Culture-based screening of selected bacterial indicators in three freeze-dried lots of the polychaete Australonuphis sp. collected on a single date in southern Brazil

Polychaetes have been investigated as aquaculture feed ingredients because of their nutritional characteristics, particularly for broodstock diets of commercially important fish and shrimp species. However, the use of polychaetes from Latin America as feed resources for industrial aquaculture remains poorly documented, and microbiological data are an essential requirement for the development of new aquaculture ingredients. Therefore, this study screened three separately freeze-dried lots of Australonuphis sp., collected on the same date in southern Brazil, for selected bacterial indicators using culture-based ISO methods. From each lot, one 25-g test portion was homogenized in buffered peptone water; aliquots of this initial suspension were used for the enumeration of total coliforms, thermotolerant coliforms, presumptive Escherichia coli and coagulase-positive staphylococci, and the remaining homogenate was pre-enriched for the detection of Salmonella spp. No target microorganism was detected above the relevant method-specific reporting or detection limits in the tested portions. In all three lots, total coliforms were below 5 CFU g-1, thermotolerant coliforms and presumptive E. coli were below 3 MPN g-1, coagulase-positive staphylococci were below 50 CFU g-1, and Salmonella spp. was not detected. These findings provide preliminary microbiological baseline data for the tested lots of freeze-dried Australonuphis sp. only. Results should not be interpreted as evidence of animal-feed regulatory compliance, as the applicable MAPA requirements depend on the regulatory classification and intended use of the material. Further studies including raw-material and multi-season sampling, additional safety parameters, storage stability, digestibility and feeding trials, together with a formal feed-specific regulatory assessment, will be necessary to determine its suitability for future aquaculture applications.