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Antibacterial Activity of Cyanobacterial Extracts against Legionella spp. †

Laboratório de Biologia e Ecotoxicologia, Departamento de Saúde Ambiental, Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), Av. Padre Cruz, 1649-016 Lisboa, Portugal
Faculdade de Ciências, Universidade de Lisboa (FCUL), Campo Grande 016, 1749-016 Lisboa, Portugal
Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Av. General Norton de Matos, s/n, 4450-208 Matosinhos, Portugal
Laboratório de Microbiologia, Departamento de Saúde Ambiental, Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), R. de Alexandre Herculano 321, 4000-053 Porto, Portugal
Laboratório Nacional de Referência para Legionella, Departamento de Doenças Infeciosas, Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), Av. Padre Cruz,1649-016 Lisboa, Portugal
Centro de Química Estrutural, Instituto Superior Técnico (IST), Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Escola de Saúde, Instituto Politécnico do Porto Porto, R. Dr. António Bernardino de Almeida 400, 4200-072 Porto, Portugal
Centro de Estudos de Ciência Animal (CECA), Instituto de Ciências, Tecnologias e Agroambiente (ICETA), Universidade do Porto, Praça Gomes Teixeira, 4051-401 Porto, Portugal
Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), Praça Gomes Teixeira, 4051-401 Porto, Portugal
Author to whom correspondence should be addressed.
Presented at the 7th Iberian Congress on Cyanotoxins/3rd Iberoamerican Congress on Cyanotoxins, Ponta Delgada, Portugal, 18–20 June 2022.
Presenting author (oral communication).
Biol. Life Sci. Forum 2022, 14(1), 28;
Published: 22 July 2022


Cyanobacteria are recognized sources of natural compounds with a pharmaceutical interest, namely for their antimicrobial activity. Several studies have shown the inhibitory effect of cyanobacteria against the most common bacterial pathogens. However, the bioactivity against Legionella pneumophila was never reported. L. pneumophila is ubiquitous in water environments and causes respiratory infections through water–air transmission. A rise in Legionella outbreaks might be expected, considering that climate changes will exacerbate water-borne diseases. In this work, we evaluated the antibacterial potential of 25 freshwater cyanobacteria from ESSACC collection, against seven Legionella strains (two reference, two clinical and three environmental). Cyanobacterial biomass was extracted with n-hexane, dicloromethane:methanol (2:1), methanol 70%, and water and extracts were dried and dissolved in DMSO (25%). The disk diffusion method was adapted to Legionella growth using 1 McFarland suspension in BCYE plates. Levofloxacin (10 μg) and DMSO (25%) were used as positive/negative controls, respectively. Methanolic extracts from Dolichospermum flos-aquae (LMECYA 165), Limnothrix redekei (LMECYA 145), Microcystis aeruginosa (LMECYA 127) and Planktothrix agardhii (LMECYA 257) induced inhibition zones ≥10 mm, demonstrating their antibacterial activity against L. pneumophila. These results encourage us to further investigate the potentiality of cyanobacteria as natural sources of antibiotics and/or water disinfectants, to overcome the occurrence of pathogenic Legionella in water environments.

Author Contributions

Conceptualization, C.M. and E.D.; methodology, N.F., I.D., J.A., C.M., C.C., P.G., R.M. and E.D.; investigation, N.F., I.D., C.M., J.A., T.R., R.M. and E.D.; resources, C.C., P.G., J.A. and C.M.; writing—original draft preparation, N.F., C.M., J.A. and E.D.; writing—review and editing, N.F, I.D., C.M., J.A., T.R., C.C., P.G., J.A.L.d.S., R.M. and E.D.; visualization, N.F., C.M., J.A. and T.R.; supervision, C.M., J.A.L.d.S. and E.D. All authors have read and agreed to the published version of the manuscript.


This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.
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MDPI and ACS Style

Ferreira, N.; Menezes, C.; Dias, I.; Azevedo, J.; Rosado, T.; Coelho, C.; Gonçalves, P.; da Silva, J.A.L.; Martins, R.; Dias, E. Antibacterial Activity of Cyanobacterial Extracts against Legionella spp. Biol. Life Sci. Forum 2022, 14, 28.

AMA Style

Ferreira N, Menezes C, Dias I, Azevedo J, Rosado T, Coelho C, Gonçalves P, da Silva JAL, Martins R, Dias E. Antibacterial Activity of Cyanobacterial Extracts against Legionella spp. Biology and Life Sciences Forum. 2022; 14(1):28.

Chicago/Turabian Style

Ferreira, Nicole, Carina Menezes, Iara Dias, Joana Azevedo, Tânia Rosado, Carla Coelho, Paulo Gonçalves, José A. L. da Silva, Rosário Martins, and Elsa Dias. 2022. "Antibacterial Activity of Cyanobacterial Extracts against Legionella spp." Biology and Life Sciences Forum 14, no. 1: 28.

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