Background: Salmonella infections are very common and an important public healthrnproblem in many parts of the world. In sub-Saharan Africa there is very little direct data onrnstrain type or antibiotic resistance. Research to date, as well as unpublished reports fromrndifferent health institutions in Ethiopia, has indicated that salmonellosis is a commonrnproblem and the extensive use of the first line drugs has led to the development of multiplerndrug resistance at a level which could pose a serious problem in the near future.rnOBJECTIVES: The study was aimed at defining the serovars responsible for Salmonellarninfection, estimating the level of antibiotic resistance, investigate molecular basis ofrnresistance and observing molecular polymorphism among Salmonella species isolated fromrnchildren in Ethiopia.rnMATERIALS AND METHODS: Pediatric patients (n=1225) presenting with diarrhoea orrnfever from pediatric out patient department of Tikur Anbessa University Hospital, AddisrnAbaba (n= 825) and Jimma University Hospital, south west Ethiopia (n= 400) wererninvestigated for enteric pathogens during January 2006 to June 2008. Forty eight Salmonellarnisolates collected in Tikur Anbessa hospital between January, 2004 and December, 2005rnfrom similar age group were analyzed together. Stool specimens were collected forrnmicroscopic examination and culture. In addition blood specimens were obtained for culture.rnBrain Heart Infusion broth was used for blood culture and Selenite F broth enrichmentrnfollowed by plating on Deoxycholate agar (DCA) and Xylose lysin deoxycholate agarrn(XLD) were used for stool culture. Identification of Salmonella species was carried outrnusing API-20E, serology with antisera and strain were characterized using multilocusrnsequence typing (MLST). Based on resistance pattern, site of collection and type ofrnspecimen in which the isolate was detected, S. Concord isolates were selected andrninvestigated for plasmid profile, incompatibility grouping, pulsed field gel electrophoresisrn(PFGE), MLST profile and fliC gene sequencing using standard procedures. In addition, 48rnpreviously collected Salmonella isolates before the commencement of the present studyrnwere sero-grouped and serotyped.rnRESULTS: A total of 463 entropathogens were isolated from 1225 pediatric patients. Thernisolates were: 65 Salmonella species, 61 Shigella species and 337 parasites. Among the 113rnxirnSalmonella isolates (65 + 48 previously collected), serogroup C, B, D and E were isolated atrna frequency of 78.8%, 11.5%, 8% and 1.8% respectively. Most of the Salmonella isolatesrnwere from stool (68%) and the rest were from blood (32%). No isolate was detected fromrnboth blood and stool of the same patient. A total of 12 serotypes were identified namely; S.rnConcord (82), S. Colindale (1), S. Gatow (3), S. Laronchelle (1),rnS. Garoli (1), S. Colorado (1), S. Typhimurium (7) S. Paratyphi B(2), S. Haifa (1) S. Typhirn(2) S. Enteritidis (4), and S. Butantan (2). Eighty nine percent of the group C isolates werernS. Concord. S. Concord isolates were highly resistant to ampicillin, trimethoprimsulfamethoxazole,rnceftriaxone, amoxicillin, chloramphenicol, gentamicin, and tetracycline.rnLow resistance rate was observed for nalidixic acid and ofloxacin and there was nornresistance to ciprofloxacin by disk diffusion test. However, E-test result indicated thernpresence of one resistant, one intermediate and twenty two (26.8%) Concord isolates whichrnshowed reduced susceptibility to ciprofloxacin. The extended spectrum beta lactamasern(ESBL) screening test result showed that 98.8% of S. Concord were positive for ESBLrnproduction. Plasmid analysis showed that all characterized S. Concord isolates harboredrnmultiple copies of small and large plasmids. The molecular weight of plasmids varied fromrnless than five to 170 kb with 120, 118 and 95 kb being the most prevalent. Plasmid repliconsrnA/C, I1 and incFI were found in the majority of the isolates. Different plasmid studiesrnindicated that A/C and incFI replicons are associated with multi drug resistance (MDR)rnSalmonella isolates. A total of 16 pulse field gel electrophoresis (PFGE) profiles were seenrnamong the 23 Concord group and 5 non Concord isolates. Every sequence type (ST) had arnunique PFGE profile which indicates that S. Concord in Ethiopia is in an endemic situation,rnrather than a spread of a clonal type (has many different point sources/reservoirs). The samernST and PFGE types were found in Addis Ababa and in Jimma suggesting movement ofrninfected people/reservoirs between the two cities. Multilocus sequence typing (MLST)rnanalysis showed the presence of a total of seven STs among 58 isolates. ST533, ST534 andrnST599 are single locus variants. Because they differ in only one of the seven loci, they arernclosely related genetically and make a single Concord group. Distantly related serotypes likernGatow and Colindale had sequence types that differ by more than one allele from Concordrngroup. Molecular serotyping using sequencing of the fliC gene was able to differentiaternxiirnbetween S. Haifa and the S. Concord group of isolates indicating the possibility of its role inrnmolecular serology. For our strain collection, it seems therefore that fliC sequencing canrncomplement MLST for classification and strain differentiation.rnCONCLUSION AND RECOMMENDATIONS: Salmonellosis in children in these twornregions of Ethiopia is mainly due to non-typhoidal salmonellae particularly with S. Concord.rnThis is different from other countries where S. Enteritidis and S. Typhimurium accounted forrnthe majority of salmonellosis. Both phenotypic and genotypic characterization indicated thatrnS. Concord is highly resistant and present in endemic situation in Ethiopia. The presence ofrnmany multi-drug resistant strains containing genes for ESBL production and the emergencernof reduced susceptibility to ciprofloxacin in this study posed a major concern in the searchrnfor efficient antimicrobial therapy of Salmonella infections in the near future. Thereforernmore comprehensive studies should be designed to trace its source and distribution withinrnthe country and to monitor antibiotic resistance pattern over time.