Production Of Bacterial Toxins Research Articles

Woman’s microbiome and obstetrical and perinatal risks: what do they have in common?

The article is devoted to the review of modern scientific publications about the microbiome of a woman and its importance in obstetric and perinatal practice. The composition of the microbiome is changed both in the process of human evolution and personally and in different periods of a person’s life. However, on the other hand, the microbiome is influenced by the specific environment in which a person lives. It consists of a certain collection of genomes of all microorganisms. Complications during pregnancy occur frequently, according to statistics – in every sixth pregnant woman, and pose a danger to the health of the mother and child.During pregnancy, the richness and diversity of the vaginal microbiome decreases, and different species of Lactobacillus play a dominant role. The microbiome stability is hypothesized to be associated with higher levels of estrogen concentration, absence of menstruation, and modification of cervical and vaginal fluids. During an uncomplicated pregnancy, the taxonomic composition of the vaginal microbiota remains stable with the exception of the period before labor, when there is an increase in microbial diversity. This makes the vaginal microbiome similar to that of a non-pregnant woman and is believed to be a trigger for the labor process to begin.The recent studies have determined a relationship between changes in the microbiome during pregnancy and the occurrence of complications in these women. Any change or disturbance in the microbiome balance can be involved in inflammatory processes, which can potentially have adverse effects on the course of pregnancy. A major interaction between the oral microbiome and preeclampsia involves the production of nitrogen derivatives, especially nitric oxide (NO). NO is produced from L-arginine via NO synthases (NOS), and is involved in vascular processes, especially vasodilation and tissue protection. Also, NO is indirectly involved in the processes that occur in the presence of chronic cardiovascular diseases, including hypertension and preeclampsia.In recent years, scientists have begun actively to study a correlation between changes in the gut microbiome and various nosologies regarding gestational diabetes. There is not much of this data at the moment. The gut microbiome is known to modulate insulin resistance and the inflammatory response, and changes in the microbiome may be associated with metabolic diseases. It is hypothesized that changes in the gut microbiome may lead to metabolic diseases through several mechanisms: abnormal intestinal permeability, increased absorption of lipopolysaccharide, abnormal production of short-chain fatty acids, altered conversion of primary bile acids, and enhanced production of bacterial toxins (e.g., trimethylamine-N-oxide).During full-term pregnancy, the “dynamic stability” of the vaginal microbiome is described as a higher concentration of Lactobacillus species starting at 20 weeks of gestation due to increased glycogen availability and a less complex and diverse microflora. This condition may be due to the lack of cyclical hormonal changes during pregnancy. Lactobacillus and small bacterial diversity are thought to be critical factors for the initiation of labor at the end of the pregnancy.Future therapeutic strategies are likely to be applied to modulate the composition of the microbiome, including the use of pro- and prebiotics and dietary modification. However, further research is needed to identify specific tools that can be used to develop personalized therapeutic approaches for individualized prevention and treatment.

Эффективность применения Lactobacillus reuteri в клинической практике

This paper addresses the primary aspects of developing gut microbiota and the immune system and the role of gut microbiocenosis in this process. Optimal gut colonization and adequate immune response are critical factors in developing tolerance to commensal microbes and anti-infectious protection. The authors highlight various prenatal, neonatal, and postnatal factors which prevent normal colonization of gastrointestinal mucosa. One of the methods to restore the qualitative and quantitative composition of gut microbiota are probiotics. Probiotics demonstrating antagonistic activity for pathogens compete with these pathogens for the adhesion to mucosal epithelium and nutrients, thereby inhibiting the production of bacterial toxins, modulating the functions of the immune system, improving gut microbiocenosis, maintaining the integrity of the gastrointestinal mucosal barrier, and controlling gut inflammation. Probiotics are a heterogeneous group of living bacteria with species- and strain-specific properties. For example, Lactobacillus reuteri is an effective probiotic commonly prescribed in premature babies, children with acute gastroenteritis, and infantile colic. KEYWORDS: gut microbiota, microbiocenosis, premature, C-section, probiotics, bacteria, immune system, infantile colic, Lactobacillus reuteri. FOR CITATION: Komarova O.N. Efficacy of Lactobacillus reuteri in clinical practice. Russian Journal of Woman and Child Health. 2021;4(3):277–283 (in Russ.). DOI: 10.32364/2618-8430-2021-4-3-277-283.

