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An Escherichia coli strain resistant to a broad spectrum of beta-lactams, including cephamycins, was isolated from a patient suffering from urinary tract infection. A resistance plasmid (pMVP-7) was transferred from the clinical isolate to an Escherichia coli recipient. Both strains produce a cefoxitin-hydrolyzing beta-lactamase focusing at pI 6.7. The phenotype was similar to that of a Klebsiella pneumoniae strain producing cephamycinase FOX-1, so primers were selected from the FOX-1 sequence to amplify the bla gene of the transconjugant. The PCR product obtained was sequenced. The percentage of identity of the deduced amino acid sequence with sequences of other AmpC-type beta-lactamases was 96.9% with FOX-1, 74.9% with CMY-1, and 67.7% with MOX-1. This new plasmid-mediated enzyme is most closely related to FOX-1 (11 amino acid exchanges). We therefore propose the designation FOX-2.

The susceptibility of the new cephamycin antibiotic, cefminox, to hydrolysis by various types of beta-lactamase produced by organisms of the Bacteroides fragilis group was compared with that of cefoxitin. Several enzymes were able to achieve complete hydrolysis of both drugs during overnight incubation, but no marked difference between the rates of inactivation of cefminox and cefoxitin was observed. Susceptibility of the cephamycins to crude extracts of beta-lactamases from the test strains of Bacteroides spp. did not correlate with the results of conventional minimum inhibitory concentration titrations. Possible reasons for these discrepancies are discussed.

The antimicrobial activity of three 7-alpha-methoxy beta-lactams were compared to cefoperazone and ceftriaxone. All had a similar spectrum of activity against the Enterobacteriaceae, except cefoxitin. Cefotetan was only slightly less active than moxalactam against the Enterobacter spp. Ceftriaxone was most effective on Neisserias, Haemophilus spp, nonenterococcal Streptococcus spp, and Acinetobacter spp. Cefoperazone generally inhibited more pseudomonads while all of the "cephamycins" showed activity against Bacteroides fragilis and B. thetaiotaomicron. Beta-lactamase hydrolysis studies of six substrates having pharmacologic serum half lives of greater than or equal to 2 hrs were performed by bioassay and automated procedures. Excellent correlations were found between methods up to 24 hrs. A "lag-phase" was observed for several drug/enzyme combinations before initiation of significant substrate hydrolysis. The 7-alpha-methoxy beta-lactams were routinely more stable to the six representative enzymes (Richmond-Sykes types I-V) than other "stable" cephalosporins. Substrate hydrolysis rates resulting in greater than 50% drug loss in less than or equal to 1 hr generally produced resistant in vitro test results. Cefotetan, cefoxitin, moxalactam, ceftriaxone, and dicloxacillin were potent inhibitors of Type I (P99) beta-lactamases. Moxalactam demonstrated significant inhibition and affinity for the Type V enzyme while cefoperazone uniquely possesses affinity (so-called inhibition) for all tested beta-lactamases. Cefotetan appears to be a promising, beta-lactam compound with some in vitro characteristics comparable to the 1-oxa-beta-lactams and alpha-methoxyimino cephalosporins.

4-Hydroxy-3-methoxymandelic acid and 3,4-dihydroxymandelic acid were found to be potent adjuvants for the rectal absorption of water-soluble compounds in rats. Both adjuvants enhanced the absorption of two cephamycin antibiotics, cefmetazole and cefoxitin. Maximum plasma levels of the antibiotics were obtained within 30 min after rectal administration. The bioavailability of both antibiotics appeared to depend on the concentration of the adjuvant in the microenema, the dosage form used in these experiments. Instead of a microbial assay, a new chemical method involving high-performance liquid chromatography with an ion-pairing technique was developed for analyzing the cephamycin antibiotic plasma levels.

