Molecular intraspecific characterization ofPhotobacterium damselaessp.damselaestrains affecting cultured marine fish

Abstract

Aims: The aim of this study was to analyse the intraspecific variability of Photobacterium damselae ssp. damselae strains isolated from different cultured marine fish species using molecular typing methods. Methods and Results: Twenty P. damselae ssp. damselae strains isolated from marine fish species were used in this study. Phenotypic characterization of the strains was carried out using standard microbiological methods. Genetic characterization was conducted using three PCR‐based methods [random amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus‐PCR (ERIC‐PCR) and repetitive extragenic palindromic‐PCR (REP‐PCR)]. Dice coefficient and the unweighted pair group method with average linkage were used for numerical analyses of banding patterns. At phenotypic level, the strains analysed showed seven different profiles, which could not be related to the host fish species, geographic area or outbreak of disease. Isolates were grouped into nine and eight clusters using the RAPD technique with primers 5 and 4, respectively. In both cases, the main cluster grouped 45% of strains. The techniques ERIC‐PCR and REP‐PCR were more discriminatory, both resulting in 14 different clusters, which grouped 15–20% of the isolates. Conclusions: In this study, the techniques tested are confirmed as good tools for molecular typing, because they allow discrimination between P. damselae ssp. damselae strains isolated within the same outbreak. In addition, ERIC‐PCR and REP‐PCR methods were more adequate for rapid typing of P. damselae ssp. damselae than RAPD, allowing the discrimination at strain level. Significance and Impact of the Study: The results, in agreement with previous studies, confirmed the high intraspecific variability among isolated P. damselae ssp. damselae strains at both phenotypic and genetic levels. This suggests the existence of different clonal lineages that coexist in the same geographic area, within a short period of time (2–3 years). The discrimination at strain level can be useful to study the traceability of infections.

Chromosome-Encoded Hemolysin, Phospholipase, and Collagenase in Plasmidless Isolates of Photobacterium damselae subsp. damselae Contribute to Virulence for Fish

“…The majority of P. damselae subsp. damselae strains isolated from outbreaks in aquaculture farms lack pPHDD1 (6,7,11), a virulence plasmid present in highly pathogenic P. damselae subsp. damselae isolates (9).…”

“…species include, among others, turbot (Scophthalmus maximus) (4), sea bream (Sparus aurata) (5), and sea bass (Dicentrarchus labrax) (6,7). The recent reports on the isolation of this pathogen from newly cultured species led to its consideration as an emerging pathogen in marine aquaculture (8).…”

“…However, the vast majority of the P. damselae subsp. damselae isolates from recent outbreaks in aquaculture farms do not produce Dly and PhlyP toxins and have been isolated mainly from sparid fish and from sea bass (6,7,11). Therefore, there is a need to investigate the genetic basis of virulence in strains that do not produce Dly and PhlyP.…”

Photobacterium damselae subsp. damselae, a bacterium pathogenic for marine animals and humans

“…), as well as of fish species of economical importance in aquaculture, causing wound infections and hemorrhagic septicemia. Cultivated species reported to be affected by this pathogen include turbot ( Psetta maxima ; Fouz et al, 1992), rainbow trout ( Oncorhynchus mykiss ; Pedersen et al, 2009), ovate pompano ( Trachinotus ovatus ; Zhao et al, 2009), eel ( Anguilla reinhardtii ; Ketterer and Eaves, 1992), sea bream ( Sparus aurata ; Vera et al, 1991), sea bass ( Dicentrarchus labrax ), yellowtail ( Seriola quinqueradiata ), redbanded seabream ( Pagrus auriga ), white seabream ( Diplodus sargus ), and meagre ( Argyrosomus regius ; Labella et al, 2006, 2010a, b), among others. The recent first reports on isolation of this pathogen from diseased marine fish of new cultured species, suggest that Photobacterium damselae subsp.…”

Photobacterium damselae subsp. damselae, an Emerging Pathogen Affecting New Cultured Marine Fish Species in Southern Spain

“…damselae strains tested: acetoin production, luminescence, gas from glucose, lysine decarboxylase, growth at 4º and 40ºC, urease, and utilization of sucrose, D-mannose, D-cellobiose and D-gluconate. Labella et al (2009) obtained that P. damselae subsp. damselae strains showed variability for the following tests: acetoin production, ß-galactosidase, lysine decarboxylase, growth at 4º and 40ºC, esculin hydrolysis, acid from mannitol, sorbitol and amygdalin, citrate utilization and assimilation of D-mannose, maltose, malate and N-acetylglucosamine.…”