Preventing empirical antibiotic treatment failure in migrant populations: screening by infection risk, not ethnic background

Multidrug-resistant organisms (MDROs) are a major international health threat. In many low and middle-income countries poorly regulated antibiotic use, limited surveillance, and inadequate sanitation give rise to high rates of antibiotic resistance. A resulting reliance on last-line antibiotic options further contributes to the emergence of MDROs. The potential for these pathogens to spread across international borders is a matter of considerable concern. However, this problem is commonly framed as primarily a threat to the health security of countries where resistance is not yet endemic. In fact, it is little acknowledged that those at greatest risk from antibiotic treatment failure are individuals who move from regions of high MDRO prevalence to settings where standard empirical treatment options remain largely effective. In this perspective, we highlight the poor treatment outcomes for disseminated bacterial infections in individuals who have moved from settings in which MDROs are common to those where MDROs are currently less common. We discuss MDRO screening strategies that could avoid stigmatizing vulnerable populations by focusing on future risk of disseminated infection, rather than past risk of acquisition. In practical terms, this means screening individuals before childbirth, immunosuppressive treatments, major surgery, or other events associated with disseminated infection risk, rather than prioritizing screening for individuals from regions with high carriage rates. We argue that such measures would reduce antibiotic treatment failure and improve outcomes while protecting migrant populations from the divisive consequences of targeted screening programs.

Cohort profile: GRACE - a residential aged care cohort examining factors influencing antimicrobial resistance carriage

BACKGROUND

The emergence of antimicrobial-resistant bacteria represents a considerable threat to human health, particularly for vulnerable populations such as those living in residential aged care. However, antimicrobial resistance carriage and modes of transmission remain incompletely understood. The Generating evidence on antimicrobial Resistance in the Aged Care Environment (GRACE) study was established to determine principal risk factors of antimicrobial resistance carriage and transmission in residential aged care facilities (RACFs). This article describes the cohort characteristics, national representation, and planned analyses for this study.

METHODS

Between March 2019 and March 2020, 279 participants were recruited from five South Australian RACFs. The median age was 88.6 years, the median period in residence was 681 days, and 71.7% were female. A dementia diagnosis was recorded in 54.5% and more than two thirds had moderate to severe cognitive impairment (68.8%). 61% had received at least one course of antibiotics in the 12 months prior to enrolment.

RESULTS

To investigate the representation of the GRACE cohort to Australians in residential aged care, its characteristics were compared to a subset of the historical cohort of the Registry of Senior Australians (ROSA). This included 142,923 individuals who were permanent residents of RACFs on June 30th, 2017. GRACE and ROSA cohorts were similar in age, sex, and duration of residential care, prevalence of health conditions, and recorded dementia diagnoses. Differences were observed in care requirements and antibiotic exposure (both higher for GRACE participants). GRACE participants had fewer hospital visits compared to the ROSA cohort, and a smaller proportion were prescribed psycholeptic medications.

CONCLUSIONS

We have assembled a cohort of aged care residents that is representative of the Australian aged care population, and which provides a basis for future analyses. Metagenomic data isolated from participants and built environments will be used to determine microbiome and resistome characteristics of an individual and the facility. Individual and facility risk exposures will be aligned with metagenomic data to identify principal determinants for antimicrobial resistance carriage. Ultimately, this analysis will inform measures aimed at reducing the emergence and spread of antimicrobial resistant pathogens in this high-risk population.

Targeted reduction of airborne viral transmission risk in long-term residential aged care

COVID-19 has demonstrated the devastating consequences of the rapid spread of an airborne virus in residential aged care. We report the use of CO2-based ventilation assessment to empirically identify potential 'super-spreader' zones within an aged care facility, and determine the efficacy of rapidly implemented, inexpensive, risk reduction measures.

Ear microbiota and middle ear disease: a longitudinal pilot study of Aboriginal children in a remote south Australian setting

Background

Otitis media (OM) is a major disease burden in Australian Aboriginal children, contributing to serious long-term health outcomes. We report a pilot analysis of OM in children attending an outreach ear and hearing clinic in a remote south Australian community over a two-year period. Our study focuses on longitudinal relationships between ear canal microbiota characteristics with nasopharyngeal microbiota, and clinical and treatment variables.

