Serotypes, Antibiotic Resistance, and Class 1 Integrons in Salmonella Isolates from Pediatric Cases of Enteritis in Tehran, Iran Reza Ranjbar, 1 Giovanni M. Giammanco, 2 Shohreh Farshad, 3 Parviz Owlia, 4 Aurora Aleo, 2 and Caterina Mammina 2 Abstract The present study was conducted to investigate serotype distribution, antimicrobial resistance patterns, carriage of class 1 integron, and clonality of Salmonella strains isolated from patients aged 0–12 years in Tehran, Iran, during 2007–2008. A total of 139 Salmonella isolates were studied. Salmonella serotypes Enteritidis, Infantis, and Typhimurium included 84.9% of isolates, Enteritidis accounting for 41.7%. The most prevalent resistances were to doxycycline (64.7%), nalidixic acid (61.2%), tetracycline (51.8%), and streptomycin (42.8%). Fifty-three (38.1%) isolates contained class 1 integron. Eight different gene cassettes were identified, aadA1 being the most fre- quently encountered. Pulsed-field gel electrophoresis showed that integron-positive Salmonella strains belonging to serotypes Infantis, Enteritidis, and Typhimurium were attributed to two, three, and five different pulsotypes, respectively. The findings indicated that the distribution and drug resistance pattern of most prevalent Salmo- nella serotypes were broadly similar to that reported globally from human isolates. Presence of class 1 integrons was common among Salmonella serotypes in Tehran, Iran. Concurrent clonal expansion and horizontal trans- mission events seem to contribute to increase in drug resistance prevalence among Salmonella serotypes. Introduction I nfections caused by Salmonella spp. are increasing in many countries including Iran (Ranjbar et al., 2007, 2010). During the last decades, the emergence of antimicrobial drug- resistant strains has been reported within different serotypes of Salmonella enterica (Guerra et al., 2000; Parry, 2003; Randall et al., 2004; Butaye et al., 2006; Irajian et al., 2009). Resistance to antimicrobial agents is often associated with the spread of transmissible plasmids and integrons (Guerra et al., 2000; Randall et al., 2004; Cabrera et al., 2006; Peirano et al., 2006; Rodrı ´guez et al., 2006; Murphy et al., 2007; Jin and Ling, 2009; Khan et al., 2009; Krauland et al., 2009). The capture of resis- tance determinants by integrons, in conjunction with their association to mobile genetic elements such as transposons, plasmids, and genomic islands, is accompanying the rapid evolution of multiple drug resistance among clinical isolates of Gram-negative bacteria, including S. enterica (White et al., 2001; Leverstein-van Hall et al., 2002; Mooij et al., 2009). Class 1 integrons are the most frequent and usually contain one or more gene cassettes that constitute a variable region, flanked by two conserved segments (5 0 -CS and 3 0 -CS) (Hall and Stokes, 1993). Their ability to capture and excise gene cas- settes, usually encoding antimicrobial drug resistances, makes them especially suited for dissemination and re- arrangement of resistance genes (Hall and Stokes, 1993; Mazel, 2006). The need for molecular epidemiological studies about the role of integrons in antimicrobial drug resistance in bacteria is increasingly evident. Reports from some Asian countries have shown a high prevalence of class 1 integrons in Gram- negative clinical isolates (Chang et al., 2000, 2007; Yu et al., 2003; Van et al., 2007; Japoni et al., 2008). These data suggest that the integrons are relatively common in this continent, especially among the Enterobacteriaceae, and therefore, they effectively contribute to the spread of antimicrobial drug re- sistance in healthcare settings. The present study was conducted to investigate the distri- bution of serotypes and antimicrobial resistance patterns among nontyphoidal Salmonella strains isolated from pediat- ric patients in Tehran, Iran, over the 2-year period (2007– 2008). Moreover, the prevalence of class 1 integrons and the 1 Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. 2 Department of Sciences for Health Promotion ‘‘G. D’Alessandro,’’ University of Palermo, Palermo, Italy. 3 Professor Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran. 4 Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran. FOODBORNE PATHOGENS AND DISEASE Volume 8, Number 4, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089=fpd.2010.0736 547