Anaerobic Growth Research Articles

Anaerobic growth and drug susceptibility of versatile fungal pathogen Scedosporium apiospermum

Although severe cases of invasive mycoses of different hypoxic and anoxic body parts have been reported, growth and drug susceptibility of fungal pathogens under anaerobic conditions remains understudied. The current study evaluated anaerobic growth potential and drug susceptibility of environmental Scedosporium apiospermum isolates under aerobic and anaerobic conditions. All tested strains showed equivalent growth and higher sensitivity to tested antifungal drugs under anaerobic conditions with lower minimum inhibitory concentration (MIC) as compared to aerobic conditions. Antifungal azoles were effective against isolates under both aerobic and anaerobic conditions. Most strains were resistant to antifungal echinocandins and polyenes under aerobic conditions but exhibited sensitivity under anaerobic conditions. This study provides evidence that resistance of S.apiospermum to antifungal drugs varies with oxygen concentration and availability and suggests re-evaluating clinical breakpoints for antifungal compounds to treat invasive fungal infections more effectively.

Characterization of two novel Fe(III)-reducing and electrogenic bacteria, Shewanella ferrihydritica sp. nov. and Shewanella electrica sp. nov., isolated from mangrove sediment.

Three novel strains in the genus Shewanella, designated A3AT, C31T and C32, were isolated from mangrove sediment samples. They were facultative anaerobic, Gram-stain-negative, rod-shaped, flagellum-harbouring, oxidase- and catalase-positive, electrogenic and capable of using Fe(III) as an electron acceptor during anaerobic growth. Results of phylogenetic analysis based on 16S rRNA gene and genomic sequences revealed that the strains should be assigned to the genus Shewanella. The 16S rRNA gene similarity, average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the isolates and their closely related species were below the respective cut-off values for species differentiation. The 16S rRNA gene similarity, ANI and dDDH values between strains C31T and C32 were 99.7, 99.9 and 99.9 %, respectively, indicating that they should belong to the same genospecies. Based on polyphasic taxonomic approach, two novel species are proposed, Shewanella ferrihydritica sp. nov. with type strain A3AT (GDMCC 1.2732T=JCM 34899T) and Shewanella electrica sp. nov. with type strain C31T (GDMCC 1.2736T=JCM 34902T).

Amine-recognizing domain in diverse receptors from bacteria and archaea evolved from the universal amino acid sensor

Bacteria possess various receptors that sense different signals and transmit information to enable an optimal adaptation to the environment. A major limitation in microbiology is the lack of information on the signal molecules that activate receptors. Signals recognized by sensor domains are poorly reflected in overall sequence identity, and therefore, the identification of signals from the amino acid sequence of the sensor alone presents a challenge. Biogenic amines are of great physiological importance for microorganisms and humans. They serve as substrates for aerobic and anaerobic growth and play a role of neurotransmitters and osmoprotectants. Here, we report the identification of a sequence motif that is specific for amine-sensing sensor domains that belong to the Cache superfamily of the most abundant extracellular sensors in prokaryotes. We identified approximately 13,000 sensor histidine kinases, chemoreceptors, receptors involved in second messenger homeostasis and Ser/Thr phosphatases from 8,000 bacterial and archaeal species that contain the amine-recognizing motif. The screening of compound libraries and microcalorimetric titrations of selected sensor domains confirmed their ability to specifically bind biogenic amines. Mutants in the amine-binding motif or domains that contain a single mismatch in the binding motif had either no or a largely reduced affinity for amines. We demonstrate that the amine-recognizing domain originated from the universal amino acid-sensing Cache domain, thus providing insight into receptor evolution. Our approach enables precise "wet"-lab experiments to define the function of regulatory systems and therefore holds a strong promise to enable the identification of signals stimulating numerous receptors.

