Evaluation of short exposure times of antimicrobial wound solutions against microbial biofilms: from in vitro to in vivo

Objectives

Test the performance of topical antimicrobial wound solutions against microbial biofilms using in vitro, ex vivo and in vivo model systems at clinically relevant exposure times.

Methods

Topical antimicrobial wound solutions were tested under three different conditions: (in vitro) 4% w/v Melaleuca oil, polyhexamethylene biguanide, chlorhexidine, povidone iodine and hypochlorous acid were tested at short duration exposure times for 15 min against 3 day mature biofilms of Staphylococcus aureus and Pseudomonas aeruginosa; (ex vivo) hypochlorous acid was tested in a porcine skin explant model with 12 cycles of 10 min exposure, over 24 h, against 3 day mature P. aeruginosa biofilms; and (in vivo) 4% w/v Melaleuca oil was applied for 15 min exposure, daily, for 7 days, in 10 patients with chronic non-healing diabetic foot ulcers complicated by biofilm.

Results

In vitro assessment demonstrated variable efficacy in reducing biofilms ranging from 0.5 log₁₀ reductions to full eradication. Repeated instillation of hypochlorous acid in a porcine model achieved <1 log₁₀ reduction (0.77 log₁₀, P = 0.1). Application of 4% w/v Melaleuca oil in vivo resulted in no change to the total microbial load of diabetic foot ulcers complicated by biofilm (median log₁₀ microbial load pre-treatment = 4.9 log₁₀ versus 4.8 log₁₀, P = 0.43).

Conclusions

Short durations of exposure to topical antimicrobial wound solutions commonly utilized by clinicians are ineffective against microbial biofilms, particularly when used in vivo. Wound solutions should not be used as a sole therapy and clinicians should consider multifaceted strategies that include sharp debridement as the gold standard.

Effect of cadexomer iodine on the microbial load and diversity of chronic non-healing diabetic foot ulcers complicated by biofilm in vivo

Objectives: The performance of cadexomer iodine was determined against microbial populations from chronic non-healing diabetic foot ulcers (DFUs) complicated by biofilm in vivo, using molecular, microscopy and zymography methods.

Methods: Chronic non-healing DFUs due to suspected biofilm involvement were eligible for enrolment. DNA sequencing and real-time quantitative PCR was used to determine the microbial load and diversity of tissue punch biopsies obtained pre- and post-treatment. Scanning electron microscopy and/or fluorescence in situ hybridization confirmed the presence or absence of biofilm. Zymography was used to determine levels of wound proteases.

Results: Seventeen participants were recruited over a 6 month period. Scanning electron microscopy and or fluorescence in situ hybridization confirmed the presence of biofilm in all samples. Eleven participants exhibited log₁₀ reductions in microbial load after treatment (range 1–2 log₁₀) in comparison with six patients who experienced <1 log₁₀ reduction (P = 0.04). Samples were tested for levels of wound proteases pre- and post-treatment. Reductions in the microbial load correlated to reductions in wound proteases pre- and post-treatment (P = 0.03).

Conclusions: To the best of our knowledge, this study represents the first in vivo evidence, employing a range of molecular and microscopy techniques, of the ability of cadexomer iodine to reduce the microbial load of chronic non-healing DFUs complicated by biofilm. Further analyses correlating log reductions to optimal duration of therapy and improvements in clinical parameters of wound healing in a larger cohort are required.

