Isolation, Enumeration, and Identification of Gram-Positive Cocci from Frozen Crabmeat

Abstract

Bacterial levels in frozen crabmeat samples were determined by plate counts using four staphylococcal isolation media incubated for 24, 48, and 72 h at 26 and 35°C. Staphylococcal counts determined by the spread-plate Food and Drug Administration Baird-Parker protocol incubated at 35°C for 48 h (FDABP48-35) served as the standard for comparison. When FDABP48-35 counts were compared to counts from 29 combinations of media, time of incubation, and incubation temperature, only FDABP and Borrego, Florido, Mrocek, and Romero (BFMR) counts, representing 11 combinations, were statistically comparable to FDABP48-35 counts. Cocci (91.5%) were the dominant bacterial type; gram-positive rods (8.3%) and gram-negative isolates (0.2%) were also detected. Isolates tested by the coagulase reaction were predominantly coagulase negative (CN) (97.7%). Of 100 isolates analyzed by the BIOLOG identification procedure, 62% were classified as Staphylococcus lentus, S. hominis, and S. epidermidis. Three isolates were identified as Staphylococcus aureus. These data indicate that species identification of staphylococci from crabmeat can assist in determining the source of contamination, and that staphylococcal isolates from crabmeat are more likely to be coagulase negative.