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Antimicrob Agents Chemother. Nov 1997; 41(11): 2374–2382.
PMCID: PMC164131
Characterization of a new TEM-derived beta-lactamase produced in a Serratia marcescens strain.
M Perilli, A Felici, N Franceschini, A De Santis, L Pagani, F Luzzaro, A Oratore, G M Rossolini, J R Knox, and G Amicosante
Dipartimento di Scienze e Tecnologie Biomediche, Cattedra di Chimica Biologica, Facoltà di Medicina e Chirurgia, Università degli Studi dell'Aquila, L'Aquila, Italy.
A natural TEM variant beta-lactamase was isolated from an epidemic strain of Serratia marcescens. Nucleotide gene sequencing revealed multiple point mutations located in the 42-to-44 tripeptide and positions 145 to 146, 178, and 238. In addition, a glutamic acid 212 deletion was also found. The purified enzyme was studied from a kinetic point of view, revealing the highest catalytic efficiency (k[cat]/Km) values for ceftazidime and aztreonam compared with the TEM-1 prototype enzyme. The in vitro resistance correlated with kinetic parameters, and the enzyme also mediated resistance to some penicillins and an ampicillin-clavulanic acid combination. The mutational and kinetic changes are discussed in relation to the three-dimensional crystallographic structure of the wild-type TEM-1 enzyme.
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