beta-lactamases in Shigella.

The occurrence of resistance and production of beta-lactamases was investigated in 60 Shigella strains. Ampicillin resistance was found in 28 (47%) of the isolates, the resistance being more frequent in Sh. flexneri than in Sh. sonnei. All strains were susceptible to cefotaxime, mecillinam, and ciprofloxacin. The beta-lactamases produced by Shigella were similar to TEM-1, OXA-1, or the low-level chromosomally mediated cephalosporinase produced by Escherichia coli. The beta-lactamases produced by Sh. flexneri were most often the OXA-1-like enzymes.