Dr Olga Tosas-Auguet

Research Area: Global Health
Technology Exchange: Medical statistics
Scientific Themes: Tropical Medicine & Global Health and Immunology & Infectious Disease
Web Links:

I am working on a Phase 1 Global Challenges Explorations award that seeks to develop and evaluate a new approach to large scale surveillance of bacterial antibiotic resistance in low income settings, which can then be taken forward to a testing stage initially in partnership with an emerging network of policy makers and healthcare practitioners in Africa (Project title: Metrics for Public Health – Perspective Surveillance of Bacterial Antibiotic Resistance). The work involves a combination of population-level metagenomics studies, led by Dr Nicole Stoesser at the Modernising Medical Microbiology Consortium, and mathematical analyses of data in collaboration with Professor Ben Cooper (Mahidol Oxford Tropical Medicine Research Unit), and a team of co-investigators based in UK and at Oxford Tropical Network Programmes in South East Asia (Cambodia-Oxford Medical Research Unit) and Africa (Kenya Medical Research Institute (KEMRI)| Wellcome Collaborative Research Programme).

I am also working on an ESRC pump-priming award with Professor Mike English and co-investigators at Kenya, UK and WHO Geneva Headquarters (Project title: Infection Prevention and Control and Antibiotic Stewardship to Avert Antibiotic Resistance in High Risk Populations from Resource Poor Settings). The study aims to provide a platform for the systematic formulation and testing of context-appropriate behaviour change/integrated interventions to improve infection prevention and control and antibiotic stewardship (IPC-ABS) in high-risk populations in Kenya hospitals, based on critical analysis of national policy, organisational and practice environments and group- and individual-level behaviours. We anticipate that proposed interventions to improve patient safety and limit the emergence and spread of bacterial antibiotic resistance though IPC-ABS, will be generalizable to other settings in East Africa.

I am collaborating in two studies that are tracking and mapping the distribution of antibiotic resistant bacteria and resistance genes in relation to sociodemographic traits in South East London communities. These studies are led by the Centre for Clinical Infection and Diagnostics Research - King’s College London & Guy’s and St Thomas’ NHS Foundation Trust.

Name Department Institution Country
Professor Mike English Tropical Medicine Oxford University, Nairobi Kenya
Dr Nicole Stoesser Experimental Medicine Division Oxford University, John Radcliffe Hospital United Kingdom
Professor Ben Cooper Tropical Medicine Oxford University, Bangkok Thailand
Professor Paul Turner Tropical Medicine Oxford University, Siem Reap Cambodia
Professor James A Berkley Tropical Medicine Oxford University, Kilifi Kenya
Professor Charles Vincent Experimental Psychology University of Oxford United Kingdom
Dr Eleanor Murray Saïd Business School University of Oxford United Kingdom
Professor Jonathan Edgeworth Centre for Clinical Infection and Diagnostics Research King's College London United Kingdom
Dr Margaret Montgomery Water, Sanitation, Hygiene and Health World Health Organisation Switzerland
Dr Jacob McKnight Tropical Medicine Oxford University, Nairobi Kenya
Dr Isabella Maina Health sector Monitoring and Evaluation Unit Ministry of Health Kenya Kenya
Professor Taane Clark Pathogen Molecular Biology London School of Hygiene and Tropical Medicine United Kingdom
Dr David Gathara Kenya Medical Research Institute Kenya
Dr Michuki Maina Kenya Medical Research Institute Kenya
Tosas Auguet O, Stabler RA, Betley J, Preston MD, Dhaliwal M, Gaunt M, Ioannou A, Desai N, Karadag T, Batra R et al. 2018. Frequent Undetected Ward-Based Methicillin-Resistant Staphylococcus aureus Transmission Linked to Patient Sharing Between Hospitals. Clin Infect Dis, 66 (6), pp. 840-848. | Show Abstract | Read more

