SARS-CoV-2 antigen tests for screening of healthcare workers; experience with over 48,000 combined antigen tests and RT-PCR tests.

BACKGROUND: To prevent spread to patients and co-workers, health care workers (HCWs) infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) should quickly be identified. Although real time polymerase chain reaction (RT-PCR) is the gold standard, this test takes several hours, during which a HCW is unable to work. Antigen (Ag) tests may be an efficacious means of screening HCWs since they are easy to perform and provide fast results. METHODS: In this study, 48,010 paired results of Ag-testing and RT-PCR, performed on HCWs between January 2021 and April 2022, were evaluated to determine the diagnostic accuracy of SARS-CoV-2 Ag-tests in diagnosing potentially infectious individuals. This analysis was performed with cycling threshold values (Ct-values) ≤30 and ≤25 as cut-offs. RESULTS: Respectively 3.1% (n = 1507) and 0.3% (n = 140) of Ag-tests were positive or indeterminate, and thus indicative for SARS-CoV-2 infection. In total, 2479 (5.2%) RT-PCRs were positive, of which 1529 (61.7%) had a Ct-value ≤25 and 402 (16.2%) a Ct-value between 26 and 30. At Ct-value ≤30 as a cut-off, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Ag-tests were 79.0%, 99.8%, 93.8% and 99.1%, respectively. At Ct-value ≤25, sensitivity further improved to 92.0%, by which the NPV increased to 99.7%. CONCLUSIONS: To prevent transmission from HCWs to patients and co-workers, while maintaining workforce capacity, Ag-tests are a valuable addition to RT-PCR tests, as they have a quick turnaround time and excellent sensitivity for identifying individuals with high potential for transmission.

Rotavirus and illness severity in children presenting with acute gastroenteritis at the primary care out-of-hours service.

BACKGROUND: Rotavirus is a common cause of acute gastroenteritis in young children in the Netherlands, where rotavirus vaccination has not yet been implemented. OBJECTIVES: To evaluate a difference in illness severity course depending on the presence of rotavirus infection and assess the prevalence of viruses and the referral rate in children with acute gastroenteritis. METHODS: A prospective cohort of children aged 6 months to 6 years presenting with acute gastroenteritis to a primary care out-of-hours service from October 2016 to March 2018. Faeces were sampled and sent to a laboratory where viral pathogens were identified and quantified by real-time polymerase chain reaction. Severe course of acute gastroenteritis was defined as a Modified Vesikari Score of ≥11. In addition, we assessed referral rates. Chi-square tests were used to evaluate differences between groups. RESULTS: We included 75 children (34 boys) with a median age of 1.5 years (interquartile range, 0.9-2.0 years). The prevalence of rotavirus was 65.3% (95% confidence interval, 53.5-76.0) with a median cycle threshold of 16.0. Severe course of acute gastroenteritis was present in 31 of 71 children (4 were lost to follow-up). Those with rotavirus (20/47) did not have a severe course more often than those without (11/24): odds ratio, 0.88 (95% confidence interval, 0.33-2.36). Referral rates were comparable for rotavirus (15.2%) and non-rotavirus (14.3%). CONCLUSION: In out-of-hours primary care, rotavirus is common but not associated with increased severity and higher referral rates in children with acute gastroenteritis.

Sofosbuvir Add-on to Ribavirin Treatment for Chronic Hepatitis E Virus Infection in Solid Organ Transplant Recipients Does Not Result in Sustained Virological Response.

Ribavirin is effective for treating immunocompromised patients with chronic hepatitis E virus infection. However, ribavirin treatment is not always successful. We describe 3 solid organ transplant recipients treated with sofosbuvir and ribavirin after failing ribavirin monotherapy. Complete elimination of hepatitis E virus could not be achieved.

An integrated approach to control a prolonged outbreak of multidrug-resistant Pseudomonas aeruginosa in an intensive care unit.

