MA BEHR, E KOKOSKIN, TW GYORKOS, L CÉDILOTTE, GM FAUBERT, JD MACLEAN. Laboratory diagnosis for
MAIN RESULTS:For 152 previously collected stools, copro-antigen detection had a sensitivity of 73 of 74 (98.6%) and a specificity of 78 of 78 (100%). In clinical samples of 62 patients, eight of the 62 patients (13%) were diagnosed with G lamblia infection on microscopy. Copro-antigen diagnosis was accurate in symptomatic patients, with sensitivity of seven of eight (87.5%) and specificity of 52 of 54 (96.8%). Serology was less accurate. IgG response to G lamblia had sensitivity of four of seven and specificity of 24 of 50 (48%), and IgM response had sensitivity of three of six and specificity 27 of 48 (56%). Western blot had a sensitivity of five of seven and a specificity of 38 of 49 (78%). CONCLUSIONS: Copro-antigen diagnosis of G lamblia is highly accurate in patients with chronic gastrointestinal complaints, while serology is less accurate and appears to be less useful diagnostically.
Mycobacterium kansasii is a nontuberculous mycobacterium that can cause serious pulmonary disease. Genotyping suggested that the species is composed of at least six subtypes that vary in clinical significance, with subtype I being clinically dominant but less commonly isolated from environmental sources. Here we report a population genomics study of 358 M. kansasii isolates obtained from global water and clinical sources. Phylogenomic analyses revealed that the six subtypes are more accurately designated as closely related subspecies. These subspecies show ample evidence of recombination mediated by distributive conjugative transfer that has contributed to subspeciation and on-going diversification. Water was confirmed as a source of clinical infections by showing that genomes of clinical strains from an Australian outbreak were almost indistinguishable from strains contaminating the drinking water supply. Most clinical infections (nearly 80%) were due to a recently emerged group of strains designated the M. kansasii main complex (MKMC), which appears to have originated in Europe in 1900s and expanded globally over the past century. Comparative genomic analyses revealed that the MKMC has maintained the methylcitrate cycle and expanded ESX-I secretion-associated proteins, perhaps facilitating metabolic adaptation and pathogenicity for human hosts. Evidence of on-going positive selection in isolates of the MKMC was found in genes involved in carbon and secondary metabolism, metal ion homeostasis and cell surface remodeling that could represent adaptation to human hosts. These results further our understanding of the epidemiology and pathogenicity of M. kansasii and emphasize the importance of monitoring its potential transition to a more human-adapted pathogen.
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