An alternative method to do what you seek is: The MQTT-EventBus integration
Check an example here: [OH2] Control ESP8266 Relay using MQTT Eventbus
Docs entry: http://docs.openhab.org/addons/bindings/mqtt1/readme.html#event-bus-binding-configuration
You can define the topics in any style that you want.
This may be better for your use case (instead of using MQTT Persistence)