Growth of MRSA and Pseudomonas aeruginosa in a fine-celled foam model containing sessile commensal skin bacteria

Sessile cultures of the skin bacteria Staphylococcus saprophyticus and Corynebacterium xerosis were grown using novel fine-celled foam substrata to test the outcome of challenge by methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa under three growth medium regimens (simulated sweat, simulated serum or simulated sweat substituted with simulated serum during the microbial challenge). S. saprophyticus and C. xerosis significantly limited MRSA and P. aeruginosa immigration respectively, under the simulated sweat and serum medium regimes. Under the substitution medium regime however, MRSA and P. aeruginosa integrated into pre-established biofilms to a significantly greater extent, attaining cell densities similar to the axenic controls. The outcome of challenge was influenced by the medium composition and test organism but could not be predicted based on planktonic competition assays or growth dynamics. Interactions between skin and wound isolates could be modelled using the fine-celled foam-based system. This model could be used to further investigate interactions and also in preclinical studies of antimicrobial wound care regimens

The Visualization of Biofilms in Chronic Diabetic Foot Wounds Using Routine Diagnostic Microscopy Methods

Diabetic foot wounds are commonly colonised by taxonomically diverse microbial communities and may additionally be infected with specific pathogens. Since biofilms are demonstrably less susceptible to antimicrobial agents than are planktonic bacteria, and may be present in chronic wounds, there is increasing interest in their aetiological role. In the current investigation, the presence of structured microbial assemblages in chronic diabetic foot wounds is demonstrated using several visualization methods. Debridement samples, collected from the foot wounds of diabetic patients, were histologically sectioned and examined using bright-field, fluorescence, and environmental scanning electron microscopy and assessed by quantitative differential viable counting. All samples (n = 26) harboured bioburdens in excess of 5 log10 CFU/g. Microcolonies were identified in 4/4 samples by all three microscopy methods, although bright-field and fluorescence microscopy were more effective at highlighting putative biofilm morphology than ESEM. Results in this pilot study indicate that bacterial microcolonies and putative biofilm matrix can be visualized in chronic wounds using florescence microscopy and ESEM, but also using the simple Gram stain

Abdominal functional electrical stimulation to assist ventilator weaning in critical illness: a double-blinded, randomised, sham-controlled pilot study

BACKGROUND: For every day a person is dependent on mechanical ventilation, respiratory and cardiac complications increase, quality of life decreases and costs increase by > $USD 1500. Interventions that improve respiratory muscle function during mechanical ventilation can reduce ventilation duration. The aim of this pilot study was to assess the feasibility of employing an abdominal functional electrical stimulation (abdominal FES) training program with critically ill mechanically ventilated patients. We also investigated the effect of abdominal FES on respiratory muscle atrophy, mechanical ventilation duration and intensive care unit (ICU) length of stay. METHODS: Twenty critically ill mechanically ventilated participants were recruited over a 6-month period from one metropolitan teaching hospital. They were randomly assigned to receive active or sham (control) abdominal FES for 30 min, twice per day, 5 days per week, until ICU discharge. Feasibility was assessed through participant compliance to stimulation sessions. Abdominal and diaphragm muscle thickness were measured using ultrasound 3 times in the first week, and weekly thereafter by a blinded assessor. Respiratory function was recorded when the participant could first breathe independently and at ICU discharge, with ventilation duration and ICU length of stay also recorded at ICU discharge by a blinded assessor. RESULTS: Fourteen of 20 participants survived to ICU discharge (8, intervention; 6, control). One control was transferred before extubation, while one withdrew consent and one was withdrawn for staff safety after extubation. Median compliance to stimulation sessions was 92.1% (IQR 5.77%) in the intervention group, and 97.2% (IQR 7.40%) in the control group (p = 0.384). While this pilot study is not adequately powered to make an accurate statistical conclusion, there appeared to be no between-group thickness changes of the rectus abdominis (p = 0.099 at day 3), diaphragm (p = 0.652 at day 3) or combined lateral abdominal muscles (p = 0.074 at day 3). However, ICU length of stay (p = 0.011) and ventilation duration (p = 0.039) appeared to be shorter in the intervention compared to the control group. CONCLUSIONS: Our compliance rates demonstrate the feasibility of using abdominal FES with critically ill mechanically ventilated patients. While abdominal FES did not lead to differences in abdominal muscle or diaphragm thickness, it may be an effective method to reduce ventilation duration and ICU length of stay in this patient group. A fully powered study into this effect is warranted. TRIAL REGISTRATION: The Australian New Zealand Clinical Trials Registry, ACTRN12617001180303. Registered 9 August 2017

