Rapid identification of Escherichia coli transformed by pBR322 carrying inserts at the PstI site

Rapid Method for Screening Large Numbers of Escherichia coli Colonies for Production of Plasmid-Mediated β-Lactamases

“…For a variety of plasmids and bacterial hosts, storage of agar plates containing colonies at 4°C for hours to weeks before assay had no effect on results. DISCUSSION Several methods have been developed in the past for rapid scoring of antibiotic resistance by color change in large numbers of individual bacterial colonies while still on an agar surface (1,4,18,19,(21)(22)(23). These methods have relied, for the most part, on ,-lactamases, for which three types of assays have been described: penicillin and starch-iodine, penicillin and pH indicator dye, and chromogenic cephalosporin.…”

“…These methods have relied, for the most part, on ,-lactamases, for which three types of assays have been described: penicillin and starch-iodine, penicillin and pH indicator dye, and chromogenic cephalosporin. With the penicillin and starch-iodine assay, presence of 1-lactamase in a colony is shown by decolorization of a blue starch-iodine complex when penicilloic acid, a cleavage product of penicillin, reacts with iodine (1,4,22). With the pH method, the production of penicilloic acid from penicillin lowers pH, a change detected by use of a pH indicator dye such as N-phenyl-1-naphylamine-azo-o-carboxybenzene (18,19).…”

“…Ordinarily, bacterial colonies are screened for loss of antibiotic resistance by replica plating, a reliable but time-consuming technique when large numbers of colonies are to be scored. Alternative methods have been developed in the past to allow assessment of antibiotic resistance in large numbers of individual colonies on an agar surface (1,4,18,19,(21)(22)(23). Such methods have, for the most part, assayed for the presence of ,B-lactamases (1,4,18,19,21,22), enzymes that inactivate penicillin, or, more recently, for the presence of an enzyme that acetylates chloramphenicol (23).…”

“…Alternative methods have been developed in the past to allow assessment of antibiotic resistance in large numbers of individual colonies on an agar surface (1,4,18,19,(21)(22)(23). Such methods have, for the most part, assayed for the presence of ,B-lactamases (1,4,18,19,21,22), enzymes that inactivate penicillin, or, more recently, for the presence of an enzyme that acetylates chloramphenicol (23). We describe an assay in which filter paper strips impregnated with benzylpenicillin and the pH indicator dye bromocresol purple are used and that allows screening of large numbers of Escherichia coli colonies for the presence of 3-lactamase.…”

Methylation-dependent transcription controls plasmid replication of the CloDF13 cop-1(Ts) mutant

“…Plasmid pGB210 was constructed by inserting a 0.4-kb chromosomal E. coli DNA fragment into the PstI site of plasmid pPA153-209. Ampicillin-susceptible transformants were selected by the method of Boyko et al (6). Plasmid pDAMA was constructed by deleting the 0.5-kb BamHI-BamHI fragment from plasmid pDAM118.…”