Determination of molecular hydrogen in investigations of the susceptibility of Enterobacteriaceae to ampicillin.

One hundred and five enterobacterial isolates from urinary tract infections were examined for ampicillin-susceptibility by measurement of molecular hydrogen production with a palladium metal oxide semi-conductor (Pd-MOS sensor). Eighty-one per cent of hydrogen producing strains could be placed in the same susceptibility groups as recorded by disc-diffusion tests. However, it was harder to separate susceptible from intermediate types than to determine resistance. In all but five strains the hydrogen production allowed determination of viability within 5 h.