Nucleic Acid Amplification Techniques
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Tuberculous Otomastoiditis
- Authors: Jonathan M. Hand, George A. Pankey
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Citation: Hand J, Pankey G. 2016. Tuberculous otomastoiditis. 4(6): doi:10.1128/microbiolspec.TNMI7-0020-2016
- DOI 10.1128/microbiolspec.TNMI7-0020-2016
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Abstract:
Tuberculous otitis media and mastoiditis, or tuberculous otomastoiditis, is a rare but well-described infectious process occasionally affecting individuals in the United States but more frequently seen in countries where tuberculosis is endemic. Infection may be primary and occur through mucus aspirated through the Eustachian tube. Alternatively, organisms may secondarily infect the nasopharynx when expectorated from the lungs and, less frequently, may be hematogenously spread. Chronic otorrhea and hearing loss are common symptoms, and extensive perforation of the tympanic membranes and facial nerve paralysis are routinely described. Diagnosis is made by direct culture of Mycobacterium tuberculosis, although more recently, molecular techniques have been used. Successful treatment of tuberculous otomastoiditis routinely involves surgical intervention combined with prolonged antituberculosis therapy.
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Epstein-Barr Virus
- Authors: Andrew Nowalk, Michael Green
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Citation: Nowalk A, Green M. 2016. Epstein-barr virus. 4(3): doi:10.1128/microbiolspec.DMIH2-0011-2015
- DOI 10.1128/microbiolspec.DMIH2-0011-2015
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This review covers relevant clinical and laboratory information relating to Epstein-Barr virus (EBV) infections in immunocompromised hosts. It describes the epidemiology and clinical manifestations with a primary focus on disease in solid organ and stem cell transplant recipients. The review pays particular attention to diagnostic approaches, including serologic testing and imaging, with an expanded discussion on the role of measuring the EBV load in peripheral blood, identifying both strengths and limitations of this assay. Additional attention is paid to potential additional strategies of immunologic monitoring that may enhance the performance of EBV load monitoring.
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To the Barricades: the Molecular Revolution
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Source: To Catch a Virus , pp 293-338
Publication Date :
January 2013
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Abstract:
In 1981, two reports from the west and east coasts of the United States marked the beginning of the acquired immunodeficiency syndrome (AIDS) epidemic by the lethal, immunosuppressant retrovirus, human immunodeficiency virus (HIV). Just four years later, in 1985, Kary Mullis and his colleagues described the polymerase chain reaction (PCR), which contributed to an explosion of research on HIV and AIDS. The story begins with an overview of the molecular genetics revolution, which was fundamental to what ultimately became molecular diagnostic virology. Key to management of infected individuals has been determination of viral load, detected by nucleic acid amplification techniques such as the PCR. Prior to the explosive commercial development of PCR and other nucleic acid amplification tests, certain molecular nucleic acid methods were explored for clinical diagnostic virology. Diagnostic virology played a central role in patient management, in pharmacotherapy, and in researching the epidemiology of circulating viral infections. Likewise, management of infections with viruses such as HIV, cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) has been significantly improved. The current trend is to devise user-friendly and walk-away molecular tests allowing more clinical laboratories to offer viral diagnostic services. From transmission studies of yellow fever with human volunteers to the application of high-throughput sequencing, diagnostic virology sits astride the confluence of advances in science and the challenges presented by human disease.
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Intestinal and Urogenital Amebae, Flagellates, and Ciliates
- Authors: Amy L. Leber, Susan Novak-Weekley
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Source: Manual of Clinical Microbiology, 10th Edition , pp 2149-2171
Publication Date :
January 2011
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This chapter talks about the intestinal amebae and urogenital amebae, flagellates, and ciliates. It is noteworthy that Dientamoeba fraglis, once classified as an ameba, is now grouped with the flagellates. All diagnostic stages of the amebae (trophozoite and cyst) can be detected in fecal specimens, the most common specimen submitted to the laboratory. Entamoeba histolytica and the other Entamoeba spp. are classified as belonging to the phylum Amoebozoa, subphylum Conosa, class Archamoebea, order Euamoebida. Some flagellates are commensals that reside in the intestinal tract and are harmless to the individual. For the detection of flagellates and ciliates, laboratories predominantly receive stool specimens for microscopic examination. The flagellates have greater morphologic diversity relative to one another than do the amebae, making determination of the genus easier. Despite the lack of external flagella, this parasite is currently classified as a flagellate but has historically been grouped with the amebae. Two additional nonpathogenic intestinal flagellates are E. hominis and Retortamonas intestinalis. Clinical laboratories are now given more choices for testing in diagnostic parasitology, with assays ranging from microscopy, culture, antigen detection, and nucleic acid amplification techniques. Molecular biology has the promise to deliver more sensitive and specific methods but to date, these methods have not been fully adapted to the clinical diagnostic laboratory.
