In vitro investigation of the effects of Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 exopolysaccharides on tight junction damage caused by influenza virus infection.

It is a problem that influenza virus infection increases susceptibility to secondary bacterial infection in lungs leading to lethal pneumonia. We previously reported that exopolysaccharides (EPS) derived from Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 (OLL1073R-1) could prevent against influenza virus infection followed by secondary bacterial infection in vitro. Therefore, the present study assessed whether EPS derived OLL1073R-1 protects the alveolar epithelial barrier disfunction caused by influenza virus infection. After A549 cells treated with EPS or without EPS were infected influenza virus A/Puerto Rico/8/34 (IFV) for 12 h, the levels of tight junction genes expression and inflammatory genes expression were measured by reverse transcription polymerase chain reaction. As results, EPS treatment could protect against low-titer IFV infection, but not high-titer IFV infection, followed by suppression of the increased expression of inflammatory cytokine gene levels and recovery of the decrease in the expression level of ZO-1 gene that was caused by low-titer IFV infection, leading to an improvement trend in the barrier function. Our findings showed that EPS derived from OLL1073R-1 could inhibit low-titer IFV infection leading to maintenance of the epithelial barrier function through the suppression of inflammatory cytokine genes expression.

The protective effects of intranasal administration of IL-12 given before influenza virus infection and the negative effects of IL-12 treatment given after viral infection.

To investigate whether the administration of IL-12 is effective against influenza virus infection, mice were intranasally administered IL-12 for three consecutive days and then infected with a non-lethal dose of the influenza virus. The IL-12-treated mice were more resistant to the virus than control mice with respect to the remission of body weight loss, virus burden, pro-inflammatory cytokine production, and inflammatory cell infiltration in the lungs. The number of NK cells and the level of NK cell cytotoxicity significantly increased in the lungs of the mice treated with IL-12 before infection compared to that observed in control mice, leading to promptly eliminate the viral-infected cells. Unexpectedly, all of mice that received IL-12 treatment after being infected with a non-lethal dose of the virus died as a result of their high virus burden and pro-inflammatory cytokine production in the lungs. One possibility of the mechanisms was considered to be activation of myeloid-derived suppressor cell (MDSC), which has immune suppressive function, in the lungs. Thus, IL-12 treatment has opposite effects depending on whether it is administered before or after infection. These results demonstrate the potential risks of immune modulating therapies such as administration of exogenous cytokine or neutralization of cytokine. J. Med. Virol. 88:1487-1496, 2016. © 2016 Wiley Periodicals, Inc.

Microbiological assessment of Suncus murinus bred and managed as laboratory animals.

Suncus murinus is gaining prominence as a laboratory animal; however, there is no generally accepted method for microbiological monitoring. This study aimed to apply non-serological microbiological monitoring of laboratory mice for S. murinus and identify the subdominant species obtained by culture methods for microbial assessment. Culture and PCR were used to test S. murinus for the laboratory mice test panels including 10 bacterial species and orthohantaviruses, all of which were negative. The species that grew sub-dominantly in rectal feces were identified as Aeromonas hydrophila, which is pathogenic to mammals. These results indicate that microbiological monitoring should be used to detect pathogens directly from S. murinus, not from sentinel animals, due to the host-specific microbial environment.

The protective effects of lactoferrin against murine norovirus infection through inhibition of both viral attachment and replication.

The purpose of this study was to evaluate the effects of bovine lactoferrin against norovirus infection using mouse norovirus (MNV) and Raw264.7 cell in vitro. When Raw264.7 cells were infected with MNV in the presence or absence of lactoferrin, the cytotoxic damage to the infected Raw264.7 cells significantly and dose-dependently decreased and completely inhibited in the presence of 15 or 20 µg/well of lactoferrin as compared with the absence of lactoferrin. Correspondingly, the MNV titers in the culture medium and intracellularly were significantly decreased in infected Raw264.7 cells treated with lactoferrin compared to control infected Raw264.7 cells. The mechanisms responsible for the protective effects of lactoferrin against MNV infection were attributed to both its inhibition of the initial MNV attachment to cells and the subsequent interference with MNV replication. Moreover, it was revealed that lactoferrin could rapidly induce the expression of anti-viral cytokine mRNA, such as IFN-α and IFN-ß which involved in inhibition of MNV replication in infected Raw264.7 cells, in the early phase of infection. It was concluded that lactoferrin exerts protective effects against MNV infection through inhibition of both viral attachment and replication. The present results provide evidence that lactoferrin may be useful as a preventive and/or therapeutic anti-norovirus agent.