Biohydrogen production of a halophytic cyanobacteria Phormidium keutzingium and activated sludge co-culture using different carbon substrates and saline concentrations

Hydrogen (H2) production using a biological pathway such as anaerobic digestion suffers limitations in the survival of microorganisms. Usually, microalgae are used as feedstock but the acidic pH of digestate ruptures the cell wall of microalgae resulting in dead cellular debris. Whereas some cyanobacteria (blue-green microalgae) are very resilient and tolerant to stressful environments such as hypersaline conditions. Therefore, in this study, a microbial consortium (co-culture) of cyanobacteria Phormidium keutzingianum and activated sludge bacteria (ASB) was established to generate H2 production from waste resources. Different co-culturing ratios 2:1, 1:1, and 1:2 v/v (P. keutzingianum: ASB) were analyzed for H2 production with glucose, sorbitol, and mannitol as carbon substrates. In addition, the effect of different concentrations (0, 10, and 20 g/L) of salt (NaCl) on H2 production was also tested. Results indicated that the amount of cumulative H2 produced changed significantly by varying the carbon substrates. Glucose-supplemented co-culture produced the lowest amount of H2 at 278 mL/L as compared to 980 and 562 mL H2/L in sorbitol and mannitol-supplemented co-cultures, respectively. The addition of NaCl negatively affected H2 production by increasing the salinity level from 0 to 20 g/L, and the cumulative H2 reduced from 980 to 176.8 mL/L and 562 to 333 mL/L in sorbitol and mannitol-supplemented co-culture, respectively. Sorbitol showed cyanobacterial growth in terms of chlorophyll from 600 to 1200 μg/L and optical density from 1 to 12 at λ 620 nm. Total organic carbon (TOC) in sorbitol supplemented co-cultures also increased to the peak 5.7, 6.7, and 7.7 g/L in 2:1, 1:2, and 1:1 v/v ratios, respectively, indicating anaerobic growth. Hence, this study signifies that sorbitol appeared to be the significant carbon substrate that helped cyanobacteria grow under anaerobic conditions resulting in higher H2 production. Moreover, cyanobacteria are more tolerant to stressful environments such as hypersaline and acidic conditions compared to microalgae.

Influence of cheese making process on STEC bacteriophage release.

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens implicated in diseases including hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC). The main virulence factor are Shiga toxins; their production and secretion are by-products of the expression of late genes of prophages upon sub-lethal environmental stimuli exposure. Hence, the lysogenic prophage after a stress switch to lytic cycle spreading the Stx phages. In the present study, 35 STEC were screened for the presence and the ability to release Shiga toxin-encoding bacteriophages. Three bacterial strains showed signals of prophage presence both in plate and in PCR. Subsequently, these bacterial strains were subjected to stressors that simulate cheese manufacturing conditions: NaCl (1, 1.5 and 2% w/v), lactic acid (0.5, 1.5 and 3% v/v), anaerobic growth, pasteurization (72°C for 15 s), UV irradiation. The ability to release prophage was evaluated by Real Time qPCR. Induction of the prophages showed that the addition of NaCl at 1.5 and 2% significantly increased viral release compared to control. Conversely, the addition of lactic acid had a significant repressive effect. The other applied stressors had no significant effect in phage release according to the experimental conditions adopted.

Co-cultivation of Saccharomyces cerevisiae strains combines advantages of different metabolic engineering strategies for improved ethanol yield

Glycerol is the major organic byproduct of industrial ethanol production with the yeast Saccharomyces cerevisiae. Improved ethanol yields have been achieved with engineered S. cerevisiae strains in which heterologous pathways replace glycerol formation as the predominant mechanism for anaerobic re-oxidation of surplus NADH generated in biosynthetic reactions. Functional expression of heterologous phosphoribulokinase (PRK) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes enables yeast cells to couple a net oxidation of NADH to the conversion of glucose to ethanol. In another strategy, NADH-dependent reduction of exogenous acetate to ethanol is enabled by introduction of a heterologous acetylating acetaldehyde dehydrogenase (A-ALD). This study explores potential advantages of co-cultivating engineered PRK-RuBisCO-based and A-ALD-based strains in anaerobic bioreactor batch cultures. Co-cultivation of these strains, which in monocultures showed reduced glycerol yields and improved ethanol yields, strongly reduced the formation of acetaldehyde and acetate, two byproducts that were formed in anaerobic monocultures of a PRK-RuBisCO-based strain. In addition, co-cultures on medium with low acetate-to-glucose ratios that mimicked those in industrial feedstocks completely removed acetate from the medium. Kinetics of co-cultivation processes and glycerol production could be optimized by tuning the relative inoculum sizes of the two strains. Co-cultivation of a PRK-RuBisCO strain with a Δgpd1 Δgpd2 A-ALD strain, which was unable to grow in the absence of acetate and evolved for faster anaerobic growth in acetate-supplemented batch cultures, further reduced glycerol formation but led to extended fermentation times. These results demonstrate the potential of using defined consortia of engineered S. cerevisiae strains for high-yield, minimal-waste ethanol production.

