Pathogenicity of four channel catfish Listeria monocytogenes isolates (CCF1, CCF4, HCC7, and HCC23) was examined in a comparative manner with virulent type strains L. monocytogenes ATCC 19115 and EGD and avirulent type strain ATCC 15313 in BDF and A/J mice. Isolates HCC7
and CCF1 (both serovar 1) caused similar percent mortalities and 50% lethal concentration values when compared with virulent type strains and were therefore considered pathogenic. The presence of the virulence factors listeriolysin (LLO), phosphotidylcholine-phospholipase (PC-PLC), and phosphotidylinositol-phospholipase
(PI-PLC) was determined using specific activity tests. The virulent catfish isolates were positive for production of LLO, PCPLC, and PI-PLC. However, catfish isolate HCC23 was not virulent in mice despite being hemolytic, suggesting that not every hemolytic L. monocytogenes strain is
virulent. With the exception of HCC7, all virulent strains displayed enhanced LLO production in a special stress medium, whereas almost undetectable LLO activity was present when catfish isolates and virulent type strain L. monocytogenes were grown in a rich medium such as brain heart
infusion. Avirulent strains were found to lack or have decreased expression of LLO, PC-PLC, or PI-PLC.
Document Type: Research Article
Veteriner Kontrol ve Arastirma Enstitusu, Pendik, Istanbul, Turkey 2:
Veterinary Medical Research Program, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762, USA
Publication date: May 1, 2000
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