Anti-Virulence Properties of Plant Species: Correlation between In Vitro Activity and Efficacy in a Murine Model of Bacterial Infection

Several plant extracts exhibit anti-virulence properties due to the interruption of bacterial quorum sensing (QS). However, studies on their effects at the preclinical level are scarce. Here, we used a murine model of abscess/necrosis induced by Pseudomonas aeruginosa to evaluate the anti-pathogenic efficacy of 24 plant extracts at a sub-inhibitory concentration. We analyzed their ability to inhibit QS-regulated virulence factors such as swarming, pyocyanin production, and secretion of the ExoU toxin via the type III secretion system (T3SS). Five of the seven extracts with the best anti-pathogenic activity reduced ExoU secretion, and the extracts of Diphysa americana and Hibiscus sabdariffa were identified as the most active. Therefore, the abscess/necrosis model allows identification of plant extracts that have the capacity to reduce pathogenicity of P. aeruginosa. Furthermore, we evaluated the activity of the plant extracts on Chromobacterium violaceum. T3SS (ΔescU) and QS (ΔcviI) mutant strains were assessed in both the abscess/necrosis and sepsis models. Only the ΔescU strain had lower pathogenicity in the animal models, although no activity of plant extracts was observed. These results demonstrate differences between the anti-virulence activity recorded in vitro and pathogenicity in vivo and between the roles of QS and T3S systems as virulence determinants.

Characterisation of Bacterial Isolates from Infected Post-Operative Patients in a Malaysian Tertiary Heart Care Centre

Several bacterial species cause post-operative infections, which has been a critical health concern among hospital patients. Our study in this direction is a much-needed exploratory study that was carried out at the National Heart Institute (IJN) of Malaysia to examine the virulence properties of causative bacteria obtained from postoperative patients. The bacterial isolates and data were provided by the IJN. Antibiotic resistance gene patterns, and the ability to form biofilm were investigated for 127 isolates. Klebsiella pneumoniae (36.2%) was the most common isolate collected, which was followed by Pseudomonas aeruginosa (26%), Staphylococcus aureus (23.6%), Streptococcus spp. (8.7%) and Acinetobacter baumannii (5.5%). There were 49 isolates that showed the presence of multidrug resistance genes. The mecA gene was surprisingly found in methicillin-susceptible S. aureus (MSSA), which also carried the ermA gene from those erythromycin-susceptible strains. The phenotypic antibiotic resistance profiles varied greatly between isolates. Findings from the biofilm assay revealed that 44 of the 127 isolates demonstrated the ability to produce biofilms. Our findings provide insights into the possibility of some of these bacteria surviving under antibiotic stress, and some antibiotic resistance genes being silenced.

The role of the oral microbiome in the diagnosis and prognosis of tumors of the oral cavity

Despite advancement in tumors treatment, oral cancer has a poor prognosis and is often detected at late stage. Recent advancement in metagenomic technologies may be useful in identifying oral tumors–related microbiome, their genomes, virulence properties, and their interaction with host immunity. Alteration in the oral commensal microbial communities have potential application as a diagnostic tool to predict oral tumors. To develop highly precise and effective therapeutic approaches, identification of specific oral microbiomes may be required. In this review, we narrate the role of microbiome in the progression of oral tumors and its role as an early diagnostic and prognostic biomarker for oral tumors.

Virulence response of escherichia coli O157:H7 to bile salts and short chain fatty acids