Otogenic Cerebellar Abscess with Polymicrobial Anaerobic Infection in a Young Female- A Rare Presentation.

Brain abscess is a serious clinical condition caused by a localized collection of pus within the brain tissue. This typically occurs as a result of an infection that originates from a nearby area, such as an ear, sinus, or dental infection, or an infection in the bloodstream. Streptococcus and Staphylococcus species are the most common organisms implicated in brain abscesses. Apart from aerobic growth, cases of mixed infections of both aerobic and anaerobic organisms are also commonly reported in the literature. Herein we report a 23-year-old immunocompetent female with chronic otitis media who presented with cerebellar abscess where the aerobic growth was sterile and anaerobic culture revealed pure growth of dual anaerobes viz… Peptostreptococcus and Bacteroides thetaiotaomicron. This case highlights the importance of prompt diagnosis and management of polymicrobial anaerobic infection in cases of brain abscess.

NADH dehydrogenase is the primary target for the bactericidal effect of CORM-2 in Shewanella oneidensis

Shewanella oneidensis is a good model for investigating the bactericidal effects of chemical agents. In this study, the effects of tricarbonyldichlororuthenium dimer (CORM-2) on the aerobic and anaerobic growth of S. oneidensis were studied, and its bactericidal mechanisms were elucidated. CORM-2 (5 µM) significantly inhibited aerobic and anaerobic respiration. Growth potential tests showed that mutants ΔkatB, ΔoxyR, ΔccmF, and Δcrp and mutants that deleted each cytochrome c-encoding gene exhibited sensitivity to CORM-2 similar to that of the wild-type strain MR-1. Enzymatic analyses showed that cytochrome oxidase, catalase and cysteine desulfurase were activated by CORM-2, while nitrite reductase, nitrate reductase, sulfite reductase, thiosulfate reductase, peroxidase and NADH dehydrogenase were inhibited by CORM-2, and no significant changes were found in the activities of superoxide dismutase and aconitase. Promoter activity assays showed that cco, cyd, cox, katB, sirA and psrA were repressed by CORM-2. Sulfide alleviated the bactericidal effect of CORM-2 and protected NADH dehydrogenase from CORM-2 inhibition. Thus, oxidative stress and cytochrome oxidase inactivation are not the primary reasons for the bactericidal effect of CORM-2, and NADH dehydrogenase is the main target in S. oneidensis. The bactericidal effect of CORM-2 is caused by the toxicity of Ru2+, not by carbon monoxide.

Morpho-physiological characterization of bacterial grain rot in rice seed from Gowa Regency, South Sulawesi

Bacterial Grain Rot caused by Burkholderia glumae is an important disease of rice. In South Sulawesi, this seed-borne pathogen has been detected in several places. There were some reports from the farmers regarding rice yield loss due to this disease. This study aimed to isolate and characterize morpho-physiologically bacterium causing grain rot of rice in the main rice-producing areas of Gowa Regency, South Sulawesi. Samples were obtained from 10 districts. Several grains of rice were isolated and grown in King’s B medium. Morphological characteristics were determined by the color, form, edge, and elevation of colonies. KOH solubility, catalase test, anaerobic growth, toxoflavin production assay, production of fluorescent pigment, and colony color on YDC medium were performed to determine physiological characteristics. 1 isolate from each area was found which has similar morphological traits to B. glumae. Colonies that were yellow, yellowish white, creamy white, and grayish white, with a circular form, entire edge, and convex elevation. The result of physiological characterization showed that all isolates tested positive for KOH solubility and catalase test as well. All isolates showed negative reactions for anaerobic growth, production of fluorescent pigment, and colony color on YDC medium. 5 isolates were able to produce yellow pigment (toxoflavin), so it can be concluded that all of the isolates that have been characterized morpho-physiologically are presumably confirmed as B. glumae.

