Abstract
Background: Globally, blaCTX-M-15 beta-lactamases are the most popular extended spectrum beta-lactamase alleles that are widely distributed due its mobilisation by mobile genetic elements in several compartments. We aimed to determine the conjugation frequencies and replicon types associated with plasmids carrying blaCTX-M-15 gene from Extended Spectrum Beta-lactamase producing isolates in order to understand the dissemination of resistance genes in different compartments. Material and methods: A total of 51 archived isolates carrying blaCTX-M-15 beta-lactamases were used as donors in this study. Antibiotic susceptibility tests were performed as previously described for both donors and transconjugants. Conjugation experiment was performed by a modified protocol of the plate mating experiment, and plasmid replicon types were screened among donor and transconjugant isolates by multiplex Polymerase Chain Reaction in a set of three primer panels. Results: The conjugation efficiency of plasmids carrying blaCTX-M-15 was 88.2% (45/51) with conjugation frequencies in the order of 10−1 to 10−9 and a 100% transfer efficiency observed among E. coli of animal origin. Majority of donors (n = 21) and transconjugants (n = 14) plasmids were typed as either Inc FIA or Inc FIB. Resistance to non-beta-lactam antibiotics was transferrable in 34/45 (75.6%) of events. Ciprofloxacin, tetracycline and sulphamethoxazole-trimethoprim resistance was co-transferred in 29/34 (85.3%) such events. Gentamicin resistance was transferred in 17/34 (50%) of events. Conclusions: Majority of plasmids carrying blaCTX-M-15 were conjugatively transferred by IncF plasmids along with non-beta lactam resistance. There is a need for more research on plasmids to understand how plasmids especially multi replicon plasmids interact and the effect of such interaction on conjugation. One Health approach is to be intensified to address antimicrobial resistance which is a public health threat.
Highlights
The increasing trend of antimicrobial resistance is intensified by mobile genetic elements that harbour resistance genes [1]
extended-spectrum beta-lactamases (ESBL) enzymes are chromosomally mediated by the selection pressure induced by beta-lactamase-producing soil organisms [6,7] or the irrational use of third-generation cephalosporins [6,8], as previously reviewed [9], plasmidmediated ESBL resulted from transposon-mediated insertion of different blaCTX-M genes in bacteria chromosome
The precursors of plasmid-mediated blaCTX-M-15 are environmental Kluyvera spp. whose chromosomal CTX-M clusters are incorporated into the chromosome of host bacteria by mobilising elements such as ISEcp1 or ISCR1
Summary
The increasing trend of antimicrobial resistance is intensified by mobile genetic elements that harbour resistance genes [1] The effect of these elements is extensively reported among bacteria of the Enterobacteriaceae family where multi drug resistance (MDR) is high. The mobilisation potential of ISEcp for chromosome-linked multi-resistant determinants in other members of enterobacteriaceae increases with the additional possession of ISCR1, another mobile genetic element (MGE) embedded in a Class 1 integron that mobilises unrelated CTX-M groups in similar or different species. We aimed to determine the conjugation frequencies and replicon types associated with plasmids carrying blaCTX-M-15 gene from Extended Spectrum Beta-lactamase producing isolates in order to understand the dissemination of resistance genes in different compartments. Conclusions: Majority of plasmids carrying blaCTX-M-15 were conjugatively transferred by IncF plasmids along with non-beta lactam resistance.
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