No abstract

To establish the prevalence of mobile colistin resistance (mcr) genes amongst Salmonella enterica isolates obtained through public health surveillance in England (April 2014 to September 2017), 33 205 S . enterica genome sequences obtained from human, food, animal and environmental isolates were screened for the presence of mcr variants 1 to 8. The mcr-positive genomes were assembled, annotated and characterized according to plasmid type. Nanopore sequencing was performed on six selected isolates with putative novel plasmids, and phylogenetic analysis was used to provide an evolutionary context for the most commonly isolated clones. Fifty-two mcr-positive isolates were identified, of which 32 were positive for mcr-1, 19 for mcr-3 and 1 for mcr-5. The combination of Illumina and Nanopore sequencing identified three novel mcr-3 plasmids and one novel mcr-5 plasmid, as well as the presence of chromosomally integrated mcr-1 and mcr-3. Monophasic S. enterica serovar Typhimurium accounted for 27/52 (52 %) of the mcr-positive isolates, with the majority clustering in clades associated with travel to Southeast Asia. Isolates in these clades were associated with a specific plasmid range and an additional extended-spectrum beta-lactamase genotype. Routine whole-genome sequencing for public health surveillance provides an effective screen for novel and emerging antimicrobial determinants, including mcr. Complementary long-read technologies elucidated the genomic context of resistance determinants, offering insights into plasmid dissemination and linkage to other resistance genes.

Background: Robust serological assays are essential for long-term control of the COVID-19 pandemic. Many recently released point-of-care (PoCT) serological assays have been distributed with little pre-market validation. Methods: Performance characteristics for five PoCT lateral flow devices approved for use in Australia were compared to a commercial enzyme immunoassay (ELISA) and a recently described novel surrogate virus neutralisation test (sVNT). Results: Sensitivities for PoCT ranged from 51.8% (95% CI 43.1 to 60.4%) to 67.9% (95% CI 59.4-75.6%), and specificities from 95.6% (95% CI 89.2-98.8%) to 100.0% (95% CI 96.1-100.0%). Overall ELISA sensitivity for either IgA or IgG detection was 67.9% (95% CI 59.4-75.6), increasing to 93.8% (95% CI 85.0-98.3%) for samples >14 days post symptom onset. Overall, sVNT sensitivity was 60.9% (95% CI 53.2-68.4%), rising to 91.2%% (95% CI 81.8-96.7%) for samples collected >14 days post-symptom onset, with a specificity 94.4% (95% CI 89.2-97.5%), Conclusion: Performance characteristics for COVID-19 serological assays were generally lower than those reported by manufacturers. Timing of specimen collection relative to onset of illness or infection is crucial in the reporting of performance characteristics for COVID-19 serological assays. The optimal algorithm for implementing serological testing for COVID-19 remains to be determined, particularly in low-prevalence settings.

Background Robust serological assays are essential for long-term control of the COVID-19 pandemic. Many recently released point-of-care (PoCT) serological assays have been distributed with little premarket validation. Methods Performance characteristics for 5 PoCT lateral flow devices approved for use in Australia were compared to a commercial enzyme immunoassay (ELISA) and a recently described novel surrogate virus neutralization test (sVNT). Results Sensitivities for PoCT ranged from 51.8% (95% confidence interval [CI], 43.1%–60.4%) to 67.9% (95% CI, 59.4%–75.6%), and specificities from 95.6% (95% CI, 89.2%–98.8%) to 100.0% (95% CI, 96.1%–100.0%). ELISA sensitivity for IgA or IgG detection was 67.9% (95% CI, 59.4%–75.6%), increasing to 93.8% (95% CI, 85.0%–98.3%) for samples >14 days post symptom onset. sVNT sensitivity was 60.9% (95% CI, 53.2%–68.4%), rising to 91.2% (95% CI, 81.8%–96.7%) for samples >14 days post symptom onset, with specificity 94.4% (95% CI, 89.2%–97.5%). Conclusions Performance characteristics for COVID-19 serological assays were generally lower than those reported by manufacturers. Timing of specimen collection relative to onset of illness or infection is crucial in reporting of performance characteristics for COVID-19 serological assays. The optimal algorithm for implementing serological testing for COVID-19 remains to be determined, particularly in low-prevalence settings.