Current Distribution of Rodentibacter Species Among the Mice and Rats of an Experimental Facility

Unraveling intestinal microbiota's dominance in polycystic ovary syndrome pathogenesis over vaginal microbiota

Background

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disease in women, intricately linked to hormonal imbalances. The microbiota composition plays a pivotal role in influencing hormonal levels within the body. In this study, we utilized a murine model to investigate how intestinal and vaginal microbiota interact with hormones in the development of PCOS.

Methods

Twenty female mice were randomly assigned to the normal group (N) and the model group (P), where the latter received daily subcutaneous injections of 0.1 mL DHEA (6 mg/100 g). Throughout the experiment, we evaluated the PCOS mouse model by estrus cycle, serum total testosterone (T), prolactin (PRL) and luteinizing hormone (LH) levels, and ovarian pathological morphology. The microbial composition in both intestinal content and vaginal microbiota were studied by 16S rRNA gene high-throughput sequencing.

Results

Compared with the N group, the P group showed significant increases in body weight, T, and PRL, with significant decrease in LH. Ovaries exhibited polycystic changes, and the estrous cycle was disrupted. The intestinal microbiota result shows that Chao1, ACE, Shannon and Simpson indexes were decreased, Desulfobacterota and Acidobacteriota were increased, and Muribaculaceae, Limosilactobacillus and Lactobacillus were decreased in the P group. T was significantly positively correlated with Enterorhabdus, and LH was significantly positively correlated with Lactobacillus. The analysis of vaginal microbiota revealed no significant changes in Chao1, ACE, Shannon, and Simpson indices. However, there were increased in Firmicutes, Bacteroidota, Actinobacteriota, Streptococcus, and Muribaculaceae. Particularly, Rodentibacter displayed a robust negative correlation with other components of the vaginal microbiota.

Conclusion

Therefore, the response of the intestinal microbiota to PCOS is more significant than that of the vaginal microbiota. The intestinal microbiota is likely involved in the development of PCOS through its participation in hormonal regulation.

Microbiota of the Pregnant Mouse: Characterization of the Bacterial Communities in the Oral Cavity, Lung, Intestine, and Vagina through Culture and DNA Sequencing

Mice are frequently used as animal models for mechanistic studies of infection and obstetrical disease, yet characterization of the murine microbiota during pregnancy is lacking. The objective of this study was to characterize the microbiotas of distinct body sites of the pregnant mouse—vagina, oral cavity, intestine, and lung—that harbor microorganisms that could potentially invade the murine amniotic cavity, thus leading to adverse pregnancy outcomes. The microbiotas of these body sites were characterized through anoxic, hypoxic, and oxic culture as well as through 16S rRNA gene sequencing. With the exception of the vagina, the cultured microbiotas of each body site varied by atmosphere, with the greatest diversity in the cultured microbiota appearing under anoxic conditions. Only cultures of the vagina were comprehensively representative of the microbiota observed through direct DNA sequencing of body site samples, primarily due to the predominance of two Rodentibacter strains. Identified as Rodentibacter pneumotropicus and Rodentibacter heylii, these isolates exhibited predominance patterns similar to those of Lactobacillus crispatus and Lactobacillus iners in the human vagina. Whole-genome sequencing of these Rodentibacter strains revealed shared genomic features, including the ability to degrade glycogen, an abundant polysaccharide in the vagina. In summary, we report body site-specific microbiotas in the pregnant mouse with potential ecological parallels to those of humans. Importantly, our findings indicate that the vaginal microbiotas of pregnant mice can be readily cultured, suggesting that mock vaginal microbiotas can be tractably generated and maintained for experimental manipulation in future mechanistic studies of host vaginal-microbiome interactions.