Next Generation DNA Sequencing of Tissues from Infected Diabetic Foot Ulcers

We used next generation DNA sequencing to profile the microbiome of infected Diabetic Foot Ulcers (DFUs). The microbiota was correlated to clinical parameters and treatment outcomes to determine if directed antimicrobial therapy based on conventional microbiological cultures are relevant based on genomic analysis. Patients≥18years presenting with a new Diabetic Foot Infection (DFI) who had not received topical or oral antimicrobials in the two weeks prior to presentation, were eligible for enrolment. Tissue punch biopsies were obtained from infected DFUs for analysis. Demographics, clinical and laboratory data were collected and correlated against microbiota data. Thirty-nine patients with infected DFUs were recruited over twelve-months. Shorter duration DFUs (<six weeks) all had one dominant bacterial species (n=5 of 5, 100%, p<0.001), Staphylococcus aureus in three cases and Streptococcus agalactiae in two. Longer duration DFUs (≥six weeks) were diversely polymicrobial (p<0.01) with an average of 63 (range 19-125) bacterial species. Severe DFIs had complex microbiomes and were distinctly dissimilar to less severe infections (p=0.02), characterised by the presence of low frequency microorganisms. Nineteen patients (49%) during the study period experienced antimicrobial treatment failure, but no overall differences existed in the microbiome of patients who failed therapy and those who experienced treatment success (p=0.2). Our results confirm that short DFUs have a simpler microbiome consisting of pyogenic cocci but chronic DFUs have a highly polymicrobial microbiome. The duration of a DFU may be useful as a guide to directing antimicrobial therapy.

Can molecular DNA-based techniques unravel the truth about diabetic foot infections?

Diabetes foot infections are a common condition and a major causal pathway to lower extremity amputation. Identification of causative pathogens is vital in directing antimicrobial therapy. Historically, clinicians have relied upon culture-dependent techniques that are now acknowledged as both being selective for microorganisms that thrive under the physiological and nutritional constraints of the microbiology laboratory and that grossly underestimate the microbial diversity of a sample. The amplification and sequence analysis of the 16S rRNA gene has revealed a diversity of microorganisms in diabetes foot infections, extending the view of the diabetic foot microbiome. The interpretation of these findings and their relevance to clinical care remains largely unexplored. The advent of molecular methods that are culture-independent and employ massively parallel DNA sequencing technology represents a potential 'game changer'. Metagenomics and its shotgun approach to surveying all DNA within a sample (whole genome sequencing) affords the possibility to characterize not only the microbial diversity within a diabetes foot infection (i.e. 'which microorganisms are present') but the biological functions of the community such as virulence and pathogenicity (i.e. 'what are the microorganisms capable of doing'), moving the focus from single species as pathogens to groups of species. This review will examine the new molecular techniques for exploration of the microbiome of infected and uninfected diabetic foot ulcers, exploring the potential of these new technologies and postulating how they could translate to improved clinical care. Copyright © 2016 John Wiley & Sons, Ltd.

Primary care referral to multidisciplinary high risk foot services - too few, too late

Background

To determine if patients with no contact with a multi-disciplinary team High Risk Foot Service (MDT-HRFS) had an increased rate of hospital admission for diabetes foot infection compared to patients with contact. Secondary aims were to report on clinical outcomes.

Methods

A retrospective study was conducted at a major tertiary referral hospital in metropolitan Sydney over 12 months. An ICD-10 search of the electronic medical record system and paper medical charts identified patients with diabetes mellitus (type 1 or type 2) and a primary admission for diabetes foot infection (DFI). Patients were categorised as having contact or no contact with an MDT-HRFS.

Results

One hundred ninety-six hospital admissions (156 patients) were identified with DFI over a 12-month period. Patients with no contact with a MDT-HRFS represented three quarters of admissions (no contact = 116, 74.7 % vs. contact = 40, 25.6 %, p = 0.0001) and presented with more severe infection (no contact = 39 vs. contact = 12). The odds of lower extremity amputation increased five-fold when both no contact and severe infection occurred in combination (no contact with severe infection and amputation = 34, 82.9 % vs. contact with severe infection and amputation = 7, 17.1 %, OR 4.9, 95 % CI 1.1–21.4, p = 0.037). Using estimates of both the contact and no contact population of people with diabetes and high-risk feet and assuming the risk of amputation was the same, than the number of expected amputations in the no contact group should have been 55, however the observed number was 77, 22 more than expected (p = 0.0001).

Conclusions

Patients with no contact with a MDT-HRFS represented the majority of admissions for DFIs to a tertiary referral hospital. This group on population estimates appears to be at high risk of amputation of the lower extremity and therefore early referral of this high-risk group might lower this risk.

