38 results match your criteria qpx


In Vitro Activity of the Ultra-Broad-Spectrum Beta-lactamase Inhibitor QPX7728 in Combination with Multiple Beta-Lactam Antibiotics against .

Antimicrob Agents Chemother 2021 Mar 29. Epub 2021 Mar 29.

Qpex Biopharma, Inc. 6275 Nancy Ridge Drive, Suite 100, San Diego, CA 92121.

QPX7728 is an ultra-broad-spectrum beta-lactamase inhibitor with potent inhibition of key serine and metallo beta-lactamases. QPX7728 enhances the potency of multiple beta-lactams in beta-lactamase producing and spp. In this study we evaluated the in vitro activity of QPX7728 (8 μg/ml) combined with multiple beta-lactams against clinical isolates of with varying beta-lactam resistance mechanisms. Read More

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Erection of a New Genus and Species for the Pathogen of Hard Clams 'Quahog Parasite Unknown' (QPX): Mucochytrium quahogii gen. nov., sp. nov.

Protist 2021 02 29;172(1):125793. Epub 2021 Jan 29.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA. Electronic address:

Quahog Parasite Unknown (QPX) is a facultative parasite of the hard clam, Mercenaria mercenaria. Although it has been observed in clams since the 1960's and cultivated since the 1990's, conflicting reports on important aspects of its biology have prevented its formal description. 18S rRNA gene sequences identify QPX as a thraustochytrid, but its production of copious mucus is atypical for this group. Read More

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February 2021

Unraveling the mechanism for an amelogenin-derived peptide regulated hydroxyapatite mineralization via specific functional domain identification.

J Mater Chem B 2020 12 28;8(45):10373-10383. Epub 2020 Oct 28.

State Key Laboratory of Oral Diseases & National Clinical Research Centre for Oral Disease, Sichuan University, No. 14, Section 3 of Renmin Road South, Chengdu, China. and Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.

Amelogenin and its various derived peptides play important roles in promoting biomimetic mineralization of enamel. Previously, an amelogenin-derived peptide named QP5 was proved to be able to repair demineralized enamel. The objective here was to interpret the mechanism of QP5 by elucidating the specific function of each domain for further sequence and efficacy improvement. Read More

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December 2020

Identification of variants associated with hard clam, Mercenaria mercenaria, resistance to Quahog Parasite Unknown disease.

Genomics 2020 11 3;112(6):4887-4896. Epub 2020 Sep 3.

Marine Animal Disease Laboratory, School of Marine and Atmospheric Sciences, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-5000, USA. Electronic address:

Severe losses in aquacultured and wild hard clam (Mercenaria mercenaria) stocks have been previously reported in the northeastern United States due to a protistan parasite called QPX (Quahog Parasite Unknown). Previous work demonstrated that clam resistance to QPX is under genetic control. This study identifies single nucleotide polymorphism (SNP) associated with clam survivorship from two geographically segregated populations, both deployed in an enzootic site. Read More

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November 2020

SNP hot-spots in the clam parasite QPX.

BMC Genomics 2018 Jun 20;19(1):486. Epub 2018 Jun 20.

School of Marine and Atmospheric Sciences, Stony Brook University, NY, 11794-5000, USA.

Background: Quahog Parasite Unknown (QPX) is an opportunistic protistan pathogen of the clam Mercenaria mercenaria. Infections with QPX have caused significant economic losses in the Northeastern United States. Previous research demonstrated a geographic gradient for disease prevalence and intensity, but little information is available on the genetic diversity of the parasite throughout its distribution range. Read More

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Identification of clam plasma proteins that bind its pathogen Quahog Parasite Unknown.

Fish Shellfish Immunol 2018 Jun 30;77:214-221. Epub 2018 Mar 30.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, USA. Electronic address:

The hard clam (Mercenaria mercenaria) is among the most economically-important marine species along the east coast of the United States, representing the first marine resource in several Northeastern states. The species is rather resilient to infections and the only important disease of hard clams results from an infection caused by Quahog Parasite Unknown (QPX), a protistan parasite that can lead to significant mortality events in wild and aquacultured clam stocks. Though the presence of QPX disease has been documented since the 1960s, little information is available on cellular and molecular interactions between the parasite and the host. Read More

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On neutron activation analysis with γγ coincidence spectrometry.

