Human intestinal lumen and mucosa-associated microbiota in patients with colorectal cancer

Recent reports have suggested the involvement of gut microbiota in the progression of colorectal cancer (CRC). We utilized pyrosequencing based analysis of 16S rRNA genes to determine the overall structure of microbiota in patients with colorectal cancer and healthy controls; we investigated microbiota of the intestinal lumen, the cancerous tissue and matched noncancerous normal tissue. Moreover, we investigated the mucosa-adherent microbial composition using rectal swab samples because the structure of the tissue-adherent bacterial community is potentially altered following bowel cleansing. Our findings indicated that the microbial structure of the intestinal lumen and cancerous tissue differed significantly. Phylotypes that enhance energy harvest from diets or perform metabolic exchange with the host were more abundant in the lumen. There were more abundant Firmicutes and less abundant Bacteroidetes and Proteobacteria in lumen. The overall microbial structures of cancerous tissue and noncancerous tissue were similar; however the tumor microbiota exhibited lower diversity. The structures of the intestinal lumen microbiota and mucosa-adherent microbiota were different in CRC patients compared to matched microbiota in healthy individuals. Lactobacillales was enriched in cancerous tissue, whereas Faecalibacterium was reduced. In the mucosa-adherent microbiota, Bifidobacterium, Faecalibacterium, and Blautia were reduced in CRC patients, whereas Fusobacterium, Porphyromonas, Peptostreptococcus, and Mogibacterium were enriched. In the lumen, predominant phylotypes related to metabolic disorders or metabolic exchange with the host, Erysipelotrichaceae, Prevotellaceae, and Coriobacteriaceae were increased in cancer patients. Coupled with previous reports, these results suggest that the intestinal microbiota is associated with CRC risk and that intestinal lumen microflora potentially influence CRC risk via cometabolism or metabolic exchange with the host. However, mucosa-associated microbiota potentially affects CRC risk primarily through direct interaction with the host.     

Xiao-Chai-Hu-Tang ameliorates tumor growth in cancer comorbid depressive symptoms via modulating gut microbiota-mediated TLR4/MyD88/NF-κB signaling pathway

BackgroundDepressive symptoms are thought to promote cancer development and depressive remission has been reported to be effective for defeating cancer. The herbal formula Xiao-Chai-Hu-Tang (XCHT), that has an anti-depressive efficacy, has been widely utilized in China. However, its anti-cancer effect and underlying mechanisms remain unclear.PurposeThe present study aims to investigate the effects of XCHT on the depression-associated tumor and its potential mechanisms.MethodsA placebo-controlled trial was conducted in cancer patients comorbid with depressive symptoms to evaluate the effects of XCHT on depressive scales, tumor-related immune indicators, and gut microbial composition. A xenografted colorectal cancer (CRC) mouse model exposure to chronic restraint stress (CRS) was established to examine XCHT effects on tumorigenesis in vivo. Further, by manipulating gut bacteria with fecal microbial transplantation (FMT) or antibiotics-induced bacterial elimination in CRS-associated xenografted model, gut microbiota-mediated anti-tumor mechanism was explored.ResultsIn cancer patients comorbid with depressive symptoms, XCHT showed substantial effects on improvement of depressive scales, system inflammatory levels and gut dysbiosis. In vivo, XCHT inhibited tumor growth and prolonged survival time in addition to showing anti-depressive effect. Similarly, in our clinical trial, XCHT partially reversed gut dysbiosis, particularly through reducing abundances of Parabacteroides, Blautia and Ruminococcaceae bacterium. Manipulation of gut bacteria in CRS-associated xenografted model further proved that the inhibition of XCHT on tumor progression was mediated by gut microbiota and that the underlying mechanism involves in downregulation of TLR4/MyD88/NF-κB signaling.ConclusionsWe demonstrated that gut microbiota mediates the anti-tumor action of the formula XCHT in cancer patients and models that were comorbid with depressive symptoms. This study implies a novel clinical significance of anti-depressive herbal medicine in the cancer treatment and clarifies the important role of gut microbiota in treating cancer accompanied by depressive symptoms.     