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Haemophilus
- Authors: Nathan A. Ledeboer, Gary V. Doern
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Source: Manual of Clinical Microbiology, 10th Edition , pp 588-602
Publication Date :
January 2011
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While the number of Haemophilus species described greatly exceeds the number of human pathogens, eight species affecting humans currently included in this genus are H. influenzae, H. aegyptius, H. ducreyi, H. pittmaniae, H. parainfluenzae, H. haemolyticus, H. parahaemolyticus, and H. paraphrohaemolyticus. Aggregatibacter aphrophilus, Aggregatibacter paraphrophilus, and Aggregatibacter segnis were formerly included in the genus Haemophilus but have recently been reclassified into the genus Aggregatibacter (formerly Actinobacillus) based on molecular taxonomy. In the absence of the recently reclassified species, significant genetic diversity still exists in the Haemophilus genus. Haemophilus influenzae may be found as part of the commensal bacterial flora of the mucosal surfaces of the upper respiratory tracts (URT) of many healthy individuals. Several molecular methods, including 16S rRNA gene sequencing, polymerase chain reaction (PCR), and fluorescence in-site hybridization have been described in the literature as being effective tools for the species identification of Haemophilus when performed on organisms recovered in culture. Other molecular methods for typing have also been applied to Haemophilusspecies. In one study evaluating the performance of intergenic dyad sequence (IDS)-PCR with 69 NTHi isolates, the assay demonstrated 65 different banding patterns that were epidemiologically classified as fingerprints similar to those obtained by pulsed-field gel electrophoresis (PFGE).
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Molecular Microbiology
- Authors: Frederick S. Nolte, Angela M. Caliendo
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Source: Manual of Clinical Microbiology, 10th Edition , pp 27-59
Publication Date :
January 2011
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Abstract:
Technological advances in realtime PCR techniques, automation, nucleic acid sequencing, multiplex analysis, and mass spectrometry have reinvigorated the field and created new opportunities for growth. Molecular microbiology is the leading area in molecular pathology in terms of both the numbers of tests performed and clinical relevance. This chapter covers amplified- and nonamplified-probe techniques, postamplification detection and analysis, clinical applications of these techniques. It also discusses the special challenges and opportunities that these techniques provide for the clinical laboratory. Although probes can range from 15 to thousands of nucleotides in size, synthetic oligonucleotides of less than 50 nucleotides are commonly incorporated into commercial kits. In most clinical applications, formalin-fixed, paraffin-embedded tissue sections are used. Nonamplified-probe techniques are used most effectively in culture confirmation assays for mycobacteria and systemic dimorphic fungi. Strategies other than PCR, are based on signal, target, or probe amplification, and have sensitivity unparalleled in laboratory medicine, have created new opportunities for the clinical laboratory to have an effect on patient care, and have become the new “gold standards” for laboratory diagnosis of many infectious diseases. In signal amplification methods, the concentration of the probe or target does not increase. Signal amplification assays have several advantages over target amplification assays. The target amplification systems share certain fundamental characteristics. They use enzyme-mediated processes, in which a single enzyme or multiple enzymes synthesize copies of target nucleic acid. In these techniques, the amplification products are detected by two oligonucleotide primers that bind to complementary sequences on opposite strands of double-stranded targets.
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Borrelia *
- Author: Martin E. Schriefer
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Source: Manual of Clinical Microbiology, 10th Edition , pp 924-940
Publication Date :
January 2011
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Borreliosis, in the form of louse-borne relapsing fever (LBRF), has been the cause of massive epidemics as recently as the early 1900s. Tick-borne relapsing fever (TBRF) and Lyme borreliosis (LB) are caused by over a dozen Borrelia species and were first described about 100 years ago. There is a high prevalence of B.afzelii among human skin isolates from Europe, whereas isolates from cerebrospinal fluid (CSF) in Europe are most often B.garinii. A few studies have reported the detection of Borrelia species (B.valaisiana, B.spielmanii, and B. lusitaniae) in patient samples in Europe. The genomes of the borreliae are unusual among prokaryotes in having a small linear chromosome of approximately 1,000 kb and both linear and circular plasmids. Two colinear plasmids (lp54 and cp26) seem to belong to the basic genome inventory of the Borrelia species that causes Lyme disease. The ecological components that maintain Borrelia species in nature are quite diverse and are spread throughout the world. This chapter talks about collection, transport, and storage of specimens. Direct microscopic visualization of borreliae in clinical samples is applicable only to cases of relapsing fever. The chapter describes molecular techniques and immunological techniques for identifying Borrelia species, and explains about the serologic test. The antimicrobial susceptibility of Borrelia species has been studied intensively in vitro. Standard methods for the determination of the minimal bactericidal concentration have not been established. Clinical criteria (case history and clinical findings) are decisive factors in the diagnosis and ordering of microbiological laboratory testing.
