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Diseases of Aquatic Organisms

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DAO 134:89-97 (2019)  -  DOI: https://doi.org/10.3354/dao03363

Ulcerative dermatitis in barramundi due to coinfection with Streptococcus iniae and Shewanella algae

Ahmad Erfanmanesh1, Babak Beikzadeh1,2, Farzaneh Aziz Mohseni3, Donya Nikaein2,4,*, Tahereh Mohajerfar1

1Academic Center for Education, Culture and Research (ACECR), Tehran Organization, Tehran, Iran
2Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
3Persian Type Culture Collection, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran
4Mycology Research Center, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
*Corresponding author:

ABSTRACT: Streptococcus iniae is a pathogenic bacterium which causes septicaemia, while Shewanella algae is an opportunistic pathogen found in marine environments. In this study, we investigated an uncommon coinfection of these 2 bacterial species which resulted in systemic disease and cutaneous ulcers in a barramundi Lates calcarifer farm in the Persian Gulf, Iran. Culture, molecular and histopathological specimens were taken from different organs. In histopathology, results indicated deep bacterial ulceration of skin and subcutaneous muscles. Haemorrhage and hyperaemia were the most common signs observed in visceral organs. In culture, Gram-positive cocci were grown from visceral organs while Gram-negative bacilli were isolated from ulcers. In molecular examination, Streptococcus iniae and Shewanella algae were identified from visceral and ulcer samples, respectively, by PCR of the 16S rRNA gene. The disk diffusion method was used to determine antimicrobial susceptibility of isolated bacteria, with Shewanella algae being resistant to most routinely used antibiotics. In this study, a mixed infection of 2 bacterial species was found; we conclude that systemic streptococcosis could act as a predisposing factor for Shewanella penetration into skin and subsequent ulcer formation. Coinfections are very common in mammals; however, this subject has received little attention in other species, such as fish, and particularly in aquaculture. This study highlights the potential significance of coinfections in barramundi, the effect on the severity of the disease and the potential for new opportunistic pathogens arising.


KEY WORDS: Asian sea bass · Barramundi · Shewanella algae · Streptococcus iniae · Ulcerative dermatitis · Streptococcosis · Antimicrobial susceptibility


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Cite this article as: Erfanmanesh A, Beikzadeh B, Aziz Mohseni F, Nikaein D, Mohajerfar T (2019) Ulcerative dermatitis in barramundi due to coinfection with Streptococcus iniae and Shewanella algae. Dis Aquat Org 134:89-97. https://doi.org/10.3354/dao03363

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