Common Commensal Bacteria Research Articles

Opportunistic Features of Non-Clostridium botulinum Strains Containing bont Gene Cluster.

The cluster of genes determining the production of botulinum toxins is an attribute of not only the Clostridium botulinum species. This cluster is also found in other members of the Clostridium genus, such as C. baratii, C. butyricum, and C. sporogenes. The occurrence of a botulinum-like cluster has also been recorded in strains of other genera, i.e., Enterococcus faecium, as well as in a Gram-negative species isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. It can be said that the mentioned species have a dual nature. Another species with a dual nature is C. butyricum. This bacterium is a common human and animal gut commensal bacterium and is also frequently found in the environment. Although non-toxigenic strains are currently used as probiotics in Asia, other strains have been implicated in pathological conditions, such as botulism in infants or necrotizing enterocolitis in preterm neonates. Additionally, C. baratii strains are rare opportunistic pathogens associated with botulism intoxication. They have been isolated from food and soil and can be carried asymptomatically or cause botulism outbreaks in animals and humans. In addition to the mentioned clostridia, the other microorganisms considered as non-toxigenic have also been suspected of carrying botulinum cluster Gram-negative bacteria, such as Chryseobacterium piperi isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. Additionally, Enterococcus faecium strains have been discovered carrying BoNT-related clusters (BoNT/En). Literature data regarding the heterogeneity of BoNT-producing strains indicate the requirement to reclassify C. botulinum species and other microorganisms able to produce BoNTs or possess botulinum-like gene clusters. This article aims to show the dual nature of Clostridium strains not belonging to the C. botulinum species that are sporadically able to carry bont clusters, which are usually considered saprophytic and even probiotic, and bont-like clusters in microorganisms from other genera. The aim was also to consider the genetic mechanisms of botulinum cluster expression in strains that are considered opportunistic and the microbiological safety aspects associated with their occurrence in the environment.

Metagenomic airborne resistome from urban hot spots through the One Health lens

AbstractHuman activities are a significant contributor to the spread of antibiotic resistance genes (ARGs), which pose a serious threat to human health. These ARGs can be transmitted through various pathways, including air, within the context of One Health. This study used metagenomics to monitor the resistomes in urban air from two critical locations: a wastewater treatment plant and a hospital, both indoor and outdoor. The presence of cell‐like structures was confirmed through fluorescence microscopy. The metagenomic analysis revealed a wide variety of ARGs and a high diversity of antibiotic‐resistant bacteria in the airborne particles collected. The wastewater treatment plant showed higher relative abundances with 32 ARG hits per Gb and m3, followed by the main entrance of the hospital (indoor) with ≈5 ARG hits per Gb and m3. The hospital entrance exhibited the highest ARG richness, with a total of 152 different ARGs classified into nine categories of antibiotic resistance. Common commensal and pathogenic bacteria carrying ARGs, such as Moraxella, Staphylococcus and Micrococcus, were detected in the indoor airborne particles of the hospital. Interestingly, no ARGs were shared among all the samples analysed, indicating a highly variable dynamic of airborne resistomes. Furthermore, the study found no ARGs in the airborne viral fractions analysed, suggesting that airborne viruses play a negligible role in the dissemination of ARGs.

Glaesserella parasuis serotype 5 induces pyroptosis via the RIG-I/MAVS/NLRP3 pathway in swine tracheal epithelial cells

