Rapid urease-positive organisms turn the entire. The formation of ammonia alkalinizes the medium, and the pH shift is detected by the color change of phenol red from light orange at pH 6.8 to magenta (pink) at pH 8.1. Hydrolysis of urea produces ammonia and CO2. To date, there is no conclusive evidence about the most appropriate treatment for AmpC-producing Enterobacterales. Urea is the product of decarboxylation of amino acids. Production of pAmpCs is common in community-acquired infections, while cAmpC producers are mainly involved in healthcare-associated infections. pAmpCs are usually constitutively expressed. Strains producing cAmpCs in an inducible manner (e.g., Enterobacter spp.) usually appear susceptible to third-generation cephalosporins, which are poor inducers, but can easily yield mutants constitutively producing the enzyme which are resistant to these drugs (which are good substrates), resulting in treatment failures. Production of AmpCs can be either inducible or constitutive, resulting in different resistance phenotypes. The objective of this paper is to review the epidemiological impact, diagnostic issues and treatment options with AmpC producers.ĪmpC enzymes encoded by resident chromosomal genes (cAmpCs) are produced by some species (e.g., Enterobacter spp., Citrobacter freundii, Serratia marcescens), while plasmid-encoded AmpCs (pAmpCs) can be encountered also in species that normally do not produce cAmpCs (e.g., Salmonella enterica, Proteus mirabilis, Klebsiella pneumoniae and Klebsiella oxytoca) or produce them at negligible levels (e.g., Escherichia coli). Resistance to third-generation cephalosporins is typical of MDRs, being mainly due to the production of extended spectrum β-lactamases or AmpC-type β-lactamases. Enterobacterales are among the most common causes of bacterial infections in the community and among hospitalized patients, and multidrug-resistant (MDR) strains have emerged as a major threat to human health.