Results

Middle ear health status were assessed in 19 children (aged 3 months to 8 years) presenting in remote western South Australia and medical interventions were recorded. Over the two-year study period, chronic suppurative OM was diagnosed at least once in 7 children (37%), acute OM with perforation in 4 children (21%), OM with effusion in 11 children (58%), while only 1 child had no ear disease. Microbiota analysis of 19 children (51 sets of left and right ear canal swabs and nasopharyngeal swabs) revealed a core group of bacterial taxa that included Corynebacterium, Alloiococcus, Staphylococcus, Haemophilus, Turicella, Streptococcus, and Pseudomonas. Within-subject microbiota similarity (between ears) was significantly greater than inter-subject similarity, regardless of differences in ear disease (p = 0.0006). Longitudinal analysis revealed changes in diagnosis to be associated with more pronounced changes in microbiota characteristics, irrespective of time interval. Ear microbiota characteristics differed significantly according to diagnosis (P (perm) = 0.0001). Diagnoses featuring inflammation with tympanic membrane perforation clustering separately to those in which the tympanic membrane was intact, and characterised by increased Proteobacteria, particularly Haemophilus influenzae, Moraxella catarrhalis, and Oligella. While nasopharyngeal microbiota differed significantly in composition to ear microbiota (P (perm) = 0.0001), inter-site similarity was significantly greater in subjects with perforated tympanic membranes, a relationship that was associated with the relative abundance of H. influenzae in ear samples (r_s = − 0.71, p = 0.0003). Longitudinal changes in ear microbiology reflected changes in clinical signs and treatment.

Conclusions

Children attending the ear and hearing clinic in a remote Aboriginal community present with a broad spectrum of OM conditions and severities, consistent with other remote Aboriginal communities. Ear microbiota characteristics align with OM diagnosis and change with disease course. Nasopharyngeal microbiota characteristics are consistent with the contribution of acute upper respiratory infection to OM aetiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02436-x.

Prevention of SARS-CoV-2 (COVID-19) transmission in residential aged care using ultraviolet light (PETRA): a two-arm crossover randomised controlled trial protocol

Background

SARS-CoV-2 poses a considerable threat to those living in residential aged care facilities (RACF). RACF COVID-19 outbreaks have been characterised by the rapid spread of infection and high rates of severe disease and associated mortality. Despite a growing body of evidence supporting airborne transmission of SARS-CoV-2, current infection control measures in RACF including hand hygiene, social distancing, and sterilisation of surfaces, focus on contact and droplet transmission. Germicidal ultraviolet (GUV) light has been used widely to prevent airborne pathogen transmission. Our aim is to investigate the efficacy of GUV technology in reducing the risk of SARS-CoV-2 infection in RACF.

Methods

A multicentre, two-arm double-crossover, randomised controlled trial will be conducted to determine the efficacy of GUV devices to reduce respiratory viral transmission in RACF, as an adjunct to existing infection control measures. The study will be conducted in partnership with three aged care providers in metropolitan and regional South Australia. RACF will be separated into paired within-site zones, then randomised to intervention order (GUV or control). The initial 6-week period will be followed by a 2-week washout before crossover to the second 6-week period. After accounting for estimated within-zone and within-facility correlations of infection, and baseline infection rates (10 per 100 person-days), a sample size of n = 8 zones (n = 40 residents/zone) will provide 89% power to detect a 50% reduction in symptomatic infection rate. The primary outcome will be the incidence rate ratio of combined symptomatic respiratory infections for intervention versus control. Secondary outcomes include incidence rates of hospitalisation for complications associated with respiratory infection; respiratory virus detection in facility air and fomite samples; rates of laboratory confirmed respiratory illnesses and genomic characteristics.

