Repurposing antibiotic resistance surveillance data to support treatment of recurrent infections in a remote setting

In northern Australia, a region with limited access to healthcare and a substantial population living remotely, antibiotic resistance adds to the complexity of treating infections. Focussing on Escherichia coli urinary tract infections (UTIs) and Staphylococcus aureus skin & soft tissue infections (SSTIs) captured by a northern Australian antibiotic resistance surveillance system, we used logistic regression to investigate predictors of a subsequent resistant isolate during the same infection episode. We also investigated predictors of recurrent infection. Our analysis included 98,651 E. coli isolates and 121,755 S. aureus isolates from 70,851 patients between January 2007 and June 2020. Following an initially susceptible E. coli UTI, subsequent recovery of a cefazolin (8%) or ampicillin (13%) -resistant isolate during the same infection episode was more common than a ceftriaxone-resistant isolate (2%). For an initially susceptible S. aureus SSTI, subsequent recovery of a methicillin-resistant isolate (8%) was more common than a trimethoprim-sulfamethoxazole-resistant isolate (2%). For UTIs and SSTIs, prior infection with a resistant pathogen was a strong predictor of both recurrent infection and resistance in future infection episodes. This multi-centre study demonstrates an association between antibiotic resistance and an increased likelihood of recurrent infection. Particularly in remote areas, a patient's past antibiograms should guide current treatment choices since recurrent infection will most likely be at least as resistant as previous infection episodes. Using population-level surveillance data in this way can also help clinicians decide if they should switch antibiotics for patients with ongoing symptoms, while waiting for diagnostic results.

Can non‐typeable Haemophilus influenzae carriage surveillance data infer antimicrobial resistance associated with otitis media?

Importance

In remote communities of the Northern Territory, Australia, children experience high rates of otitis media (OM), commonly caused by non-typeable Haemophilus influenzae (NTHi). Few data exist on antibiotic susceptibility of NTHi from OM.

Objective

To determine whether population-level nasopharyngeal NTHi antibiotic susceptibility data could inform antibiotic treatment for OM.

Methods

NTHi isolates (n = 92) collected from ear discharge between 2003 and 2013 were selected to time- and age-match NTHi isolates from the nasopharyngeal carriage (n = 95). Antimicrobial susceptibility were tested. Phylogenomic trees and a genome-wide association study (GWAS) were performed to determine the similarity of nasopharyngeal and ear isolates at a population level.

Results

Among 174 NTHi isolates available for antimicrobial susceptibility testing, 10.3% (18/174) were resistant to ampicillin and 9.2% (16/174) were resistant to trimethoprim-sulfamethoxazole. Small numbers of isolates (≤3) were resistant to tetracycline, chloramphenicol, or amoxicillin-clavulanic acid. There was no statistical difference in the proportion of ampicillin-resistant (P = 0.11) or trimethoprim-sulfamethoxazole-resistant isolates (P = 0.70) between ear discharge and nasopharynx-derived NTHi isolates. Three multi-drug resistant NTHi isolates were identified. Phylogenomic trees showed no clustering of 187 Haemophilus influenzae isolates based on anatomical niche (nasopharynx or ear discharge), and no genetic variations that distinguished NTHi derived from ear discharge and nasopharyngeal carriage were evident in the GWAS.

Interpretation

In this population-level study, nasopharyngeal and ear discharge isolates did not represent distinct microbial populations. These results support tracking of population-level nasopharyngeal NTHi antibiotic resistance patterns to inform clinical management of OM in this population.

Disease burden, associated mortality and economic impact of antimicrobial resistant infections in Australia

BACKGROUND

The growing spread of antimicrobial resistance (AMR) is accepted as a threat to humans, animals and the environment. This threat is considered to be both country specific and global, with bacteria resistant to antibiotic treatment geographically dispersed. Despite this, we have very few Australian estimates available that use national surveillance data supplemented with measures of risk, to generate reliable and actionable measures of AMR impact. These data are essential to direct policies and programs and support equitable healthcare resource utilisation. Importantly, such data can lead to implementation of programs to improved morbidity and mortality of patients with a resistant infection.