IMPORTANCE Mice are widely utilized as animal models of obstetrical complications; however, the characterization of the murine microbiota during pregnancy has been neglected. Microorganisms from the vagina, oral cavity, intestine, and lung have been found in the intra-amniotic space, where their presence threatens the progression of gestation. Here, we characterized the microbiotas of pregnant mice and established the appropriateness of culture in capturing the microbiota at each site. The high relative abundance of Rodentibacter observed in the vagina is similar to that of Lactobacillus in humans, suggesting potential ecological parallels. Importantly, we report that the vaginal microbiota of the pregnant mouse can be readily cultured under hypoxic conditions, demonstrating that mock microbial communities can be utilized to test the potential ecological parallels between microbiotas in human and murine pregnancy and to evaluate the relevance of the structure of these microbiotas for adverse pregnancy outcomes, especially intra-amniotic infection and preterm birth.

Effects of Antibiotic Use on Saliva Antibody Content and Oral Microbiota in Sprague Dawley Rats

Antibiotics are often used to treat systemic diseases not associated with the oral cavity. This application of antibiotics may affect the healthy oral microbiota community, as it destroys the balance between specific bacterial populations throughout the ecosystem and may lead to dysbacteriosis. We hypothesized that the effects on antibiotics on oral microbiota regulation and function would affect antibody content in saliva, depending on the antibiotic type. To address this, a total of 24 Sprague Dawley rats (divided into 4 cages, 6 per pen) were administered amoxicillin (AMX), spiramycin (SP), metronidazole (MTZ), or water (control) daily for 14 days (gavage). After treatment was completed, high-throughput sequencing of 16S rRNA genes was used to determine changes in the composition, metabolic function, and diversity of oral microbiota in the rats. Enzyme-linked immunosorbent assay was used to detect antibodies in saliva, including SIgA, IgG, and IgM. Results showed that AMX, MTZ, and SP significantly affected oral microbiota composition, diversity, and metabolic function in rats. AMX induced substantial changes in the rat salivary antibody concentrations. At the genus level, the relative abundance of Rothia and Haemophilus was higher in the AMX group than in the other groups. In conclusion, antibiotics-induced changes in oral microbiota populations may be associated with changes in salivary antibody concentrations. However, the specific interaction mechanisms remain unknown, and it is still unclear whether significant changes in the oral microbiota cause changes in salivary antibody concentrations or vice versa.

Bacteriological and pathological investigations on the preputial glands of one-year-old C57BL/6NCrl mice maintained in individually ventilated cages

Spontaneous infections of the preputial glands represent overlooked health problems in mice that could raise welfare concerns and potentially confound scientific experiments. Agents involved in preputial gland infections have rarely been investigated, with opportunistic pathogens of laboratory animals usually detected in inflamed preputial glands. The aim of this study was to investigate the prevalence of bacterial infection in the preputial glands and the relationship between haematological and pathological changes and infection status. We analysed 40 preputial glands from 20 one-year-old C57BL/6NCrl male mice by using bacteriology, haematology and pathology. Bacteria were isolated from 16/20 (80%) mice, for a total of 32/40 (80%) examined preputial glands. Enterobacter cloacae, Pasteurella spp., Klebsiella spp. and Staphylococcus aureus were identified in 35%, 17.5%, 15% and 12.5% of the examined glands, respectively. Preputial gland inflammation was identified in 29/40 (72.5%) glands and was classified as chronic interstitial adenitis in 27 cases and suppurative adenitis in the remaining two glands. No haematological changes were found in mice with infected glands. Histologically, the presence of intralesional bacteria, intraluminal necrotic material, intraluminal keratin accumulation, interstitial inflammatory cell infiltrate and granulocytes (intraluminal and/or interstitial), along with total inflammatory score and total histopathological score, were significantly increased in infected glands and correlated with the bacterial load. Most severe inflammatory changes were identified after S. aureus infection, while ductal hyperkeratosis was significantly increased in glands infected with Klebsiella spp. In conclusion, preputial gland infection was a common event in one-year-old C57BL/6NCrl mice, and bacterial load correlated with pathological findings, while systemic effects were not highlighted by haematology.

