Staphylococcus aureus (S. aureus) is the leading cause of various infective diseases, including topical soft tissue infections. The goals of this study were to investigate the roles of YycF and CodY in the regulation of biofilm formation and pathogenicity.

Pseudomonas is one of the most diverse bacterial genera identified in the environment. Genome sequence analysis has indicated that this genus can be clustered into three lineages and ten groups. Each group can adopt different mechanisms to thrive under zinc-depleted or high-zinc conditions, two environments that are frequently encountered during their environmental propagation. The response of three prominent Pseudomonas strains (Pseudomonas aeruginosa PAO1, Pseudomonas putida KT2440, and Pseudomonas fluorescens ATCC 13525T) to minimal inhibitory concentrations of zinc were compared using RNA-seq and ultra-performance liquid chromatography-tandem mass spectrometry analysis. Results demonstrated that the three strains shared only minimal similarity at the transcriptional level. Only four genes responsible for zinc efflux were commonly upregulated. P. aeruginosa PAO1 specifically downregulated the operons involved in siderophore synthesis and the genes that encode ribosomal protein, while upregulated the genes associated with antibiotic efflux and cell envelope biosynthesis. The membrane transporters in P. putida KT2440 were globally downregulated, indicating changes in cell permeability. Compared with P. aeruginosa PAO1 and P. putida KT2440, the most remarkable transcriptional variation in P. fluorescens ATCC 13525T is the significant downregulation of the type VI secretion system. Metabolite quantitative analysis showed that low concentrations of the metabolites involved in central carbon metabolism and amino acid synthesis were detected in the three strains. In summary, the cellular responses of the three strains under high-zinc condition is quite divergent. Although similar metal efflux systems were upregulated, the three strains employed different pathways to reduce zinc intrusion. In addition, zinc treatment can increase the difficulties of scavenging P. aeruginosa from its colonization area, and reduce the competitiveness of P. fluorescens in microbiota.

Dental caries is a biofilm-dependent disease that largely relies on the ability of Streptococcus mutans to synthesize exopolysaccharides. Although the rnc gene is suggested to be involved in virulence mechanisms in many other bacteria, the information regarding it in S. mutans is very limited. Here, using deletion or overexpression mutant assay, we demonstrated that rnc in S. mutans significantly positively regulated exopolysaccharide synthesis and further altered biofilm formation. Meanwhile, the cariogenecity of S. mutans was decreased by deletion of rnc in a specific pathogen-free (SPF) rat model. Interestingly, analyzing the expression at mRNA level, we found the downstream vic locus was repressed by rnc in S. mutans. Using deep sequencing and bioinformatics analysis, for the first time, three putative microRNA-size small RNAs (msRNAs) targeting vicRKX were predicted in S. mutans. The expression levels of these msRNAs were negatively correlated with vicRKX but positively correlated with rnc, indicating rnc probably repressed vicRKX expression through msRNAs at the post-transcriptional level. In all, the results present that rnc has a potential role in the regulation of exopolysaccharide synthesis and can affect vicRKX expressions via post-transcriptional repression in S. mutans. This study provides an alternative avenue for further research aimed at preventing caries.

We investigated antimicrobial resistance trends and characteristics of ESBL-producing Escherichia coli isolates from pets and whether this correlates with antibiotic usage in the clinic. Clinical samples containing E. coli from diseased cats and dogs were screened for antibiotic sensitivity and associated genotypic features. We identified 127 E. coli isolates from 1886 samples from dogs (n = 1565) and cats (n = 321) with the majority from urinary tract infections (n = 108, 85%). High rates of resistance were observed for β-lactams and fluoroquinolones and resistance to > 3 antibiotic classes (MDR) increased from 67% in 2012 to 75% in 2017 (P < 0.0001). This was especially true for strains resistant to 6-9 antibiotics that increased from 26.67 to 60.71%. Increased rates in β-lactam use for clinical treatment accompanied these increasing resistance rates. Accordingly, the most frequently encountered subtypes were bla CTX-M (n = 44, 34.65%), bla CTX-M-65 (n = 19) and bla CTX-M-15 (n = 18) and qnrB (n = 119, 93.70%). The bla CTX-M-isolates possessed 36 unique pulsed field electrophoretic types (PFGEs) and 28 different sequence types (STs) in ST405 (7, 15.9%), ST131 (3, 6.8%), ST73, ST101, ST372, and ST827 (2, 4.5% each) were the most prevalent. This data demonstrated a high level of diversity for the bla CTX-M-positive E. coli isolates. Additionally, bla NDM-5 was detected in three isolates (n = 3, 2.36%), comprised of two ST101 and one ST405 isolates, and mcr-1 was also observed in three colistin-resistant E. coli with three different STs (ST6316, ST405, and ST46). Our study demonstrates an increasing trend in MDR and ESBL-producing E. coli and this correlated with β-lactam antibiotic usage for treatment of these animals. This data indicates that there is significant risk for the spread of resistant bacteria from pets to humans and antibiotic use for pets should be more strictly regulated.

The cariogenic pathogen Streptococcus mutans effectively utilizes dietary sucrose for the synthesis of exopolysaccharide, which act as a scaffold for its biofilm, thus contributing to its pathogenicity, environmental stress tolerance, and antimicrobial resistance. The two-component system VicRK of S. mutans regulates a group of virulence genes that are associated with biofilm matrix synthesis. Knockout of vicX affects biofilm formation, oxidative stress tolerance, and transformation of S. mutans. However, little is known regarding the vicX-modulated structural characteristics of the exopolysaccharides underlying the biofilm formation and the phenotypes of the vicX mutants. Here, we identified the role of vicX in the structural characteristics of the exopolysaccharide matrix and biofilm physiology. The vicX mutant (SmuvicX) biofilms seemingly exhibited "desertification" with architecturally impaired exopolysaccharide-enmeshed cell clusters, compared with the UA159 strain (S. mutans wild type strain). Concomitantly, SmuvicX showed a decrease in water-insoluble glucan (WIG) synthesis and in WIG/water-soluble glucan (WSG) ratio. Gel permeation chromatography (GPC) showed that the WIG isolated from the SmuvicX biofilms had a much lower molecular weight compared with the UA159 strain indicating differences in polysaccharide chain lengths. A monosaccharide composition analysis demonstrated the importance of the vicX gene in the glucose metabolism. We performed metabolite profiling via (1)H nuclear magnetic resonance spectroscopy, which showed that several chemical shifts were absent in both WSG and WIG of SmuvicX biofilms compared with the UA159 strain. Thus, the modulation of structural characteristics of exopolysaccharide by vicX provides new insights into the interaction between the exopolysaccharide structure, gene functions, and cariogenicity. Our results suggest that vicX gene modulates the structural characteristics of exopolysaccharide associated with cariogenicity, which may be explored as a potential target that contributes to dental caries management. Furthermore, the methods used to purify the EPS of S. mutans biofilms and to analyze multiple aspects of its structure (GPC, gas chromatography-mass spectrometry, and (1)H nuclear magnetic resonance spectroscopy) may be useful approaches to determine the roles of other virulence genes for dental caries prevention.

Portal vein thrombosis (PVT) is a serious complication of liver cirrhosis (LC) and is closely related to gut homeostasis. The study aimed to investigate the composition of gut microbiota and its putative role in PVT development in LC.