METHODS

Using data from a previous case-cohort study, we estimated the AMR-associated health and economic impact caused by five hospital-associated AMR pathogens (Enterococcus spp., E. coli, K. pneumoniae, P. aeruginosa and S. aureus) in patients with a bloodstream, urinary tract, or respiratory tract infection in Australia in 2020. We estimated disease burden based on the counterfactual scenario in which all AMR infections were replaced by no infection.We used a population-level simulation model to compute AMR-associated mortality, loss of quality-adjusted life years and costs.

FINDINGS

In 2020, there were 1,031 AMR-associated deaths (95% uncertainty interval [UI] 294, 2,615) from the five resistant hospital-associated infections in Australia. The greatest odds of dying were from respiratory infections (ceftazidime-resistant P. aeruginosa) and bloodstream infections, both resulting in high hospital and premature death costs. MRSA bacteraemia contributed the most to hospital costs (measured as bed-days) as patients with this infection resulted in additional 12,818 (95% UI 7246, 19966) hospital bed-days and cost the hospitals an extra $24,366,741 (95%UI $13,774,548, $37,954,686) per year. However, the cost of premature death from five resistant pathogens was $438,543,052, which was by far greater than the total hospital cost ($71,988,858). We estimate a loss of 27,705 quality-adjusted life years due to the five AMR pathogens.

INTERPRETATION

These are the first Australian estimates of AMR-associated health and economic impact. Country-level estimates of AMR impact are needed to provide local evidence to better inform programs and health policies to reduce morbidity and mortality associated with infection. The burden in hospital is likely an underestimate of the impact of AMR due to community-associated infections where data are limited, and the AMR burden is high. This should now be the focus of future study in this area.

FUNDING

TMW was supported by the Australian Partnership for Preparedness Research on Infectious Disease Emergencies (APPRISE) (grant number GNT1116530) Fellowship.

The antimicrobial resistance travel tool, an interactive evidence-based educational tool to limit antimicrobial resistance spread

BACKGROUND

International travel has been recognized as a risk factor contributing to the spread of antimicrobial resistance (AMR). However, tools focused on AMR in the context of international travel and designed to guide decision-making are limited. We aimed at developing an evidence-based educational tool targeting both healthcare professionals (HCPs) and international travellers to help prevent the spread of AMR.

METHODS

A literature review on 12 antimicrobial-resistant bacteria (ARB) listed as critical and high tiers in the WHO Pathogen Priority List covering four key areas was carried out: AMR surveillance data; epidemiological studies reporting ARB prevalence data on carriage in returning travellers; guidance documents reporting indications on screening for ARB in returning travellers and recommendations for ARB prevention for the public. The evidence, catalogued at country-level, provided the content for a series of visualizations that allow assessment of the risk of AMR acquisition through travel.

RESULTS

Up to January 2021, the database includes data on: (i) AMR surveillance for 2.018.241 isolates from 86 countries; (ii) ARB prevalence of carriage from 11.679 international travellers and (iii) 15 guidance documents published by major public health agencies. The evidence allowed the development of a consultation scheme for the evaluation of risk factors, prevalence of carriage, proportion and recommendations for screening of AMR. For the public, pre-travel practical measures to minimize the risk of transmission were framed.

CONCLUSIONS

This easy-to-use, annually updated, freely accessible AMR travel tool (https://epi-net.eu/travel-tool/overview/), is the first of its kind to be developed. For HCPs, it can provide a valuable resource for teaching and a repository that facilitates a stepwise assessment of the risk of AMR spread and strengthen implementation of optimized infection control measures. Similarly, for travellers, the tool has the potential to raise awareness of AMR and outlines preventive measures that reduce the risk of AMR acquisition and spread.

Contribution of socio-economic factors in the spread of antimicrobial resistant infections in Australian primary healthcare clinics

OBJECTIVES

To effectively contain antimicrobial resistant (AMR) infections, we must better understand the social determinates of health that contribute to transmission and spread of infections.

METHODS

We used clinical data from patients attending primary healthcare clinics across three jurisdictions of Australia (2007-2019). Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) isolates and their corresponding antibiotic susceptibilities were included. Using multivariable logistic regression analysis, we assessed associations between AMR prevalence and indices of social disadvantage as reported by the Australian Bureau of Statistics (i.e. remoteness, socio-economic disadvantage and average person per household).