The Campylobacter concisus BisA protein plays a dual role: oxide-dependent anaerobic respiration and periplasmic methionine sulfoxide repair.

Campylobacter concisus is an excellent model organism to study respiration diversity, including anaerobic respiration of physiologically relevant N-/S-oxides compounds, such as biotin sulfoxide, dimethyl sulfoxide, methionine sulfoxide (MetO), nicotinamide N-oxide, and trimethylamine N-oxide. All C. concisus strains harbor at least two, often three, and up to five genes encoding for putative periplasmic Mo/W-bisPGD-containing N-/S-oxide reductases. The respective role (substrate specificity) of each enzyme was studied using a mutagenesis approach. One of the N/SOR enzymes, annotated as "BisA", was found to be essential for anaerobic respiration of both N- and S-oxides. Additional phenotypes associated with disruption of the bisA gene included increased sensitivity toward oxidative stress and elongated cell morphology. Furthermore, a biochemical approach confirmed that BisA can repair protein-bound MetO residues. Hence, we propose that BisA plays a role as a periplasmic methionine sulfoxide reductase. This is the first report of a Mo/W-bisPGD-enzyme supporting both N- or S-oxide respiration and protein-bound MetO repair in a pathogen.

Formate production is dispensable for Haemophilus ducreyi virulence in human volunteers.

Haemophilus ducreyi is a causative agent of cutaneous ulcers in children who live in the tropics and of the genital ulcer disease chancroid in sexually active persons. In the anaerobic environment of abscesses and ulcers, anaerobic respiration and mixed acid fermentation (MAF) can be used to provide cellular energy. In Escherichia coli, MAF produces formate, acetate, lactate, succinate, and ethanol; however, MAF has not been studied in H. ducreyi. In human challenge experiments with H. ducreyi 35000HP, transcripts of the formate transporter FocA and pyruvate formate lyase (PflB) were upregulated in pustules compared to the inocula. We made single and double mutants of focA and pflB in 35000HP. Growth of 35000HPΔfocA was similar to 35000HP, but 35000HPΔpflB and 35000HPΔfocA-pflB had growth defects during both aerobic and anaerobic growth. Mutants lacking pflB did not secrete formate into the media. However, formate was secreted into the media by 35000HPΔfocA, indicating that H. ducreyi has alternative formate transporters. The pH of the media during anaerobic growth decreased for 35000HP and 35000HPΔfocA, but not for 35000HPΔpflB or 35000HPΔfocA-pflB, indicating that pflB is the main contributor to media acidification during anaerobic growth. We tested whether formate production and transport were required for virulence in seven human volunteers in a mutant versus parent trial between 35000HPΔfocA-pflB and 35000HP. The pustule formation rate was similar for 35000HP (42.9%)- and 35000HPΔfocA-pflB (62%)-inoculated sites. Although formate production occurs during in vitro growth and focA-pflB transcripts are upregulated during human infection, focA and pflB are not required for virulence in humans.

