Trouble shooting for Modified Hodge test?

[vivegaviji]

Dear all,

We had faced a problem in MHT test? We could not able to get good results in MHT by using known carbapenemase resistant strains? we checked to all possible ways like inoculum concentration, MHA, ATCC strains.. We could not sort out the issue... Please share your ideas and views about trouble shooting procedrue for MHT.

Many thanks in advance for your views...

 

Dr. R. Vijaya KUmar

[Micro.Pete]

Hi,

Please specify what is exactly your problem with the MHT. It can be due to the ATCC E. Coli strain or with the Klebsiella controls or even because of bad equipment (such as agar plates, saline, etc..)

Make sure that you do the next steps:

1. For obtaining a good ATCC E. Coli growth you have to reach 0.5-0.63 McFarland dilution. For that you have to use extra pure saline (not the one you may use for the VITEK machine).

 

2. Make sure that your Mueller-Hinton agar plates are not expired.

 

3. Make sure you use fresh Klebsiella positive and negative controls (They are typically good for about 2-3 weeks after you prepare them on Mcconkey agar plates).

 

4.what kind of bacteria do you often check with your MHT? Note that Enterobacter spp. tend to give false positive results which have to be verified using PCR.