Comparative Study of Shimizu and Gibbs' Sets for Phage Typing Staphylococcus aureus Isolated from Poultry

Abstract

Shimizu and Gibbs' phage sets for typing poultry Staphylococcus aureus strains were applied to 295 strains isolated from chickens, a turkey, quails, pigeons and birds of prey in Japan and 5 other countries. Typability with Shimizu's set of 25 phages and with Gibbs' set of 22 phages was compared. Of 295 strains, 230 (78.0%) strains were typable with the former and 238 (80.7%) strains were typable with the latter, respectively. The majority of the poultry strains were highly susceptible at routine test dilution to the phages in the two sets. When the two typing sets were combined, the increase of typability was ca. 10%. Most of strains isolated from chickens in Japan, England, Belgium, Italy, Bulgaria and Argentina can be typed into the phage groups. The two sets appeared useful in typing strains in each of the S. aureus isolated from chickens in different countries. The phages of the two sets were found to be highly active also to the strains isolated from a turkey, quails, pigeons and birds of prey, showing a variety of avian hosts. It was shown from the relationship between Shimizu and Gibbs' phages that groups I and II of Shimizu's phages were closely correlated with group A and B2, respectively, of Gibbs' phages. Lytic spectra of all 47 phages of Shimizu and Gibbs' sets were made by the use of their propagating strains. These phages were divided into 6 distinct groups according to their host ranges. The propagating strain 11 of group IV phage CH11 which constitutes Shimizu's set was shown to be identical with a new species, S. hyicus subsp. hyicus on the basis of a taxonomic analysis. Therefore, we proposed in the present study that the phage CH11 should be deleted from our poultry phage set and regarded as a new phage of our S. hyicus subsp. hyicus phage set which had been established for typing S. hyicus subsp. hyicus strains of swine origin. Accordingly, the phages of our poultry phage set were classified into 3 lytic groups (I, II and III) according to their host ranges.