Identification of a large repetitive RTX immunogen in a highly virulent Rodentibacter heylii strain

Rodentibacter (R.) heylii is frequently detected in laboratory rodents. Repeats in toxin (RTX) toxins are considered important virulence factors of this major murine pathogen. We evaluated the virulence of a R.heylii strain negative for all known RTX toxin genes and Muribacter (M.) muris, a commensal in mice, in experimental infections of C57BL/6 and BALB/c mice. Experimental intranasal infection with 108 CFU of the pnxI-, pnxII- and pnxIII- R. heylii strain resulted in 75% and 100% mortality in C57BL/6 and BALB/c mice, respectively. In early losses, multiple internal organs were infected and purulent bronchopneumonia was the main pathology. Intranasal application of M. muris did not result in mortality or severe weight loss. Immunoproteomics led to the identification of a surface-associated and specific immunogen, which was designated as R. heylii immunogen A (RhiA) and which was exclusively recognised by sera obtained from mice infected with this R. heylii pathotype. RhiA is a 262.6 kDa large protein containing long imperfect tandem repeats and C-terminal RTX consensus sequences. Immunohistochemical analysis confirmed that this R.heylii pathotype expresses RhiA in the lower respiratory tract. In summary, this study describes a specific immunogen in a virulent R. heylii, strain which is an excellent antigen for pathotype-specific serological screenings and which might carry out RTX-related functions.

Differentiation among the most important Rodentibacter species by multiplex PCR assays targeting the ITSile+ala sequences of the rRNA operons

Screening for the Rodentibacter species is part of the microbiologic quality assurance programs of laboratory rodents all over the world. Nevertheless, currently there are no PCR amplification techniques available for the diagnostic of R. ratti, R. heidelbergensis and of a Rodentibacter related β-haemolytic taxon. The aim of this study was to utilize the differences in the sequence of the Internal Transcribed Spacer (ITS) regions of R. pneumotropicus, R. heylii, R. ratti, R. heidelbergensis and of the β-haemolytic Rodentibacter taxon for the design of specific PCR assays for these species. The ITS^ile+ala sequence variations allowed the design of specific forward and reverse primers for each species included, that could be combined in different multiplex assays. The performance characteristics specificity and sensitivity registered for each primer pair against a diverse collection of Pasteurellaceae isolated from rats and mice and of further non-Pasteurellaceae strains was 100% for all five Rodentibacter species included. In addition, the PCR assays displayed high limits of detection and could be successfully used for detection of Rodentibacter spp. DNA in clinical swabs of laboratory mice and rats. Overall, the assays described here represent the first PCRs able to diagnose R. ratti, R. heidelbergensis and the β-haemolytic Rodentibacter taxon, whose diagnostic to species level could further facilitate better understanding of their geographic distribution, prevalence, and biology in the future.

Differentiation Among Rodentibacter Species Based on 16S-23S rRNA Internal Transcribed Spacer Analysis

The internal transcribed spacer (ITS) regions of Rodentibacter pneumotropicus, R. heylii, R. rarus, R. ratti, and R. heidelbergensis and of a Rodentibacter- related β-hemolytic Pasteurellaceae taxon isolated from laboratory rodents were studied for their feasibility to discriminate among these species. The 6 species analyzed showed species-specific ITS patterns that were shared by the type strains and clinical isolates and that allowed their identification. Nevertheless, differentiating between the ITS band patterns of R. pneumotropicus and R. ratti is visually challenging. In all species tested, sequence analysis of the ITS fragments revealed a larger ITS^ile+ala, which contained the genes for tRNA^Ile(GAU) and tRNA ^Ala(UGC), and a smaller ITS^glu with the tRNA^Glu(UUC) gene. The ITS sequences varied among the 6 species evaluated, displaying identity levels ranging from 62% to 86% for ITS^ile+ala and 68% to 90% for ITS^glu. Overall, ITS amplification proved to be a reliable method to differentiate among these important Pasteurellaceae species of laboratory rodents. Moreover, the ITS sequence variations recorded here might facilitate the design of probes for specific identification of these species. The ability to diagnose these organisms to the species level could increase our understanding of their clinical significance.

