Serological Responses to Streptococcus pyogenes Vaccine Candidate Antigens Suggests That Streptococcus dysgalactiae Is the Predominant Cause of Lower Limb Cellulitis.

Background: A future Streptococcus pyogenes (Strep A) vaccine will ideally prevent a significant burden of lower limb cellulitis; however, natural immune responses to proposed vaccine antigens following an episode of cellulitis remain uncharacterized. Methods: We enrolled 63 patients with cellulitis and 26 with invasive beta hemolytic streptococci infection, using a multiplexed assay to measure immunoglobulin G against Strep A vaccine candidate antigens, including: streptolysin O (SLO), deoxyribonuclease B (DNB), group A carbohydrate (GAC), C5a peptidase (ScpA), cell envelope proteinase (SpyCEP), and adhesion and division protein (SpyAD). Responses in the invasive cohort were used to predict the infecting etiology in the cellulitis cohort. Results: Of 41 patients with cellulitis and paired serological samples, 68.3% had evidence of beta hemolytic streptococci infection by conventional anti-SLO and/or anti-DNB criteria. A positive serological response to at least 1 of the tested antigens was seen in 78.0% of the cellulitis cohort. Individually, anti-SLO (58.5%), anti-SpyAD (46.3%), and anti-ScpA (39.0%) were the most common. Based on principal component analysis, increases in these 3 antibodies, without responses to DNB, GAC, and SpyCEP characterized Streptococcus dysgalactiae subspecies equisimilis (SDSE) infection. Conclusions: SDSE appears to be the predominant cause of lower limb cellulitis. Effective Strep A vaccines incorporating antigens that provide additional cross protection against SDSE may prevent a significant burden of lower limb cellulitis.

Associations of Diabetes and Hyperglycaemia with Extent and Outcomes of Acute Burn Injuries.

BACKGROUND: Severe burns may induce hyperglycaemia in the absence of diabetes, but how glucose trajectories relate to burns outcomes is unclear. AIM: To assess incidence of hyperglycaemia following acute burn injury, and associations with diabetes history and length of stay (LOS). METHODS: Retrospective cohort study of adults admitted with acute burns to tertiary centres. Blood glucose level (BGL), hyperglycaemic episodes (BGL ≥ 11.1 mmol/L) and hyperglycaemic days were recorded. Stress hyperglycaemia was defined as BGL ≥ 11.1 mmol/L without a diabetes history. RESULTS: A total of 30 participants had a diabetes history and 260 did not. Participants with known diabetes had higher mean BGLs (9.7 vs. 9.0 mmol/L, p < 0.001), more hyperglycaemic episodes (28.0 vs. 17.2%, p < 0.001) and hyperglycaemic days (51 vs. 21%, p < 0.001), compared to those without diabetes, despite smaller burns (total body surface area 1.0 vs. 14.8%, p < 0.001). Fourteen participants with stress hyperglycaemia had similar BGLs (at admission 10.3 vs. 11.5 mmol/L; during inpatient stay 9.9 vs. 9.8 mmol/L), more severe burns (15.6% vs. 1.0% TBSA) and longer LOS (18 vs. 7 days, p < 0.001) compared to participants with known diabetes. Extent of burns, having NGT nutrition, age, having inpatient BGL monitoring in the setting of diabetes, or having inpatient BGL monitoring in the absence of diabetes were associated with longer LOS. CONCLUSIONS: In participants with known diabetes, small burn injuries were associated with hyperglycaemia. Stress hyperglycaemia can be triggered by major burn injuries, with early and sustained elevation of BGLs. Further research is warranted to improve inpatient management of BGL in patients with acute burn injury.

Stratification of Sepsis Patients on Admission into the Intensive Care Unit According to Differential Plasma Metabolic Phenotypes.

Delayed diagnosis of patients with sepsis or septic shock is associated with increased mortality and morbidity. UPLC-MS and NMR spectroscopy were used to measure panels of lipoproteins, lipids, biogenic amines, amino acids, and tryptophan pathway metabolites in blood plasma samples collected from 152 patients within 48 h of admission into the Intensive Care Unit (ICU) where 62 patients had no sepsis, 71 patients had sepsis, and 19 patients had septic shock. Patients with sepsis or septic shock had higher concentrations of neopterin and lower levels of HDL cholesterol and phospholipid particles in comparison to nonsepsis patients. Septic shock could be differentiated from sepsis patients based on different concentrations of 10 lipids, including significantly lower concentrations of five phosphatidylcholine species, three cholesterol esters, one dihydroceramide, and one phosphatidylethanolamine. The Supramolecular Phospholipid Composite (SPC) was reduced in all ICU patients, while the composite markers of acute phase glycoproteins were increased in the sepsis and septic shock patients within 48 h admission into ICU. We show that the plasma metabolic phenotype obtained within 48 h of ICU admission is diagnostic for the presence of sepsis and that septic shock can be differentiated from sepsis based on the lipid profile.

