TEM-187, a New Extended-Spectrum β-Lactamase with Weak Activity in a Proteus mirabilis Clinical Strain

Abstract

A Proteus mirabilis clinical strain (7001324) was isolated from urine sample of a patient hospitalized in a long-term-care facility. PCR and cloning experiments performed with this strain identified a novel TEM-type ␤-lactamase (TEM-187) differing by four amino acid substitutions (Leu21Phe, Arg164His, Ala184Val, and Thr265Met) from TEM-1. This characterization provides further evidence for the diversity of extended-spectrum ␤-lactamases (ESBL) produced by P. mirabilis and for their potential spread to other Enterobacteriaceae due to a lack of sensitive detection methods used in daily practice. Before the CTX-M era, TEM-type extended-spectrum ␤-lactamases (TEM-ESBL) were the most prevalent mechanism of resistance to ␤-lactam antibiotics in Enterobacteriaceae. They emerged from the parental penicillinases TEM-1 and TEM-2 (1). Since the 1990s, different enzymes that combine novel substitutions leading to an ESBL pattern in Proteus mirabilis isolates such as TEM-10, TEM-24, TEM-52, TEM-72, TEM-87, and TEM-92 have been reported (2-6).In 2002, during a study on ESBL detection and the agreement between four different techniques, Leverstein-van Hall et al. identified a novel TEM variant that associated the Arg164His substitution observed in numerous TEM-ESBL with Leu21Phe and Thr265Met substitutions (7). This ␤-lactamase, designated TEM-75, was produced by Escherichia coli or Klebsiella pneumoniae strains and is easily detected by different methods; the ESBL-Etest method was considered the best. Recently, we reported on an ESBL-producing Proteus mirabilis isolate incorrectly detected as a TEM-24-producing clone recovered from urine of spinal cord injury patients (8). During this outbreak period, one patient was previously infected by a new TEM-derived ESBL called TEM-187 with a new combination of four substitutions in bla TEM gene.In this study, we characterized the genetic support and the enzymatic activity of TEM-187. A Proteus mirabilis clinical strain (7001324) was isolated from a urine sample of a patient hospitalized in the Physical Medicine Department at Nantes University Hospital, France. This patient had been treated with different antibiotics for urinary tract colonization/infections in the previous months. P. mirabilis 7001324 harbored a high level of resistance to amoxicillin and ticarcillin but was fully susceptible to penicillinclavulanate combinations and expanded-spectrum cephalosporins according to the results determined with a Vitek2 automated system with an AST-N103 card (bioMérieux, Marcy l'Etoile, France) or with a Phoenix automated system with an NMIC-93 gallery (BD Diagnostics, Sparks, MD), using a standard protocol. The double-disk synergy test (Mast Cica-␤ ESBL test) was negative for P. mirabilis 7001324 (9). Alone, a modified double-disk test with a 35-mm interdisk distance between ceftazidime-and amoxicillin-clavulanate-containing disks was positive. ␤-Lactam MICs were determined by a microdilution method on MuellerHinton agar (BD) with an inoculum of 10 4 CFU per spot (Table 1). P. mirabilis...

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