Werngren J.,Swedish Institute for Communicable Disease Control SMI |
Sturegard E.,Lund University |
Jureen P.,Swedish Institute for Communicable Disease Control SMI |
Angeby K.,Karolinska University Hospital |
And 2 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2012
Pyrazinamide (PZA) is a potent first-line agent for the treatment of tuberculosis (TB) with activity also against a significant part of drug-resistant Mycobacterium tuberculosis strains. Since PZA is active only at acid pH, testing for susceptibility to PZA is difficult and insufficiently reproducible. The recommended critical concentration for PZA susceptibility (MIC, 100 mg/liter) used in the Bactec systems (460 and MGIT 960) has not been critically evaluated against wild-type MIC distributions in clinical isolates of Mycobacterium tuberculosis. Using the Bactec MGIT 960 system, we determined the PZA MICs for 46 clinical M. tuberculosis isolates and compared the results to pncA sequencing and previously obtained Bactec 460 data. For consecutive clinical isolates (n = 15), the epidemiological wild-type cutoff (ECOFF) for PZA was 64 mg/liter (MIC distribution range, ≤8 to 64mg/liter), and no pncA gene mutations were detected. In strains resistant in both Bactec systems (n=18), the PZA MICs ranged from 256 to ≥ 1,024 mg/liter. The discordances between pncA sequencing, susceptibility results in Bactec 460, and MIC determinations in Bactec MGIT 960 were mainly observed in strains with MICs close to or at the ECOFF. We conclude that in general, wild-type and resistant strains were clearly separated and correlated to pncA mutations, although some isolates with MICs close to the ECOFF cause reproducibility problems within and between methods. To solve this issue, we suggest that isolates with MICs of ≤64 mg/liter be classified susceptible, that an intermediary category be introduced at 128 mg/liter, and that strains with MICs of >128 mg/liter be classified resistant. Copyright © 2012, American Society for Microbiology. All Rights Reserved.
Schon T.,Kalmar County Hospital |
Schon T.,Linköping University |
Jureen P.,Swedish Institute for Communicable Disease Control SMI |
Chryssanthou E.,Karolinska University Hospital |
And 5 more authors.
Journal of Antimicrobial Chemotherapy | Year: 2013
Objectives: It has long been assumed that some rifampicin-resistant Mycobacterium tuberculosis strains are susceptible to, and thus treatable with, rifabutin. However, clinical breakpoints for susceptibility testing of rifabutin as well as the evidence for a clinical effect of rifabutin in rifampicin-resistant strains remains poorly defined. The objective of this study was to re-evaluate the breakpoint for rifabutin in relation to its MIC wild-type distribution and the presence of mutations in rpoB. Methods: The MIC in 7H10 Middlebrook medium was determined for clinical isolates of M. tuberculosis (n1/495), where a majority were multidrug resistant. Additionally, all strains were screened for rpoB mutations by sequencing and the GenoType MTBDRplus assay. Results: Rifampicin resistance was confirmed by genotypical and/or phenotypical tests in 73 isolates (76.8%). Nineteen isolates, defined as rifampicin resistant and rifabutin susceptible according to the present breakpoint, exhibited significantly higher MICs of rifabutin (0.064-0.5 mg/L) than rifabutin-susceptible isolates without any detectable mutations in rpoB (P <0.001). These 19 isolates were clearly resistant to rifampicin (MIC 2-256 mg/L) and all but one had mutations in rpoB, with 9 (47.4%) specifically in Asp516Val. Conclusions:Our results indicate that rifampicin-resistant but rifabutin-susceptible isolates according to the present breakpoints harbour rpoB mutations and have a rifabutin MIC significantly higher than strains without any detectable mutations in rpoB. So far there are no clinical, pharmacological or microbiological data to confirm that such isolates can be treated with rifabutin and we suggest a revision of the current breakpoints. © The Author 2013. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.
Vanni I.,Instituto Superiore Of Sanita |
Caccio S.M.,Instituto Superiore Of Sanita |
van Lith L.,University Utrecht |
Lebbad M.,Swedish Institute for Communicable Disease Control SMI |
And 3 more authors.
