Parasitic Nematodes Exert Antimicrobial Activity and Benefit From Microbiota-Driven Support for Host Immune Regulation

Intestinal parasitic nematodes live in intimate contact with the host microbiota. Changes in the microbiome composition during nematode infection affect immune control of the parasites and shifts in the abundance of bacterial groups have been linked to the immunoregulatory potential of nematodes. Here we asked if the small intestinal parasite Heligmosomoides polygyrus produces factors with antimicrobial activity, senses its microbial environment and if the anti-nematode immune and regulatory responses are altered in mice devoid of gut microbes. We found that H. polygyrus excretory/secretory products exhibited antimicrobial activity against gram+/− bacteria. Parasites from germ-free mice displayed alterations in gene expression, comprising factors with putative antimicrobial functions such as chitinase and lysozyme. Infected germ-free mice developed increased small intestinal Th2 responses coinciding with a reduction in local Foxp3+RORγt+ regulatory T cells and decreased parasite fecundity. Our data suggest that nematodes sense their microbial surrounding and have evolved factors that limit the outgrowth of certain microbes. Moreover, the parasites benefit from microbiota-driven immune regulatory circuits, as an increased ratio of intestinal Th2 effector to regulatory T cells coincides with reduced parasite fitness in germ-free mice

Parasitic Nematodes Exert Antimicrobial Activity and Benefit From Microbiota-Driven Support for Host Immune Regulation

Intestinal parasitic nematodes live in intimate contact with the host microbiota. Changes in the microbiome composition during nematode infection affect immune control of the parasites and shifts in the abundance of bacterial groups have been linked to the immunoregulatory potential of nematodes. Here we asked if the small intestinal parasite Heligmosomoides polygyrus produces factors with antimicrobial activity, senses its microbial environment and if the anti-nematode immune and regulatory responses are altered in mice devoid of gut microbes. We found that H. polygyrus excretory/secretory products exhibited antimicrobial activity against gram+/− bacteria. Parasites from germ-free mice displayed alterations in gene expression, comprising factors with putative antimicrobial functions such as chitinase and lysozyme. Infected germ-free mice developed increased small intestinal Th2 responses coinciding with a reduction in local Foxp3+RORγt+ regulatory T cells and decreased parasite fecundity. Our data suggest that nematodes sense their microbial surrounding and have evolved factors that limit the outgrowth of certain microbes. Moreover, the parasites benefit from microbiota-driven immune regulatory circuits, as an increased ratio of intestinal Th2 effector to regulatory T cells coincides with reduced parasite fitness in germ-free mice.Peer Reviewe

Transmission of SARS-CoV-2 among children and staff in German daycare centres

In daycare centres, the close contact of children with other children and employees favours the transmission of infections. The majority of children <6 years attend daycare programmes in Germany, but the role of daycare centres in the SARS-CoV-2 pandemic is unclear. We investigated the transmission risk in daycare centres and the spread of SARS-CoV-2 to associated households. 30 daycare groups with at least one recent laboratory-confirmed SARS-CoV-2 case were enrolled in the study (10/2020–06/2021). Close contact persons within daycare and households were examined over a 12-day period (repeated SARS-CoV-2 PCR tests, genetic sequencing of viruses, symptom diary). Households were interviewed to gain comprehensive information on each outbreak. We determined primary cases for all daycare groups. The number of secondary cases varied considerably between daycare groups. The pooled secondary attack rate (SAR) across all 30 daycare centres was 9.6%. The SAR tended to be higher when the Alpha variant was detected (15.9% vs. 5.1% with evidence of wild type). The household SAR was 53.3%. Exposed daycare children were less likely to get infected with SARS-CoV-2 than employees (7.7% vs. 15.5%). Containment measures in daycare programmes are critical to reduce SARS-CoV-2 transmission, especially to avoid spread to associated households.Peer Reviewe

Synopse virologischer Analysen im Nationalen Referenzzentrum für Influenzaviren während der COVID-19-Pandemie

Das Nationale Referenzzentrum für Influenzaviren gewinnt durch die fortlaufende Untersuchung von Proben aus den Sentinelpraxen der Arbeitsgemeinschaft Influenza einen umfassenden Überblick über die zirkulierenden respiratorischen Erreger in Deutschland. Dazu gehören neben SARS-CoV-2 und den Influenzaviren auch das Respiratorische Synzytialvirus, Parainfluenzaviren, humane Metapneumoviren, humane saisonale Coronaviren und humane Rhinoviren. Die Analyseergebnisse von 15.660 Sentinelproben sowie weiteren Isolaten im Zeitraum von Kalenderwoche 5/2020 bis 21/2022 werden im Epidemiologischen Bulletin 22/2022 vorgestellt. Beschrieben werden außerdem die Zirkulation respiratorischer Erreger im Vergleich zu vorpandemischen Saisons, die molekulare Charakterisierung und phylogenetische Analysen, die Überprüfung der Passgenauigkeit der eingesetzten Influenzaimpfstoffe und die Resistenzprüfung von Influenzaviren