Background: Recent evidence suggests that hospital transmission of methicillin-resistant Staphylococcus aureus (MRSA) is uncommon in UK centers that have implemented sustained infection control programs. We investigated whether a healthcare-network analysis could shed light on transmission paths currently sustaining MRSA levels in UK hospitals. Methods: A cross-sectional observational study was performed in 2 National Health Service hospital groups and a general district hospital in Southeast London. All MRSA patients identified at inpatient, outpatient, and community settings between 1 November 2011 and 29 February 2012 were included. We identified genetically defined MRSA transmission clusters in individual hospitals and across the healthcare network, and examined genetic differentiation of sequence type (ST) 22 MRSA isolates within and between hospitals and inpatient or outpatient and community settings, as informed by average and median pairwise single-nucleotide polymorphisms (SNPs) and SNP-based proportions of nearly identical isolates. Results: Two hundred forty-eight of 610 (40.7%) MRSA patients were linked in 90 transmission clusters, of which 27 spanned multiple hospitals. Analysis of a large 32 patient ST22-MRSA cluster showed that 26 of 32 patients (81.3%) had multiple contacts with one another during ward stays at any hospital. No residential, outpatient, or significant community healthcare contacts were identified. Genetic differentiation between ST22 MRSA inpatient isolates from different hospitals was less than between inpatient isolates from the same hospitals (P ≤ .01). Conclusions: There is evidence of frequent ward-based transmission of MRSA brought about by frequent patient admissions to multiple hospitals. Limiting in-ward transmission requires sharing of MRSA status data between hospitals.

Wu PJ, Jeyaratnam D, Tosas O, Cooper BS, French GL. 2017. Point-of-care universal screening for meticillin-resistant Staphylococcus aureus: a cluster-randomized cross-over trial. J Hosp Infect, 95 (3), pp. 245-252. | Show Abstract | Read more

BACKGROUND: Meticillin-resistant Staphylococcus aureus (MRSA) is frequently endemic in healthcare settings and may be transmitted by person-to-person spread. Asymptomatic MRSA carriers are potential, unsuspected sources for transmission and some of them may be identified by admission screening. AIM: To assess whether rapid point-of-care screening (POCS) for MRSA at hospital admission may be associated with a reduction in MRSA acquisition rates when compared with slower laboratory-based methods. METHODS: A cluster-randomized cross-over trial was conducted in four admission wards of an acute London tertiary care hospital. Polymerase chain reaction-based POCS screening was compared with conventional culture screening. Patients were screened on ward admission and discharge, and the MRSA acquisition rate on the admission wards was calculated as the primary outcome measure. RESULTS: In all, 10,017 patients were included; 4978 in the control arm, 5039 in the POCS arm. The MRSA carriage rate on admission was 1.7%. POCS reduced the median reporting time from 40.4 to 3.7 h (P < 0.001). MRSA was acquired on the admission wards by 23 (0.46%) patients in the control arm and by 24 (0.48%) in the intervention arm, acquisition rates of 5.39 and 4.60 per 1000 days respectively. After taking account of predefined confounding factors, the adjusted incidence rate ratio (IRR) for change in trend for MRSA acquisition was 0.961 (95% confidence interval: 0.766-1.206). The adjusted IRR for step change for MRSA acquisition was 0.98 (0.304-3.162). CONCLUSION: POCS produces a significantly faster result but has no effect on MRSA acquisition on admission wards compared with culture screening. Where compliance with infection prevention and control is high and MRSA carriage is low, POCS has no additional impact on MRSA acquisition rates over the first one to four days of admission compared with conventional culture screening.

Dyakova E, Bisnauthsing KN, Querol-Rubiera A, Patel A, Ahanonu C, Tosas Auguet O, Edgeworth JD, Goldenberg SD, Otter JA. 2017. Efficacy and acceptability of rectal and perineal sampling for identifying gastrointestinal colonization with extended spectrum β-lactamase Enterobacteriaceae. Clin Microbiol Infect, 23 (8), pp. 577.e1-577.e3. | Show Abstract | Read more

OBJECTIVES: We evaluated 'pre-laboratory' factors associated with the detection of extended spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) colonization including anatomical site, and staff and patient factors. METHODS: All admissions to a large London hospital over 3 months were approached to provide rectal and perineal swabs, which were cultured for ESBL-E using chromogenic media. ESBL-E detection rates for patient- or staff-collected rectal or perineal swabs were compared using McNemar tests. Binary logistic regression was used to explore factors associated with patients declining to provide a rectal swab. The impact of simplifying the verbal study description to patients to improve the participation rate was evaluated. RESULTS: Carriage of ESBL-E was significantly higher in rectal swabs than perineal swabs (7.8% of 4006 versus 3.8% of 4006, p <0.001), whether collected by staff or patients; 31.9% of 869 patients did not provide a rectal swab before the change in study description compared with 7.6% of 3690 patients afterwards (p <0.001). In multivariable analysis, factors associated with patients declining to provide a rectal swab were younger age (OR 0.99, 95% CI 0.99-1.00), female gender (OR 1.26, 95% CI 1.04-1.52), transfers from other hospitals (OR 1.77, 95% CI 1.07-2.93) or an unknown admission route (OR 1.61, 95% CI 1.09-2.37), being admitted before the change in study description (OR 0.39, 95% CI 0.31-0.48), and the staff member who consented the patient (p <0.001); ethnicity was not a significant factor. CONCLUSIONS: Rectal swabs are recommended for the detection of ESBL-E colonization. Staff and patient factors influence whether patients participate in prevalence studies, which may skew their findings.