Abdominal functional electrical stimulation to improve respiratory function after spinal cord injury: a systematic review and meta-analysis

Objectives: Abdominal functional electrical stimulation (abdominal FES) is the application of a train of electrical pulses to the abdominal muscles, causing them to contract. Abdominal FES has been used as a neuroprosthesis to acutely augment respiratory function and as a rehabilitation tool to achieve a chronic increase in respiratory function after abdominal FES training, primarily focusing on patients with spinal cord injury (SCI). This study aimed to review the evidence surrounding the use of abdominal FES to improve respiratory function in both an acute and chronic manner after SCI. Settings: A systematic search was performed on PubMed, with studies included if they applied abdominal FES to improve respiratory function in patients with SCI. Methods: Fourteen studies met the inclusion criteria (10 acute and 4 chronic). Low participant numbers and heterogeneity across studies reduced the power of the meta-analysis. Despite this, abdominal FES was found to cause a significant acute improvement in cough peak flow, whereas forced exhaled volume in 1 s approached significance. A significant chronic increase in unassisted vital capacity, forced vital capacity and peak expiratory flow was found after abdominal FES training compared with baseline. Conclusions: This systematic review suggests that abdominal FES is an effective technique for improving respiratory function in both an acute and chronic manner after SCI. However, further randomised controlled trials, with larger participant numbers and standardised protocols, are needed to fully establish the clinical efficacy of this technique

PARADIGM-2: Two parallel phase I studies of olaparib and radiotherapy or olaparib and radiotherapy plus temozolomide in patients with newly diagnosed glioblastoma, with treatment stratified by MGMT status

Glioblastoma has a dismal prognosis and molecular targeted agents have failed to improve outcomes to date. PARADIGM-2 is a phase I dose escalation study evaluating olaparib plus radiotherapy ± temozolomide in newly diagnosed glioblastoma, using MGMT methylation status to stratify patients and inform treatment schedules

Simultaneous assessment of acidogenesis-mitigation and specific bacterial growth-inhibition by dentifrices

Dentifrices can augment oral hygiene by inactivating bacteria and at sub-lethal concentrations may affect bacterial metabolism, potentially inhibiting acidogenesis, the main cause of caries. Reported herein is the development of a rapid method to simultaneously measure group-specific bactericidal and acidogenesis-mitigation effects of dentifrices on oral bacteria. Saliva was incubated aerobically and anaerobically in Tryptone Soya Broth, Wilkins-Chalgren Broth with mucin, or artificial saliva and was exposed to dentifrices containing triclosan/copolymer (TD); sodium fluoride (FD); stannous fluoride and zinc lactate (SFD1); or stannous fluoride, zinc lactate and stannous chloride (SFD2). Minimum inhibitory concentrations (MIC) were determined turbidometrically whilst group-specific minimum bactericidal concentrations (MBC) were assessed using growth media and conditions selective for total aerobes, total anaerobes, streptococci and Gram-negative anaerobes. Minimum acid neutralization concentration (MNC) was defined as the lowest concentration of dentifrice at which acidification was inhibited. Differences between MIC and MNC were calculated and normalized with respect to MIC to derive the combined inhibitory and neutralizing capacity (CINC), a cumulative measure of acidogenesis-mitigation and growth inhibition. The overall rank order for growth inhibition potency (MIC) under aerobic and anaerobic conditions was: TD> SFD2> SFD1> FD. Acidogenesis-mitigation (MNC) was ordered; TD> FD> SFD2> SFD1. CINC was ordered TD> FD> SFD2> SFD1 aerobically and TD> FD> SFD1> SFD2 anaerobically. With respect to group-specific bactericidal activity, TD generally exhibited the greatest potency, particularly against total aerobes, total anaerobes and streptococci. This approach enables the rapid simultaneous evaluation of acidity mitigation, growth inhibition and specific antimicrobial activity by dentifrices

Comparative antibacterial potential of selected aldehyde-based biocides and surfactants against planktonic Pseudomonas fluorescens

