title: Natural coinfection by Streptococcus agalactiae and Francisella noatunensis subsp. orientalis in farmed Nile tilapia (Oreochromis niloticus L.).
abstract: Streptococcus agalactiae and Francisella noatunensis subsp. orientalis (Fno) are important pathogens for farm-raised tilapia worldwide. There are no reports of coinfection caused by S. agalactiae and Fno in fish. This study aimed to determine the aetiology of atypical mortalities in a cage farm of Nile tilapia and to characterize the genetic diversity of the isolates. Fifty-two fish were sampled and subjected to parasitological and bacteriological examination. The S. agalactiae and Fno isolates were genotyped using MLST and REP-PCR, respectively. Whole-genome sequencing was performed to confirm the MLST results. Seven fish were shown coinfected by S. agalactiae and Fno. Chronic hypoxia and a reduction in the water temperature were determined as risk factors for coinfection. Fno isolates were shown clonally related in REP-PCR. The MLST analysis revealed that the S. agalactiae isolates from seven coinfected fish were negative for the glcK gene; however, these were determined to be members of clonal complex CC-552. This is the first description of coinfection by S. agalactiae and Fno in farm-raised Nile tilapia. The coinfection was predisposed by chronic hypoxia and was caused by the main genotypes of S. agalactiae and Fno reported in Brazil. Finally, a new S. agalactiae genotype with glcK gene partially deleted was described.
authors.affiliation: AQUAVET, Laboratory of Aquatic Animal Diseases, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: G B N
authors.initials: GB
authors.lastname: Assis
authors.affiliation: AQUAVET, Laboratory of Aquatic Animal Diseases, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: G C
authors.identifier: http://orcid.org/0000-0002-2735-2562
authors.initials: GC
authors.lastname: Tavares
authors.affiliation: AQUACEN - National Reference Laboratory of Aquatic Animal Diseases, Ministry of Fisheries and Aquaculture, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: F L
authors.initials: FL
authors.lastname: Pereira
authors.affiliation: AQUAVET, Laboratory of Aquatic Animal Diseases, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.|AQUACEN - National Reference Laboratory of Aquatic Animal Diseases, Ministry of Fisheries and Aquaculture, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: H C P
authors.initials: HC
authors.lastname: Figueiredo
authors.affiliation: AQUAVET, Laboratory of Aquatic Animal Diseases, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.|AQUACEN - National Reference Laboratory of Aquatic Animal Diseases, Ministry of Fisheries and Aquaculture, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: C A G
authors.initials: CA
authors.lastname: Leal
mesh_terms: D000818:Animals; D017756:Aquaculture; D023681:Cichlids; D060085:Coinfection / Q000382:microbiology / Q000401:mortality / Q000662:veterinary; D005393:Fish Diseases / Q000382:microbiology / Q000401:mortality*; D005603:Francisella / Q000235:genetics / Q000502:physiology*; D014644:Genetic Variation; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000401:mortality / Q000662:veterinary*; D020071:Interspersed Repetitive Sequences; D055029:Inverted Repeat Sequences; D058885:Multilocus Sequence Typing / Q000662:veterinary; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013290:Streptococcal Infections / Q000382:microbiology / Q000401:mortality / Q000662:veterinary*; D013292:Streptococcus agalactiae / Q000235:genetics / Q000502:physiology*
keywords: 
  MLST
  ; 
  glcK
  ; REP-PCR; coinfection; francisellosis; streptococcosis