Otter JA, Dyakova E, Bisnauthsing KN, Querol-Rubiera A, Patel A, Ahanonu C, Tosas Auguet O, Edgeworth JD, Goldenberg SD. 2016. Universal hospital admission screening for carbapenemase-producing organisms in a low-prevalence setting. J Antimicrob Chemother, 71 (12), pp. 3556-3561. | Show Abstract | Read more

BACKGROUND: Carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat for healthcare providers worldwide. OBJECTIVES: To determine CPE carriage rates and risk factors in an unselected hospital cohort at the time of admission. METHODS: We approached 4567 patients within 72 h of admission to provide a rectal swab and answer a questionnaire on risk factors for carriage. Rectal swabs were cultured for carbapenem-resistant organisms on chromogenic and non-chromogenic agar, and tested for carbapenemase production by PCR (Check-Direct CPE). The study was approved by the NHS Research Ethics Committee. RESULTS: Only 6 CPE were cultured from 5 (0.1%) of 4006 patients who provided a rectal swab; only 1 was cultured using non-chromogenic media. An additional 76 culture-negative rectal swabs were initially PCR positive, but none grew a carbapenem-resistant organism despite enrichment culture and only two were positive when retested several months later by Check-Direct and a second PCR assay (Cepheid GeneXpert®Carba-R). A modified Ct cut-off of <35 would have resolved these apparent false-positives. 40% of patients had a risk factor that should prompt screening and pre-emptive isolation as defined by UK CPE guidelines but only 8.1% and 20.2% of these patients had been screened and pre-emptively isolated by clinical teams, respectively. Overseas hospitalization was the only significant risk factor for CPE carriage (P < 0.001, OR 64.3, 95% CI 7.3-488.5). CONCLUSIONS: This study highlights a very low carriage rate of CPE. Hospitalization abroad is the most important risk factor to guide admission screening in this low-prevalence setting.

Stewardson AJ, Allignol A, Beyersmann J, Graves N, Schumacher M, Meyer R, Tacconelli E, De Angelis G, Farina C, Pezzoli F et al. 2016. The health and economic burden of bloodstream infections caused by antimicrobial-susceptible and non-susceptible Enterobacteriaceae and Staphylococcus aureus in European hospitals, 2010 and 2011: a multicentre retrospective cohort study Eurosurveillance, 21 (33), | Read more

Hughes J, Goldenberg SD, Tosas O, Edgeworth JD, Otter JA. 2016. Recent emergence of carbapenem-resistant organisms in a low prevalence UK setting in London Journal of Infection Prevention, 17 (3), pp. 130-134. | Read more

Last M, Tosas O, Gallo Cassarino T, Kozlakidis Z, Edgeworth J. 2016. Evolving classification of intensive care patients from event data Artificial Intelligence in Medicine, 69 pp. 22-32. | Read more

Aia P, Kal M, Lavu E, John LN, Johnson K, Coulter C, Ershova J, Tosas O, Zignol M, Ahmadova S, Islam T. 2016. The Burden of Drug-Resistant Tuberculosis in Papua New Guinea: Results of a Large Population-Based Survey PLOS ONE, 11 (3), pp. e0149806-e0149806. | Read more

Deeny SR, Worby CJ, Tosas Auguet O, Cooper BS, Edgeworth J, Cookson B, Robotham JV. 2016. More Research Is Needed to Quantify Risks, Benefits, and Cost-Effectiveness of Universal Mupirocin Usage. Clin Infect Dis, 62 (9), pp. 1193-1194. | Read more

