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      Equivalent Performance of the Cobas ® Cdiff Test for Use on the Cobas ® Liat ® System and the Cobas ® 4800 System


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          Clostridium difficile infection is a significant health burden, and innovative solutions are needed to shorten time to diagnosis and improve infection control. We evaluated the performance of the cobas ® Cdiff test for use on the cobas ® Liat ® System (cobas ® Liat ® Cdiff), a single-sample, on-demand, and automated molecular solution with a 20-min turnaround time. The limit of detection was 45–90 colony-forming units (CFUs)/swab for toxigenic strains that covered the most prevalent toxinotypes, including the hyper-virulent epidemic 027/BI/NAP1 strain. Using 442 prospectively collected clinical stool specimens, we compared the performance of the cobas® Liat® Cdiff to direct culture and to the cobas® Cdiff test on the cobas® 4800 System (cobas® 4800 Cdiff) – a medium-throughput molecular platform. The sensitivity and specificity of the cobas® Liat® Cdiff compared to direct culture were 93.1% and 95.1%, respectively, and this performance did not statistically differ from the cobas® 4800 Cdiff (P < 0.05). Direct correlation of the cobas® Liat® and cobas® 4800 Cdiff tests yielded overall percent agreement of 98.6%. The test performance, automation, and turnaround time of the cobas® Liat® Cdiff enable its use for on-demand and out-of-hours testing as a complement to existing batch testing solutions like the cobas® 4800 Cdiff.

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          Diverse sources of C. difficile infection identified on whole-genome sequencing.

          It has been thought that Clostridium difficile infection is transmitted predominantly within health care settings. However, endemic spread has hampered identification of precise sources of infection and the assessment of the efficacy of interventions. From September 2007 through March 2011, we performed whole-genome sequencing on isolates obtained from all symptomatic patients with C. difficile infection identified in health care settings or in the community in Oxfordshire, United Kingdom. We compared single-nucleotide variants (SNVs) between the isolates, using C. difficile evolution rates estimated on the basis of the first and last samples obtained from each of 145 patients, with 0 to 2 SNVs expected between transmitted isolates obtained less than 124 days apart, on the basis of a 95% prediction interval. We then identified plausible epidemiologic links among genetically related cases from data on hospital admissions and community location. Of 1250 C. difficile cases that were evaluated, 1223 (98%) were successfully sequenced. In a comparison of 957 samples obtained from April 2008 through March 2011 with those obtained from September 2007 onward, a total of 333 isolates (35%) had no more than 2 SNVs from at least 1 earlier case, and 428 isolates (45%) had more than 10 SNVs from all previous cases. Reductions in incidence over time were similar in the two groups, a finding that suggests an effect of interventions targeting the transition from exposure to disease. Of the 333 patients with no more than 2 SNVs (consistent with transmission), 126 patients (38%) had close hospital contact with another patient, and 120 patients (36%) had no hospital or community contact with another patient. Distinct subtypes of infection continued to be identified throughout the study, which suggests a considerable reservoir of C. difficile. Over a 3-year period, 45% of C. difficile cases in Oxfordshire were genetically distinct from all previous cases. Genetically diverse sources, in addition to symptomatic patients, play a major part in C. difficile transmission. (Funded by the U.K. Clinical Research Collaboration Translational Infection Research Initiative and others.).
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            Clostridium difficile infection: epidemiology, diagnosis and understanding transmission.

            Clostridium difficile infection (CDI) continues to affect patients in hospitals and communities worldwide. The spectrum of clinical disease ranges from mild diarrhoea to toxic megacolon, colonic perforation and death. However, this bacterium might also be carried asymptomatically in the gut, potentially leading to 'silent' onward transmission. Modern technologies, such as whole-genome sequencing and multi-locus variable-number tandem-repeat analysis, are helping to track C. difficile transmission across health-care facilities, countries and continents, offering the potential to illuminate previously under-recognized sources of infection. These typing strategies have also demonstrated heterogeneity in terms of CDI incidence and strain types reflecting different stages of epidemic spread. However, comparison of CDI epidemiology, particularly between countries, is challenging due to wide-ranging approaches to sampling and testing. Diagnostic strategies for C. difficile are complicated both by the wide range of bacterial targets and tests available and the need to differentiate between toxin-producing and non-toxigenic strains. Multistep diagnostic algorithms have been recommended to improve sensitivity and specificity. In this Review, we describe the latest advances in the understanding of C. difficile epidemiology, transmission and diagnosis, and discuss the effect of these developments on the clinical management of CDI.
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              Clostridium difficile infection caused by the epidemic BI/NAP1/027 strain.

              Rates and severity of Clostridium difficile infection (CDI) in hospitals in North America and Europe have increased since 2000 and correlate with dissemination of an epidemic strain characterized by higher than usual toxin A and B production, the presence of a third toxin, binary toxin, and high-level resistance to fluoroquinolone antibiotics. The strain, which is restriction endonuclease analysis group BI, pulse-field gel electrophoresis type NAP1, and polymerase chain reaction ribotype 027, is designated BI/NAP1/027. How this strain has become so widely distributed geographically and produces such severe CDI is the subject of active investigation. The deletion at position 117 of the tcdC gene, a repressor of toxin A and B production, is one possible contributor to increased levels of the toxins. The role of binary toxin is unknown. Recent isolates of BI/NAP1/027 were found to be resistant to fluoroquinolones, which is likely to contribute to the dissemination of this strain. Other virulence factors such as increased sporulation and surface layer protein adherence are also under investigation. Infections caused by this organism are particularly frequent among elderly hospitalized patients, in whom the attributable 30-day mortality is greater than 5%. Major risk factors for BI/NAP1/027 infection include advanced age, hospitalization, and exposure to specific antimicrobials, especially fluoroquinolones and cephalosporins. When CDI is severe, vancomycin treatment is more effective than metronidazole; for mild disease either agent can be used. Control of hospital outbreaks caused by BI/NAP1/027 is difficult but possible through a combination of barrier precautions, environmental cleaning, and antimicrobial stewardship.

                Author and article information

                Eur J Microbiol Immunol (Bp)
                Eur J Microbiol Immunol (Bp)
                European Journal of Microbiology & Immunology
                Akadémiai Kiadó (Budapest )
                05 December 2017
                18 December 2017
                : 7
                : 4
                : 310-318
                [1 ] Medical and Scientific Affairs, Roche Molecular Diagnostics , Pleasanton, CA, USA
                [2 ] Development, Roche Molecular Diagnostics , Pleasanton, CA, USA
                [3 ] NorthShore University HealthSystem , Evanston, IL, USA
                Author notes
                * Roche Molecular Diagnostics, 4300 Hacienda Drive, Pleasanton, CA 94588, USA; +1(925) 251–6863; +1(925) 730–8988; sachin.garg@ 123456roche.com
                © 2017, The Author(s)

                This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License ( https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and reproduction in any medium for non-commercial purposes, provided the original author and source are credited, a link to the CC License is provided, and changes – if any – are indicated.

                : 16 October 2017
                : 11 November 2017
                Page count
                Figures: 0, Tables: 3, Equations: 0, References: 42, Pages: 9
                Original Article

                clostridium difficile,pcr,poc,cdi,near-patient,molecular,naat
                clostridium difficile, pcr, poc, cdi, near-patient, molecular, naat


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