Rates of iron(III) reduction coupled to elemental sulfur or tetrathionate oxidation by acidophilic microorganisms and detection of sulfur intermediates

Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by aerobic microbial iron(II) and inorganic sulfur/compound oxidation. Dissimilatory iron(III) reduction coupled to sulfur/compound oxidation (DIRSO) by acidophilic microorganisms has been described for anaerobic cultures, but iron reduction was observed under aerobic conditions as well. Aim of this study was to explore reaction rates and mechanisms of this process. Cell-specific iron(III) reduction rates for different Acidithiobacillus (At.) strains during batch culture growth or stationary phase with iron(III) (∼40 mM) as electron acceptor and elemental sulfur or tetrathionate as electron donor (1% or 5 mM, respectively) were determined. The rates were highest under anaerobic conditions for the At. ferrooxidans type strain with 6.8 × 106 and 1.1 × 107 reduced iron(III) ions per second per cell for growth on elemental sulfur and tetrathionate, respectively. The iron(III) reduction rates were somehow lower for the anaerobically sulfur grown archaeon Ferroplasma acidiphilum, and lowest for the sulfur grown At. caldus type strain under aerobic conditions (1.7 × 106 and 7.3 × 104 reduced iron(III) ions per second per cell, respectively). The rates for five strains of At. thiooxidans (aerobe) were in between those for At. ferrooxidans (anaerobe) and At. caldus (aerobe). There was no pronounced pH dependence of iron(III) reduction rates in the range of pH 1.0–1.9 for the type strains of all species but rates increased with increasing pH for four other At. thiooxidans strains. Thiosulfate as sulfur intermediate was found for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III) but not during anaerobic growths on elemental sulfur and iron(III), and a small concentration was measured during aerobic growths on tetrathionate without iron(III). For the At. thiooxidans type strain thiosulfate was found with tetrathionate grown cells under aerobic conditions in presence and absence of iron(III), but not with sulfur grown cells. Evidence for hydrogen sulfide production at low pH was found for the At. ferrooxidans as well as the At. thiooxidans type strains during microaerophilic growth on elemental sulfur and for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III). The occurrence of sulfur compound intermediates supports the hypothesis that chemical reduction of iron(III) ions takes place by sulfur compounds released by the microbial cells.

The evolution of anaerobic growth in Saccharomycotina yeasts.

Humans rely on the ability of budding yeasts to grow without oxygen in industrial scale fermentations that produce beverages, foods, and biofuels. Oxygen is deeply woven into the energy metabolism and biosynthetic capabilities of budding yeasts. While diverse ecological habitats may provide wide varieties of different carbon and nitrogen sources for yeasts to utilize, there is no direct substitute for molecular oxygen, only a range of availability. Understanding how a small subset of budding yeasts evolved the ability to grow without oxygen could expand the set of useful species in industrial scale fermentations as well as provide insight into the cryptic field of yeast ecology. However, we still do not yet appreciate the full breadth of species that can growth without oxygen, what genes underlie this adaptation, and how these genes have evolved.

The influence of the coronavirus disease transmitted during pregnancy on the course of gestation and changes in the main biotopes of a woman’s organism

