulcers (DFUs) are the most common complications of diabetes resulting from hyperglycemia leading to ischemic hypoxic tissue and nerve damage. Staphylococcus aureus is the most frequently isolated bacteria from DFUs and causes severe necrotic infections leading to amputations with a poor 5-year survival rate. However, very little is known about the mechanisms by which S. aureus dominantly colonizes and causes severe disease in DFUs. Herein, we utilized a pressure wound model in diabetic TALLYHO/JngJ mice to reproduce ischemic hypoxic tissue damage seen in DFUs and demonstrated that anaerobic fermentative growth of S. aureus significantly increased the virulence and the severity of disease by activating two-component regulatory systems leading to expression of virulence factors. Our in vitro studies showed that supplementation of nitrate as a terminal electron acceptor promotes anaerobic respiration and suppresses the expression of S. aureus virulence factors through inactivation of two-component regulatory systems, suggesting potential therapeutic benefits by promoting anaerobic nitrate respiration. Our in vivo studies revealed that dietary supplementation of L-arginine (L-Arg) significantly attenuated the severity of disease caused by S. aureus in the pressure wound model by providing nitrate. Collectively, these findings highlight the importance of anaerobic fermentative growth in S. aureus pathogenesis and the potential of dietary L-Arg supplementation as a therapeutic to prevent severe S. aureus infection in DFUs.IMPORTANCES. aureus is the most common cause of infection in DFUs, often resulting in lower-extremity amputation with a distressingly poor 5-year survival rate. Treatment for S. aureus infections has largely remained unchanged for decades and involves tissue debridement with antibiotic therapy. With high levels of conservative treatment failure, recurrence of ulcers, and antibiotic resistance, a new approach is necessary to prevent lower-extremity amputations. Nutritional aspects of DFU treatment have largely been overlooked as there has been contradictory clinical trial evidence, but very few in vitro and in vivo modelings of nutritional treatment studies have been performed. Here we demonstrate that dietary supplementation of L-Arg in a diabetic mouse model significantly reduced duration and severity of disease caused by S. aureus. These findings suggest that L-Arg supplementation could be useful as a potential preventive measure against severe S. aureus infections in DFUs.

Transcriptomic identification of genes expressed in invasive S. aureus diabetic foot ulcer infection

Introduction

Infection in diabetic foot ulcers (DFUs) is one of the major complications associated with patients with diabetes. Staphylococcus aureus is the most common offending pathogen in patients with infected DFU. Previous studies have suggested the application of species-specific antibodies against S. aureus for diagnosis and monitoring treatment response. Early and accurate identification of the main pathogen is critical for management of DFU infection. Understanding the host immune response against species-specific infection may facilitate diagnosis and may suggest potential intervention options to promote healing infected DFUs. We sought to investigate evolving host transcriptome associated with surgical treatment of S. aureus- infected DFU.

Methods

This study compared the transcriptome profile of 21 patients with S. aureus- infected DFU who underwent initial foot salvage therapy with irrigation and debridement followed by intravenous antibiotic therapy. Blood samples were collected at the recruitment (0 weeks) and 8 weeks after therapy to isolate peripheral blood mononuclear cells (PBMCs). We analyzed the PBMC expression of transcriptomes at two different time points (0 versus 8 weeks). Subjects were further divided into two groups at 8 weeks: healed (n = 17, 80.95%) versus non-healed (n = 4, 19.05%) based on the wound healing status. DESeq2 differential gene analysis was performed.

Results and discussion

An increased expression of IGHG1, IGHG2, IGHG3, IGLV3-21, and IGLV6-57 was noted during active infection at 0 weeks compared with that at 8 weeks. Lysine- and arginine-rich histones (HIST1H2AJ, HIST1H2AL, HIST1H2BM, HIST1H3B, and HIST1H3G) were upregulated at the initial phase of active infection at 0 weeks. CD177 and RRM2 were also upregulated at the initial phase of active infection (0 weeks) compared with that at 8 weeks of follow-up. Genes of heat shock protein members (HSPA1A, HSPE1, and HSP90B1) were high in not healed patients compared with that in healed patients 8 weeks after therapy. The outcome of our study suggests that the identification of genes evolution based on a transcriptomic profiling could be a useful tool for diagnosing infection and assessing severity and host immune response to therapies.

Diabetic foot ulcer-a systematic review on relevant microbial etiology and antibiotic resistance in Asian countries

BACKGROUND AND AIMS

Diabetic foot ulcer (DFU) is one of the most common but uncontrolled health issues of diabetic patients that needs more therapeutic considerations. This systematic review aims to study the current status of the etiological agents responsible for DFU, their frequency in some of the most occurring Asian countries, and their antibiotic resistance pattern based on available studies.

