Within-Host and Population Transmission of bla (OXA-48) in K. pneumoniae and E. coli

During a large hospital outbreak of OXA-48 producing bacteria, most K. pneumoniae (OXA-48) isolates were phenotypically resistant to meropenem or imipenem, whereas most E. coli (OXA-48) isolates were phenotypically susceptible to these antibiotics. In the absence of molecular gene-detection E. coli (OXA-48) could remain undetected, facilitating cross-transmission and horizontal gene transfer of bla (OXA-48). Based on 868 longitudinal molecular microbiological screening results from patients carrying K. pneumoniae (OXA-48) (n = 24), E. coli (OXA-48) (n = 17), or both (n = 40) and mathematical modelling we determined mean durations of colonisation (278 and 225 days for K. pneumoniae (OXA-48) and E. coli (OXA-48), respectively), and horizontal gene transfer rates (0.0091/day from K. pneumoniae to E. coli and 0.0015/day vice versa). Based on these findings the maximum effect of horizontal gene transfer of bla (OXA-48) originating from E. coli (OXA-48) on the basic reproduction number (R (0)) is 1.9%, and it is, therefore, unlikely that phenotypically susceptible E. coli (OXA-48) will contribute significantly to the spread of bla (OXA-48).