The Enterobacterales order contains 7 families with more than 40 bacterial genera which are isolated from various types of environment. The genera Shimwellia, Obesumbacterium, Rahnella, Citrobacter, Klebsiella, Raoultella, Serratia and Enterobacter are often found in the beer brewing process. The ability of these bacteria to grow and multiply in the finished beer is minimal. The bacteria occur primarily as contamination of yeast. They are harmful because these bacteria produce sensory undesirable substances (e.g. dimethylsulfide, diacetyl, acetoin) at the beginning of the main fermentation and get into the finished beer. Some species are involved in the formation of N-nitrosamines harmful for health. Here we present an overview of the basic morphological and physiological properties of these bacteria and describe their importance from the point of view of harmfulness in the beer brewing process.