Maybe try specifying the field Alias?
Whenever I accessed the attributes of results, I used the format of features[0].attributes.<the attribute Field Name>". Note the use of a period instead of array brackets ( [ ] ). Like all things Javascript, the field name WILL be case sensitive.
You could also try quoting the field name in your specification: features[0].attributes['<the attribute field name>']
//Assumes you're using an up-to-date browser! console.log(Object.keys(features[0].attributes));