The city council of any municipal corporation in the State containing more than five thousand inhabitants and less than ten thousand inhabitants, which has acquired, constructed or caused to be constructed a hospital, may establish a city hospital commission to operate and manage such hospital, may appoint or elect the trustees thereof and may fix by the ordinance establishing the commission the number of trustees thereof to be elected or appointed by the city council and their respective terms of office. In so doing it shall so provide that the original trustees when appointed shall serve originally for varying terms in office so that the term or terms of office of the several members of the commission may not expire at the same time. And upon the expiration of the term or terms of office of the trustees originally appointed the city council may appoint or elect their successors. And in the event of any vacancy by death, resignation or otherwise in the membership of any such commission the vacancy or vacancies may be filled by election or appointed by the city council for the unexpired term.