String conversions using backticks are a shorthand notation for calling repr() on a value. For integers, the resulting output of str() and repr() happens to be the same, but it is not the same operation:
>>> example = 'bar'
>>> str(example)
'bar'
>>> repr(example)
"'bar'"
>>> `example`
"'bar'"
The backticks syntax was removed from Python 3; I wouldn't use it, as an explicit str() or repr() call is far clearer in its intent.
Note that you have more options to convert integers to strings; you can use str.format() or old style string formatting operations to interpolate an integer into a larger string:
>>> print 'Hello world! The answer is, as always, {}'.format(42)
Hello world! The answer is, as always, 42
which is much more powerful than using string concatenation.