13- Lactam sensitive mutants

The use of p-lactam-sensitive mutants, in combination with p-lacta-mases, allows a certain degree of characterization based on p-lactamase stability. 

Table 7.7. -LACTAMASE PRODUCTION AND SENSITIVITY TO /3-LACTAM ANTIBIOTICS OF MUTANTS OF PS. AERUGINOSA DEFECTIVE IN THE INDUCTION MECHANISM IN COMPARISON WITH THE CORRESPONDING...

Treatment of Ps. aeruginosa strains with mutagens allows variants to be isolated which show an increased sensitivity to /3-lactam antibiotics, despite the presence of the inducible /3-lactamase. The resistance pattern of one such mutant compared with the parent strain is shown in Table 7.10. Evidence suggesting that the mutation is a non-specific permeability mutation is provided by MIC results obtained with the mutant and parent strains against a range of unrelated antibacterial agents (Table 7.11). 

The first report of a specific screening technique designed to search for p-lactam antibiotic-producing cultures was described by Kitano et al. (1975). A mutant of Pseudomonas aeruginosa highly and specifically sensitive to p-lactam antibiotics was isolated. A similar mutant strain of Escherichia coli highly sensitive to p-lactam antibiotics was used in the detection of nocardicins (Aoki et al., 1976). 

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