Trauma patient heterotopic ossification diagnosis is associated with increased hospital length of stay.

BACKGROUND: Traumatic heterotopic ossification (tHO) refers to the development of extra-skeletal bone in muscle and soft tissues following tissue insult secondary to surgery or trauma. This presents a persistent clinical concern associated with significant patient morbidity and expense to diagnose and treat. Traumatic HO is a substantial barrier to rehabilitation for trauma-injured patients. As such, the development of tHO after burn and other trauma is hypothesised to prolong inpatient length of stay (LOS) and thus increase health care costs. OBJECTIVE: To investigate the association between an inpatient tHO diagnosis and hospital LOS in trauma patients. METHODS: A retrospective audit of trauma patients over a 14-year period was completed using data from four WA hospitals. Burn and neurological trauma patients diagnosed with tHO as an inpatient (tHO+) and control subjects (tHO-), matched (1:3) by age, gender, and injury severity factors, were identified using medical diagnostic codes. Data relating to patient and injury-related determinants of LOS from tHO+ and tHO- subjects were analysed to model the association of tHO on total hospital length of stay. RESULTS: 188 identified patients were hospitalised due to traumatic injury; 47 patients with tHO following burn injury (n = 17), spinal cord injury (n = 13) and traumatic brain injury (n = 17), and 141 control patients. Those who developed tHO during hospitalisation had a significantly higher median LOS than matched trauma patients who did not develop tHO (142 days vs. 61 days). Multivariate regression analyses identified the following independent predictive factors of a prolonged hospital LOS: tHO diagnosis, mechanical ventilation hours, injury to the hip region and thigh area, other ossification disorder, pressure injury, admission to intensive care unit and deep vein thrombosis. Trauma patients diagnosed with tHO during their hospital admission stayed 1.6 times longer than trauma patients matched for injury severity without a tHO diagnosis (IRR 1.56, 95% CI 1.35-1.79, p<0.001). CONCLUSION: Traumatic heterotopic ossification is an independent explanatory factor for increased hospital LOS in patients following burns, spinal cord, and traumatic brain injury. Early diagnosis may assist in reducing the impact of tHO on acute hospital stay after trauma.

Evaluation of the accuracy of diagnostic coding and clinical documentation for traumatic heterotopic ossification diagnoses in Western Australian hospitals.

BACKGROUND: Traumatic heterotopic ossification (tHO) refers to the pathological formation of ectopic bone in soft tissues that can occur following burn, neurological ororthopaedic trauma. As completeness and accuracy of medical diagnostic coding can vary based on coding practices and depend on the institutional culture of clinical documentation, it is important to assess diagnostic coding in that local context. To the authors' knowledge, there is no prior study evaluating the accuracy of medical diagnostic coding or specificity of clinical documentation for tHO diagnoses across Western Australia (WA) trauma centres or across the full range of inciting injury and surgical events. OBJECTIVE: To evaluate and compare the clinical documentation and the diagnostic accuracy of ICD-10-AM coding for tHO in trauma populations across 4 WA hospitals. METHODS: A retrospective data search of the WA trauma database was conducted to identify patients with tHO admitted to WA hospitals following burn, neurological or orthopaedic trauma. Patient demographic and tHO diagnostic characteristics were assessed for all inpatient and outpatient tHO diagnoses. The frequency and distribution of M61 (HO-specific) and broader, musculoskeletal (non-specific) ICD-10-AM codes were evaluated for tHO cases in each trauma population. RESULTS: HO-specific M61 ICD-10-AM codes failed to identify more than a third of true tHO cases, with a high prevalence of non-specific HO codes (19.4 %) and cases identified via manual chart review (25.4 %). The sensitivity of M61 codes for correctly diagnosing tHO after burn injury was 50 %. ROC analysis showed that M61 ICD-10-AM codes as a predictor of a true positive tHO diagnosis were a less than favourable method (AUC=0.731, 95 % CI=0.561-0.902, p = 0.012). Marked variability in clinical documentation for tHO was identified across the hospital network. CONCLUSION: Coding inaccuracies may, in part, be influenced by insufficiencies in clinical documentation for tHO diagnoses, which may have implications for future research and patient care. Clinicians should consistently employ standardised clinical terminology from the point of care to increase the likelihood of accurate medical diagnostic coding for tHO diagnoses.