J Radioanal Nucl Chem 2017 Oct 26;314(1):513-519. Epub 2017 Jul 26.

Chemical Sciences Division, National Institute of Standards and Technology, 100 Bureau Drive, MS 8395, Gaithersburg, MD 20899-8395, USA.

A new γγ coincidence system has been set up at NIST. It is operated with a digital data finder supported by new software developed at NIST. The system is used to explore possible enhancements in instrumental neutron activation analysis (INAA) and study applicability to neutron capture prompt gamma activation analysis (PGAA). Read More

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October 2017

Differential Gene Expression in Five Isolates of the Clam Pathogen, Quahog Parasite Unknown (QPX).

J Eukaryot Microbiol 2017 09 10;64(5):647-654. Epub 2017 Mar 10.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, 11794-5000, New York, USA.

Quahog parasite unknown (QPX) is a thraustochytrid protist that infects the hard clam, Mercenaria mercenaria, causing significant economic losses along the northeastern coast of North America. Previous investigations noted differences in growth dynamics and virulence in QPX cells from different geographic locations. In order to probe the molecular determinants for these variations, we investigated the transcriptomic profiles of five geographically distinct QPX isolates using custom 15k 60-mer oligonucleotide arrays. Read More

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September 2017

Identification and characterization of peptidases secreted by quahog parasite unknown (QPX), the protistan parasite of hard clams.

Dis Aquat Organ 2016 11;122(1):21-33

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Quahog parasite unknown (QPX) is a protistan parasite capable of causing deadly infections in the hard clam Mercenaria mercenaria, one of the most valuable shellfish species in the USA. QPX is an extracellular parasite found mostly in the connective tissue of clam mantle and, in more severe cases of infection, other clam organs. Histopathologic examinations revealed that QPX cells within clam tissues are typically surrounded by hollow areas that have been hypothesized to be, at least in part, a result of extracellular digestion of clam proteins by the parasite. Read More

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November 2016

Effect of "heat shock" treatments on QPX disease and stress response in the hard clam, Mercenaria mercenaria.

J Invertebr Pathol 2016 07 3;138:39-49. Epub 2016 Jun 3.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, USA. Electronic address:

The hard clam, Mercenaria mercenaria, is one of the most valuable commercial mollusk species along the eastern coast of the United States. Throughout the past 2 decades, the hard clam industry in the Northeast was significantly impacted by disease outbreaks caused by a lethal protistan parasite known as Quahog Parasite Unknown (QPX). QPX is an opportunistic pathogen and the infection has been shown to be a cold water disease, where warmer conditions (above 21°C) lead to disease reduction and clam healing. Read More

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Clam focal and systemic immune responses to QPX infection revealed by RNA-seq technology.

BMC Genomics 2016 Feb 27;17:146. Epub 2016 Feb 27.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, 11794-5000, USA.

Background: The hard clam Mercenaria mercenaria is an important seafood species widely exploited along the eastern coasts of the United States and play a crucial role in coastal ecology and economy. Severe hard clam mortalities have been associated with the protistan parasite QPX (Quahog Parasite Unknown). QPX infection establishes in pallial organs with the lesions typically characterized as nodules, which represent inflammatory masses formed by hemocyte infiltration and encapsulation of parasites. Read More

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February 2016

Infectious diseases of marine molluscs and host responses as revealed by genomic tools.

Philos Trans R Soc Lond B Biol Sci 2016 Mar;371(1689)

Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ 08349, USA.