Tosas Auguet O, Betley JR, Stabler RA, Patel A, Ioannou A, Marbach H, Hearn P, Aryee A, Goldenberg SD, Otter JA et al. 2016. Evidence for Community Transmission of Community-Associated but Not Health-Care-Associated Methicillin-Resistant Staphylococcus Aureus Strains Linked to Social and Material Deprivation: Spatial Analysis of Cross-sectional Data. PLoS Med, 13 (1), pp. e1001944. | Show Abstract | Read more

BACKGROUND: Identifying and tackling the social determinants of infectious diseases has become a public health priority following the recognition that individuals with lower socioeconomic status are disproportionately affected by infectious diseases. In many parts of the world, epidemiologically and genotypically defined community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged to become frequent causes of hospital infection. The aim of this study was to use spatial models with adjustment for area-level hospital attendance to determine the transmission niche of genotypically defined CA- and health-care-associated (HA)-MRSA strains across a diverse region of South East London and to explore a potential link between MRSA carriage and markers of social and material deprivation. METHODS AND FINDINGS: This study involved spatial analysis of cross-sectional data linked with all MRSA isolates identified by three National Health Service (NHS) microbiology laboratories between 1 November 2011 and 29 February 2012. The cohort of hospital-based NHS microbiology diagnostic services serves 867,254 usual residents in the Lambeth, Southwark, and Lewisham boroughs in South East London, United Kingdom (UK). Isolates were classified as HA- or CA-MRSA based on whole genome sequencing. All MRSA cases identified over 4 mo within the three-borough catchment area (n = 471) were mapped to small geographies and linked to area-level aggregated socioeconomic and demographic data. Disease mapping and ecological regression models were used to infer the most likely transmission niches for each MRSA genetic classification and to describe the spatial epidemiology of MRSA in relation to social determinants. Specifically, we aimed to identify demographic and socioeconomic population traits that explain cross-area extra variation in HA- and CA-MRSA relative risks following adjustment for hospital attendance data. We explored the potential for associations with the English Indices of Deprivation 2010 (including the Index of Multiple Deprivation and several deprivation domains and subdomains) and the 2011 England and Wales census demographic and socioeconomic indicators (including numbers of households by deprivation dimension) and indicators of population health. Both CA-and HA-MRSA were associated with household deprivation (CA-MRSA relative risk [RR]: 1.72 [1.03-2.94]; HA-MRSA RR: 1.57 [1.06-2.33]), which was correlated with hospital attendance (Pearson correlation coefficient [PCC] = 0.76). HA-MRSA was also associated with poor health (RR: 1.10 [1.01-1.19]) and residence in communal care homes (RR: 1.24 [1.12-1.37]), whereas CA-MRSA was linked with household overcrowding (RR: 1.58 [1.04-2.41]) and wider barriers, which represent a combined score for household overcrowding, low income, and homelessness (RR: 1.76 [1.16-2.70]). CA-MRSA was also associated with recent immigration to the UK (RR: 1.77 [1.19-2.66]). For the area-level variation in RR for CA-MRSA, 28.67% was attributable to the spatial arrangement of target geographies, compared with only 0.09% for HA-MRSA. An advantage to our study is that it provided a representative sample of usual residents receiving care in the catchment areas. A limitation is that relationships apparent in aggregated data analyses cannot be assumed to operate at the individual level. CONCLUSIONS: There was no evidence of community transmission of HA-MRSA strains, implying that HA-MRSA cases identified in the community originate from the hospital reservoir and are maintained by frequent attendance at health care facilities. In contrast, there was a high risk of CA-MRSA in deprived areas linked with overcrowding, homelessness, low income, and recent immigration to the UK, which was not explainable by health care exposure. Furthermore, areas adjacent to these deprived areas were themselves at greater risk of CA-MRSA, indicating community transmission of CA-MRSA. This ongoing community transmission could lead to CA-MRSA becoming the dominant strain types carried by patients admitted to hospital, particularly if successful hospital-based MRSA infection control programmes are maintained. These results suggest that community infection control programmes targeting transmission of CA-MRSA will be required to control MRSA in both the community and hospital. These epidemiological changes will also have implications for effectiveness of risk-factor-based hospital admission MRSA screening programmes.