The antimicrobial efficacy of two aldehydebased biocides (glutaraldehyde, GTA, and orthophthalaldehyde, OPA) and two surfactants (cetyltrimethyl ammonium bromide, CTAB, and sodium dodecyl sulphate, SDS) was tested against planktonic Pseudomonas fluorescens. The antimicrobial effects were evaluated by respiratory activity as a measure of the oxygen uptake rate, adenosine triphosphate (ATP) release, outer membrane proteins (OMP) expression and cellular colour changes. The results were compared with the bacterial characteristics without chemical treatment. Tests in the presence of bovine serum albumin (BSA), in order to mimic a disinfection process in the real situation under dirty conditions, were performed according to the European Standard EN-1276. P. fluorescens was completely inactivated with OPA (minimum bactericidal concentration, MBC = 0.5 mM) and CTAB (MBC = 5 mM) and was resistant to GTA and SDS. Only CTAB promoted cellular disruption and consequent ATP release. The antimicrobial action of the chemicals tested was significantly reduced when BSA was introduced into the bacterial cultures, increasing markedly the MBC values. Additionally, the presence of BSA acted as a disruption protective agent when CTAB was applied and stimulated the bacterial respiratory activity when lower concentrations of SDS were tested. The OMP of the bacterial cells was affected by the application of both surfactants. OMP expression remained unaltered after biocide treatment. Bacterial colour change was noticed after treatment with biocides and surfactants. In summary, P. fluorescens was extremely resistant to GTA and SDS, with antimicrobial action being quenched markedly by the reaction with BSA.Instituto de Biotecnologia e Química Fina (IBQF).Fundação para a Ciência e a Tecnologia (FCT) - (Project CHEMBIO - POCI/BIO/61872/2004

Differential Actions of Chlorhexidine on the Cell Wall of Bacillus subtilis and Escherichia coli

Chlorhexidine is a chlorinated phenolic disinfectant used commonly in mouthwash for its action against bacteria. However, a comparative study of the action of chlorhexidine on the cell morphology of Gram-positive and Gram-negative bacteria is lacking. In this study, the actions of chlorhexidine on the cell morphology were identified with the aids of electron microscopy. After exposure to chlorhexidine, numerous spots of indentation on the cell wall were found in both Bacillus subtilis and Escherichia coli. The number of indentation spots increased with time of incubation and increasing chlorhexidine concentration. Interestingly, the dented spots found in B. subtilis appeared mainly at the hemispherical caps of the cells, while in E. coli the dented spots were found all over the cells. After being exposed to chlorhexidine for a prolonged period, leakage of cellular contents and subsequent ghost cells were observed, especially from B subtilis. By using 2-D gel/MS-MS analysis, five proteins related to purine nucleoside interconversion and metabolism were preferentially induced in the cell wall of E. coli, while three proteins related to stress response and four others in amino acid biosynthesis were up-regulated in the cell wall materials of B. subtilis. The localized morphological damages together with the biochemical and protein analysis of the chlorhexidine-treated cells suggest that chlorhexidine may act on the differentially distributed lipids in the cell membranes/wall of B. subtilis and E. coli

Hypervirulent Clostridium difficile PCR-Ribotypes Exhibit Resistance to Widely Used Disinfectants

The increased prevalence of Clostridium difficile infection (CDI) has coincided with enhanced transmissibility and severity of disease, which is often linked to two distinct clonal lineages designated PCR-ribotype 027 and 017 responsible for CDI outbreaks in the USA, Europe and Asia. We assessed sporulation and susceptibility of three PCR-ribotypes; 012, 017 and 027 to four classes of disinfectants; chlorine releasing agents (CRAs), peroxygens, quaternary ammonium compounds (QAC) and biguanides. The 017 PCR-ribotype, showed the highest sporulation frequency under these test conditions. The oxidizing biocides and CRAs were the most efficacious in decontamination of C. difficile vegetative cells and spores, the efficacy of the CRAs were concentration dependent irrespective of PCR-ribotype. However, there were differences observed in the susceptibility of the PCR-ribotypes, independent of the concentrations tested for Virkon®, Newgenn®, Proceine 40® and Hibiscrub®. Whereas, for Steri7® and Biocleanse® the difference observed between the disinfectants were dependent on both PCR-ribotype and concentration. The oxidizing agent Perasafe® was consistently efficacious across all three PCR ribotypes at varying concentrations; with a consistent five Log10 reduction in spore titre. The PCR-ribotype and concentration dependent differences in the efficacy of the disinfectants in this study indicate that disinfectant choice is a factor for llimiting the survival and transmission of C. difficile spores in healthcare settings