More and more infectious diseases affect marine molluscs. Some diseases have impacted commercial species including MSX and Dermo of the eastern oyster, QPX of hard clams, withering syndrome of abalone and ostreid herpesvirus 1 (OsHV-1) infections of many molluscs. Although the exact transmission mechanisms are not well understood, human activities and associated environmental changes often correlate with increased disease prevalence. Read More

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Alterations of the immune transcriptome in resistant and susceptible hard clams (Mercenaria mercenaria) in response to Quahog Parasite Unknown (QPX) and temperature.

Fish Shellfish Immunol 2016 Feb 12;49:163-76. Epub 2015 Dec 12.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, 11794, USA. Electronic address:

Quahog Parasite Unknown (QPX) is a fatal protistan parasite that causes severe losses in the hard clam (Mercenaria mercenaria) fisheries along the northeastern coast of the US. Field and laboratory studies of QPX disease have demonstrated a major role for water temperature and M. mercenaria genetic origin in disease development. Read More

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February 2016

Characterisation of the secretome of the clam parasite, QPX.

Int J Parasitol 2015 Feb 31;45(2-3):187-96. Epub 2014 Dec 31.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA. Electronic address:

Secreted and cell surface-associated molecules play a major role in disease development processes and host-pathogen interactions, and usually determine the virulence of invading organisms. In this study, we investigated proteins secreted by quahog parasite unknown, a thraustochytrid protist that infects the hard clam, Mercenaria mercenaria. In silico analysis of quahog parasite unknown transcripts predicted over 1200 proteins to possess an amino-terminal signal peptide which directs proteins into the classical eukaryotic secretory pathway. Read More

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February 2015

Characterization of the transcriptome and temperature-induced differential gene expression in QPX, the thraustochytrid parasite of hard clams.

BMC Genomics 2014 Mar 28;15:245. Epub 2014 Mar 28.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Background: The hard clam or northern quahog, Mercenaria mercenaria, is one of the most valuable seafood products in the United States representing the first marine resource in some Northeastern states. Severe episodes of hard clam mortality have been consistently associated with infections caused by a thraustochytrid parasite called Quahog Parasite Unknown (QPX). QPX is considered as a cold/temperate water organism since the disease occurs only in the coastal waters of the northwestern Atlantic Ocean from Maritime Canada to Virginia. Read More

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Development of genomic resources for a thraustochytrid pathogen and investigation of temperature influences on gene expression.

PLoS One 2013 17;8(9):e74196. Epub 2013 Sep 17.

Department of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America.

Understanding how environmental changes influence the pathogenicity and virulence of infectious agents is critical for predicting epidemiological patterns of disease. Thraustochytrids, part of the larger taxonomic class Labyrinthulomycetes, contain several highly pathogenic species, including the hard clam pathogen quahog parasite unknown (QPX). QPX has been associated with large-scale mortality events along the northeastern coast of North America. Read More

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Assessing the photoprotective effectiveness of non-photochemical chlorophyll fluorescence quenching: a new approach.

Biochim Biophys Acta 2012 Jul 1;1817(7):977-82. Epub 2012 Apr 1.

School of Biological and Chemical Sciences, Queen Mary University of London, UK.

The photoprotective nature of non-photochemical quenching (NPQ) has not been effectively quantified and the major reason is the inability to quantitatively separate NPQ that acts directly to prevent photoinhibition of photosystem II (PSII). Here we describe a technique in which we use the values of the PSII yield and qP measured in the dark following illumination. We expressed the quantum yield of PSII (Φ(PSII)) via NPQ as: Φ(PSII)=qP×(Fv/Fo)/(1+Fv/Fo+NPQ). Read More

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Differential immune response in the hard clam (mercenaria mercenaria) against bacteria and the protistan pathogen QPX (quahog parasite unknown).

