Aim: Determination of the diversities and antibiotic resistances of the most abundant aerobic culturable bacteria and their survival in 15 German biogas plants (BGPs). Methods and Results: Microbiological standard media (complex and selective media) were applied to enumerate mesophilic and oligotrophic bacteria (Enterobacteriaceae, Salmonella, staphylococci and enterococci) in input and output samples of BGPs. Concentrations of aerobic culturable bacteria in outputs were mostly one to two orders of magnitude lower than in input samples. In total, 852 isolates from input and 902 from output samples were identified either by partial 16S rRNA gene sequencing or Matrix-assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) analysis. Antibiotic resistance screening of target families against veterinary relevant antibiotics resulted in similar resistance pattern in input and output samples. Conclusions: Potentially pathogenic bacteria were detected in output samples of BGPs, but in decreased abundance. The selectivity of the most applied clinical standard media was insufficient. Significance and Impact of the Study: Only little is known about the release of antibiotic resistant and potentially pathogenic bacteria from BGPs. However, this study indicates the detection of several potentially pathogenic bacteria in output samples, which showed several antibiotic resistances.