Abstract
Background and Objectives: Urinary tract infections(UTIs) are the most prevalent infections after respiratory infections, particularly in females. Escherichia coli is the most common causative bacterium in UTI. There are different methods to study these bacteria based on phenotypic and genotypic characteristics. Phenotypic characteristics tend to vary, but genotypic characteristics are more stable. Plasmid profile analysis provides useful information in tracing the outbreak origin and number of different clones which exist in the outbreak. This study was performed to show plasmid profiles of E.coli strains isolated from UTI of in- and out-patients and their restriction endonucleases digestion patterns to survey epidemiologic relationships between isolated strains.
Materials and Methods: For plasmid DNA extraction, alkaline lysis procedure was used. Extracted plasmid DNA was subjected to electrophoresis in 0.8% agarose gel and stained with ethidium bromide. Then plasmid bands were visualized under UV. For detection of open circular bands from supercoiled ones, two dimentional electrophoresis and enzyme digestion methods were used. For enzymatic digestion, Eco R1, Hind III, Bam1 and SmaI restriction enzymes were used.
Results: Antibiotic susceptibility and plasmid profiles of 100 E.coli strains isolated from urine of in- and out-patient samples with UTIs were analysed. Ninety nine (99%) of the strains were resistent to ampicillin, but all were sensitive to amikacin. Antibiotic susceptibilities were recorded as 96%, 64%, 57% and 27% against nitrofurantoin, ciprofloxacin, nalidixic acid and co-trimoxazole, respectively. Ten strains (10%) lacked any plasmid and in 90 strains (90%), 1-7 plasmids were detected. Although some strains contained plasmids of >21kb molecular mass, but mainly our isolated plasmids ranged from 0.9 kb to 21 kb. E.coli strains isolated from in-patients revealed to contain more number and larger molecular weight plasmids compared to strains from out-patients. Eighty three (83%) resistant strains to ampicillin had 21 kb plasmid. Fourty four plasmid profiles were obtained from total of 90 plasmid containing strains. When the isolated plasmids were digested using restriction endonucleases, in some cases similar digestion profiles were obtained, and in other cases although the digestion profiles were different, but similar bands were detected.
Conclusion: Our findings suggest plasmid presence in E.coli strains isolated from UTIs in out-patients and in-patients, and there were great similarities in their plasmid profiles. Since these strains had been isolated from various wards in a short period of time, our results raise the possibility of unique source for some strains and high prevalence of genetic exchange among hospital isolates.