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Comparison of in vitro-cultured and wild-type Perkinsus marinus. I. Pathogen virulence
Susan E Ford1, Marnita M Chintala, David Bushek
1Haskin Shellfish Research Laboratory, Institute of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, New Jersey 08349, USA. susan@hsrl.rutgers.edu
Abstract:
Perkinsus marinus is a highly contagious pathogen of the eastern oyster Crassostrea virginica. Until recently, transmission studies have employed wild-type parasites isolated directly from infected oysters. Newly developed methods to propagate P. marinus in vitro have led to using cultured parasites for infection studies, but results suggest that cultured parasites are less virulent than wild-type parasites In this paper, we report results of experiments designed to quantify differences between wild-type and cultured P. marinus virulence and to test the following hypotheses: (1) in vitro-cultured parasites are less virulent than wild-type parasites; (2) virulence decreases gradually during in vitro culture; (3) virulence of in vitro cultures can be restored by in vivo passage; (4) virulence changes with culture phase. Our results demonstrate that parasites freshly isolated from infected hosts are much more virulent than those propagated in culture, indicating a potential deficiency in the culture medium used. Virulence was lost immediately in culture and, for that reason, the practice of repassing cultured cells through the host to restore virulence does not work for P. marinus. Virulence was also associated with culture phase: log-phase parasites were significantly more virulent than those obtained from lag- or stationary-phase cultures.
Insights
Newly cultured Perkinsus marinus (P. marinus) parasites show reduced virulence compared to wild-type strains. Virulence loss is immediate in culture and not restorable by host passage, varying with parasite growth phase.
Area of Science:
- Marine biology
- Pathogen research
- Aquaculture science
Background:
- Perkinsus marinus is a contagious pathogen affecting eastern oysters (Crassostrea virginica).
- In vitro culture methods for P. marinus have been developed, but cultured parasites appear less virulent than wild-type strains.
- Understanding virulence differences is crucial for effective disease management in oyster populations.
Purpose of the Study:
- To quantify virulence differences between wild-type and in vitro-cultured Perkinsus marinus.
- To investigate the impact of in vitro culture duration and phase on parasite virulence.
- To determine if in vivo passage can restore virulence to cultured P. marinus.
Main Methods:
- Comparison of virulence between wild-type and cultured P. marinus isolates.
- Assessment of virulence changes during extended in vitro culture.
- Testing the efficacy of in vivo passage for virulence restoration.
- Correlation of virulence with different culture phases (log, lag, stationary).
Main Results:
- Wild-type P. marinus isolates are significantly more virulent than cultured parasites.
- Virulence is lost immediately upon initiation of in vitro culture.
- In vivo passage does not restore virulence in cultured P. marinus.
- Log-phase cultured parasites exhibit higher virulence than those in lag or stationary phases.
Conclusions:
- Current in vitro culture methods may lead to a deficiency affecting P. marinus virulence.
- The practice of repassing cultured P. marinus through hosts is ineffective for restoring virulence.
- Parasite virulence is significantly influenced by its growth phase during in vitro culture.