METHODS

Here, the literature survey was conducted on all the DFU studies with the records of etiological agents and conventional therapeutic treatment published until March 2021 using Medical Literature Analysis and Retrieval System Online (MEDLINE) and Web of Science Core Collection (WoSCC) database.

RESULTS

Overall, in our study, a total of 73 studies representing 12 Asian countries worldwide have been included. We found that the highest number of studies were reported from India (45%) followed by Pakistan (11%), China, Iran and others. 71% of recent studies reported DFU being attributed to poly-microbial infections while the dominant position was significantly secured by Gram- negative bacteria (77%, p = 0.34). Staphylococcus aureus was found to be the most prevalent isolate followed by Pseudomonas and then Escherichia coli (mean value - 22%, 17%, and 15% respectively). Antibiotic sensitivity pattern was determined based on availability in terms of median resistance (MR) and interquartile range (IQR) which showed the growing resistance developed by both Gram-positive and Gram-negative isolates. Gram positive pathogens were still reported as susceptible to vancomycin (MR 0%, IQR 0-22.8%), linezolid (MR 0%, IQR 0-15.53%) and imipenem (MR 11%, IQR 0-23.53%). Carbapenem genera, colistin, and amikacin were the most effective drugs against Gram-negative pathogens.

CONCLUSION

The findings of this study highly recommend searching for alternative and complementary therapeutic regimens instead of prescribing conventional drugs blindly without investigating the progression of the stages of the ulcer, which may help reduce the medical and economic burden of this disease.

Distribution of Causative Microorganisms in Diabetic Foot Infections: A Ten-Year Retrospective Study in a Tertiary Care Hospital in Central Malaysia

Diabetes mellitus is a global pandemic, especially in Southeast Asia. Diabetic foot infection (DFI) is a common complication of this condition and causes significant morbidity and mortality in those affected. There is a lack of locally published data on the types of microorganisms and empirical antibiotics being prescribed. This paper highlights the importance of local microorganism culture and antibiotic prescription trends among diabetic foot patients in a tertiary care hospital in central Malaysia. This is a retrospective, cross-sectional study of data taken from January 2010 to December 2019 among 434 patients admitted with diabetic foot infections (DFIs) using the Wagner classification. Patients between the ages of 58 and 68 years old had the highest rate of infection. Pseudomonas Aeruginosa, Proteus spp., and Proteus mirabilis appeared to be the most isolated Gram-negative microorganisms, and Staphylococcus aureus, Streptococcus agalactiae, and MRSA appeared to be the most common Gram-positive microorganisms. The most common empirical antibiotics prescribed were ampicillin/sulbactam, followed by ciprofloxacin and ceftazidime, and the most common therapeutic antibiotics prescribed were ampicillin/sulbactam, ciprofloxacin, and cefuroxime. This study could be immensely pertinent in facilitating future empirical therapy guidelines for treating diabetic foot infections.

A Comparison of Pathogens in Skin and Soft-Tissue Infections and Pedal Osteomyelitis in Puncture Wound Injuries Affecting the Foot

BACKGROUND

To compare pathogens involved in skin and soft-tissue infections (SSTIs) and pedal osteomyelitis (OM) in patients with and without diabetes with puncture wounds to the foot.

METHODS

We evaluated 113 consecutive patients between June 1, 2011, and March 31, 2019, with foot infection (SSTIs and OM) from a puncture injury sustained to the foot. Eighty-three patients had diabetes and 30 did not. We evaluated the bacterial pathogens in patients with SSTIs and pedal OM.

RESULTS

Polymicrobial infections were more common in patients with diabetes mellitus (83.1% versus 53.3%; P = .001). The most common pathogen for SSTIs and OM in patients with diabetes was Staphylococcus aureus (SSTIs, 50.7%; OM, 32.3%), whereas in patients without diabetes it was Pseudomonas (25%) for SSTIs. Anaerobes (9.4%) and fungal infection (3.1%) were uncommon. Pseudomonas aeruginosa was identified in only 5.8% of people with diabetes.

CONCLUSIONS

The most common bacterial pathogen in both SSTIs and pedal OM was S aureus in patients with diabetes. Pseudomonas species was the most common pathogen in people without diabetes with SSTIs.

