Recent transmission among immigrants and transmission permeability between the immigrant and autochthonous populations were found. Epidemiologic strategies that combine universal genotyping and refined surveys of the clustered patients are needed to investigate transmission patterns in complex scenarios.
BackgroundNosocomial outbreaks of multidrug-resistant Acinetobacter baumannii are of worldwide concern. Using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and multiple locus variable number tandem repeat sequence (VNTR) analysis (MLVA), the present work examines the genetic diversity of the endemic and epidemic A. baumannii clones isolated in a single hospital over a twelve-year period.ResultsPFGE analysis of 405 A. baumannii-calcoaceticus complex isolates detected 15 A. baumannii endemic/epidemic PFGE types (EE1 to EE15) that grouped into five clusters: EE1-EE8, EE9, EE10, EE11 and EE12-EE15. The MLST sequence type (ST) distributions were: international clone II (ST-2) 60%, international clone III (ST-3) 26.7%, ST-15 6.7%, and ST-80 6.7%. MLVA-8Orsay returned 17 allelic profiles. The large (L) VNTR marker profiles were fully concordant with the detected STs, and concordant with 14 up to 15 PFGE types. Imipenem resistance was detected in five PFGE types; the prevalence of the blaOXA-58-like and blaOXA-40-like genes was 60% and 40% respectively.ConclusionsPFGE proved to be a vital tool for analysis of the temporal and spatial distribution of the clones. MLST and the VNTR L-markers grouped the isolates into clonal clusters. The wide diversity of MLVA small (S)-markers, however, did not permit clustering. The present results demonstrate the persistence of several endemic PFGE types in the hospital, the involvement of some of them in outbreaks, and the inter hospital transmission of extensively drug-resistant ST-15 and ST-80.
Laboratory cross-contamination by Mycobacterium tuberculosis is known to be responsible for the misdiagnosis of tuberculosis, but its impact on other contexts has not been analyzed. We present the findings of a molecular epidemiology analysis in which the recent transmission events identified by a genotyping reference center were overestimated as a result of unnoticed laboratory cross-contamination in the original diagnostic laboratories.The phenomenon of misdiagnosing tuberculosis by laboratory cross-contamination when Mycobacterium tuberculosis is cultured has been widely reported (3, 4-8, 10, 11). The production of aerosolized particles after the processing of smearpositive specimens, cultures positive for M. tuberculosis, or positive control strains may be responsible for the inoculation of other specimens processed on the same day or of reagents used for the decontamination of specimens (5). False positivity is suspected (i) if M. tuberculosis is cultured from a sample processed together with a smear-positive specimen, (ii) if M. tuberculosis is cultured from only one of the cultures in the set (usually with a low yield of bacteria), and (iii) if the clinician is considering an alternative diagnosis, that is, a diagnosis other than tuberculosis (TB). Suspicion of false positivity is increased when two or more of these conditions are met. Finally, if molecular analysis is available, cross-contamination is confirmed when the strains cultured from both truly infected and contaminated specimens share the same genotypic pattern and no epidemiological links can be found between the cases. Several studies, some of which are based on molecular analysis, have estimated that the rate of laboratory cross-contamination for M. tuberculosis ranges from 0.1% to 3%, although massive contamination has caused up to 65% of false-positive cases (11).False-positive results for tuberculosis have been a matter of concern because of the clinical, therapeutic, and social impacts of the misdiagnosis of tuberculosis. The economic load associated with each misdiagnosed case of tuberculosis has been estimated to be $32,618 (9). However, another area on which false positivity has an impact but which has received little attention is the misidentification of recent transmission events by molecular epidemiology studies. Molecular epidemiology is based on the analysis of the genotypes of cultured M. tuberculosis isolates to identify cases infected by the same M. tuberculosis strain. These cases are defined as clustered and are considered to be caused by recent transmission events and to belong to the same transmission chain. If an analysis to determine the existence of potential false-positive cases is not performed before molecular analysis, as a quality control of microbiological procedures, there is a risk of misassigning clustered cases. This refined preanalysis is not usually performed because molecular epidemiology studies are generally run by laboratories which are different from those which culture M. tuberculosis from clinical spec...
Drug resistance mutations in HIV-2 are selected at the same positions as in HIV-1, although with different frequency. Polymorphisms in the RT and PR associated with drug resistance in HIV-1 as compensatory changes are common in untreated HIV-2 subjects. These findings highlight the need for specific guidelines for interpreting genotypic resistance patterns in HIV-2 infection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.