ANTIMICROBIAL RESISTANCE AND GENETIC DIVERSITY OF SHIGELLA SONNEI ISOLATES FROM ROMANIA.

Although not endemic in the European Union and European Economic Area, shigellosis is included among the priority food- and waterborne diseases carefully surveyed by the European Centre for Disease Prevention and Control. From 2010 to 2012, 1018 cumulated confirmed shigellosis cases were reported to the European Surveillance System by Romania. This retrospective study aimed to provide insights into the antibiotic resistance and genetic diversity of a set of Shigella sonnei isolates recovered during that period. A total of 59 S. sonnei isolates were subjected to antimicrobial susceptibility testing (ampicillin, cefotaxim, chloramphenicol, streptomycin, gentamicin, kanamycin, tetracycline, sulphonamides compound, trimethoprim, trimethoprim-sulfamethoxazole, nalidixic acid, and ciprofloxacin), biotyping, and molecular characterization of resistance to third-generation cephalosporins, fluoroquinolones, and integron content. Pulsed-field gel electrophoresis (PFGE) was performed in order to assess the genetic relatedness of the isolates. Thirty-eight (64%) of the studied isolates displayed multidrug-resistant (MDR) phenotypes, the most common resistance profile comprising resistance to ampicillin, streptomycin, sulphonamides compound, trimethoprim, and trimethoprim-sulfamethoxazole. Resistance to cefotaxim was detected in a biotype g blaCTX-M-15 and a biotype e blaCMY-2-positive isolate, respectively. Resistance to ciprofloxacin and/or nalidixic acid was detected in three MDR isolates and was due to known mutations in gyrA gene leading to aminoacid substitutions (i.e. Ser83Leu, Asp87Tyr, Asp87Gly). Either class 1 or class 2 integrons were identified in 10 isolates. Comparisons of XbaI PFGE patterns of S. sonnei isolates revealed 9 clonal groups and 6 unique patterns. The genotyping results suggested that dissemination of clonal groups of S. sonnei may have persisted over the years in Romania.