Editing Beta-lactamase (section)

==== OXA beta-lactamases (class D) ====
OXA beta-lactamases were long recognized as a less common but also plasmid-mediated beta-lactamase variety that could hydrolyze [[oxacillin]] and related anti-staphylococcal penicillins. These beta-lactamases differ from the TEM and SHV enzymes in that they belong to molecular class D and functional group 2d. The OXA-type beta-lactamases confer resistance to [[ampicillin]] and [[cephalothin]] and are characterized by their high hydrolytic activity against [[oxacillin]] and [[cloxacillin]] and the fact that they are poorly inhibited by [[clavulanic acid]]. Amino acid substitutions in OXA enzymes can also give the ESBL phenotype. While most ESBLs have been found in ''[[Escherichia coli|E. coli]]'', ''[[K. pneumoniae]]'', and other [[Enterobacteriaceae]], the OXA-type ESBLs have been found mainly in ''[[P. aeruginosa]]''. OXA-type ESBLs have been found mainly in ''[[Pseudomonas aeruginosa]]'' isolates from Turkey and France. The OXA beta-lactamase family was originally created as a phenotypic rather than a genotypic group for a few beta-lactamases that had a specific hydrolysis profile. Therefore, there is as little as 20% sequence homology among some of the members of this family. However, recent additions to this family show some degree of homology to one or more of the existing members of the OXA beta-lactamase family. Some confer resistance predominantly to ceftazidime, but OXA-17 confers greater resistance to cefotaxime and cefepime than it does resistance to ceftazidime.