Nasal Delivery of Haemophilus haemolyticus Is Safe, Reduces Influenza Severity, and Prevents Development of Otitis Media in Mice

BACKGROUND

Despite vaccination, influenza and otitis media (OM) remain leading causes of illness. We previously found that the human respiratory commensal Haemophilus haemolyticus prevents bacterial infection in vitro and that the related murine commensal Muribacter muris delays OM development in mice. The observation that M muris pretreatment reduced lung influenza titer and inflammation suggests that these bacteria could be exploited for protection against influenza/OM.

METHODS

Safety and efficacy of intranasal H haemolyticus at 5 × 107 colony-forming units (CFU) was tested in female BALB/cARC mice using an influenza model and influenza-driven nontypeable Haemophilus influenzae (NTHi) OM model. Weight, symptoms, viral/bacterial levels, and immune responses were measured.

RESULTS

Intranasal delivery of H haemolyticus was safe and reduced severity of influenza, with quicker recovery, reduced inflammation, and lower lung influenza virus titers (up to 8-fold decrease vs placebo; P ≤ .01). Haemophilus haemolyticus reduced NTHi colonization density (day 5 median NTHi CFU/mL = 1.79 × 103 in treatment group vs 4.04 × 104 in placebo, P = .041; day 7 median NTHi CFU/mL = 28.18 vs 1.03 × 104; P = .028) and prevented OM (17% OM in treatment group, 83% in placebo group; P = .015).

CONCLUSIONS

Haemophilus haemolyticus has potential as a live biotherapeutic for prevention or early treatment of influenza and influenza-driven NTHi OM. Additional studies will deem whether these findings translate to humans and other respiratory infections.

Skin microbiota of oxazolone-induced contact hypersensitivity mouse model

Contact allergy is a common skin allergy, which can be studied utilising contact hypersensitivity (CHS) animal model. However, it is not clear, whether CHS is a suitable model to investigate skin microbiota interactions. We characterised the effect of contact dermatitis on the skin microbiota and studied the biological effects of oxazolone (OXA) -induced inflammation on skin thickness, immune cell numbers and changes of the microbiota in CHS mouse model (n = 72) for 28 days. Through 16S rRNA gene sequencing we defined the composition of bacterial communities and associations of bacteria with inflammation. We observed that the vehicle solution of acetone and olive oil induced bacterial community changes on day 1, and OXA-induced changes were observed mainly on day 7. Many of the notably enriched bacteria present in the OXA-challenged positive group represented the genus Faecalibaculum which were most likely derived from the cage environment. Additionally, skin inflammation correlated negatively with Streptococcus, which is considered a native skin bacterium, and positively with Muribacter muris, which is typical in oral environment. Skin inflammation favoured colonisation of cage-derived faecal bacteria, and additionally mouse grooming transferred oral bacteria on the skin. Due to the observed changes, we conclude that CHS model could be used for certain skin microbiome-related research set-ups. However, since vehicle exposure can alter the skin microbiome as such, future studies should include considerations such as careful control sampling and statistical tests to account for potential confounding factors.

Lactobacillus Modulates Chlamydia Infectivity and Genital Tract Pathology in vitro and in vivo

Since we previously reported that women infected with chlamydia had a significant overall reduction in Lactobacillus in the vagina microbiota as compared to those uninfected individuals; the interactions between the altered Lactobacillus and Chlamydia trachomatis, on the other hand, need to be elucidated. Here, we employed both in vitro and in vivo models to evaluate the effects of this changed Lactobacillus on Chlamydia infection. We found that L. iners, L. crispatus, L. jensenii, L. salivarius, L. gasseri, L. mucosae, and L. reuteri all significantly reduced C. trachomatis infection in a dose- and time-dependent manner. The strongest anti-Chlamydia effects were found in L. crispatus (90 percent reduction), whereas the poorest was found in L. iners (50 percent reduction). D (–) lactic acid was the key component in Lactobacillus cell-free supernatants (CFS) to inactivate Chlamydia EBs, showing a positive correlation with the anti-Chlamydia activity. The effects of D (–) lactic acid were substantially attenuated by neutralizing the pH value to 7.0. In vivo, mice intravaginally inoculated with Lactobacillus mixtures (L. crispatus, L. reuteri, and L. iners at a ratio of 1:1:1), but not single Lactobacillus, after genital Chlamydia infection, significantly attenuated the levels of Chlamydia live organism shedding in both the lower genital tract and the intestinal tract, reduced cytokines production (TNF-α, IFN-γ, and IL-1β) in the vagina, and lessened upper genital tract inflammation and pathogenicity. Taken together, these data demonstrate that Lactobacillus inhibits Chlamydia infectivity both in vivo and in vitro, providing useful information for the development of Lactobacillus as adjunctive treatment in Chlamydia infection.

