Effect of Dyes on Multi-drug Resistant S. enterica Harbouring Plasmids

Aim: To determine and compare the antiseptic property of dyes such as acridine orange and ethidium bromide on Multi-drug resistant (MDR) Salmonella enterica in this part of Nigeria.

Study Design: The stool samples of patients with symptoms of enteric fever were isolated and investigated from four hospitals in the south-east region of Nigeria

Place and Duration of Study: The study was carried out in the Department of Microbiology and Biotechnology, Nigerian Institute for Medical Research, Lagos, between August and November, 2012.

Methodology: The 100 S. enterica were recovered using microbact® identification kit-12E. PCR analysis and chromogenic nitrocefin sticks were used to detect isolates with Blactx-M and β-lacatamase enzyme respectively, while alkaline lysis method was adopted for the plasmid extraction. Tube dilutions of the subinhibitory concentration of the dyes and the antibiotics Minimum Inhibitory Concentration [MIC] susceptibility were used to determine the antiseptic effects of the dyes on the isolates.

Results: The S. enterica recovered indicated direct dissemination of these organisms among hospitalized patients and transfers of R-plasmids. Low molecular weight plasmids recovered were 9(9%), 13(13%) of the MDR S. enterica harbored BlaCTX-M gene. Few strains of S. enterica had increased susceptibility to the MIC’s of the antibiotics at 1.25 µg/ml and 0.625 µg/ml of the ethidium bromide dyes, while acridine dyes had reduced effects of the resistant plasmid at 2.50 µg/ml.

Conclusion: These dyes were confirmed to display an antiseptic activity on the resistant plasmid DNA of S. enterica with MDR. There were high significant differences at (p<0.05), in the performance of the selected antibiotics on the MDR S. enterica.