Kampo medicines suppress the production of exfoliative toxins causing impetigo in Staphylococcus aureus

An alternative approach, such as antivirulence therapy that modulates the production of bacterial toxins or virulence factors, is necessary to tackle the emergence of antimicrobial-resistant strains. Here, we investigated the potential antivirulence effects of seven Kampo medicines (Jumihaidokuto, Eppikajutsuto, Jizusoippo, Shomakakkonto, Sammotsuogonto, Hainosankyuto and Inchinkoto) against exfoliative toxin (ET)-positive Staphylococcus aureus, which is the major causative agent of impetigo. A growth inhibition assay showed that all of the selected Kampo medicines inhibited the growth of S.aureus at 1/5 (2.5mg/mL) or less of the conventionally used concentrations. Among these, Jizusoippo and Inchinkoto (0.25-1mg/mL) suppressed the production of ET without inhibiting the bacterial growth. Furthermore, Jizusoippo and Inchinkoto significantly suppressed the expression of ET genes in a concentration-dependent manner. Our findings strongly suggest, for the first time, that Kampo medicines, especially Jizusoippo and Inchinkoto, have the potential to serve as antivirulence agents against skin infections caused by S.aureus by suppressing the production of ET.

Airway Microbiota as a Modulator of Lung Cancer.

Recent research on cancer-associated microbial communities has elucidated the interplay between bacteria, immune cells, and tumor cells; the bacterial pathways involved in the induction of carcinogenesis; and their clinical significance. Although accumulating evidence shows that a dysbiotic condition is associated with lung carcinogenesis, the underlying mechanisms remain unclear. Microorganisms possibly trigger tumor initiation and progression, presumably via the production of bacterial toxins and other pro-inflammatory factors. The purpose of this review is to discuss the basic role of the airway microbiome in carcinogenesis and the underlying molecular mechanisms, with the aim of developing anticancer strategies involving the airway microbiota. In addition, the mechanisms via which the microbiome acts as a modulator of immunotherapies in lung cancer are summarized.

Shirazi thyme (Zataria multiflora Boiss) and Rosemary (Rosmarinus officinalis) essential oils repress expression of sagA, a streptolysin S-related gene in Streptococcus iniae

The pathogenicity of Streptococcus iniae in fish is depending on the secreted virulence factors, such as streptolysin S (SLS). It is demonstrated that some plant essential oils can affect the production of bacterial toxins. In this study, broth macrodilution method was first used to determine minimum inhibitory concentrations (MICs) of Rosmarinus officinalis and Zataria multiflora essential oils against S. iniae. Hemolysin assay and real-time PCR analysis were then conducted to investigate the effect of subinhibitory concentrations of the essential oils on SLS major encoding gene, sagA, in two isolates of S. iniae. The obtained data showed that both R. officinalis and Z. multiflora decreased the hemolytic activity of S. iniae supernatant, dose-dependently. However, SLS was not inactivated when the essential oils were added to the bacterial culture supernatant. The transcription of sagA was significantly down-regulated during treatment of the bacterial isolates with subinhibitory concentrations of the essential oils. This data suggested that both R. officinalis and Z. multiflora could be advantageous for the control of streptococcosis caused by S. iniae, via inhibition the growth and repression the production of SLS.

Comment on: Linezolid use in sepsis due to methicillin-susceptible Staphylococcus aureus

De Gascun and colleagues report on a case of methicillinsusceptible Staphylococcus aureus (MSSA) sepsis treated successfully with linezolid after initial failure of a triple regimen of apparently appropriate antibiotics. They ascribe the observed efficacy of linezolid to an anti-toxin effect of the antibiotic. Linezolid acts by inhibiting bacterial protein synthesis, and it, therefore, blocks the production of bacterial toxins and other virulence factors. The suggested anti-toxin effect is attractive to explain the observed efficacy of linezolid. Yet, linezolid was initiated at a time when all cultures were negative, whereas toxin production requires a bacterial source to be present. De Gascun and colleagues looked for such a source but were unable to find one. Yet, presence of a source with access difficulties for the initial triple antibiotic regimen but not for linezolid seems possible. Such a source might explain the negative blood cultures (elimination of bacteria leaking from the source into the bloodstream) as well as the worsening symptoms of sepsis (continued toxin release into the bloodstream from bacteria surviving in the source) observed during treatment with the initial triple antibiotic regimen. Superior penetration of linezolid into the source on the other hand, in combination with an anti-toxin effect, might then have prevented further toxin release into the bloodstream, with regressing sepsis symptoms and eventual recovery as a result. Even if it seems possible to link the patient’s recovery to linezolid, multiple factors can interfere with this evolution. Aggressive initial treatment with drugs such as drotrecogin alpha (activated) or substitutive doses of corticosteroids could, by themselves, have improved the patient’s condition. A randomized trial of conservative therapy versus linezolid would be of the highest interest to confirm its use in this setting. Widespread use could induce S. aureus resistance.