Discussion

Measures that can be deployed rapidly into RACF, that avoid the requirement for changes in resident and staff behaviour, and that are effective in reducing the risk of airborne SARS-CoV-2 transmission, would provide considerable benefit in safeguarding a highly vulnerable population. In addition, such measures might substantially reduce rates of other respiratory viruses, which contribute considerably to resident morbidity and mortality.

Trial registration Australian and New Zealand Clinical Trials Registry ACTRN12621000567820 (registered on 14th May, 2021).

Contribution of facility level factors to variation in antibiotic use in long-term care facilities: a national cohort study

OBJECTIVES

To examine national variation in systemic antibiotic use in long-term care facilities (LTCFs) and identify facility characteristics associated with antibiotic utilization.

METHODS

This retrospective cohort study included 312 375 residents of 2536 Australian LTCFs between 2011 and 2016. LTCFs were categorized as low, medium or high antibiotic use facilities according to tertiles of DDDs of systemic antibiotics dispensed per 1000 resident-days. Multivariable logistic regression estimated the associations between facility characteristics (ownership, size, location, medication quality indicator performance, prevalence of after-hours medical practitioner services) and antibiotic use (low versus high).

RESULTS

LTCFs in the lowest and highest antibiotic use categories received a median of 54.3 (IQR 46.5-60.5) and 106.1 (IQR 95.9-122.3) DDDs/1000 resident-days, respectively. Compared with not-for-profit LTCFs in major cities, government-owned non-metropolitan LTCFs were less likely to experience high antibiotic use [adjusted OR (aOR) 0.47, 95% CI 0.24-0.91]. LTCFs with 69-99 residents were less likely to experience high antibiotic use (aOR 0.69, 95% CI 0.49-0.97) than those with 25-47 residents annually. Greater prevalence of medical practitioner services accessed after-hours was associated with high antibiotic use [aOR 1.10 (per 10% increase in after-hours services), 95% CI 1.01-1.21]. South Australian LTCFs (aOR 2.17, 95% CI 1.38-3.39) were more likely, while Queensland (0.43, 95% CI 0.30-0.62) and Western Australian (aOR 0.34, 95% CI 0.21-0.57) LTCFs were less likely to experience high antibiotic use than New South Wales LTCFs.

CONCLUSIONS

Considerable facility level variation in systemic antibiotic use was observed across Australian LTCFs. Identification of facility characteristics associated with antibiotic use provides a basis for targeted stewardship initiatives.

National Trends in Antibiotic Use in Australian Residential Aged Care Facilities, 2005-2016

BACKGROUND

Understanding current patterns of antibiotic use in residential aged care facilities (RACFs) is essential to inform stewardship activities, but limited utilization data exist. This study examined changes in prevalence and consumption of antibiotics in Australian RACFs between 2005-2006 and 2015-2016.

METHODS

This population-based, repeated cross-sectional analysis included all long-term permanent residents of Australian RACFs between July 2005 and June 2016 who were aged ≥ 65 years. The yearly prevalence rate of antibiotic use and number of defined daily doses (DDDs) of systemic antibiotics per 1000 resident-days were determined annually from linked pharmaceutical claims data. Trends were assessed using ordinary least squares regression.

RESULTS

This study included 502 752 residents from 3218 RACFs, with 424.9 million resident-days analyzed. Antibiotics were dispensed on 5 608 126 occasions during the study period, of which 88% were for oral use. Cefalexin, amoxicillin-clavulanic acid, and trimethoprim were the most commonly dispensed antibiotics. The annual prevalence of antibiotic use increased from 63.8% (95% confidence interval [CI], 63.3%-64.4%) to 70.3% (95% CI, 69.9%-70.7%) between 2005-2006 and 2015-2016 (0.8% average annual increase, P < .001). There was a 39% relative increase in total consumption of systemic antibiotics, with utilization increasing from 67.6 to 93.8 DDDs/1000 resident-days during the study period (average annual increase of 2.8 DDDs/1000 resident-days, P < .001).

CONCLUSIONS

This nationwide study showed substantial increases in both prevalence of use and total consumption of antibiotics in Australian RACFs between 2005 and 2016. The increasingly widespread use of antibiotics in Australian RACFs is concerning and points to a need for enhanced efforts to optimize antibiotic use in this setting.

