Catholics use a quote from Ignatius in 107 AD to try to show a reference to the Catholic church in early christian writings. It can actually disprove the catholic church. Here is the quote.
"Wherever Christ is there is the catholic church"
The word catholic here is the Greek katholicos. Many say it means universal but in the New Testament it can be translated whole, all, entire, every, etc. It just means all of a set. It isn't a name. See Acts 9:31 where it is all of a small region of geography. It is never used with the church in the New Testament. In catholic translation they translated by simply transliterating vs translating. What if they translated it as the New Testament does vs transliterating? It woudl likely say "there is the whole church" or there is the "entire church". It wouldn't be a reference to the modern catholic church at all. It would simply be a normal word if used without bias.
Since it was written before any ecuminical councils and before the papacy is recognizeable historically, it only requires that you be with Christ and Christ be with your congregation of Christians, it doesn't require us to accept catholic theology or practice. It is actually accepting no denomination except Christ. If Christ is with you then you are the church. Of course they can argue to have Christ you must be catholic. That is a debate for another page, but I would argue if becoming catholic you would be leaving Christ for human commands and gnostic interpretation.
So the quote is a trick through transliteration vs translation. The word catholic was used of the church councils where constantine called the entire christian community to discussions and votes. This sounds fait but realize many called were gnostics out of different areas of Africa and Europe. In other words many called to vote weren't true christians and carried a lot of error. The error was mixed into the doctrinal decisions. The votes were not representative of true christianity universally, but all carrying the name Christian whether true or not.