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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…

Chlamydia trachomatis

The Pathogen and Pathogenesis Chlamydiae are obligate, intracellular, nonmotile, gram-negative bacteria with a unique biphasic developmental cycle consisting of extra- and intracellular forms. Chlamydiae have an outer membrane that contains lipopolysaccharide (LPS) and membrane proteins. Peptidoglycan is present in the septum of dividing bacteria. Although chlamydiae contain DNA, RNA, and ribosomes, they obtain high-energy phosphate compounds from the host cell. Chlamydia trachomatis encodes an abundant protein…

Chlamydophila (Chlamydia) pneumoniae

The Pathogen Chlamydiae are obligate intracellular pathogens, which former genus Chlamydia pneumoniae has been reclassified (somewhat controversially ) through genome sequencing and comparative analysis of the ribosomal operon to Chlamydophila pneumoniae, with three biovars—human (TWAR), koala, and equine. Still controversial, Chlamydophila pneumoniae is considered a homotypic synonym for Chlamydia pneumoniae . In this chapter, C. pneumoniae refers to the biovar TWAR, the agent causing infection in…

Capnocytophaga Species

Capnocytophaga is a genus in the family Flavobacteriaceae encompassing a group of slow-growing, capnophilic (carbon dioxide−loving), facultative anaerobic, gram-negative fusiform bacilli. Species are divided into two groups, the “human” group (formerly classified as Centers for Disease Control and Prevention [CDC] biogroup dysgenic fermenter [DF]-1), which colonize the oral cavity of humans and 4 species in the zoonotic group (CDC biogroup DF-2), which are distinguishable from human…

Other Campylobacter Species

The genus Campylobacter includes approximately 26 species and 9 subspecies. Of the Campylobacter species that are associated with human disease, C. jejuni is the prototype for enteric infections, and C. fetus is the prototype for extraintestinal infections. Campylobacter species other than C. jejuni and C. coli are estimated to comprise 3% of Campylobacter isolates isolated from stool. Refinement of microbiologic techniques for isolation of Campylobacter species…

Campylobacter jejuni and Campylobacter coli

Campylobacter spp. are one of the most common causes of culture-proven bacterial gastroenteritis in resource-rich and resource-limited countries. In the US, the annual incidence is 19.5 cases per 100,000 persons and is highest in children aged <5 years. , Although diarrhea is the most common clinical manifestation, Campylobacter infections can be asymptomatic or can result in bacteremia, localized extraintestinal findings, or inflammatory and autoimmune manifestations such…

Bordetella pertussis (Pertussis) and Other Bordetella Species

Pertussis is an acute respiratory tract infection that was well described in the 1500s and endemic in Europe by the 1600s; its current worldwide prevalence is dampened only by continuous use of active immunization. Sydenham first used the term pertussis (intense cough) in 1670. Inexorable spasms of coughing and a protracted course characterize pertussis, as attested to by names given to the disease in many languages:…

Brucella Species (Brucellosis)

Acknowledgements Ed Young was a true gentleman and scholar who was a continuous source of education for all who crossed his path. Brucellosis is a disease of animals that can be transmitted to humans (zoonosis). The genus Brucella belongs to the α-2-subgroup of Protobacteria phylogenetically related to plant and other intracellular animal pathogens (e.g., Bartonella and Rickettsia ). Based on phenotypic analysis, 6 named (nomen) species…

Bartonella Species (Cat-Scratch Disease)

Acknowledgments The authors thank Richard F. Jacobs for the previous contributions to this chapter. The genus Bartonella consists of more than 40 species, of which the best known is B. henselae. The role of B. henselae in most cases of cat-scratch disease has been established through serologic analysis, polymerase chain reaction tests on lymph nodes, and isolation of the organism from lymph nodes. B. quintana, the…

Other Vibrio Species

In addition to organisms that cause cholera (see Chapter 158 ), several other Vibrio species cause vibriosis. These can be divided into invasive species primarily associated with bloodstream and wound infections (e.g., V. vulnificus ) and species that typically cause gastroenteritis (e.g., V. parahaemolyticus ). With the exception of V. parahaemolyticus and V. vulnificus biogroup 3, these organisms rarely cause outbreaks. Description of the Pathogens Vibrios…

Vibrio cholerae (Cholera)

Cholera is an acute diarrheal disease with great potential for epidemic spread. For centuries cholera has caused considerable morbidity and mortality, particularly in the most impoverished areas of the world, where it remains a major public health challenge. Epidemic cholera is caused by two toxin-producing serogroups of the bacterium Vibrio cholerae, O1 and O139. Severe cholera causes rapid loss of fluid and electrolytes, which, without prompt…

Stenotrophomonas maltophilia

Acknowledgments Substantial material from Jane L. Burns’ chapter in the previous edition has been used. Stenotrophomonas maltophilia was originally classified as Pseudomonas. It was transferred to the genus Xanthomonas, however, and subsequently to its own genus, Stenotrophomonas, because of its pattern of biochemical reactions and its role as a human pathogen. S. maltophilia exhibits a negative indophenol oxidase reaction, and many strains require methionine for growth.…

Infections in Returning Travelers

Of the approximately 80 million people who travel from industrialized to developing countries each year, 22% to 64% of travelers report some illness. The approach to the patient requires knowledge of world geography, the epidemiology of disease patterns in 230 or so countries, and the clinical presentation of a wide spectrum of disorders. Most illnesses are mild, most are self-limited, and many are noninfectious. Up to…

Protection of Travelers

Revised March 31, 2020 Pretravel management of an international traveler should be based on risk management principles. Prevention strategies and medical interventions need to be individualized according to both the itinerary and factors that are dependent on the traveler. A structured approach to patient interaction ( Table 318.1 ) is the most efficient way to cover the necessary educational and preventive interventions. Because many of these…

Zoonoses

Zoonoses, derived from the Greek words for animal (zoo) and the suffix modification indicating a state or condition (sis), are infectious diseases of humans that originate in animals. Infectious diseases that originate in humans and move into other animals are commonly described as reverse zoonoses. The majority of emerging viral diseases, up to 70%, represent zoonoses, with such prominent examples as human immunodeficiency virus and acquired…