PLoS Neglected Tropical Diseases | Year: 2012
The flagellated protozoan Giardia duodenalis is a common gastrointestinal parasite of mammals, including humans. Molecular characterizations have shown the existence of eight genetic groups (or assemblages) in the G. duodenalis species complex. Human infections are caused by assemblages A and B, which infect other mammals as well. Whether transmission routes, animal reservoirs and associations with specific symptoms differ for assemblage A and assemblage B is not clear. Furthermore, the occurrence and clinical significance of mixed (A+B) infections is also poorly understood. To date, the majority of PCR assays has been developed to identify all G. duodenalis assemblages based on the use of primers that bind to conserved regions, yet a reliable identification of specific assemblages is better achieved by ad hoc methods. The aim of this work was to design simple PCR assays that, based on the use of assemblage-specific primers, produce diagnostic bands of different lengths for assemblage A and B. We first generated novel sequence information from assemblage B, identified homologous sequences in the assemblage A genome, and designed primers at six independent loci. Experiments performed on DNA extracted from axenic cultures showed that two of the six assays can detect the equivalent of a single cyst and are not negatively influenced by disproportions between DNA of each assemblage, at least up to a 9:1 ratio. Further experiments on DNAs extracted from feces showed that the two assays can detect both assemblages in single tube reactions with excellent reliability. Finally, the robustness of these assays was demonstrated by testing a large collection of human isolates previously typed by multi-locus genotyping. © 2012 Vanni et al.
Zeimes C.B.,Catholic University of Louvain |
Olsson G.E.,Swedish University of Agricultural Sciences |
Hjertqvist M.,Swedish Institute for Communicable Disease Control SMI |
Vanwambeke S.O.,Catholic University of Louvain
Parasites and Vectors | Year: 2014
Background: In this paper, the hazard and exposure concepts from risk assessment are applied in an innovative approach to understand zoonotic disease risk. Hazard is here related to the landscape ecology determining where the hosts, vectors and pathogens are and, exposure is defined as the attractiveness and accessibility to hazardous areas. Tick-borne encephalitis in Sweden was used as a case study. Methods. Three boosted regression tree models are compared: a hazard model, an exposure model and a global model which combines the two approaches. Results: The global model offers the best predictive power and the most accurate modelling. The highest probabilities were found in easy-to-reach places with high landscape diversity, holiday houses, waterbodies and, well-connected forests of oak, birch or pine, with open-area in their ecotones, a complex shape, numerous clear-cuts and, a variation in tree height. Conclusion: While conditions for access and use of hazardous areas are quite specific to Scandinavia, this study offers promising perspectives to improve our understanding of the distribution of zoonotic and vector-borne diseases in diverse contexts. © 2014 Zeimes et al.; licensee BioMed Central Ltd.
Hallander H.O.,Swedish Institute for Communicable Disease Control SMI |
Nilsson L.,Swedish Institute for Communicable Disease Control SMI |
Nilsson L.,University Hospital |
Gustafsson L.,Swedish Institute for Communicable Disease Control SMI
Expert Review of Clinical Pharmacology | Year: 2011
Pertussis is still poorly controlled in both adolescents and adults. As a result, an adolescent pertussis booster vaccine dose has already been implemented or decided on in many countries. The reasons for this have been twofold: a worrying increase of infections in the target group of adolescents and a wish to prevent serious pertussis disease among young yet unvaccinated, and partly vaccinated, infants. Currently, it is still too early to evaluate the effect of the late booster on the circulation of Bordetella pertussis owing to the lack of relevant follow-up data. A universal adolescent booster vaccination will reduce the incidence of pertussis in the target group but the duration of immunity is uncertain. It is an open question as to what extent boosters should be offered to older age groups or if natural infections would be preferable. On the one hand, circulating B. pertussis may be hazardous to the youngest unvaccinated infants. On the other hand, subclinical natural boosters might be beneficial to population immunity. As the duration of immunity is shorter after vaccination than after natural infections, an unwanted consequence of adolescent boosters might shift the infection peak to older child-bearing adults. It is therefore recommended that recurrent serosurveys are used to follow the influence of vaccination on the antigenic pressure, as well as the duration of protective immunity. For this purpose, standardization of symptoms and laboratory criteria used for notification, as well as the methodology for seroepidemiology, must be established. Adverse reactions after adolescent vaccination and outbreaks owing to new B. pertussis variants must also be carefully monitored. In this article, we have used Swedish surveillance data and the results from Swedish seroepidemiology to illustrate these problem areas. © 2011 Expert Reviews Ltd.
Darenberg J.,Swedish Institute for Communicable Disease Control SMI
Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin | Year: 2013
The incidence of invasive group A streptococcal infections in Sweden was 6.1 per 100,000 population in 2012, the highest since the disease became notifiable in 2004. Furthermore, January and February 2013 marked a dramatic increase of cases notified, partly explainable by an increase of emm1/T1 isolates, a type previously shown to cause severe invasive disease more often than other types. Healthcare providers in Sweden and health authorities in neighbouring countries have been informed about this increase.
