Carbapenem resistance among Enterobacterales has become a global health concern. Clinical
Escherichia coli
isolates producing the metallo β-lactamase NDM have been isolated from two hospitals in Faisalabad, Pakistan. These
E. coli
strains were characterized by MALDI-TOF, PCR, antimicrobial susceptibility testing, XbaI and S1 nuclease pulsed-field gel electrophoresis (PFGE), conjugation assay, DNA hybridization, whole genome sequencing, bioinformatic analysis, and
Galleria mellonella
experiments. Thirty-four
bla
NDM
producing
E. coli
strains were identified among 52 nonduplicate carbapenem-resistant strains. More than 90% of the isolates were found to be multidrug resistant by antimicrobial susceptibility testing. S1 PFGE confirmed the presence of
bla
NDM
gene on plasmids ranging from 40 kbps to 250 kbps, and conjugation assays demonstrated transfer frequencies of
bla
NDM
harboring plasmids ranging from 1.59 × 10
−1
to 6.46 × 10
−8
per donor. Whole genome sequencing analysis revealed
bla
NDM-5
as the prominent NDM subtype with the highest prevalence of
bla
OXA-1
,
bla
CTX-M-15
,
aadA2
,
aac(6')-Ib-cr
, and
tet(A
) associated resistant determinants.
E. coli
sequence types: ST405, ST361, and ST167 were prominent, and plasmid Inc types: FII, FIA, FIB, FIC, X3, R, and Y, were observed among all isolates. The genetic environment of
bla
NDM
region on IncF plasmids included partial IS
Aba125
, the bleomycin
ble
gene, and a class I integron. The virulence genes
terC, traT, gad, fyuA, irp2, capU,
and
sitA
were frequently observed, and
G. mellonella
experiments showed that virulence correlated with the number of virulence determinants. A strong infection control management in the hospital is necessary to check the emergence of carbapenem resistance in Gram-negative bacteria.
IMPORTANCE
We describe a detailed analysis of highly resistant clinical
E. coli
isolates from two tertiary care centers in Pakistan including carbapenem resistance as well as common co-resistance mechanisms. South Asia has a huge problem with highly resistant
E. coli
. However, we find that though these isolates are very difficult to treat they are of low virulence. Thus the Western world has an increasing problem with virulent
E. coli
that are mostly of low antibiotic resistance, whereas, South Asia has an increasing problem with highly resistant
E. coli
that are of low virulence potential. These observations allow us to start to devise methodologies to limit both virulence and resistance and combat problems in developing nations as well as the Western world.