DISTRIBUTION OF INDICATOR BACTERIA AND BACTERIOPHAGES IN SHELLFISH AND SHELLFISH-GROWING WATERS

Shellfish (mussels and clams) and shellfish-growing waters were examin ed for indicator bacteria according to the EC regulations, Salmonella spp., coliphages and anti-Salmonella phages. Samples mere collected bo th from natural-growing areas along the coast and from authorized shel lfish-harvesting beds. The coastal area was affected by organic pollut ion and extensive faecal contamination and, according to the legal req uirements, was unsuitable for shellfish farming. The shellfish collect ed along the coast also showed faecal contamination at levels which di d not conform to legal standards. No significant differences were obse rved between the frequency of isolation of somatic coliphages and indi cator bacteria from sea water. In contrast, both the authorized and mi ld coastal shellfish were contaminated by coliphages at a significantl y higher level than the corresponding bacterial indicators for faecal contamination (chi(2) test, P < 0.01). Coliphage concentrations were s ignificantly correlated with faecal indicators in marine waters (P < 0 .001)and sediments (P < 0.05), but no correlation was found in shellfi sh, thus showing their low specificity as indicators of faecal polluti on of human origin in shellfish of economic importance.