RESULTS

This study reports 12 years of longitudinal data from 43,448 isolates from a high-burden low resource setting in Australia. Access to health and social services (as measured by remoteness index) was a risk factor for increased prevalence of third-generation cephalosporin-resistant (3GC) E. coli (odds ratio 5.05; 95% confidence interval 3.19, 8.04) and methicillin-resistant S. aureus (MRSA) (odds ratio 5.72; 95% confidence interval 5.02, 6.54). We did not find a positive correlation of AMR and socio-economic disadvantage or average person per household indices.

CONCLUSIONS

Remoteness is a risk factor for increased prevalence of 3GC-resistant E.coli and MRSA. We demonstrate that traditional disease surveillance systems can be repurposed to capture the broader social drivers of AMR. Access to pathogen-specific and social data early and within the local regional context will fill a significant gap in disease prevention and the global spread of AMR.

The increased length of hospital stay and mortality associated with community-associated infections in Australia

Background

An increasing proportion of antibiotic-resistant infections are community acquired. However, the burden of community-associated infections (CAIs) and the resulting impact due to resistance have not been well described.

Methods

We conducted a multisite, retrospective case–cohort study of all acute care hospital admissions across 134 hospitals in Australia. Patients admitted with a positive culture of 1 of 5 organisms of interest, namely Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecium, from January 1, 2012, through December 30, 2016, were included. Data linkage was used to link hospital admissions and pathology data. Patients with a bloodstream infection (BSI), urinary tract infection (UTI), or respiratory tract infection (RTI) were included in the analysis. We compared patients with a resistant and drug-sensitive infection and used regression analyses to derive the difference in length of hospital stay (LOS) and mortality estimates associated with resistance.

Results

No statistically significant impact on hospital LOS for patients with resistant CAIs compared with drug-sensitive CAIs was identified. CAI patients with drug-resistant Enterobacteriaceae (E. coli, K. pneumoniae) BSIs were more likely to die in the hospital than those with drug-sensitive Enterobacteriaceae BSIs (odds ratio [OR], 3.28; 95% CI, 1.40–6.92). CAI patients with drug-resistant P. aeruginosa UTIs were more likely to die in the hospital than those with the drug-sensitive counterpart (OR, 2.43; 95% CI, 1.12–4.85).

Conclusions

The burden of CAI in the hospital is significant, and antibiotic resistance is adding to associated mortality.

Antimicrobial Resistance Surveillance to Support Decision-Making in a High-Prevalence Region: An Evaluation

Despite a high use of antibiotics and a significant burden of infectious disease, ongoing monitoring and reporting of antimicrobial resistant pathogens in rural and regional Australia is insufficient. Many geographically isolated regions of Australia have limited infrastructure, resources and fall outside of surveillance reach, limiting health services’ ability to provide an early warning signal and appropriate response. To monitor trends in the development of antimicrobial resistance (AMR), identify high-risk populations and to evaluate effectiveness of control and prevention in rural and regional Australia, a subnational surveillance system termed HOTspots was developed. To promote the best use of public health resources through the development of effective and efficient surveillance systems, we evaluated HOTspots and its prototype surveillance platform for data quality, acceptability, representativeness, and timeliness. We used the Centers for Disease Prevention and Control (CDC) guidelines for evaluating public health surveillance systems and assessed the four attributes using a descriptive analysis of quantitative data and a thematic analysis of qualitative data. We report that the HOTspots surveillance system and its prototype platform effectively captures and represents AMR data across Northern Australia. The descriptive analysis of HOTspots data demonstrated some variation in data completeness but that data validity and representativeness were high. Thematic analysis of interview transcripts found that the system was acceptable, with almost all study participants identifying timeliness, online accessibility, and community representativeness as drivers for adoption of the system, and that the system provided timely data. The evaluation also identified areas for improvement and made recommendations to the HOTspots surveillance system and its associated prototype platform.

Antibiotic resistance in uropathogens across northern Australia 2007-20 and impact on treatment guidelines

BACKGROUND

Urinary tract infections are common and are increasingly resistant to antibiotic therapy. Northern Australia is a sparsely populated region with limited access to healthcare, a relatively high burden of disease, a substantial regional and remote population, and high rates of antibiotic resistance in skin pathogens.

OBJECTIVES

To explore trends in antibiotic resistance for common uropathogens Escherichia coli and Klebsiella pneumoniae in northern Australia, and how these relate to current treatment guidelines in the community and hospital settings.