Effects of NKT Cells on Metabolic Disorders Caused by High-Fat Diet Using CD1d-Knockout Mice.

Purpose: The purpose of this study was to investigate whether NKT cells play an important role in preventing or exacerbating diseases caused by high-fat diet (HFD) using CD1d-knockout (KO) mice which lack NKT cells. Methods: Five-week-old male Balb/c (wild-type; WT) or CD1dKO mice were fed with control-diet (CTD) or HFD for 16 weeks. Results: The present study revealed four main findings. First, CD1dKO mice were susceptible to obesity caused by HFD in comparison to WT mice. Second, clinical conditions of fatty liver caused by HFD were comparable between CD1dKO mice and WT mice. Third, HFD-fed WT mice showed high levels of serum biochemical markers, involved in lipid metabolisms, in comparison to WT mice fed a CTD. Notably, the serum concentrations of ALT, T-CHO, TG and HDL-C in CD1dKO mice fed a HFD were almost comparable to those of CD1dKO mice fed a CTD. Fourth, the expression of peroxisome proliferator-activated receptor (PPAR) γ, low-density lipoprotein receptor (LDLR), CD36 of epididymal adipose tissue enhanced and proprotein convertase subtilisin/kexin type (PCSK) 9 in serum decreased. Conclusion: NKT cells were responsible for protection against HFD-induced obesity. However, CD1dKO mice were resistant to serum biochemical marker abnormalities after HFD feeding. One possible explanation is that the epididymal adipose tissue of CD1dKO mice could take up greater amounts of excess lipids in serum in comparison to WT mice.

Fecal microbiota transplantation from Suncus murinus, an obesity-resistant animal, to C57BL/6NCrSIc mice, and the antibiotic effects in the approach.

Introduction: Important studies on the relationship of the intestinal microbial flora with obesity have uncovered profound changes in the composition of the gut microbiota in obese individuals. Animal studies successfully altered body phenotypes by fecal microbiota transplantation (FMT). Methods: In this study, we analyzed the gut microbiome of Suncus murinus (S. murinus), a naturally obesity-resistant animal, and the changes of the gut flora of C57BL/6NCrSIc mice that received gut bacteria transplantation from S. murinus by 16S rRNA gene analysis method. And analyzed and discussed the possible impact of the use of antibiotics before transplantation on the outcome of transplantation. Results: Our results showed no significant changes in body weight in the FMT group compared to the control (AB) group, but large fluctuations due to antibiotics. There was no change in blood lipid levels between groups before and after FMT. The gut microbiota of S. murinus were enriched in Firmicutes and Proteobacteria, while Bacteroidetes were not detected, and fewer OTUs were detected in the intestine gut in comparison to other mouse groups. Statistically significant differences in alpha diversity were observed between the FMT group and other groups. Furthermore, a beta diversity analysis indicated an apparent structural separation between the FMT group and other groups. Conclusion: It was suggested that the gut flora of S. murinus was not well established in the gut trace of mice through FMT, and the administration of antibiotics before transplantation was an important factor affecting the overall composition of the gut flora. Although FMT of S. murinus failed to completely colonize the intestinal tract of the mice, it still had a certain effect on the establishment of the intestinal flora of the mice. The unpredictable effects of pre-transplantation antibiotics on the results of transplantation cannot be ignored.

Mice with asthma are more resistant to influenza virus infection and NK cells activated by the induction of asthma have potentially protective effects.