Glaesserella parasuis (G. parasuis) is a common Gram-negative commensal bacterium in the upper respiratory tract of swine that can cause Glässer's disease under stress conditions. Pyroptosis is an important immune defence mechanism of the body that plays a crucial role in clearing pathogen infections and endogenous danger signals. This study aimed to investigate the mechanism of G. parasuis serotype 5 SQ (GPS5-SQ)-induced pyroptosis in swine tracheal epithelial cells (STECs). The results of the present study demonstrated that GPS5-SQ infection induces pyroptosis in STECs by enhancing the protein level of the N-terminal domain of gasdermin D (GSDMD-N) and activating the NOD-like receptor protein 3 (NLRP3) inflammasome. Furthermore, the levels of pyroptosis-related proteins, including GSDMD-N and cleaved caspase-1 were considerably decreased in STECs after the knockdown of retinoic acid inducible gene-I (RIG-I) and mitochondrial antiviral signaling protein (MAVS). These results indicated that GPS5-SQ might trigger pyroptosis through the activation of the RIG-I/MAVS/NLRP3 signaling pathway. More importantly, the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) repressed the activation of the RIG-I/MAVS/NLRP3 signaling and rescued the decrease in Occludin and zonula occludens-1 (ZO-1) after GPS5-SQ infection. Overall, our findings show that GPS5-SQ can activate RIG-I/MAVS/NLRP3 signaling and destroy the integrity of the epithelial barrier by inducing ROS generation in STECs, shedding new light on G. parasuis pathogenesis.

CCR2-dependent CX3CR1+ colonic macrophages promote Enterococcus faecalis dissemination.

Enterococci are common commensal bacteria that colonize the gastrointestinal tracts of most mammals, including humans. Importantly, these bacteria are one of the leading causes of nosocomial infections. This study examined the role of colonic macrophages in facilitating Enterococcus faecalis infections in mice. We determined that depletion of colonic phagocytes resulted in the reduction of E. faecalis dissemination to the gut-draining mesenteric lymph nodes. Furthermore, we established that trafficking of monocyte-derived CX3CR1-expressing macrophages contributed to E. faecalis dissemination in a manner that was not reliant on CCR7, the conventional receptor involved in lymphatic migration. Finally, we showed that E. faecalis mutants with impaired intracellular survival exhibited reduced dissemination, suggesting that E. faecalis can exploit host immune cell migration to disseminate systemically and cause disease. Our findings indicate that modulation of macrophage trafficking in the context of antibiotic therapy could serve as a novel approach for preventing or treating opportunistic infections by disseminating enteric pathobionts like E. faecalis.

Analysis of Antimicrobial Resistance in Bacterial Pathogens Recovered from Food and Human Sources: Insights from 639,087 Bacterial Whole-Genome Sequences in the NCBI Pathogen Detection Database.

Understanding the role of foods in the emergence and spread of antimicrobial resistance necessitates the initial documentation of antibiotic resistance genes within bacterial species found in foods. Here, the NCBI Pathogen Detection database was used to query antimicrobial resistance gene prevalence in foodborne and human clinical bacterial isolates. Of the 1,843,630 sequence entries, 639,087 (34.7%) were assigned to foodborne or human clinical sources with 147,788 (23.14%) from food and 427,614 (76.88%) from humans. The majority of foodborne isolates were either Salmonella (47.88%), Campylobacter (23.03%), Escherichia (11.79%), or Listeria (11.3%), and the remaining 6% belonged to 20 other genera. Most foodborne isolates were from meat/poultry (95,251 or 64.45%), followed by multi-product mixed food sources (29,892 or 20.23%) and fish/seafood (6503 or 4.4%); however, the most prominent isolation source varied depending on the genus/species. Resistance gene carriage also varied depending on isolation source and genus/species. Of note, Klebsiella pneumoniae and Enterobacter spp. carried larger proportions of the quinolone resistance gene qnrS and some clinically relevant beta-lactam resistance genes in comparison to Salmonella and Escherichia coli. The prevalence of mec in S. aureus did not significantly differ between meat/poultry and multi-product sources relative to clinical sources, whereas this resistance was rare in isolates from dairy sources. The proportion of biocide resistance in Bacillus and Escherichia was significantly higher in clinical isolates compared to many foodborne sources but significantly lower in clinical Listeria compared to foodborne Listeria. This work exposes the gaps in current publicly available sequence data repositories, which are largely composed of clinical isolates and are biased towards specific highly abundant pathogenic species. We also highlight the importance of requiring and curating metadata on sequence submission to not only ensure correct information and data interpretation but also foster efficient analysis, sharing, and collaboration. To effectively monitor resistance carriage in food production, additional work on sequencing and characterizing AMR carriage in common commensal foodborne bacteria is critical.

