Reclassification of the Listeria-CAMP test strain ATCC 49444 Staphylococcus aureus as Staphylococcus pseudintermedius

ATCC 49444, originally designated as Staphylococcus aureus, has been cited as a component strain in the CAMP test for identification of Listeria monocytogenes. A polyphasic study, in which molecular data were combined with cytochemical properties and physiological characteristics, identified this isolate as Staphylococcus pseudintermedius. The nucleotide sequences of the 16S rRNA and sodA genes from ATCC 49444 were determined and found to be identical to those of other S. pseudintermedius strains. Ribotyping analysis of ATCC 49444 indicated a low (0.2) similarity index with S. aureus and Staphylococcus intermedius strains but a similarity index of more than 0.66 with S. pseudintermedius isolates. A functional comparison of ATCC 49444 with S. aureus ATCC 25923 utilizing the CAMP test demonstrated equivalent hemolytic enhancement with L. monocytogenes isolates. While this study demonstrates that ATCC 49444 is a valid component strain for the CAMP test, it is proposed that ATCC 49444 be reclassified as S. pseudintermedius and that users worldwide be alerted to this reclassification and name change.