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Chlamydiaceae *
- Authors: Charlotte Gaydos, Andreas Essig
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Source: Manual of Clinical Microbiology, 10th Edition , pp 986-1000
Publication Date :
January 2011
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The Chlamydiaceae contain the known human pathogens Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci as well as organisms such as C. abortus and C. felis that have been associated only rarely with human infections. An overview about ranges of sensitivity and specificity for common diagnostic tests for C. trachomatis in urogenital specimens is provided in this chapter. Problems associated with cell culture isolation of chlamydiae, including technical complexity and long turnaround time, and stringent requirements related to collection, transport, and storage of specimens have driven the development of commercially available nonculture methods that have found widespread application in many routine laboratories. The basic procedure for detection of isolated chlamydiae involves demonstration of intracytoplasmic inclusions by fluorescent-antibody staining that provides both morphological and immunological identification of chlamydiae. Serologic testing may be helpful in the diagnosis of human ornithosis, LGV, neonatal pneumonia caused by C. trachomatis, and respiratory C. pneumoniae infections. The most commonly used serological assay formats include the complement fixation (CF) test, the MIF test, and the EIA to detect immunoglobulin M (IgM), IgA, IgG, or total classes of antibodies, with either family, species, or serotype specificity. Evaluation of antimicrobial resistance and potential clinical treatment failure in chlamydial infection is hampered by the lack of standardized antimicrobial susceptibility tests and the fact that in vitro resistance does not correlate with the patient’s clinical outcome.
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Algorithms for Detection and Identification of Viruses
- Authors: Marie Louise Landry, Angela M. Caliendo, Christine C. Ginocchio, Yi-Wei Tang, Alexandra Valsamakis
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Source: Manual of Clinical Microbiology, 10th Edition , pp 1297-1301
Publication Date :
January 2011
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Abstract:
This chapter analyses methods focused on conventional cell cultures, classical serologic techniques, and light and electron microscopy. Novel detection methods have permitted the diagnosis of multiple respiratory viruses in a single multiplex PCR test. Quantitative monitoring of viral load in blood has become more widely applied due to implementation of real-time PCR techniques. As tests become more sensitive, low levels of clinically irrelevant or nonviable viruses may be detected and can be misleading to clinicians. Similarly, interpreting the clinical relevance of multiple viral pathogens in the same sample when relative quantification is not available is problematic. Laboratories need to choose which tests to offer. Selecting the appropriate test will depend on the viruses sought, sample site, clinical presentation, clinical purpose, patient characteristics, and disease prevalence. Laboratories must recognize the uses and also the limitations of each test in order to guide clinicians in interpreting the results. Due to the speed of methodological change and the continuing discovery of new viruses and new therapies, keeping abreast of the most recent literature is strongly recommended.
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Arboviruses *
- Authors: Robert S. Lanciotti, Theodore F. Tsai
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Source: Manual of Clinical Microbiology, 10th Edition , pp 1488-1503
Publication Date :
January 2011
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Important antigenic determinants have been elucidated for the most important arboviruses, and virus- and group-specific monoclonal antibodies are available for taxonomic and diagnostic purposes. Serologic cross-relationships are most evident in hemagglutination inhibition and binding assays, e.g., enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody tests, and occur to a lesser extent in complement fixation tests. The epidemiologic and clinical characteristics of the medically important arboviruses are summarized in this chapter. Immunoglobulin M capture ELISAs for arboviral central nervous system infections transmitted in the United States are offered by several reference and some state public health laboratories. A number of nucleic acid amplification strategies have been developed for the detection and identification of medically important arboviruses, including standard RT-PCR (with agarose gel analysis), real-time RT-PCR using fluorescent probes, nucleic acid sequence-based amplification (NASBA), and the recently developed reverse transcription-loop-mediated isothermal amplification (LAMP) method. Novel arboviruses continue to be discovered, usually as orphan viruses first identified in vector surveys but, remarkably, also from human clinical specimens. The majority of arboviruses are lethal to suckling (2 to 3-day-old) mice, which exhibit signs of illness, paralysis, and death within days to 2 weeks after intracerebral inoculation. While identification of arboviral isolates previously depended upon their antigenic characterization, PCR and other molecular tests are now available for many of the medically important arboviruses.
