Mechanisms Involved in the Active Secretion of CTX-M-15 β-Lactamase by Pathogenic Escherichia coli ST131

Abstract

Infections caused by antimicrobial resistant bacterial pathogens are fast becoming an important global health issue. Strains of Escherichia coli are common causal agents of urinary tract infection and can carry multiple resistance genes. This includes the gene bla CTX-M-15 that encodes for an extended spectrum beta-lactamase (ESBL). While studying antimicrobial resistance (AMR) in the environment we isolated several strains of E. coli ST131 downstream of a waste water treatment plan (WWTP) in a local river. These isolates were surviving in the river sediment and characterisation proved that a multi-resistant phenotype was evident. Here, we show that E. coli strain 48 (river isolate ST131), provided a protective effect against a third-generation cephalosporin (cefotaxime) for a susceptible E. coli strain 33 (river isolate ST3576) through secretion of a functional ESBL into the growth medium. Furthermore, extracellular ESBL activity was stable for at least 24 h after secretion. Proteomic and molecular genetic analyses identified CTX-M-15 as the major secreted ESBL responsible for the observed protective effect. In contrast to previous studies, outer-membrane vesicles (OMVs) were not the route for CTX-M-15 secretion. Indeed, mutation of the Type I secretion system led to a significant reduction in the growth of the ESBL-producing strain as well as a significantly reduced ability to confer protective effect. We speculate that CTX-M-15 secretion, mediated through active secretion using molecular machinery provides a public goods service by facilitating the survival of otherwise susceptible bacteria in the presence of cefotaxime.

Urban Pigeons (Columba livia) as a Source of Broad-Spectrum β-Lactamase-Producing Escherichia coli in Lisbon, Portugal

“…Indeed, ST131 was present in ESBL-producing E. coli in reservoir water in Singapore [ 29 ], whereas ST10 has been found in antibiotic-resistant Enterobacteriaceae circulating in sewage and aquatic environments in Ireland [ 30 ] and China [ 31 ]. On the other hand, ST3576 has been found in a susceptible E. coli isolate recovered downstream of a wastewater treatment plan in a river in the United Kingdom [ 32 ]. Therefore, our study is consistent with previous studies in which human, animal and environment isolates shared mainly identical STs.…”

Spontaneous Prophage Induction Contributes to the Production of Membrane Vesicles by the Gram-Positive Bacterium Lacticaseibacillus casei BL23

“…Prophage-independent mechanisms of biogenesis have been reported in several Gram-positive bacteria ( 16 – 18 ). Notably, the inhibition of PG synthesis by β-lactam antibiotics was described regarding their role in MV production in Staphylococcus aureus and Lactobacillus casei ATCC 7469 ( 7 , 16 ), as well as in Gram-negative bacteria ( 66 – 68 ). In addition, the role of autolysins in the release of MVs has been proved in Bacillus subtilis and Staphylococcus aureus ( 17 , 18 ).…”

“…The dependency of both PLE3 and PLE1 on prophage PLE2 strongly suggests their satellite nature. Vesicles were shown to play a large number of physiological roles: they are involved in stress resistance, biofilm formation ( 15 , 77 , 78 ), HGT ( 6 , 9 , 79 ), antibiotic ( 66 – 68 , 71 ), and phage resistance ( 80 ). In this context, it will be relevant to further investigate whether the vesicles released after spontaneous and triggered prophage induction promote bacterial resistance to stresses.…”

Gut bacterial extracellular vesicles: important players in regulating intestinal microenvironment

“… 40 A homologous system was also observed in pathogenic E. coli ST131. 59 Horizontal gene transfer (HGT) is a unique mechanism by which bacteria rapidly evolve and adapt to complex environments. In addition to transformation, transduction, and conjugation, GBEVs are often used as a fourth mode of HGT among bacteria.…”