Plasmid – mediated Resistance in Salmonella typhi Isolates from Door Handles in Nasarawa State, North-central Nigeria

Contamination of door handles with antibiotic resistant bacteria can be a major threat to public health, as the antibiotic resistant determinants can be transferred to other pathogenic bacteria thus, compromising the treatment of severe bacterial infections. This study investigated the antibiotic susceptibility and plasmid profile of Salmonella typhi isolated from door handles of two tertiary institutions in Nasarawa State, Nigeria. One hundred door handles from each of the two institutions, making 200 in total were sampled and 36(18.00%) S. typhi were isolated. The isolates were 100% resistant to 7 out of the 10 antibiotics tested. Minimum Inhibitory Concentrations (MICs) study on selected multiple antibiotics resistant isolates showed that the isolates were susceptible to the tested antibiotics in the following order: Imipenem = Ciprofloxacin > Ceftazidime > Cefuroxime > Ampicillin > Nitrofurantoin. Fourteen (38.89%) of the multiple antibiotic resistant isolates produced beta lactamase enzymes. Conjugation experiment on the multiple antibiotics resistant S. typhi isolates showed that 7(18.42%) of the test S. typhi isolates transferred resistance plasmid gene to sensitive Proteus mirabilis and the MICs of the recipients increased significantly after conjugation. Plasmid profile of the transconjugants and the donors showed the presence of plasmid of different sizes ranging from 1600 to 2500 base pairs in both donor multiple antibiotics resistant S. typhi and transconjugants P. mirabilis. The transfer of resistant plasmids between bacteria could result in serious epidemics that may be difficult to manage.