PURPOSE: This study was conducted in order to investigate whether the virulence of the influenza virus infection is affected by asthma in mice. METHODS: Mice with asthma or control mice were infected with influenza virus. The survival rate, body weight, virus titer, cytokine profile, and cell infiltration in bronchoalveolar lavage fluid (BALF) were measured. The NK cell cytotoxicity was determined by a co-culture system with YAC-1 cells, and the effects of NK cells were observed by depletion of NK cells using anti-asialoGM1 serum. The virus-specific CD8(+) T cell killing assay was also performed. RESULTS: When asthmatic or control mice were infected with non- and sub-lethal doses of influenza virus, the asthmatic mice were more resistant to the virus than control mice with regard to the survival rate, the remission of body weight loss, and the virus burden. Anti-viral cytokines and the NK cell number were increased in the BALF of asthmatic mice before the infection. The NK cell cytotoxicity in the asthmatic mice was significantly enhanced compared to that in control mice, and the depletion of NK cells in asthmatic mice was abrogated both the improved survival rate and the recovery of the body weight loss. The antigen-specific CD8(+) T cell killing activity in asthmatic mice was also significantly increased following the infection compared to that in control mice. CONCLUSION: NK cell activated by the induction of asthma and the subsequently activated antigen-specific CD8(+) T cells could promptly eliminate the viral-infected cells, thus leading to improvements in the morbidity and mortality of influenza virus infection.

Genomic and pathogenic characterization of RTX toxin producing Rodentibacter sp. that is closely related to Rodentibacter haemolyticus.

Rodentibacter spp. are opportunistic pathogens that are often isolated from the upper respiratory tracts of laboratory rodents. In particular, R. pneumotropicus and R. heylii require considerable caution in rodent colonies, as they cause lethal pneumonia in rodents. A new species, R. haemolyticus, has recently been classified in the genus, and a very closely related strain, Rodentibacter sp. strain JRC, has been isolated in Japan. This study focused on strain JRC by performing genomic and pathogenic analyses. Draft genome sequencing of strain JRC identified several genes coding for putative virulent proteins, including hemolysin and adhesin. Furthermore, we found a new RTX (repeats-in-structural toxin) toxin gene in the genome, which was predicted to produce a critical virulence factor (RTXIA) similar to Enterobacteriaceae. The concentrated culture supernatant containing RTX toxin (RTXIA) showed cytotoxicity toward RAW264.7 cells. Pre-incubation with anti-CD11a attenuated the cytolysis, suggesting that the concentrated culture supernatant containing RTXIA is cell surface LFA-1 mediated cytolysin. Experimental infection of strain JRC intranasally with 5 female BALB/c-Rag2-/- mice showed 60% lethality and was not significantly different from those of R. pneumotropicus ATCC 35149T using the log-rank test. Combined with our finding that RTXIA has an almost identical amino acid sequence (98% identity) to that of R. haemolyticus 1625/19T, these results strongly suggest that RTXIA-producing strain JRC (and related R. haemolyticus) is pathogenic to immunodeficient rodents, and both agents should be excluded in laboratory rodent colonies.

Molecular and virulence characteristics of an outer membrane-associated RTX exoprotein in Pasteurella pneumotropica.

BACKGROUND: Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Currently two RTX toxins, PnxIA and PnxIIA, which are similar to hemolysin-like high-molecular-weight exoproteins are known in this species. In this study, we identified and analyzed a further RTX toxin named PnxIIIA and the corresponding type I secretion system. RESULTS: The RTX exoprotein, PnxIIIA, contains only a few copies of the RTX repeat-like sequence and 3 large repeat sequences that are partially similar to the outer membrane protein found in several prokaryotes. Recombinant PnxIIIA protein (rPnxIIIA) was cytotoxic toward J774A.1 mouse macrophage cells, whereas cytotoxicity was attenuated by the addition of anti-CD11a monoclonal antibody. rPnxIIIA could bind to extracellular matrices (ECMs) and cause hemagglutination of sheep erythrocytes. Binding was dependent on the 3 large repeat sequences in PnxIIIA. Protein interaction analyses indicated that PnxIIIA is mainly localized in the outer membrane of P. pneumotropica ATCC 35149 in a self-assembled oligomeric form. PnxIIIA is less cytotoxic to J774A.1 cells than PnxIA and PnxIIA. CONCLUSIONS: The results implicate that PnxIIIA is located on the cell surface and participates in adhesion to ECMs and enhanced hemagglutination in the rodent pathogen P. pneumotropica.

Seroprevalence of anti-mumps virus IgG antibody titer and voluntary mumps vaccination coverage in young adults in Japan.

