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Journal of Medical Microbiology logo Journal of Medical Microbiology

Volume 74, Issue 3

: disease-causing pathogen or opportunistic bystander? Open Access

This article is part of the Clinical Profiles collection.

Graphical Abstract

 Graphical abstract 

is an obligate intracellular bacterium found in free-living amoebae. As with other has a biphasic lifecycle with an infectious elementary body and a replicative reticulate body. Once inside a host, the elementary body differentiates to the reticulate body to undergo replication within the membrane-bound compartment called the inclusion. These infected amoebae can be found in many environments such as in hospitals, household water sources, lakes and farm animals. Although the exact route of transmission from amoebae to humans is unknown, it is believed that humans may breathe in the -infected amoebae. The amoebae can then reside on the respiratory epithelium within the new human host. It is possible that newly released can then directly infect human host cells, such as macrophages, pneumocytes or lung fibroblasts, or propagate within infected amoebae. has been found in humans with multiple respiratory infections such as pneumonia and bronchitis, indicating an association of the presence of this bacterium with severe disease. Transmission may also occur zoonotically through contact with contaminated animals. The understanding of potential complications of pregnancy associated with infection is not understood, but there may be an association with infertility or recurrent miscarriage. Identification and diagnosis can be performed by co-culture of respiratory samples with amoebae or by quantitative PCR using primers specific to . This bacterium is found around the world, but due to the lack of testing in patients, the incidence of infection is largely unknown.

 

 

Abstract

is an obligate intracellular bacterium related to disease-causing bacteria like and and is thus classified within the order. was initially discovered within an strain isolated from water in a humidifier during an investigation of an outbreak of respiratory infections in humans.

The disease-causing potential of this bacterium is not fully understood, but has been associated with bronchiolitis, bronchitis, aspiration pneumonia and community-acquired pneumonia in humans. Additionally, diagnostic testing for infection is not routinely performed, indicating that prevalence is underreported.

This JMM profile aims to gauge what is currently known about the pathogenic potential of and bring awareness to gaps in knowledge.

Amoebae appear to be the main reservoir of and likely enter the nasal passages through contaminated water sources or contact with contaminated animals. The infected amoebae may then descend to the lower respiratory tract where the lytic cycle is triggered, causing human infection.

By implementing serology and molecular testing, as well as conducting additional epidemiological studies, a better understanding of the association of human colonization with disease outcomes can be achieved.

  • Received:
  • Accepted:
  • Published Online:
Keyword(s): Chlamydia-related bacteria , Chlamydiales order , emerging pathogen , lung infection , protists and virulence
Funding
This study was supported by the:
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (Award 197768)
    • Principal Award Recipient: GreubGilbert
© 2025 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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2026-02-19

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