Conventional myelosuppressive chemotherapy for non-haematological malignancy disrupts the intestinal microbiome

Background

The gut microbiota influences many aspects of host physiology, including immune regulation, and is predictive of outcomes in cancer patients. However, whether conventional myelosuppressive chemotherapy affects the gut microbiota in humans with non-haematological malignancy, independent of antibiotic exposure, is unknown.

Methods

Faecal samples from 19 participants with non-haematological malignancy, who were receiving conventional chemotherapy regimens but not antibiotics, were examined prior to chemotherapy, 7–12 days after chemotherapy, and at the end of the first cycle of treatment. Gut microbiota diversity and composition was determined by 16S rRNA gene amplicon sequencing.

Results

Compared to pre-chemotherapy samples, samples collected 7–12 days following chemotherapy exhibited increased richness (mean 120 observed species ± SD 38 vs 134 ± 40; p = 0.007) and diversity (Shannon diversity: mean 6.4 ± 0.43 vs 6.6 ± 0.41; p = 0.02). Composition was significantly altered, with a significant decrease in the relative abundance of gram-positive bacteria in the phylum Firmicutes (pre-chemotherapy median relative abundance [IQR] 0.78 [0.11] vs 0.75 [0.11]; p = 0.003), and an increase in the relative abundance of gram-negative bacteria (Bacteroidetes: median [IQR] 0.16 [0.13] vs 0.21 [0.13]; p = 0.01 and Proteobacteria: 0.015 [0.018] vs 0.03 [0.03]; p = 0.02). Differences in microbiota characteristics from baseline were no longer significant at the end of the chemotherapy cycle.

Conclusions

Conventional chemotherapy results in significant changes in gut microbiota characteristics during the period of predicted myelosuppression post-chemotherapy. Further study is indicated to link microbiome changes during chemotherapy to clinical outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08296-4.

The cystic fibrosis gut as a potential source of multidrug resistant pathogens

BACKGROUND

The emergence of multidrug resistant (MDR) pathogens represents a profound threat to global health. Individuals with CF have amongst the highest cumulative antibiotic exposure of any patient group, including to critically-important last-line agents. While there is little evidence that antibiotic resistance in airway pathogens results in worse clinical outcomes for CF patients, the potential emergence of MDR pathogens in non-respiratory systems, as a consequence of CF care, represents a potential health threat to the wider population, including family and carers.

METHODS

Stool from 19 adults with CF and 16 healthy adult controls was subjected to metagenomic sequencing, to assess faecal resistome, and culture-based analysis. Resistant isolates were identified phenotypically, and genetic determinants of resistance characterised by whole genome sequencing.

RESULTS

CF and control faecal resistomes differed significantly (P = 0.0003). The proportion of reads that mapped to mobile genetic elements was significantly higher in CF (P = 0.014) and the composition was significantly different (P = 0.0001). Notably, CF patients displayed higher carriage of plasmid-mediated aminoglycoside-modifying genes ant(6)-Ib, aac(6')-Ip, and aph(3')-IIIa (P < 0.01). Culture-based analysis supported higher aminoglycoside resistance, with a higher proportion of aminoglycoside-resistant, Gram-negative bacteria (P < 0.0001). Isolated extended spectrum beta lactamase (ESBL)-positive Escherichia coli from CF stool exhibited phenotypic resistance to tobramycin and gentamicin. Genomic analysis showed co-localisation of both aminoglycoside resistance and ESBL genes, consistent with MDR emergence through horizontal gene transfer.

CONCLUSIONS

The carriage of potentially transmissible resistance within the adult CF gut microbiome is considerably greater than in healthy individuals and could contribute to the emergence and dissemination of MDR pathogens.

Australian consensus statements for the regulation, production and use of faecal microbiota transplantation in clinical practice

OBJECTIVE

Faecal microbiota transplantation (FMT) has proved to be an extremely effective treatment for recurrent Clostridioides difficile infection, and there is interest in its potential application in other gastrointestinal and systemic diseases. However, the recent death and episode of septicaemia following FMT highlights the need for further appraisal and guidelines on donor evaluation, production standards, treatment facilities and acceptable clinical indications.

