Antibiotic and colistin resistance pattern of Salmonella spp. isolated from pediatric patients with diarrhea in the Southern region of Vietnam

Background: Salmonella spp. is a prominent causative agent of pediatric diarrhea, with recent research emphasizing the rising concern regarding antimicrobial resistance (AMR), particularly involving colistin, a last-resort antibiotic. Methods: This study involved the collection of 500 stool samples from children with diarrhea from two tertiary pediatric hospitals in Ho Chi Minh City. Conventional methods were used to isolate Salmonella spp., and antibiotic resistance profiling against seven antibiotics was conducted using the disk diffusion method. Colistin resistance was determined by the microdilution method. Colistin resistance (mcr) genes were detected by PCR assay. A conjugation experiment with a multidrug-resistant Salmonella strain and E. coli J53 was performed, and the plasmids from this Salmonella strain were analyzed using bioinformatics. Results: The Salmonella spp. infection rate was found to be 74/500 (14.8 %). The predominant antibiotic resistance phenotype was ampicillin with 53/74 (71.6 %), followed by trimethoprim-sulfamethoxazole with 23/74 (31.1 %). Resistance rates to ceftazidime, cefotaxime and gentamicin were 14/74 (18.9 %), 13/74 (17.6 %) and 6/74 (8.1 %), respectively. Resistance to imipenem was not observed. Colistin resistance was exhibited in 3/74 (4.1 %) of isolates, all harboring the mcr-1 gene. The plasmid carrying the mcr-1 gene could transfer to E. coli, which belongs to the IncX4 type and contains IS26. Conclusion: This study provides valuable insights into the antibiotic resistance profiles of Salmonella spp. isolated from pediatric patients, with particular emphasis on colistin resistance.