In Japan, monovalent vaccine against mumps virus (MuV) infection was shifted to a voluntary basis vaccination due to the incidences of aseptic meningitis in the past. According to an analysis of a total of 409 participants aged 18-20 years, overall vaccination coverage rate was 48%. The mean anti-MuV IgG antibody titer of participants with medical history and more than two times vaccination was significantly higher than that in those without a medical history and unvaccinated and single vaccination, respectively. Seropositivity against MuV infection was >50% regardless of the number of vaccinations. Although these results suggest that seropositivity may persist due to asymptomatic infection, it is necessary to implement either a high vaccine coverage or routine vaccination for prevention of periodic mumps epidemics.

Persistence of Anti-Rubella Immunoglobulin G Antibody Titers in Young Adults Involved in a Short-Term Periodic Immunization in Japan.

In Japan, several rubella outbreaks in adults have erupted due to insufficient immunity against rubella virus (RUBV). Although selective immunization is being promoted along with routine rubella vaccination as its eradication strategy, serosurveillance against RUBV needs to be implemented in the generations corresponding to the vaccination transition period. In this study, a survey of anti-rubella immunoglobulin G (IgG) antibody titers was conducted among young adults involved in the transitional periods of the routine rubella vaccination program. Specifically, serosurveillance was performed in 370 healthy young adults aged 18-20 years, wherein their serum samples were analyzed using an enzyme immunoassay to determine rubella-specific IgG antibody titers. Although multiple regression analysis revealed significant differences only in medical history, more than 90% of participants exhibited seropositivity, excluding those who received a single-dose vaccine alone. Based on elapsed periods after the last vaccination, rubella-specific IgG antibody titers in less than a 6-year period were higher than those in more than a 10-year period. Although almost all study participants in the transitional period had seropositivity, the results may indicate that this persistence is related to past rubella outbreaks.

Penicillin-Binding Proteins and Associated Protein Mutations Confer Oxacillin/Cefoxitin Tolerance in Borderline Oxacillin-Resistant Staphylococcus aureus.

Among clinical isolates of Staphylococcus aureus, borderline oxacillin-resistant S. aureus (BORSA), which is mildly resistant to oxacillin (OXA) without harboring the mecA or mecC gene, is considered a risk factor for further resistance against multiple antibiotics. In this study, BORSA isolates and their derivatives were characterized through antibiotic susceptibility testing and mutation analysis of the genes encoding penicillin-binding proteins (PBPs) and their related proteins, including the promoter region. Eight BORSA isolates were confirmed to harbor the blaZ gene, and hyperproduction of blaZ-encoded penicillinase was predicted based on the minimum inhibitory concentrations (MICs). Of these, four derivative strains that were spontaneously selected based on viability on media containing high concentrations of OXA showed higher MICs than the parent isolates. The minimum bactericidal concentrations, MIC ratios, and TDtest results identified many strains with cefoxitin tolerance. Sequencing of pbp1, pbp2, pbp3, pbp4, gdpP, and yjbH, and the promoter of pbp4 revealed mutations in BORSA isolates and derivatives, despite their absence in parent isolates, suggesting that mutations in PBPs confer OXA/cefoxitin tolerance in BORSA strains.

Prevalence and analysis of Pseudomonas aeruginosa in chinchillas.

BACKGROUND: Chinchillas (Chinchilla laniger) are popular as pets and are often used as laboratory animals for various studies. Pseudomonas aeruginosa is a major infectious agent that causes otitis media, pneumonia, septicaemia enteritis, and sudden death in chinchillas. This bacterium is also a leading cause of nosocomial infections in humans. To prevent propagation of P. aeruginosa infection among humans and animals, detailed characteristics of the isolates, including antibiotic susceptibility and genetic features, are needed. In this study, we surveyed P. aeruginosa distribution in chinchillas bred as pets or laboratory animals. We also characterized the isolates from these chinchillas by testing for antibiotic susceptibility and by gene analysis. RESULTS: P. aeruginosa was isolated from 41.8% of the 67 chinchillas included in the study. Slide agglutination and pulsed-field gel electrophoresis discriminated 5 serotypes and 7 unique patterns, respectively. For the antibiotic susceptibility test, 40.9% of isolates were susceptible to gentamicin, 77.3% to ciprofloxacin, 77.3% to imipenem, and 72.7% to ceftazidime. DNA analyses confirmed that none of the isolates contained the gene encoding extended-spectrum ß-lactamases; however, 2 of the total 23 isolates were found to have a gene similar to the pilL gene that has been identified in the pathogenicity island of a clinical isolate of P. aeruginosa. CONCLUSIONS: P. aeruginosa is widely spread in chinchillas, including strains with reduced susceptibility to the antibiotics and highly virulent strains. The periodic monitoring should be performed to help prevent the propagation of this pathogen and reduce the risk of infection from chinchillas to humans.

