Introducction. Gram-Positive Bacteria (Anaerobes and ´Lactic Acid´ Bacteria). Aerobic Gram-Positive Rods and Cocci. Aeromonadaceae Representatives (Motile Aeromonads). Aeromonadaceae Representatives (Aeromonas salmonicida). Enterobacteriaceae Representatives. Flavobacteria and Cytophagas. Francisellaceae Representatives. Pseudomonads. Vibrios. Miscellaneous Pathogens. Isolation/Detection. Diagnosis. Control. Conclusions. Index.