Downloaded from www.microbiologyresearch.org by IP: 54.146.34.65 On: Wed, 20 Jul 2016 07:58:07 Antimicrobial resistance and genetic characteristics of integron-carrier shigellae isolated in Hungary (1998–2008) Noe ´mi No ´ gra ´ dy, 1 Margit Kira ´ ly, 1 Kla ´ ra Borba ´s, 2 A ´ kos To ´ th, 3 Judit Pa ´ szti 1 and Istva ´n To ´ th 4 Correspondence Istva ´n To ´ th tothi@vmri.hu Received 10 February 2013 Accepted 24 June 2013 1 Department of Phage Typing and Molecular Epidemiology, National Center for Epidemiology, H-1097 Budapest, Gya ´li u ´ t 2-6, Hungary 2 Central Regional Laboratory of Enteric Pathogens, National Center for Epidemiology, H-1097 Budapest, Gya ´li u ´ t 2-6, Hungary 3 Department of Bacteriology, National Center for Epidemiology, H-1097 Budapest, Gya ´li u ´t 2-6, Hungary 4 Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, H-1143, Budapest, Hunga ´ ria krt. 21, Hungary Antimicrobial susceptibility, integron carriage, genetic relationship and presence of some important virulence genes of the integron-carrier strains of Shigella sonnei (n5230) and Shigella flexneri (n522) isolated from stool samples of patients in Hungary between 1998 and 2008 were investigated. Sixty-seven per cent (168/252) of the strains were resistant to sulfamethoxazole/ trimethoprim (SxT) followed by streptomycin (S, 47 %), ampicillin (A, 32 %) and tetracycline (Tc, 28 %). Thirty-six per cent (90/252) exhibited multidrug resistance, mostly showing SSxTTc or ASSxTc, ASSxTTc resistance patterns. An S. sonnei strain of imported origin was resistant to cefotaxime and harboured a bla CTX-M-55 -type extended-spectrum b-lactamase gene. Altogether 33 % of the S. sonnei (n575) and 14 % of the S. flexneri (n53) strains had either class 1 or class 2 integrons or both. The variable regions encoded aadA1 or dfrA1-aadA1 genes for the class 1 and dfrA1-sat2-aadA1 or dfrA1-sat2 genes for the class 2 integrons. Pulsed-field gel electrophoresis analysis revealed that those strains that have different integron types represented different genetic clusters. The Shiga toxin (stx1) gene was identified in one S. sonnei strain and the cdtB gene was detected in an S. flexneri strain. The results reveal the high incidence of antibiotic resistance among Shigella isolates and the presence of the stx1 gene in S. sonnei and the cdtB gene in S. flexneri. The genetic diversity of Shigella spp. isolated recently in Hungary was also demonstrated. INTRODUCTION Shigellosis is one of the frequently diagnosed diarrhoeal diseases both in developing and industrialized countries. Antibiotic treatment is usually indicated for individuals with moderate or severe symptoms of shigellosis, because it can reduce the duration and severity of symptoms, excretion of organisms and prevent potentially lethal complications. However, increasing antimicrobial resist- ance and carriage of mobile genetic elements that encode antimicrobial resistance genes, such as class 1 and class 2 integrons of Shigella spp., has been reported worldwide (Oh et al., 2003; Peirano et al., 2005; Pan et al., 2006; Kuo et al., 2008). Essential events in the pathogenesis of Shigella infections include bacterial invasion of epithelial cells, escape from the phagosome, intracellular multiplication, extension into adjacent epithelial cells and induction of apoptosis in macrophages (Guichon et al., 2001). Several virulence factors have been associated with Shigella spp., the most common being the ability to colonize and invade the intestinal cells. Another virulence factor, related mainly to Shigella dysenteriae, is its capacity to produce an exotoxin called Shiga toxin (Stx), which is not excreted by the bacteria but is released only during cell lysis (Cantey, 1985). Despite its clear toxigenicity, the role of Stx in Abbreviations: CDT, Cytolethal distending toxin; ESBL, extended- spectrum b-lactamase; MDR, multidrug resistance; PFGE, pulsed-field gel electrophoresis; Rif R , rifampicin resistant; Stx, Shiga toxin; TC, transconjugant. Journal of Medical Microbiology (2013), 62, 1545–1551 DOI 10.1099/jmm.0.058917-0 058917 G 2013 SGM Printed in Great Britain 1545