Resistance to mecillinam produced by the co-operative action of mutations affecting lipopolysaccharide, spoT, and cya or crp genes of Salmonella typhimurium.
Lipopolysaccharide (LPS), spoT, and cya or crp mutations individually do not affect the minimum inhibitory concentration of mecillinam on Salmonella typhimurium. However, when mutations of two of these types were combined in the same strain, high-level resistance appeared, and increased even further when all three types of mutations were present. Most mutations affecting LPS (rfa, rfb, rfc) showed this behaviour, although to different degrees. The highest resistance to mecillinam was caused by galE and rfc mutations whereas almost no effect was noticed with rfaB or rfaK mutations. This phenomenon appears to be specific for mecillinam since none of several other antibiotics elicited it. Reduction of guanosine tetraphosphate (ppGpp) levels by introduction of a relA mutation did not significantly affect the MIC of mecillinam on strains carrying different combinations of spoT, galE, and cya or crp mutations. All the strains produced spherical cells in medium with a low concentration (0.05 microgram ml-1) of the antibiotic. These results suggest that the antibacterial action of mecillinam on S. typhimurium is somehow dependent on the interaction of LPS, cyclic AMP/cyclic AMP receptor protein (cAMP/CRP), and SpoT. The reported resistance to mecillinam of cya and crp mutants of Escherichia coli K-12 is probably due to the natural LPS defectiveness of this strain.
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Departamento de Radiobiología, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina.
D000262:Adenylyl Cyclases / Q000235:genetics* / Q000502:physiology; D000560:Amdinocillin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000145:classification; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism; D002240:Carbohydrate Sequence; D002352:Carrier Proteins; D003227:Conjugation, Genetic; D002373:Cyclic AMP Receptor Protein / Q000235:genetics* / Q000502:physiology; D006159:Guanosine Tetraphosphate / Q000378:metabolism; D006602:Hexosyltransferases / Q000235:genetics; D008070:Lipopolysaccharides / Q000096:biosynthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011755:Pyrophosphatases / Q000235:genetics* / Q000502:physiology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics / Q000648:ultrastructure; D014534:UDPglucose 4-Epimerase; D018440:beta-Lactam Resistance / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D008070:Lipopolysaccharides; C079397:rfb protein, Bacteria; D006159:Guanosine Tetraphosphate; D006602:Hexosyltransferases; C085652:O-antigen polymerase; C027627:guanosine-3',5'-bis(diphosphate) 3'-pyrophosphatase; D011755:Pyrophosphatases; D000262:Adenylyl Cyclases; D002238:Carbohydrate Epimerases; D014534:UDPglucose 4-Epimerase; C020551:galactose epimerase; D000560:Amdinocillin