Genomic insights into virulence, antimicrobial resistance, and adaptation acumen of Escherichia coli isolated from an urban environment.

Evolutionary patterns of E. coli bacteria convey that they evolve into highly pathogenic forms by acquiring fitness advantages, such as AMR, and various virulence factors through the horizontal gene transfer (HGT)-mediated acquisition of MGEs. However, limited research on the genetic profiles of environmental E. coli, particularly from India, hinders our understanding of their transition to pathogenic forms and impedes the adoption of a comprehensive approach to address the connection between environmentally dwelling E. coli populations and human and veterinary public health. This study focuses on high-resolution genomic analysis of the environmental E. coli isolates aiming to understand the genetic similarities and differences among isolates from different environmental niches and uncover the survival strategies employed by these bacteria to thrive in their surroundings. Our approach involved molecular characterization of environmental samples using PCR-based DNA fingerprinting and subsequent WGS analysis. This multidisciplinary approach is likely to provide valuable insights into the understanding of any potential spill-over to human and animal populations and locales. Investigating these environmental isolates has significant potential for developing epidemiological strategies against transmission and understanding niche-specific evolutionary patterns.

Gut Microbiome Faecalibacterium Abundance in Patients with Plasma Cell Disorders Undergoing Autologous Hematopoietic Stem Cell Transplant Is Associated with Progression Free Survival

Background: Different aspects of the gut microbiota (GM), including diversity, abundance, and functionality, have been linked to the development, progression, response, and adverse events to therapy in plasma cell neoplasms (PCN). The primary goal of this study was to further investigate the relationship between the composition of the GM, focusing on the genus Faecalibacterium that contains the most common anaerobic commensal bacterium in the GM ( Faecalibacterium prausnitzii), and clinical outcomes of patients with PCN undergoing autologous hematopoietic stem cell transplant (HSCT). Methods: GM samples were collected prospectively between 2017 and 2021 at our institution as part of a phase III, randomized clinical trial including patients with malignant hematologic diseases undergoing either chemotherapy or transplant. Fecal samples were obtained at pre (baseline), mid (defined as at 1 week from baseline), and end (defined as at engraftment, absolute neutrophil count > 500 cells/mm 3) autologous HSCT and processed by 16S rDNA sequencing (V1-V3) using Illumina MiSeq to determine Faecalibacterium abundance at each prespecified time point. Progression free survival (PFS) and overall survival (OS) were computed via Kaplan-Meier estimate. Results: 83 evaluable patients underwent autologous HSCT for PCN, 54 (65%) as part of frontline therapy. 79 (95%) of the transplant recipients carried a diagnosis of Multiple Myeloma. Melphalan was used as the conditioning regimen, with 54 (65%) of the patients receiving a dose of 200 mg/m 2 (versus 140 mg/m 2). The median age of the patients was 64 (range, 31-79) years and 50 (60%) were men. With median time to follow up for survivors (n= 82, alive > 1 month post HSCT) of 32 (range, 0.7-61) months, the median PFS was 40 months and median OS was not reached. Faecalibacterium relative abundance was 3.5%, 1.7%, and 2% of the GM at pre, mid, and end transplant, respectively. Higher baseline Faecalibacterium abundance was significantly associated with superior PFS (n= 79) (HR= 0.92, p= 0.01) and OS (HR= 0.88, p= 0.008). Patients were partitioned into 2 groups, those with pre-transplant Faecalibacterium abundance above median and below median, to generate representative Kaplan-Meier curves for PFS (Figure 1). Greater reduction in Faecalibacterium abundance during transplant, and especially from pre to mid transplant, were significantly associated with worse PFS (n= 75) (HR= 1.08, p= 0.007; HR= 1.10, p= 0.004, respectively) and OS (HR= 1.09, p= 0.021; HR= 1.09, p= 0.04, respectively). There was no significant relationship between Faecalibacterium abundance and PFS at mid (n= 83) (HR= 1, p= 1), end (n= 83) (HR= 1.01, p= 0.7), or notably mid to end transplant (n= 75) (HR= 1, p= 0.9). Levels of the bacteria also did not associate with OS from mid to end transplant (n= 75) (HR 1.01, p= 0.8). Conclusions: Our study indicated that Faecalibacterium abundance in the GM changed rapidly early after autologous HSCT in patients with PCN likely due to melphalan administration. Higher baseline levels and smaller reduction in Faecalibacterium abundance predicted superior PFS. Further follow up with more mature data is needed to confirm OS associations. These findings support the need for further investigation into the role of GM and possible interventions to modify GM to improve outcomes to autologous transplant in patients with PCN.