Actinobacillus utilizes a binding protein-dependent ABC transporter to acquire the active form of vitamin B6

Bacteria require high-efficiency uptake systems to survive and proliferate in nutrient-limiting environments, such as those found in host organisms. ABC transporters in the bacterial plasma membrane provide a mechanism for transport of many substrates. In this study, we examine an operon containing a periplasmic binding protein in Actinobacillus for its potential role in nutrient acquisition. The electron density map of 1.76 Å resolution obtained from the crystal structure of the periplasmic binding protein was best fit with a molecular model containing a pyridoxal-5'-phosphate (P5P/pyridoxal phosphate/the active form of vitamin B6) ligand within the protein's binding site. The identity of the P5P bound to this periplasmic binding protein was verified by isothermal titration calorimetry, microscale thermophoresis, and mass spectrometry, leading us to name the protein P5PA and the operon P5PAB. To illustrate the functional utility of this uptake system, we introduced the P5PAB operon from Actinobacillus pleuropneumoniae into an Escherichia coli K-12 strain that was devoid of a key enzyme required for P5P synthesis. The growth of this strain at low levels of P5P supports the functional role of this operon in P5P uptake. This is the first report of a dedicated P5P bacterial uptake system, but through bioinformatics, we discovered homologs mainly within pathogenic representatives of the Pasteurellaceae family, suggesting that this operon exists more widely outside the Actinobacillus genus.

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.

Early-life malnutrition causes gastrointestinal dysmotility that is sexually dimorphic

BACKGROUND

Slow gastrointestinal (GI) transit occurs in moderate-to-severe malnutrition. Mechanisms underlying malnutrition-associated dysmotility remain unknown, partially due to lack of animal models. This study sought to characterize GI dysmotility in mouse models of malnutrition.

METHODS

Neonatal mice were malnourished by timed maternal separation. Alternatively, low-protein, low-fat diet was administered to dams, with malnourished neonates tested at two weeks or weaned to the same chow and tested as young adults. We determined total GI transit time by carmine red gavage, colonic motility by rectal bead latency, and both gastric emptying and small bowel motility with fluorescein isothiocyanate-conjugated dextran. We assessed histology with light microscopy, ex vivo contractility and permeability with force-transduction and Ussing chamber studies, and gut microbiota composition by 16S rDNA sequencing.

KEY RESULTS

Both models of neonatal malnutrition and young adult malnourished males but not females exhibited moderate growth faltering, stunting, and grossly abnormal stomachs. Progression of fluorescent dye was impaired in both neonatal models of malnutrition, whereas gastric emptying was delayed only in maternally separated pups and malnourished young adult females. Malnourished young adult males but not females had atrophic GI mucosa, exaggerated intestinal contractile responses, and increased gut barrier permeability. These sex-specific abnormalities were associated with altered gut microbial communities.

CONCLUSIONS & INFERENCES

Multiple models of early-life malnutrition exhibit delayed upper GI transit. Malnutrition affects young adult males more profoundly than females. These models will facilitate future studies to identify mechanisms underlying malnutrition-induced pathophysiology and sex-specific regulatory effects.

Nasal Delivery of a Commensal Pasteurellaceae Species Inhibits Nontypeable Haemophilus influenzae Colonization and Delays Onset of Otitis Media in Mice

Nasopharyngeal colonization with nontypeable Haemophilus influenzae (NTHi) is a prerequisite for developing NTHi-associated infections, including otitis media. Therapies that block NTHi colonization may prevent disease development. We previously demonstrated that Haemophilus haemolyticus, a closely related human commensal, can inhibit NTHi colonization and infection of human respiratory epithelium in vitro. We have now assessed whether Muribacter muris (a rodent commensal from the same family) can prevent NTHi colonization and disease in vivo using a murine NTHi otitis media model.

