Molecular characterization of metronidazole resistant Bacteroides strains from Kuwait

Eleven metronidazole resistant Bacteroides and one newly classified Phocaeicola dorei strain from Kuwait were investigated for their resistance mechanisms and the emergence of their resistant plasmids. All but one strain harbored nimE genes on differently sized plasmids. Of the 11 nimE genes, 9 were preceded by full copies of the prototype ISBf6 insertion sequence element, one carried a truncated ISBf6 and one was activated by an additional copy of IS612B. Nucleotide sequencing results showed that the nimE ISBf6 distances were constant and all five different plasmids shared a common region, suggesting that (i) the nimE-ISBf6 configuration was inserted into an undisclosed common genetic element, (ii) over time, this common element was mutated by insertions and deletions, spreading the resultant plasmids. Of the 10 B. fragilis strains in this collection, 6 were also cfiA-positive, one with full imipenem resistance, indicating a tendency for multidrug resistance (MDR) among such isolates. The significant number of metronidazole resistant Bacteroides spp. and P. dorei strains with the MDR phenotype warns of difficulties in treatment and suggests promoting adherence to antibiotic stewardship recommendations in Kuwait.