The article presents literature data on the peculiarities of the pregnancy course and changes in the main biotopes in women who suffered from COVID-19 in different periods of gestation. Certain regularities regarding the association of perinatal complications with the severity of the disease, the presence of somatic and gynecological pathology in these pregnant women, in particular, obesity and chronic inflammatory diseases of the genital organs, were observed.According to research conducted on the basis of the department of pathology of pregnancy and childbirth of the State Institution «Institute of Pediatrics, Obstetrics and Gynecology named after academician O. M. Lukyanova of the National Academy of Sciences of Ukraine», the risk group of a severe course of the coronavirus disease includes all the same factors as for any other diseases, not related to pregnancy: age over 35 years; the presence of concomitant pathology (diabetes, obesity, hypertension), work, lifestyle or housing conditions that increase the risk of infection. More frequent manifestations of obstetric pathology were found in older women and primipara women.Complicated obstetric anamnesis, namely, medical abortions and miscarriages, cervical pathology, previous inflammatory diseases, especially of the genital organs, are considered to be risk factors. The course of pregnancy and childbirth are accompanied by such complications as the threat of early miscarriage; anemia; combination of placental dysfunction, polyhydramnios and fetal distress; anomalies uterine activity, which increases the frequency of pathological childbirth in this contingent of women and requires repeated hospitalization during pregnancy.A review of scientific publications in recent years demonstrates the significant impact of COVID-19 on the composition of biotopes of the human organism. There are convincing data on the close relationship between the infection of the mucous membranes of the upper respiratory tract and the infection of the lungs with the SARS-CoV-2 virus. Lung hypoxia, typical for this infection, causes the growth of anaerobes and facultative anaerobes, which are part of the mentioned microbiomes during a person’s life. A significant number of observations have found the correlation of changes in the microbiocenosis of the respiratory tract and intestines in patients with SARS-CoV-2 and convalescents. At the same time, there is also a disorder in the vaginal microbiocenosis after the coronavirus disease, especially during pregnancy. A conclusion was made regarding the correlation between the severity of COVID-19 course and the number of lactobacilli in the vaginal biotope: the more severe course, the worse of the microflora composition. The gestation period is more often complicated by the threat of early pregnancy loss, placental dysfunction, polyhydramnios, fetal distress, and the threat of premature birth in those women who suffered a coronavirus infection in the I trimester. A large rate of polyhydramnios in most cases indicates the risk of intrauterine infection, so such women should be carefully monitored both for the impact of COVID-19 and for the activation of latent infections in the background of reduced immunity and, first of all, violations of the vaginal biotope. At the same time, a high frequency of obesity was found among these women, which worsens the course of infectious processes and the condition of the main biotopes.Therefore, for this contingent of women, the issue of timely detection and correction of violations of the genital tract microbiocenosis as a prevention of perinatal and obstetric complications becomes relevant. In order to avoid the negative impact of changes in the vaginal microbiocenosis on the condition of a woman and her child in the future, modern universal and safe preparations during pregnancy and lactation should be used for local treatment and strengthening of regenerative processes, which do not contain an antibacterial component, do not cause antibiotic resistance and are effective, available and convenient to use. The clinical experience of recent years allows to recommend for wide use in obstetrics and gynecology the complex safe and effective local preparations, which include chlorhexidine, chlorophyllipt and preparations with hyaluronic acid and plant extracts.

Carbon nanotubes modified reticulated vitreous carbon materials enhancing extracellular electron transfer of Shewanella loihica PV-4

Increasing current output of bioelectrochemical devices is crucial for their real-world application. Electrodes modified with conductive nanoparticles increase the contact area between anodic microorganisms and solid electron acceptors, thus resulting in higher cells concentration and current output. Electron transfer mechanisms in Shewanella loihica PV-4 viable biofilms formed at carbon nanotubes (CNTs)-coated RVC electrode is investigated in potentiostat-controlled electrochemical cells set at oxidative potentials. Chronoamperometry showed a stable biofilm growth with final current output above 150 µA·cm−2 within two weeks, which was 3 times higher than unmodified RVC systems. The current output showed biphasic growth, which could be attributed to outer layer and inner layer biofilm growth, respectively, where aerobic and anaerobic growth occurred, respectively. Cyclic voltammetry and differential pulse voltammetry analysis indicated a contribution from both direct electron transfer (DET) and mediated electron transfer (MET) mechanisms. In the early stage, DET was dominant and contributed to biofilm formation. In the late stage, the contribution from MET to the overall extracellular electron transfer (EET) eventually became dominant. The mediators could be confined into the biofilm matrix and produce continuous current output. Scanning electron microscopy (SEM) showed that the bacteria distributed uniformly on the electrode surface, which enhanced the EET rate. The high surface of the RVC-CNTs electrode was accessible to biofilms in short-term batch experiments, and RVC-CNTs could be a potential anodic material for bioelectrochemical devices.

PKA regulatory subunit Bcy1 couples growth, lipid metabolism, and fermentation during anaerobic xylose growth in Saccharomyces cerevisiae.

