Chilean and German scientists discover new bacterium

A team of Chilean and German scientists discovered a new bacterial species linked to Atlantic salmon (Salmo salar).

Ruben Avendano, a Chilean researcher explained that the study consisted of identifying two bacterial strains isolated from farmed salmon in Chapo Lake, located in the Region of Los Lagos, whose colonies of growth in a solid medium are pigmented, a fact similar to what happens with the fish pathogen Flavobacterium psychrophilum.

This finding is significant because from the aquaculture point of view it alerts that in the aquatic medium associated with salmon farming, ''the genus Chryseobacterium is a natural component, and in some cases, even associated with mixed mortalities as in the case of Chryseobacterium pisicola,'' says Avendano.

"Its similitude with Flavobacterium psychrophilum can lead to a wrong diagnosis since the tests usually applied in the diagnostic laboratories are basic and mainly based upon the usage of commercial enzymatic kits, a situation not recommendable if there are no complementary studies,'' he continued.

"As long as there are no in-depth biochemical and genetic characterisation, identification of these bacteria is difficult and of high cost due to the type of analysis to be performed as DNA-DNA hybridisation, fatty acids analysis and comparisons with all those bacteria that have at least 97% similarity in their 16S ribosomal RNA,'' Avendano added.

In Chile, there are no vaccines registered to prevent cases of flavobacteriosis caused by F. psychrophilum. To diminish mortality, the antibiotics oxytetracycline and florfenicol are usually used, to which the bacteria of the genus Chryseobacterium seem to be resistant.

In addition, there is a silent disadvantage: the damage done to the environment as a result of an erroneous bacterial identification and the corresponding measures to counteract an infectious outbreak.