Identification of Ipa and Stx Genes and Their Antibiotic Resistance Pattern in Shigella Sonnei isolated from Clinical Samples using Multiplex-PCR

Shigella is responsible for shigellosis or bacillary dysentery, which is transmitted by contaminated food. Invasion Plasmid Antigens (Ipa) gene leads to intra- or extra-cellular spreading of Shigella. The current study aimed to identify Ipa and stx genes in Shigella sonnei isolated from clinical samples by multiplex-PCR and determine their antibiotic resistance profile.
In this study, 150 stool samples were collected from different treatment centers in Tehran. After culture-based microbiological and biochemical tests, 60 Shigella sonnei species were identified. Antibiotic susceptibility tests were performed by disk diffusion method according to CLSI guideline. Then, multiplex-PCR assay was employed to identify stx and ipa genes.
The results showed that the highest and lowest resistance was related to co-trimoxazole (n=60, 100%) and ceftriaxone (n=10, 16.7%), respectively. Out of the 60 isolates, 57 strains (95%) were positive for ipaH gene and other virulence genes were not detected in any of the samples.
ipaH, due to presence in the majority of Shigella strains, can be a candidate to identify this organism. It seems that indiscriminate use of antibiotics is one of the causes of antibiotic resistance in Shigella species.