Editing Beta-lactamase (section)

==== CTX-M beta-lactamases (class A) ====
These enzymes were named for their greater activity against [[cefotaxime]] than other oxyimino-beta-lactam substrates (e.g., [[ceftazidime]], [[ceftriaxone]], or [[cefepime]]). Rather than arising by mutation, they represent examples of plasmid acquisition of beta-lactamase genes normally found on the chromosome of ''[[Kluyvera]]'' species, a group of rarely pathogenic commensal organisms. These enzymes are not very closely related to TEM or SHV beta-lactamases in that they show only approximately 40% identity with these two commonly isolated beta-lactamases. More than 172<ref>{{cite journal | vauthors = Ramadan AA, Abdelaziz NA, Amin MA, Aziz RK | title = Novel blaCTX-M variants and genotype-phenotype correlations among clinical isolates of extended spectrum beta lactamase-producing Escherichia coli | journal = Scientific Reports | volume = 9 | issue = 1 | pages = 4224 | date = March 2019 | pmid = 30862858 | pmc = 6414621 | doi = 10.1038/s41598-019-39730-0 | s2cid = 75136447 | bibcode = 2019NatSR...9.4224R }}</ref> CTX-M enzymes are currently known. Despite their name, a few are more active on [[ceftazidime]] than [[cefotaxime]]. They are widely described among species of [[Enterobacteriaceae]], mainly ''E. coli'' and ''K. pneumoniae''. Detected in the 1980s they have since the early 2000s spread and are the now the predominant ESBL type in the world. They are generally clustred into five groups based on sequencing homologies; CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9 and CTX-M-25.  CTX-M-15 (belonging to the CTX-M-1 cluster) is the most prevalent CTX-M-gene.<ref>{{Cite journal |last=Castanheira |first=Mariana |date=3 Sep 2021 |title=Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection |journal=Journal of Antimicrobial Chemotherapy|volume=3 |issue=3 |pages=dlab092 |doi=10.1093/jacamr/dlab092 |pmid=34286272 |pmc=8284625 }}</ref> An example of beta-lactamase CTX-M-15, along with IS''Ecp1'', has been found to have transposed onto the chromosome of ''[[Klebsiella pneumoniae]]'' ATCC BAA-2146.<ref>{{cite journal | vauthors = Hudson CM, Bent ZW, Meagher RJ, Williams KP | title = Resistance determinants and mobile genetic elements of an NDM-1-encoding Klebsiella pneumoniae strain | journal = PLOS ONE | volume = 9 | issue = 6 | pages = e99209 | date = 7 June 2014 | pmid = 24905728 | pmc = 4048246 | doi = 10.1371/journal.pone.0099209 | doi-access = free | bibcode = 2014PLoSO...999209H }}</ref> The initials stand for "Cefotaxime-Munich".<ref>{{Cite journal | vauthors = Cantón R, González-Alba JM, Galán JC |date=2012 |title=CTX-M Enzymes: Origin and Diffusion |journal= Frontiers in Microbiology |volume=3 |page=110 |doi=10.3389/fmicb.2012.00110 |pmid=22485109 |pmc=3316993 |issn=1664-302X|doi-access=free }}</ref>