Commensal Cutibacterium acnes induce epidermal lipid synthesis important for skin barrier function.

Lipid synthesis is necessary for formation of epithelial barriers and homeostasis with external microbes. An analysis of the response of human keratinocytes to several different commensal bacteria on the skin revealed that Cutibacterium acnes induced a large increase in essential lipids including triglycerides, ceramides, cholesterol, and free fatty acids. A similar response occurred in mouse epidermis and in human skin affected with acne. Further analysis showed that this increase in lipids was mediated by short-chain fatty acids produced by Cutibacterium acnes and was dependent on increased expression of several lipid synthesis genes including glycerol-3-phosphate-acyltransferase-3. Inhibition or RNA silencing of peroxisome proliferator-activated receptor-α (PPARα), but not PPARβ and PPARγ, blocked this response. The increase in keratinocyte lipid content improved innate barrier functions including antimicrobial activity, paracellular diffusion, and transepidermal water loss. These results reveal that metabolites from a common commensal bacterium have a previously unappreciated influence on the composition of epidermal lipids.

Lactic acid bacteria with probiotic characteristics in fermented dairy products reduce cow milk allergy

The use of fermented dairy products containing lactic acid bacteria (LAB) with probiotic properties has been suggested as a suitable solution to reduce cow milk allergy (CMA). In our previous study, we screened four LAB strains with the ability to hydrolyze allergic milk protein. In this study, we further evaluated the in vivo allergenicity of fermented milk beverage (FMB) made with the compound of four strains. Our results showed that FMB administration significantly reduced the allergic responses induced by milk proteins compared to skimmed milk (SM) administration. Specifically, FMB modulated the T helper cell (Th) 1/Th2 and Th17/T regulatory cell (Treg) immune balance of BALB/c mice, reduced total IgG, total IgG1, and total IgE antibody levels, mast cell protease in serum, and histamine levels in plasma. Additionally, intestinal microbiota analysis demonstrated that FMB administration increased the abundance of Lachnospiraceae, a common immunomodulatory commensal bacteria, and down-regulated the abundance of Muribaculaceae and Prevotellaceae. Overall, FMB is a low-allergenicity dairy product that can alleviate allergy symptoms by regulating the immune response and intestinal microbiota composition. FMB has the potential to be developed as a low-allergenicity dairy product or allergy therapy as well.

Short-Term Dietary Intervention with Whole Oats Protects from Antibiotic-Induced Dysbiosis.

Antibiotic-induced gut microbiome dysbiosis (AID) is known to be influenced by host dietary composition. However, how and when diet modulates gut dysbiosis remains poorly characterized. Thus, here, we utilize a multi-omics approach to characterize how a diet supplemented with oats, a rich source of microbiota-accessible carbohydrates, or dextrose impacts amoxicillin-induced changes to gut microbiome structure and transcriptional activity. We demonstrate that oat administration during amoxicillin challenge provides greater protection from AID than the always oats or recovery oats diet groups. In particular, the group in which oats were provided at the time of antibiotic exposure induced the greatest protection against AID while the other oat diets saw greater effects after amoxicillin challenge. The oat diets likewise reduced amoxicillin-driven elimination of Firmicutes compared to the dextrose diet. Functionally, gut communities fed dextrose were carbohydrate starved and favored respiratory metabolism and consequent metabolic stress management while oat-fed communities shifted their transcriptomic profile and emphasized antibiotic stress management. The metabolic trends were exemplified when assessing transcriptional activity of the following two common gut commensal bacteria: Akkermansia muciniphila and Bacteroides thetaiotaomicron. These findings demonstrate that while host diet is important in shaping how antibiotics effect the gut microbiome composition and function, diet timing may play an even greater role in dietary intervention-based therapeutics. IMPORTANCE We utilize a multi-omics approach to demonstrate that diets supplemented with oats, a rich source of microbiota-accessible carbohydrates, are able to confer protection against antibiotic-induced dysbiosis (AID). Our findings affirm that not only is host diet important in shaping antibiotics effects on gut microbiome composition and function but also that the timing of these diets may play an even greater role in managing AID. This work provides a nuanced perspective on dietary intervention against AID and may be informative on preventing AID during routine antibiotic treatment.

