@article{mbs:/content/journal/micro/10.1099/00221287-48-3-449, author = "O'Callaghan, Cynthia H. and Muggleton, P. W.", title = "The Action of Cephaloridine with Cloxacillin or Methicillin against °bT-Lactamase-Producing Gram-negative Bacteria", journal= "Microbiology", year = "1967", volume = "48", number = "3", pages = "449-460", doi = "https://doi.org/10.1099/00221287-48-3-449", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-48-3-449", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "SUMMARY: Cephaloridine has a broad spectrum of antibacterial activity, but certain Gram-negative organisms (e.g. Aerobacter aerogenes, Proteus morgani) are resistant by reason of their ability to destroy the antibiotic. Methicillin and cloxacillin do not inhibit Gram-negative organisms but are resistant to the βbT-lactamases which some strains produce and can protect cephaloridine from destruction by such enzymes. This protection effect towards cephaloridine has been demonstrated in vitro and on experimentally infected mice. In vitro, a relatively small proportion of the penicillin exerted a maximal protecting effect towards cephalosporin and enhanced its bactericidal action against the Gram-negative organisms which produce °bT-lactamase. The clinical use of a combination of cloxacillin or methicillin with cephaloridine for the treatment of intractable systemic infections with °bT-lactamase-producing Gram-negative organisms is suggested, even though laboratory tests may show the organisms to be resistant to both cephaloridine and the penicillins when they are tested separately.", }