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a gastrointestinal pathogen which causes hemorrhagic colitis and can lead to neurological damage, acute kidney failure (hemolytic uremic syndrome and vascular lesions. During intestinal colonization EHEC is exposed to a variety of stresses including bile salts (BS) in the small intestine and short chain fatty acids (SCFA) in the large intestine; little is known about how these stresses affect this pathogen's virulence properties. The goal of this study was to investigate the impact of exposure of E. coli O157:H7 to physiologically relevant concentrations of BS and SCFA alone and in mixtures on bacterial survival, verotoxin production and adhesion to human epithelial cells. The results indicated that BS treatments significantly enhanced several virulence properties including survival and adhesion to human epthelial cell lines including colonic epithelial cells. Verotoxin production was not affected by any of the BS treatments. Bacterial pretreatment with erythromycin at a sub-minimal inhibitory concentration eliminated the adhesion enhancement after BS treatment, suggesting that protein synthesis was required for enhanced adhesion of BS treated organisms. Using the isogenci mutant of the known adhesions, intimin and iha it was established that there was no role for intimin or iha in the BS-induced adhesion enhancement. SCFA treatments reduced bacterial viability but significantly enhanced both adhesion to human epithelial cells and verotoxin production. The results of this research indicate that ingestion stresses such as BS and SCFA, which are part of the host's natural chemical assault on foreign organisms, may actually enhance the viulence properties of this pathogen and contribute to, rather than, prevent infection. Furthermore, they suggest that this pathogen may use these ingestion stresses to cue the expression of numerous virulence factors for successful infection of local microenvironments.

Virulence response of escherichia coli O157:H7 to bile salts and short chain fatty acids

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a gastrointestinal pathogen which causes hemorrhagic colitis and can lead to neurological damage, acute kidney failure (hemolytic uremic syndrome and vascular lesions. During intestinal colonization EHEC is exposed to a variety of stresses including bile salts (BS) in the small intestine and short chain fatty acids (SCFA) in the large intestine; little is known about how these stresses affect this pathogen's virulence properties. The goal of this study was to investigate the impact of exposure of E. coli O157:H7 to physiologically relevant concentrations of BS and SCFA alone and in mixtures on bacterial survival, verotoxin production and adhesion to human epithelial cells. The results indicated that BS treatments significantly enhanced several virulence properties including survival and adhesion to human epthelial cell lines including colonic epithelial cells. Verotoxin production was not affected by any of the BS treatments. Bacterial pretreatment with erythromycin at a sub-minimal inhibitory concentration eliminated the adhesion enhancement after BS treatment, suggesting that protein synthesis was required for enhanced adhesion of BS treated organisms. Using the isogenci mutant of the known adhesions, intimin and iha it was established that there was no role for intimin or iha in the BS-induced adhesion enhancement. SCFA treatments reduced bacterial viability but significantly enhanced both adhesion to human epithelial cells and verotoxin production. The results of this research indicate that ingestion stresses such as BS and SCFA, which are part of the host's natural chemical assault on foreign organisms, may actually enhance the viulence properties of this pathogen and contribute to, rather than, prevent infection. Furthermore, they suggest that this pathogen may use these ingestion stresses to cue the expression of numerous virulence factors for successful infection of local microenvironments.

The New Antibacterial Properties of the Plants: Quo vadis Studies of Anti-virulence Phytochemicals?

The recent increase in bacterial resistance to antibiotics has motivated the resurgence of the study of natural antimicrobial products. For centuries, plants have been recognized for their bactericidal properties. However, in the last two decades, it has been reported that several plant derived metabolites at growth subinhibitory concentrations also tend to have anti-virulence properties, since they reduce the expression of factors that cause damage and the establishment of pathogenic bacteria. In this area of study, plants have been positioned as one of the main natural sources of anti-virulence molecules, but only a small portion of the plant species that exist have been investigated. Also, anti-virulence studies have been primarily focused on analyzing the ability of extracts and compounds to inhibit quorum sensing and biofilms formation in vitro. This mini-review discusses the current panorama, the trends in the study of anti-virulence phytochemicals, as well as their potential for the development of antibacterial therapies.

