Microbiome Analysis Revealed Acholeplasma as a Possible Factor Influencing the Susceptibility to Bacterial Leaf Blight Disease of Two Domestic Rice Cultivars in Vietnam.

The microbiomes of two important rice cultivars in Vietnam which differ by their susceptibility to the bacterial leaf blight (BLB) disease were analyzed through 16S rRNA amplicon technology. A higher number of operational taxonomic units and alpha-diversity indices were shown in the BLB-resistant LA cultivar than in the BLB-susceptible TB cultivar. The BLB pathogen Xanthomonas was scantly found (0.003%) in the LA cultivar, whereas was in a significantly higher ratio in the TB cultivar (1.82%), reflecting the susceptibility to BLB of these cultivars. Of special interest was the genus Acholeplasma presented in the BLB-resistant LA cultivar at a high relative abundance (22.32%), however, was minor in the BLB-sensitive TB cultivar (0.09%), raising a question about its roles in controlling the Xanthomonas low in the LA cultivar. It is proposed that Acholeplasma once entered the host plant would hamper other phytopathogens, i.e. Xanthomonas, by yet unknown mechanisms, of which the triggering of the host plants to produce secondary metabolites against pathogens could be a testable hypothesis.

Whole-genome sequencing of antimicrobial-resistant Salmonella enterica isolates from a Cairina moschata carcass.

Salmonella enterica is one of the most common agents of foodborne bacterial illness with poultry being an important reservoir. The indiscriminate use of antimicrobial compounds in poultry farming increasingly leads to antimicrobial-resistant (AMR) which threatens the health of both animals and humans. Antimicrobial-resistant Salmonella enterica from the poultry can spread to human through the direct contact with infected poultry or fecal contaminated environments. Antimicrobial-resistant S. enterica, especially fluoroquinolone-resistant nontyphoidal Salmonella is in the list of global health concern stated by the World Health Organization (WHO). Here we report the whole-genome sequencing data and de novo genome assemble of antimicrobial-resistant S. enterica strains S8 and S9 from the C. moschata carcass collected in Vietnam. Genomic DNA of S. enterica were extracted and subjected to whole-genome sequencing using Illumina MiSeq platform. The genome size of antimicrobial-resistant S. enterica strain S8 is 4,707,459 bp with a GC-content of 52.38%, containing 10 antimicrobial resistant genes. The genome size of antimicrobial-resistant Samonella enterica strain S9 is 4,923,944 bp with a GC-content of 52,39%, containing 10 antimicrobial resistance genes. Our data provided the insights on antimicrobial resistant genes of S. enterica isolates from the C. moschata carcass, which help to understand the infection mechanism of antimicrobial-resistant S. enterica in human.

Management of Highly Resistant Gram-Negative Infections in the Intensive Care Unit in the Era of Novel Antibiotics.

Antimicrobial-resistant bacterial infections, particularly those caused by Gram-negative bacteria, are major public health threats globally. Since 2015, several antibiotics with activity against highly antimicrobial-resistant Gram-negative bacteria have been approved, which offer alternatives emerging to previous frontline agents such as polymyxins and aminoglycosides. Despite data that new drugs are more effective and better tolerated than older agents against at least some highly antimicrobial-resistant Gram-negative bacterial infections, clinicians remain uncertain about how best to incorporate them into clinical practice. In this article, we discuss the management of highly resistant Gram-negative bacterial infections in the era of new antibiotics, with particular attention to those caused by AmpC- and extended-spectrum ß-lactamase-producing Enterobacterales (which manifest phenotypically as 3rd generation cephalosporin resistance), carbapenem-resistant Enterobacterales, multidrug-resistant Pseudomonas aeruginosa, carbapenem-resistant acinetobacter baumannii, and Stenotrophomonas maltophilia.

Paenibacillus vietnamensis sp. nov., isolated from the rhizosphere soil of Arachis hypogaea.

