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  • Predictive Value of Blood Culture Time to Positivity
    11/16/2018
  • Microbial Life in the Wake of Hurricanes
    11/16/2018
  • Microbiology Minutes: Mega-Antibodies Treat Flu, Epidemic Calendars, and Microbiomes and Ethnicity
    11/13/2018
  • What Can We Do to Stop the Spread of Drug-Resistant Infections?
    11/12/2018
  • What Happens When Antibiotics Stop Working?
    11/12/2018
  • How Do Antibiotics in Agriculture Affect Human Clinical Infectious Diseases?
    11/12/2018
  • Multiplex Target Testing — Should We Be More Specific About Specificity?
    11/05/2018
  • From Poisoning to Pharmacy: A Tale of Two Ergots
    11/02/2018
  • Applying for Fellowships Benefits Early-Graduate Students
    11/02/2018
  • Microbiology Resource of the Month: Freshwater Vibrio cholerae Genome
    10/31/2018

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  • Monday, 19 November 2018

    Outbreaks of diseases in farmed fish remain a recurring problem despite the development of vaccines and improved hygiene standards on aquaculture farms. One commonly observed bacterial disease in tropical aquaculture of the South-East Asian region is tenacibaculosis, which is attributed to members of the Bacteroidetes genus Tenacibaculum, most notably T. maritimum. The impact of tenacibaculosis on fish microbiota remains poorly understood. In this study, we analysed the microbiota of different tissue types of commercially reared Asian seabass (Lates calcarifer) that showed symptoms of tenacibaculosis and compared the microbial communities to those of healthy and experimentally infected fish that were exposed...

  • Monday, 19 November 2018

    Aims: Bacterial genotyping on the basis of the CRISPR array has been established in Mycobacterium tuberculosis with a method called spacer oligonucleotide typing (spoligotyping). The spoligotyping method had been widely used for both detection and typing of M. tuberculosis complex bacteria. This present study aimed at determining if the CRISPR array in Salmonella spp. could be applied to establish a correlationship between serogroup and the fingerprint generated by CRISPR typing. Methodology and results: A total of 30 samples were obtained from Diagnostic Veterinary Laboratory, Kota Kinabalu, Sabah. Serogroup was determined on the basis of ELISA (enzyme-linked immunosorbent assay). Four different...

  • Monday, 19 November 2018

    Measles is a human infectious disease of global concern caused by the measles virus. In this study, we report the complete genome sequencing of one measles isolate, genotype D8, obtained in Boa Vista city, the capital of the Roraima State, Brazil, directly from the urine sample. Phylogenetics reconstruction grouped the genome described in this study with samples from Australia, Italy, United Kingdom, and the USA. To our knowledge, this is the first complete genome of a wild-type measles virus from Latin America. Therefore, the present data strengthens the current knowledge about the molecular epidemiology of measles worldwide.

  • Monday, 19 November 2018

    Sulfonamides are synthetic chemotherapeutic agents that work as competitive inhibitors of the di-hydro-pteroate synthase (DHPS) enzyme, encoded by the folP gene. Resistance to sulfonamides is widespread in the clinical setting and predominantly mediated by plasmid- and integron-borne sul1-3 genes encoding mutant DHPS enzymes that do not bind sulfonamides. In spite of their clinical importance, the genetic origin of sul1-3 genes remains unknown. Here we analyze sul genes and their genetic neighborhoods to uncover sul signature elements that enable the elucidation of their genetic origin. We identify a protein sequence Sul motif associated with sul-encoded proteins, as well as consistent association...

  • Monday, 19 November 2018

    Resistance to enfuvirtide, the only clinically approved HIV-1 entry inhibitor, has primarily been mapped to the binding site in the N-terminal heptad repeat (NHR) of the Env transmembrane domain and a limited number of allosteric sites. To better delineate the genotypic determinants of resistance, we used deep mutational scanning to quantify how all mutations to HIV-1 Env affect enfuvirtide sensitivity. We identified numerous additional resistance mutations in the NHR and other regions of Env, including the co-receptor binding site. This complete map of resistance sheds light on the diverse mechanisms of enfuvirtide resistance and can inform clinical monitoring of patients.

  • Monday, 19 November 2018

    Small non-coding RNAs play a significant role in regulation of bacterial transcription and translation. Their expression in response to external factors is important for the adaptation of bacteria to changing environmental conditions. We investigated the expression of DrrS, a small noncoding RNA of Mycobacterium tuberculosis, in the mouse model in vivo, in the ex vivo model based upon infected macrophages, and in bacterial cultures, and demonstrated its significant contribution to host-pathogen interactions. Activation of the host immune system triggers NO-inducible up-regulation of DrrS in macrophage-engulfed mycobacteria. Constitutive overexpression of DrrS in cultured mycobacteria launches a broad spectrum of shifts in...