DESIGN

For these consensus statements, a 24-member multidisciplinary working group voted online and then convened in-person, using a modified Delphi approach to formulate and refine a series of recommendations based on best evidence and expert opinion. Invitations to participate were directed to Australian experts, with an international delegate assisting the development. The following issues regarding the use of FMT in clinical practice were addressed: donor selection and screening, clinical indications, requirements of FMT centres and future directions. Evidence was rated using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system.

RESULTS

Consensus was reached on 27 statements to provide guidance on best practice in FMT. These include: (1) minimum standards for donor screening with recommended clinical selection criteria, blood and stool testing; (2) accepted routes of administration; (3) clinical indications; (4) minimum standards for FMT production and requirements for treatment facilities acknowledging distinction between single-site centres (eg, hospital-based) and stool banks; and (5) recommendations on future research and product development.

CONCLUSIONS

These FMT consensus statements provide comprehensive recommendations around the production and use of FMT in clinical practice with relevance to clinicians, researchers and policy makers.

Improving Risk-Benefit in Faecal Transplantation through Microbiome Screening

Faecal microbiota transplantation (FMT) has been shown to be effective in the treatment of a growing number of conditions, and its clinical use continues to rise. However, recent cases of antibiotic-resistant pathogen transmission through FMT, resulting in at least one case of fatal sepsis, highlight the need to reevaluate current donor screening practices. Commensal gut microbes profoundly influence infection risk but are not routinely assessed in donor stool. Extending the assessment of donor material beyond pathogen populations to include the composition and structure of the wider faecal microbiota has the potential to reduce infectious complications in FMT recipients.

DNA extraction approaches substantially influence the assessment of the human breast milk microbiome

In addition to providing nutritional and bioactive factors necessary for infant development, human breast milk contains bacteria that contribute to the establishment of commensal microbiota in the infant. However, the composition of this bacterial community differs considerably between studies. We hypothesised that bacterial DNA extraction methodology from breast milk samples are a substantial contributor to these inter-study differences. We tested this hypothesis by applying five widely employed methodologies to a mock breast milk sample and four individual human breast milk samples. Significant differences in DNA yield and purity were observed between methods (P < 0.05). Microbiota composition, assessed by 16S rRNA gene amplicon sequencing, also differed significantly with extraction methodology (P < 0.05), including in the contribution of contaminant signal. Concerningly, many of the bacterial taxa identified here as contaminants have been reported as components of the breast milk microbiome in other studies. These findings highlight the importance of using stringent, well-validated, DNA extraction methodologies for analysis of the breast milk microbiome, and exercising caution interpreting microbiota data from low-biomass contexts.

Case report: Identification of intra-laboratory blood culture contamination with Staphylococcus aureus by whole genome sequencing

Staphylococcus aureus in blood cultures is rarely considered a contaminant. We report a case of intra-laboratory contamination between blood culture bottles which was confirmed by whole genome sequencing, highlighting the importance of molecular analysis in the clinical laboratory setting.

Optimisation of a propidium monoazide based method to determine the viability of microbes in faecal slurries for transplantation

The efficacy of faecal microbiota transplantation (FMT) as a therapeutic intervention may depend on the viability of the microorganisms in faecal slurries (FS) prepared from donor stool. However, determining the viability of these organisms is challenging. Most microorganisms in stool are refractory to culture using standard techniques, and culture-independent PCR-based methods derive signal from both viable and non-viable cells. Propidium monoazide (PMA) treatment has been shown to be effective in preventing PCR amplification of DNA from non-viable bacteria in a range of contexts. However, this methodology can be sensitive to factors such as bacterial load and sample turbidity. We describe the optimisation of a PMA treatment methodology for FS that restricts quantitative PCR-based bacterial enumeration to viable cells. When applied to concentrated FS (10-25% stool content), PMA treatment at 100 μM concentration was ineffective in preventing DNA amplification from heat-killed cells. Efficacy was not significantly improved by doubling the PMA concentration. However, PMA treatment efficacy was improved markedly following 10-fold sample dilution, and was found to be optimal at 100-fold dilution. Substantial reductions in viable bacterial load could be observed following both freeze-thaw and heat-treatment of FS. This method successfully prevented DNA amplification of heat-killed Pseudomonas and Staphylococcus spiked into stool and could reliably determine the proportion of live bacteria and viable E. coli counts present in fresh and heat-treated stool. With appropriate sample dilution, PMA treatment excluded >97% of non-viable cells from amplification in all assays, without significantly affecting the amplification of DNA from viable cells. This method can be applied to optimise sample processing of FMT donor material, and to characterise bacterial viability within faecal samples more widely.