A novel bacterial strain, N4T, was isolated from the soil of a groundnut Arachis hypogaea field in Nghean province, Vietnam. The phylogenetic, chemotaxonomic and phenotypic characteristics of this strain were determined. Cells of strain N4T were Gram-negative, aerobic, endospore-forming and rod-shaped. Strain N4T grew at 20-37 °C (optimum, 30 °C), pH 6-10 (optimum, pH 7) and 0-5 % NaCl (optimum, 0 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain N4T belonged to the genus Paenibacillus and was closely related to Paenibacillus harenae B519T (=KCTC 3951T) and Paenibacillus alkaliterrae KSL-134T (=KCTC 3956T) with 96.3 and 96.5% gene sequence similarity, respectively. It contained meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 52.9 mol%. The major isoprenoid quinone was MK-7. Anteiso-C15 : 0 and iso-C16 : 0 were the dominant cellular fatty acids. Based on phylogenetic, physiological and biochemical characteristics, strain N4T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus vietnamensis sp. nov. is proposed. The type strain is N4T (=KCTC 33932T= VTCC 12236T).

In vitro antiviral activities of ethanol and aqueous extracts of Vietnamese traditional medicinal plants against Porcine Epidemic Diarrhea virus: a coronavirus family member.

Porcine epidemic diarrhea virus (PEDV) causes diarrhea in pigs leading to severe illnesses and high mortality rates. The development of medicinal agents to treat PEDV infection is therefore crucial. In this study, antiviral activities against PEDV of ethanol and aqueous extracts of 17 Vietnamese traditional medicinal plants were evaluated using the cytopathic effect-based assay. The results showed that 14 out of 17 medicinal plants could inhibit the cytopathic effect of PEDV. The ethanol extract of Stixis scandens was identified as the most active extract with its MIC (minimum inhibitory concentration) being 0.15 µg/mL. Other plant extracts also displayed strong antiviral activity against PEDV, including Anisomeles indica, Pericampylus glaucus and Croton kongensis. The results demonstrate that certain medicinal plants have a high antiviral potential and may serve as a lead to develop novel pharmaceutical agents to cure PED as well as the diseases caused by other coronaviruses.

Biomedical Applications of Bacterial Exopolysaccharides: A Review.

Bacterial exopolysaccharides (EPSs) are an essential group of compounds secreted by bacteria. These versatile EPSs are utilized individually or in combination with different materials for a broad range of biomedical field functions. The various applications can be explained by the vast number of derivatives with useful properties that can be controlled. This review offers insight on the current research trend of nine commonly used EPSs, their biosynthesis pathways, their characteristics, and the biomedical applications of these relevant bioproducts.

Dataset on the effects of spacing and fruit truss limitation on the growth, yield and quality of open-field tomato plants.

This article presents data on the effects of spacing and fruit truss limitation on tomato plant growth, yield and fruit quality. Plants with two, three, and four fruit trusses (T1-T3) were grown in four different spaces (S1-S4) to create 12 treatments. The experiment was conducted on an open field with a randomized complete block design and three replications. Data on fruit quantity, weight, and yield were collected to assess the effects of plant density and fruit truss limitation on tomato fruit produced and marketable fruit produced. This data could help develop a strategy for breeding new tomato cultivars for high density planting on the rice-based rotational crop systems in the Red River Delta of Vietnam and other similar sub-tropical regions.

Sulfate Reduction for Bioremediation of AMD Facilitated by an Indigenous Acidand Metal-Tolerant Sulfate-Reducer.

Acid mine drainage (AMD) has been a serious environmental issue that threatens soil and aquatic ecosystems. In this study, an acid-tolerant sulfate-reducing bacterium, strain S4, was isolated from the mud of an AMD storage pond in Vietnam via enrichment in anoxic mineral medium at pH 5. Comparative analyses of sequences of the 16S rRNA gene and dsrB gene involved in sulfate reduction revealed that the isolate belonged to the genus Desulfovibrio, and is most closely related to Desulfovibrio oxamicus (with 99% homology in 16S rDNA sequence and 98% homology in dsrB gene sequence). Denaturing gradient gel electrophoresis (DGGE) analyses of dsrB gene showed that strain S4 represented one of the two most abundant groups developed in the enrichment culture. Notably, strain S4 was capable of reducing sulfate in low pH environments (from 2 and above), and resistance to extremely high concentration of heavy metals (Fe 3,000 mg/l, Zn 100 mg/l, Cu 100 mg/ l). In a batch incubation experiment in synthetic AMD with pH 3.5, strain S4 showed strong effects in facilitating growth of a neutrophilic, metal sensitive Desulfovibrio sp. strain SR4H, which was not capable of growing alone in such an environment. Thus, it is postulated that under extreme conditions such as an AMD environment, acid- and metal-tolerant sulfate-reducing bacteria (SRB)- like strain S4 would facilitate the growth of other widely distributed SRB by starting to reduce sulfate at low pH, thus increasing pH and lowering the metal concentration in the environment. Owing to such unique physiological characteristics, strain S4 shows great potential for application in sustainable remediation of AMD.

