Pheno- and genotypic characterization of Listeria monocytogenes clinical isolates from the Southwestern region of the State of São Paulo, Brazil

Abstract

Considering the lack of information available in Brazil concerning listeriosis, the present study aimed to analyze phenotypic and genotypically Listeria monocytogenes clinical isolates from the Southwestern region of the State of São Paulo, Brazil. From January 1995 to May 2005, thirteen isolates of L. monocytogenes from twelve patients with listeriosis were sent to the Adolfo Lutz Institute (Campinas Regional Laboratory, São Paulo, Brazil). The antimicrobial susceptibility of the isolates was evaluated by the microdilution broth method for ampicillin, gentamicin, trimethoprim, sulfamethoxazole and vancomycin. They were also serotyped (Denka Seiken, Japan), and sub-typed by PFGE employing ApaI and AscI and the American CDC protocol. None of the isolates showed resistance to the antibiotics tested; however, seven of them presented increased values for sulfamethoxazole MICs. Ten isolates belonged to serotype 4b, two to serotype 1/2a and only one to serotype 1/2b. After digestion with ApaI and AscI, the strains were distributed in 3 different groups according to their profile. It was observed that the spatial or temporally unrelated strains exhibited similar PFGE profiles, indicating a possible clonal relationship among them.