Nasopharyngeal colonization with nontypeable Haemophilus influenzae (NTHi) is a prerequisite for developing NTHi-associated infections, including otitis media. Therapies that block NTHi colonization may prevent disease development. We previously demonstrated that Haemophilus haemolyticus, a closely related human commensal, can inhibit NTHi colonization and infection of human respiratory epithelium in vitro. We have now assessed whether Muribacter muris (a rodent commensal from the same family) can prevent NTHi colonization and disease in vivo using a murine NTHi otitis media model. Otitis media was modeled in BALB/c mice using coinfection with 1 × 10^4.5 PFU of influenza A virus MEM H3N2, followed by intranasal challenge with 5 × 10⁷ CFU of NTHi R2866 Spec^r. Mice were pretreated or not with an intranasal inoculation of 5 × 10⁷ CFU M. muris 24 h before coinfection. NTHi and M. muris viable counts and inflammatory mediators (gamma interferon [IFN-γ], interleukin-1β [IL-1β], IL-6, keratinocyte chemoattractant [KC], and IL-10) were measured in nasal washes and middle ear tissue homogenate. M. muris pretreatment decreased the median colonization density of NTHi from 6 × 10⁵ CFU/ml to 9 × 10³ CFU/ml (P = 0.0004). Only 1/12 M. muris-pretreated mice developed otitis media on day 5 compared to 8/15 mice with no pretreatment (8% versus 53%, P = 0.0192). Inflammation, clinical score, and weight loss were also lower in M. muris-pretreated mice. We have demonstrated that a single dose of a closely related commensal can delay onset of NTHi otitis media in vivo. Human challenge studies investigating prevention of NTHi colonization are warranted to reduce the global burden of otitis media and other NTHi diseases.

Phylogenomic analysis of Haemophilus parasuis and proposed reclassification to Glaesserella parasuis, gen. nov., comb. nov

The Gram-negative bacterium Haemophilus parasuis is the etiologic agent of Glässer's disease in pigs, and causes significant economic losses to the swine industry. This bacterium has been classified as a member of the family Pasteurellaceae in the genus Haemophilus, but phylogenetic relatedness has not been adequately examined to support this genus classification. Phenotypically, all 38 strains of H. parasuis tested were positive for catalase activity, oxidase activity, V-factor requirement, and acid formation from maltose and d-galactose without gas. All strains were negative for X-factor requirement, formation of indole from tryptophan, urease, l-arabinose, and α-glucosidase activity. To determine whether H. parasuis belongs to one of the current Pasteurellaceae genera 40 H. parasuis genomes, plus those of representative Pasteurellaceae, were subjected to phylogenetic analysis of concatenated, multi-protein alignments. Sequence variation at 16S rRNA and rpoB loci allowed the 15 reference serovars of H. parasuis to be integrated into the whole-genome tree. The phylogenetic analysis showed H. parasuis to be a distinct and tight clade whose sister taxon is the genus Bibersteinia. Within H. parasuis two clades were identified with individual serovars distributed between the two. As a result, H. parasuis was confirmed as a member of the family Pasteurellaceae, but was distinct from other genera in this family. Therefore, we propose the name Glaesserella parasuis, gen. nov., comb. nov. for bacterial strains currently classified as H. parasuis. The reference strain of this species is ATCC 19417 (1374)^T, NCTC 4557^T, DSM 21448^T, CCUG 3712^T.

Differentiation of Rodentibacter pneumotropicus, Rodentibacter heylii and Muribacter muris by MALDI-TOF MS

The pathogens Rodentibacter (R.) pneumotropicus and R. heylii as well as the commensal Muribacter (M.) muris are frequently isolated in mice. In this study, a MALDI-TOF MS database was extended with spectra of well characterized strains of these species. Compared to a multiplex PCR, all examined out-of-sample isolates were correctly identified.

Actinobacillus vicugnae sp. nov., isolated from alpaca (Vicugna pacos)

Ten strains of an Actinobacillus-like organism were isolated from alpaca (Vicugna pacos) in the UK over a period of 5 years, with no known epidemiological linkages. The isolates are distinct, based on both phenotype and genotype, from any previously described Actinobacillus species. Molecular analysis, based on 16S rRNA, rpoB and infB gene sequences, placed the isolates as a novel, early branching, lineage within the currently recognised Actinobacillus sensu stricto. In agreement with the results of the single-gene analysis, average nucleotide identity values, based on whole genome sequences, showed very similar identities to a number of members of the Actinobacillus sensu stricto notably Actinobacillus equuli, Actinobacillus suis and Actinobacillus ureae. At least two phenotypic characteristics differentiate the alpaca isolates from other Actinobacillus sensu stricto species, and from taxa likely falling within this group but awaiting formal species description, with Actinobacillus anseriformium and A. equulisubsp. haemolyticus being the most closely related phenotypically. The alpaca isolates can be differentiated from A. anseriformium by production of β-galactosidase (ONPG) and acid from raffinose, and from A. equulisubsp. haemolyticus by production of acid from d-sorbitol and failure to produce acid from d-xylose. Isolates were obtained from multiple sites in alpaca including respiratory tract, alimentary tract and internal organs although further evidence is required to understand any pathogenic significance. Based on the results of characterization described here, it is proposed that the isolates constitute a novel species, Actinobacillus vicugnae sp. nov. The type strain is W1618^T (LMG30745^T NCTC14090^T) isolated in the UK in 2012 from oesophageal ulceration in an alpaca (Vicugna pacos).

