Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

Human Herpesviruses 6 and 7 (Roseola, Exanthem Subitum)

Human Herpesvirus 6 Human herpesvirus 6 (HHV-6) was first isolated from the peripheral blood lymphocytes of adults with lymphoproliferative diseases and HIV infection and was named human B-lymphotropic virus. When additional isolates were identified in CD4 + lymphocytes, further characterization indicated that the virus was a herpesvirus. Because it was the sixth member of the herpesvirus family, it was renamed Human herpesvirus 6. Two years after…

Cytomegalovirus

Cytomegalovirus (CMV) is a ubiquitous virus that infects most individuals worldwide. In immunocompetent individuals, CMV causes mild to no symptoms but can cause significant disease in immunocompromised patients. Congenital CMV is the most common infection in newborns worldwide and is a leading cause of hearing loss in children. In addition, CMV is an important cause of disease in solid organ and stem cell transplant recipients and…

Varicella-Zoster Virus

Varicella-zoster virus (VZV) is an alphaherpesvirus that is related most closely to herpes simplex viruses 1 and 2. Primary infection with VZV causes varicella, commonly called chickenpox. VZV establishes latent infection in dorsal root and cranial ganglia and can reactivate to cause herpes zoster, often referred to as shingles. The double-stranded DNA genome of the virus encodes >70 proteins, including regulatory and virion structural proteins and…

Herpes Simplex Virus

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) belong to the Alphaherpesvirinae subfamily of herpesviruses. The large DNA viruses have a short reproductive cycle, rapidly produce lytic infection in tissue culture, and remain latent in sensory neural ganglia. After infection of the oral mucosa, usually by HSV-1, the virus becomes latent in the trigeminal ganglia. After genital infection by HSV-2 or HSV-1, the latent…

Introduction to Herpesviridae

The family Herpesviridae contains three subfamilies: Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae. , The eight known human herpesviruses are represented in six genera, which are shown with the typical characteristics of the subfamilies in Table 203.1 . TABLE 203.1 Members of Herpesviridae Family Subfamily Characteristics Genus Member Alphaherpesvirinae Short reproductive cycle Efficient destruction of infected cells with release of viral progeny Rapid spread in culture Latency in sensory…

Poxviridae

Despite the eradication of smallpox as a human pathogen, several poxviruses remain clinically significant, including monkeypox, vaccinia (i.e., virus used for smallpox vaccination), molluscum contagiosum, and several relatively uncommon zoonotic viruses. Concern about smallpox as a bioterrorist weapon also has led to continued interest in poxvirus research. Concurrently, interest in poxviruses (vaccinia virus in particular) as vaccine vectors and potential immunotherapeutic agents has contributed to a…

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Acknowledgements This chapter includes information included by Drs. Gary S. Marshall and Bryan D. Carter in previous editions of the book. It also relies heavily on the collaborative efforts of members of the international writing group for the Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Primer, Drs. Rosemary A. Underhill, Kenneth J. Friedman, Alan Gurwitt, Marvin S. Medow, Malcolm S. Schwartz, Nigel Speight, Julian M. Stewart, Rosamund Vallings, and…

Kawasaki Disease

Kawasaki disease (KD) is the most common cause of acquired heart disease in children in the developed world. The epidemiology and clinical features of the illness point to an infectious etiology, but the cause remains unknown. KD is a unique vasculitis that occurs in previously healthy young children and can result in serious long-term coronary artery disease or death. Approximately 20% of children with KD who…

Ureaplasma urealyticum

Microbiology Members of the family Mycoplasmataceae are small pleomorphic bacteria that characteristically lack a cell wall. Shapes range from filamentous to spherical, with diameters up to 0.8 μm. The genus Ureaplasma is biochemically unique in that all members possess urease and therefore hydrolyze urea to produce adenosine triphosphate. Ammonia, which increases the pH and limits growth in culture, is also produced. Ureaplasma urealyticum was first described…

Other Mycoplasma Species

Many Mollicutes colonize the mucosal surfaces of humans ( Table 197.1 ). Of these, only Mycoplasma genitalium , M. hominis , M. pneumoniae (see Chapter 196 ) , and Ureaplasma urealyticum (see Chapter 198 ) are known to be pathogenic for healthy humans. Other Mycoplasma species have been isolated in pure culture from nonmucosal sites in immunocompromised people, indicating that commensal species can cause disease in…