Impact of Pelvic Radiotherapy on Gut Microbiota of Gynecological Cancer Patients Revealed by Massive Pyrosequencing

Although pelvic irradiation is effective for the treatment of various cancer types, many patients who receive radiotherapy experience serious complications. Gut microbial dysbiosis was hypothesized to be related to the occurrence of radiation-induced complications in cancer patients. Given the lack of clinical or experimental data on the impact of radiation on gut microbiota, a prospective observational study of gut microbiota was performed in gynecological cancer patients receiving pelvic radiotherapy. In the current study, the overall composition and alteration of gut microbiota in cancer patients receiving radiation were investigated by 454 pyrosequencing. Gut microbial composition showed significant differences (P < 0.001) between cancer patients and healthy individuals. The numbers of species-level taxa were severely reduced after radiotherapy (P < 0.045), and the abundance of each community largely changed. In particular, the phyla Firmicutes and Fusobacterium were significantly decreased by 10% and increased by 3% after radiation therapy, respectively. In addition, overall gut microbial composition was gradually remolded after the full treatment course of pelvic radiotherapy. In this set of cancer patients, dysbiosis of the gut microbiota was linked to health status, and the gut microbiota was influenced by pelvic radiotherapy. Although further studies are needed to elucidate the relationship between dysbiosis and complications induced by pelvic radiotherapy, the current study may offer insights into the treatment of cancer patients suffering from complications after radiation therapy.     

Dysbiosis Signature of Fecal Microbiota in Colorectal Cancer Patients

The human gut microbiota is a complex system that is essential to the health of the host. Increasing evidence suggests that the gut microbiota may play an important role in the pathogenesis of colorectal cancer (CRC). In this study, we used pyrosequencing of the 16S rRNA gene V3 region to characterize the fecal microbiota of 19 patients with CRC and 20 healthy control subjects. The results revealed striking differences in fecal microbial population patterns between these two groups. Partial least-squares discriminant analysis showed that 17 phylotypes closely related to Bacteroides were enriched in the gut microbiota of CRC patients, whereas nine operational taxonomic units, represented by the butyrate-producing genera Faecalibacterium and Roseburia, were significantly less abundant. A positive correlation was observed between the abundance of Bacteroides species and CRC disease status (R?=?0.462, P?=?0.046?<?0.5). In addition, 16 genera were significantly more abundant in CRC samples than in controls, including potentially pathogenic Fusobacterium and Campylobacter species at genus level. The dysbiosis of fecal microbiota, characterized by the enrichment of potential pathogens and the decrease in butyrate-producing members, may therefore represent a specific microbial signature of CRC. A greater understanding of the dynamics of the fecal microbiota may assist in the development of novel fecal microbiome-related diagnostic tools for CRC.     

Towards the human colorectal cancer microbiome

Multiple factors drive the progression from healthy mucosa towards sporadic colorectal carcinomas and accumulating evidence associates intestinal bacteria with disease initiation and progression. Therefore, the aim of this study was to provide a first high-resolution map of colonic dysbiosis that is associated with human colorectal cancer (CRC). To this purpose, the microbiomes colonizing colon tumor tissue and adjacent non-malignant mucosa were compared by deep rRNA sequencing. The results revealed striking differences in microbial colonization patterns between these two sites. Although inter-individual colonization in CRC patients was variable, tumors consistently formed a niche for Coriobacteria and other proposed probiotic bacterial species, while potentially pathogenic Enterobacteria were underrepresented in tumor tissue. As the intestinal microbiota is generally stable during adult life, these findings suggest that CRC-associated physiological and metabolic changes recruit tumor-foraging commensal-like bacteria. These microbes thus have an apparent competitive advantage in the tumor microenvironment and thereby seem to replace pathogenic bacteria that may be implicated in CRC etiology. This first glimpse of the CRC microbiome provides an important step towards full understanding of the dynamic interplay between intestinal microbial ecology and sporadic CRC, which may provide important leads towards novel microbiome-related diagnostic tools and therapeutic interventions.     

The power of small changes: Comprehensive analyses of microbial dysbiosis in breast cancer

