Frequency of Shigella dysenteriae in Patients with Bacillary Dysentery and its Antimicrobial Resistance

Abstract

This study was carried out in Khartoum State during the period October 2008 - March 2009 to determine frequency of Shigella dysenteriae in Patients with bacillary dysentery and its antimicrobial resistance. A total of 253 stool specimens were collected from patients suspected to have bacillary dysentery attended Omdurman Teaching Hospital and Friendship Hospitals were included. The specimens were cultured on selanite F broth, xylose lysine deoxycholate agar to isolate the causative agent. The identification of the isolated bacteria was done by colonial morphology, Gram stain and API 20E. Antimicrobial resistance of each isolate was determined by modified Kirby – Bauer disk diffusion method. E.test was used to determine minimum inhibitory concentration of antimicrobial agents. The result reveled that Shigella dysenteriae was isolated from 8 (3%) specimens. Study on antimicrobial susceptibility test revealed that the resistance rate of Shigella dysenteriae was (100%) to ceftazidime and tetracycline, (0%) to ciprofloxacin, gentamicin and chloramphenicol. The minimum inhibitory concentration (MIC) of chloramphenicol was (0.1- 0.01 μg), MIC of tetracycline (5 – 0.5 μg), MIC of gentamicin (0.1-0.25 μg), MIC of ciprofloxacin (0.01 -0.004 μg) and the MIC of ceftazidime (1 -0.1 μg). The MIC50 and MIC90 of antibiotics were 0.5μg to tetracycline, 0.004 ciprofloxacin, 0.25 μg gentamicin, 0.01μg chloramphenicol, and the MIC50 of ceftazidime was 0.1 μg and the MIC90 of ceftazidime was 1 μg. The study concluded that the responsibility of Shigella dysenteriae in causing Bacillary dysentery is slightly high. The antimicrobial resistance for Shigella dysenteriae to the routinely used antibiotics was also high too.