Recombinant production of bacterial toxins and their derivatives in the methylotrophic yeast Pichia pastoris

The methylotrophic yeast Pichia pastoris is a popular heterologous expression host for the recombinant production of a variety of prokaryotic and eukaryotic proteins. The rapid emergence of P. pastoris as a robust heterologous expression host was facilitated by the ease with which it can be manipulated and propagated, which is comparable to that of Escherichia coli and Saccharomyces cerevisiae. P. pastoris offers further advantages such as the tightly-regulated alcohol oxidase promoter that is particularly suitable for heterologous expression of foreign genes. While recombinant production of bacterial toxins and their derivatives is highly desirable, attempts at their heterologous expression using the traditional E. coli expression system can be problematic due to the formation of inclusion bodies that often severely limit the final yields of biologically active products. However, recent literature now suggests that P. pastoris may be an attractive alternative host for the heterologous production of bacterial toxins, such as those from the genera Bacillus, Clostridium, and Corynebacterium, as well as their more complex derivatives. Here, we review the recombinant production of bacterial toxins and their derivatives in P. pastoris with special emphasis on their potential clinical applications. Considering that de novo design and construction of synthetic toxin genes have often been necessary to achieve optimal heterologous expression in P. pastoris, we also present general guidelines to this end based on our experience with the P. pastoris expression of the Bacillus thuringiensis Cyt2Aa1 toxin.

A Novel Peptide Screened by Phage Display Can Mimic TRAP Antigen Epitope against Staphylococcus aureus Infections

Staphylococcus aureus is a major human pathogen. Pathogenic effects are largely due to production of bacterial toxins, whose synthesis is controlled by an mRNA molecule termed RNAIII. The S. aureus protein called RAP (RNAIII-activating protein) is secreted and activates RNAIII production by inducing the phosphorylation of its target protein TRAP (target of RAP). Antibodies to TRAP have been shown to suppress exotoxin production by S. aureus in vitro, suggesting that TRAP may be a useful vaccine target site. Here we showed that a peptide TA21 was identified by screening a phage display library using anti-TRAP antibodies. Mice vaccinated with Escherichia coli engineered to express TA21 on their surface (FTA21) were protected from S. aureus infections, using sepsis and cellulitis mice models. By sequence analysis, it was found that the TA21 is highly homologous to the C-terminal sequence of TRAP which is conserved among S. aureus and Staphylococcus epidermidis, suggesting that peptide TA21 may be a useful broad vaccine to protect from infection caused by various staphylococcal strains.

Pathophysiology of reactive airway disease and sinusitis.

The association between asthma and sinusitis was recognized more than a century ago. Since 1980, several studies have documented that severe asthma improved after coexisting sinusitis was effectively treated either medically or surgically. Because the mechanism relating sinusitis to asthma is not known, several theories have been proposed: 1) aspiration of infected sinus secretions into the lungs during sleep, 2) enhanced vagal stimulation in the infected sinus producing direct bronchospasm, 3) bronchospasm from excessive airway drying from mouth breathing, 4) production of bacterial toxins that induce partial beta blockade, and 5) production in the infected sinus of cytokines and bronchoconstrictive mediators. There are data to support each of these hypotheses, and any or all of them may be operative. In view of recent demonstrations of activated lymphocytes and eosinophils in asthmatic airways, it is intriguing that biopsies of chronic hypertrophic sinusitis have revealed increased numbers of eosinophils and increased levels of granulocyte-macrophage colony stimulating factor, interleukin-3, and interleukin-5 compared to control tissue. These findings suggest that sinusitis might induce asthma by stimulating eosinophil production and activation and thereby supplying peptidoleukotrienes (LTC4 and LTD4) and other asthmagenic eosinophil products.