Using the Galleria mellonella burn wound and infection model to identify and characterize potential wound probiotics.

Burn wound infection is the leading cause of mortality among burn wound patients. One of the most commonly isolated bacterial burn wound pathogens is Pseudomonas aeruginosa, a notorious nosocomial multidrug-resistant pathogen. As a consequence of its recalcitrance to frontline antibiotic therapy, there is an urgent need to develop alternative treatment avenues to tackle this pathogen. One potential alternative infection prevention measure is to seed the wound bed with probiotic bacteria. Several species of Lactobacillus, a common commensal bacterium, have been previously reported to display growth inhibition activity against wound pathogens. Various species of this genus have also been shown to augment the wound healing process, which makes it a promising potential therapeutic agent. Due to the complexity of the burn wound trauma and burn wound infection, an in vivo model is required for the development of novel therapeutics. There are multiple in vivo models that are currently available, the most common among them being the murine model. However, mammalian burn wound infection models are logistically challenging, do not lend themselves to screening approaches and come with significant concerns around ethics and animal welfare. Recently, an invertebrate burn wound and infection model using G. mellonella has been established. This model addresses several of the challenges of more advanced animal models, such as affordability, maintenance and reduced ethical concerns. This study validates the capacity of this model to screen for potential wound probiotics by demonstrating that a variety of Lactobacillus spp. can limit P. aeruginosa burn wound infection and improve survival.

Impact of intensified contact precautions while treating hematopoietic stem cell transplantation recipients during aplasia

BackgroundBacterial infections are a major complication for patients undergoing allogeneic hematopoietic stem cell transplantation (HCT). Therefore, protective isolation is considered crucial to prevent nosocomial infections in this population. Here, the impact of intensified contact precautions on environmental contamination and the occurrence of bloodstream infections (BSI) in patients on a HCT unit were compared between two contact precaution measures.MethodsA 2-year retrospective observational study was performed. In the first year, strict contact precaution measures were applied (i.e., protective isolation, the use of sterile personal protective equipment (PPE) by healthcare workers and visitors and sterilization of linen and objects that entered the patient’s room). After one year, contact precautions were reduced (i.e., no use of sterile PPE, no sterilization of linen and objects that entered the patient’s room). Environmental contamination in randomly selected patient rooms was monitored by sampling six standardized environmental sites in the respective patient treatment units. In a before-and-after study, the number of BSI episodes of those patients, who were accommodated in the monitored rooms was compared.ResultsIn total, 181 treatment units were monitored. No significant difference in the contamination of anterooms and patient’s rooms between both groups was found. A total of 168 patients were followed for the occurrence of BSI during the entire study period (before: 84 patients, after: 84 patients). The total count of patients with BSI episodes showed a higher incidence in the period with reduced contact precautions (30/84 vs. 17/84, p = 0.039). The cause of this increasing number of BSI can be traced back to BSI episodes with common commensal bacteria (17/84 vs. 5/84, p = 0.011).ConclusionsThe implementation of maximal barrier measures did not reduce the bacterial contamination of the patients’ environment. The impact on the patients’ outcomes remain controversial. Further research is needed to investigate the impact of infection prevention measures on the clinical outcome of patients undergoing HCT.