Critical Role of Innate Immunity to Flagellin in the Absence of Adaptive Immunity

BACKGROUND

Bacterial flagellin is a major target of innate and adaptive immunity, both of which can promote and/or compensate for deficiencies in each other's function.

METHODS

To investigate the role of innate immune detection of flagellin irrespective of adaptive immunity, we examined the consequences of loss of Toll-like receptor 5 (T5) and/or Nod-like receptor 4 (N4) upon a Rag1-deficient background.

RESULTS

Mice lacking Toll-like receptor 5 and Rag1 (T5/Rag-DKO) exhibited frequent lethal Pasteurellaceae-containing abscesses that prevented breeding of these mice. Mice lacking Toll-like receptor 5, Nod-like receptor 4, and Rag1 (T5/N4/Rag-TKO) also resulted in sporadic lethal abdominal abscesses caused by similar Pasteurellaceae. In the absence of such infections, relative to Rag1-KO, T5/N4/Rag-TKO mice exhibited microbiota encroachment, low-grade inflammation, microbiota dysbiosis, and, moreover were highly prone to Citrobacter infection and developed severe colitis when adoptively transferred with colitogenic T cells. Relative proneness of T5/N4/Rag-TKO mice to T-cell colitis was ablated by antibiotics while fecal microbiota transplant from T5/N4/Rag-TKO mice to wild-type mice transferred proneness to Citrobacter infection, indicating that dysbiosis in T5/N4/Rag-TKO mice contributed to these phenotypes.

CONCLUSIONS

These results demonstrate a critical role for innate immune detection of flagellin, especially in the intestinal tract and particularly in hosts deficient in adaptive immunity.

Fatal progression of experimental visceral leishmaniasis is associated with intestinal parasitism and secondary infection by commensal bacteria, and is delayed by antibiotic prophylaxis

Leishmania donovani causes visceral leishmaniasis (VL), which is typically fatal without treatment. There is substantial variation between individuals in rates of disease progression, response to treatment and incidence of post-treatment sequelae, specifically post-kala-azar dermal leishmaniasis (PKDL). Nevertheless, the majority of infected people are asymptomatic carriers. Hamsters and mice are commonly used as models of fatal and non-fatal VL, respectively. Host and parasite genetics are likely to be important factors, but in general the reasons for heterogeneous disease presentation in humans and animal models are poorly understood. Host microbiota has become established as a factor in cutaneous forms of leishmaniasis but this has not been studied in VL. We induced intestinal dysbiosis in mice and hamsters by long-term treatment with broad-spectrum antibiotics in their drinking water. There were no significant differences in disease presentation in dysbiotic mice. In contrast, dysbiotic hamsters infected with L. donovani had delayed onset and progression of weight loss. Half of control hamsters had a rapid progression phenotype compared with none of the ABX-treated animals and the nine-month survival rate was significantly improved compared to untreated controls (40% vs. 10%). Antibiotic-treated hamsters also had significantly less severe hepatosplenomegaly, which was accompanied by a distinct cytokine gene expression profile. The protective effect was not explained by differences in parasite loads or haematological profiles. We further found evidence that the gut-liver axis is a key aspect of fatal VL progression in hamsters, including intestinal parasitism, bacterial translocation to the liver, malakoplakia and iron sequestration, none of which occurred in non-progressing murine VL. Diverse bacterial genera were cultured from VL affected livers, of which Rodentibacter was specifically absent from ABX-treated hamsters, indicating this pathobiont may play a role in promoting disease progression. The results provide experimental support for antibiotic prophylaxis against secondary bacterial infections as an adjunct therapy in human VL patients.