Disparate occurrence of breast cancer remains an intriguing question since only a subset of women with known risk factors develop cancer. Recent studies suggest an active role of local and distant microbiota in breast cancer initiation, progression, and overall prognosis. A dysbiotic microbiota predisposes the body to develop cancer by inducing genetic instability, initiating DNA damage and proliferation of the damaged progeny, eliciting favorable immune response, metabolic dysregulation and altered response to therapy. In this review, we present our analyses of the existing datasets and discuss the local dysbiosis observed in breast cancer patients and different aspects of breast carcinogenesis that can be potentially influenced by local breast microbiota. Striking differences between microbial community compositions in breast of cancer patients compared to healthy individuals were noted. Differences in microbiome were also apparent between benign and malignant disease and between nipple aspirate fluid of healthy individuals and breast survivors. We also discuss the identification of distinct bacterial, fungal, viral as well as parasite signatures for breast cancer. These microbes are capable of producing numerous secondary metabolites that can act as signaling mediators effecting breast cancer progression. We review how microbes potentially alter response to therapy affecting drug metabolism, pharmacokinetics, anti-tumor effects and toxicity. In conclusion, breast harbors a community of microbes that can communicate with the host cells inducing downstream signaling pathways and modulating various aspects of breast cancer growth and metastatic progression and an improved understanding of microbial dysbiosis can potentially reduce breast cancer risk and improve outcomes of breast cancer patients.The human microbiome, now referred to as, the “forgotten organ” contains a metagenome that is 100-fold more diverse compared to the human genome, thereby, is critically associated with human health [1,2]. With the revelations of the human microbiome project and advent of deep sequencing techniques, a plethora of information has been acquired in recent years. Body sites like stomach, bladder and lungs, once thought to be sterile, are now known to harbor millions of indigenous microbial species. Approximately 80% of the healthy microbiome consists of Firmicutes and Bacteroidetes accompanied by Verrucomicrobia, Actinobacteria, Proteobacteria, Tenericutes and Cyanobacteria [[2], [3], [4], [5], [6], [7]]. The role of microbiome in diabetes, obesity and even neurodegenerative diseases was greatly appreciated in the last decade [1,[7], [8], [9], [10], [11], [12], [13], [14]] and now it has been established that microbiome significantly contributes to many organ specific cancers [1,15,16].     

Microbial dysbiosis in colorectal cancer (CRC) patients

The composition of the human intestinal microbiota is linked to health status. The aim was to analyze the microbiota of normal and colon cancer patients in order to establish cancer-related dysbiosis.

Patients and Methods

Stool bacterial DNA was extracted prior to colonoscopy from 179 patients: 60 with colorectal cancer, and 119 with normal colonoscopy. Bacterial genes obtained by pyrosequencing of 12 stool samples (6 Normal and 6 Cancer) were subjected to a validated Principal Component Analysis (PCA) test. The dominant and subdominant bacterial population (C. leptum, C. coccoides, Bacteroides/Prevotella, Lactobacillus/Leuconostoc/Pediococcus groups, Bifidobacterium genus, and E. coli, and Faecalibacterium prausnitzii species) were quantified in all individuals using qPCR and specific IL17 producer cells in the intestinal mucosa were characterized using immunohistochemistry.

Findings

Pyrosequencing (Minimal sequence 200 nucleotide reads) revealed 80% of all sequences could be assigned to a total of 819 taxa based on default parameter of Classifier software. The phylogenetic core in Cancer individuals was different from that in Normal individuals according to the PCA analysis, with trends towards differences in the dominant and subdominant families of bacteria. Consequently, All-bacteria [log₁₀ (bacteria/g of stool)] in Normal, and Cancer individuals were similar [11.88±0.35, and 11.80±0.56, respectively, (P = 0.16)], according to qPCR values whereas among all dominant and subdominant species only those of Bacteroides/Prevotella were higher (All bacteria-specific bacterium; P = 0.009) in Cancer (-1.04±0.55) than in Normal (-1.40±0.83) individuals. IL17 immunoreactive cells were significantly expressed more in the normal mucosa of cancer patients than in those with normal colonoscopy.

Conclusion

This is the first large series to demonstrate a composition change in the microbiota of colon cancer patients with possible impact on mucosal immune response. These data open new filed for mass screening and pathophysiology investigations.     

Analysis of mitochondrial DNA copy number variation in blood and tissue samples of metastatic breast cancer patients (A pilot study)

Changes in mitochondrial DNA (mt-DNA) copy number in blood/tissue have been linked to increased risk of several cancers; however, studies on their association in breast cancer is still lacking. In this pilot study, we investigated mt-DNA copy number variation in peripheral blood and tissue samples from metastatic breast cancer patients and compared their differences. For the study, peripheral blood samples from non-cancer individuals (control) and breast cancer patients, along with resected tissues from adjacent and tumor sites from same breast cancer patients were collected. Total genomic DNA was isolated and changes in mt-DNA copy number were measured by relative quantification using SYBR green based quantitative real time PCR method. Our results indicated a significant reduction in mt-DNA copy number in blood samples of breast cancer patients compared to control. However, a significantly higher mt-DNA copy number was observed in tumor tissue when compared with paired non tumor tissue. There was no significant difference in mt-DNA copy number between blood and adjacent tumor tissue samples of the breast cancer patients. Overall, our study reports for the first time a comparison of mt-DNA copy number in blood and paired tissue together and suggested that mt-DNA copy number is differentially regulated in blood and tumor tissues in breast cancer.     

