Since Jesus and his disciples were of the faith of the Jews, then obviously they were pure MONOTHEISTS and hence automatically MUSLIMS: believers in the One and Only God.
3: 52When Jesus found unbelief on their part he said: "Who will be my helpers to (the work of) Allah?" Said the Disciples: "We are Allah's helpers we believe in Allah and do thou bear witness that we are Muslims [Muslimoon]
5: 111"And behold! I inspired the Disciples to have faith in Me and Mine Apostle: they said `We have faith and do thou bear witness that we bow to Allah as Muslims' [Muslimoon]."
22:78And strive in His cause as ye ought to strive (with sincerity and under discipline): He has chosen you and has imposed no difficulties on you in religion; it is the cult of your father Abraham. It is He Who has named you Muslims both before and in this (Revelation);that the Apostle may be a witness for you and ye be witnesses for mankind! So establish regular Prayer give regular Charity and hold fast to Allah! He is your Protector the Best to protect and the Best to help!
*** It is the Quran that asserts that Allah named the People of the Book - previous revelations - Muslims because they believe in the One and Only God ***