Microbiomes in the insectivorous bat species Mops condylurus rapidly converge in captivity

Bats are well known reservoir hosts for RNA and DNA viruses. The use of captive bats in research has intensified over the past decade as researchers aim to examine the virus-reservoir host interface. In this study, we investigated the effects of captivity on the fecal bacterial microbiome of an insectivorous microbat, Mops condylurus, a species that roosts in close proximity to humans and has likely transmitted viral infections to humans. Using amplicon 16S rRNA gene sequencing, we characterized changes in fecal bacterial community composition for individual bats directly at the time of capture and again after six weeks in captivity. We found that microbial community richness by measure of the number of observed operational taxonomic units (OTUs) in bat feces increases in captivity. Importantly, we found the similarity of microbial community structures of fecal microbiomes between different bats to converge during captivity. We propose a six week-acclimatization period prior to carrying out infection studies or other research influenced by the microbiome composition, which may be advantageous to reduce variation in microbiome composition and minimize biological variation inherent to in vivo experimental studies.Peer Reviewe

Comparative Genomic Analysis of Two Novel Sporadic Shiga Toxin-Producing <i>Escherichia coli</i> O104:H4 Strains Isolated 2011 in Germany

<div><p>A large outbreak of gastrointestinal disease occurred in 2011 in Germany which resulted in almost 4000 patients with acute gastroenteritis or hemorrhagic colitis, 855 cases of a hemolytic uremic syndrome and 53 deaths. The pathogen was an uncommon, multiresistant <i>Escherichia coli</i> strain of serotype O104:H4 which expressed a Shiga toxin characteristic of enterohemorrhagic <i>E</i>. <i>coli</i> and in addition virulence factors common to enteroaggregative <i>E</i>. <i>coli</i>. During post-epidemic surveillance of Shiga toxin-producing <i>E</i>. <i>coli</i> (STEC) all but two of O104:H4 isolates were indistinguishable from the epidemic strain. Here we describe two novel STEC O104:H4 strains isolated in close spatiotemporal proximity to the outbreak which show a virulence gene panel, a Shiga toxin-mediated cytotoxicity towards Vero cells and aggregative adherence to Hep-2 cells comparable to the outbreak strain. They differ however both from the epidemic strain and from each other, by their antibiotic resistance phenotypes and some other features as determined by routine epidemiological subtyping methods. Whole genome sequencing of these two strains, of ten outbreak strain isolates originating from different time points of the outbreak and of one historical sporadic EHEC O104:H4 isolate was performed. Sequence analysis revealed a clear phylogenetic distance between the two variant strains and the outbreak strain finally identifying them as epidemiologically unrelated isolates from sporadic cases. These findings add to the knowledge about this emerging pathogen, illustrating a certain diversity within the bacterial core genome as well as loss and gain of accessory elements. Our results do also support the view that distinct new variants of STEC O104:H4 repeatedly might originate from yet unknown reservoirs, rather than that there would be a continuous diversification of a single epidemic strain established and circulating in Germany after the large outbreak in 2011.</p></div

Phylogeny of the 13 STEC O104:H4 isolates under investigation and of ten more STEC O104:H4 strains based on selected SNPs in their published genome sequences assignes the two German sporadic isolates 11–06681 and 11–07153 to a clade clearly separate from the one containing the 2011 outbreak strain isolates.

<p>The tree was calculated using the MrBayes tool from the GENEIOUS software [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.ref026" target="_blank">26</a>] and routed to the German historical isolate 01–09591 which served as outgroup. The sequences for EL-2071 and EL-2050, two sporadic isolates from cases in Georgia in 2009 and C-3493, an isolate obtained in the USA from a person with travelling history to Germany in May 2011 were published by Ahmed et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.ref021" target="_blank">21</a>]. The sequences for Ec04-8351 and Ec09-7901, two historical strains from France and the sequences of Ec11-9450, Ec11-9941, Ec11-9990, Ec12-0456, Ec12-0466, five more recent sporadic isolates from France were published by Grad et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.ref022" target="_blank">22</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.ref023" target="_blank">23</a>]. The selected SNPs used for tree calculation are given in supplementary files <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.s001" target="_blank">S1 Dataset</a> (SNP positions) and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122074#pone.0122074.s002" target="_blank">S2 Dataset</a> (sequences).</p

The two sporadic STEC O104:H4 strains 11–06681 and 11–07153 and the outbreak strain isolate 11–02027 show comparable levels of toxicity towards Vero cells.

<p>EHEC EDL933 served as a positive control and <i>E</i>. <i>coli</i> K12 C600 as a negative control. Toxicity of strain EDL933 as a quantitative reference was set to 100%. Shown are mean values of three independent experiments, each performed in triplicates. Bars represent means and standard deviation of three experiments. No significant difference in cytotoxicity of the STEC strains was observed.</p