Molecular mechanism of multi-drug resistance in Shigella isolates from rural China.

Diarrhoeal diseases and enteric infections are major causes of morbidity and mortality in the developing countries. Shigellosis was sixth in the rank of death caused by infectious disease in China. Present study assess the patterns of antimicrobial susceptibility and mutations in marA genes of Shigella isolates and its association. One hundred isolates of Shigella spp were tested to evaluate the antimicrobial susceptibility and mutation of marA through PCR-SSCP. The antimicrobial resistance profiles were: Amoxicilline-clavum (85%), Nalidixic acid (100%), Piperacilline (100%), Ciprofloxacin (25%) and Polymixin B (1.1%). S. flexneri isolates were more resistant than those ofS. sonnei to Amoxicilline-clavum (96.6% versus 0.0%, P<0.001) and Ciprofloxacin (27.3% versus 8.3%, P=0.141). S. flexneri isolates were more resistant than those of S. sonnei to three or more antimicrobial agents (96.6% versus 8.3%, P<0.001). Overall mutation rate in marA was 19%. Nucleotide sequencing showed mutations in three positionsÿcodon 6 ( Delation of C), 319 (Ala Gly) and 374 (Addition of C). The mutation of marA may play a minor role and other mechanisms may contribute to the drug resistance of Shigella spp.