Plasmid Replicon Typing of Antibiotic-Resistant Escherichia coli From Clams and Marine Sediments

Abstract

Unlike human isolates, environmental Escherichia coli isolates have not been thoroughly investigated for the diversity and transferability of antibiotic-resistant plasmids. In this study, antibiotic-resistant strains from marine sediment (n = 50) and clams (n = 53) were analyzed (i) for their plasmid content using a PCR-based plasmid replicon typing (PBRT) kit and (ii) for the transferability of plasmid-associated antibiotic resistance (AR) traits by mating experiments. Fifteen of the thirty replicons targeted by the PBRT kit were detected in the isolates; 8/15 were identified in both sediment and clam isolates, although at different frequencies. The most frequent replicons in sediment (74%) and in clam strains (66%) alike, were FIA, FIB, or FII, which are associated with the IncF group, followed by the I1α replicon, which was more frequent in clam (24.5%) than in sediment (10%) strains. More than 50% of the strains contained multiple replicons; although 15 were untypable, S1-PFGE analysis demonstrated that 14/15 carried no plasmids. All cryptic strains were successfully typed and were positive for IncF or IncI replicons. Antibiotic-resistant strains accounted for 63% of all isolates and were significantly (p < 0.05) more frequent in phylogroup A. Most (35%) multidrug-resistant (MDR) strains belonged to phylogroup A, too. Although 25/26 MDR strains were positive for IncF plasmids (the exception being a clam strain), the FII-FIB rep combination was predominant (63%) among the sediment isolates, whereas most clam isolates (40%) carried the FII replicon alone. In mating experiments, selected MDR strains carrying FIB, FII, and I1α replicons, used as the donors, transferred multiple ARs together with the IncF or IncI plasmids at high frequency. Since IncI plasmids are common in E. coli and Salmonella enterica isolates from poultry, our findings suggest an animal origin to the E. coli clam strains carrying IncI plasmids. They also suggest a role for IncI plasmids in the spread of ARs among environmental Enterobacteriaceae and, through the food chain, to human isolates. In conclusion, the PBRT kit proved to be a useful tool to identify plasmids carrying antibiotic-resistant genes and to shed light on the factors underpinning their diffusion.

Elucidating the resistance repertoire, biofilm production, and phylogenetic characteristics of multidrug‐resistant Escherichia coli isolated from community ponds: A study from West Bengal, India

“…This study detected rich plasmid pool in MDR isolates capable of conjugating to different bacterial hosts. The predominance of plasmid replicon groups like IncF (Frep, FIA, and FIB subgroups), IncI1, IncY was reported from environmental sources including water sediments (Citterio et al, 2020). Plasmid types like IncI, IncF and IncY with multiple antibiotic determinants are known to predominate in specific geographic areas and can amplify in a variety of hosts depending upon the antibiotic pressure.…”

Function Characterization of Endogenous Plasmids in Cronobacter sakazakii and Identification of p-Coumaric Acid as Plasmid-Curing Agent

“…Alternatively, molecular biology methods based on plasmid incompatibility involve the construction of plasmids containing replicons to cure endogenous plasmids, which primarily rely on the accurate cloning of the replicon from endogenous plasmids (Buckner et al, 2018). However, this method is subject to the prediction of plasmid incompatibility, and the multiple replicons that are frequently present in endogenous plasmids can further restrict the applicability of the plasmid incompatibility-based method (Citterio et al, 2020). Another traditional approach uses transposons harboring the sacB or rpsL genes to cure various plasmids that were established decades ago.…”

The Emerging Nosocomial Pathogen Klebsiella michiganensis : Genetic Analysis of a KPC-3 Producing Strain Isolated from Venus Clam

“…K. michiganensis isolates have also been recovered from wastewaters ( 9 , 10 ), suggesting that coastal areas receiving urban and hospital effluents could represent potential sources of infections for humans. In central Italy, along the coast of the Adriatic Sea, Escherichia coli epidemic clones of human origin have been isolated from waters, sediments, and mollusks ( 11 – 13 ). Bivalves have the potential to concentrate microorganisms as a consequence of their filter-feeding activity.…”