How do I perform QC on the HTM plates for Haemophilus influenzae susceptibility testing?
A. The CLSI publication M100-S19 (2009) contains revised tables of patient and QC zone sizes for disk diffusion testing of Haemophilus spp. on HTM plates. The QC organisms required by CLSI are H. influenzae, ATCC® 49247 and 49766. It is imperative with this media that the turbidity of the inoculum be carefully adjusted, and that the plates be observed after no later than 18 hours of incubation. A suspension that is too heavy will produce false-resistance results.
