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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)…

Other Haemophilus Species and Aggregatibacter Species

Of the Haemophilus species, H. influenzae causes by far the most human disease. Several other members of this genus, however, cause clinical illness. These include H. influenzae biogroup aegyptius , H. ducreyi, H. parainfluenzae, H. pittmaniae, H. sputorum, H. haemolyticus, H. parahaemolyticus, and the ill-defined species H. paraphrohaemolyticus . Three former Haemophilus species known to cause human disease have been reclassified into the genus Aggregatibacter. The…

Haemophilus influenzae

Haemophilus influenzae was first isolated by Pfieffer during the 1889 influenza pandemic. For a time, H. influenzae was believed to be the causative agent of influenza and originally was called the influenza bacillus. However, subsequent studies demonstrated the fallacy of this notion, and the organism ultimately was given the genus name Haemophilus, meaning blood loving and reflecting its growth requirements . The species name was chosen…

Francisella tularensis (Tularemia)

Description of Pathogen and Epidemiology Francisella tularensis, the etiologic agent of tularemia, is a small, fastidious, non−spore-forming, strictly aerobic gram-negative coccobacillus, which is nonmotile and nonpiliated and has a thin capsule composed mostly of lipid. Tularemia is a zoonotic disease; in addition to humans, who are accidental hosts, >100 animal species are affected, particularly ground squirrels, rabbits, hares, voles, prairie dogs, and muskrats. , The bacteria…

Family Anaplasmataceae (Anaplasmosis, Ehrlichiosis, Neorickettsiosis, and Neoehrlichiosis)

Description of the Pathogens The family Anaplasmataceae is classified in the order Rickettiales and currently contains five genera and two candidate genera of obligate intracellular bacteria. Four of the genera contain members that are known to infect humans: Anaplasma , Ehrlichia , Neorickettsia , and Candidatus Neoehrlichia. These zoonotic bacteria are transmitted by invertebrate vectors and can cause potentially life-threatening diseases in humans and animals. Their…

Coxiella burnetii (Q Fever)

The Pathogen Q fever (or “query” fever) is caused by the intracellular bacterium Coxiella burnetii, which belongs to the order Legionellales, family Coxiellaceae. C. burnetii primarily is a zoonotic pathogen. The organism can be present in high concentrations in the placenta and amniotic fluid of parturient animals and can be transmitted to humans through inhalation or direct contact. , C. burnetii is highly infectious to humans,…

Chlamydia (Chlamydophila) psittaci (Psittacosis)

The Pathogen Chlamydia psittaci (also known as Chlamydophila psittaci ) is a gram-negative obligate intracellular zoonotic bacterium that causes both systemic infection and pneumonia, often referred to as psittacosis or ornithosis ( Fig. 168.1 ). Originally named parrot fever because of its association with psittacines (e.g., parrots, parakeets), psittacosis can be transmitted by virtually all domestic and wild birds. , Epidemiology Psittacosis was first described in…