Plasmid Profile Analysis and Antibiotic Resistance Patterns of Shigella Isolates from Kwale County, Kenya

Shigellosis caused by multidrug-resistant (MDR) Shigella strains is an important cause of morbidity and mortality in developing countries. Shigella strains usually harbour heterogeneous population of plasmids which can confer resistance to different antibiotics. A hospital based survey was conducted to determine the pattern of antimi- crobial resistance and plasmid profiles in Shigella species from diarrheal patients in Kwale county. Twenty nine (8.1%) Shigella spp were obtained from 360 stool samples collected and each strain screened for antimicrobial resistance to common antimicrobial agents and presence of plasmids. High antibiotic resistance was found to Sulfamethoxazole-tri- methoprim (79%), Ampicillin (75.9%) and Streptomycin (75.9%). All isolates were sensitive to ciprofloxacin, ceph- alosporins and Aztreonam antibiotics. Ninety seven percent of the isolates screened contained one or more plasmids ranging from 1-6. Majority were small plasmids. Species specific plasmids of 3.2kb, 9.0kb, and 3.8kb were found in Shigella flexneri, Shigella dysenteriae and Shigella sonnei respectively, while 34.5% and 79.3% MDR strains harbored large (>100kb) and middle range self-transmissible plasmids (10-100kb). In all species, no association was found be- tween specific plasmid profile and antibiotic resistance patterns. Significant association was found between carriage of 80kb plasmid in S. dysenteriae (P<0.001), combined 48kb and 80kb plasmids in S. flexneri (P=0.002) and S. sonnei (P=0.041) and MDR phenotype. The middle range plasmids specified resistance to Sulfamethoxazole-trimethoprim, Ampicillin, Streptomycin and Tetracycline. This study reports the usefulness of plasmid profiling in detection and discrimination of Shigella strains in Kenya. The study also shows that middle range self-transferable R-plasmids are widespread among the circulating MDR Shigella strains indicating the important role of these genetic elements in the development and dissemination of multidrug resistance.