Research Publications: UM-SG-RS-2003-14


QPX, a pathogen of quahogs (hard clams), employs mucoid secretions to resist host antimicrobial agents.




Anderson, RS; Kraus, BS; McGladdery, S; Smolowitz, R


Journal of Shellfish Research
22 ( 1 ) : 205 - 208


The thraustochytrid protist quahog parasite unknown (QPX) has caused mass mortalities of hard clams (Mercenaria mercenaria) in Atlantic Canada and Massachusetts. It typically secretes copious mucus in vivo and in vitro. M. mercenaria plasma contains naturally-occurring agents that modulate growth of QPX cultures. This activity was shown by exposing washed, mucus-free QPX (wQPX) to filter-sterilized M. mercenaria plasma. Low plasma protein concentrations (10 mug/ml) in the medium tended to stimulate QPX growth; higher concentrations (10-50 mug/ml) produced dose-dependent inhibition. If wQPX were incubated for various times before exposure to an inhibitory concentration of M. mercenaria plasma, a time-dependent protection from the plasma was observed; total protection was seen after similar to24 h preincubation. This effect was probably a result of the re-establishment of the mucoid coats around the wQPX during preincubation. These data suggest that the mucoid secretion of QPX may represent an important virulence factor.

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