Looking at the I10 guidelines, B96.81 should be a secondary DX.
I.C.1.b.
Infectious agents as the cause of diseases classified to other chapters
Certain infections are classified in chapters other than Chapter 1 and no organism is identified as part of the infection code. In these instances, it is necessary to use an additional code from Chapter 1 to identify the organism. A code from category B95, Streptococcus, Staphylococcus, and Enterococcus as the cause of diseases classified to other chapters, B96, Other bacterial agents as the cause of diseases classified to other chapters, or B97, Viral agents as the cause of diseases classified to other chapters, is to be used as an additional code to identify the organism. An instructional note will be found at the infection code advising that an additional organism code is required.