Diversity of Plasmid Profile in Multi-drug Resistant Non- E. coli Intestinal Flora Lacking Association with Resistance Phenomenon

Aims: To study the plasmid diversity of intestinal non- Escherichia coli community, describe their potential as a reservoir of antibiotic resistance phenomenon and to find any association of resistance phenomenon with the plasmid content if any.

Place and Duration of the Study: Department of Microbiology, Jahangirnagar University, Dhaka between June 2014 to July 2015.

Methods: Stool samples were cultured onto MacConkey agar plates for selective isolation of Gram negative bacteria. Identification of intestinal non- E. coli was done through conventional biochemical tests according to Bergey’s Manual of Systematic Bacteriology. Plasmid extraction was done according to the modified hot alkaline method. Antibiogram was carried out by disc diffusion method and MIC determination by agar dilution assay.

Results: One hundred and forty four representative colonies were selected from stool culture of 60 healthy human subjects. Of 144 colonies, 90 belonged to 21 non- E. coli species shared by 11 genus. Majority of the isolates (81%, 73 of 90) showed resistance to one or more antibiotics while the rest 18.9% (17 of 90) were sensitive to all the antibiotics used (amoxicillin, cefixime, ciprofloxacin, gentamicin, sulfamethoxazole-trimethoprim). Highest resistance frequency was observed against amoxicillin (67%) followed by cefixime (28%), gentamicin (24%), sulphamethoxazole–trimethoprime (16%), tetracycline (14%), and ciprofloxacin (8%). A notable proportion of the bacteria (20%) were found to be multi-drug resistant. Majority of the isolates (57%) were found to contain 1 to 6 plasmids and exhibited 34 different plasmid profiles. Thirty two isolates (of 90) carried plasmids with high molecular weight (> 20 Mdal) including 4 isolates that carried large plasmids of approximately 140 Mdal size.

Conclusion: Findings of this study indicate that intestinal non- E. coli population may function as a reservoir of heterogeneous plasmid. Although no direct association was observed between resistance phenomenon and presence of plasmids in general, to study the role(s) of individual plasmid for encoding any particular drug resistance phenomenon and /or pathogenic gene(s) would be an interesting line of inquiry.