In this paper we aim to provide insight into the complexity of outbreak management in an intensive care unit (ICU) setting. In October 2010 four patients on the ICU of our tertiary care centre were colonized or infected with a multidrug-resistant strain of Pseudomonas aeruginosa (MDR-PA). An outbreak investigation was carried out and infection control measures were taken in an attempt to identify a potential source and stop transmission. The outbreak investigation included descriptive epidemiology, comprising retrospective case finding by reviewing the laboratory information system back to 2004 and prospective case finding by patient screening for MDR-PA. Furthermore, microbiological analysis, environmental screening and a case-control study were carried out. Infection control measures consisted of re-education of healthcare personnel on basic hygiene measures, auditing of hygiene procedures used in daily practice by infection control practitioners, and stepwise up-regulation of isolation measures. From February 2009 to January 2012, 44 patients on our ICU were found to be MDR-PA positive. MDR-PA isolates of the 44 patients showed two distinct AFLP patterns, with homology within each of the AFLP clusters of more than 93%. The VIM metallo-ß-lactamase gene was detected in 20 of 21 tested isolates. A descriptive epidemiology investigation identified the rooms with the highest numbers of MDR-PA positive patients. The case-control study showed three factors to be independently associated with MDR-PA positivity: admission to ICU subunit 1 (OR, 6.1; 95% CI, 1.7, 22), surgery prior to or during admission (OR, 5.7; 95% CI, 1.6, 20) and being warmed-up with the warm-air blanket (OR, 3.6; 95% CI, 1.2, 11). After three environmental screening rounds, with sampling of sinks, furniture and devices in the ICU, without revealing a clear common source, a fourth environmental investigation included culturing of faucet aerators. Two faucets were found to be positive for MDR-PA and were replaced. The occurrence of new cases decreased with the strengthening of infection control measures and declined further with the removal of the common source. With this integrated approach a prolonged outbreak of P. aeruginosa was controlled. Contaminated faucet aerators on the ICU probably served as a persisting source, while interpatient transmission by medical staff was a likely way of spread. Seven months after the last case (January 2012) and 3 months after cessation of extended isolation measures (May 2012), single cases started to occur on the ICU, with a total of seven patients in the past year. No common source has yet been found.

Nucleoside plus nucleotide analogs and cessation of hepatitis B immunoglobulin after liver transplantation in chronic hepatitis B is safe and effective.

BACKGROUND: After orthotopic liver transplantation (OLT) in chronic hepatitis B (HBV), adequate prophylaxis for recurrence of HBV in the graft is mandatory. OBJECTIVES: Evaluate safety of HBV prophylaxis with tenofovir and emtricitabine (TDF/FTC) after cessation of hepatitis B immunoglobulin (HBIG) after OLT in chronic HBV. STUDY DESIGN: In 17 consecutive patients after OLT in chronic HBV we started TDF/FTC after cessation of HBIG. All had received HBIG >6 months. 15/17 were HBsAg negative and 16/17 had undetectable HBV-DNA. RESULTS: After mean follow-up of 2 years 16/17 patients were alive, one died due to urosepsis. All 16 with undetectable HBV-DNA remained HBV-DNA negative. From 15 HBsAg negative patients at start, in one seroconversion to positive HBsAg occurred, without detectable HBV-DNA. Liver biochemistry remained within the normal ranges. There were no cases of drug discontinuation. No major side effects were reported. TDF/FTC use saves €16,262/year over standard-of-care (HBIG+LAM). This prospective follow-up study shows that in liver transplantation for chronic hepatitis B, after initial treatment including HBIG for at least 6 months combined with or followed by (dual) nucleos(t)ide analog therapy, TDF/FTC provides adequate prophylaxis against recurrent HBV infection without major side effects and leads to substantial cost savings over a regimen with HBIG. CONCLUSION: Combined prophylaxis with TDF/ETV nucleoside plus nucleotide analogs and cessation of immunoglobulin after liver transplantation in chronic hepatitis B is safe and effective.

Comparison of two matrix-assisted laser desorption ionisation-time of flight mass spectrometry methods for the identification of clinically relevant anaerobic bacteria.