NKT cells are responsible for the clearance of murine norovirus through the virus-specific secretory IgA pathway.

Norovirus infection cause epidemic nonbacterial gastroenteritis in patients. The immune mechanisms responsible for the clearance of virus are not completely understood. We examined whether NKT cells are effective against norovirus infection using CD1d KO mice. The body weights of 4-weeks-old CD1d KO mice that were infected with murine norovirus-S7 (MNV-S7) were significantly lower than those of non-infected CD1d KO mice. On the other hand, the body weights of infected WT mice were comparable to those of non-infected WT mice. Correspondingly, CD1d KO mice had an almost 1000-fold higher MNV-S7 burden in the intestine after infection in comparison to WT mice. The mechanism responsible for the insufficient MNV-S7 clearance in CD1d KO mice was attributed to reduced IFN-γ production early during MNV-S7 infection. In addition, the markedly impaired IL-4 production in CD1d KO mice resulted in an impaired MNV-S7-specific secretory IgA production after MNV-S7 infection which is associated with mucosal immunity. Thus, the present results provide evidence that NKT cells play an essential role in MNV-S7 clearance.

Identification and characterization of hemolysin-like proteins similar to RTX toxin in Pasteurella pneumotropica.

Pasteurella pneumotropica is an opportunistic pathogen that causes lethal pneumonia in immunodeficient rodents. The virulence factors of this bacterium remain unknown. In this study, we identified the genes encoding two RTX toxins, designated as pnxI and pnxII, from the genomic DNA of P. pneumotropica ATCC 35149 and characterized with respect to hemolysis. The pnxI operon was organized according to the manner in which the genes encoded the structural RTX toxin (pnxIA), the type I secretion systems (pnxIB and pnxID), and the unknown orf. The pnxII gene was involved only with the pnxIIA that coded for a structural RTX toxin. Both the structural RTX toxins of deduced PnxIA and PnxIIA were involved in seven of the RTX repeat and repeat-like sequences. By quantitative PCR analysis of the structural RTX toxin-encoding genes in P. pneumotropica ATCC 35149, the gene expression of pnxIA was found to have increased from the early log phase, while that of pnxIIA increased from the late log to the early stationary phase. As expressed in Escherichia coli, both the recombinant proteins of PnxIA and PnxIIA showed weak hemolytic activity in both sheep and murine erythrocytes. On the basis of the results of the Southern blotting analysis, the pnxIA gene was detected in 82% of the isolates, while the pnxIIA gene was detected in 39%. These results indicate that the products of both pnxIA and pnxIIA were putative associations of virulence factors in the rodent pathogen P. pneumotropica.

Comparative analysis of Pasteurella pneumotropica isolates from laboratory mice and rats.

Selected biochemical and genetic characteristics of the wild-type strains of Pasteurella pneumotropica isolated from mice and rats were investigated and compared in order to determine the significant differences among the isolates. The isolates were divided into six groups on the basis of the patterns of carbon source utilization in the host rodents. The genome sizes were determined by electrophoretic analysis, and the mean genome size of the isolates from mice was larger than that of the isolates from rats (P < 0.05). Cluster analysis of the rpoB sequences discriminated five clusters; the differences might have correlated with the host associations. Principal component analysis (PCA) based on both the biochemical and genetic characteristics revealed total 44 strains discriminated into three groups comprising the host-dependent and host-independent groups. Although the P. pneumotropica isolates were mainly classified on the basis of the host rodents by the examinations, the existence of isolates that could not be discriminated on the basis of the host rodents alone was confirmed by the PCA. These results indicated that the P. pneumotropica isolates could be further classified by taxonomic analysis and also suggested the existence of a host-independent group in addition to the host-dependent groups.

