We have examined the production of beta-lactamases by 11 clinical and nine
environmental isolates of Plesiomonas shigelloides from Czechoslovakia, the
Czech Republic and Cuba. Ten isolates (50%) expressed detectable amounts o
f a chromosomally encoded, non-inducible beta-lactamase, though all isolate
s showed a broadly similar resistance profile: low-level resistance to ampi
cillin and higher-level resistance to carbenicillin. All strains were susce
ptible to cephalosporins and meropenem. Three clinical isolates expressed a
beta-lactamase similar to a class 2c carbenicillinase, with a pI of 5.2 an
d three expressed an enzyme similar to a class 2d oxacillinase, with a pI o
f 5.3. The environmental isolates produced a variety of penicillinases. Ind
icating that there is a reservoir of heterogeneous beta-lactamase genes in
this species.