Two commercially available MALDI-TOF MS systems, Bruker MS and Shimadzu MS, were compared for the identification of clinically relevant anaerobic bacteria. A selection of 79 clinical isolates, representing 19 different genera, were tested and compared with identification obtained by 16S rRNA gene sequencing. Correct genus identification was achieved for 71% of isolates by Shimadzu MS and for 61% by Bruker MS. Correct identification at the species level occurred in 61% and 51%, respectively. Shimadzu showed markedly better results for identification of Gram-positive anaerobic cocci. In contrast, the Bruker system performed better than Shimadzu for the Bacteroides fragilis group. When strains not present in the database were excluded from the analyses for each database, both systems performed equally well, with 76.7% and 75.0% correct genus identification for Shimadzu and Bruker, respectively. Similarly, when the most recently updated Bruker database was applied, no difference was observed. We conclude that the composition and quality of the database is crucial for a correct identification. The databases currently available for both systems need to be optimized before MS can be implemented for routine identification of anaerobic bacteria.

Matched follow-up study of 5 8-year-old ICSI singletons: child behaviour, parenting stress and child (health-related) quality of life.

BACKGROUND: Psychosocial follow-up of ICSI children is scarce. We compared child behaviour, parenting stress and quality of life for singletons aged 5-8 years born after ICSI, IVF and natural conception (NC). METHODS: All singletons born between June 1996 and December 1999 after ICSI in the Leiden University Medical Center were invited (n = 110). Matched singletons born after IVF and NC were recruited. Parents completed the Child Behaviour Checklist (measures problem behaviour), the Parenting Stress Index (Nijmeegse Ouderlijke Stress Index) and two quality of life questionnaires (Dux25 and TACQOL). Children completed the Dux25 Child form. RESULTS: Eighty-seven ICSI children (79%), 92 IVF children (73%) and 85 NC children enrolled. Prevalence of behavioural disorders-as reported by the parents-was comparable in the three groups. Three of 87 ICSI children had autism or an autistic spectrum disorder (ASD). Problem behaviour scores were similar for ICSI and NC children; IVF children (mainly girls) scored less problem behaviour (P < 0.05) and their scores were less often in the (borderline) clinical range. Parenting stress was similar for ICSI and IVF, but lower for NC than ICSI parents, mainly on the child scale. Quality of life scores were similar in the three conception groups. CONCLUSIONS: Prevalence of autism/ASD seemed higher after ICSI, but this unexpected finding should be confirmed by future studies with larger group sizes. ICSI parents experienced more stress than NC parents, although selection bias cannot be ruled out. The majority of ICSI singletons assessed at age 5-8 years showed a normal psychosocial well-being.

Systemic resistance in Arabidopsis induced by rhizobacteria requires ethylene-dependent signaling at the site of application.

Root colonization of Arabidopsis thaliana by the nonpathogenic, rhizosphere-colonizing, biocontrol bacterium Pseudomonas fluorescens WCS417r has been shown to elicit induced systemic resistance (ISR) against Pseudomonas syringae pv. tomato (Pst). The ISR response differs from the pathogen-inducible systemic acquired resistance (SAR) response in that ISR is independent of salicylic acid and not associated with pathogenesis-related proteins. Several ethylene-response mutants were tested and showed essentially normal symptoms of Pst infection. ISR was abolished in the ethylene-insensitive mutant etr1-1, whereas SAR was unaffected. Similar results were obtained with the ethylene-insensitive mutants ein2 through ein7, indicating that the expression of ISR requires the complete signal-transduction pathway of ethylene known so far. The induction of ISR by WCS417r was not accompanied by increased ethylene production in roots or leaves, nor by increases in the expression of the genes encoding the ethylene biosynthetic enzymes 1-aminocyclopropane-1-carboxylic (ACC) synthase and ACC oxidase. The eir1 mutant, displaying ethylene insensitivity in the roots only, did not express ISR upon application of WCS417r to the roots, but did exhibit ISR when the inducing bacteria were infiltrated into the leaves. These results demonstrate that, for the induction of ISR, ethylene responsiveness is required at the site of application of inducing rhizobacteria.

A novel signaling pathway controlling induced systemic resistance in Arabidopsis.