Relevance, pathogenicity and virulence of microorganisms in implant related infections

It is impossible to imagine modern medicine today without indwelling devices of various kinds. The time that these implants or prostheses remain in the patient's body can vary from a few hours, e.g. intravenous catheter, to his entire life, e.g. hip prosthesis, heart valve. Besides the indisputable use and advantages of this type of medical intervention for the patient, e.g. saving his life or improving its quality, the associated complications should not be overlooked. One of the most frequent and significant complications of implant surgery is the manifestation of infection in the tissue around the implant. That infection occurs is not surprising since the indwelling devices predispose to bacterial and mycotic infection on the one hand and impede its eradication on the other. The consequences of infection for the patient may mean the loss of regained mobility and independence, hospitalization for sepsis, or even death. Microbes per se are not necessarily pathogenic, however, there are numerous virulence factors which affect the degree of pathogenicity of the microorganisms. These include, for example, various enzymes, (e.g. catalase, hyaluronidase, collagenase and other proteases), and specific surface structures, e.g. the polysaccharide capsules of pneumococci or the lipopolysaccharides of Gram negative bacteria, and the production of bacterial toxins, e.g. leucozidin, streptolysine. The strategies which the pathogenic bacteria employ in their efforts to occupy the host include adherence, penetration and multiplication, antiphagocytosis and serum resistance, the formation of siderophores, antiimmunity, and cell and tissue damage. An attempt will be made here to present an overview of this multifactorial event in which the host obviously plays an important role.

Fermented foods and food safety

An evaluation is presented of risk factors associated with fermented foods, in comparison with fresh or alternatively processed foods. Cases of microbial food-borne infection have been reported in association with fresh cheese, sausages, fermented fish and fermented cereals. Another risk involves microbial food intoxications due to mycotoxin contaminated raw materials, production of bacterial toxins or possible mycotoxin production by fungal innoculants. In addition, toxic by-products of fermentation may be produced including ethyl carbamate and biogenic amines. From a food processing point of view, major risk enhancing factors are the use of contaminated raw materials, lack of pasteurization, and use of poorly controlled natural fermentations. Also sub-optimal fermentation starters and inadequate storage and maturation conditions as well as consumption without prior cooking may reduce the safety of fermented foods. In addition to ensuring adequate processing conditions, the development of non-toxigenic starters with ability to antogonize pathogenic microorganisms and to degrade toxic substances needs continued attention.

Eugenol Mediated Morphological Changes in Bacillus Subtilis

Linezolid is active against a broad range of gram-positive pathogens and has the potential to also affect production of bacterial toxins and host immune function.To assess the evidence for direct effects of linezolid on bacterial toxin synthesis and modulation of host immune responses.Literature searches were performed of the PubMed and OVID databases. Reviews and non–English language articles were excluded. Articles with information on the effect of linezolid on bacterial toxin synthesis and immune responses were selected for further review, and data were summarized.Substantial in vitro evidence supports effects of linezolid on bacterial toxin production; however, the strength of the evidence and the nature of the effects are mixed. In the case of Staphylococcus aureus, repeated observations support the inhibition of production of certain staphylococcal toxins (Panton-Valentine leukocidin, protein A, and α- and β-hemolysin) by linezolid, whereas only solitary reports indicate inhibition (toxic shock syndrome toxin-1, coagulase, autolysins, and enterotoxins A and B) or stimulation (phenol-soluble modulins) of toxin production by linezolid. In the case of Streptococcus pyogenes, there are solitary reports of linezolid inhibition (protein M, deoxyribonuclease, and streptococcal pyrogenic exotoxins A, B, and F) or stimulation (immunogenic secreted protein 2 and streptococcal inhibitor of complement-mediated lysis) of toxin production, whereas published evidence for effects on streptolysin O production is conflicting. In vitro data are limited, but suggest that linezolid might also have indirect effects on host cytokine expression through inhibition of bacterial production of toxins. In vivo data from preclinical animal studies and a single clinical study in humans are limited and equivocal insofar as a potential role for linezolid in modulating the host inflammatory response; this is due in part to the difficulty in isolating antimicrobial effects and toxin synthesis inhibitory effects of linezolid from any secondary effects on host inflammatory response.Available evidence supports the possibility that linezolid can inhibit, and in some cases stimulate, toxin production in clinically relevant pathogens. However, more research will be needed to determine the potential clinical relevance of those findings for linezolid.

Pathogenesis of Pseudomonas aeruginosa ocular diseases.

