Plasmid Analysis of Resistant Bacteria Isolates from Human Orodental Specimens

Abstract

Background and Objective: Plasmids play a significant role in developing and spreading multidrug resistance genes in nosocomial pathogens, which is becoming a public health challenge. This study analyzed the plasmid of ten multi-drug resistant isolates identified among 163 bacterial strains obtained from human orodental specimens.

Methodology: Isolates were subjected to plasmid content analyses and antibiogram before and after curing using standard agar disc diffusion and agar dilution methods. Plasmid DNA isolation and curing were carried out using standard alkaline lysis method and acridine orange as curing agent, while plasmid profiling of cured and wild strains was done on agarose gel electrophoresis.

Results: The bacterial isolates were multi-drug resistant and 80.0% of them harboured one plasmid with a molecular weight of 10.0 kb.  The observed plasmid DNA was of type 1 colistins plasmids on comparison with plasmid databases. Minimum inhibitory concentrations of test antibiotics against cured isolates were reduced, corresponding to increased antibacterial effect. However, the cured isolates retained resistance to amoxicillin, which indicated a chromosomal amoxicillin resistance.

Conclusion: The presence of plasmid-borne multi-drug resistance gene in human orodental specimen as observed in our study underscores the need for antibiogram, rational antibiotic usage or stewardship to contain the public scourge of multi drug resistant antibiotic phenomenon.