Four exact GES variants used for identification of GES-type extended-spectrum β-lactamases with different hydrolysis profiles and inhibitor-resistance patterns by pyrosequencing

In our proposed nomenclature system including GES-type (Guiana-Extended- Spectrum β-lactamase) or IBC-type (Integron-Borne Cephalosporinase) extended-spectrum β-lactamases (ESBLs), GES-2 has an amino acid substitution of G170N, GES-3 has two M62T and E104K substitutions, GES-4 has three M62T, E104K and G170S substitutions, GES-5 has a G170S substitution, GES-6 has two F104K and G170S substitutions, GES-7 (IBC-1) has a G104K substitution, GES-8 (IBC-2) has a A125L substitution and GES-9 has a G243S substitution, compared to the sequence of GES-1. This proposed nomenclature update would not confuse microbiologists studying GES-type ESBLs, fundamentally preventing misleading nomenclature of these antibiotic resistance genes. The definitive renaming of GES/IBC-type ESBLs can help also some researchers to conectly designate new GES-type ESBLs such as novel enzymes identified from some nationwide surveys. In order to detect rapidly and exactly GES-type ESBLs with different hydrolysis profiles and inhibitor-resistance patterns by pyrosequencing, we also proposed here the new four key amino acid substitutions and four GES-type variants as follows: (i) GES-1 able to hydrolyze ceftazidime, (ii) GES-4 able to hydrolyze ceftazidime, cefoxitin and imipenem and able to show inhibitor-resistance, (iii) GES-5 able to hydrolyze ceftazidime, cefoxitin and imipenem and (iv) GES-9 able to hydrolyze ceftazidime and aztreonam.