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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…

Anaerobic Bacteria: Clinical Concepts and the Microbiome in Health and Disease

Classification Anaerobic bacteria predominate on normal skin and among the bacterial flora of mucous membranes. , Infections caused by anaerobic bacteria are common, arise from the sites where they are normal flora (endogenous), and can be serious or life-threatening. Anaerobic bacteria are fastidious, difficult to isolate, and often overlooked. Their recovery requires proper methods of collection, transportation, and cultivation. Their ubiquity on mucocutaneous surfaces often interferes…

Other Borrelia Species and Spirillum minus

Acknowledgments Substantial contributions of Eugene D. Shapiro to this chapter in previous editions are recognized with gratitude. Borrelia Species (Relapsing Fever) Borellia species are generally divided in two major groups: B. burgdorferi sensu lato, which includes the causative agents of Lyme borreliosis, and the complex of pathogens associated with relapsing fever. Microbiology Members of the genus Borrelia are microaerophilic spirochetal bacteria characterized morphologically by coarse and…

Borrelia burgdorferi (Lyme Disease)

Pathogenesis and Immunity Lyme disease is caused by the spirochete Borrelia burgdorferi, a cylindrical, fastidious, microaerophilic bacterium that replicates very slowly and requires special medium for in vitro growth. Its cell membrane is covered by flagella and a loosely associated outer membrane. The 3 major outer surface proteins, OspA, OspB, and OspC (which are highly charged basic proteins with molecular weights of ∼31, 34, and 23 kd,…

Leptospira Species (Leptospirosis)

Acknowledgments Substantial contributions of Eugene D. Shapiro to this chapter in previous editions are recognized with gratitude. Pathogens and Pathogenesis The Leptospira genus consists of a group of motile, finely coiled, catalase-producing spirochetal bacteria that are obligate aerobes . The Leptospira genus is classified into at least 20 species and genomospecies. L. biflexa is a free-living saprophytic organism that is found in water and soil and…

Other Treponema Species

Yaws Yaws ( Treponema pallidum subsp. Pertenue infection) is an infectious disease of childhood. It is seen in warm, humid tropical regions in rural, often inaccessible areas and is associated with poverty, overcrowding, poor hygiene, and lack of access to health services. “Yaws begins where the road ends.” Endemic areas include Africa, Southeast Asia, the Western Pacific, and South and Central America. Yaws is also known…

Treponema pallidum (Syphilis)

Four diseases are associated with pathogenic treponemes: (1) venereal syphilis, caused by Treponema pallidum subsp. pallidum ; (2) yaws, caused by T. pallidum subsp. pertenue ; (3) endemic syphilis, or bejel, caused by T. pallidum subsp. endemicum ; and (4) pinta, caused by T. carateum . These diseases are thought to have diverged from a single disease 10,000 to 100,000 years ago under the influence of…

Other Gram-Negative Coccobacilli

A large number of gram-negative coccobacilli have been reported to cause infections in humans. This chapter describes three coccobacilli not discussed in other chapters. These organisms are important in specific epidemiologic and clinical settings and present special problems of diagnosis and therapy. Aggregati Bacter Species Aggregatibacter (formerly Actinobacillus ) actinomycetemcomitans , a small, fastidious gram-negative coccobacillus, is a cause of endocarditis, of periodontal infection, and of…

Streptobacillus moniliformis (Rat-Bite Fever)

Streptobacillus moniliformis, S. hongkongensis, and S. notomytis of the genus Streptobacillus cause infection in humans. They are fastidious, nonmotile, gram-negative, pleomorphic, and often filamentous, beaded, facultative anaerobic bacilli. S. moniliformis can exist in two phases: the bacillary phase and the cell wall-deficient L-phase. , In addition to being the main etiologic agent of a systemic illness called rat-bite fever , S. moniliformis causes Haverhill fever. Sodoku…

Other Rickettsia Species

Rickettsia Prowazekii (Classic Louse-Borne Epidemic Typhus: Brill-Zinsser Disease Or Recrudescent Typhus; Sylvatic Or Flying Squirrel-Associated Typhus) Description of Pathogen Rickettsia prowazekii is a small, gram-negative, obligately intracellular, rod-shaped bacterium. R. prowazekii possesses a regularly arrayed surface autotransporter protein (OmpB) layer external to the cell envelope that has a peptidoglycan sacculus located between the inner cytoplasmic and lipopolysaccharide-containing outer membrane. It does not possess flagella. Both humoral…

Rickettsia rickettsii (Rocky Mountain Spotted Fever)

Description of The Pathogen Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever (RMSF), is a small, obligately intracellular, gram-negative, rod-shaped organism that is among the most pathogenic of all known bacteria. Although R. rickettsii can infect several different cell types, its primary targets in mammalian hosts are the endothelial cells lining capillaries, arterioles, and venules of all major tissues and organ systems ( Fig.…

Legionella Species

Investigation of an outbreak of pneumonia among attendees at an American Legion Convention in Philadelphia in 1976 revealed a previously unrecognized causative pathogen, Legionella pneumophila. , Infection with Legionella spp. occurs in sporadic and outbreak forms and is one etiology of both community-acquired and healthcare-associated pneumonia; it is known as legionnaires’ disease or legionellosis. Legionella spp. also is associated with Pontiac fever, a rare illness that…

Kingella Species

The genus Kingella belongs to the Neisseriaceae family in the β-subclass of the Proteobacteria, and the genus currently comprises five recognized species. Kingella potus has been isolated from an infected animal bite in an adult, the recently described K. negevensis is carried in the oropharynx of children and is associated with bacterial vaginosis, but its role as a human pathogen is still uncertain and three other…

Other Gastric and Enterohepatic Helicobacter Species

Since the discovery of Helicobacter pylori and the demonstration of its causal relationship with human gastroduodenal disease, investigators have identified numerous non− Helicobacter pylori Helicobacter (NHPH) species. These other Helicobacter spp. are frequently found in domestic and wild animals and have been recovered from the stomach, intestine, and hepatobiliary systems of humans. Although the complete spectrum of human disease syndromes associated with NHPH remains to be…

Helicobacter pylori

Helicobacter pylori infection is ubiquitous among humans. , Despite declining prevalence in developed countries, H. pylori continues to be one of the most common human infections worldwide, affecting up to 90% of the population in developing nations. Transmission primarily occurs from person to person during early childhood. H. pylori infection causes gastritis, duodenal and gastric ulcers, as well as gastric adenocarcinoma and mucosal-associated lymphoid type (MALT)…