Assessment of the Antimicrobial Activity of Algae Extracts on Bacteria Responsible of External Otitis

Abstract

External otitis is a diffuse inflammation around the external auditory canal and auricle, which is often occurred by microbial infection. This disease is generally treated using antibiotics, but the frequent occurrence of antibiotic resistance requires the development of new antibiotic agents. In this context, unexplored bioactive natural candidates could be a chance for the production of targeted drugs provided with antimicrobial activity. In this paper, microbial pathogens were isolated from patients with external otitis using ear swabs for over one year, and the antimicrobial activity of the two methanol extracts from selected marine (Dunaliella salina) and freshwater (Pseudokirchneriella subcapitata) microalgae was tested on the isolated pathogens. Totally, 114 bacterial and 11 fungal strains were isolated, of which Staphylococcus spp. (28.8%) and Pseudomonas aeruginosa (P. aeruginosa) (24.8%) were the major pathogens. Only three Staphylococcus aureus (S. aureus) strains and 11 coagulase-negative Staphylococci showed resistance to methicillin. The two algal extracts showed interesting antimicrobial properties, which mostly inhibited the growth of isolated S. aureus, P. aeruginosa, Escherichia coli, and Klebsiella spp. with MICs range of 1.4 × 109 to 2.2 × 1010 cells/mL. These results suggest that the two algae have potential as resources for the development of antimicrobial agents.

First identification of marine diatoms with anti-tuberculosis activity

“…Pane et al . 22 also analyzed the bioactivity of Dunaliella extracts: they tested the ability of D . salina to inhibit the growth of 114 bacterial and 11 fungal strains isolated from patients with external otitis and found interesting activities especially against S .…”

The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products

“…The extract of D. salina significantly inhibits the growth of Klebsiella pneumoniae . Substances synthesized by Dunaliella primolecta also showed antibacterial activity against S. aureus and against other bacterial strains [ 260 ].…”

Antimicrobial Compounds from Eukaryotic Microalgae against Human Pathogens and Diseases in Aquaculture

“…Large screening programs have thus been conducted to assess the potential antibacterial activity of various microalgal extracts against pathogenic and foodborne bacteria. Numerous microalgal species from distinct taxonomical groups originating from various areas [ 50 , 51 , 52 ], mainly from marine environment [ 53 , 54 , 55 , 56 , 57 , 58 ], but also from freshwater environment [ 59 , 60 ], or even from the soil [ 61 ] were shown to have potent antibacterial activity against both (G+) and (G−) bacteria ( Table 1 ). As screening studies can sometimes include hundreds of different microalgae [ 51 , 55 , 59 ], Table 1 only presents the microalgae with the highest antibacterial activity or the wider spectrum of activity from these screenings.…”