Molecular characterization of Staphylococcus species isolates from buck semen and their effect on semen quality

Objective: Buck reproductive health is the key for breeding and production of quality semen. To assess the health of breeding bucks, in this study, we detected the presence of Staphylococcus spp in semen. Staphylococcus aureus is a common commensal and opportunistic pathogenic bacteria and is also a cause of many diseases in animals. Besides this, it can also deteriorate the semen quality. Materials and Methods: In this study, we collected 48 semen ejaculates from healthy bucks of three breeds, namely, Jamunapari, Barbari, and Jakhrana to assess the presence of Staphylococcus spp. Besides bacteriological study, the semen was also assessed for semen quality parameters in infected as well as in non-infected semen samples. Results and Conclusion: The semen quality was significantly deteriorated with Staphylococcus infection. The bacterial infection was initially confirmed as Staphylococcus spp. based on the Gram’s staining and growth on Mannitol salt agar. Based on this preliminary bacteriological analysis, 52.08% (n = 25) of the samples were found positive for Staphylococcus spp. from the total 48 buck semen ejaculates belonging to three different goat breeds. The isolates were confirmed based on the basis of multiplex PCR and the species identified were S. aureus, Staphylococcus sciuri, Staphylococcus haemolyticus, Staphylococcus chromogenes, Staphylococcus epidermidis, and Staphylococcus simulans directly in the buck semen. By this study, it is evident that semen can get contamination from a buck which has the presence of staphylococcus in the reproductive tract and semen quality is adversely affected. Hence, it is important to ensure the health and hygiene of the bucks maintained for semen production for artificial insemination.

A bacteria-regulated gut peptide determines host dependence on specific bacteria to support host juvenile development and survival

BackgroundCommensal microorganisms have a significant impact on the physiology of host animals, including Drosophila. Lactobacillus and Acetobacter, the two most common commensal bacteria in Drosophila, stimulate fly development and growth, but the mechanisms underlying their functional interactions remain elusive.ResultsWe found that imaginal morphogenesis protein-Late 2 (Imp-L2), a Drosophila homolog of insulin-like growth factor binding protein 7, is expressed in gut enterocytes in a bacteria-dependent manner, determining host dependence on specific bacteria for host development. Imp-L2 mutation abolished the stimulatory effects of Lactobacillus, but not of Acetobacter, on fly larval development. The lethality of the Imp-L2 mutant markedly increased under axenic conditions, which was reversed by Acetobacter, but not Lactobacillus, re-association. The host dependence on specific bacteria was determined by Imp-L2 expressed in enterocytes, which was repressed by Acetobacter, but not Lactobacillus. Mechanistically, Lactobacillus and Acetobacter differentially affected steroid hormone-mediated Imp-L2 expression and Imp-L2-specific FOXO regulation.ConclusionsOur finding may provide a way how host switches dependence between different bacterial species when benefiting from varying microbiota.

Concordance between Antimicrobial Resistance Phenotype and Genotype of Staphylococcus pseudintermedius from Healthy Dogs.

Staphylococcus pseudintermedius, a common commensal canine bacterium, is the main cause of skin infections in dogs and is a potential zoonotic pathogen. The emergence of methicillin-resistant S. pseudintermedius (MRSP) has compromised the treatment of infections caused by these bacteria. In this study, we compared the phenotypic results obtained by minimum inhibitory concentration (MICs) for 67 S. pseudintermedius isolates from the skin of nine healthy dogs versus the genotypic data obtained with Nanopore sequencing. A total of 17 antibiotic resistance genes (ARGs) were detected among the isolates. A good correlation between phenotype and genotype was observed for some antimicrobial classes, such as ciprofloxacin (fluoroquinolone), macrolides, or tetracycline. However, for oxacillin (beta-lactam) or aminoglycosides the correlation was low. Two antibiotic resistance genes were located on plasmids integrated in the chromosome, and a third one was in a circular plasmid. To our knowledge, this is the first study assessing the correlation between phenotype and genotype regarding antimicrobial resistance of S. pseudintermedius from healthy dogs using Nanopore sequencing technology.

