Comparison of glycine enhancement with cefoxitin induction of Class 1 β-lactamase production in Enterobacter cloacae ATCC 13047

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Abstract
The presence of either glycine or cefoxitin in the growth medium resulted in an increase in the β-lactamase activity of cultures of Enterobacter cloacae ATCC 13047. Although the β-lactamases produced as a result of either glycine enhancement or cefoxitin induction were identical there were striking differences in the kinetics of β-lactamase production. The increased production of β-lactamase which resulted from enhancement by glycine occurred late in the growth cycle whereas, with cefoxitin induction, the maximum production of β-lactamase occurred early in logarithmicphase growth. After the peak activity was reached the β-lactamase activity appeared to decline with both processes. However, the mechanism of the apparent fall in the intracellular β-lactamase activity was different with glycine enhancement and cefoxitin induction. In glycine enhanced cultures the fall presumably was due to leakage of intracellular β-lactamase into the culture medium whereas with cefoxitin induced cultures there was dilution of β-lactamase activity by bacterial protein derived from an increase in cell numbers after the cessation of induction. High extra-cellular levels of β-lactamase activity were observed in cultures enhanced by glycine, whereas little β-lactamase activity was detected in the medium when the cultures were induced by cefoxitin. The findings demonstrate that there are considerable differences between glycine enhancement and cefoxitin induction, but a final mechanism common to both processes exists which results in the production of identical β-lactamases by E. cloacae ATCC 13047.