Microbiology and Immunology最新文献

Probiotics can help prevent antibiotic-associated diarrhea; however, those lacking antimicrobial resistance may be ineffective during antimicrobial treatment. Here, we aimed to examine the effects of antimicrobials on the probiotic strain Bifidobacterium bifidum G9-1 (BBG9-1). Minimum inhibitory concentrations were determined in vitro by culturing B. bifidum G9-1 with antimicrobials and assessing its viability. For in vivo analysis, germ-free and specific pathogen-free mice were administered B. bifidum G9-1 along with antimicrobials. Gut microbiota composition and viable B. bifidum G9-1 abundance were determined. Bifidobacterium bifidum G9-1 was highly sensitive to antimicrobials in vitro. However, in a complex bacterial environment mimicking the gut environment, the abundance of viable B. bifidum G9-1 was significantly high despite antimicrobial exposure. Dominant bacterial populations were more affected by antimicrobials than nondominant populations, with B. bifidum G9-1 exhibiting increased viability in the presence of diverse bacterial species. In vivo, combined administration of antimicrobials and B. bifidum G9-1 significantly reduced B. bifidum G9-1 abundance in germ-free mice but not in specific pathogen-free mice, where the gut microbiota composition shifted following administration of B. bifidum G9-1. The presence of diverse live bacteria in the intestine promotes the survival of B. bifidum G9-1 and its beneficial effects, even in the presence of antimicrobials. This finding suggests that B. bifidum G9-1, despite lacking intrinsic antimicrobial resistance, can survive and reach the large intestine, maintaining its probiotic function. Therefore, B. bifidum G9-1 can potentially be used for antibiotic-associated diarrhea prevention.

Cover photograph: Circular heat map depicting expression patterns of common differentially expressed kinases in both GSE datasets. Microbiol Immunol: 69:326-338. Article link here

In Staphylococcus aureus, a gram-positive pathogen, vancomycin-resistant strains become susceptible to β-lactam antibiotics, referred to as the “seesaw effect.” However, in gram-negative bacteria, the phenomenon is less clear. Here, we analyzed the gene-knockout effects of eight lytic transglycosylases (slt, mltA, mltB, mltC, mltD, mltE, mltF, mltG) on antibiotic sensitivity in Escherichia coli. Knockout of both slt and mltG increased sensitivity to β-lactam antibiotics and reduced sensitivity to vancomycin. The β-lactam antibiotic sensitivity and vancomycin resistance of the slt-knockout mutant were abolished by the introduction of the wild-type slt gene but remained unchanged by the introduction of the mutant slt gene encoding an amino acid substitution variant of the transglycosylase catalytic centre. The double-knockout strain for slt and mltB was more sensitive to ampicillin and more resistant to vancomycin than each single-knockout strain. The double-knockout strain for slt and mltG was more sensitive to ampicillin and more resistant to vancomycin than each single-knockout strain. These results suggest that loss of lytic transglycosylase activity causes β-lactam antibiotic sensitivity and vancomycin resistance in E. coli.

Cover photograph: Functions of soluble and membrane-bound C-type lectins against pathogens. A) Soluble C-type lectins are multimerized and inactivate pathogens by agglutinating or coating their surfaces. They also activate complement to kill pathogens and promote phagocytosis by opsonization. B) Membrane-bound C-type lectins are called C-type lectin receptors (CLRs). CLRs take up pathogens via endocytosis and degrade and inactivate them in lysosomes. The degraded antigens are presented on MHC-II, inducing an acquired immune response. C) CLRs associated with ITAM adapter molecules such as FcRg and DAP12 induce various inflammatory responses necessary for host defense. D) CLRs with hemITAM in the cytoplasmic region directly transmit activation signals. E) CLRs with the inhibitory motif ITIM suppress host immune responses. This can either suppress excessive inflammation caused by pathogens or allow pathogens to evade host immunity. F) ITAM has two sides. Many pathogen ligands are multivalent and transmit activation signals through ITAM, but monovalent ligands transmit inhibitory signals. G) Some CLRs capture pathogens on the cell surface and pass them to other pathogen recognition receptors. Microbiol Immunol: 69:257-269. Article link here

Supplementation with Bifidobacterium bifidum G9-1 (BBG9-1) has been established to enhance the production of butyrate, a short-chain fatty acid (SCFA) known for its beneficial effects in alleviating constipation. We hypothesized that BBG9-1 alters gut microbiota such that bacteria that produce butyric acid from lactate and acetate become more abundant. In this study, we sought to determine whether BBG9-1 promotes the growth of butyrate-producing bacteria and thereby enhances butyrate production. BBG9-1 was cocultured with different butyrate-producing bacteria to compare differences in the SCFA production of cocultures and monocultures. We indeed detected significant increases in the production of SCFAs in cocultures compared to monocultures. Moreover, lactate and butyrate production increased in a time-dependent manner in the BBG9-1 and Faecalibacterium prausnitzii ID 6052 coculture. In addition, acetate production in cocultures initially increased until 16 h, followed by a decline between 20 and 24 h, and a subsequent significant increase at 48 h. Comparatively, lactate and acetate production in the BBG9-1 and Anaerostipes caccae JCM 13470^T coculture peaked at 16 h and declined thereafter, and butyrate production increased in a time-dependent manner. In contrast, lactate, acetate, and butyrate production in the BBG9-1 and Roseburia hominis JCM 17582^T coculture increased in a time-dependent manner. These findings indicate that butyrate-producing bacteria increase butyrate production by utilizing BBG9-1-produced lactate and acetate. Thus, the butyrate-mediated physiological activity of BBG9-1 could be attributed to an indirect enhancement of butyrate production.

Clinical isolates of Streptococcus pyogenes are usually classified using emm and multilocus sequence typing (MLST). Recently, whole genome sequencing (WGS) has been employed for emm typing and MLST analysis. WGS data provides additional information on the presence of virulence factor genes. To enable researchers unfamiliar with bioinformatics to analyze WGS data of S. pyogenes, we opened an online tool named GAS-J, which automatically outputs emm types, sequence types (STs), carriage of virulence factor genes, and phylogenetic trees. The tool accepts raw short-read data as inputs, since it includes the velvet assembler. In all isolates, the emm typing results from this tool were identical to those obtained by conventional PCR and Sanger sequencing, even in cases where isolates had pseudo-emm (emm-like) genes. STs are determined by performing a BLAST search using seven alleles as references. To detect S. pyogenes virulence factor genes, we prepared a new data set containing 620 related proteins. Users may choose which isolates to include in SNP-based phylogenetic tree from a pool of 406 isolates with epidemiological data. The data set includes isolates whose symptoms (STSS or non-STSS) were diagnosed based on the STSS criteria of the Japan Communicable Disease Prevention Law. GAS-J application is available at http://gasj.ncgm.go.jp. The data of isolates are going to be updated in the future.