A TEM-DERIVED EXTENDED-SPECTRUM BETA-LACTAMASE IN PSEUDOMONAS-AERUGINOSA

A clinical strain of Pseudomonas aeruginosa, PAe1100, was found to be resistant to all antipseudomonal beta-lactam antibiotics and to aminog lycosides, including gentamicin, amikacin, and isepamicin. PAe1100 pro duced two beta-lactamases, TEM-2 (pi 5.6) and a novel, TEM-derived ext ended-spectrum beta-lactamase called TEM-42 (pi 5.8), susceptible to i nhibition by clavulanate, sulbactam, and tazobactam. Both enzymes, as well as the aminoglycoside resistance which resulted from AAC(3)-IIa a nd AAC(6')-I production, were encoded by an 18-kb nonconjugative plasm id, pLRM1, that could be transferred to Escherichia coli by transforma tion. The gene coding for TEM-42 had four mutations that led to as man y amino acid substitutions with respect to TEM-2: Val for Ala at posit ion 42 (Ala42), Ser for Gly238, Lys for Glu240, and Met for Thr265 (Am bler numbering), The double mutation Ser for Gly238 and Lys for Glu240 , which has so far only been described in SHV-type but not TEM-type en zymes, conferred concomitant high-level resistance to cefotaxime and c eftazidime, The novel, TEM-derived extended-spectrum beta-lactamase ap pears to be the first of its class to be described in P. aeruginosa.