0:00 Introduction
0:47 Basics of Proteins
1:04 Genes
1:30 TEM
1:54 SHV
2:14 CTX-M
2:50 OXA
3:19 Previously
3:32 ESBL
4:00 Formation of ESBL
4:14 Note
4:34 Results in Abusing Antibiotic
5:06 Prevention of spreading Antibiotics
5:46 Important Message
6:05 Conclusion
This episode is dedicated --to the types of beta-lactamases including TEM, SHV, SHV, CTX-M, OXA, and Extended-spectrum beta-lactamase i.e ESBL. In the previous episode we already have discussed the basics of beta-lactamases.
DNA molecule has information in triplet codes and each code gives the information of particular amino acid and a stretch of DNA that encodes a protein is called the gene for that protein and for beta-lactamase there are 5 major types genes that are responsible for the synthesis of beta-lactamase enzyme. These are TEM, SHV, CTX-M, OXA, and ESBL. Although they are different they are originated form a common ancestor beta-lactamase gene.
Gram-negative bacteria. Up to 90% of ampicillin resistance in E. coli is due to the production of TEM-1
SHV-1 shares 68 percent of its amino acids with TEM-1 and has a similar overall structure. The SHV-1 beta-lactamase is most commonly found in K. pneumoniae and is responsible for up to 20% of the plasmid-mediated ampicillin resistance.
CTX-M beta-lactamases (class A), 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 80 CTX-M enzymes are currently known. There are sub-variants in this group and CTX-M-14, CTX-M-3, and CTX-M-2 are the most widespread.
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. These have been found in E. coli, K. pneumoniae, and other Enterobacteriaceae, the OXA-type have been found mainly in P. aeruginosa.
Commonly express plasmid-encoded β-lactamases that we have discussed previously confer resistance only to penicillin, not to other related antibiotics. But In the mid-1980s, a new group of enzymes, the extended-spectrum β-lactamases (ESBLs). ESBLs are beta-lactamases that hydrolyze extended-spectrum cephalosporins including cefotaxime, ceftriaxone, and ceftazidime. Thus ESBLs confer multi-resistance to these antibiotics and related oxyimino-beta lactams. In typical circumstances, they derive from genes for TEM and SHV by mutations that alter the amino acid configuration around the active site of these β-lactamases.
I have already mentioned this in the previous episode of antibiotic resistance, Estimates says that 700,000 to several million deaths result per year due to antibiotic resistance mainly due to the action of these enzymes making antibiotic therapy ineffective. New and new variants of these enzymes are evolving due to random mutations. More we misuse antibiotics more enzymes will be produced making our antibiotics ineffective. Let me tell you about a concerning point that bacteria are now found to be resistant to even the last stock of antibiotics, this means if you get infected with that bacteria then there will be no treatment option available for you.
