So far many carbapenem antibiotics have been discovered, such as thienamycins, olivanic acids, epithienamycins, PS series, OA-6129 series, C-19393 series, asparenomycins, carpetimycins, pluracidomycins, SF-2103 series and SQ27,860. Most carbapenem antibiotics were produced by Streptomyces. Only SQ 27,860 was produced by Erwinia and Serratia. No other microorganism in any other genus has been reported to produce carbapenem antibiotics. Our screening program for novel carbapenem antibiotics from so-called 'rare actinomycetes' led to the discovery of a new strain named Kitasatosporia papulosa AB-110, which produces a novel carbapenem antibiotic named AB-110-D together with epithienamycins A, B, E and F. The structure of AB-110-D was elucidated as the Z isomer of epithienamycin E in the side chain. No carbapenem antibiotic having a Z side chain has been isolated from the culture broth of any microorganism. This paper describes the fermentation, isolation, structure elucidation and characteristics of AB-110-D.