Rapid diagnosis of invasive candidiasis: ready for prime-time?

PURPOSE OF REVIEW: We review the performance of culture-independent diagnostic tests (CIDTs), including ß-D-glucan (BDG), polymerase chain reaction (PCR) and T2Candida, in diagnosing invasive candidiasis, their potential roles in patient management, and unintended consequences of testing. RECENT FINDINGS: In a recent multicenter trial, T2Candida was 90% sensitive and 98% specific for diagnosing candidemia. A new study provided the first data for T2Candida in diagnosing deep-seated candidiasis, demonstrating sensitivity/specificity of 45%/96%. Two studies showed that ongoing T2Candida-positivity is associated with poor prognosis. In several studies, serum BDG and T2Candida, targeted to patients at-risk for invasive candidiasis, were useful in guiding treatment decisions and antifungal stewardship. A randomized, multicenter trial of BDG-guided empiric antifungal treatment is underway among critically ill patients. PCR performance was highly variable for candidemia and deep-seated candidiasis in recent studies. CIDT results may overstate bloodstream infections, according to current National Healthcare Safety Network (NHSN) definitions. SUMMARY: BDG and T2Candida are nearing prime-time status in the clinic. To be useful, testing must be directed to carefully chosen patients and specific clinical questions. Candida PCR is limited by a need for standardized methodologies and commercial assays. NHSN definitions of bloodstream infections must be revised in the era of CIDTs.

Combating resistance while maintaining innovation: the future of antimicrobial stewardship.

Antimicrobial resistance represents a significant global health threat. However, a commercial model that does not offer a return on investment resulting in a lack of investment in antibiotic R&D, means that the current pipeline of antibiotics lacks sufficient innovation to meet this challenge. Those responsible for defining, promoting and monitoring the rationale use of antibiotics (the antimicrobial stewardship programme) are key to addressing current shortcomings. In this personal perspective, we discuss the future role stewardship can play in stimulating innovation, a need to move away from a pharmacy budget dominated view of antibiotic use, and the impact of the ever-increasing sophistication and interdisciplinary nature of antimicrobial control programs. Changes are needed to optimize clinical outcomes for patients.

Klebsiella pneumoniae Carbapenemase-2 (KPC-2), Substitutions at Ambler Position Asp179, and Resistance to Ceftazidime-Avibactam: Unique Antibiotic-Resistant Phenotypes Emerge from ß-Lactamase Protein Engineering.

The emergence of Klebsiella pneumoniae carbapenemases (KPCs), ß-lactamases that inactivate "last-line" antibiotics such as imipenem, represents a major challenge to contemporary antibiotic therapies. The combination of ceftazidime (CAZ) and avibactam (AVI), a potent ß-lactamase inhibitor, represents an attempt to overcome this formidable threat and to restore the efficacy of the antibiotic against Gram-negative bacteria bearing KPCs. CAZ-AVI-resistant clinical strains expressing KPC variants with substitutions in the Ω-loop are emerging. We engineered 19 KPC-2 variants bearing targeted mutations at amino acid residue Ambler position 179 in Escherichia coli and identified a unique antibiotic resistance phenotype. We focus particularly on the CAZ-AVI resistance of the clinically relevant Asp179Asn variant. Although this variant demonstrated less hydrolytic activity, we demonstrated that there was a prolonged period during which an acyl-enzyme intermediate was present. Using mass spectrometry and transient kinetic analysis, we demonstrated that Asp179Asn "traps" ß-lactams, preferentially binding ß-lactams longer than AVI owing to a decreased rate of deacylation. Molecular dynamics simulations predict that (i) the Asp179Asn variant confers more flexibility to the Ω-loop and expands the active site significantly; (ii) the catalytic nucleophile, S70, is shifted more than 1.5 Å and rotated more than 90°, altering the hydrogen bond networks; and (iii) E166 is displaced by 2 Å when complexed with ceftazidime. These analyses explain the increased hydrolytic profile of KPC-2 and suggest that the Asp179Asn substitution results in an alternative complex mechanism leading to CAZ-AVI resistance. The future design of novel ß-lactams and ß-lactamase inhibitors must consider the mechanistic basis of resistance of this and other threatening carbapenemases.IMPORTANCE Antibiotic resistance is emerging at unprecedented rates and threatens to reach crisis levels. One key mechanism of resistance is the breakdown of ß-lactam antibiotics by ß-lactamase enzymes. KPC-2 is a ß-lactamase that inactivates carbapenems and ß-lactamase inhibitors (e.g., clavulanate) and is prevalent around the world, including in the United States. Resistance to the new antibiotic ceftazidime-avibactam, which was designed to overcome KPC resistance, had already emerged within a year. Using protein engineering, we uncovered a mechanism by which resistance to this new drug emerges, which could arm scientists with the ability to forestall such resistance to future drugs.

