The increase in the bacterial antimicrobial resistance is very frightening because of difficulties in treatment of bacterial infections in both animals and humans. In terms of resistance of Gram negatives against beta lactam antibiotics which are commonly used in treatment, the increase is mostly related with high variety of beta-lactamase enzymes produced by bacteria. It is known that beta-lactamase enzymes posses structural heterogeneity and each shows different substrat (antibiotic) specificity. Hence, classification of beta-lactamases of Gram negative bacteria is challenging and updated regularly after new beta-lactamases are identified. In the present review article, beta-lactamases of Gram negatives determined until present are discussed and the findings of Turkish studies related with beta-lactamases of Gram negatives from domestic animals and livestock are reviewed.