Parasitic Biofilms: Formation, Implications, and Associated Parasites

Parasitic biofilms represent a structured community of parasites embedded in an extracellular matrix, facilitating their survival, persistence, and resistance to host immune responses and treatments. This review discusses the characteristics of parasitic biofilms, the major parasites involved, their role in pathogenesis, and potential therapeutic interventions. Biofilms are organized microbial communities that adhere to surfaces and produce an extracellular polymeric substance (EPS). While biofilms are commonly associated with bacteria and fungi, emerging evidence suggests that certain parasites can also form biofilms. These parasitic biofilms contribute to chronic infections, immune evasion, and resistance to antiparasitic drugs.

Parasitic Biofilm Formation

Parasitic biofilms comprise parasites, their secreted EPS, and sometimes co-associated bacteria. Biofilm formation enhances parasite survival by providing a protective niche that limits exposure to environmental stressors and host immune attacks. Several key factors influence parasitic biofilm development, including adhesion molecules, quorum sensing, and environmental conditions.

Parasites Capable of Biofilm Formation

Several protozoan and helminthic parasites have been reported to form biofilms:

1. Giardia lamblia: This intestinal protozoan forms biofilm-like aggregates that contribute to chronic infections and increased resistance to metronidazole (Einarsson et al., 2018).
2. Entamoeba histolytica: Forms multicellular aggregates that enhance pathogenicity and resistance to immune clearance (Biron et al., 2013).
3. Leishmania spp.: Promastigotes of Leishmania exhibit biofilm-like structures, particularly in the sand fly vector, aiding in survival and transmission (Sádlová et al., 2012).
4. Trichomonas vaginalis: Forms structured biofilms in the vaginal mucosa, contributing to chronic infections and increased resistance to treatment (Fiori et al., 2013).
5. Toxoplasma gondii: Forms biofilm-like cysts in host tissues, which protect the parasite from immune responses and antiparasitic drugs (Barragan & Sibley, 2002).
6. Trypanosoma cruzi: Involved in Chagas disease, this parasite exhibits biofilm formation, enhancing persistence in host tissues and transmission (Ferreira et al., 2014).
7. Plasmodium spp.: Biofilm-like sequestration of infected red blood cells in cerebral malaria has been reported, contributing to disease severity (Postels & Birbeck, 2013).

Role in Pathogenesis

Parasitic biofilms enhance virulence, persistence, and drug resistance. Forming biofilms shields parasites from immune recognition and clearance, leading to chronic infections. Moreover, biofilms facilitate parasite transmission by providing a stable reservoir for continued infection. Biofilm-associated parasites pose significant challenges for treatment due to increased resistance to conventional antiparasitic drugs. Novel therapeutic strategies include:

• Biofilm Disruptors: Agents targeting EPS components, such as DNase and dispersin B, may help break down biofilm integrity.
• Combination Therapy: Using antiparasitic drugs with biofilm inhibitors (e.g., quorum sensing inhibitors) may enhance treatment efficacy.
• Nanotechnology: Nanoparticles designed to penetrate biofilms could improve drug delivery to parasitic communities.

Parasitic biofilms represent a novel and challenging aspect of parasitology, with significant implications for disease progression and treatment. Understanding the mechanisms of parasitic biofilm formation and resistance may lead to more effective therapeutic interventions.

References

• Barragan, A., & Sibley, L. D. (2002). Migration of Toxoplasma gondii across biological barriers. Trends in Microbiology, 10(9), 405-410.
• Biron, D. G., et al. (2013). Amoebiasis: Insights from genomics and transcriptomics. Infectious Disorders - Drug Targets, 13(3), 171-183.
• Einarsson, E., et al. (2018). Biofilm formation in Giardia lamblia: Implications for chronic infections. PLoS Pathogens, 14(2), e1006792.
• Ferreira, R. C., et al. (2014). Trypanosoma cruzi biofilms: A new perspective on Chagas disease persistence. PLoS Neglected Tropical Diseases, 8(3), e2987.
• Fiori, P. L., et al. (2013). Trichomonas vaginalis and bacterial biofilms: An unholy alliance. Trends in Parasitology, 29(11), 556-563.
• Postels, D. G., & Birbeck, G. L. (2013). Cerebral malaria: Biofilm-like sequestration of infected erythrocytes. Neurology Clinical Practice, 3(4), 389-398.
• Sádlová, J., et al. (2012). Biofilm formation by Leishmania in the sand fly vector. PLoS ONE, 7(10), e49466.

 

This is a simplified figure showing the life-cycle stages that initiate human infection and outbreaks of Cryptosporidium and G. duodenalis. The figure also shows the differences in their impacts on epithelial cells as a result of infection. Adapted from “Cryptosporidium Infection Cycle” by Biorender.com (28 August 2023).