The CTX-M-15-Producing Escherichia coli Clone O25b: H4-ST131 Has High Intestine Colonization and Urinary Tract Infection Abilities

Abstract

Increasing numbers of pyelonephritis-associated uropathogenic Escherichia coli (UPEC) are exhibiting high resistance to antibiotic therapy. They include a particular clonal group, the CTX-M-15-producing O25b:H4-ST131 clone, which has been shown to have a high dissemination potential. Here we show that a representative isolate of this E. coli clone, referred to as TN03, has enhanced metabolic capacities, acts as a potent intestine- colonizing strain, and displays the typical features of UPEC strains. In a modified streptomycin-treated mouse model of intestinal colonization where streptomycin was stopped 5 days before inoculation, we show that TN03 outcompetes the commensal E. coli strains K-12 MG1655, IAI1, and ED1a at days 1 and 7. Using an experimental model of ascending UTI in C3H/HeN mice, we then show that TN03 colonized the urinary tract. One week after the transurethral inoculation of the TN03 isolates, the bacterial loads in the bladder and kidneys were significantly greater than those of two other UPEC strains (CFT073 and HT7) belonging to the same B2 phylogenetic group. The differences in bacterial loads did not seem to be directly linked to differences in the inflammatory response, since the intrarenal expression of chemokines and cytokines and the number of polymorphonuclear neutrophils attracted to the site of inflammation was the same in kidneys colonized by TN03, CFT073, or HT7. Lastly, we show that in vitro TN03 has a high maximum growth rate in both complex (Luria-Bertani and human urine) and minimum media. In conclusion, our findings indicate that TN03 is a potent UPEC strain that colonizes the intestinal tract and may persist in the kidneys of infected hosts.

Characterization of Extended-Spectrum-Beta-Lactamase-Producing Escherichia coli Strains Involved in Maternal-Fetal Colonization: Prevalence of E. coli ST131

“…One possible reason for the striking epidemiological success of bla CTX-M-15 and ST131 might be their association. Indeed, the ST131 clone has adapted well to humans (20), and this has contributed to the worldwide dissemination of efficient resistance to third-generation cephalosporins: bla CTX-M-15 . Some studies suggest that clone ST131 is virulent: like other B2 isolates, it killed 100% of experimental mice in another study (36).…”

“…Interestingly, only one other strain, not belonging to the ST131 clone, possessed a putative PAI II J96 -like domain. Clone ST131 might thus have found an optimal balance between virulence, colonization, and resistance (20).…”

“…Allele-specific PCR of the pabB and trpA alleles was used to detect B2 strains belonging to the pandemic clone O25b:H4-ST131 (19). Four strains known to belong to clone ST131 were used as positive controls (e.g., strain TN03 [20]). …”

Escherichia coli ST131, an Intriguing Clonal Group

“…Vimont et al investigated the capacity of the tested ST131 isolate to colonize the digestive tract by measuring its maximal growth rate (MGR) under three sets of culture conditions: a rich medium and two min-imal media containing either gluconate or glucose. They compared the results obtained with those for the commensal E. coli strain K-12 MG1655 and two ExPEC strains, CFT073 and HT7 (127). The ST131 strain had a significantly higher MGR than the other three strains.…”

CTX-M-32 beta-lactamase-producing uropathogenic Escherichia coli isolated in Latin America

“…Beta-lactam antibiotics have been widely used to treat UPEC infections; however, extended-spectrum beta-lactamases (ESBLs) create significant therapeutic problems by inactivating almost all beta-lactams except cephamycins and carbapenems [1,2]. The CTX-M-type beta-lactamases are members of a lineage of ESBLs currently recognized as the most widespread worldwide, both in clinical and community settings.…”