Unraveling Drug Penetration of Echinocandin Antifungals at the Site of Infection in an Intra-abdominal Abscess Model.

Intra-abdominal candidiasis (IAC) is a prominent invasive fungal infection associated with high mortality. Prompt antifungal therapy and source control are crucial for successful treatment. Echinocandin antifungal drugs are first-line agents; however, their clinical effectiveness is highly variable, with known potential for breakthrough resistance, and little is known about drug exposure at the site of infection. Using matrix-assisted desorption ionization mass spectrometry imaging technology, we investigated the spatial and quantitative distribution in tissue lesions for two echinocandin drugs, micafungin and CD101, in a clinically relevant IAC mouse model. Drug accumulation within lesions was observed with both drugs at their humanized therapeutic doses. CD101, but not micafungin, accumulated in lesions at levels above the mutant prevention concentration of the infecting strain. These findings indicate that current echinocandin drugs are limited by penetration at the site of infection and have implications for clinical outcomes and emergence of resistance in patients with IAC.

CD36 Provides Host Protection Against Klebsiella pneumoniae Intrapulmonary Infection by Enhancing Lipopolysaccharide Responsiveness and Macrophage Phagocytosis.

Klebsiella pneumoniae remains an important cause of intrapulmonary infection and invasive disease worldwide. K. pneumoniae can evade serum killing and phagocytosis primarily through the expression of a polysaccharide capsule, but its pathogenicity is also influenced by host factors. We examined whether CD36, a scavenger receptor that recognizes pathogen and modified self ligands, is a host determinant of K. pneumoniae pathogenicity. Despite differences in serum sensitivity and virulence of 3 distinct K. pneumoniae (hypermucoviscous K1, research K2, and carbapenemase-producing ST258) strains, the absence of CD36 significantly increased host susceptibility to acute intrapulmonary infection by K. pneumoniae, regardless of strain. We demonstrate that CD36 enhances LPS responsiveness to K. pneumoniae to increase downstream cytokine production and macrophage phagocytosis that is independent of polysaccharide capsular antigen. Our study provides new insights into host determinants of K. pneumoniae pathogenicity and raises the possibility that functional mutations in CD36 may predispose individuals to K. pneumoniae syndromes.

Is Fluconazole or an Echinocandin the Agent of Choice for Candidemia.

OBJECTIVE: Candidemia is among the most common nosocomial bloodstream infections and is associated with high mortality, increased length of hospital stay, and significant economic burden. The introduction of the echinocandins in the 2000s has expanded the armamentarium against Candida spp and provides therapeutic options that are effective, safe, and tolerable. Although the Infectious Diseases Society of America favors echinocandins as treatment for candidemia in selected settings (at least as initial therapy), there remain divergent opinions about whether an echinocandin or fluconazole is the preferred agent for candidemia, and clinical practice guidelines are in flux. In this review, the currently available laboratory and clinical data are summarized and critically evaluated. DATA SOURCES: A MEDLINE search of the English language literature was performed using the search terms echinocandin, fluconazole, and candidemia. References of review articles and guidelines were also screened for inclusion. STUDY SELECTION AND DATA EXTRACTION: Studies whose primary goal was to compare echinocandins with fluconazole were evaluated as well as studies that differentiated pharmacological and pharmacokinetic properties between agents. DATA SYNTHESIS: It is clear that echinocandins and fluconazole each have roles in the management of candidemia. Specific recommendations are provided that will hopefully optimize outcomes in candidemia while incorporating stewardship concepts of cost-effectiveness and limiting the emergence of resistance. CONCLUSIONS: Despite the advantages brought by the echinocandins and fluconazole, outcomes among patients with candidemia remain suboptimal. Improved treatment of candidemia may ultimately be achieved by optimizing the use of antifungal agents rather than the development of new drugs.