Nonsevere Burn Induces a Prolonged Systemic Metabolic Phenotype Indicative of a Persistent Inflammatory Response Postinjury.

Globally, burns are a significant cause of injury that can cause substantial acute trauma as well as lead to increased incidence of chronic comorbidity and disease. To date, research has primarily focused on the systemic response to severe injury, with little in the literature reported on the impact of nonsevere injuries (<15% total burn surface area; TBSA). To elucidate the metabolic consequences of a nonsevere burn injury, longitudinal plasma was collected from adults (n = 35) who presented at hospital with a nonsevere burn injury at admission, and at 6 week follow up. A cross-sectional baseline sample was also collected from nonburn control participants (n = 14). Samples underwent multiplatform metabolic phenotyping using 1H nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry to quantify 112 lipoprotein and glycoprotein signatures and 852 lipid species from across 20 subclasses. Multivariate data modeling (orthogonal projections to latent structures-discriminate analysis; OPLS-DA) revealed alterations in lipoprotein and lipid metabolism when comparing the baseline control to hospital admission samples, with the phenotypic signature found to be sustained at follow up. Univariate (Mann-Whitney U) testing and OPLS-DA indicated specific increases in GlycB (p-value < 1.0e-4), low density lipoprotein-2 subfractions (variable importance in projection score; VIP > 6.83e-1) and monoacyglyceride (20:4) (p-value < 1.0e-4) and decreases in circulating anti-inflammatory high-density lipoprotein-4 subfractions (VIP > 7.75e-1), phosphatidylcholines, phosphatidylglycerols, phosphatidylinositols, and phosphatidylserines. The results indicate a persistent systemic metabolic phenotype that occurs even in cases of a nonsevere burn injury. The phenotype is indicative of an acute inflammatory profile that continues to be sustained postinjury, suggesting an impact on systems health beyond the site of injury. The phenotypes contained metabolic signatures consistent with chronic inflammatory states reported to have an elevated incidence postburn injury. Such phenotypic signatures may provide patient stratification opportunities, to identify individual responses to injury, personalize intervention strategies, and improve acute care, reducing the risk of chronic comorbidity.

Exercise in adults admitted to hospital with diabetes-related foot ulcers: a pilot study of feasibility and safety.

BACKGROUND: Diabetes-related foot ulcers result in significant mortality, morbidity and economic costs. Pressure offloading is important for ulcer healing, but patients with diabetes-related foot ulcers are presented with a dilemma, because whilst they are often advised to minimise standing and walking, there are also clear guidelines which encourage regular, sustained exercise for patients with diabetes. To overcome these apparently conflicting recommendations, we explored the feasibility, acceptability and safety of a tailored exercise program for adults admitted to hospital with diabetes-related foot ulcers. METHODS: Patients with diabetes-related foot ulcers were recruited from an inpatient hospital setting. Baseline demographics and ulcer characteristics were collected, and participants undertook a supervised exercise training session comprising aerobic and resistance exercises followed by prescription of a home exercise programme. Exercises were tailored to ulcer location, which complied with podiatric recommendations for pressure offloading. Feasibility and safety were assessed via recruitment rate, retention rate, adherence to inpatient and outpatient follow up, adherence to home exercise completion, and recording of adverse events. RESULTS: Twenty participants were recruited to the study. The retention rate (95%), adherence to inpatient and outpatient follow up (75%) and adherence to home exercise (50.0%) were all acceptable. No adverse events occurred. CONCLUSIONS: Targeted exercise appears safe to be undertaken by patients with diabetes-related foot ulcers during and after an acute hospital admission. Recruitment in this cohort may prove challenging, but adherence, retention and satisfaction with participation in exercise were high. TRIAL REGISTRATION: The trial is registered in the Australian New Zealand Clinical Trials Registry (ACTRN12622001370796).

Lower gut dysbiosis and mortality in acute critical illness: a systematic review and meta-analysis.