Novel Requirement for Staphylococcal Cell Wall-Anchored Protein SasD in Pulmonary Infection.

ABSTRACTStaphylococcus aureus can complicate preceding viral infections, including influenza virus. A bacterial infection combined with a preceding viral infection, known as superinfection, leads to worse outcomes than a single infection. Most of the pulmonary infection literature focuses on the changes in immune responses to bacteria between homeostatic and virally infected lungs. However, it is unclear how much of an influence bacterial virulence factors have in single or superinfection. Staphylococcal species express a broad range of cell wall-anchored proteins (CWAs) that have roles in host adhesion, nutrient acquisition, and immune evasion. We screened the importance of these CWAs using mutants lacking individual CWAs in vivo in both bacterial pneumonia and influenza superinfection. In bacterial pneumonia, the lack of individual CWAs leads to various decreases in bacterial burden, lung damage, and immune infiltration into the lung. However, the presence of a preceding influenza infection partially abrogates the requirement for CWAs. In the screen, we found that the uncharacterized CWA S. aureus surface protein D (SasD) induced changes in both inflammatory and homeostatic lung markers. We further characterized a SasD mutant (sasD A50.1) in the context of pneumonia. Mice infected with sasD A50.1 have decreased bacterial burden, inflammatory responses, and mortality compared to wild-type S. aureus. Mice also have reduced levels of interleukin-1β (IL-1β), likely derived from macrophages. Reductions in IL-1β transcript levels as well as increased macrophage viability point at differences in cell death pathways. These data identify a novel virulence factor for S. aureus that influences inflammatory signaling within the lung.IMPORTANCE Staphylococcus aureus is a common commensal bacterium that can cause severe infections, such as pneumonia. In the lung, viral infections increase the risk of staphylococcal pneumonia, leading to combined infections known as superinfections. The most common virus associated with S. aureus pneumonia is influenza, and superinfections lead to worse patient outcomes than either infection alone. While there is much known about how the immune system differs between healthy and virally infected lungs, the role of bacterial virulence factors in single and superinfection is less understood. The significance of our research is identifying bacterial components that play a role in the initiation of lung injury, which could lead to future therapies to prevent pulmonary single or superinfection with S. aureus.

Meningococcal Urethritis: Old and New.

Neisseria meningitidis is a common commensal bacterium found in the respiratory tract, but it can also cause severe, invasive disease. Vaccines have been employed which have been successful in helping to prevent invasive disease caused by encapsulated N. meningitidis from the A, C, W, Y, and B serogroups. Currently, nonencapsulated N. meningitidis groups are more common commensals in the population than in the prevaccine era. One emerging nonencapsulated group of bacteria is the U.S. N. meningitidis urethritis clade (US_NmUC), which can cause meningococcal urethritis in men. US_NmUC has unique genotypic and phenotypic features that may increase its fitness in the male urethra. It is diagnostically challenging to identify and distinguish meningococcal urethritis from Neisseria gonorrhoeae, as the clinical presentation and microbiological findings are overlapping. In this review, the history of meningococcal urethritis, emergence of US_NmUC, laboratory diagnosis, and clinical treatment are all explored.

Differentially Expressed Genes of Pseudomonas aeruginosa Isolates from Eyes with Keratitis and Healthy Conjunctival Sacs.

