FEMS Microbiology Letters 112 (1993) 291-300 © 1993 Federation of European Microbiological Societies 0378-1097/93/$06.00 Published by Elsevier 291 FEMSLE 05609 Pathological activities of Yersinia ruckeri, the Enteric Redmouth (ERM) bacterium Jesfis L. Romalde 1 and Alicia E. Toranzo Departmento de Microbiologla y Parasitologfa, Facultad de Biologfa, Universidad de Santiago de Compostela, Santiago de Compostela Spain (Received 25 June 1993; accepted 26 June 1993) Abstract: The adherence and invasive capacities as well as the pathobiological activities exhibited by Yersinia ruckeri were examined. Although adhesive ability was dependent on the cell-line employed, all the strains showed moderate adhesion and invasiveness in the salmon cell-line CHSE-214. With regard to the extracellular products (ECP) all of them were strongly toxic for fish with LD50 ranging from 2 to 9.12/~g protein per g fish. In addition, all the ECP samples showed caseinase, gelatinase, amylase, lipase and phospholipase activities, hydrolysed esculin and displayed hemolytic activities for trout, salmon, sheep and human erythrocytes. Heat treatment (100°C for 10 min) caused the loss of all these biological activities except the hydrolysis of gelatin. On the other hand, SDS-PAGE analysis of the LPS and protein components of the ECP revealed variations among strains depending on the serotype. The lack of lethal effects of the LPS present in the ECP was also demonstrated. Key words: Yersinia ruckeri; Adherence; Invasiveness; Extracellular products; Virulence; Enteric Redmouth disease Introduction The Enteric Redmouth (ERM) disease caused by Yersinia ruckeri is an acute to chronic bacter- aemia infection affecting mainly salmonid fish all over the world [1,2]. The first description in Spain was in 1985 [3] and since this date, the disease Correspondence to: A.E. Toranzo, Departamento de Microbi- ologla y Parasitologla, Facultad de Biologla, Universidad de Santiago de Compostela, 15706 Santiago de Compostela, Spain. x Present address: Baylor College of Medicine, Division of Molecular Virology, One Baylor Plaza, Texas Medical Cen- ter, Houston, TX 77030-3498, USA. has been detected each year, producing signifi- cant losses mainly in rainbow trout [4]. Despite the great number of studies on epi- demiological and serological aspects of Y. ruck- er/, few works focussing on the virulence mecha- nisms of this fish pathogen have been published. We have previously demonstrated the lack of relationship among pathogenicity of Y. ruckeri and classical virulence factors such as hemaggluti- nation, hydrophobicity and other cell-surface characteristics [5]. In this work, the toxicity for fish as well as the biological activities of the extracellular products (ECP) of Y. ruckeri have been evaluated in order to understand their pos- sible role in the development of the disease. In Downloaded from https://academic.oup.com/femsle/article/112/3/291/542285 by guest on 25 June 2022