Hughes J, Stabler R, Gaunt M, Karadag T, Desai N, Betley J, Ioannou A, Aryee A, Hearn P, Marbach H et al. 2015. Clonal variation in high- and low-level phenotypic and genotypic mupirocin resistance of MRSA isolates in south-east London. J Antimicrob Chemother, 70 (12), pp. 3191-3199. | Show Abstract | Read more

OBJECTIVES: Both low-level mupirocin resistance (LMR) and high-level mupirocin resistance (HMR) have been identified. The aim of this study was to determine the epidemiology of LMR and HMR in MRSA isolates at five hospitals that have used mupirocin for targeted decolonization as part of successful institutional control programmes. METHODS: All MRSA identified in three microbiology laboratories serving five central and south-east London hospitals and surrounding communities between November 2011 and February 2012 were included. HMR and LMR were determined by disc diffusion testing. WGS was used to derive multilocus sequence types (MLSTs) and the presence of HMR and LMR resistance determinants. RESULTS: Prevalence of either HMR or LMR amongst first healthcare episode isolates from 795 identified patients was 9.69% (95% CI 7.72-11.96); LMR was 6.29% (95% CI 4.70-8.21) and HMR was 3.40% (95% CI 2.25-4.90). Mupirocin resistance was not significantly different in isolates identified from inpatients at each microbiology laboratory, but was more common in genotypically defined 'hospital' rather than 'community' isolates (OR 3.17, 95% CI 1.36-9.30, P = 0.002). LMR was associated with inpatient stay, previous history of MRSA and age ≥65 years; HMR was associated with age ≥65 years and residential postcode outside London. LMR and HMR varied by clone, with both being low in the dominant UK MRSA clone ST22 compared with ST8, ST36 and ST239/241 for LMR and with ST8 and ST36 for HMR. V588F mutation and mupA carriage had high specificity (>97%) and area under the curve (>83%) to discriminate phenotypic mupirocin resistance, but uncertainty around the sensitivity point estimate was large (95% CI 52.50%-94.44%). Mutations in or near the mupA gene were found in eight isolates that carried mupA but were not HMR. CONCLUSIONS: Mupirocin resistance was identified in <10% of patients and varied significantly by clone, implying that changes in clonal epidemiology may have an important role in determining the prevalence of resistance in conjunction with selection due to mupirocin use.

Deeny SR, Worby CJ, Tosas Auguet O, Cooper BS, Edgeworth J, Cookson B, Robotham JV. 2015. Impact of mupirocin resistance on the transmission and control of healthcare-associated MRSA. J Antimicrob Chemother, 70 (12), pp. 3366-3378. | Show Abstract | Read more

OBJECTIVES: The objectives of this study were to estimate the relative transmissibility of mupirocin-resistant (MupR) and mupirocin-susceptible (MupS) MRSA strains and evaluate the long-term impact of MupR on MRSA control policies. METHODS: Parameters describing MupR and MupS strains were estimated using Markov chain Monte Carlo methods applied to data from two London teaching hospitals. These estimates parameterized a model used to evaluate the long-term impact of MupR on three mupirocin usage policies: 'clinical cases', 'screen and treat' and 'universal'. Strategies were assessed in terms of colonized and infected patient days and scenario and sensitivity analyses were performed. RESULTS: The transmission probability of a MupS strain was 2.16 (95% CI 1.38-2.94) times that of a MupR strain in the absence of mupirocin usage. The total prevalence of MupR in colonized and infected MRSA patients after 5 years of simulation was 9.1% (95% CI 8.7%-9.6%) with the 'screen and treat' mupirocin policy, increasing to 21.3% (95% CI 20.9%-21.7%) with 'universal' mupirocin use. The prevalence of MupR increased in 50%-75% of simulations with 'universal' usage and >10% of simulations with 'screen and treat' usage in scenarios where MupS had a higher transmission probability than MupR. CONCLUSIONS: Our results provide evidence from a clinical setting of a fitness cost associated with MupR in MRSA strains. This provides a plausible explanation for the low levels of mupirocin resistance seen following 'screen and treat' mupirocin usage. From our simulations, even under conservative estimates of relative transmissibility, we see long-term increases in the prevalence of MupR given 'universal' use.