BACKGROUND: The human gastrointestinal tract harbours a complex multi-kingdom community known as the microbiome. Dysbiosis refers to its disruption and is reportedly extreme in acute critical illness yet its clinical implications are unresolved. The review systematically evaluates the association between gut dysbiosis and clinical outcomes of patients early in critical illness. METHODS: Following PRISMA guidelines, a prospectively registered search was undertaken of MEDLINE and Cochrane databases for observational studies undertaking metagenomic sequencing of the lower gastrointestinal tract of critically ill adults and children within 72 h of admission. Eligible studies reported an alpha diversity metric and one or more of the primary outcome, in-hospital mortality, or secondary clinical outcomes. After aggregate data were requested, meta-analysis was performed for four studies with in-hospital mortality stratified to high or low Shannon index. RESULTS: The search identified 26 studies for systematic review and 4 had suitable data for meta-analysis. No effect of alpha diversity was seen on in-hospital mortality after binary transformation of Shannon index (odds ratio 0.52, CI 0.12-4.98, I2 = 0.64) however certainty of evidence is low. Pathogen dominance and commensal depletion were each more frequently associated with in-hospital mortality, adverse clinical and ecological sequelae, particularly overabundance of Enterococcus. CONCLUSIONS: There is a paucity of large, rigorous observational studies in this population. Globally, alpha diversity was dynamically reduced in early ICU admission in adults and children and was not associated with in-hospital mortality. The abundance of taxa such as Enterococcus spp. appears to offer greater predictive capacity for important clinical and ecological outcomes.

Comprehensive Lipidomic Workflow for Multicohort Population Phenotyping Using Stable Isotope Dilution Targeted Liquid Chromatography-Mass Spectrometry.

Dysregulated lipid metabolism underpins many chronic diseases including cardiometabolic diseases. Mass spectrometry-based lipidomics is an important tool for understanding mechanisms of lipid dysfunction and is widely applied in epidemiology and clinical studies. With ever-increasing sample numbers, single batch acquisition is often unfeasible, requiring advanced methods that are accurate and robust to batch-to-batch and interday analytical variation. Herein, an optimized comprehensive targeted workflow for plasma and serum lipid quantification is presented, combining stable isotope internal standard dilution, automated sample preparation, and ultrahigh performance liquid chromatography-tandem mass spectrometry with rapid polarity switching to target 1163 lipid species spanning 20 subclasses. The resultant method is robust to common sources of analytical variation including blood collection tubes, hemolysis, freeze-thaw cycles, storage stability, analyte extraction technique, interinstrument variation, and batch-to-batch variation with 820 lipids reporting a relative standard deviation of <30% in 1048 replicate quality control plasma samples acquired across 16 independent batches (total injection count = 6142). However, sample hemolysis of ≥0.4% impacted lipid concentrations, specifically for phosphatidylethanolamines (PEs). Low interinstrument variability across two identical LC-MS systems indicated feasibility for intra/inter-lab parallelization of the assay. In summary, we have optimized a comprehensive lipidomic protocol to support rigorous analysis for large-scale, multibatch applications in precision medicine. The mass spectrometry lipidomics data have been deposited to massIVE: data set identifiers MSV000090952 and 10.25345/C5NP1WQ4S.

Toxic epidermal necrolysis in adult patients: Experience from the West Australian Collaboration.

Toxic epidermal necrolysis (TEN) is a rare and life-threatening mucocutaneous disease triggered by a reaction to a drug. Despite reported mortality of 30%, management differs between healthcare settings. Our hospital was established in February 2015 becoming the new state burns centre in Western Australia (WA). Following this, we collaborated on comprehensive multidisciplinary guidelines for the management of TEN. These guidelines are updated annually to reflect the weight of emerging evidence in managing TEN. Our aim was to review the management and outcomes of TEN patients presenting to our hospital between February 2015 and May 2021 (inclusive). We collected data for 10 patients on year, age, ethnicity, gender, medical history, culprit drug and exposure, SCORTEN, length of stay, maximum percentage of skin detachment, mucosal surface involvement, ophthalmic amniotic membrane transplant, burns unit input/admission, intensive care unit admission, weight, systemic treatment(s), complications and outcome. We excluded 7 out of 17 flagged patients who did not strictly meet the definition of TEN as greater than 30% epidermal detachment, with epidermal detachment defined as bullae, erosions, and/or positive Nikolsky. We found that the mortality rate in WA from TEN is improving compared with two previous WA studies, with a mortality rate in our study of 20% (2 deaths). Though limited by small sample size and retrospective design, our study suggests a shift towards at least one systemic therapy per patient (most commonly cyclosporine), the growing use of etanercept and the ophthalmic use of amniotic membrane transplants. It demonstrates the importance of burns unit input and the utility of comprehensive multidisciplinary guidelines. While the management and outcomes of TEN patients in WA are continuing to improve, we support calls for large registry data to facilitate evidence growth and collaboration for this rare life-threatening condition.