Plants have the ability to acquire an enhanced level of resistance to pathogen attack after being exposed to specific biotic stimuli. In Arabidopsis, nonpathogenic, root-colonizing Pseudomonas fluorescens bacteria trigger an induced systemic resistance (ISR) response against infection by the bacterial leaf pathogen P. syringae pv tomato. In contrast to classic, pathogen-induced systemic acquired resistance (SAR), this rhizobacteria-mediated ISR response is independent of salicylic acid accumulation and pathogenesis-related gene activation. Using the jasmonate response mutant jar1, the ethylene response mutant etr1, and the SAR regulatory mutant npr1, we demonstrate that signal transduction leading to P. fluorescens WCS417r-mediated ISR requires responsiveness to jasmonate and ethylene and is dependent on NPR1. Similar to P. fluorescens WCS417r, methyl jasmonate and the ethylene precursor 1-aminocyclopropane-1-carboxylate were effective in inducing resistance against P. s. tomato in salicylic acid-nonaccumulating NahG plants. Moreover, methyl jasmonate-induced protection was blocked in jar1, etr1, and npr1 plants, whereas 1-aminocyclopropane-1-carboxylate-induced protection was affected in etr1 and npr1 plants but not in jar1 plants. Hence, we postulate that rhizobacteria-mediated ISR follows a novel signaling pathway in which components from the jasmonate and ethylene response are engaged successively to trigger a defense reaction that, like SAR, is regulated by NPR1. We provide evidence that the processes downstream of NPR1 in the ISR pathway are divergent from those in the SAR pathway, indicating that NPR1 differentially regulates defense responses, depending on the signals that are elicited during induction of resistance.

Ethylene-insensitive tobacco lacks nonhost resistance against soil-borne fungi.

Enhanced ethylene production is an early response of plants to pathogen attack and has been associated with both resistance and susceptibility to disease. Tobacco plants were transformed with the mutant etr1-1 gene from Arabidopsis, conferring dominant ethylene insensitivity. Besides lacking known ethylene responses, these transformants (Tetr) did not slow growth when contacting neighboring plants, hardly expressed defense-related basic pathogenesis-related proteins, and developed spontaneous stem browning. Whereas hypersensitive resistance to tobacco mosaic virus was unimpaired, Tetr plants had lost nonhost resistance against normally nonpathogenic soil-borne fungi.

Characterization of baculovirus insecticides expressing tailored Bacillus thuringiensis CryIA(b) crystal proteins.

Full-length, truncated, and mature forms of the CryIA(b) insecticidal crystal protein gene of Bacillus thuringiensis were engineered into the p10 locus of Autographa californica nuclear polyhdrosis virus (AcNPV). A signal sequence of Heliothis virescens juvenile hormone esterase was introduced at the N-terminus of these constructs to induce secretion. All recombinants, except those containing the mature toxin, produced high levels of CryIA(b) ICPs in insect cells. Thirty percent of the intracellular protoxin was N-glycosylated, suggesting that the protoxin was translocated across the ER membrane. Secretion into the medium, however, was limited. The production of the mature toxin was poor as a result of its cytotoxicity to insect cells. In a bioassay against second instar Spodoptera exigua larvae, using a recombinant expressing the Androctonus australis scorpion toxin gene in the same p10 locus as a positive control, the median survival time of AcNPV recombinants expressing the various B. thuringiensis CryIA(b) ICP constructs was not significant different from that of wild-type AcNPV. This suggests that production and/or secretion of B. thuringiensis (pro)toxins by AcNPV p10 recombinant viruses does not increase insecticidal activity since (i) the protoxins produced are inactive and not likely to be activated in vivo; (ii) secretion of the B. thuringiensis protoxins is poor; and (iii) production of the mature toxins results in cytotoxicity.

Virus-induced gene expression for enzymes of ethylene biosynthesis in hypersensitively reacting tobacco.

A full-length cDNA clone (cEFE-26) encoding ethylene-forming enzyme (EFE) was isolated from a cDNA library, prepared from leaves of tobacco mosaic virus (TMV)-infected tobacco cultivar Samsun NN. The cDNA clone encodes a protein with 90% amino acid sequence similarity to established EFEs of tomato and other plants. By using cEFE-26 cDNA and the insert from cDNA clone pACC13 (B. A. Bailey, A. Avni, N. Li, A. K. Mattoo, and J. D. Anderson, Plant Physiol. 100:1615-1616, 1992) encoding tobacco 1-aminocyclopropane-1-carboxylic acid synthase as probes, it was established that tobacco contains small gene families for these proteins. Furthermore, RNA blot analyses indicated that transcript levels in leaves for the two ethylene pathway genes were elevated after infection with TMV. The results are discussed in relation to a possible signalling role of ethylene in induced resistance and gene expression for pathogenesis-related proteins.