PER-1 Extended-Spectrum β-Lactamase Production in anAlcaligenes faecalisClinical Isolate Resistant to Expanded-Spectrum Cephalosporins and Monobactams from a Hospital in Northern Italy

Abstract

An Alicaligenes faecalis (FL-424/98) resistant to expanded-spectrum cephalosporins and aztreonam was isolated from the urine of an inpatient at the Intensive Care Unit of the Varese Hospital (Northern Italy) after antimicrobial chemotherapy with cefazolin, vancomycin, and amikacin. Clavulanic acid restored the activity of expanded-spectrum cephalosporins, suggesting the production of an extended-spectrum β-lactamase (ESβL). A crude extract of FL-424/98 showed the presence of two β-lactamase activities focusing at pH 5.3 and 7.6, respectively. The ESβL activity, purified by means of three Chromatographic steps, was found to correspond to the pI 5.3 enzyme. Determination of kinetic parameters confirmed that the enzyme efficiently hydrolyzed expanded-spectrum cephalosporins and aztreonam. A colony-blot hybridization revealed the presence of bla_PER-related sequences in FL-424/98, and sequencing confirmed the identity of this determinant with bla_PER-1, previously detected in Pseudomonas aeruginosa, Acinetobacter, and Salmonella clinical isolates from Turkey. Finding of bla_PER-1 in a species that can be part of the resident human microbiota raises the possibility that it could be an efficient shuttle for spreading of this resistance gene among other opportunistic pathogens that are normally members of the resident microbiota. Kinetic parameters determined for the PER-1 enzyme with some cephalosporin substrates were somewhat different from those previously reported.