Australian guideline on management of diabetes-related foot infection: part of the 2021 Australian evidence-based guidelines for diabetes-related foot disease.

BACKGROUND: Diabetes-related foot infections cause substantial morbidity and mortality, both globally and in Australia. There is a need for up-to-date evidence-based guidelines to ensure optimal management of patients with diabetes-related foot infections. We aimed to identify and adapt high quality international guidelines to the Australian context to become the new Australian evidence-based guideline for people with a diabetes-related foot infection. METHODS: Following Australian National Health and Medical Research Council (NHMRC) procedures we identified the 2019 International Working Group on the Diabetic Foot (IWGDF) guidelines as suitable for adaptation to the Australian context. Guidelines were screened, assessed and judged by an expert panel for the Australian context using the guideline adaptation frameworks ADAPTE and Grading of Recommendations Assessment, Development and Evaluation (GRADE). Judgements led to recommendations being adopted, adapted or excluded, with additional consideration regarding their implementation, monitoring and future research for the Australian context. Clinical pathways were then developed to assist implementation. RESULTS: Of 36 original diabetes-related foot infection IWGDF sub-recommendations, 31 were adopted, four were adapted and one was excluded. Adaption was primarily undertaken due to differences or clarification of the sub-recommendations' intended population. One sub-recommendation was excluded due to substantial differences in judgements between the panel and IWGDF and unacceptable heterogeneity of the target population. Therefore, we developed 35 evidence-based sub-recommendations for the Australian context that should guide best practice diagnosis and management of people with diabetes-related foot infection in Australia. Additionally, we incorporated these sub-recommendations into two clinical pathways to assist Australian health professionals to implement these evidence-based sub-recommendations into clinical practice. The six guidelines and the full protocol can be found at: https://www.diabetesfeetaustralia.org/new-guidelines/ . CONCLUSIONS: A new national guideline for the diagnosis and management of people with diabetes-related foot infections were successfully developed for the Australian context. In combination with simplified clinical pathway tools they provide an evidence-based framework to ensure best management of individuals with diabetes-related foot infections across Australia and highlight considerations for implementation and monitoring.

Australian guideline on management of diabetes-related foot infection: part of the 2021 Australian evidence-based guidelines for diabetes-related foot disease

Diabetes-related foot infections cause substantial morbidity and mortality, both globally and in Australia. There is a need for up-to-date evidence-based guidelines to ensure optimal management of patients with diabetes-related foot infections. We aimed to identify and adapt high quality international guidelines to the Australian context to become the new Australian evidence-based guideline for people with a diabetes-related foot infection. Following Australian National Health and Medical Research Council (NHMRC) procedures we identified the 2019 International Working Group on the Diabetic Foot (IWGDF) guidelines as suitable for adaptation to the Australian context. Guidelines were screened, assessed and judged by an expert panel for the Australian context using the guideline adaptation frameworks ADAPTE and Grading of Recommendations Assessment, Development and Evaluation (GRADE). Judgements led to recommendations being adopted, adapted or excluded, with additional consideration regarding their implementation, monitoring and future research for the Australian context. Clinical pathways were then developed to assist implementation. Of 36 original diabetes-related foot infection IWGDF sub-recommendations, 31 were adopted, four were adapted and one was excluded. Adaption was primarily undertaken due to differences or clarification of the sub-recommendations' intended population. One sub-recommendation was excluded due to substantial differences in judgements between the panel and IWGDF and unacceptable heterogeneity of the target population. Therefore, we developed 35 evidence-based sub-recommendations for the Australian context that should guide best practice diagnosis and management of people with diabetes-related foot infection in Australia. Additionally, we incorporated these sub-recommendations into two clinical pathways to assist Australian health professionals to implement these evidence-based sub-recommendations into clinical practice. A new national guideline for the diagnosis and management of people with diabetes-related foot infections were successfully developed for the Australian context. In combination with simplified clinical pathway tools they provide an evidence-based framework to ensure best management of individuals with diabetes-related foot infections across Australia and highlight considerations for implementation and monitoring.