Flocculation of Escherichia coli Cells in Association with Enhanced Production of Outer Membrane Vesicles.

Microbial flocculation is a phenomenon of aggregation of dispersed bacterial cells in the form of flocs or flakes. In this study, the mechanism of spontaneous flocculation of Escherichia coli cells by overexpression of the bcsB gene was investigated. The flocculation induced by overexpression of bcsB was consistent among the various E. coli strains examined, including the K-12, B, and O strains, with flocs that resembled paper scraps in structure being about 1 to 2 mm. The distribution of green fluorescent protein-labeled E. coli cells within the floc structure was investigated by three-dimensional confocal laser scanning microscopy. Flocs were sensitive to proteinase K, indicating that the main component of the flocs was proteinous. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and nano-liquid chromatography tandem mass spectrometry analyses of the flocs strongly suggested the involvement of outer membrane vesicles (OMVs) in E. coli flocculation. The involvement of OMVs in flocculation was supported by transmission electron microscopy observation of flocs. Furthermore, bcsB-induced E. coli flocculation was greatly suppressed in strains with hypovesiculation phenotypes (ΔdsbA and ΔdsbB strains). Thus, our results demonstrate the strong correlation between spontaneous flocculation and enhanced OMV production of E. coli cells.

Exopolysaccharide assay in Escherichia coli microcolonies using a cleavable fusion protein of GFP-labeled carbohydrate-binding module.

A fused protein composed of a carbohydrate-binding module and green fluorescence protein (GFP) was developed to measure the exopolysaccharides (EPShs) present in Escherichia coli microcolonies. The cleavage of the GFP part of this protein using a site-specific protease allowed for the non-invasive and quantitative evaluation of the EPShs.

Enhanced colonization of rpoS-deficient Escherichia coli cells on solid surfaces by reinforced csgA gene expression.

Scanning electron microscopy revealed that the rpoS-deficient cells of E. coli K-12 BW25113 (ΔrpoS) increased the number of flagella on the cell surfaces. However, the quantitative analysis of cell colonization showed that the increased number of flagella on ΔrpoS cell surfaces did not cause the enhancement of cell colonization on the surfaces of polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS) after 24 h of incubation at 37℃. To facilitate the enhanced expression of curli, the csgA gene was introduced into the ΔrpoS cells. The transformed cells rich in flagella and curli on the cell surfaces were found to make colonies 2-3 times larger than both the wild type and ΔrpoS cells on the PVC, PP and PS surfaces at 37℃. It was thus verified that the reinforcement of csgA gene in the ΔrpoS cells induced the enhanced colonization on the solid surfaces with the increased flagellum and curli expressions.

Undiagnosed invasive candidiasis: incorporating non-culture diagnostics into rational prophylactic and preemptive antifungal strategies.

The insensitivity of blood cultures for diagnosing invasive candidiasis fuels prophylactic and preemptive antifungal treatment. Assays like serum ß-D-glucan or mannan/anti-mannan detection can identify blood culture-negative invasive candidiasis, but their roles in guiding antifungal therapy are undefined. We propose that non-culture tests can be incorporated into rational management strategies, based on clinical setting. As an example, ß-D-glucan sensitivity/specificity for blood culture-negative, deep-seated candidiasis is approximately 60/75%. In intensive care units with <1 or 3% invasive candidiasis rates, positive/negative predictive values are <2/>99% and 6/98%, respectively. With pre-test likelihoods of 10 and 33%, positive/negative predictive values are 20/94% and 54/79%, respectively. Based on these data, negative and positive ß-D-glucan results likely will be most useful for discontinuing prophylaxis among low-risk to moderate-risk patients (pre-test likelihoods ∼3-10%), and triggering preemptive therapy among moderate-risk to high-risk patients (pre-test likelihoods ∼10-25%), respectively. In extremely high-risk patients, universal prophylaxis is likely to be the best strategy.