Microbiome of the External Auditory Canal: Changes After Long-Term Hearing Aid Use.

OBJECTIVE: To investigate the microbial changes of long-term hearing aid use culture independently. STUDY DESIGN: Cross-sectional study. PATIENTS: Fifty long-term hearing aid users and 80 volunteer controls with asymptomatic ears. INTERVENTION: External auditory canal (EAC) sampling with DNA-free swabs. MAIN OUTCOME MEASURES: Microbial communities in the samples were investigated with amplicon sequencing of the 16S rRNA gene. RESULTS: The final analysis contained 48 hearing aid users, 59 controls. Twenty-four samples were excluded because of low sequence count, recent use of antimicrobials and/or corticosteroids, recent cold, or missing health status. The groups showed significant differences in bacterial diversity (beta div., p = 0.011), and hearing aid users showed lower species richness than the control group (alpha div., p < 0.01). The most frequent findings in both groups were Staphylococcus auricularis , Alloiococcus otitis , Cutibacterium acnes , Corynebacterium otitidis , and Staphylococcus unclassified sp. Hearing aid users' samples presented more Corynebacterium tuberculostearicum than the control samples. Common EAC pathogens, such as Staphylococcus aureus or Pseudomonas aeruginosa were rare. CONCLUSION: Long-term hearing aid use lowers bacterial diversity and modulates the EAC microbiome. The changes mostly affect commensals. Lowered diversity may predispose individuals to EAC conditions and needs more research.

SARS-CoV-2 variant with mutations in N gene affecting detection by widely used PCR primers.

While most of the spontaneous mutations in the viral genome have no functional, diagnostic, or clinical consequences, some have. In February 2021, we noticed in Southern Finland coronavirus disease 2019 cases where two commercial polymerase chain reaction (PCR) analyses failed to recognize the used N gene target but recognized the other target gene of severe acute respiratory syndrome coronavirus 2. Complete viral genome sequence analysis of the strains revealed several mutations that were not found at that time in public databases. A short 3 bp deletion and three subsequent single nucleotide polymorphisms in the N gene were found exactly at the site where an early published and widely used N gene-based PCR primer is located, explaining the negative results in the N gene PCR. Later the variant strain was identified as a member of the B.1.1.318 Pango lineage that had first been found from Nigerian samples collected in January 2021. This strain shares with the Beta variant the S gene E484K mutation linked to impaired vaccine protection, but differs from this variant in several other ways, for example by deletions in the N gene region. Mutations in the N gene causing diagnostic resistance and on the other hand E484K mutation in the causing altered infectivity warrants careful inspection on virus variants that might get underdiagnosed.

Phenotypic effects of dietary stress in combination with a respiratory chain bypass in mice.

The alternative oxidase (AOX) from Ciona intestinalis was previously shown to be expressible in mice and to cause no physiological disturbance under unstressed conditions. Because AOX is known to become activated under some metabolic stress conditions, resulting in altered energy balance, we studied its effects in mice subjected to dietary stress. Wild-type mice (Mus musculus, strain C57BL/6JOlaHsd) fed a high-fat or ketogenic (high-fat, low-carbohydrate) diet show weight gain with increased fat mass, as well as loss of performance, compared with chow-fed animals. Unexpectedly, AOX-expressing mice fed on these metabolically stressful, fat-rich diets showed almost indistinguishable patterns of weight gain and altered body composition as control animals. Cardiac performance was impaired to a similar extent by ketogenic diet in AOX mice as in nontransgenic littermates. AOX and control animals fed on ketogenic diet both showed wide variance in weight gain. Analysis of the gut microbiome in stool revealed a strong correlation with diet, rather than with genotype. The microbiome of the most and least obese outliers reared on the ketogenic diet showed no consistent trends compared with animals of normal body weight. We conclude that AOX expression in mice does not modify physiological responses to extreme diets.

Bracketing phenogenotypic limits of mammalian hybridization.

An increasing number of mammalian species have been shown to have a history of hybridization and introgression based on genetic analyses. Only relatively few fossils, however, preserve genetic material, and morphology must be used to identify the species and determine whether morphologically intermediate fossils could represent hybrids. Because dental and cranial fossils are typically the key body parts studied in mammalian palaeontology, here we bracket the potential for phenotypically extreme hybridizations by examining uniquely preserved cranio-dental material of a captive hybrid between grey and ringed seals. We analysed how distinct these species are genetically and morphologically, how easy it is to identify the hybrids using morphology and whether comparable hybridizations happen in the wild. We show that the genetic distance between these species is more than twice the modern human-Neanderthal distance, but still within that of morphologically similar species pairs known to hybridize. By contrast, morphological and developmental analyses show grey and ringed seals to be highly disparate, and that the hybrid is a predictable intermediate. Genetic analyses of the parent populations reveal introgression in the wild, suggesting that grey-ringed seal hybridization is not limited to captivity. Taken together, we postulate that there is considerable potential for mammalian hybridization between phenotypically disparate taxa.

Dietary supplementation with yeast hydrolysate in pregnancy influences colostrum yield and gut microbiota of sows and piglets after birth.

Dietary supplementation with yeast derivatives (YD) contributes to the health and physiology of sows and piglets, but few studies have focused on how it influences gut health and performance of sows and piglets. The goal was therefore to examine whether YD, based on brewer's yeast hydrolysate added to pregnancy diet, would affect colostrum composition, yield (CY) and gut microbiota of sows and piglets. Sows were allocated to either a control diet (n = 19) or a control diet supplemented with 2g YD/kg (n = 18) during the pregnancy. Piglets suckling belonging to the control sows (n = 114) and supplemented sows (n = 108) were also included in the study. Gut microbiota populations of sows at farrowing and piglets at one and four weeks of age were assessed using 16S rRNA gene sequencing. Colostrum samples were examined for nutritional composition and immunoglobulin (Ig) content. All piglets were individually weighed at birth and 24 hours later in order to calculate CY, and later at four weeks to calculate average daily gain (ADG). Protein, lactose and dry matter content of colostrum did not significantly differ between the two groups, while sows fed YD had higher levels of fat in their colostrum (P < 0.05). Immunoglobulin A, IgM and IgG levels in colostrum did not differ between the two groups (P >0.05). Colostrum yield was lower in the control than that in YD group (3701g vs. 4581 g; P <0.05). Although the YD supplementation did not change fecal bacteria diversity in sow, more beneficial and fermentative bacteria (Roseburia, Paraprevotella, Eubacterium) were found in the YD fed group (P <0.01) while, some opportunistic pathogens, including Proteobacteria, especially the genera Desulfovibrio, Escherichia/Shigella and Helicobacter, were suppressed. Piglets at one week of age from sows fed YD had more beneficial microbial populations with significant diversity and fewer opportunistic pathogens. Additionally, we established a Pearson's correlations between CY, colostrum components, piglet birth weight and fecal microbiota. Therefore, YD added to the sow diet during pregnancy increases colostrum availability and its energy content for neonate piglets, also promoting beneficial maternal microbial sources for neonate.