Woolhouse MEJ, Thumbi SM, Jennings A, Chase-Topping M, Callaby R, Kiara H, Oosthuizen MC, Mbole-Kariuki MN, Conradie I, Handel IG et al. 2015. Co-infections determine patterns of mortality in a population exposed to parasite infection Science Advances, 1 (2), pp. e1400026-e1400026. | Read more

Otter JA, Tosas-Auguet O, Herdman MT, Williams B, Tucker D, Edgeworth JD, French GL. 2014. Implications of targeted versus universal admission screening for meticillin-resistant Staphylococcus aureus carriage in a London hospital. J Hosp Infect, 87 (3), pp. 171-174. | Show Abstract | Read more

Universal admission screening for meticillin-resistant Staphylococcus aureus (MRSA) has been performed in England since 2010. We evaluated the predictive performance of a regression model derived from the first year of universal screening for detecting MRSA at hospital admission. If we had used our previous targeted screening policy, 75% fewer patients (21,699 per year) would have been screened. However, this would have identified only ~55% of all MRSA carriers, 65% of healthcare-associated MRSA strains, and 40% of community-associated strains. Failing to identify ~45% of patients (262 per year) carrying MRSA at hospital admission may have implications for MRSA control.

Lauinger IL, Bible JM, Halligan EP, Bangalore H, Tosas O, Aarons EJ, MacMahon E, Tong CYW. 2013. Patient characteristics and severity of human rhinovirus infections in children Journal of Clinical Virology, 58 (1), pp. 216-220. | Read more

Vlek ALM, Cooper BS, Kypraios T, Cox A, Edgeworth JD, Auguet OT. 2013. Clustering of antimicrobial resistance outbreaks across bacterial species in the intensive care unit. Clin Infect Dis, 57 (1), pp. 65-76. | Show Abstract | Read more

BACKGROUND: There are frequent reports of intensive care unit (ICU) outbreaks due to transmission of particular antibiotic-resistant bacteria. Less is known about the burden of outbreaks of resistance due to horizontal transfer of mobile genetic elements between species. Moreover, the potential of existing statistical software as a preliminary means for detecting such events has never been assessed. This study uses a software package to determine the burden of species and resistance outbreaks in 2 adjacent ICUs and to look for evidence of clustering of resistance outbreaks consistent with interspecies transmission of resistance elements. METHODS: A retrospective analysis of data from 2 adjacent 15-bed adult ICUs between 2002 and 2009 was undertaken. Detection of bacterial species-groups and resistance outbreaks was conducted using SaTScan and WHONet-SaTScan software. Resampling and permutation methods were applied to investigate temporal clustering of outbreaks. RESULTS: Outbreaks occurred for 69% of bacterial species-groups (18/26), and resistance outbreaks were detected against 63% of antibiotics (10/16). Resistance outbreaks against 7 of 10 antibiotics were observed in multiple species-groups simultaneously and there was evidence of inter-species-group dependence for 4 of 7 antibiotics; background temporal changes in resistance did not explain the temporal aggregation of outbreaks in 3 of 7 antibiotics. CONCLUSIONS: Species outbreaks occurred for the majority of bacteria commonly identified in the ICU. There was evidence for frequent temporal clustering of resistance outbreaks consistent with interspecies transmission of resistance elements. Wider application of outbreak detection software combined with targeted sequencing of bacterial genomes is needed to understand the contribution of interspecies gene transfer to resistance emergence.

Otter JA, Patel A, Cliff PR, Halligan EP, Tosas O, Edgeworth JD. 2013. Selection for qacA carriage in CC22, but not CC30, methicillin-resistant Staphylococcus aureus bloodstream infection isolates during a successful institutional infection control programme Journal of Antimicrobial Chemotherapy, 68 (5), pp. 992-999. | Read more

Otter JA, Herdman MT, Williams B, Tosas O, Edgeworth JD, French GL. 2013. Low prevalence of meticillin-resistant Staphylococcus aureus carriage at hospital admission: implications for risk-factor-based vs universal screening Journal of Hospital Infection, 83 (2), pp. 114-121. | Read more

Bronsvoort BMDC, Thumbi SM, Poole EJ, Kiara H, Tosas Auguet O, Handel IG, Jennings A, Conradie I, Mbole-Kariuki MN, Toye PG et al. 2013. Design and descriptive epidemiology of the Infectious Diseases of East African Livestock (IDEAL) project, a longitudinal calf cohort study in western Kenya BMC Veterinary Research, 9 (1), pp. 171-171. | Read more

Cooper BS, Kypraios T, Batra R, Wyncoll D, Tosas O, Edgeworth JD. 2012. Quantifying type-specific reproduction numbers for nosocomial pathogens: evidence for heightened transmission of an Asian sequence type 239 MRSA clone. PLoS Comput Biol, 8 (4), pp. e1002454. | Show Abstract | Read more

