Abstract

Objectives

The mechanism by which Escherichia coli acquires multidrug resistance genes from other bacteria in the natural environment or livestock is still unclear. The ability of ciliates to promote the transfer of genes encoding extended-spectrum β-lactamases (ESBLs) between the CTX-M-27 donor and clinically isolated recipient E. coli strains was investigated.

Methods

Equal amounts (∼109 cfu) of donor cefotaxime-resistant E. coli and recipient ciprofloxacin-resistant E. coli strains were mixed together in the presence or absence of 105 ciliates in Page's amoeba saline for 24 h, in the presence or absence of certain drugs (cytochalasin D, cycloheximide and latrunculin B).

Results

Gene transfer frequency in the presence of ciliates was estimated at ∼10−6; in the absence of ciliates it was ∼10−10. Protein synthesis (cycloheximide) or phagocytosis (cytochalasin D or latrunculin B) inhibitors significantly reduced the frequency of gene transfer.

Conclusions

Ciliates promote the transfer of genes encoding ESBLs between E. coli strains, implying that the presence of ciliates may provide a significant impact on emerging multidrug-resistant bacteria.

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