Fish Shellfish Immunol 2012 Jun 29;32(6):1124-34. Epub 2012 Mar 29.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

The immune response of the hard clam (quahog) Mercenaria mercenaria following challenge with live bacteria (Vibrio alginolyticus) and the protist QPX (Quahog Parasite Unknown) was investigated. The study also compared immune responses following QPX challenge in two different hard clam broodstocks exhibiting different degrees of susceptibility toward this parasite. Different immune and stress-related cellular and humoral factors were assessed including general hemocyte parameters (total and differential hemocyte counts, percentage of dead cells, reactive oxygen production, phagocytosis), parameters geared toward QPX (anti-QPX activity in plasma and hemocyte resistance to the cytotoxicity of QPX extracellular products). Read More

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Effects of salinity on hard clam (Mercenaria mercenaria) defense parameters and QPX disease dynamics.

J Invertebr Pathol 2012 May 15;110(1):73-82. Epub 2012 Feb 15.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

QPX (Quahog Parasite Unknown) is a protistan parasite affecting hard clams (Mercenaria mercenaria) along the Northeast coast of the United States. The fact that QPX disease epizootics are usually observed in field sites with high salinities led to the general assumption that salinity represents an important factor for disease distribution. This study was designed to investigate the effect of salinity on QPX disease development as well as constitutive and QPX-induced defense factors in M. Read More

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Effects of temperature on hard clam (Mercenaria mercenaria) immunity and QPX (Quahog Parasite Unknown) disease development: II. Defense parameters.

J Invertebr Pathol 2011 Feb 27;106(2):322-32. Epub 2010 Nov 27.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Quahog Parasite Unknown (QPX) is a protistan parasite affecting hard clams Mercenaria mercenaria along the Northeastern coast of the United States. The geographic distribution and occurrence of disease epizootics suggests a primary role of temperature in disease development. This study was designed to investigate the effect of temperature on constitutive and QPX-induced defense factors in M. Read More

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February 2011

Effects of temperature on hard clam (Mercenaria mercenaria) immunity and QPX (Quahog Parasite Unknown) disease development: I. Dynamics of QPX disease.

J Invertebr Pathol 2011 Feb 26;106(2):314-21. Epub 2010 Nov 26.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Quahog Parasite Unknown (QPX) causes disease and mortality in hard clams, Mercenaria mercenaria. Seasonality of QPX disease prevalence in the field and changes in QPX growth and survival in vitro suggest a role of temperature in the hard clam-QPX interaction and disease development. This study specifically examined the effect of temperature on QPX disease development and dynamics. Read More

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February 2011

Effect of environmental factors on survival and growth of quahog parasite unknown (QPX) in vitro.

J Invertebr Pathol 2010 Jun 19;104(2):83-9. Epub 2010 Feb 19.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Quahog parasite unknown (QPX) is a protistan microorganism associated with mass mortalities of hard clams (Mercenaria mercenaria) along the northeastern coasts of the United States and maritime Canada. Because several studies indicate modulatory effects of prevailing environmental parameters on disease outbreaks, this study tested the effect of major environmental parameters (temperature, salinity and oxygen concentration; individually or combined) on QPX survival in artificial seawater and parasite growth in culture media in vitro. Three QPX isolates from two different geographic locations were compared. Read More

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Combined effects of a parasite, QPX, and the harmful-alga, Prorocentrum minimum on northern quahogs, Mercenaria mercenaria.

Mar Environ Res 2010 Jun 29;69(5):337-44. Epub 2009 Dec 29.

University of Connecticut, Department of Marine Sciences, Groton, CT 06340, USA.

Northern quahogs, Mercenaria mercenaria (L.), frequently are infected with the parasite Quahog Parasite Unknown (QPX, Labyrintohomorpha, Thraustochytriales), which can cause morbidity and mortality of the quahogs. Possible interactions between this parasitic disease and exposure to the harmful dinoflagellate Prorocentrum minimum in M. Read More

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Identification and expression of differentially expressed genes in the hard clam, Mercenaria mercenaria, in response to quahog parasite unknown (QPX).

BMC Genomics 2009 Aug 14;10:377. Epub 2009 Aug 14.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Background: The hard clam, Mercenaria mercenaria, has been affected by severe mortality episodes associated with the protistan parasite QPX (Quahog Parasite Unknown) for several years. Despite the commercial importance of hard clams in the United States, molecular bases of defense mechanisms in M. mercenaria, especially during QPX infection, remain unknown. Read More

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Cytotoxicity of quahog parasite unknown (QPX) toward hard clam ( Mercenaria mercenaria) haemocytes and interactions between different pathogen isolates and host strains.