  • Monday, 19 November 2018

    Australia was officially recognised as having eliminated endemic measles circulation in 2014. Maintaining laboratory support for surveillance of vaccine-preventable diseases such as measles, is an essential component of reaching and maintaining circulation-free status. Between 2010 and 2017 over 13,700 specimens were tested in our laboratory by real-time RT-PCR (RT-rPCR). Positive extracts from travellers were sequenced as required. Sequences were uploaded to GenBank and demonstrated the wide genetic variation expected from detection of MeV among virus introductions due to global travel. We describe the laboratory workflow employed in our laboratory between 2010 and 2017 for the sensitive detection of MeV infection,...

  • Monday, 19 November 2018

    Extreme diversity of the major surface antigen and virulence determinant of the malaria parasite Plasmodium falciparum, Erythrocyte Membrane Protein-1 (PfEMP1), poses a major barrier to identifying targets of protective immunity. To overcome this problem, we developed a PfEMP1 protein microarray containing 456 DBL domains, which was used to characterize the immunome of a cohort of semi-immune children and to identify variants associated with protective immune responses. Children with high mean antibody levels to DBL group 2 had a 26-36% reduced risk of uncomplicated (clinical) malaria, however only 8 diverse DBL variants were weakly associated with protection from clinical malaria and...

  • Monday, 19 November 2018

    In the wild, the soil dwelling nematode Caenorhabditis elegans primarily feeds on microbes which are abundant in rotting vegetation. Recent published studies showthat several Gram-positive and Gram-negative bacterial populations predominantly constitutes the C. elegans gut microbiome but surprisingly lack any yeast species. Here, we show that C. elegans display low satiety on yeast diet of Cryptococcus neoformans, C. laurentii or S. cerevisiae. We found that average size of budding yeast cells is much larger than E. coli cells. Yeast cells also cause pharyngeal obstruction, diminished feeding, and lower level of neutral lipids in adult C. elegans. Using scanning electron microscopy,...

  • Sunday, 18 November 2018

    The genomes of bacteria derived from the gut microbiota are replete with pathways that mediate contact-dependent interbacterial antagonism. However, the role of direct interactions between co-resident microbes in driving microbiome composition is not well understood. Here we report the widespread occurrence of acquired interbacterial defense (AID) gene clusters in the human gut microbiome. These clusters are found on predicted mobile elements and encode arrays of immunity genes that confer protection against interbacterial toxin-mediated antagonism in vitro and in gnotobiotic mice. We find that Bacteroides ovatus strains containing AID systems that inactivate B. fragilis toxins delivered between cells by the type...

  • Sunday, 18 November 2018

    The mutualistic symbiont Vibrio fischeri builds a symbiotic biofilm during colonization of squid hosts. Regulation of the exopolysaccharide component, termed Syp, has been examined in strain ES114, where production is controlled by a phosphorelay that includes the inner membrane hybrid histidine kinase RscS. Most strains that lack RscS or encode divergent RscS proteins cannot colonize the squid host unless RscS from a squid symbiont is heterologously expressed. In this study, we examine V. fischeri isolates worldwide to understand the landscape of biofilm regulation during beneficial colonization. We provide a detailed study of three distinct evolutionary groups of V. fischeri and...

  • Sunday, 18 November 2018

    Biflagellate zoospores of some phytopathogenic Phytophthora species spontaneously aggregate within few minutes in suspension. Depending on species auto-aggregate formation results from bioconvection or from a sequence bioconvection-positive chemotaxis. In this study, we show that P. parasitica zoospores may form aggregates upon application of a K+ gradient in particular geometric arrangements. Based on the use of macro- and microfluidic devices, in addition to time-lapse live imaging both in the vertical and horizontal planes, we defined (i) the spatiotemporal and concentration scale evolution within the gradient in correlation with (ii) cell distribution and (iii) metrics of zoospore motion (velocity, trajectory). The results...

  • Friday, 16 November 2018

    Tsetse flies (Glossina spp.) vector pathogenic trypanosomes (Trypanosoma spp.) in sub-Saharan Africa. These parasites cause human and animal African trypanosomiases, which are debilitating diseases that inflict an enormous socio-economic burden on inhabitants of endemic regions. Current disease control strategies rely primarily on treating infected animals and reducing tsetse population densities. However, relevant programs are costly, labor intensive and difficult to sustain. As such, novel strategies aimed at reducing tsetse vector competence require development. Herein we investigated whether an Enterobacter bacterium (Esp_Z), which confers Anopheles gambiae with resistance to Plasmodium, is able to colonize tsetse and induce a trypanosome refractory phenotype...

