function disableSpellCheckOnPeoplePickers() {  
  var inputs = document.getElementsByTagName('input');

  for (var index = 0; index < inputs.length; index++) {
    var input = inputs[index];
    if (input.parentNode 
          && input.parentNode.tagName == 'SPAN' 
          && elem.parentNode.getAttribute("NoMatchesText")) {      
        disableSpellCheckOnPeoplePickersAllChildren(elem.parentNode);
    }
  }
}

function disableSpellCheckOnPeoplePickersAllChildren(elem) {
  if (!elem) return;

  elem.setAttribute('excludeFromSpellCheck', true);
  var children = elem.childNodes;
  for (var i = 0; i < children.length; i++) {
    disableSpellCheckOnPeoplePickersAllChildren(children[i]);
  }
}