Organisms have evolved elaborate physiological pathways that regulate growth, proliferation, metabolism, and stress response. These pathways must be properly coordinated to elicit the appropriate response to an ever-changing environment. While individual pathways have been well studied in a variety of model systems, there remains much to uncover about how pathways are integrated to produce systemic changes in a cell, especially in dynamic conditions. We previously showed that deletion of Protein Kinase A (PKA) regulatory subunit BCY1 can decouple growth and metabolism in Saccharomyces cerevisiae engineered for anaerobic xylose fermentation, allowing for robust fermentation in the absence of division. This provides an opportunity to understand how PKA signaling normally coordinates these processes. Here, we integrated transcriptomic, lipidomic, and phospho-proteomic responses upon a glucose to xylose shift across a series of strains with different genetic mutations promoting either coupled or decoupled xylose-dependent growth and metabolism. Together, results suggested that defects in lipid homeostasis limit growth in the bcy1Δ strain despite robust metabolism. To further understand this mechanism, we performed adaptive laboratory evolutions to re-evolve coupled growth and metabolism in the bcy1Δ parental strain. The evolved strain harbored mutations in PKA subunit TPK1 and lipid regulator OPI1, among other genes, and evolved changes in lipid profiles and gene expression. Deletion of the evolved opi1 gene partially reverted the strain's phenotype to the bcy1Δ parent, with reduced growth and robust xylose fermentation. We suggest several models for how cells coordinate growth, metabolism, and other responses in budding yeast and how restructuring these processes enables anaerobic xylose utilization.

Decolonizing drug-resistant E. coli with phage and probiotics: breaking the frequency-dependent dominance of residents.

Widespread antibiotic resistance in commensal bacteria creates a persistent challenge for human health. Resident drug-resistant microbes can prevent clinical interventions, colonize wounds post-surgery, pass resistance traits to pathogens or move to more harmful niches following routine interventions such as catheterization. Accelerating the removal of resistant bacteria or actively decolonizing particular lineages from hosts could therefore have a number of long-term benefits. However, removing resident bacteria via competition with probiotics, for example, poses a number of ecological challenges. Resident microbes are likely to have physiological and numerical advantages and competition based on bacteriocins or other secreted antagonists is expected to give advantages to the dominant partner, via positive frequency dependence. Since a narrow range of Escherichia coli genotypes (primarily those belonging to the clonal group ST131) cause a significant proportion of multidrug-resistant infections, this group presents a promising target for decolonization with bacteriophage, as narrow-host-range viral predation could lead to selective removal of particular genotypes. In this study we tested how a combination of an ST131-specific phage and competition from the well-known probiotic E. coli Nissle strain could displace E. coli ST131 under aerobic and anaerobic growth conditions in vitro. We showed that the addition of phage was able to break the frequency-dependent advantage of a numerically dominant ST131 isolate. Moreover, the addition of competing E. coli Nissle could improve the ability of phage to suppress ST131 by two orders of magnitude. Low-cost phage resistance evolved readily in these experiments and was not inhibited by the presence of a probiotic competitor. Nevertheless, combinations of phage and probiotic produced stable long-term suppression of ST131 over multiple transfers and under both aerobic and anaerobic growth conditions. Combinations of phage and probiotic therefore have real potential for accelerating the removal of drug-resistant commensal targets.

Microbial Profiling of Amniotic Fluid, Umbilical Blood and Placenta of the Foaling Mare.

The presence of a microbiome/microbiota in the placenta is hotly debated. In previous studies, the presence of bacteria in equine amniotic fluid and umbilical blood was independent of foal health. The objective of the present study was to determine if the same bacteria are present in the equine placenta as in amniotic fluid and umbilical blood. Samples were obtained from 24 parturient mares and foals. Placental bacterial DNA was extracted, and the microbiome was identified using 16S rRNA sequencing. All amniotic fluid samples contained some polymorphonucleocytes; bacteria were isolated from four samples. Aerobic or anaerobic growth was found in 18 and 3 umbilical blood samples, respectively. Serum amyloid A was <5 mg/L in all 24 samples, total WBC varied between 2900 and 10,700/µL, and fibrinogen varied between 0 and 5.16 g/L. In jugular blood, serum amyloid A was <5 mg/L in all 24 foals, total white blood count was 3200 to 8100/µL, and fibrinogen was 0.44 to 4.42 g/L. The diversity of bacterial microbiota was similar in all placental regions at the phylum level but differed at the genus level; the most abundant phyla were Proteobacteria (42-46.26%) and Actinobacteria (26.91-29.96%). In conclusion, bacteria were found in the fetal compartments and placenta of healthy equine pregnancies; however, we can neither prove nor disprove the hypothesis that the placenta has its own microbiome.