Gut microbial dysbiosis is associated with development and progression of radiation enteritis during pelvic radiotherapy

Radiation enteritis (RE) is the most common complication of radiotherapy for pelvic irradiation receivers. Herein we investigated the alterations in gut microbial profiles and their association with enteritis in patients undergoing pelvic radiotherapy. Faecal samples were collected from 18 cervical cancer patients during radiotherapy. Microbiota profiles were characterized based on 16S rRNA sequencing using the Illumina HiSeq platform. Epithelial inflammatory response was evaluated using bacterial‐epithelial co‐cultures. Dysbiosis was observed among patients with RE, which was characterized by significantly reduced α‐diversity but increased β‐diversity, relative higher abundance of Proteobacteria and Gammaproteobacteria and lower abundance of Bacteroides. Coprococcus was clearly enriched prior to radiotherapy in patients who later developed RE. Metastat analysis further revealed unique grade‐related microbial features, such as more abundant Virgibacillus and Alcanivorax in patients with mild enteritis. Additionally, using bacterial‐epithelial co‐cultures, RE patient‐derived microbiota induced epithelial inflammation and barrier dysfunction, enhanced TNF‐α and IL‐1β expression compared with control microbiota. Taken together, we define the overall picture of gut microbiota in patients with RE. Our results suggest that dysbiosis of gut microbiota may contribute to development and progression of RE. Gut microbiota can offer a set of biomarkers for prediction, disease activity evaluation and treatment selection in RE.     

Matricellular CCN6 (WISP3) protein: a tumor suppressor for mammary metaplastic carcinomas

Located at 6q22–23, Ccn6 (WISP3) encodes for a matrix-associated protein of the CCN family, characterized by regulatory, rather than structural, roles in development and cancer. CCN6, the least studied member of the CCN family, shares the conserved multimodular structure of CCN proteins, as well as their tissue and cell-type specific functions. In the breast, CCN6 is a critical regulator of epithelial-to-mesenchymal transitions (EMT) and tumor initiating cells. Studies using human breast cancer tissue samples demonstrated that CCN6 messenger RNA and protein are expressed in normal breast epithelia but reduced or lost in aggressive breast cancer phenotypes, especially inflammatory breast cancer and metaplastic carcinomas. Metaplastic carcinomas are mesenchymal-like triple negative breast carcinomas, enriched for markers of EMT and stemness. RNAseq analyses of the TCGA Breast Cancer cohort show reduced CCN6 expression in approximately 50% of metaplastic carcinomas compared to normal breast. Our group identified frameshift mutations of Ccn6 in a subset of human metaplastic breast carcinoma. Importantly, conditional, mammary epithelial-cell specific ccn6 (wisp3) knockout mice develop invasive high-grade mammary carcinomas that recapitulate human spindle cell metaplastic carcinomas, demonstrating a tumor suppressor function for ccn6. Our studies on CCN6 functions in metaplastic carcinoma highlight the potential of CCN6 as a novel therapeutic approach for this specific type of breast cancer.     

Bifidobacteria Abundance-Featured Gut Microbiota Compositional Change in Patients with Behcet’s Disease

Gut microbiota compositional alteration may have an association with immune dysfunction in patients with Behcet’s disease (BD). We conducted a fecal metagenomic analysis of BD patients. We analyzed fecal microbiota obtained from 12 patients with BD and 12 normal individuals by sequencing of 16S ribosomal RNA gene. We compared the relative abundance of bacterial taxa. Direct comparison of the relative abundance of bacterial taxa demonstrated that the genera Bifidobacterium and Eggerthella increased significantly and the genera Megamonas and Prevotella decreased significantly in BD patients compared with normal individuals. A linear discriminant analysis of bacterial taxa showed that the phylum Actinobacteria, including Bifidobacterium, and the family Lactobacillaceae exhibited larger positive effect sizes than other bacteria in patients with BD. The phylum Firmicutes and the class Clostridia had large effect sizes in normal individuals. There was no significant difference in annotated species numbers (as numbers of operational taxonomic unit; OTU) and bacterial diversity of each sample (alpha diversity) between BD patients and normal individuals. We next assigned each sample to a position using three axes by principal coordinates analysis of the OTU table. The two groups had a significant distance as beta diversity in the 3-axis space. Fecal sIgA concentrations increased significantly in BD patients but did not correlate with any bacterial taxonomic abundance. These data suggest that the compositional changes of gut microbes may be one type of dysbiosis (unfavorable microbiota alteration) in patients with BD. The dysbiosis may have an association with the pathophysiology of BD.     