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Epstein-Barr Virus *
- Author: Barbara C. Gärtner
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Source: Manual of Clinical Microbiology, 10th Edition , pp 1575-1584
Publication Date :
January 2011
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This chapter focuses on Epstein-Barr virus (EBV) that is a member of the Herpesviridae and belongs to the subfamily Gammaherpesvirinae, replicating in epithelial cells and establishing long-term latency in lymphocytes like its closest human-pathogenic relative, human herpesvirus 8. EBV nuclear antigen 1 (EBNA1), EBNA2, EBNA3 (also referred to as EBNA3a), EBNA4 (EBNA3b), EBNA5 (EBNALP), EBNA6 (EBNA3c), and latent membrane proteins (LMP1, -2A, and -2B) may be expressed in B cells. Four types of B-cell latency have been defined, based on various levels of expression of the latency-associated proteins. During lytic replication more than 70 proteins are expressed, including the virus capsid antigens (VCA) and the early antigens used in diagnostics. Nucleic acid detection techniques (NAT) might be applied to blood, cerebrospinal fluid (CSF), or biopsy samples. A wide variety of detection methods are available, ranging from in situ hybridization on frozen or paraffin sections through cytohybridization on cell suspensions, dot blot hybridization, Southern blot hybridization, and nucleic acid amplification techniques (NAAT). The most commonly used clinical diagnostic tools for direct detection of EBV are NAAT. Quantitative real-time PCR is the most popular method today for EBV monitoring in patients at risk for EBV-associated disorders. Individual viral isolates can be characterized by molecular techniques on the basis of polymorphism of the EBNA1 and EBNA3 genes. Patients with X-linked lymphoproliferative syndrome have typically a high viral load and do not develop EBNA antibodies. The ultimate diagnosis, however, is based on genetic analysis for a variety of mutations in the SH2D1A gene domain.
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In Vitro Nucleic Acid Amplification Techniques
- Authors: Vivekanand Datta, Randall T. Hayden
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Source: Molecular Microbiology , pp 33-61
Publication Date :
January 2011
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Nucleic acid amplification (NAA) techniques have come of age. The specific amplification and detection of an oligonucleotide sequence went from the fictional to the mundane in the span of two decades. By looking at the theoretical basis for each method, NAA techniques can be placed into one of two broad categories: (i) target amplification systems, including PCR, ligase chain reaction (LCR), self-sustaining sequence amplification (3SR), nucleic acid sequence-based amplification (NASBA), transcription-based amplification system (TAS), transcription-mediated amplification (TMA), strand displacement amplification (SDA), and loop-mediated isothermal amplification (LAMP); and (ii) signal amplification systems (including probe amplification methods), such as branched-DNA technologies (bDNA) and cleavage-based signal amplification (cycling probe technologies [CPT] and Invader assays). Proofreading may help maintain fidelity of replication, and its absence can result in a relatively high rate of nucleotide incorporation errors (misincorporation), most relevant when starting with low target numbers. Misincorporation can produce amplicon mismatched to detection probes and can also result in inefficient amplification (especially when longer genetic stretches are targeted), due to primer mismatch in subsequent amplification rounds. Successful ligation relies on contiguous positioning and correct base pairing of the 3' and 5' ends of oligonucleotide probes on a target DNA molecule. The reliability of sequence data has improved, and the taxonomic and cytogenetic characterization of microorganisms has advanced tremendously. These improvements give the tools to allow the rapid and increasingly routine development of molecular methods for the identification, quantification, and characterization of microorganisms.
