A Dissertation Submitted in Partial Fulfillment of the Requirement for the Degree of
Master’s in Life Sciences of the Nelson Mandela African Institution of Science and
Technology
Globally, blaCTX-M-15 beta-lactamases are the most popular extended spectrum beta-lactamase
alleles that are widely distributed due its mobilization 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. 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. Escherichia coli was recovered from majority of isolates. 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. 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