METHODS

We used data from an antibiotic resistance surveillance system. We calculated the monthly and yearly percentage of isolates that were resistant in each antibiotic class, by bacterium. We analysed resistance proportions geographically and temporally, stratifying by healthcare setting. Using simple linear regression, we investigated longitudinal trends in monthly resistance proportions and correlation between community and hospital isolates.

RESULTS

Our analysis included 177 223 urinary isolates from four pathology providers between 2007 and 2020. Resistance to most studied antibiotics remained <20% (for E. coli and K. pneumoniae, respectively, in 2019: amoxicillin/clavulanate 16%, 5%; cefazolin 17%, 8%; nitrofurantoin 1%, 31%; trimethoprim 36%, 17%; gentamicin 7%, 2%; extended-spectrum cephalosporins 8%, 5%), but many are increasing by 1%-3% (absolute) per year. Patterns of resistance were similar between isolates from community and hospital patients.

CONCLUSIONS

Antibiotic resistance in uropathogens is increasing in northern Australia, but treatment guidelines generally remain appropriate for empirical therapy of patients with suspected infection (except trimethoprim in some settings). Our findings demonstrate the importance of local surveillance data (HOTspots) to inform clinical decision making and guidelines.

Attributable Length of Stay, Mortality Risk, and Costs of Bacterial Health Care-Associated Infections in Australia: A Retrospective Case-cohort Study

Background

Unbiased estimates of the health and economic impacts of health care–associated infections (HAIs) are scarce and focus largely on patients with bloodstream infections (BSIs). We sought to estimate the hospital length of stay (LOS), mortality rate, and costs of HAIs and the differential effects on patients with an antimicrobial-resistant infection.

Methods

We conducted a multisite, retrospective case-cohort of all acute-care hospital admissions with a positive culture of 1 of the 5 organisms of interest (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, or Enterococcus faecium) from 1 January 2012 through 30 December 2016. Data linkage was used to generate a data set of statewide hospital admissions and pathology data. Patients with bloodstream, urinary, or respiratory tract infections were included in the analysis and matched to a sample of uninfected patients. We used multistate survival models to generate LOS, and logistic regression to derive mortality estimates.

Results

We matched 20 390 cases to 75 635 uninfected control patients. The overall incidence of infections due to the 5 studied organisms was 116.9 cases per 100 000 patient days, with E. coli urinary tract infections (UTIs) contributing the largest proportion (51 cases per 100 000 patient days). The impact of a UTI on LOS was moderate across the 5 studied pathogens. Resistance significantly increased LOS for patients with third-generation cephalosporin-resistant K. pneumoniae BSIs (extra 4.6 days) and methicillin-resistant S. aureus BSIs (extra 2.9 days). Consequently, the health-care costs of these infections were higher, compared to corresponding drug-sensitive strains.

Conclusions

The health burden remains highest for BSIs; however, UTIs and respiratory tract infections contributed most to the health-care system expenditure.

Championing women working in health across regional and rural Australia - a new dual-mentorship model

BACKGROUND

Mentoring is a critical component of career development and job satisfaction leading to a healthier workforce and more productive outputs. However, there are limited data on mentorship models in regional areas and in particular for women aspiring to leadership positions. Mentorship programs that leverage off experienced mentors from diverse disciplines have the potential to foster the transfer of knowledge and to positively influence job satisfaction and build capacity within the context of workforce shortage.

METHODS

This study describes a dual-mentorship model of professional development for women working in health in regional and rural Australia. We present the framework and describe the evaluation findings from a 12-month pilot program.

RESULTS

Both academic and corporate mentors provided diverse perspectives to the mentees during the 12-month period. On average, corporate mentors met with mentees more often, and focused these discussions on strategy and leadership skills whilst academic mentors provided more technical advice regarding academic growth. Mentees reported an improvement in workplace interconnectedness and confidence at the completion of the program.

CONCLUSION

We developed a framework for establishing a professional mentorship program that matches women working in regional health with mentors from diverse sectors including business, government, philanthropy and health, to provide a holistic approach to improving career satisfaction, institutional productivity and supporting a diverse workforce in regional or resource-poor settings.

