Prevalence of quinolone resistance determinants in non-typhoidal Salmonella isolates from human origin in Extremadura, Spain Maria Jorge Campos a, e, ⁎, Gonzalo Palomo a , Lorena Hormeño a , Silvia Herrera-León c , Lucas Domínguez d , Santiago Vadillo a , Segundo Píriz a , Alberto Quesada b a Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain b Departamento de Bioquímica, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain c Servicio de Bacteriología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Spain d Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain e Grupo de Investigação em Recursos Marinhos (GIRM), Instituto Politécnico de Leiria (IPL), Peniche, Portugal abstract article info Article history: Received 8 May 2013 Received in revised form 15 October 2013 Accepted 15 January 2014 Available online xxxx Keywords: Salmonella enterica Antimicrobial resistance Quinolone resistance Mobilisable plasmid PMQR Ciprofloxacin Nalidixic acid qnrS gyrA gyrB parC parE Resistance to the quinolones nalidixic acid (NAL) and ciprofloxacin (CIP) and the occurrence of quinolone resistance determinants have been investigated in 300 non-typhoidal Salmonella from human origin, isolated in the years between 2004 and 2008, in 6 hospitals within Extremadura (Spain). Salmonella Enteritidis was the major serotype found among quinolone-resistant isolates, most of which were clustered by clonal analysis to a single clone, which presented D87 or S83 substitutions in GyrA. Eleven isolates presented the non-classical quinolone resistance phenotype (resistance to CIP and susceptibility to NAL), lacking mutations in the quinolone resistance determinant region of topoisomerase genes. Among them, one Salmonella Typhimurium isolate carried a qnrS1 gene in a low-molecular-weight plasmid, pQnrS1-HLR25, identical to plasmids previously found in the UK, Taiwan, and USA. The occurrence of this genetic element could represent a risk for the horizontal transmission of quinolone resistance among Enterobacteriaceae in the Iberian Peninsula. © 2014 Elsevier Inc. All rights reserved. 1. Introduction The most common syndrome associated with salmonellosis is a self-limited gastroenteritis that does not require chemotherapy. Sometimes, especially in the case of children, the elderly, and immunocompromised patients or when invasive infection occurs, antibiotics could be required. Fluoroquinolones represent one of the first choices among antimicrobial treatments for severe salmonellosis (Hopkins et al., 2005). However, there is great concern regarding the extensive use of quinolones that positively select resistant isolates and can favor the emergence of resistant isolates. Quinolones interact with complexes formed between DNA and topoisomerase II or topoisomerase IV, leading to inhibition of cell growth and destruction of bacterial cells (Andriole, 2005). The main mechanism of quinolone resistance is point mutations affecting the quinolone resistance determinant region (QRDR) of the genes encoding topoisomerase II, gyrA and gyrB, and/or topoisomerase IV, parC and parE, which might have an additive effect on the level of resistance shown by the microorganism(Fàbrega et al., 2009). Other chromosomal mutation could reduce susceptibility to quinolones by producing the overexpression of efflux pumps AcrAB/TolC or AcrEF/ TolC (Fàbrega et al., 2008; Giraud et al., 2006). Plasmid-mediated quinolone resistance (PMQR) mechanisms in Enterobacteriaceae are mediated by qnr, qep, aac-(6′)-lb-cr genes or oqxAB, which are rarely found in Salmonella (Strahilevitz et al., 2009). Quinolone resistance among non-typhoidal Salmonella has been documented since the early 90s in Spain and other countries (Herrera- León et al., 2011). This study aims to contribute to the field by analyzing the quinolone resistance among strains of Salmonella enterica isolated from humans in different locations of Extremadura, the Middle West region of Spain, in the 4 years between 2004 and 2008. 2. Materials and methods 2.1. Bacterial isolates and antimicrobial susceptibility A total of 300 Salmonella isolates were systematically collected from faeces, with the exception of a few strains that were collected Diagnostic Microbiology and Infectious Disease xxx (2014) xxx–xxx ⁎ Corresponding author. Tel.: +351-262783607; fax: +351-262783088. E-mail address: mcampos@ipleiria.pt (M.J. Campos). 0732-8893/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.diagmicrobio.2014.01.010 Contents lists available at ScienceDirect Diagnostic Microbiology and Infectious Disease journal homepage: www.elsevier.com/locate/diagmicrobio Please cite this article as: Campos MJ, et al, Prevalence of quinolone resistance determinants in non-typhoidal Salmonella isolates from human origin in Extremadura, Spain..., Diagn Microbiol Infect Dis (2014), http://dx.doi.org/10.1016/j.diagmicrobio.2014.01.010