2.5. Transmissibility of resistance
Conjugative matings was carried out in LB broth (Fisher
Scientific Ltd.) between blaCTX-M-14-positive E. coli and the recipient
strain GFP-E. coli HB101 (UA6190) (resistant to gentamicin,
kanamycin and rifampicin) (Mata et al., 2010) in a 1:1 ratio.
Transconjugants were positively selected for blaCTX-M-14 gene and
associated phenotype upon LB agar (Fisher Scientific Ltd., Loughborough,
UK) containing 50 mg/ml rifampicin and 2 mg/ml
cefotaxime. Gene transfer was further confirmed by PCR.
S1-nuclease digestion was used for plasmid characterisation in
positive transconjugants, as described.