Molecular Methodologies for Improved Polymicrobial Sepsis Diagnosis.

Polymicrobial sepsis is associated with worse patient outcomes than monomicrobial sepsis. Routinely used culture-dependent microbiological diagnostic techniques have low sensitivity, often leading to missed identification of all causative organisms. To overcome these limitations, culture-independent methods incorporating advanced molecular technologies have recently been explored. However, contamination, assay inhibition and interference from host DNA are issues that must be addressed before these methods can be relied on for routine clinical use. While the host component of the complex sepsis host-pathogen interplay is well described, less is known about the pathogen's role, including pathogen-pathogen interactions in polymicrobial sepsis. This review highlights the clinical significance of polymicrobial sepsis and addresses how promising alternative molecular microbiology methods can be improved to detect polymicrobial infections. It also discusses how the application of shotgun metagenomics can be used to uncover pathogen/pathogen interactions in polymicrobial sepsis cases and their potential role in the clinical course of this condition.

Wound healing with "spray-on" autologous skin grafting (ReCell) compared with standard care in patients with large diabetes-related foot wounds: an open-label randomised controlled trial.

There is an urgent need for interventions that improve healing time, prevent amputations and recurrent ulceration in patients with diabetes-related foot wounds. In this randomised, open-label trial, participants were randomised to receive an application of non-cultured autologous skin cells ("spray-on" skin; ReCell) or standard care interventions for large (>6 cm2 ), adequately vascularised wounds. The primary outcome was complete healing at 6 months, determined by assessors blinded to the intervention. Forty-nine eligible foot wounds in 45 participants were randomised. An evaluable primary outcome was available for all wounds. The median (interquartile range) wound area at baseline was 11.4 (8.8-17.6) cm2 . A total of 32 (65.3%) index wounds were completely healed at 6 months, including 16 of 24 (66.7%) in the spray-on skin group and 16 of 25 (64.0%) in the standard care group (unadjusted OR [95% CI]: 1.13 (0.35-3.65), P = .845). Lower body mass index (P = .002) and non-plantar wounds (P = .009) were the only patient- or wound-related factors associated with complete healing at 6 months. Spray-on skin resulted in high rates of complete healing at 6 months in patients with large diabetes-related foot wounds, but was not significantly better than standard care (Australian New Zealand Clinical Trials Registry: ACTRN12618000511235).

Risk factors for catheter related thrombosis during outpatient parenteral antimicrobial therapy.

BACKGROUND: Outpatient parenteral antimicrobial therapy (OPAT) delivery using peripherally inserted central catheters is associated with a risk of catheter related thrombosis (CRT). Individualised preventative interventions may reduce this occurrence, however patient selection is hampered by a lack of understanding of risk factors. We aimed to identify patient, infection or treatment related risk factors for CRT in the OPAT setting. METHODS: Retrospective case control study (1:3 matching) within OPAT services at two tertiary hospitals within Australia. RESULTS: Over a 2 year period, encompassing OPAT delivery to 1803 patients, there were 19 cases of CRT, giving a prevalence of 1.1% and incidence of 0.58/1000 catheter days. Amongst the cases of CRT, there were nine (47%) unplanned readmissions and two (11%) pulmonary emboli. Compared to controls, cases had a higher frequency of malposition of the catheter tip (4/19 (21%) vs 0/57 (0%), p = 0.003) and complicated catheter insertion (3/19 (16%) vs 1/57 (2%), p = 0.046). CONCLUSIONS: Although CRTs during OPAT are infrequent, they often have clinically significant sequelae. Identification of modifiable vascular access related predictors of CRT should assist with patient risk stratification and guide risk reduction strategies.

An in vitro study into the antimicrobial and cytotoxic effect of Acticoat™ dressings supplemented with chlorhexidine.

