Affiliation:
1. Center
for Food Safety and Applied Nutrition, U.S. Food and Drug
Administration, College Park, Maryland
20740
2. The Lobster
Institute, University of Maine, Orono, Maine
04469
Abstract
ABSTRACT
Studies
were undertaken to characterize and determine the pathogenic mechanisms
involved in a newly described systemic disease in
Homarus
americanus
(American lobster) caused by a
Vibrio
fluvialis
-like microorganism. Nineteen isolates were obtained from
eight of nine lobsters sampled. Biochemically, the isolates resembled
V. fluvialis
, and the isolates grew optimally at 20°C;
none could grow at temperatures above 23°C. The type strain
(1AMA) displayed a thermal reduction time (D value) of 5.77 min at
37°C. All of the isolates required at least 1% NaCl for
growth. Collectively, the data suggest that these isolates may embody a
new biotype. Pulsed-field gel electrophoresis (PFGE) analysis of the
isolates revealed five closely related subgroups. Some isolates
produced a sheep hemagglutinin that was neither an outer membrane
protein nor a metalloprotease. Several isolates possessed
capsules. The isolates were highly susceptible to a variety of
antibiotics tested. However, six isolates were resistant to
erythromycin. Seventeen isolates harbored plasmids. Lobster challenge
studies revealed that the 50% lethal dose of a plasmid-positive
strain was 100-fold lower than that of a plasmid-negative strain,
suggesting that the plasmid may enhance the pathogenicity of these
microorganisms in lobsters. Microorganisms that were recovered from
experimentally infected lobsters exhibited biochemical and PFGE
profiles that were indistinguishable from those of the challenge
strain. Tissue affinity studies demonstrated that the challenge
microorganisms accumulated in heart and midgut tissues as well as in
the hemolymph. Culture supernatants and polymyxin B lysates of the
strains caused elongation of CHO cells in tissue culture, suggesting
the presence of a hitherto unknown enterotoxin. Both plasmid-positive
and plasmid-negative strains caused significant dose-related intestinal
fluid accumulations in suckling mice. Absence of viable organisms in
the intestinal contents of mice suggests that these microorganisms
cause diarrhea in mice by intoxication rather than by an infectious
process. Further, these results support the thermal reduction data at
37°C and suggest that the mechanism(s) that led to fluid
accumulation in mice differs from the disease process observed in
lobsters by requiring neither the persistence of viable microorganisms
nor the presence of plasmids. In summary, results of lobster studies
satisfy Koch's postulates at the organismal and molecular levels;
the findings support the hypothesis that these
V.
fluvialis
-like organisms were responsible for the originally
described systemic disease, which is now called limp lobster
disease.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
36 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献