Review Article | Published:

Medically important bacterial–fungal interactions

Nature Reviews Microbiology volume 8, pages 340349 (2010) | Download Citation

Abstract

Whether it is in the setting of disease or in a healthy state, the human body contains a diverse range of microorganisms, including bacteria and fungi. The interactions between these taxonomically diverse microorganisms are highly dynamic and dependent on a multitude of microorganism and host factors. Human disease can develop from an imbalance between commensal bacteria and fungi or from invasion of particular host niches by opportunistic bacterial and fungal pathogens. This Review describes the clinical and molecular characteristics of bacterial–fungal interactions that are relevant to human disease.

Key points

  • This Review focuses on the mechanisms and clinical importance of the bacterial–fungal interactions that occur on or in the human body.

  • Bacteria and fungi can interact in several ways, including physical interactions by direct cell–cell contact, chemical interaction through the secretion of small molecules that are often involved in quorum sensing, environmental modifications such as pH changes, use of metabolic by-products and alterations in host responses.

  • A range of mammalian and non-mammalian models of infection are now available for the study of mixed bacterial–fungal infections.

  • Several Gram-negative pathogens are capable of killing Candida albicans and inhibiting filament formation, including Pseudomonas aeruginosa, Acinetobacter baumannii, Burkholderia cepacia and Salmonella enterica subsp. enterica serovar Typhimurium. This is predominantly mediated through the secretion of small molecules, such as quorum-sensing molecules and other known secretory virulence factors (namely, phospholipase C and phenazines for P. aeruginosa).

  • Oral streptococci have adapted to adhere to C. albicans in the human mouth, and this seems to be mediated through polysaccharide receptors on the bacterial surface. Such co-aggregation is important in the pathogenesis of many oral diseases.

  • C. albicans mounts a defence against these bacterial predators through the secretion of its quorum-sensing molecule farnesol. This molecule can affect bacterial production of virulence factors, viability and susceptibility to antibacterials.

  • Limited study has been dedicated to understanding the host responses to polymicrobial infections. Recent work in mice suggests that immune responses to a bacterial–fungal infection may be directed preferentially towards a bacterial-type response mediated by T helper 1 cells.

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Acknowledgements

A.Y.P. is funded by a Massachusetts General Hospital ECOR Fund for Medical Discovery Award.

Author information

Affiliations

  1. Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.  apeleg@bidmc.harvard.edu

    • Anton Y. Peleg
    •  & Eleftherios Mylonakis
  2. Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.

    • Anton Y. Peleg
  3. Harvard Medical School, Boston, Massachusetts 02115, USA.  emylonakis@partners.org

    • Anton Y. Peleg
    •  & Eleftherios Mylonakis
  4. Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.  Deborah.A.Hogan@Dartmouth.edu

    • Deborah A. Hogan

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The authors declare no competing financial interests.

Glossary

Gastrointestinal mucositis

Inflammation of the mucosal lining of the gastrointestinal tract (which extends from the oral cavity through to the rectum), often leading to increased microbial transit through the gastrointestinal wall.

Commensal organism

A microorganism that resides on or in the host without causing disease.

Candidiasis

Infection with a Candida species.

Biofilm

A complex community of microorganisms that are often attached to a surface and are surrounded by extracellular matrix.

Quorum sensing

Communication between neighbouring organisms through secreted signalling molecules that allows populations to sense organism density and alter gene expression.

Phenazine

A secreted secondary metabolite and virulence factor of P. aeruginosa.

Probiotic

A microorganism that confers a health benefit to the host.

Endotoxin

A toxin that is part of the structure of the bacterium rather than being secreted. In Gram-negative bacteria, it is most commonly lipopolysaccharide in the outer cell membrane.

Peritoneal cavity

The space in the abdomen that is lined by visceral and parietal peritoneum.

Atopic disease

A disease associated with an allergy (that is, mediated by immunoglobulin E), such as asthma, eczema and hay fever.

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https://doi.org/10.1038/nrmicro2313

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