The activity of cefbuperazone, a 7 alpha-methoxy ureido cephalosporin, was determined against 726 clinical isolates. Ninety percent of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter diversus, Proteus mirabilis, Enterobacter aerogenes, Proteus vulgaris, Morganella morganii, Salmonella, and Shigella species were inhibited by less than or equal to 6.3 micrograms/ml. Cefbuperazone was more active than cefamandole, cefoxitin and piperacillin against these species. Concentrations of 25 micrograms/ml of cefbuperazone were needed to inhibit Serratia marcescens and Providencia species, and 50% of Enterobacter cloacae had MICs greater than 25 micrograms/ml. Cefbuperazone was less active by 8 to 32-fold than cefotaxime or moxalactam against most Enterobacteriaceae. Cefbuperazone did not inhibit Acinetobacter or Pseudomonas species. Hemolytic streptococci were inhibited by 12.5 micrograms/ml and staphylococci by 25 micrograms/ml. Cefbuperazone had activity comparable to cefoxitin and moxalactam against Bacteroides fragilis with MIC90s of 6.3 micrograms/ml. Cefbuperazone was not hydrolyzed by plasmid or chromosomal beta-lactamases and was an inhibitor of the P99 E. cloacae beta-lactamase with an I50 of 1 microgram/ml. It was a less effective inhibitor of the K. oxytoca K1 and E. coli TEM-1 beta-lactamases than was clavulanic acid. Cefbuperazone induced beta-lactamases in P. aeruginosa and resistant E. cloacae. A permeability barrier in E. cloacae, C. freundii and P. aeruginosa is suggested by the potentiation of cefbuperazone's activity by EDTA.

The disappearance of phenylalanine and phenylalanylglycine from a perfusate circulated across rat rectal tissue was enhanced significantly in the presence of salicylate or 5-methoxysalicylate at pH 4.5, 7.4, and 8.5. The disappearance of di-, tri-, and tetraphenylalanine from a perfusate at pH 7.4, although facilitated by the presence of salicylate and 5-methoxysalicylate, was also fairly substantial when no adjuvant was present. These peptide analogues of phenylalanine also enhanced the rectal absorption of cefoxitin and cefmetazole, two highly water soluble antibiotics. Phenylalanine and phenylalanylglycine, both poorly absorbed across the rectal membrane when administered alone, did not enhance the rectal absorption of either antibiotic.

Three semisynthetic cephamycin antibiotics (7alpha-methoxy-cephalosporins), SK&F 73678, SK&F 83088 (CS-1170) and cefoxitin, have been found to possess favorable biological and chemotherapeutic properties. All three cephamycins are active in vitro against strains of Staphylococcus aureus and a variety of gram-negative bacilli. Beta-lactamase producing organisms including indole-producing Proteus spp., Enterobacter spp. and Serratia strains as well as certain anaerobic bacteria were found to be susceptible to these antibiotics. SK&F 73768 showed somewhat better MIC values than cefoxitin against multiple strains of bacteria. Strains of Pseudomonas aeruginosa and group D streptococci are essentially insensitive to these compounds. Their binding to serum proteins is relatively low. In mice, cefoxitin showed the most favorable pharmacokinetics with respect to peak serum level, serum half-life and urinary recovery. These cephamycins protected mice experimentally infected with a variety of bacterial strains. All three compounds are rapidly bacteriolytic to the logarithmically growing Escherichia coli and belatedly so to Staphylococcus strains with complete sterilizing effect. SK&F 73678 and SK&F 83088 showed activity and potency comparable to or better than cefoxitin and thus can be considered candidates for clinical study.

Eight strains of the Bacteroides fragilis group that produce unusual beta-lactamases were used to investigate the activity and susceptibility to hydrolysis of cefotetan, a new cephamycin and Sch 34343, a new penem. Cefoxitin and imipenem were also examined for comparison. Antibiotic titrations revealed that cefotetan was less active than cefoxitin against four of the eight strains, and that Sch 34343 was as active or more active than imipenem. Crude enzyme extracts degraded cefotetan more quickly than cefoxitin as judged by high pressure liquid chromatography. Three of the extracts were able to degrade imipenem completely within 1 h and these enzymes degraded Sch 34343 even more rapidly.