The mechanism by which chlamydiae persist in vivo remains undefined; however, chlamydiae in most animals persist in the gastrointestinal tract (GI) and are transmitted via the fecal-oral route. Oral infection of mice with Chlamydia muridarum was previously shown to establish a long-term persistent infection in the GI tract. In this study, BALB/c, DBA/2 and C57Bl/6 mice, infected orally with C. muridarum, were infected in the cecum for as long as 100 days in the absence of pathology. The primary target tissue was the cecum although the large intestine was also infected in most animals. A strong serum IgG and cecal IgA antibody response developed. Lymphocyte proliferation assays to chlamydial antigen on mesenteric lymph node cells were positive by day 10 and peaked on days 15–21, but the response returned to baseline levels by 50 days, despite the ongoing presence of the organism in the cecum. Since studies have shown that women and men become infected orally with chlamydiae, we propose that the GI tract is a site of persistent infection and that immune down-regulation in the gut allows chlamydiae to persist indefinitely. As a result, women may become reinfected via contamination of the genital tract from the lower GI tract.
The mouse chlamydial pathogen Chlamydia muridarum has been used as a model organism for the study of human Chlamydia trachomatis urogenital and respiratory tract infections. To date, two commonly used C. muridarum isolates have been used interchangeably and are essentially taken to be identical. Herein, we present data that indicate that this is not the case. The C. muridarum Weiss isolate and C. muridarum Nigg isolate varied significantly in their virulences in vivo and possessed different growth characteristics in vitro. Distinct differences were observed in intravaginal 50% infectious doses and in challenge infections, with the Weiss isolate displaying greater virulence. Respiratory infection by the intranasal route also indicated a greater virulence of the Weiss isolate. In vitro, morphometric analysis revealed that the Weiss isolate produced consistently smaller inclusions in human cervical adenocarcinoma cells (HeLa 229) and smaller plaques in monolayers of mouse fibroblasts (L929) than did the Nigg isolate. In addition, the Weiss isolate possessed significantly higher replicative yields in vitro than did the Nigg isolate. In plaque-purified isolates derived from our stocks of these two strains, total genomic sequencing identified several unique nonsynonymous single nucleotide polymorphisms and insertion/deletion mutations when our Weiss (n ؍ 4) and Nigg (n ؍ 5) isolates were compared with the published Nigg sequence. In addition, the two isolates shared 11 mutations compared to the published Nigg sequence. These results prove that there is genotypic and virulence diversity among C. muridarum isolates. These findings can be exploited to determine factors related to chlamydial virulence and immunity.
BackgroundThe gut microbiota of breast-fed and formula-fed infants differ significantly, as do the risks for allergies, gut dysfunction, and upper respiratory tract infections. The connections between breast milk, various formulas, and the profiles of gut bacteria to these childhood illnesses, as well as the mechanisms underlying the effects, are not well understood.MethodsWe investigated distal colon microbiota by 16S RNA amplicon sequencing, morphology by histomorphometry, immune response by cytokine expression, and tryptophan metabolism in a pig model in which piglets were sow-fed, or fed soy or dairy milk-based formula from postnatal day (PND) 2 to 21.ResultsFormula feeding significantly (p < 0.05) altered the colon microbiota relative to the sow feeding. A significant reduction in microbial diversity was noted with formula groups in comparison to sow-fed. Streptococcus, Blautia, Citrobacter, Butrycimonas, Parabacteroides, Lactococcus genera were increased with formula feeding relative to sow feeding. In addition, relative to sow feeding, Anaerotruncus, Akkermansia, Enterococcus, Acinetobacter, Christensenella, and Holdemania were increased in milk-fed piglets, and Biliophila, Ruminococcus, Clostridium were increased in soy-fed piglets. No significant gut morphological changes were noted. However, higher cytokine mRNA expression (BMP4, CCL11, CCL21) was observed in the distal colon of formula groups. Formula feeding reduced enterochromaffin cell number and serotonin, but increased tryptamine levels relative to sow feeding.ConclusionOur data confirm that formula diet alters the colon microbiota and appears to shift tryptophan metabolism from serotonin to tryptamine, which may lead to greater histamine levels and risk of allergies in infants.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-017-0297-z) contains supplementary material, which is available to authorized users.
Background Neonatal diet has a large influence on child health and might modulate changes in fecal microbiota and metabolites. Objectives The aim is to investigate fecal microbiota and metabolites at different ages in infants who were breastfed (BF), received dairy-based milk formula (MF), or received soy-based formula (SF). Methods Fecal samples were collected at 3 (n = 16, 12, and 14, respectively), 6 (n = 20, 19, and 15, respectively), 9 (n = 12, 11, and 12, respectively), and 12 mo (n = 14, 14, and 15, respectively) for BF, MF, and SF infants. Infants that breastfed until 9 mo and switched to formula were considered as no longer breastfeeding at 12 mo. Microbiota data were obtained using 16S ribosomal RNA sequencing. Untargeted metabolomics was conducted using a Q-Exactive Hybrid Quadrupole-Orbitrap mass spectrometer. The data were analyzed using R (version 3.6.0) within the RStudio (version 1.1.463) platform. Results At 3, 6, and 9 mo of age BF infants had the lowest α-diversity, SF infants had the highest diversity, and MF was intermediate. Bifidobacterium was 2.6- to 5-fold lower in SF relative to BF infants through 1 y of life. An unidentified genus from Ruminococcaceae higher in the SF (2%) than in the MF (0.4%) and BF (0.08%) infants at 3 mo of age was observed. In BF infants higher levels of butyric acid, d-sphingosine, kynurenic acid, indole-3-lactic acid, indole-3-acetic acid, and betaine were observed than in MF and SF infants. At 3 mo Ruminococcaceae was positively correlated to azelaic, gentisic, isocitric, sebacic, and syringic acids. At 6 mo Oscillospira was negatively correlated with 3-hydroxybutyric-acid, hydroxy-hydrocinnamic acid, and betaine whereas Bifidobacterium was negatively associated with 5-hydroxytryptamine. At 12 mo of age, Lachnospiraceae was negatively associated with hydroxyphenyllactic acid. Conclusions Infant diet has a large impact on the fecal microbiome and metabolome in the first year of life. This study was registered at clinicaltrials.gov as NCT00616395.
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