All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we ask Allaah to reward you for being keen on letting your beard grow, and for following the example of your Prophet . We have already answered such a question in Fataawa 88254 and 82143.
However, we will mention the following matters:
1- Allaah only legislated for His slaves what is beneficial for them, as He is the All-Knower of what is beneficial for His Slaves; included in this is the matter of letting the beard grow.
2- If you mean that the hair of the beard could be a shelter for some microbes, then this matter is not only applicable to the hair of the beard; rather, it applies to all kinds of hair including the eyebrows. If the matter of microbes is feared, then the hair of the beard could be covered in the same way the hair of the head is covered [while working in the hospital], and so forth.
3- If there is a necessity to continue this job, then it becomes permissible to shave your beard as we clarified in one of the above-referred Fataawa. However, it should be noted that the necessity that renders what is forbidden permissible, is the necessity when a person reaches a situation that causes death or that he will face an unbearable difficulty if he does not commit that prohibition.
Allaah Knows best.