A code for reporting and comparing results in phage typing.

This code, like the others proposed, involves the definition of a characteristic reaction for each system. Each reaction must be positive or negative. As regards the interpretation of results, it is worth noting that if the bacteriophage typing system uses not less than 5 phages, there is no problem for interpreting the results of small series of 10 to 20 strains, whatever the code used. But should the system use more than 5 phages, the advantage offered by the octal code becomes obvious because, without computer, the manual coding for comparing the results of various series is always possible. Beyond 6 phages, the binary pattern reporting, unintelligible without correction, is possible with an octal number not exceeding 7 digits for a pattern corresponding to a 21-phage set. When very large series of strains are considered, the coding can be completely done and printed out by any computer through a very simple program. This proposed code is not only rational but also a useful method even if the number of phages used is larger than 20 or 30, but after a computer becomes necessary however the coding system used.