The gram-negative opportunistic bacterial pathogen, Pseudomonas aeruginosa, is an important etiologic agent of a variety of infectious diseases affecting the eye and surrounding tissues. The number of clinical studies and studies with mouse, guinea pig, and rabbit models of Pseudomonas-induced ocular disease has increased markedly in recent years, and this research has led to our improved understanding of factors relating to the pathogenesis and management of the diseases. Factors that predispose to ocular infections with P. aeruginosa include (1) trauma to the cornea with, or implantation of, foreign bodies or substances contaminated with the bacteria; (2) the presence of preexisting ocular disease; (3) immunosuppressive chemotherapy; and (4) presumed immunoincompetency in premature infants. The results of studies with animal models support the idea that the severe corneal damage that occurs during pseudomonas keratitis is caused by the production of bacterial enzymes and toxins that injure or kill the cellular components and/or degrade the extracellular matrix of the cornea and by bacterial product-mediated release or activation of cornea-degrading enzymes from corneal cells and/or from polymorphonuclear leukocytes infiltrating the infected cornea.

Extracellular Secondary Metabolite Production by the Marine Dinoflagellate Prorocentrum minimum in Culture

Marine dinoflagellates produce extracellular secondary metabolites that may play a role in the ecology of the producing species. The concentration of one such external metabolite, 1-(2,6,6-trimethyl-4-hydroxycyclohexenyl)-1, 3-butanedione, produced by the marine dinoflagellate Prorocentrum minimum, was determined quantitatively during exponential growth and during senescence in phosphate-starved batch cultures. The pattern of production is similar to the production of many bacterial toxins. There was little production of the β-diketone during the exponential growth period and highest production occurred within 1 wk after cessation of cell division. About 50% of the total β-diketone produced was excreted on a single day, 6 d after phosphate became limiting to growth. Cell lysis or photodestruction of carotenoids do not appear to be the source of this compound.Key words: antibiotic, dinoflagellate, organic excretion, Prorocentrum minimum, secondary metabolite, phosphate starvation

Effect of iron on growth and toxin production byClostridium botulinum type A

The kinetics of growth and toxin production by the Hall strain ofClostridium botulinum type A was examined in the presence of various concentrations of iron (0.1 to 10.1 μg/ml, 1.8 to 182 μM) in a chemically defined medium. At concentrations below 0.5 μg/ml, iron insufficiency limited the growth of the organism. The maximum amount of toxin produced varied by only twofold (6×105 to 1.2×106 mouse median lethal doses/ml per A540 unit) over the 100-fold range of iron concentrations used. High concentrations of iron did not reduce the elaboration of botulinum toxin, in contrast with its marked inhibitory effects on the production of many bacterial toxins. Iron is unlikely to be a regulatory effector for the formation of botulinum toxin by the Hall strain of type A.

The Relation of the Reaction of the Culture Medium to the Production of Haemolysin

Ever since artificial media have been used for the cultivation of micro-organisms, the question as to what is the best reaction—that is the degree of acidity or alkalinity—has been a moot point. It has been assumed gratuitously that there is an optimum reaction which is the same for all the common bacteria met with in the laboratory. In recent years however some attempts have been made to settle the question definitely, notably by Eyre and Deelemann. On enquiring what reaction of medium was adopted in six different London laboratories, Eyre found that very divergent standards were used, ranging from 20 units of acidity to 10 units of alkalinity on his scale. (20 units of acidity implies that 20 c.c. of normal alkali must be added to each litre to make it neutral to phenolphthalein. In the case of alkalinity the indicated number of c.c. of normal acid must be added.) The importance of having a definite reaction had until recently not impressed itself upon the majority of bacteriologists. The possibility that although many organisms may grow on media of comparatively widely differing reactions, yet only one of these reactions may be suitable for the growth of a more delicate kind, had been overlooked. Consequently they failed to grow bacteria which by careful adjusting of the reaction of the medium could be readily cultivated. Martin (1910), for example, has lately pointed out the ease with which gonococcus can be made to grow on serum agar if the reaction is carefully adjusted. In later years the subject has assumed still more importance in connection with the production of bacterial toxins, which have been submitted to a large amount of investigation. In the production of diphtheria toxin it was soon recognised that bouillon containing more alkali than is usually employed for ordinary bacteriological work, yielded the most toxin, and even various devices were invented to avoid the initial production of acid which usually takes place as the consequence of bacterial growth in a sugar-containing medium. Madsen (1896) has made a thorough examination of the factors governing the production of diphtheria toxin. By following the reaction of a growing culture from day to day he found two different types of growth occur,—one in which the medium increases in acidity without abatement, and such cultures are atoxic; in the other the primary increase in acidity is followed by a decrease, and subsequent increase in alkalinity. These cultures are sometimes toxic. The two conditions seemed to have relation to the amount of alkali added in the preparation of the bouillon, in that a strongly alkaline medium gave an alkaline end reaction while a less alkaline medium gave sometimes an acid and sometimes an alkaline end reaction.