OLDWICK, N.J.--(BUSINESS WIRE)--A.M. Best has downgraded the issuer credit rating to “a” from “a+” and affirmed the financial strength (FSR) rating of A (Excellent) of AXA Art Insurance Corporation (AXA Art) (New York, NY). The outlook for these ratings has been revised to negative from stable. Concurrently, A.M. Best has affirmed the FSR of A (Excellent) and the ICR of “a+” of AXA Insurance Company (AXA Insurance) (New York, NY), and affirmed the FSR of B++ (Good) and the ICR of “bbb” of Colis