Methods:We screened a random sample of 148 uropathogenic E. coli (UPEC) isolates collected from the outpatient department of the Pakistan Institute of Medical Sciences, Islamabad between August 2012 and August 2014 for the O25b-ST131 type using the CH typing method (Weissman et al., 2012). Phylogenetically these isolates were characterized using the triplex PCR method of Clermont et al., 2000.Fluoroquinolone resistance mutations were examined by DNA sequencing of the associated genes gyrA, gyrB, parC and parE.
Results:46% of the isolates were ST131 (n=68); almost half (46%) of the ST131 were sub-clone O25b-ST131 H30-R (n=31). Phylogenetic characterization using the triplex PCR method classified the non-O25b H30-R ST131 as: B1 (5%); B2 (38%); D (57%); and the ST131 O25b H30-R as: A (3%); B1 (6%); B2 (61%); D (30%). By contrast, the non-ST131 were: A (6%); B1 (8%); B2 (35%); D (51%). 40% of all isolates and 97% of the O25b-ST131 were ESBL producers. Most ESBL isolates carried bla CTX-M-15. All ST131 O25b H30-R were resistant to fluoroquinolone, compared to 62% of the non-O25b H30-R ST131, and 61% of the non-ST131. Almost all of the fluoroquinolone resistant E. coli carried two or more non-synonymous mutations in gyrA, parC and parE genes. The sub-clone O25b-ST131 H30-R appeared to have a novel and conserved gyrA/parC/parE allelic combination.
Conclusion:In conclusion, the majority of the multi drug resistant (MDR) isolates in this Pakistani collection were of the ST131 lineage and in phylogroup B2. We observed a greater proportion of ST131 (including the O25b H30-R subgroup) in the phylogroup D lineage than reported previously. A novel gyrA/parC/parE allelic combination in the fluoroquinolone resistant sub-clone O25b-ST131 H30-R appeared in isolates from phyogroups B2 and D.
J. I. Dasti, None
S. E. Graham, None
E. Salzman, None
B. Foxman, None