Geospatial epidemiology of Staphylococcus aureus in a tropical setting: an enabling digital surveillance platform

Delivery of information to clinicians on evolving antimicrobial susceptibility needs to be accurate for the local needs, up-to-date and readily available at point of care. In northern Australia, bacterial infection rates are high but resistance to first- and second-line antibiotics is poorly described and currently-available datasets exclude primary healthcare data. We aimed to develop an online geospatial and interactive platform for aggregating, analysing and disseminating data on regional bacterial pathogen susceptibility. We report the epidemiology of Staphylococcus aureus as an example of the power of digital platforms to tackle the growing spread of antimicrobial resistance in a high-burden, geographically-sparse region and beyond. We developed an online geospatial platform called HOTspots that visualises antimicrobial susceptibility patterns and temporal trends. Data on clinically-important bacteria and their antibiotic susceptibility profiles were sought from retrospectively identified clinical specimens submitted to three participating pathology providers (96 unique tertiary and primary healthcare centres, n = 1,006,238 tests) between January 2008 and December 2017. Here we present data on S. aureus only. Data were available on specimen type, date and location of collection. Regions from the Australian Bureau of Statistics were used to provide spatial localisation. The online platform provides an engaging visual representation of spatial heterogeneity, demonstrating striking geographical variation in S. aureus susceptibility across northern Australia. Methicillin resistance rates vary from 46% in the west to 26% in the east. Plots generated by the platform show temporal trends in proportions of S. aureus resistant to methicillin and other antimicrobials across the three jurisdictions of northern Australia. A quarter of all, and up to 35% of methicillin-resistant S. aureus (MRSA) blood isolates in parts of the northern Australia were resistant to inducible-clindamycin. Clindamycin resistance rates in MRSA are worryingly high in regions of northern Australia and are a local impediment to empirical use of this agent for community MRSA. Visualising routinely collected laboratory data with digital platforms, allows clinicians, public health physicians and guideline developers to monitor and respond to antimicrobial resistance in a timely manner. Deployment of this platform into clinical practice supports national and global efforts to innovate traditional disease surveillance systems with the use of digital technology and to provide practical solutions to reducing the threat of antimicrobial resistance.

Using the best available data to estimate the cost of antimicrobial resistance: a systematic review

Background

Valuation of the economic cost of antimicrobial resistance (AMR) is important for decision making and should be estimated accurately. Highly variable or erroneous estimates may alarm policy makers and hospital administrators to act, but they also create confusion as to what the most reliable estimates are and how these should be assessed. This study aimed to assess the quality of methods used in studies that quantify the costs of AMR and to determine the best available evidence of the incremental cost of these infections.

Methods

In this systematic review, we searched PubMed, Embase, Cinahl, Cochrane databases and grey literature sources published between January 2012 and October 2016. Articles reporting the additional burden of Enterococcus spp., Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) resistant versus susceptible infections were sourced. The included studies were broadly classified as reporting oncosts from the healthcare/hospital/hospital charges perspective or societal perspective. Risk of bias was assessed based on three methodological components: (1) adjustment for length of stay prior to infection onset and consideration of time-dependent bias, (2) adjustment for comorbidities or severity of disease, and (3) adjustment for inappropriate antibiotic therapy.

Results

Of 1094 identified studies, we identified 12 peer-reviewed articles and two reports that quantified the economic burden of clinically important resistant infections. Two studies used multi-state modelling to account for the timing of infection minimising the risk of time dependent bias and these were considered to generate the best available cost estimates. Studies report an additional CHF 9473 per extended-spectrum beta-lactamases -resistant Enterobacteriaceae bloodstream infections (BSI); additional €3200 per third-generation cephalosporin resistant Enterobacteriaceae BSI; and additional €1600 per methicillin-resistant S. aureus (MRSA) BSI. The remaining studies either partially adjusted or did not consider the timing of infection in their analysis.

Conclusions

Implementation of AMR policy and decision-making should be guided only by reliable, unbiased estimates of effect size. Generating these estimates requires a thorough understanding of important biases and their impact on measured outcomes. This will ensure that researchers, clinicians, and other key decision makers concerned with increasing public health threat of AMR are accurately guided by the best available evidence.

Electronic supplementary material

The online version of this article (10.1186/s13756-019-0472-z) contains supplementary material, which is available to authorized users.

Letter to the editor in response to estimating the burden of antimicrobial resistance: a systematic literature review

The systematic review published by Naylor et al. in April 2018 highlights methodological assumptions and biases that occur in studies investigating the burden of antimicrobial resistance (AMR). They note that, due to both the large diversity of statistical approaches and perspectives chosen, the current evidence base of the burden of AMR is highly variable. Certainly, these conclusions are valid and the authors present a very thorough analysis of the currently published literature with a broad array of drug-bug combinations. But readers are left with limited direction of estimating the current best available estimate of the health and economic burden of AMR. Such estimates are desperately needed to inform clinical management and for priority setting activities and initiative to curbing the global threat of AMR.

