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Fish Shellfish Immunol. 2018 Sep;80:573-581. doi: 10.1016/j.fsi.2018.06.049. Epub 2018 Jun 28.

Outcome of co-infection with opportunistic and multidrug resistant Aeromonas hydrophila and A. veronii in zebrafish: Identification, characterization, pathogenicity and immune responses.

Author information

1
College of Veterinary Medicine, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea.
2
Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province, 63243, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province, 63243, Republic of Korea.
3
Veterinary Medical Center and College of Veterinary Medicine, Chungbuk National University, Cheongju, 28644, Republic of Korea.
4
College of Veterinary Medicine, Chungnam National University, Yuseong-gu, Daejeon, 34134, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province, 63243, Republic of Korea. Electronic address: mahanama@cnu.ac.kr.

Abstract

Fish can be potentially co-infected by two or more bacterial strains, which can make synergistic influence on the virulence of infection. In this study, two opportunistic and multidrug resistant Aeromonas strains were isolated from wounds of morbid zebrafish with typical deep skin lesions similar to Motile Aeromonas Septicemia. Isolates were genetically identified as A. hydrophila and A. veronii by 16 S rRNA sequencing and phylogenetic analysis. Both isolates were positive for virulent genes (aerA, lip, ser, exu gcaT) and selected phenotypic tests (DNase, protease, gelatinase, lipase, biofilm production and β-haemolysis). A. hydrophila and A. veronii had strong antibiotic resistance against ampicillin, tetracycline, nalidixic acid, kanamycin, erythromycin, clindamycin and trimethoprim-sulfamethoxazole. Histopathological studies revealed that co-infection causes severe necrosis and hypertrophy in the muscles, kidney and liver of zebrafish. Naturally co-infected zebrafish showed highly induced tnf-α, il-1β, il-6, il-12, ifn, ifn-γ, cxcl18 b and ccl34a.4 at transcription level compared to healthy fish, suggesting virulence factors may activate immune and inflammatory responses of zebrafish. Experimentally infected zebrafish showed significantly higher mortality under co-infection with A. hydrohila and A. veronii (87%), followed by individual challenge of A. hydrophila (72%) or A. veronii (67%) suggesting that virulence of A. hydrophila have greater pathogenicity than A. veronii during co-infection.

KEYWORDS:

Aeromonas hydrophila; Aeromonas veronii; Co-infection; Immune responses; Multidrug resistant bacteria; Zebrafish

PMID:
29964197
DOI:
10.1016/j.fsi.2018.06.049
[Indexed for MEDLINE]

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