PLASMID SCREENING OF MULTIRESISTANT SHIGELLA ISOLATES

Abstract

Twelve isolates (3.67%) out of 327 diarrheal cases were identified biochemically and serologically as shigellae. Shigella flexneri was the most frequently isolated subgroup of shigella (2.14%) followed by Shigella boydii (1.22%), and Shigella dysenteriae (0.3%), respectively. The susceptibility of the isolates to 18 different antimicrobial chemotherapeutic agents was performed by the disc diffusion method. All the isolates were resistant to 1-6 of the antimicrobial agents under test. The majority of shigella isolates (58.3%) were resistant to at least 4 of the antimicrobial agents. The resistance patterns of shigella isolates were heterogenous, since as many as 8 different patterns were recognized among the tested isolates. The plasmids of shigella isolates were detected by agarose gel electrophoresis. The results revealed very heterogenous profiles. Eleven different profiles were recognized for the 12 shigella isolates. All the shigella isolates were harboring at least 3 plasmids. The approximate molecular weight of shigella plasmids were ranged from 1. 2-5.2 Mega Dalton (MDa). The data revealed that there is no consistent relationship between the plasmid profiles and the resistance patterns of the isolates. Moreover, one of the plasmid profile was shared by 2 of the shigella isolates (isolate no. 80 & 256) although they have different susceptibility patterns. However, in some instances, isolates sharing some resistance markers, had one or more plasmid in common.