Differential methylation of TSP50 and mTSP50 genes in different types of human tissues and mouse spermatic cells

Earlier studies identified human TSP50 as a testis-specific gene that encoded a threonine protease. Most importantly, TSP50 could be a cancer/testis antigen since there was a high frequency of reactivation in breast cancer biopsies. It was also found to be negatively regulated by the p53 gene. To further characterize this gene, we recently examined the DNA methylation patterns of the TSP50 gene promoter in normal human testis, as well as breast tissue and a testicular embryonic carcinoma cell line (HTECCL). Bisulfite genomic sequencing results demonstrated that the promoter exhibited mixed DNA methylation patterns in normal human testis, mainly non-methylation versus slight methylation, which could be attributed to the different stages spermatic cells go through during spermatogenesis. In contrast, it was methylated to a much greater extent in both breast tissue and HTECCL. To find out whether DNA methylation status was related to spermatogenesis stages, we analyzed DNA methylation patterns of the mTSP50 (the mouse ortholog of TSP50) promoter in spermatocytes and spermatozoa isolated from sexually mature mice. The results clearly demonstrated that each group of cells exhibited its preferential DNA methylation pattern that apparently was consistent with the gene expression status observed before. Taken together, our findings suggested that DNA methylation might regulate the TSP50 and mTSP50 gene expressions in different types of tissues and spermatic cells.     

Molecular profiling of mucosal tissue associated microbiota in patients manifesting acute exacerbations and remission stage of ulcerative colitis

Dysbiosis of intestinal microflora has been postulated in ulcerative colitis (UC), which is characterized by imbalance of mucosal tissue associated bacterial communities. However, the specific changes in mucosal microflora during different stages of UC are still unknown. The aim of the current study was to investigate the changes in mucosal tissue associated microbiota during acute exacerbations and remission stages of UC. The mucosal microbiota associated with colon biopsy of 12 patients suffering from UC (exacerbated stage) and the follow-up samples from the same patients (remission stage) as well as non-IBD subjects was studied using 16S rRNA gene-based sequencing and quantitative PCR. The total bacterial count in patients suffering from exacerbated phase of UC was observed to be two fold lower compared to that of the non-IBD subjects (p?=?0.0049, Wilcox on matched-pairs signed rank tests). Bacterial genera including Stenotrophomonas, Parabacteroides, Elizabethkingia, Pseudomonas, Micrococcus, Ochrobactrum and Achromobacter were significantly higher in abundance during exacerbated phase of UC as compared to remission phase. The alterations in bacterial diversity with an increase in the abnormal microbial communities signify the extent of dysbiosis in mucosal microbiota in patients suffering from UC. Our study helps in identifying the specific genera dominating the microbiota during the disease and thus lays a basis for further investigation of the possible role of these bacteria in pathogenesis of UC.     

DNA methylation changes in murine breast adenocarcinomas allow the identification of candidate genes for human breast carcinogenesis

Epigenetic inactivation due to aberrant promoter methylation is a key process in breast tumorigenesis. Murine models for human breast cancer have been established for nearly every important human oncogene or tumor suppressor gene. Mouse-to-human comparative gene expression and cytogenetic profiling have been widely investigated for these models; however, little is known about the conservation of epigenetic alterations during tumorigenesis. To determine if this key process in human breast tumorigenesis is also mirrored in a murine breast cancer model, we mapped cytosine methylation changes in primary adenocarcinomas and paired lung metastases derived from the polyomavirus middle T antigen mouse model. Global changes in methylcytosine levels were observed in all tumors when compared to the normal mammary gland. Aberrant methylation and associated gene silencing was observed for Hoxa7, a gene that is differentially methylated in human breast tumors, and Gata2, a novel candidate gene. Analysis of HOXA7 and GATA2 expression in a bank of human primary tumors confirms that the expression of these genes is also reduced in human breast cancer. In addition, HOXA7 hypermethylation is observed in breast cancer tissues when compared to adjacent tumor-free tissue. Based on these studies, we present a model in which comparative epigenetic techniques can be used to identify novel candidate genes important for human breast tumorigenesis, in both primary and metastatic tumors.     

