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Updated: Feb 6, 2026

Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing
Published on: December 23, 2022
Flavobacterium oreochromis From Farmed Tambaqui (Colossoma macropomum): Insights Into Genetic, Phenotypic and
Elcimara Cardoso Pereira1, Mariluce Dos Reis Ferreira1, Suzana Kotzent1
1Nilton Lins University, Manaus, Amazonas, Brazil.
Abstract:
Flavobacterium spp. are the etiological agents of columnaris disease. Although there is evidence that columnaris poses a significant threat to the farming of tambaqui (Colossoma macropomum), there remains a large gap in understanding the genetic and phenotypic diversities of columnaris-causing bacteria (CCB). This study was designed to identify diversity traits of CCB from tambaqui reared in Brazil. From 26 CCB outbreaks previously identified as F. columnare with MALDI-TOF were prospected. A multiplex PCR was conducted to confirm the bacterial species, while REP-PCR was used to determine the differences in genetic patterns (GP), and putative virulence genes were accessed using PCR (norB, trx and gtf). All isolates were identified as F. oreochromis by multiplex PCR. REP-PCR identified 4 genetic variants (GP1, GP2, GP3 and GP4), with GP3 being the most frequent. All the putative virulence genes were detected in all analysed strains. One strain representing each GP was subjected to the description of phenotypic traits (growth patterns, morphology and pathogenicity). The pathogenicity and patterns of virulence were assessed and achieved for all GP, and AMFO14 (GP3) displayed the highest frequency. Based on recent taxonomic advances on Flavobacterium spp. from freshwater fish worldwide, this study provides unprecedented insights regarding CCB retrieved from tambaqui.
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