Parasitology 2009 Sep 23;136(11):1281-9. Epub 2009 Jul 23.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

The ability of pathogens to neutralize host defence mechanisms represents a fundamental requisite in the successful establishment of an infection. Host-pathogen interactions between quahog parasite unknown (QPX) and its hard clam host are poorly understood. Our prior in vivo investigations have shown that different QPX isolates display varying levels of pathogenicity toward clams. Read More

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September 2009

Quantitative real-time PCR assay for QPX (Thraustochytriidae), a parasite of the hard clam (Mercenaria mercenaria).

Appl Environ Microbiol 2009 Jul 22;75(14):4913-8. Epub 2009 May 22.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

We developed a real-time quantitative PCR (qPCR) assay targeting the rRNA internal transcribed spacer region of the hard clam pathogen QPX. The qPCR assay was more sensitive than was histology in detecting clams with light QPX infections. QPX was detected in 4 of 43 sediment samples but in none of 40 seawater samples. Read More

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Environmental distribution and persistence of Quahog Parasite Unknown (QPX).

Dis Aquat Organ 2008 Sep;81(3):219-29

Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.

Quahog Parasite Unknown (QPX) is the cause of mass mortality events of hard clams Mercenaria mercenaria from Virginia, USA, to New Brunswick, Canada. Aquaculture areas in Massachusetts, USA, have been particularly hard hit. The parasite has been shown to be a directly infective organism, but it is unclear whether it could exist or persist outside of its clam host. Read More

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September 2008

Modulatory effects of hard clam (Mercenaria mercenaria) tissue extracts on the in vitro growth of its pathogen QPX.

J Invertebr Pathol 2009 Jan 7;100(1):1-8. Epub 2008 Oct 7.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA.

Quahog parasite unknown (QPX) is a fatal protistan parasite affecting cultured and wild hard clams Mercenaria mercenaria along the northeastern coasts of the USA and maritime Canada. Field investigations and laboratory transmission studies revealed some variations in the susceptibility of different hard clam stocks to QPX infection. In this study, we used in vitro QPX cultures to investigate the effect of plasma and tissue extracts from two different clam stocks on parasite survival and growth. Read More

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January 2009

Prevalence of Perkinsus marinus (dermo), Haplosporidium nelsoni (MSX), and QPX in bivalves of Delaware's inland bays and quantitative, high-throughput diagnosis of dermo by QPCR.

J Eukaryot Microbiol 2007 Nov-Dec;54(6):520-6

College of Marine and Earth Studies, University of Delaware, Lewes, Delaware 19958, USA.

Restoration of oyster reef habitat in the Inland Bays of Delaware was accompanied by an effort to detect and determine relative abundance of the bivalve pathogens Perkinsus marinus, Haplosporidium nelsoni, and QPX. Both the oyster Crassostrea virginica and the clam Mercenaria mercenaria were sampled from the bays. In addition, oysters were deployed at eight sites around the bays as sentinels for the three parasites. Read More

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January 2008

Molecular genetic variation within and among isolates of QPX (Thraustochytridae), a parasite of the hard clam Mercenaria mercenaria.

Dis Aquat Organ 2007 Sep;77(2):159-68

Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA.

The thraustochytrid known as QPX (Quahog Parasite Unknown) has sporadically caused disease in the hard clam Mercenaria mercenaria along the east coast of North America since the 1960s. We hypothesized that genetically distinct QPX strains might be responsible for outbreaks of QPX disease in different areas and tested this hypothesis by comparing several QPX isolates recovered from the recent outbreak in Raritan Bay, New York with QPX strains isolated from 2 outbreaks in Massachusetts, USA. There was no variation in small subunit rDNA (SSU rDNA), 5. Read More

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September 2007