Capsule-Transmitted Gut Symbiotic Bacterium of the Japanese Common Plataspid Stinkbug, Megacopta punctatissima

The Japanese common plataspid stinkbug, Megacopta punctatissima, deposits small brown particles, or symbiont capsules, on the underside of the egg mass for the purpose of transmission of symbiotic bacteria to the offspring. We investigated the microbiological aspects of the bacteria contained in the capsule, such as microbial diversity, phylogenetic placement, localization in vivo, and fitness effects on the host insect. Restriction fragment length polymorphism analysis of 16S ribosomal DNA clones revealed that a single bacterial species dominates the microbiota in the capsule. The bacterium was not detected in the eggs but in the capsules, which unequivocally demonstrated that the bacterium is transmitted to the offspring of the insect orally rather than transovarially, through probing of the capsule content. Molecular phylogenetic analysis showed that the bacterium belongs to the γ-subdivision of the Proteobacteria. In adult insects the bacterium was localized in the posterior section of the midgut. Deprivation of the bacterium from the nymphs resulted in retarded development, arrested growth, abnormal body coloration, and other symptoms, suggesting that the bacterium is essential for normal development and growth of the host insect.     

The Emerging Biotherapeutic Agent: Akkermansia

The human gastrointestinal tract (GIT) is a well-recognized hub of microbial activities. The microbiota harboring the mucus layer of the GIT act as a defense against noxious substances, and pathogens including Clostridium difficile, Enterococcus faecium, Escherichia coli, Salmonella Typhimurium. Toxins, pathogens, and antibiotics perturb the commensal floral composition within the GIT. Imbalanced gut microbiota leads to dysbiosis, manifested as diseases ranging from obesity, diabetes, and cancer to reduced lifespan. Among the bacteria present in the gut microbiome, the most beneficial are those representing Firmicutes and Bacteroidetes. Recent studies have revealed the emergence of a novel biotherapeutic agent, Akkermansia, which is instrumental in regaining eubiosis and conferring various health benefits.     

Mining zebrafish microbiota reveals key community-level resistance against fish pathogen infection

The long-known resistance to pathogens provided by host-associated microbiota fostered the notion that adding protective bacteria could prevent or attenuate infection. However, the identification of endogenous or exogenous bacteria conferring such protection is often hindered by the complexity of host microbial communities. Here, we used zebrafish and the fish pathogen Flavobacterium columnare as a model system to study the determinants of microbiota-associated colonization resistance. We compared infection susceptibility in germ-free, conventional and reconventionalized larvae and showed that a consortium of 10 culturable bacterial species are sufficient to protect zebrafish. Whereas survival to F. columnare infection does not rely on host innate immunity, we used antibiotic dysbiosis to alter zebrafish microbiota composition, leading to the identification of two different protection strategies. We first identified that the bacterium Chryseobacterium massiliae individually protects both larvae and adult zebrafish. We also showed that an assembly of 9 endogenous zebrafish species that do not otherwise protect individually confer a community-level resistance to infection. Our study therefore provides a rational approach to identify key endogenous protecting bacteria and promising candidates to engineer resilient microbial communities. It also shows how direct experimental analysis of colonization resistance in low-complexity in vivo models can reveal unsuspected ecological strategies at play in microbiota-based protection against pathogens.Subject terms: Microbiome, Microbial ecology     

The microbiota protects against Pseudomonas aeruginosa pneumonia via γδ T cell-neutrophil axis in mice

Exposure to antimicrobials leading to microbiota dysbiosis has been found to be an independent risk factor for extensively drug-resistant Pseudomonas aeruginosa acquisition. Microbiota dysbiosis may induce imbalanced immune responses and can affect disease susceptibility. However, the potential role of commensal microbiota in bacterial pneumonia is poorly defined. The aim of this study was to investigate the mechanistic basis for the defective host defenses against P. aeruginosa pneumonia induced by antibiotic pretreatment perturbing microbiota. We found that antibiotic pretreatment significantly perturbed the composition of intestinal microbiota. The microbiota dysbiosis impaired host defenses against P. aeruginosa pneumonia, as reflected by the increased bacterial burden and dissemination, compromised local inflammatory responses and shortened survival time in microbiota-depleted mice compared with controls. This impairment correlated with a defective γδ T17 cell and downstream neutrophil responses. Anti-TCRγδ-treated mice had changes similar to those in the microbiota-depleted mice. Overall, our results suggest the importance of microbiota in supporting the host defense against pneumonia, define a crucial role for the γδ T cell-neutrophil axis in the potential mechanism, and delineate the deleterious effects of antibiotic treatment on antibacterial defenses.