The members of the order Chlamydiales have been regrouped into two genera and nine species based on differences in phenotype, 16S rRNA, and 23S rRNA.10 The genus Chlamydia comprises three species: C. trachomatis, C. suis, and C. muridarum. The other genus, Chlamy-dophila, consists of six species: C. pneumoniae, C. psittaci, C. pecorum, C. felis, C. caviae, and C abortus}0'11 Chlamydiae possess a heat-stable, family-specific antigen that is an essential component of the cell membrane lipopoly^ saccharide10; species and type-specific protein antigens-also exist. Members of the order Chlamydiales are obligate intracellular bacteria that were once regarded as viruses. These organisms require the biochemical resources of the eukaryotic host cell environment to fuel their metabolism for growth and replication because they are unable to produce high-energy compounds such as adenosine triphosphate. Chlamydiae have unique developmental life cycle, with an intracellular growth, or replicative form, the reticulate body (RB), and an extracellular, metabolically inert, infective form, the elementary body (EB). Structurally, the chlamydial EB closely resembles a gram-negative bacillus; however; its cell wall lacks a peptidoglycan layer. In addition this replicative cycle assodated with acute chlamydial infections, multiple lines of evidence indicate that Chlamydia can also persist.2 " Following an unresolved infection, it is believed that Chlamydia persist in a viable but noncultivable growth stage referred to as a persistent body (PB), which results in a long-term, stable relationship with the infected host cell, that is, a chronic, infection. Through an unknown stimulus, PBs can then presumably resume differentiation into EB and leac to active infection. The entire life cyde is illustrated in Figure 46-1. C. trachomatis, C. pneumoniae, and CpsittacL are important causes of human infection; C. psittad anM C. pecorum are common pathogens among animals; These three organisms that infect humans differ with respect to their antigens, host cell preference, antibiotic susceptibility, EB morphology, and indusion morphology (Table 46-1).

Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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