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…
Nonvenereal treponemal infections—yaws, bejel (endemic syphilis), and pinta—are caused by different subspecies of Treponema pallidum and occur in tropical and subtropical areas. The causative agents of nonvenereal treponematoses— T. pallidum pertenue, T. pallidum subspecies endemicum, and Treponema carateum —cannot be…
Syphilis is a chronic systemic sexually or vertically (mother to child) transmitted infection that can be easily treated if detected early but manifests with protean clinical symptoms and significant morbidity if left unchecked. Etiology Syphilis is caused by Treponema pallidum,…
Nontuberculous mycobacteria ( NTM ), also referred to as atypical mycobacteria and mycobacteria other than tuberculosis (MOTT), are all members of the genus Mycobacterium and include species other than Mycobacterium tuberculosis complex and Mycobacterium leprae . The NTM constitute a…