how can I remove a sewer gas like smell from a residential bathroom?

Where is the smell strongest? That would be a good place to start looking. If the bath has a side panel, remove it and see what lurks in the space behind it. If the waste pipe from the toilet is boxed in then see if you can at least get some of the enclosure off to determine if the source of the smell is in there.

Another possible source is the overflow pipe for both the sink and the bath. A good dose of strong bleach can work wonders in clearing smells from these. Avoid the use of caustic soda unles you are certain that all the pipework is plastic or lead, as this chemical is very corrosive to copper and iron.

Some bleach down the bath and sink waste pipes can help too; the sewage daprtment's definition of "clean" and that of residents may be rather different.

check there's water closing every sifon the bathroom
and besure the smell does not come from the OUTside

George:
Here are a list of things you can try some of which are mentioned above.

https://dengarden.com/home-improvement/Phew-Whats-that-awful-smell-Could-it-be-sewer-gas-invading-your-home

Hello Everyone,

         I know this is offbeat from my original question, but, I am wondering why I do not see options for Accepted and Assisted Answers.  I am having this same issue with another currently open question.  

        Thank you

         George

try the Contact Us in the menu at the bottom right of the screen

you should see

Accept multiple solutions - The answer to your question was summarized in more than one comment. To select this option, click the "Accept Multiple Solutions" button on the comment that best summarized the solution, then select the supporting comments you feel contributed to the solution.

the last couple of years they made closing Questions so difficult many people  can't do it anymore
it's really become a guessing game, like the windows menus - see the "option" represented by 3 dots

I no longer see best solution and assisted on mine.
Has the point system been stopped?
On my question all I see are "was this helpful (or also in the drop down box is "unhelpful)" and I think I can choose the best one.
George you should see the 5 steps on the left. If you click on 4 (I have my answer)  is seen and then "best" is an option for all comments.

I do not see any reference to "unhelpful" though it was a choice as step 3.

Hello and Good Morning Everyone,

          Thank you for your shared insights and tips.  I am happy to say the issue is resolved.  It turns our the commode base was a little loose and a new wax seal had to be applied.  In order to make sure a proper identification and correction of this issue was done, I went ahead and called in a plumber.  It is much better now.

            On a side note, I truly hope I have been fair in the closure of this post.  There have been some unexpected modifications such as the elimination of the options of accepting assisted questions and allocating points for each response.  That said, I truly apologize if I have been unfair in any way with respect to the appreciation and acknowledgment of the feedback given to this post.  Hopefully, the moderators and administrators in charge of the design and operation of the EE pages will bring these options of accepting assisted questions and allocating points back to the forefront.   With the new setup, it seems that the accepting of answers is based on either an all or nothing principle.   All responses which enrich the answers to concerns should receive acknowledgment which was previously handled through the allocation of points.  Of course, this is just one person's opinion here.  From a moral and ethical standpoint, returning the point allocation system in addition to having the option of selecting assisted answers are the only things though that makes sense to me.  

                 Thanks in advance everyone for hearing me out on this one.

                  George