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Update on the Detection and Characterization of Bacterial Pathogens by Nucleic Acid Amplification
- Authors: K. Loens, H. Goossens, M. Ieven
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Source: Molecular Microbiology , pp 355-381
Publication Date :
January 2011
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Real-time-based platforms currently offer numerous advantages over conventional nucleic acid amplification techniques (NAATs) such as higher speed, less handling of PCR products, decreased risk of false-positive results due to carryover contamination, and the capability to quantify results. This chapter reviews some updates on the detection by NAAT of some relevant individual agents alone, and associated with clinical syndromes, with emphasis on the detection of respiratory agents, particularly the atypical pathogens Mycobacterium pneumoniae, Chlamydophila pneumoniae, Legionella spp., and Bordetella pertussis but also Streptococcus pneumoniae, for which also quantitative real-time amplification is discussed. Given the many alternative amplification protocols proposed for some applications, such studies are clearly needed. Although such studies are often lacking, new-generation molecular techniques are gradually replacing tissue culture and even conventional PCRs as the gold standard for the diagnosis of respiratory infections and for the detection of particular individual bacterial pathogens, as is further reviewed in this chapter. A recent development is the application of PCR for detecting the family of Haemophilus integrating conjugative elements among antibiotic-resistant Haemophilus influenzae type b directly to cerebrospinal fluid (CSF) to diagnose Haemophilus influenzae type b meningitis and predict the organism's susceptibility, irrespective of culture results. The potential of pyrosequencing after broad-range PCR was successfully investigated by Jordan for the identification of bacterial pathogens responsible for sepsis in neonates.
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Molecular Approaches to the Diagnosis of Meningitis and Encephalitis
- Authors: Karen C. Bloch, Yi-Wei Tang
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Source: Molecular Microbiology , pp 767-784
Publication Date :
January 2011
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This chapter reviews various diagnostic tests available for central nervous system (CNS) infections and provides a detailed discussion of specific molecular approaches to the most common organisms causing meningitis and encephalitis in the United States. A vast array of organisms have been associated with encephalitis, including bacteria, fungi, viruses, and protozoa. Just as meningitis and encephalitis localize to distinct compartments of the CNS, the pathogens causing these two syndromes differ, and the respective microbiologies of meningitis and encephalitis are discussed separately. While the chapter focuses on the use of molecular assays for diagnosis of CNS infection, traditional microbiological diagnostic approaches continue to play an important role in pathogen identification and are complementary to nucleic acid amplification techniques. A DNA probe array has been developed for the simultaneous identification of herpesviruses, enteroviruses, and flaviviruses after several PCR amplifications. Nucleic acid amplification techniques have markedly improved the identification of CNS infections caused by viral and fastidious bacterial pathogens. Molecular techniques such as PCR allow rapid diagnosis, with consequent improvement of outcomes and cost savings. Results of molecular diagnostic testing for CNS infections must be interpreted in the context of the individual patient presentation and clinical illness, and close cooperation between the laboratory and the clinician is required for optimal use of these technologies.
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Contents
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Source: Molecular Microbiology
Publication Date :
January 2011
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No descriptions available.
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Index
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Source: Molecular Microbiology
Publication Date :
January 2011
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No descriptions available.
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Tuberculosis
- Authors: Gerhard Walzl, Paul Van Helden, Philip R. Botha
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Source: The Immune Response to Infection , pp 623-631
Publication Date :
January 2011
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Approximately one-third of the world’s population is thought to harbor latent forms of tuberculosis and the resultant huge reservoir for future disease. The recent increase in multidrug resistant disease and a dangerous interplay between tuberculosis and human immunodeficiency virus (HIV) infection continues to pose serious challenges for health care in the years to come. M. tuberculosis is transmitted by the inhalation of small droplet nuclei, which are aerosolized infectious particles generated by coughing, talking, and sneezing. A minority of patients with tuberculosis, who are started on highly active antiretroviral therapy (HAART) experience immune reconstitution disease (IRD) due to rapid restoration of the immune system with an increased response to mycobacterial antigens. To be valuable as a surrogate endpoint, a biomarker should measure an event that is directly involved in pathogenesis or protection and should change early during treatment. Early bactericidal activity (EBA) is used in the early evaluation of new tuberculosis drugs and is based on the rate of fall of colony-forming unit counts of M. tuberculosis (log10cfu/day) in overnight sputum samples that are collected before and on alternate days of treatment, up to day 14. A host of nonspecific markers have been described that appear promising as biomarkers for tuberculosis. The extent of the tuberculosis problem that exists today represents an affront to modern society. New tools are urgently needed and only multidisciplinary approaches that include all sectors of healthcare providers and researchers stand a chance to address the problem effectively.