The effect of diabetes mellitus on costs and length of stay in patients with peripheral arterial disease undergoing vascular surgery

OBJECTIVE

To determine the impact of diabetes mellitus (DM) and other comorbidities on length of stay (LOS) and costs in patients with peripheral arterial disease (PAD) admitted to a vascular surgical unit.

METHODS

A retrospective study was conducted between January 2011 and July 2012 at a tertiary referral hospital in Sydney. Demographic, laboratory, and operative data were obtained from the Australasian Vascular Audit database and hospital diagnostic-related group (DRG) reports. Patients with confirmed PAD with or without DM requiring hospital admission for a diagnosis of claudication, rest pain, ulcer/gangrene, and infection that required lower limb surgical intervention were included. Associations between LOS, surgical procedure, and DRG were explored.

RESULTS

Five hundred and sixty-eight admissions (492 patients) were identified: 292 admissions with PAD and 276 admissions with PAD in conjunction with DM (PADDM). Mean LOS for patients with PAD was 10 ± 13.7 days compared with 15 ± 18.2 days for PADDM (p < .01; 95% confidence interval 2.7-8.0). LOS and costs were greatest in patients with PADDM undergoing major amputation (37 ± 13.7 days; US$42,236; p < .01). Analysis of variance indicated that the best predictors of LOS were the presence of DM, bypass surgery, amputation, chronic kidney disease (CKD) stage V, infection, and emergency admission. Over 18 months, the estimated total inpatient costs associated with lower limb intervention for PAD with and without DM amounted to US$7,598,597. People with DM incurred greater inpatient costs, averaging US$1,912 more per episode of admission and a total of US$528,029 over 18 months.

CONCLUSION

The impact of diabetes as a comorbid condition in patients with PAD is significant, both clinically and economically. Factors that predict increased LOS in patients with PAD are DM, bypass surgery, amputation, CKD stage V, infection, and emergency admission.

Pedal osteomyelitis in patients with diabetes: a retrospective audit from Saudi Arabia

OBJECTIVE

To examine the characteristics of patients presenting to the emergency room and the specialist diabetes foot clinic with pedal osteomyelitis (PO).

METHOD

A retrospective study was conducted at a regional hospital. The charts of patients with suspected PO who presented during the period 1 January to 31 December 2011 were analysed. Demographics, biochemistry and microbiological data were obtained. Bone biopsies were performed by the attending clinician either during surgical removal of infected bone, or percutaneously under guided fluoroscopy through non-infected tissue.

RESULTS

Sixty-six cases of osteomyelitis affecting 102 joints were noted. The study population consisted of 44 men, mean age 62.9 +/- 1.3 years, and 22 women, mean age of 57.6 +/- 10.6 years. Gram-positive bacteria were the predominating pathogens (p < 0.05). Staphylococcus aureus was cultured in 36% of all bone biopsy cases. A predictive trend in HbA1c was observed,where every increase of 1% from the recommended level of 7% was associated with a 10% increase in the likelihood of receiving surgical intervention.

CONCLUSION

S. aureus infection is a major cause of osteomyelitis in interphalangeal joints of the feet of diabetic patients.There is an apparent association with patients who present with diabetic foot osteomyelitis and sub-optimal glycaemic control, requiring surgical intervention.

"The Happy Migrant Effect": perceptions of negative experiences of healthcare by patients with little or no English: a qualitative study across seven language groups

BACKGROUND

The subjective experiences of patients with little or no English who either attended the Emergency Department or were admitted to the wards of a tertiary referral hospital were explored.

SETTING AND METHODS

The reports of experiences from 49 patients of a tertiary referral hospital were analysed using grounded theory methods applied to translated transcriptions from focus groups held with discharged patients in seven languages.

RESULTS

Inability to communicate in English, poor patient and family involvement with staff, a lack of control or powerlessness, staff shortages, staff negligence or incompetence, and treatment delays were reported by some patients. Others tended to discount or minimise the significance of similar experiences, suggesting a construct, "The Happy Migrant Effect," in which there is reluctance to assert healthcare rights. Patients appear "happy" and satisfied, despite problems with their hospital care. Explanatory factors for the construct include extreme powerlessness related to being unable to communicate, a positive comparison of healthcare in the new country compared with the old, patriotism for the new country, cultural norms that proscribe acceptance, politeness or social desirability, self-denigration for not having learnt English and, for a few, a fear of reprisals if they spoke out in complaint.