Changing Bacterial Etiology and Antimicrobial Resistance Profiles as Prognostic Determinants of Diabetic Foot Infections: A Ten-Year Retrospective Cohort Study

Background: In this single-center study, we analyzed a retrospective cohort of patients with diabetic foot infections (DFIs) between 2011 and 2020. Patients and Methods: The first and second five-year periods were compared. A poor prognosis was defined as a primary composite end point including re-infection, major amputation, or mortality at six months. Results: A total of 484 patients were enrolled. Overall, 269 patients had the primary composite end point. A substantial decrease was detected in the second five-year period in terms of re-infection (n = 132, 66.0% vs. n = 68, 23.9%; p < 0.001) and mortality (n = 22, 11.0% vs. n = 7, 2.5%; p < 0.001). A total of 798 micro-organisms were isolated from 484 patients. A substantial increase was detected in polymicrobial infections (48.5% vs. 65.1%; p = 0.001) as well as Streptococcus spp. (2.5% vs. 9.2%; p = 0.003), Corynebacterium spp. (9.5% vs. 22.9%; p < 0.001), and extended-spectrum β-lactamase (ESBL) producing Escherichia coli (3.0% vs. 12.7%; p < 0.001) in the second five-year period, whereas the prevalence of multi-drug-resistanct (MDR) Pseudomonas aeruginosa (17.0% vs. 10.2%; p = 0.029) and carbapenem-resistant Acinetobacter baumannii (7.5% vs. 2.8%; p = 0.017) decreased. Multivariable regression analysis revealed that MDR Pseudomonas aeruginosa (odds ratio [OR], 1.917; 95% confidence interval [CI], 1.074-3.420; p = 0.028) and carbapenem-resistant Acinetobacter baumannii (OR, 3.069; 95% CI, 1.114-8.453; p = 0.030) were independent predictors for poor prognosis. Conclusions: This 10-year cohort study provides reassuring information about the changing epidemiology of DFIs and the prognostic determinants in patients with DFIs.

Decreased accuracy of erythrocyte sedimentation rate in diagnosing osteomyelitis in diabetic foot infection patients with severe renal impairment: A retrospective cross-sectional study

BACKGROUND

Rapid diagnosis and treatment of diabetic foot osteomyelitis (DFO) could reduce the risk of amputation and death in patients with diabetic foot infection (DFI). Erythrocyte sedimentation rate (ESR) is considered the most useful serum inflammatory marker for the diagnosis of DFO. However, whether severe renal impairment (SRI) affects its diagnostic accuracy has not been reported previously.

OBJECTIVE

To investigate the accuracy of ESR in diagnosing DFO in DFI patients with and without SRI.

METHODS

This was a retrospective cross-sectional study. From the inpatient electronic medical record system, the investigators extracted demographic information, diagnostic information, and laboratory test results of patients with DFI who had been hospitalized in Longhua Hospital from January 1, 2016 to September 30, 2021. Logistic regression was performed to analyze the interaction between ESR and SRI with adjustment for potential confounders. The area under the curve (AUC), cutoff point, sensitivity, specificity, prevalence, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were analyzed by receiver operating characteristic (ROC) curve analysis and VassarStats.

RESULTS

A total of 364 DFI patients were included in the analysis. The logistic regression analysis results showed that elevated ESR increased the probability of diagnosing DFO (adjusted odds ratio [OR], 2.40; 95% confidence interval [CI], 1.75-3.28; adjusted P < 0.001); SRI was not associated with the diagnosis of DFO (adjusted OR, 3.20; 95% CI, 0.40-25.32; adjusted P = 0.271), but it had an obstructive effect on the diagnosis of DFO by ESR (adjusted OR, 0.48; 95% CI, 0.23-0.99; adjusted P = 0.048). ROC analysis in DFI patients without SRI revealed that the AUC of ESR to diagnose DFO was 0.76 (95% CI, 0.71-0.81), with the cutoff value of 45 mm/h (sensitivity, 67.8%; specificity, 78.0%; prevalence, 44.7%; PPV, 71.3%; NPV, 75.0%; LR+, 3.08; LR-, 0.41). In contrast, in patients with SRI, the AUC of ESR to diagnose DFO was 0.57 (95% CI, 0.40-0.75), with the cutoff value of 42 mm/h (sensitivity, 95.0%; specificity, 29.2%; prevalence, 45.5%; PPV, 52.8%; NPV, 87.5%; LR+, 1.34; LR-, 0.17).

CONCLUSIONS

The accuracy of ESR in diagnosing DFO in DFI patients with SRI is reduced, and it may not have clinical diagnostic value in these patients.

Bacterial diversity and inflammatory response at first-time visit in younger and older individuals with diabetic foot infection (DFI)

AIM

Infection of a diabetic foot ulcer (DFU) is common. More than the half of DFUs become infected and 15-20% of them necessitate amputation in course of treatment. Diabetic foot infection (DFI) is therefore the major cause for non-traumatic lower limb amputation in Germany. Prompt and effective treatment of DFI is mandatory to safe limbs and lives. We investigated if there are relevant differences in evoked inflammatory response between different species and age-separated groups. We further investigated if there is an impact of ulcer localization on bacterial diversity.

METHODS

For a 12-month period, we investigated 353 individuals with infected DFU, their laboratory results and bacterial diversity at first-time visit in a Diabetic Foot Care Center in Southern Germany.