Virulence Properties of GI-23 Infectious Bronchitis Virus Isolated in Poland and Efficacy of Different Vaccination strategies

Infectious bronchitis virus (IBV) is one of the most important poultry pathogens, leading significant economic losses worldwide. IBV is characterised by highly genetic, serotype, and pathotypic variability. Despite extensive immunoprophylaxis strategies, the emergence of new genetic lineages is frequently observed in the field, causing disease control to be more complicated. In the last decade, the spread of variants assigned to the GI-23 lineage of IBV (formerly known as Var2) started from Middle-Eastern countries and reached Europe in the last few years. Recently, the introduction and fast spread of Var2-like IBVs in Poland was reported. In this study, the virulence properties and efficacy of different vaccination programmes were evaluated against infection with the IBV GI-23 strain gammaCoV/Ck/Poland/G052/2016. The pathogenicity of the Var2 isolate was conducted in one-day-old and three-week-old SPF chickens and showed that the course of the disease is age dependent. Seven vaccination programmes using Mass, 793B, QX alone or in combination, and Var2 live vaccines were tested against the GI-23 infectious bronchitis virus challenge. All groups were scored according to the ciliostasis test at 5 days post challenge. Two immunoprophylaxis strategies generated full protection against gammaCoV/Ck/Poland/G052/2016 infection—Var2 and Mass used in one-day-old chickens boosted by a combination of the QX and 793B vaccine (both with a ciliostasis score of 0 and 100% protection).

#17: DNA Methylation in Streptococcus pyogenes Promotes M-Protein Expression and Enhances Epithelial Cell Adherence and Persistence on a Mucosal Surface

Background DNA methylation has been extensively studied as a regulator of gene expression among eukaryotes, but the regulatory role for DNA methylation has been far less studied in bacterial pathogens. Streptococcus pyogenes, or Group A Streptococcus, is an important bacterial pathogen of children. Our group has recently shown that S. pyogenes utilizes DNA methylation at N6-methyladenine (m6A) as a regulatory mechanism, modulating gene transcription and influencing the expression of several genes recognized as potential virulence factors. Our goal was to further explore how DNA methylation impacts virulence properties of S. pyogenes through adherence to epithelial cells and persistence on a mucosal surface. Methods S. pyogenes strains HSC12 (M14), MEW123 (M28), and MEW431 (M4) were modified by in-frame genetic deletion of a 3-gene operon encoding the only Type-I Restriction-Modification locus, resulting in mutant strains lacking the majority of m6A base modifications (ΔRSM). S. pyogenes parent and ΔRSM mutant strains were subjected to transcriptional profiling by RT–PCR and RNA-Seq analysis. Adherence rates of streptococci to D562 human pharyngeal epithelial cells and VKE6E7 human vaginal epithelial cells were assessed. A murine vaginal mucosa colonization model was used to monitor streptococcal mucosal persistence. Results The ΔRSM mutants of all three strains lacked essentially all m6A DNA base modifications by dot-blot with anti-m6A antibody and PacBio™ sequencing with methylation analysis. Transcriptional profiling demonstrated that a limited subset of ~20 genes was strongly down-regulated in all of the ΔRSM mutant strains, most notably genes in the core Mga regulon involved in tissue adherence and evasion of the host immune response, including the M protein (emm gene). The ΔRSM mutants of all 3 strains were attenuated for adherence to human respiratory and vaginal epithelial cells compared with parent strains or complemented mutant strains. The HSC12 and MEW431 ΔRSM mutant strains exhibited significantly decreased bacterial burdens over time compared with parent strains in the murine mucosal carriage model. The bacterial burdens of strain MEW123 and its ΔRSM mutant were not significantly different in the murine mucosal carriage model. Expression of R28, an adhesin specifically promoting adherence to vaginal epithelial cells, was not altered in the MEW123 ΔRSM mutant, which may explain the continued persistence of this strain in the murine model. Conclusions DNA methylation influences gene expression at the transcriptional level in S. pyogenes and affects virulence properties in both in vitro and in vivo models of infection. We report that methylation promotes activation of several important virulence factors, including the M protein and other members of the Mga regulon, and influences epithelial cell adherence and streptococcal persistence on a mucosal surface. DNA methylation appears to be an important contributor to bacterial physiology and pathogenesis. Future work will identify the interaction of m6A base modifications and transcriptional regulatory proteins.