Clinical management of drug-resistant bacteria in Australian hospitals: An online survey of doctors' opinions

BACKGROUND

To gain a better understanding of clinical practice for the treatment of common drug-resistant infections.

METHODS

A web-based anonymous survey was developed to gain a better understanding of clinical practice of patients infected with drug-resistant bloodstream infections (BSI). The survey instrument was a questionnaire requesting doctors to provide their opinion on the most likely choice of an antibiotic, dose and route of administration for patients infected with a drug-resistant Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa or Enterococcus faecium.

RESULTS

All of the survey participants (n = 28) were hospital-based doctors. Choice of therapy for drug-resistant E. coli and K. pneumoniae was uniform across survey participants. However, optimal treatment of ceftazidime-resistant P. aeruginosa and VRE was less clear.

CONCLUSION

The survey adds to the limited body of evidence in this clinical area and can be a useful tool for health economists in determining the additional cost of treating patients with drug-resistant infections.

How much do superbugs cost Australian hospitals? An evidence-based open-access tool

Drug resistant "superbugs" are on the rise and pose a considerable threat. Little is known of their impact on health outcomes and costs to health services at a country-level. Local and relevant estimates that are realistic and derived with a transparent method can stimulate and inform policy responses. We describe an innovative online open-access tool, ResImpact that provides estimates of the national cost of common drug-resistant infections in Australia. Users are able to modify the proportion of five resistant organisms and be presented with an estimate of the associated healthcare costs. By translating complex economic data into a practical and user-friendly output, policy makers and other health professionals can improve their policy response for the Australian healthcare system.

Epidemiology of sexually transmissible infections in New South Wales: are case notifications enough?

BACKGROUND

Surveillance of sexually transmissible infections (STI)s is important to assess the disease burden in the population and to monitor and evaluate changes in trends over time. Routinely collected surveillance data in New South Wales are reliant on case reporting, which for many infections is an inadequate mechanism for capturing incidence and prevalence. Increasing rates of chlamydia over the past decade have sparked intense debate as to whether the current notification system is optimal and whether the true burden of infection are being measured. This study describes the current surveillance for STIs in New South Wales.

METHODS

New South Wales-specific data for the years 2000-2009 were analysed. Notification data were used to examine the rate of the 4 STIs that are notifiable in New South Wales; chlamydia, gonorrhoea, infectious syphilis and HIV notifications. Hospital admissions and chlamydia-associated pelvic inflammatory disease were analysed using admitted patient data.

RESULTS

Chlamydia was the most frequently reported of the notifiable STIs in New South Wales. Despite the higher rates of notification compared with other STIs, chlamydia-related hospitalisations contribute less than a 5th of all STI-related hospital admissions. Infectious syphilis contributed to the highest proportion of all STI-related hospitalisations in New South Wales and rates increased from 2000 to 2009. For other STIs such as anogenital herpes and gonorrhoea, hospital admissions remained stable for the same period.

CONCLUSIONS

Notifications data for STIs should be complemented with hospital admission and other data sources to better describe STI morbidity. A synthesis of these data sources is needed to improve current surveillance and allow for better comparisons and trend analysis of STIs in New South Wales.

Immunological diversity within a family of cutinase-like proteins of Mycobacterium tuberculosis

Secreted proteins of Mycobacterium tuberculosis play key roles in the assembly of the mycobacterial cell wall, with many being major targets of the host immune response. To date, meaningful characterization of a significant proportion of this important group of proteins is lacking. Among the group of putatively secreted proteins of M. tuberculosis are 7 cutinase-like proteins (CLP), not previously characterized in terms of their immunogenicity or vaccine protective efficacy. Although the CLP vary in the degree of homology with one another, they all share a similar active catalytic triad, closely homologous to that of the cutinase of Fusarium solani. By construction of DNA vaccines of all 7 CLP, and expression and purification of soluble, recombinant CLP, this study addresses the immunological responses to these proteins. Clp1, 2, 3 and 6 were found to elicit significant IFN-gamma secretion in DNA immunized mice, with the antigens also demonstrating specificity in terms of CLP-generated T cell IFN-gamma release, with minimal cross reactivity of humoral responses. Finally, following delivery of DNA vaccines, Clp1, 2 and 6, conferred a moderate yet reproducible and significant level of protection in a murine aerosol model of M. tuberculosis infection.