An important determinant of a pathogen's success is the rate at which it is transmitted from infected to susceptible hosts. Although there are anecdotal reports that methicillin-resistant Staphylococcus aureus (MRSA) clones vary in their transmissibility in hospital settings, attempts to quantify such variation are lacking for common subtypes, as are methods for addressing this question using routinely-collected MRSA screening data in endemic settings. Here we present a method to quantify the time-varying transmissibility of different subtypes of common bacterial nosocomial pathogens using routine surveillance data. The method adapts approaches for estimating reproduction numbers based on the probabilistic reconstruction of epidemic trees, but uses relative hazards rather than serial intervals to assign probabilities to different sources for observed transmission events. The method is applied to data collected as part of a retrospective observational study of a concurrent MRSA outbreak in the United Kingdom with dominant endemic MRSA clones (ST22 and ST36) and an Asian ST239 MRSA strain (ST239-TW) in two linked adult intensive care units, and compared with an approach based on a fully parametric transmission model. The results provide support for the hypothesis that the clones responded differently to an infection control measure based on the use of topical antiseptics, which was more effective at reducing transmission of endemic clones. They also suggest that in one of the two ICUs patients colonized or infected with the ST239-TW MRSA clone had consistently higher risks of transmitting MRSA to patients free of MRSA. These findings represent some of the first quantitative evidence of enhanced transmissibility of a pandemic MRSA lineage, and highlight the potential value of tailoring hospital infection control measures to specific pathogen subtypes.




Miller CE, Batra R, Cooper BS, Patel AK, Klein J, Otter JA, Kypraios T, French GL, Tosas O, Edgeworth JD. 2012. An association between bacterial genotype combined with a high-vancomycin minimum inhibitory concentration and risk of endocarditis in methicillin-resistant staphylococcus aureus bloodstream infection Clinical Infectious Diseases, 54 (5), pp. 591-600. | Show Abstract | Read more

Introduction. Antimicrobial resistance and bacterial virulence factors may increase the risk of hematogenous complications during methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI). This study reports on the impact of increasing vancomycin minimum inhibitory concentrations (V-MICs) and MRSA clone type on risk of hematogenous complications from MRSA BSI during implementation of an effective MRSA control program. Methods. In sum, spa typing, staphylococcal cassette chromosome mec allotyping, and vancomycin and teicoplanin MICs were performed on 821 consecutive MRSA bloodstream isolates from 1999 to 2009. Prospectively collected data, including focus of infection, were available for 695 clinically significant cases. Logistic and multinomial logistic regression was used to determine the association between clone type, vancomycin MIC (V-MIC), and focus of infection. Results. MRSA BSIs decreased by ∼90% during the 11 years. Typing placed isolates into 3 clonal complex (CC) groups that had different population median V-MICs (CC30, 0.5 μg/mL [n = 349]; CC22, 0.75 μg/mL [n = 272] ; non-CC22/30, 1.5 μg/mL [n = 199]). There was a progressive increase in the proportion of isolates with a V-MIC above baseline median in each clonal group and a disproportionate fall in the clone group with lowest median V-MIC (CC30). In contrast, there were no increases in teicoplanin MICs. High V-MIC CC22 isolates (1.5-2 μg/mL) were strongly associated with endocarditis (odds ratio, 12; 95% confidence interval, 3.72-38.9) and with a septic metastasis after catheter-related BSI (odds ratio, 106; 95% confidence interval, 12.6-883) compared with other clone type/V-MIC combinations.Conclusions.An interaction between clone type and V-MIC can influence the risk of endocarditis associated with MRSA BSI, implying involvement of both therapeutic and host-pathogen factors. © The Author 2012. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved.

Kotwinski D, Batra R, Olga T, Edgeworth J, Wyncoll D, Shankar-Hari M. 2011. Prevalence of Gram-negative bacilli resistance in adult critically ill patients at admission screening Critical Care, 15 (Suppl 1), pp. P225-P225. | Read more

Cox AP, Tosas O, Tilley A, Picozzi K, Coleman P, Hide G, Welburn SC. 2010. Constraints to estimating the prevalence of trypanosome infections in East African zebu cattle Parasites & Vectors, 3 (1), pp. 82-82. | Read more

Padrós F, Palenzuela O, Hispano C, Tosas O, Zarza C, Crespo S, Alvarez-Pellitero P. 2001. Myxidium leei (Myxozoa) infections in aquarium-reared Mediterranean fish species Diseases of Aquatic Organisms, 47 pp. 57-62. | Read more