Plasmid Profiles of Antibiotic Resistant Bacteria Associated with Biofilms from Ground Water Sources in Ado-Ekiti, Ekiti State, Nigeria

Introduction: The presence of microbial biofilms in our drinking water sources poses a significant health risks to human because biofilm serves as an environmental reservoir of pathogenic microorganisms; the bacteria in biofilms are usually antibiotic resistant and therefore their multiple resistance genes may be harbored on the resistant plasmid.

Aim: The study investigated the plasmid profiles of antibiotic resistant bacteria associated with biofilms from ground water sources in Ado-Ekiti, Ekiti State Nigeria.

Methodology: One hundred samples of water were collected randomly from wells and boreholes, isolation and identification of bacteria from the biofilms of the water samples were carried out by using standard microbiological procedures, antibiotic sensitivity of the isolates was carried out and multiple antibiotic resistant indexes of the bacterial isolates were calculated. The plasmid profiles of the bacterial isolates was also determined.

Results: Results showed that a total of 209 bacteria were isolated from the biofilms of the two ground water sources; these include Streptococcus faecalis, Escherichia coli, Enterobacter aerogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhi and Shigella dysenteriae. S. faecalis from borehole and well water samples had the highest occurrence of (37.5%) and (49.5%) respectively. Shigella dysenteriae had the lowest occurrence of (1.8%) from borehole water while Staphylococcus aureus from well occurred least (2.1%). Both Gram positive and the Gram negative bacterial isolates showed considerable resistance to the different antibiotics. The percentage occurrence of the multiple antibiotic resistant (MAR) bacterial isolates was 106 (52.5%) with the highest percentage (63.4%) from the biofilms of borehole water samples. The MAR indexes of the majority of the bacterial isolates were above 0.2, this revealed a high prevalence of MAR indexes which indicates high risk source of contamination in the study area. Of the 10 MAR isolates selected and examined for plasmid analysis, it was discovered that only six isolates harbored plasmids with molecular size range of 300-950 bp. Plasmid curing and antibiotic sensitivity test after curing showed that curing of plasmids was effective in four isolates (P. vulgaris B11, E. coli W21, Enterobacter aerogenes W25 and Strept. faecalis B25) and partially effective in two isolates (Salmonella typhi B4 and E. coli B37).

Conclusion: Well and borehole water must be treated at the point of use, water storage vessels must be washed regularly and there should be public enlightenment on indiscriminate use of antibiotics in order to eradicate the incidence of antibiotic resistance.