CONCLUSIONS

Some immigrant patients with poor language skills might not report serious problems with healthcare delivery. In all patients in this study where problems with healthcare were reported, the events were considered to be largely preventable by appropriate language facilitation, patient and family involvement, and provider respect and compassion.

The multi-dimensionality of the FIM motor items precludes an interval scaling using Rasch analysis

Rasch analysis scaling is said to produce an interval scale of Functional Independence Measure (FIM) motor function items. Rasch analysis requires that the data to be analysed represent the influence of a single underlying unidimensional variable. A unidimensional interval scale of activities of daily living means that a person who can perform the most difficult item on a scale can also perform the easiest item. For a FIM motor function interval scale, the ability to climb stairs would imply necessarily and ability to eat normally. As this need not be the case, the FIM motor items do not constitute an adequate interval scale. Eating and walking are different activities, and a unidimensional construct linking them is unsatisfactory. A principal components analysis of the admission FIM motor function items of 515 consecutive patients admitted to an inpatient rehabilitation unit revealed that more than one significant factor was necessary to explain the variance in scores. The counter-factual and statistical evidence argues that a unidimensional construct does not underly the FIM motor function items, and the use of Rasch analysis will not lead to a description of interval properties of the FIM motor function items.

Problems with the ICIDH definition of impairment

This paper discusses problems with the definition of impairment in the International Classification of Impairments, Disabilities, and Handicaps, in particular the inclusion in the definition of the term 'psychological'.

A longitudinal investigation into anxiety and depression in the first 2 years following a spinal cord injury

This study is a 1 year extension of a controlled 1 year follow up study of spinal cord injured persons. The study assessed the extent of spinal cord injury (SCI) persons' depression and anxiety in comparison to an able bodied control group matched for age, sex, education and as far as possible, occupation. Psychological adjustment to SCI was assessed in terms of scores on the Trait Anxiety Inventory and the Beck Depression Inventory. Results obtained at the 2 year follow up were not significantly changed from those obtained over the first year. There was no significant improvement in anxiety and depression scores in the SCI group 2 years post injury. Examination of the SCI scores suggest that psychological morbidity was confined to a group of approximately 30% of persons, whilst the remaining persons were not severely anxious or depressed. Traditional stage models of adjustment to SCI which suggest that the passage of time is associated with better adjustment were not supported by the present data.

Inpatient quality assurance by local analysis of uniform data set data

We constructed a data base in order to examine the profile of patients admitted to a 24 bed inpatient rehabilitation unit at Fairfield Hospital. Data were collected according to the Uniform Data Set for Medical Rehabilitation, and collated and analysed using the Clinical Reporting System database software and the Statistical Package for Interactive Data Analysis statistical software. Outcome data collected included the patients domicile before and after admission, the duration of stay, medical diagnoses before admission to and during the stay in the Rehabilitation Unit, as well as the Functional Independence Measure item scores at admission and discharge. Analysis of the first 100 patients in the data base indicated a duration of stay of 43 +/- 34 days with a right skew distribution. Scatter plots of age and duration of stay, and age and functional improvement showed no bias in the Unit concerning these parameters. The Wilcoxon rank sum test indicated a highly significant difference (P = 0) between entry and exit Functional Independence Measure scores, indicating that patients improved functionally in the unit. Eighty three patients returned home on discharge and only five required admission to a nursing home. With the data base, the course of patients whose performance lies outside the range of normal for the unit can be examined and factors identified which produce a prolonged stay or failure to progress.

