Carriage of potentially fish-pathogenic bacteria in Sparus aurata cultured in Mediterranean fish farms.
A bacteriological survey of gilthead sea bream Sparus aurata from different fish farms and culture systems on the Spanish Mediterranean coast was conducted. Three different studies were performed. Study A included hatchery-reared larvae; Study B, periodic examination of randomly sampled growing fish; and Study C, growing fish sampled only during mortality/morbidity events. In Studies B and C, sea cages, earth ponds and indoor tanks were surveyed, and in both cases diseased (showing clinical signs) and non-diseased fish were included. In Study A, a shift from Vibrio spp. (30 d after hatching) to oxidative species (60 d after hatching) was detected, and no mortality events were registered. The percentage of fish yielding bacterial growth were similar in Studies B and C, reaching 57.4 and 61.3%, respectively. A statistically significant relationship between the bacterial carriage and the type of facility was only found in Study B, showing that fish from sea cages had a higher bacterial occurrence than fish from other facilities. A statistically significant relationship between bacterial carriage and signs of disease was found, although the pattern differed in each study. Thus, in Study B only 36.2% of fish yielding abundant bacterial growth were diseased, versus 68.0% in Study C. In total, 25.0% of the fish examined were diseased. Bacterial species composition was similar in asymptomatic and diseased fish, except for a group of V. ichthyoenteri-like isolates that occurred almost exclusively in asymptomatic fish. Dominant bacterial species were V. harveyi and V. splendidus, followed by V. ichthyoenteri-like isolates, Photobacterium damselae ssp. damselae and V. fisheri. Non-fermenters were less frequent but, among them, unidentified halophilic Cytophaga-Flavobacterium isolates and Pseudoalteromonas haloplanktis were the most abundant. An association of individual species with disease was not clear, which suggests the involvement of mixed infections.
Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Departament de Microbiología i Ecología, Facultad de Biologia, Campus de Burjassot, Universitat de València, 46100 Valencia, Spain.
M J
MJ
Pujalte
A
A
Sitjà-Bobadilla
P
P
Alvarez-Pellitero
E
E
Garay
D000818:Animals; D017756:Aquaculture; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D015169:Colony Count, Microbial; D005393:Fish Diseases / Q000453:epidemiology* / Q000382:microbiology; D007814:Larva / Q000382:microbiology; D010776:Photobacterium / Q000302:isolation & purification / Q000472:pathogenicity; D021541:Sea Bream; D013030:Spain / Q000453:epidemiology; D014733:Vibrio / Q000302:isolation & purification / Q000472:pathogenicity; D014735:Vibrio Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D014774:Virulence; D014871:Water Microbiology