83
© Springer International Publishing Switzerland 2016
B. Austin, D.A. Austin, Bacterial Fish Pathogens,
DOI 10.1007/978-3-319-32674-0_3
Chapter 3
Aerobic Gram-Positive Rods and Cocci
Abstract Aerobic heterotrophic Gram-positive rods and cocci have received great
attention from fi sheries microbiologists, largely because of the severity of the diseases caused by pathogenic representatives. The group includes Ren. salmoninarum, Mycobacterium and Nocardia, the causal agents of BKD mycobacteriosis and
nocardiosis, respectively. These organisms have been associated with slowly developing diseases that occur both in the wild and in aquaculture.
Keywords Mycobacteriosis • Nocardiosis • BKD • Bacillary necrosis •
Micrococcosis
Erysipelothrix rhusiopathiae
Characteristics of the Disease
The organism was associated with haemorrhagic septicaemia in Australian eels, and
may have been triggered by high temperatures, i.e. >40 °C. Haemorrhages were
apparent in the gill arches and opercula, and in the pale liver. The intestinal mucosa
was haemorrhagic (Chong et al. 2015 ).
Isolation
Kidney and gill tissue was inoculated onto blood agar, MacConkey agar and TCBS
with incubation at 25 and 37 °C for 48–120 h whereupon pinprick colonies on blood
agar (but not MacConkey agar or TCBS) developed (Chong et al. 2015 ).
© Springer International Publishing Switzerland 2016
B. Austin, D.A. Austin, Bacterial Fish Pathogens,
DOI 10.1007/978-3-319-32674-0_3
Chapter 3
Aerobic Gram-Positive Rods and Cocci
Abstract Aerobic heterotrophic Gram-positive rods and cocci have received great
attention from fi sheries microbiologists, largely because of the severity of the diseases caused by pathogenic representatives. The group includes Ren. salmoninarum, Mycobacterium and Nocardia, the causal agents of BKD mycobacteriosis and
nocardiosis, respectively. These organisms have been associated with slowly developing diseases that occur both in the wild and in aquaculture.
Keywords Mycobacteriosis • Nocardiosis • BKD • Bacillary necrosis •
Micrococcosis
Erysipelothrix rhusiopathiae
Characteristics of the Disease
The organism was associated with haemorrhagic septicaemia in Australian eels, and
may have been triggered by high temperatures, i.e. >40 °C. Haemorrhages were
apparent in the gill arches and opercula, and in the pale liver. The intestinal mucosa
was haemorrhagic (Chong et al. 2015 ).
Isolation
Kidney and gill tissue was inoculated onto blood agar, MacConkey agar and TCBS
with incubation at 25 and 37 °C for 48–120 h whereupon pinprick colonies on blood
agar (but not MacConkey agar or TCBS) developed (Chong et al. 2015 ).