Editing Beta-lactamase (section)

==== TEM beta-lactamases (class A) ====
TEM-1 is the most commonly encountered beta-lactamase in [[gram-negative bacteria]]. Up to 90% of ampicillin resistance in [[Escherichia coli|''E. coli'']] is due to the production of TEM-1.<ref name="pmid2193616">{{cite journal | vauthors = Cooksey R, Swenson J, Clark N, Gay E, Thornsberry C | title = Patterns and mechanisms of beta-lactam resistance among isolates of Escherichia coli from hospitals in the United States | journal = Antimicrobial Agents and Chemotherapy | volume = 34 | issue = 5 | pages = 739–45 | date = May 1990 | pmid = 2193616 | pmc = 171683 | doi = 10.1128/AAC.34.5.739 }}</ref> Also responsible for the ampicillin and penicillin resistance that is seen in ''[[H. influenzae]]'' and ''[[N. gonorrhoeae]]'' in increasing numbers. Although TEM-type beta-lactamases are most often found in ''[[Escherichia coli|E. coli]]'' and ''[[K. pneumoniae]]'', they are also found in other species of gram-negative bacteria with increasing frequency. The amino acid substitutions responsible for the [[#Extended-spectrum beta-lactamase (ESBL)|extended-spectrum beta lactamase (ESBL)]] phenotype cluster around the active site of the enzyme and change its configuration, allowing access to oxyimino-beta-lactam substrates. Opening the active site to beta-lactam substrates also typically enhances the susceptibility of the enzyme to β-lactamase inhibitors, such as clavulanic acid. Single amino acid substitutions at positions 104, 164, 238, and 240 produce the ESBL phenotype, but ESBLs with the broadest spectrum usually have more than a single amino acid substitution. Based upon different combinations of changes, currently 140 TEM-type enzymes have been described. TEM-10, TEM-12, and TEM-26 are among the most common in the United States.<ref name="pmid14576117">{{cite journal | vauthors = Paterson DL, Hujer KM, Hujer AM, Yeiser B, Bonomo MD, Rice LB, Bonomo RA | title = Extended-spectrum beta-lactamases in Klebsiella pneumoniae bloodstream isolates from seven countries: dominance and widespread prevalence of SHV- and CTX-M-type beta-lactamases | journal = Antimicrobial Agents and Chemotherapy | volume = 47 | issue = 11 | pages = 3554–60 | date = November 2003 | pmid = 14576117 | pmc = 253771 | doi = 10.1128/AAC.47.11.3554-3560.2003 }}</ref><ref name="pmid11585791">{{cite journal | vauthors = Bradford PA | title = Extended-spectrum beta-lactamases in the 21st century: characterization, epidemiology, and detection of this important resistance threat | journal = Clinical Microbiology Reviews | volume = 14 | issue = 4 | pages = 933–51, table of contents | date = October 2001 | pmid = 11585791 | pmc = 89009 | doi = 10.1128/CMR.14.4.933-951.2001 }}</ref><ref name="pmid15673804">{{cite journal | vauthors = Jacoby GA, Munoz-Price LS | title = The new beta-lactamases | journal = The New England Journal of Medicine | volume = 352 | issue = 4 | pages = 380–91 | date = January 2005 | pmid = 15673804 | doi = 10.1056/NEJMra041359 }}</ref> The term TEM comes from the name of the Athenian patient (Temoniera) from which the isolate was recovered in 1963.<ref>{{cite journal  | doi = 10.3201/eid2404.et2404 | title = Etymologia: TEM | year = 2018 | vauthors = Ruiz J | journal = Emerging Infectious Diseases | volume = 24 | issue = 4 | page = 709 | doi-access = free | pmc = 5875283 }}</ref>