Finally, I found myself the answer.
To resolve it, I had to create a subscription, specifying the topic source and the queue destination. To do it, in the IBM WebSphere MQ Explorer :
- Go in the navigator -> IBM WebSphereMQ -> Queue Managers -> Select your queue -> Subscriptions -> New -> Subscription
- Enter the name of your subscription -> click "Next"
- Enter/Select the default attribute "SYSTEM.DEFAULT.SUB"
- Enter the name of the topic (you can select it among the existing in the button on the right)
- Enter the name of the existing queue destination
- Click "Terminate"
That's it ! There were the minimal prerequisites to make it, but you can specify other options.
You can check the properties of subscription on the documentation via this link :
https://www.ibm.com/support/knowledgecenter/SSFKSJ_7.5.0/com.ibm.mq.explorer.doc/e_properties_subs.htm
Note : The instructions' words can be slightly different because I translated the functionnalities of the Websphere MQ software from french to english to answer this post.
(Edit) Explanation :
My NodeJS application has to communicate both ways (publish/receive) with the other app.
As @Shashi said in the comments, MQTT protocol basically works only with Publish/Subscribe model.
However, it is able to communicates with a queue thanks to the "Subscription" functionnality of IBM WebSphere MQ software as I explain earlier.
Indeed, according to what I understand, the "Subscription" functionnality is a kind of "bridge" linking/converting a topic (for the NodeJS) to a destination queue (for the app).
It is the opposite of what an AliasQueue can be for a Topic in IBM Websphere MQ :
"An alias name can also resolve to a topic. If an application currently puts messages onto a queue, it can be made to publish to a topic by making the queue name an alias for the topic. No change to the application code is necessary." (from the documentation)
