Scrub typhus is an important cause of acute febrile illness in South and East Asia and the Pacific and could be emerging in the Middle East and South America. The causative agent is distinct from, but related to, Rickettsia species.…
Rickettsia species were classically divided into spotted fever and typhus groups based on serologic reactions and the presence or absence of the outer membrane protein A (ompA) gene. Sequencing of at least 45 complete genomes has refined distinctions. However, there…
Chlamydia psittaci, the agent of psittacosis (also known as parrot fever and ornithosis ), is primarily an animal pathogen and rarely causes human disease. In birds, C. psittaci infection is known as avian chlamydiosis . Etiology C. psittaci affects both…
Chlamydia trachomatis is subdivided into 2 biovars: lymphogranuloma venereum (LGV) and trachoma, which is the agent of human oculogenital diseases other than LGV. Although the strains of both biovars have almost complete DNA homology, they differ in growth characteristics and…
Chlamydia pneumoniae is a common cause of lower respiratory tract diseases, including pneumonia in children and bronchitis and pneumonia in adults. Etiology Chlamydiae are obligate intracellular pathogens that have established a unique niche in host cells. Chlamydiae cause a variety…
Etiology Mycoplasma species are small pleomorphic bacteria that typically lack a cell wall and are bound by a cell membrane. Many of the biologic properties of mycoplasmas are in fact due to the absence of a rigid cell wall, including…
Among the 7 Mycoplasma species isolated from the human respiratory tract, Mycoplasma pneumoniae remains the most common species causing respiratory infections in school-age children and young adults. The Organism Mycoplasmas are the smallest self-replicating prokaryotes known to cause disease in…
Lyme disease is the most common vector-borne disease in the United States and is an important public health problem. Etiology Lyme disease is caused by the spirochete Borrelia burgdorferi sensu lato (broad sense). In North America, B. burgdorferi sensu stricto…
Relapsing fever is characterized by recurring fevers and flu-like symptoms such as headaches, myalgia, arthralgia, and rigors. Etiology Relapsing fever is an arthropod (lice or ticks)-transmitted infection caused by spirochetes of the genus Borrelia . Louse-borne (epidemic) relapsing fever is…
Leptospirosis is a common and widespread zoonosis caused by aerobic, motile spirochetes of the genus Leptospira. Etiology Leptospira spp. are thin, helix-shaped members of the phylum Spirochaetes. There are 22 species identified within the genus Leptospira , and these are…