RESULTS

The ulcer microbiota was dominated by gram-positive species, primary Staphylococcus aureus. The gram-negative sector was mainly formed by Pseudomonas aeruginosa and Enterobacteriaceae (Proteus spp., Enterobacter spp., Escherichia coli and Klebsiella spp.). With increase in age, P. aeruginosa and S. aureus became more frequent, while Streptococci decreased. Ischemic and/or deep wounds were more likely to bear gram-negative species. Inflammatory response did not differ between gram-positive and gram-negative species, while Streptococci and Proteus spp. induced the highest serum inflammation reaction in their category. Streptococci, Enterobacter spp. and E. coli were more frequent in summer, while Enterococci spp., coagulase-negative Staphylococci and P. aeruginosa were more prevalent in winter half-year. DFIs of the forefoot and plantar side are mostly caused by gram-positive species, while Enterobacteriaceae were most frequent in plantar ulcerations.

CONCLUSION

Gram-positive species dominate bacterial spectrum in DFI. With increase in age, S. aureus, Streptococci and Pseudomonas aeruginosa became more frequent. The inflammatory response did not differ significantly between different species, but gram-negative species were slightly but not significant more frequent in ischemic wounds. Climatic distinction like summer or winter half-year as well as foot ulcer localization seems to influence bacterial diversity in DFUs.

Extended Spectrum β-Lactamase-Mediated Resistance and Antibiogram of Pseudomonas aeruginosa Isolates from Patients Attending Two Public Hospitals in Khartoum, Sudan

Treating infections caused by Pseudomonas aeruginosa is challenging. In addition to its intrinsic ability to develop resistance to multiple classes of antibiotics, it also produces extended-spectrum β-lactamase (ESBL). Continuous update of the antibiograms is required to cope with the rate of the emergence of antibiotic resistance. This study aimed to determine the antimicrobial susceptibility pattern and to determine the frequency of ESBL production among the P. aeruginosa isolates from patients at two public military hospitals in Khartoum, Sudan. A total of 34 isolates of P. aeruginosa obtained from patients with diabetic septic foot wounds were tested for their antibiotic sensitivity patterns. Resistance occurred most commonly to ceftazidime (35%), followed by ciprofloxacin (20.6%) and piperacillin (14.7%). We found that 17.6% of the P. aeruginosa isolates were ESBL producers, but all of these isolates were sensitive to meropenem. The chi-squared test showed a significant association between the ESBL production and antimicrobial resistance to amikacin, ceftazidime, and piperacillin. Our findings strengthen previous reports in which aminoglycosides (amikacin) and carbapenems (meropenem) were found to be highly effective against P. aeruginosa. Our findings highlight the need for effective surveillance and antibiogram-guided antibiotic prescription.

Bacterial chatter in chronic wound infections

One of the hallmark characteristics of chronic diabetic wounds is the presence of biofilm-forming bacteria. Bacteria encapsulated in a biofilm may coexist as a polymicrobial community and communicate with each other through a phenomenon termed quorum sensing (QS). Here, we describe the QS circuits of bacterial species commonly found in chronic diabetic wounds. QS relies on diffusion of signaling molecules and the local concentration changes of these molecules that bacteria experience in wounds. These biochemical signaling pathways play a role not only in biofilm formation and virulence but also in wound healing. They are, therefore, key to understanding the distinctive nature of these infections. While several in vivo and in vitro models exist to study QS in wounds, there has been limited progress in understanding the interplay between QS molecules and host factors that contribute to wound healing. Lastly, we examine the potential of targeting QS for both diagnosis and therapeutic intervention purposes.

Microbiota and Its Antibiotic Susceptibility in Diabetic Foot Infections: Observations From Polish Nonmetropolitan Hospital, 2015-2016

In current clinical practice, in case of symptoms-based suspicion of diabetic foot infection, immediate empiric antibiotic therapy is recommended. Prevailing guidelines do not provide region-specific therapy schemes. To validate existing recommendations, there is an urgent need for a report on diabetic foot infection microbiota patterns in Central Europe. This study aimed to describe diabetic foot infections microbiota and its antibiotic susceptibility in Poland. We conducted a single-center descriptive study at the General Surgery Department, Siedlce Hospital, Poland. Data for all patients diagnosed with diabetic foot infection between January 1, 2015, and December 31, 2016, and corresponding antimicrobial susceptibility tests were extracted. A total of 54 patients were included in the study, with a total of 102 microbiological samples. Among 81 positive samples, 77.1% of the isolated bacteria were Gram-negative. A total of 93.4% of the isolates were facultatively anaerobic bacteria. No obligatory anaerobic bacteria and no yeasts were isolated. Facultatively anaerobic, Gram-negative bacteria, mainly Proteus spp and Escherichia coli, were the most common organisms cultured in diabetic foot infections. This study suggests that the currently implemented treatment recommendations might not be adequate in Poland.