Spinal cord injury: a search for determinants of depression two years after the event

A prospective longitudinal study employing repeated measures was used to isolate factors which might predispose a person to depression two years after sustaining spinal cord injury (SCI). Thirty-one subjects who suffered acute spinal injuries resulting in permanent loss of movement, and who had no head injuries or any pre-existing psychopathology, were at least 17 years of age, and who were able to speak English, participated in the study. Using the Beck Depression Inventory (BDI) as a measure of depression, a regression analysis demonstrated that the experience of pain two years post-injury and feeling out of control of one's life prior to hospital discharge were predictive of depression two years post-injury. No demographic variables or injury characteristics such as level of lesion or completeness of lesion were related to long-term depression. Pain management and rehabilitation techniques that enhance the individual's belief of control over their lives are therefore recommended as interventions that could act to reduce depression in the long term in persons with spinal cord injury.

Anxiety and depression over the first year of spinal cord injury: a longitudinal study

The literature concerning the psychological consequences following spinal cord injury (SCI) indicates a discordance between clinical impressions and empirical research. Although many studies report that psychological morbidity is not an inevitable consequence of SCI, much of this research is characterised by methodological inadequacies and the conclusions are therefore tenuous. The present study assessed 41 persons with SCI for depression and anxiety using objective psychological measures on three occasions over the first year of SCI and compared them with 41 able bodied controls matched for age, sex, education and, as far as possible, occupation. Results demonstrated significant differences between the two groups, with the SCI group being more anxious and depressed. However, psychological morbidity was not an inevitable consequence of SCI, with group means reflecting mild levels of depression and anxiety. No significant differences were found across time and no interactions between groups and time were detected. Implications for the treatment of SCI are discussed.

Task-dependent changes in the responses to low-threshold cutaneous afferent volleys in the human lower limb

1. In seven human subjects who were standing without support the sural nerves were stimulated electrically using trains of non-painful stimuli (five pulses at 300 Hz), designed to activate afferents from cutaneous mechanoreceptors. The reflex effects of the stimulus train on different muscles of the ipsilateral and contralateral legs were sought in post-stimulus averages of rectified EMG. Changes in the pattern of reflex influence were investigated when the subjects maintained different postures. 2. Clear reflex responses were seen in ipsilateral tibialis anterior, soleus, biceps femoris and vastus lateralis, but only when the muscles were actively contracting. In each muscle, inhibition was the dominant reflex response within the first 100 ms. In four of the seven subjects, reflex changes were detectable in the contralateral tibialis anterior and soleus, the peak-to-peak modulation within the first 200 ms being 25-50% of that for the homologous ipsilateral muscle. 3. When subjects attempted to stand on a tilted platform, an unstable platform or on one leg with the other flexed, different combinations of muscles were active, involving both flexors and extensors or predominantly flexors or predominantly extensors. In each posture the reflex effects were demonstrable only in the active muscles. 4. With ipsilateral tibialis anterior, there were task-dependent changes in the short-latency components of the EMG response, approximately 60 ms and 80 ms after the stimulus. When seated performing voluntary contractions these components were difficult to define, and when standing on a platform tilted toe-up they were small. When the ipsilateral leg was flexed or when standing on an unstable base, these early components were more prominent in each subject. With contralateral tibialis anterior, the dominant reflex pattern was inhibition when seated and contracting voluntarily, and facilitation during bipedal stance tilted toe-up. These changes in reflex pattern could not be explained by different levels of background contraction. 5. It is concluded that cutaneous mechanoreceptors of the foot have widespread reflex actions on muscles throughout both limbs, particularly the ipsilateral limb, and that the reflex pattern in different muscles and within a single muscle may change dependent on the task that the subject is undertaking. These task-dependent changes indicate plasticity in the expression of cutaneous reflex activity, affecting both short-latency spinal as well as long-latency pathways.

Trimethoprim-sulphamethoxazole and thrombocytopenia

Thrombocytopenia is an uncommon but serious side effect of the antimicrobial combination of trimethoprim and sulphamethoxazole. Thirty-one cases in seven years, including two deaths, have been reported to the Australian Adverse Drug Reactions Registry. Females were affected twice as frequently as males. In 70% of the patients platelet counts were 20x10(9)/L or less. Thrombocytopenia which is associated with this agent may occur at any age.