Not Just Antibiotics: Is Cancer Chemotherapy Driving Antimicrobial Resistance?

The global spread of antibiotic-resistant pathogens threatens to increase the mortality of cancer patients significantly. We propose that chemotherapy contributes to the emergence of antibiotic-resistant bacteria within the gut and, in combination with antibiotics, drives pathogen overgrowth and translocation into the bloodstream. In our model, these processes are mediated by the effects of chemotherapy on bacterial mutagenesis and horizontal gene transfer, the disruption of commensal gut microbiology, and alterations to host physiology. Clinically, this model manifests as a cycle of recurrent sepsis, with each episode involving ever more resistant organisms and requiring increasingly broad-spectrum antimicrobial therapy. Therapies that restore the gut microbiota following chemotherapy or antibiotics could provide a means to break this cycle of infection and treatment failure.

Influence of antimicrobial susceptibility reporting on junior doctors' decision to prescribe antimicrobials inappropriately

Objectives

Inappropriate antimicrobial use drives antimicrobial resistance and is a global public health problem. This study examined whether withholding antimicrobial susceptibilities in combination with interpretive comments on microbiological reports influenced the decision to inappropriately prescribe antibiotics in a controlled survey.

Methods

Seventy junior doctors attending educational sessions were given one of two surveys describing four clinical case vignettes (scenarios) in which antimicrobial treatment was not indicated. They were asked to select their preferred treatment from multiple choices. In the scenarios labelled 'A', the laboratory report did not report antibiotic susceptibilities, but included comments from the microbiologist. In the scenarios labelled 'B', the laboratory report included full organism identification and susceptibility results without additional comments.

Results

For scenarios 1, 2 and 3 there was a significantly higher probability ( P  <   0.01) that the doctor selected an answer involving antibiotic treatment if he/she received the 'B' version of the scenario where reports included antimicrobial susceptibilities, but no interpretive comments. This was significant in both interns and more senior doctors. In scenario 4, of which there were two versions, there was no difference seen in the answers between the groups given scenario A or B.

Conclusions

The results of this survey suggest that withholding antimicrobial susceptibility results in combination with interpretive comments on microbiology reports significantly influences the decision of junior doctors to prescribe antibiotics in low-acuity outpatient setting scenarios (represented in scenarios 1-3), but not in inpatient scenarios (represented in scenario 4).

A matrix metalloproteinase proenzyme activator produced by articular cartilage

Matrix metalloproteinases (MMPs) are involved in connective tissue turnover under physiological and pathological conditions. MMP activity is regulated by the requirement for zymogen activation. This report describes a proMMP-3 activator produced by articular cartilage. The activator initiates a step-wise processing of proMMP-3 to generate an array of active species. Sequencing of activation intermediates demonstrated cleavage on the NH2-terminal side of certain basic residues in the MMP-3 propeptide. Metal ion chelators inhibited activator-dependent proteolysis, and activity was restored by low levels of ZnCl2. These catalytic properties suggest similarity to members of the insulinase superfamily of metalloendopeptidases with in vitro specificity for single arginine or paired basic processing sites in a variety of prohormones. Dibasic sites also exist in the propeptides of several MMPs including proMMP-3. This is the first report that cartilage produces a potent MMP proenzyme activator, opening the possibility of a novel intrinsic activation pathway for catabolic processes in this avascular tissue.