Surgical Marking Pen Contamination: Writing a Postoperative Infection Into Your Preoperative Plan.

Introduction Preoperative marking is an essential safety practice to prevent "never" events, including wrong site surgery. Moreover, the Joint Commission regulations of the Universal Protocol require that patients be marked to indicate the operative site. Marking typically occurs with a pen or marker, which may be disposable or reusable. Previous studies have demonstrated that methicillin-resistant Staphylococcus aureus (MRSA) can survive in the dark, moist, capped environment of the marking pen and thus could plausibly be a nidus for transmission from patient to patient. The Joint Commission has established no increased risk of postoperative infection with these markings. With this study, we aimed to determine the colonization of surgical marking pens in the plastic surgery population. Methods Two marking pens from five different attending plastic surgeons at a single institution were cultured in standard fashion for aerobic and anaerobic growth. All pens were used repeatedly in office settings for performing patient markings. Those same ten marking pens were then used to mark incision sites on mock patients. Standard povidone-iodine prepping was then performed in a paint-only fashion over the skin markings, and cultures were again taken. A control group consisted of cultures from five sterile pens from the operating room. Each sterile pen was opened, uncapped, and then swabbed. All twenty-five cultures were analyzed in the hospital laboratory in a blinded fashion. Results The five control pens revealed no bacterial growth. Of the 10 direct pen cultures, two samples grew coagulase-negative staphylococci and one culture contained Pseudomonas aeruginosa. The 10-patient marked and prepped specimens showed eight negative cultures and two with coagulase-negative staphylococci. Although Pseudomonas was detected on standard pen culture, no pseudomonal growth was present in any of the samples after patient marking and prepping with povidone-iodine. Conclusions Our findings reaffirm that marking pens may be vehicles for bacterial transmission and expand upon previous studies by describing the presence of bacterial colonization on marking pens even after surgical site preparation with povidone-iodine.

ВЛИЯНИЕ МЕРОПЕНЕМА И ИМИЦЕНЕМА НА МИКРОБИОЦЕНОЗ И МОРФОЛОГИЮ ТОНКОГО КИШЕЧНИКА КРЫС

Background. Gut microbiota plays an important role in the human body, antimicrobial drugs intake being one of the main factors affecting microbiota composition. Antibiotics suppress normal intestinal microflora allowing for the growth and development of pathogenic flora. Objective. To study the effect of meropenem and imicenem on the microbiocenosis and morphology of the small intestine in rats. Material and methods. In an experiment on rats, we analysed the microbiocenosis of the large intestine after intraperitoneal administration of meropenem, imicinem and 0.9% NaCl, as well as examined samples of the small intestine. Results. In a comparative analysis of the control group with the meropenem and imicinem groups, there has been noted a decrease in the number of anaerobes in the meropenem group (8.6±0.14, p&lt;0.05) as compared with the control group (9.4±0.22, p&lt;0 .05) and the imicinem group (9.4±0.40, p&lt;0.05); the number of bifidobacteria decreased in the meropenem group (8.1±0.16, p&lt;0.05) in contrast to the control group (9.2±0.25, p&lt;0.05) and the imicinem group (9.2±0.41, p&lt;0.05). When compared with meropenem (3.8±0.44, p&lt;0.05), imicinem (4.9±0.20, p&lt;0.05) led to a greater growth of spore-forming anaerobes. In animals of the imicinem group, the histostructure of the jejunal mucosa was similar to the control group, while in the meropenem group, inflammatory changes in the stroma of the villi of the jejunal mucosa were observed. Conclusions. In a comparative analysis of carbapenem activity, it has been determined that these antibiotics both have a significant effect on the microbiocenosis of the large intestine and affect the mucous wall of the small intestine. These should be taken into account by clinicians in order to improve the effectiveness and safety of antibiotic therapy.