  • Friday, 16 November 2018

    High-risk human papillomavirus (HPV) E7 proteins enable oncogenic transformation of HPV-infected cells by inactivating host cellular proteins. High-risk but not low-risk HPV E7 target PTPN14 for proteolytic degradation, suggesting that PTPN14 degradation may be related to their oncogenic activity. HPV infects human keratinocytes but the role of PTPN14 in keratinocytes and the consequences of PTPN14 degradation are unknown. Using an HPV16 E7 variant that can inactivate RB1 but cannot degrade PTPN14 we found that high-risk HPV E7-mediated PTPN14 degradation impairs keratinocyte differentiation. Deletion of PTPN14 from primary human keratinocytes decreased keratinocyte differentiation gene expression. Related to oncogenic transformation, both HPV16...

  • Friday, 16 November 2018

    Coxsackievirus typically infects humans via the gastrointestinal tract, whichhas a large number of microorganisms, collectively referred to as the microbiota. To study how the intestinal microbiota influence enteric virus infection, several groups have used an antibiotic regimen in mice to deplete bacteria.These studies have shown that bacteriapromote infection with several enteric viruses. However, very little is known about whether antibiotics influence viruses in a microbiota-independent manner. Here, we sought to determine the effects of antibiotics on coxsackievirus B3 (CVB3) using an in vitrocell culture model in the absence of bacteria. We determined that an aminoglycoside antibiotic, neomycin, enhanced plaque size...

  • Friday, 16 November 2018

    Collective behavior in spatially structured groups, or biofilms, is the norm among microbes in their natural environments. Though microbial physiology and biofilm formation have been studied for decades, tracing the mechanistic and ecological links between individual cell properties and the emergent features of cell groups is still in its infancy. Here we use single-cell resolution confocal microscopy to explore biofilm properties of the human pathogen Vibrio cholerae in conditions closely mimicking its marine habitat. We find that some - but not all - pandemic isolates produce filamentous cells than can be over 50 micrometers long. This filamentous morphotype gains a...

  • Friday, 16 November 2018

    Attachment of adenovirus (HAd) to host cell is a critical step of infection. This work reports the cryo-electron microscopy (cryo-EM) structure of a non-symmetrical complex smaller than 100kDa formed by the trimeric human adenovirus of type 3 fibre knob (HAd3K) and human desmoglein 2 (DSG2). The structure reveals a unique stoichiometry, shedding light to new adenovirus infection strategies and providing new insights for adenoviral vector development.

  • Friday, 16 November 2018

    YxaL is conserved within Bacillus subtilis species complex associated with plant and soil. The mature protein YxaL contains a repeated beta-propeller domain, but the subcellular location and function of YxaL has not been determined. The gene encoding the mature YxaL protein was PCR amplified from genomic DNA of B. velezensis strain GH1-13 and used for recombinant protein production. A rabbit polyclonal antibody against the purified YxaL was generated and used for western blotting to determine the constitutive expression and secretion of YxaL, which exhibited a half-life of 1.6 h in the culture medium of strain GH1-13. In this study, we...

  • Thursday, 15 November 2018

    The double tubular structure of the type VI secretion system (T6SS) is considered as one of the longest straight and rigid intracellular structures in bacterial cells. Contraction of the T6SS outer sheath occurs almost instantly and releases sufficient power to inject the inner needle-like Hcp tube and its associated effectors into target bacterial cells through piercing the stiff cell envelope. The molecular mechanism triggering T6SS contraction remains elusive. Here we report that the double tubular T6SS structure is strikingly flexible and elastic, forming U-, circular-, or S- shapes while maintaining functional for contraction and substrate delivery. We show that physical...

  • Thursday, 15 November 2018

    Phagosome acidification is a critical mechanism of defense in phagocytic cells, which inhibits microbes by producing a less hospitable pH that also activates microbicidal mechanisms. We analyzed the dynamic distribution of phagolysosome pH measurements after bone marrow derived macrophages had ingested live Cryptococcus neoformans or C. gattii cells, dead C. neoformans cells, or inert beads at various time intervals. Phagosomes acidified for each type of ingested particle, producing a range of pH values that approximated normal distributions, yet the degree to which they differed from normality depended on the particle type. Irrespective of the particle ingested, we noted wide variation...

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