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Tuberculous Otomastoiditis
- Author: George A. Pankey
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Source: Tuberculosis and Nontuberculous Mycobacterial Infections, Sixth Edition , pp 266-268
Publication Date :
January 2011
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Tuberculous otitis media and tuberculous mastoiditis occur together as a single disease process and are referred to as tuberculous otomastoiditis. Most of the medical literature on tuberculous otomastoiditis is from Europe and Asia, where the disease is more prevalent. The chapter discusses pathogenesis and pathology of tuberculous otomastoiditis. Tuberculous otomastoiditis may be masked by suprainfection with other bacteria as well as by systemic antituberculous therapy. The diagnosis of tuberculous otomastoiditis is considered confirmed by culture of Mycobacterium tuberculosis from the local discharge or biopsy sample. Once the diagnosis of tuberculous otomastoiditis is made, the combined talents of the primary care physician, an ear, nose, and throat surgeon, and an infectious disease specialist are required for optimum therapy. Isoniazid plus rifampin is the preferred antituberculous therapy, with pyrazinamide added for the first 2 months. Ethambutol is also usually given until resistant M. tuberculosis is ruled out. In addition to obtaining tissue for diagnosis, the surgeon may have a role in therapy by removing a nidus of infected debris. Complications mandating surgical approach include facial nerve paralysis, subperiosteal abscess, labyrinthitis, persistent postauricular fistula, and extension of infection into the central nervous system. After therapy is completed, reconstructive procedures may improve hearing in certain patients.
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Tuberculous Lymphadenitis and Parotitis
- Author: W. Garrett Hunt
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Source: Tuberculosis and Nontuberculous Mycobacterial Infections, Sixth Edition , pp 293-300
Publication Date :
January 2011
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The incidence of tuberculosis has increased worldwide, resulting in an increased incidence of tuberculous lymphadenitis. Tuberculous infection in the parotid gland usually develops following infection of intraparotid lymph nodes. As the capsule of the infected lymph tissue breaks down, parotitis may ensue. Historically, lymph node and parotid tuberculosis was caused mainly by Mycobacterium bovis, but nearly all tuberculous lymphadenitis is now due to M. tuberculosis. Symptoms associated with tuberculous lymphadenitis depend largely on the location of involved nodes. Differential diagnosis of tuberculous lymphadenitis or parotitis is extensive. Tuberculin skin testing is the most definitive noninvasive diagnostic procedure, yielding positive results in more than 90% of persons with tuberculous lymphadenitis. When diagnosis of tuberculous lymphadenitis remains in doubt, biopsy material must be submitted for histology, culture, and potentially PCR. Cytologic findings identify granulomatous changes in 50 to 80% of patients with tuberculous lymphadenitis, but acid-fast bacilli are identified in only 30 to 60% and cultures are positive for only 20 to 80%. A recent systematic review found that nucleic acid amplification tests for tuberculous lymphadenitis produce highly variable and inconsistent results, precluding the determination of clinically meaningful results. Management of tuberculous lymphadenitis and parotitis involves appropriate use of antituberculous chemotherapy with the judicious use of surgical excision in a minority of patients. There are no published trials of therapy for parotitis, so guidelines for lymphadenitis should be followed. Treatment involves the use of combination antituberculous chemotherapy, with occasional need for surgical excision.
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Potential Use of Bacteriophages as Indicators of Water Quality and Wastewater Treatment Processes
- Authors: Francisco Lucena, Juan Jofre
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Source: Bacteriophages in the Control of Food-and Waterborne Pathogens , pp 103-118
Publication Date :
January 2010
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Viruses and phages in water and the solid compartments undergo inactivation by both natural and human-introduced physical, chemical, and biological stressors. In primary sedimentation, flocculation-aided sedimentation, activated sludge digestion, activated sludge digestion plus precipitation, and upflow anaerobic sludge blanket processes, the die-off of the microorganisms seems to play a minor role in the reduction in counts. Viruses and bacteriophages persist longer than conventional bacterial indicators in water environments, and their persistence resembles that of viruses, as shown by model experiments and by the decreases in ratios between the numbers of conventional bacterial indicators and of viruses and phages in water environments with aged pollutants, either surface water. Bacteriophages infecting enteric bacteria have been reported in drinking water that fulfill the quality criteria based on bacterial indicators. Most likely, the application of advanced mathematical models such as artificial neural networks or support vector machines will reduce the uncertainty and give much better information about relationships between indicator bacteriophages and human viruses. In conclusion, it can be stated that, though not perfect, bacteriophages infecting enteric bacteria are useful additional indicators for water quality control because of their numbers in fecally contaminated water and their outcome in water environments and water treatment plants.