Interleukin-23 restores immunity to Mycobacterium tuberculosis infection in IL-12p40-deficient mice and is not required for the development of IL-17-secreting T cell responses

Host control of Mycobacterium tuberculosis is dependent on the activation of CD4+ T cells secreting IFN-gamma and their recruitment to the site of infection. The development of more efficient vaccines against tuberculosis requires detailed understanding of the induction and maintenance of T cell immunity. Cytokines important for the development of cell-mediated immunity include IL-12 and IL-23, which share the p40 subunit and the IL-12Rbeta1 signaling chain. To explore the differential effect of IL-12 and IL-23 during M. tuberculosis infection, we used plasmids expressing IL-23 (p2AIL-23) or IL-12 (p2AIL-12) alone in dendritic cells or macrophages from IL-12p40(-/-) mice. In the absence of the IL-12/IL-23 axis, immunization with a DNA vaccine expressing the M. tuberculosis Ag85B induced a limited Ag-specific T cell response and no control of M. tuberculosis infection. Co-delivery of p2AIL-23 or p2AIL-12 with DNA85B induced strong proliferative and IFN-gamma-secreting T cell responses equivalent to those observed in wild-type mice immunized with DNA85B. This response resulted in partial protection against aerosol M. tuberculosis; however, the protective effect was less than in wild-type mice owing to the requirement for IL-12 or IL-23 for the optimal expansion of IFN-gamma-secreting T cells. Interestingly, bacillus Calmette-Guérin immune T cells generated in the absence of IL-12 or IL-23 were deficient in IFN-gamma production, but exhibited a robust IL-17 secretion associated with a degree of protection against pulmonary infection. Therefore, exogenous IL-23 can complement IL-12 deficiency for the initial expansion of Ag-specific T cells and is not essential for the development of potentially protective IL-17-secreting T cells.

Plasmid interleukin-23 (IL-23), but not plasmid IL-27, enhances the protective efficacy of a DNA vaccine against Mycobacterium tuberculosis infection

Protection against intracellular pathogens such as Mycobacterium tuberculosis requires the development of Th1-like T-cell responses. This in turn is dependent on the pattern of cytokine produced from dendritic cells (DCs) after infection. Three heterodimeric cytokines, interleukin-12 (IL-12), IL-23, and IL-27, as well as IL-18, contribute to the differentiation and expansion of naive CD4(+) T cells. In this study we compared the effects of plasmids expressing both chains of IL-12, IL-23, or IL-27 as adjuvants for DNA immunization against M. tuberculosis infection. The genes encoding p19 and p40 chains of IL-23 or EBI3 and p28 chains of IL-27 were cloned on either side of a self-cleaving peptide from the FMDV2A protein. The secretion of functional cytokines from transfected cells was detected with bioassays. Supernatant from p2AIL-23-transfected cells induced the release of IL-17 from activated lymphocytes, confirming the presence of bioactive IL-23. Further, supernatant from p2AIL-27-transfected cells stimulated a significant increase in the proliferation of peptide-stimulated transgenic CD4(+) T cells. In initial experiments, M. tuberculosis infection of DCs was more potent at inducing IL-12 and IL-23 secretion than infection with the vaccine strain Mycobacterium bovis bacille Calmette-Guérin (BCG), and no significant upregulation of IL-27 was observed. Coimmunization of C57BL/6 mice with DNA expressing M. tuberculosis antigen 85B (Ag85B; DNA85B) and plasmids expressing IL-23 or IL-12 stimulated stronger Ag85B-specific T-cell proliferative and IFN-gamma responses than DNA85B alone, whereas the addition of p2AIL-27 had no effect. Interestingly, DNA85B codelivered with p2AIL-12, but not p2AIL-23, reduced the immunoglobulin G antibody response. Both p2AIL-23 and p2AIL-12, but not p2AIL-27, enhanced the protective efficacy of DNA85B against aerosol M. tuberculosis challenge. Therefore, both p2AIL-23 and p2AIL-12 are valuable as cytokine adjuvants for increasing the protective antituberculosis immunity induced by DNA vaccines.