BackgroundPseudomonas aeruginosa (P. aeruginosa) is the second-most common commensal bacterium in healthy conjunctival sacs. When the corneal epithelial barrier is damaged, P. aeruginosa in a healthy conjunctival sac can cause infectious keratitis, which can result in the loss of vision. This study was designed to investigate the differentially expressed genes (DEGs) of P. aeruginosa isolates from eyes with keratitis and from healthy conjunctival sacs to predict their functions and pathways through Illumina high-throughput RNA sequencing (RNA-seq).MethodsP. aeruginosa isolates from keratitis and healthy conjunctival sacs were obtained. The transcriptome profile of P. aeruginosa was characterized by a high throughput RNA-seq strategy using the Illumina HiSeq 2500 platform. The DEGs were analyzed with DESeq and validated through quantitative real-time polymerase chain reaction (PCR) and with experimental mice. GO enrichment and the KEGG pathway were also analyzed.ResultsIn genome-wide transcriptional analysis, 557 genes (332 upregulated and 225 downregulated) were found to be differentially expressed (fold change ≥ 2, p ≤ 0.05) in the strains from keratitis. GO enrichment analysis suggested that DEGs tended to be associated with cellular and metabolic processes. KEGG pathway analysis revealed the DEGs were typically associated with the pathways of the bacterial secretion system and pyoverdine metabolism. Eleven DEGs were validated using quantitative reverse-transcription PCR and verified with experimental mice. The results were consistent with those obtained in RNA-seq.ConclusionThe DEGs related to pilin, T2SS, T3SS, and pyoverdine metabolisms were significantly altered in the strains from keratitis. The findings may be helpful for further investigations on genes or pathways related to the pathogenesis of and therapeutic targets for P. aeruginosa keratitis.

Suppression of Cutibacterium acnes-Mediated Inflammatory Reactions by Fibroblast Growth Factor 21 in Skin.

Cutibacterium acnes (C. acnes) is a common commensal bacterium that is closely associated with the pathogenesis of acne. Fibroblast growth factor 21 (FGF21), as a favorable regulator of glucose and lipid metabolism and insulin sensitivity, was recently shown to exert anti-inflammatory effects. The role and mechanism of FGF21 in the inflammatory reactions induced by C. acnes, however, have not been determined. The present study shows that FGF21 in the dermis inhibits epidermal C. acnes-induced inflammation in a paracrine manner while it functions on the epidermal layer through a receptor complex consisting of FGF receptor 1 (FGFR1) and β-Klotho (KLB). The effects of FGF21 in heat-killed C. acnes-induced HaCaT cells and living C. acnes-injected mouse ears were examined. In the presence of C. acnes, FGF21 largely counteracted the activation of Toll-like receptor 2 (TLR2), the downstream nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) signaling pathways induced by C. acnes. FGF21 also significantly reduced the expression of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α. Taken together, these findings indicate that FGF21 suppresses C. acnes-induced inflammation and might be used clinically in the management and treatment of acne.

Gut microbiota of the threatened takah\u0113: biogeographic patterns and conservation implications

BackgroundThe Aotearoa New Zealand takahē (Porphyrio hochstetteri), once thought to be extinct, is a nationally threatened flightless rail under intensive conservation management. While there has been previous research into disease-related microbes in takahē, little is known about the microbes present in the gastrointestinal tract. Given the importance of gut-associated microbes to herbivore nutrition and immunity, knowledge of these communities is likely to be of considerable conservation value. Here we examined the gut microbiotas of 57 takahē at eight separate locations across Aotearoa New Zealand.ResultsFaecal samples, taken as a proxy for the hindgut bacterial community, were subjected to 16S rRNA gene amplicon sequencing using Illumina MiSeq. Phylogenetic analysis of > 2200 amplicon sequence variants (ASVs) revealed nine main bacterial phyla (Acidobacteriota, Actinobacteriota, Bacteroidota, Campilobacterota, Firmicutes, Fusobacteriota, Planctomycetota, Proteobacteria, and Verrucomicrobiota) that accounted for the majority of sequence reads. Location was a significant effect (p value < 0.001, 9999 permutations) that accounted for 32% of the observed microbiota variation. One ASV, classified as Lactobacillus aviarius, was present in all samples at an average relative abundance of 17% (SD = 23.20). There was strong evidence (p = 0.002) for a difference in the abundance of the genus Lactobacillus between locations. A common commensal bacterium previously described in takahē, Campylobacter spp., was also detected in most faecal samples.ConclusionsLocation plays a pivotal role in the observed variation among takahē gut bacterial communities and is potentially due to factors such as supplemental feeding and medical treatment experienced by birds housed in captivity at one of the eight sampled sites. These data present a first glimpse of the previously unexplored takahē gut microbiota and provide a baseline for future microbiological studies and conservation efforts.