ABSTRACT
To evaluate the sensitivity and specificity of assays used to screen blood for antibody to hepatitis C virus (HCV) infection, the International Consortium for Blood Safety (ICBS) established fully characterized CBS panels. lCBS collected and characterized 1007 anti-HCV-positive plasma units from geographically diverse origins by ELISA, RIBA, RT-PCR, and sequence-based genotyping, 539 of which met the definition of a true positive. Of these, 200 confirmed positive plasma units, representing the 6 major HCV genotypes, were selected to assemble the true-positive constituents of the panel. The negative panel comprises 181 plasma units collected from the USA. The panels have proved valuable for determining the performance of anti-HCV assays thus permitting national authorities, especially in resource-limited countries, to make informed decisions on selection of affordable and reliable assays.
Subject(s)
Enzyme-Linked Immunosorbent Assay/methods , Hepatitis C/diagnosis , Hepatitis C/virology , Mass Screening/methods , Reverse Transcriptase Polymerase Chain Reaction/methods , Transfusion Reaction , Blood Donors , Blood Transfusion/standards , Enzyme-Linked Immunosorbent Assay/standards , Genotype , Global Health , Hepacivirus/genetics , Hepatitis C/blood , Hepatitis C/epidemiology , Humans , International Agencies , Mass Screening/standards , Molecular Epidemiology , Nucleotide Mapping , Phylogeny , RNA, Viral , Reverse Transcriptase Polymerase Chain Reaction/standards , Safety Management/organization & administration , Sensitivity and SpecificityABSTRACT
To evaluate the sensitivity and specificity of assays used to screen blood for antibody to hepatitis C virus [HCV] infection, the International Consortium for Blood Safety [ICBS] established fully characterized ICBS panels. ICBS collected and characterized 1007 anti-HCV-positive plasma units from geographically diverse origins by ELISA, RIBA, RT-PCR, and sequence-based genotyping, 539 of which met the definition of a true positive. Of these, 200 confirmed positive plasma units, representing the 6 major HCV genotypes, were selected to assemble the true-positive constituents of the panel. The negative panel comprises 181 plasma units collected from the USA. The panels have proved valuable for determining the performance of anti-HCV assays thus permitting national authorities, especially in resource-limited countries, to make informed decisions on selection of affordable and reliable assays
Subject(s)
Safety Management , Sensitivity and Specificity , Mass Screening , Enzyme-Linked Immunosorbent Assay , Hepatitis C , Reverse Transcriptase Polymerase Chain Reaction , Blood TransfusionABSTRACT
A growing body of information has provided insights into the mechanisms by which the oral streptococci maintain their niches in the human mouth. In at least one case, Streptococcus mutans, the organism apparently uses a panel of proteins to survive in acidic conditions while it promotes the formation of dental caries. Oral streptococci, which are not as inherently resistant to acidification, use protective schemes to ameliorate acidic plaque pH values. Existing information clearly shows that while the streptococci are highly related, very different strategies have evolved for them to take advantage of their particular location in the oral cavity. The picture that emerges is that the acid-adaptive regulatory mechanisms of the oral streptococci differ markedly from those used by Gram-negative bacteria. What future research must determine is the extent and complexity of the acid-adaptive systems in these organisms and how they permit the organisms to maintain themselves in the face of a low-pH environment and the microbial competition present in their respective niches.
Subject(s)
Mouth/microbiology , Streptococcus/genetics , Streptococcus/physiology , Acids/metabolism , Adaptation, Physiological/genetics , Adenosine Triphosphatases/biosynthesis , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/physiology , Bacterial Proteins/biosynthesis , Bacterial Proteins/genetics , Bacterial Proteins/physiology , DNA Repair , Gene Expression Regulation, Enzymologic , Genes, Bacterial , Humans , Hydrogen-Ion Concentration , Hydrolases/biosynthesis , Hydrolases/genetics , Hydrolases/physiology , Streptococcus/enzymology , Urease/biosynthesis , Urease/genetics , Urease/physiologyABSTRACT
The strategies employed by oral streptococci to resist the inimical influences of acidification reflect the diverse and dynamic niches of the human mouth. All of the oral streptococci are capable of rapid degradation of sugar to acidic end-products. As a result, the pH value of their immediate environment can plummet to levels where glycolysis and growth cease. At this point, the approaches for survival in acid separate the organisms. Streptococcus mutans, for example, relies on its F-ATPase, to protect itself from acidification by pumping protons out of the cells. S. salivarius responds by degrading urea to ammonia and S. sanguis produces ammonia by arginolysis. The mechanisms by which these organisms regulate their particular escape route are now being explored experimentally. The picture that emerges is that the acid-adaptive regulatory mechanisms of the oral streptococci differ markedly from those employed by Gram-negative bacteria. What remains to be elucidated are the breadth of the acid-response systems in these organisms and how they permit the microbes to sustain themselves in the face of low pH and the bacterial competition present in their respective niches. In this article, we summarize reports concerning the means by which oral streptococci either utilize acidification to subdue their competitors or protect themselves until pH values return to a more favorable level.