A Survey of Vaccine-Induced Measles IgG Antibody Titer to Verify Temporal Changes in Response to Measles Vaccination in Young Adults.

In Japan, sporadic measles cases increased rapidly in 2019 compared to the past six years. To clarify the persistence of immunity against measles in young adults, this study explored the persistence of immunoglobulin G (IgG) antibody titers against the measles virus in 17- to 24-year-old young participants who reside in the Chiba prefecture of Japan. Measles-specific IgG antibody titers, determined by enzyme immunoassay in serum samples collected from 506 participants, were assessed through statistical analyses. Multivariable regression analysis revealed that the distribution of measles IgG antibody titers was significantly correlated with a medical history of measles (P < 0.05), while there was no significant correlation between the number of vaccinations related to measles IgG titers. Furthermore, measles IgG titers tended to decrease, as revealed by the temporal change in IgG titers, during the elapsed period after the last vaccination (P = 0.08). These results indicate that periodic vaccination against measles is required to prevent sporadic measles infection in young and older adults.

Investigation of the microbial community in a microbiological additive used in a manure composting process.

The objectives of this study were to investigate the fate of microorganisms by using cultivation methods as well as DNA analyses in a commercial microbiological additive (MA) in the course of the composting. Almost all the predominant species in the microbial succession during composting process determined by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) were in disagreement with those determined by the clone library method. None of the microbial species in the composting stages corresponded to the microorganisms identified in the MA either by the cultivation method or DNA analysis. The results in regard to predominant microorganisms of the MA detected from the liquid medium by the PCR-DGGE did not correspond with those detected from the MA itself and composting processes. Although no evidence was found that predominant species in the MA itself dominate in the composting process, predominant species diversity in the MA itself was markedly changed after culturing at different thermophilic temperatures. These results suggested that cultivable microorganisms in the MA did not become predominant in the composting process: however, some microorganisms that are detected from the MA itself by the DNA analysis may act effectively in the composting process.

Comparison of the in vitro susceptibility of rodent isolates of Pseudomonas aeruginosa and Pasteurella pneumotropica to enrofloxacin.

The objectives of this study were to determine and compare the in vitro enrofloxacin susceptibility of 94 Pseudomonas aeruginosa isolates obtained from enrofloxacin-treated and untreated mice and that of 40 Pasteurella pneumotropica strains and also to assess the efficacy and effects of enrofloxacin treatment of laboratory mice. The minimum inhibitory concentrations (MICs) of enrofloxacin against all the Ps. aeruginosa isolates were in the range of 1 to 4 microg/ml, whereas those against all the P. pneumotropica strains were less than 0.5 microg/ml. The mutation frequency in 54% of the Ps. aeruginosa isolates on treatment with enrofloxacin ranged from 10(-6) to 10(-8); however, none of the P. pneumotropica strains could grow on medium containing more than 3 microg/ml enrofloxacin. Comparison of in vitro enrofloxacin susceptibilities suggested that enrofloxacin was effective for eliminating P. pneumotropica but not for eliminating Ps. aeruginosa for which the MIC of enrofloxacin was more than 1 microg/ml. These results indicated that the enrofloxacin susceptibility of P. pneumotropica was higher than that of Ps. aeruginosa, and that the enrofloxacin treatment might not affect the susceptibility of Ps. aeruginosa.

Phylogenetic relationship of Pasteurella pneumotropica isolates from laboratory rodents based on 16S rDNA sequence.

A 1344 bp fragment of the 16S ribosomal DNA (rDNA) sequence was used to determine the genetic relationship of Pasteurella pneumotropica isolates from laboratory rodents. A total of 30 nucleotide sequences of P. pneumotropica, including 24 wild strains, 3 reference strains, and 3 nucleotide sequences deposited in GenBank, were examined for heterogeneity of their 16S rDNA sequences. Phylogenetic analysis based on 16S rDNA sequence discriminated 5 types of branching lineages. Of these 5 types, 3 types had significant associations with mice or rats, and 2 had significant associations with the beta-hemolytic phenotype. These results suggest that 16S rDNA sequencing of P. pneumotropica isolates demonstrates genetic heterogeneity and phylogenetic discrimination in terms of their hemolytic phenotype and host associations.