Identification of Lonepinella sp. in Koala Bite Wound Infections, Queensland, Australia

We report 3 cases of koala bite wound infection with Lonepinella koalarum–like bacteria requiring antimicrobial and surgical management. The pathogens could not be identified by standard tests. Phylogenetic analysis of 16S rRNA and housekeeping genes identified the genus. Clinicians should isolate bacteria and determine antimicrobial susceptibilities when managing these infections.

The Likelihood of Misidentifying Rodent Pasteurellaceae by Using Results from a Single PCR Assay

The precise identification of rodent Pasteurellaceae is known to be highly challenging. An unknown strain of Pasteurellaceae appeared and rapidly spread throughout our animal facilities. Standard microbiology, combined with biochemical analysis, suggested that the bacteria strain was Rodentibacter pneumotropicus or R. heylii. We submitted samples of the unknown bacteria and known isolates of R. pneumotropicus, R. heylii, and Muribacter muris, to 2 service laboratories that provide animal health monitoring. Results of microbiology tests performed by both laboratories, species-specific PCR analysis performed by one laboratory, and independent 16S rRNA gene sequencing yielded identical identification of the unknown bacteria as Pasteurellaceae (Pasteurella spp.) and not R. pneumotropicus or R. heylii. In contrast, the similarly intended PCR assay performed by the other laboratory identified the bacteria as R. heylii. Careful evaluation of all of the results led us to conclude that the correct identification of the bacteria is Pasteurellaceae. From our experience, we recommend that a combination of several methods should be used to achieve correct identification of rodent Pasteurellaceae. Specifically, we advise that all primer sets used should be disclosed when reporting PCR test results, including in health reports provided by service laboratories and animal vendors. Careful, correct, and informative health monitoring reports are most beneficial to animal researchers and caretakers who might encounter the presence and effects of rodent Pasteurellaceae.

Revised taxonomy and nomenclature of rodent Pasteurellaceae: Implications for monitoring

Pasteurellosis is a well-recognized disease with similar pathology in all laboratory rodent species. Pasteurella pneumotropica is the most frequently mentioned member of the Pasteurellaceae isolated from mice and rats. Numerous other Pasteurellaceae taxa have been obtained from mice, rats, and other rodent species. Recently, rodent Pasteurellaceae have been submitted to comprehensive genetic and phenotypic (polyphasic) taxonomic studies. As a result they are now classed within six validly published new genera, namely Cricetibacter, Mesocricetibacter, Mannheimia, Muribacter, Necropsobacter, and Rodentibacter. All previously used names such as P. pneumotropica have become obsolete. The new classification forms a firm basis for the correct phenotypic identification of Pasteurellaceae from laboratory animals and for the selection of strains for pathogenicity studies. Consequences of taxonomic changes notably involve molecular methods used for the detection of Pasteurellaceae infection in laboratory animal colonies. Testing may be done using primer sets that detect all Pasteurellaceae taxa or sets developed to detect host-specific members of the family.

Reclassification of Bisgaard taxon 5 as Caviibacterium pharyngocola gen. nov., sp. nov. and Bisgaard taxon 7 as Conservatibacter flavescens gen. nov., sp. nov

A total of 29 strains mainly from guinea pigs were investigated by a polyphasic approach that included previously published data. The strains were classified as Bisgaard taxa 5 and 7 by comparison of phenotypic characteristics and the strains showed typical cultural characteristics for members of family Pasteurellaceae and the strains formed two monophyletic groups based on 16S rRNA gene sequence comparison. Partial rpoB sequence analysis as well as published data on DNA-DNA hybridization showed high genotypic relationships within both groups. A new genus with one species, Caviibacterium pharyngocola gen. nov., sp. nov., is proposed to accommodate members of taxon 5 of Bisgaard, whereas members of taxon 7 are proposed as Conservatibacter flavescens gen. nov., sp. nov. The two genera are clearly separated by phenotype from each other and from existing genera of the family Pasteurellaceae. The type strain of Caviibacterium pharyngocola is 7.3^T (=CCUG 16493^T=DSM 105478^T) and the type strain of Conservatibacter flavescens is 7.4^T (=CCUG 24852^T=DSM 105479^T=HIM 794-7^T), both were isolated from the pharynx of guinea pigs.