Long-term adaptation of ParA, RelE/ParE partition system, replication protein and phage proteins encoding low-cost plasmids of Escherichia species isolated from diarrheic children of North East India.

AIMS

The prevalent distribution of plasmid-mediated β-lactam resistance is the most pressing global problem in enteric diseases. The current work aims to characterize plasmid-carrying β-lactam resistant Enterobacteriaceae isolates from North East India for horizontal gene transfer (HGT) and plasmid adaptation study.

METHODS AND RESULTS

In vitro transconjugation and transformation showed overall high conjugation frequency (4.11 × 10-1-9.2 × 10-1) and moderate transformation efficiency/µg DNA (1.02 × 102 -1 × 103), and the highest conjugation frequency (9.2 × 10-1) and transformation efficiency (1 × 103) for Escherichia species S-10. Intra/intergenus plasmid transformation efficiency was highest for the transformation of Klebsiella pneumoniae S-2 to Shigellaflexneri S-42 (1.3 × 103) and lowest for Escherichia species S-10 to Escherichia fergusonii S-30 (2 × 102). In the plasmid stability test, S-10 was detected with the highest plasmid carrying frequency (83.44%) and insignificant segregational loss rate (0.0004) until the 60th day with low plasmid cost on the host. The above findings were also validated by whole-plasmid sequencing of Escherichia species S-10. The genome was identified with two plasmids constituting multiple phage proteins, relaxosomal protein NikA, replication protein RepA, and the plasmid maintenance proteins (ParA, RelE/ParE), thus assisting stable plasmid maintenance.

CONCLUSIONS

The results thus indicate that the high conjugation ability and low plasmid fitness cost might lead to horizontal gene transfer of the plasmid to the environment due to their prolonged adaptation in nonselective conditions, intensifying the infection's severity.