Rizzardi K.,Swedish Institute for Communicable Disease Control SMI |
Wahab T.,Swedish Institute for Communicable Disease Control SMI |
Jernberg C.,Swedish Institute for Communicable Disease Control SMI
Journal of Clinical Microbiology | Year: 2013
In this study, an alternative to the current traditional bioserotyping techniques was developed for subtyping Y. enterocolitica using matrix-Assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The most common pathogenic bioserotypes could easily be distinguished using only a few bioserotype-specific biomarkers. However, biochemical methods should still be used to distinguish biotype 1A from 1B. Copyright © 2013, American Society for Microbiology. All Rights Reserved.
Linder E.,Karolinska Institutet |
Grote A.,University of Helsinki |
Varjo S.,University of Oulu |
Linder N.,University of Helsinki |
And 6 more authors.
PLoS Neglected Tropical Diseases | Year: 2013
Background:Microscopy, being relatively easy to perform at low cost, is the universal diagnostic method for detection of most globally important parasitic infections. As quality control is hard to maintain, misdiagnosis is common, which affects both estimates of parasite burdens and patient care. Novel techniques for high-resolution imaging and image transfer over data networks may offer solutions to these problems through provision of education, quality assurance and diagnostics. Imaging can be done directly on image sensor chips, a technique possible to exploit commercially for the development of inexpensive "mini-microscopes". Images can be transferred for analysis both visually and by computer vision both at point-of-care and at remote locations.Methods/Principal Findings:Here we describe imaging of helminth eggs using mini-microscopes constructed from webcams and mobile phone cameras. The results show that an inexpensive webcam, stripped off its optics to allow direct application of the test sample on the exposed surface of the sensor, yields images of Schistosoma haematobium eggs, which can be identified visually. Using a highly specific image pattern recognition algorithm, 4 out of 5 eggs observed visually could be identified.Conclusions/Significance:As proof of concept we show that an inexpensive imaging device, such as a webcam, may be easily modified into a microscope, for the detection of helminth eggs based on on-chip imaging. Furthermore, algorithms for helminth egg detection by machine vision can be generated for automated diagnostics. The results can be exploited for constructing simple imaging devices for low-cost diagnostics of urogenital schistosomiasis and other neglected tropical infectious diseases. © 2013 Linder et al.
Riera-Montes M.,Swedish Institute for Communicable Disease Control SMI |
Riera-Montes M.,U.S. Center for Disease Control and Prevention |
Velicko I.,Swedish Institute for Communicable Disease Control SMI
Eurosurveillance | Year: 2011
This study evaluates the ability of the Chlamydia surveillance system to provide relevant information to inform prevention and control activities in Sweden. The system was evaluated, according to the Guidelines for Evaluating Public Health Surveillance Systems from the United States Centers for Disease Prevention and Control, using surveillance data from 1997 to 2008. We interviewed staff from the Swedish Institute for Communicable Disease Control, the National Board of Health and Welfare and one county medical officer (CMO). We conducted a survey among laboratories, CMOs and a sample of clinics. Satisfaction with the system was good for 86% of CMOs, all laboratories, and 99% of clinics. The interviewed stakeholders considered the system to deliver relevant and accurate information that is useful for health policy decision making. However, the objectives for Chlamydia surveillance should be clearly defined in order to adapt the system requirements, simplify data collection and improve timeliness. © 2008 All rights reserved.
Borjesson S.,National Veterinary Institute SVA |
Jernberg C.,Swedish Institute for Communicable Disease Control SMI |
Brolund A.,Swedish Institute for Communicable Disease Control SMI |
Edquist P.,Swedish Institute for Communicable Disease Control SMI |
And 6 more authors.
Clinical Microbiology and Infection | Year: 2013
A selection of plasmid-mediated AmpC-producing Escherichia coli isolates carrying blaCMY-2 from Swedish broilers were characterized to establish their relatedness to and a possible overlap with human clinical E. coli isolates. The results showed diversity among the E. coli isolated from broilers, indicating that the spread in the population was not due to one strain. However, only one type of plasmid belonging to replicon type incK was identified. Furthermore, there were no indications of spread of blaCMY-2 E. coli isolates from broilers to human clinical settings, although Swedish broilers may be a source of blaCMY-2 and/or the plasmid carrying blaCMY-2. ©2013 European Society of Clinical Microbiology and Infectious Diseases.