Distribution of extended-spectrum β-lactamases (ESBLs) among Salmonella serogroups isolated from pediatric patients

Extended-spectrum β-lactamases (ESBLs) and fluoroquinolones are generally used to treat invasive Salmonella infections, but emergence of antibiotic-resistant strains are increasing worldwide. This study was aimed to investigate the distribution of ESBLs among Salmonella serogroups isolated from pediatric patients in Tehran, Iran. The study included all Salmonella isolates recovered from pediatric patients admitted to Children’s Medical Center, Tehran, Iran during 2015-2016. Bacterial isolation and identification were performed by standard biochemical and agglutination tests. Antimicrobial susceptibility testing was done according to the Clinical and Laboratory Standards Institute (CLSI). Polymerase chain reaction was used to identify the genetic determinants responsible for ESBL phenotypes. A total of 138 S. enterica serovars were isolated from stool specimens, including serogroup A (1), serogroup B (18), serogroup C (41) and serogroup D (78). Forty isolates out of 138 Salmonella strains had shown ESBL-positive phenotype. All ESBL-positive isolates showed multiple resistant phenotype. Resistance to more than 3 antimicrobial agents was observed among ESBL-positive strains. The frequency of Salmonella strains carrying the blaCTX, blaTEM and blaSHV genes was 17 (12.3%), 40 (29.9%) and 4 (2.89%) respectively. The high rates of ESBLs positive-Salmonella strains recovered from pediatric patients is alarming and indicates a necessity to substitute the cephalosporins with a proper alternative