Pseudomonas aeruginosa beta-lactamases.

Forty recently isolated hospital strains of Pseudomonas aeruginosa were assayed to determine the part played by the production of beta-lactamase in their resistance to beta-lactamic antibiotics, together with the relative importance of constitutive and inducible enzymes in such resistance in the case of carbenicillin (CB). 62.5% were CB-resistant. In 56% of cases, this resistance was due to the production of a class Vd constitutive enzyme, whereas it was ascribable to intrinsic resistance in the other 44%.