Extended Spectrum β-Lactamases (ESBL)

ESBL refers to Extended Spectrum β-Lactamases. ESBL falls  under Group 2be and Class A by functional and molecular classification respectively of β-Lactamases. Various types of ESBL have been recognized, the number of which is accounted to more than 700 ESBL.


Most ESBLs are derivatives of TEM or SHV enzymes  [2,3] and  found in E. coli and K. pneumoniae. Besides, they have also been found in Proteus spp., Providencia spp., and other genera of Enterobacteriaceae.

Fig. 1 Screening Test of ESBL by Kirby Bauer Disk Diffusion on Muller Hinton Agar (Positive).
The diameter of Zone of inihibition was 13mm with Ceftazidime plus Clavulanic acid.

The types of ESBL are enlisted below:
i) TEM
ii) SHV
iii) CTX-M and Toho β-Lactamases
iv) OXA
v) Other ESBLs:
Related ESBL: PER-1, PER-2, VEB-1, CME-1and TLA-1.
Uncommon: SFO-1and GES-1.
Non-TEM and non-SHV ESBLs:BES-1, TLA, IBC [4]

REFERENCES
1. Raut S and Adhikari B.  2015. ESBL and their identification in peripheral laboratories of Nepal. Nepal Med Coll J; 17 (3-4): 176-181
2. Bush, K., G. A. Jacoby, and A. A. Medeiros. 1995. A functional classification scheme for β-lactamases and its correlation with molecular structure. Antimicrob. Agents Chemother. 39:1211–1233.
3. Jacoby, G. A., and A. A. Medeiros. 1991. More extended-spectrum β-lactamases. Antimicrob. Agents Chemother. 35:1697–1704.
4.Paterson D.L. and Bonomo R.A. 2005. Extended-Spectrum β-Lactamases: a Clinical Update. Clinical Microbiology Reviews. ASM. Vol. 18, No. 4, p. 657–686.