Burn injuries can cause traumatic and debilitating physical trauma, with burn wounds prone to bacterial infection. This study examined in vitro the effectiveness of the silver nanoparticle based antimicrobial dressing, Acticoat™, in combination with a range of antimicrobial compounds against Staphylococcus aureus and Pseudomonas aeruginosa and investigated potential cytotoxic effects in multi-layered differentiated keratinocyte models. Acticoat™ with chlorhexidine was found to be highly effective against S. aureus and P. aeruginosa across a 3 day incubation period on pig skin models. MTT assays and histological staining of keratinocyte models revealed Acticoat™ had a cytotoxic effect following initial contact with the cells and cytotoxicity was exacerbated when dressings were coated with chlorhexidine and antimicrobial peptide formulations. Spectrophotometric analysis suggested that the silver nanoparticles may mobilise from the dressing as nanoclusters or silver salts, which may relate to the observed cytotoxicity. The bacterial strains used in this study showed a substantial tolerance to Acticoat™ with biofilm-like communities observed on the dressing surfaces. This could be mitigated with chlorhexidine, albeit with an increase in cytotoxicity. The clinical significance of these findings in terms of infection control and wound healing remain to be determined; the potential benefit of bactericidal activity must be balanced against cytotoxicity, and the prevalence and potential transmission of the silver tolerant phenotype must also be assessed.

A clinical and in vitro assessment of outpatient parenteral benzylpenicillin and ceftriaxone combination therapy for enterococcal endovascular infections.

BACKGROUND: Amoxicillin plus ceftriaxone combination therapy is now standard of care for enterococcal endocarditis. Due to amoxicillin instability in infusion devices, benzylpenicillin plus ceftriaxone may be substituted to facilitate outpatient parenteral antimicrobial therapy (OPAT) delivery, despite lack of guideline endorsement. OBJECTIVES: To assess the clinical efficacy of benzylpenicillin plus ceftriaxone for the management of enterococcal endovascular infections, in addition to assessing this combination's in vitro synergy. PATIENTS AND METHODS: Retrospective cohort study assessing unplanned readmissions, relapses and mortality for 20 patients with endovascular Enterococcus faecalis infections treated with benzylpenicillin plus ceftriaxone delivered via OPAT. For a subset of isolates, synergism for both amoxicillin and benzylpenicillin in combination with ceftriaxone was calculated using a chequerboard method. RESULTS: Patients had endovascular infections of native cardiac valves (n = 11), mechanical or bioprosthetic cardiac valves (n = 7), pacemaker leads (n = 1) or left ventricular assistant devices (n = 1). The median duration of OPAT was 22 days, and the most frequent antimicrobial regimen was benzylpenicillin 14 g/day via continuous infusion and ceftriaxone 4 g once daily via short infusion. Rates of unplanned readmissions were high (30%), although rates of relapsed bacteraemia (5%) and 1 year mortality (15%) were comparable to the published literature. Benzylpenicillin less frequently displayed a synergistic interaction with ceftriaxone when compared with amoxicillin (3 versus 4 out of 6 isolates). CONCLUSIONS: Lower rates of synergistic antimicrobial interaction and a significant proportion of unplanned readmissions suggest clinicians should exercise caution when treating enterococcal endovascular infection utilizing a combination of benzylpenicillin and ceftriaxone via OPAT.

Revisiting the inoculum effect for Streptococcus pyogenes with a hollow fibre infection model.

Severe, invasive Streptococcus pyogenes (Strep A) infections result in greater than 500,000 deaths annually. First line treatment for such infections is benzylpenicillin, often with the addition of clindamycin, but treatment failure can occur with this regimen. This failure has been partially attributed to the inoculum effect, which presents as reduced antibiotic susceptibility during high bacterial density and plateau-phase growth. Hollow fibre infection models (HFIM) have been proposed as an in vitro alternative to in vivo research to study these effects. To re-evaluate the inoculum effect for benzylpenicillin, clindamycin, linezolid, and trimethoprim-sulfamethoxazole using a Strep A HFIM. Differential antibiotic susceptibility of Strep A was measured in a HFIM starting from low- and high-density inocula with an average difference in bacterial concentration of 56-fold. Dynamic antibiotic concentrations were delivered over 48 h to simulate in vivo human pharmacokinetics in an in vitro model. Differences in antibiotic susceptibility were measured by plate count of colony-forming units over time. Inoculum effects were seen in benzylpenicillin and linezolid at 24 h, and benzylpenicillin, linezolid, and clindamycin at 48 h. The effect size was greatest for continuously infused benzylpenicillin at 48 h with a log10-fold difference of 4.02 between groups. No inoculum effect was seen in trimethoprim-sulfamethoxazole, with a maximal log10-fold difference of 0.40. Inoculum effects were seen using benzylpenicillin, linezolid, and clindamycin, which may predict reduced clinical efficacy following treatment delay. The model has proven robust and largely in agreeance with published data, recommending it for further Strep A study.