Mycoplasma pneumoniae

Description of the Pathogen Mycoplasma pneumoniae is a member of the class Mollicutes, which includes bacterial pathogens and commensals found in many animals and plants. These pathogens comprise the smallest self-replicating prokaryotes known to cause infection in humans. M. pneumoniae is approximately 120–150 nm, about the size of myxoviruses, and it passes easily through membrane filters intended to prevent bacterial contamination. Humans are the only known…

Anaerobic Gram-Positive Nonsporulating Bacilli (Including Actinomycosis)

Anaerobic gram-positive, nonsporulating bacilli of clinical significance include Actinomyces , Bifidobacterium , Eubacterium , Lactobacillus , Mobiluncus , and Cutibacterium (formerly Propionibacterium ) . A taxonomic revision has placed all Propionibacterium species of the skin microbiota within a new genus: Cutibacterium . Cutibacterium acnes is the best studied species. Actinomyces and Cutibacterium are the most common clinical pathogens and can be differentiated by biochemical reactions and…

Anaerobic Cocci

The anaerobic cocci are major components of the normal microbiota of the mouth, upper respiratory tract, gastrointestinal tract, vagina, and skin. Gram-positive cocci and gram-negative cocci ( Veillonella spp.) are the anaerobic bacteria most commonly isolated from clinical specimens. Traditional methods of isolating anaerobes is time consuming and can require multiple subcultures and biochemical analyses; the use of inappropriate culture and transport methods further reduces the…

Fusobacterium Species

Fusobacteria are non–spore-forming, nonmotile, pleomorphic, gram-negative ( Fig. 193.1 ), obligate anaerobic bacilli that can cause a wide spectrum of human disease ranging from mild pharyngitis to sepsis, and these organisms are most notorious for causing septic thrombophlebitis of the internal jugular vein, commonly referred to as Lemierre syndrome. Fusobacterium infections in children and adolescents often are associated with abscess formation and intracranial complications. F. nucleatum…

Bacteroides and Prevotella Species and Other Anaerobic Gram-Negative Bacilli

Clinically important anaerobic gram-negative bacilli (AGNB) include B. fragilis group (including Bacteroides and Parabacteroides ), Prevotella , Porphyromonas , and Fusobacterium . Fusobacterium are discussed in Chapter 193 . Infections due to Porphyromonas and Prevotella (previously named Bacteroides species) are not common in children, except for Prevotella melaninogenica and Prevotella intermedia. , Changing taxonomy has caused considerable clinical confusion in recategorization of Bacteroides species. Additionally, many…

Other Clostridium Species

Clostridia are gram-positive, spore-forming bacilli that cause up to 10% of anaerobic infections and occur at diverse clinical sites. Of the more than 200 recognized species of Clostridium , <20 are associated with invasive and toxigenic human diseases. , Clostridial species vary in oxygen tolerance, nutritional needs, motility, and optimal temperature for growth. They can cause distinct clostridial histotoxic syndromes by means of specific clostridial toxins…

Clostridioides difficile

Acknowledgment Substantial material from this chapter in the previous edition has been used. The Pathogen Clostridioides difficile (formerly Clostridium difficile ) is an anaerobic spore-forming, Gram-positive bacillus that was first described as part of a study of the intestinal flora of newborn infants. C. difficile infection (CDI) is a toxin-mediated disease . Once spores reach the colon, they convert to the functional vegetative form in which…

Clostridium botulinum (Botulism)

Botulism is a neuroparalytic disease of humans and other animals caused by the action of a heat-labile neurotoxin produced almost exclusively by Clostridium botulinum. Botulism is categorized by modes of acquisition: (1) infant botulism, which results from intestinal colonization, outgrowth, replication, and toxin elaboration after the ingestion of spores; (2) foodborne botulism, which results from the ingestion of preformed toxin elaborated in food that was naturally…

Clostridium tetani (Tetanus)

Tetanus is caused by a neurotoxin produced by Clostridium tetani . It is common in warmer climates. Globally, 15,102 cases of tetanus were reported in 2018 and an estimated 76,600 died. Although a major cause of morbidity and mortality in developing countries, tetanus is rare in the US, with approximately 23–70 cases reported annually to the Centers for Disease Control and Prevention (CDC). Reported cases are…