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PubMed1976

High performance liquid chromatography of natural products. I. Separation of cephalosporin C derivatives and cephalosporin antibiotics;isolation of cephalosporin C from fermentation broth.

Microbonded propylamine silica with a solvent system containing acetic acid, methanol, acetonitrile and water (2:4:7.5:86.5) is suitable for an efficient separation of mixtures containing several closely related cephem derivatives. The same system with preparative columns was used for the isolation of cephalosporin C directly from the filtered broth of C. acremonium fermentation.

Acremonium↗
PubMed2006

Immediate allergic reactions to cephalosporins: evaluation of cross-reactivity with a panel of penicillins and cephalosporins.

BACKGROUND: Allergy to cephalosporins has mainly been evaluated in the context of patients with confirmed penicillin allergy. The problem of studying cross-reactivity in subjects primarily sensitized to cephalosporins and potentially allergic to penicillins has not been sufficiently addressed. OBJECTIVE: To evaluate the in vitro IgE response and cross-reactivity to betalactams in patients with immediate allergic reactions to cephalosporins. METHODS: The study included 24 patients with immediate allergic reactions to cephalosporins and RAST-positive to at least 1 cephalosporin. Skin testing and RAST were performed with a panel of penicillins and cephalosporins. RAST inhibition assay with different monomeric conjugates of penicillin and cephalosporin was performed to establish cross-reactivity. RESULTS: The culprit cephalosporins were cefaclor (N = 7), cefonicid (N = 1), cefotaxime (N = 2), ceftazidime (N = 2), ceftriaxone (N = 3), and cefuroxime (N = 9). Two patients had a positive skin test result to penicillin determinants, and 22 patients had a negative result to penicillin determinants and tolerated benzylpenicillin administration. Of these 22, 19 had a positive skin test result to cephalosporins and divided into patients reacting only to the culprit cephalosporin (63.2%) and those reacting to more than 1 cephalosporin (36.8%). RAST and RAST inhibition studies confirmed that the side chain at the R1 position is crucial for recognition. CONCLUSION: The R1 side chain rather than the betalactam structure, shared by penicillins and cephalosporins, seems to play a dominant role in determining the specificity of immunologic reactions to cephalosporins. Thus, penicillin can be administered safely to patients allergic to cephalosporins and with a negative skin test result to penicillin determinants.

Adolescent↗
PubMed2006

Phenotypic and genotypic detection of ESBL mediated cephalosporin resistance in Klebsiella pneumoniae: emergence of high resistance against cefepime, the fourth generation cephalosporin.

OBJECTIVES: Cephalosporins belonging to second and third generation are commonly used in India for the treatment of Klebsiella pneumoniae. Report on resistance among K. pneumoniae strains to second and third generation cephalosporins are on rise in this country, which has been attributed to emergence of strains expressing extended-spectrum beta-lactamases (ESBLs). The aim of this study was to evaluate the in vitro susceptibility of K. pneumoniae to broad-spectrum cephalosporins particularly to cefepime, a recently introduced fourth generation cephalosporin in relation to ESBL production. METHODS: This study has been carried out in two phases among K. pneumoniae strains isolated between October 2001 and September 2002 (phase I, before marketing of cefepime in India) and between August 2003 and July 2004 (phase II, after marketing of cefepime in India). Minimum Inhibitory Concentration (MIC) was determined by a commercial strip containing gradient of antimicrobials (Strip E-test). Detection for ESBL production was carried out by DDST, E-test ESBL and PCR. RESULTS: Antimicrobial resistance profile of K. pneumoniae strains to five cephalosporins as analyzed by WHONET 5 identified 15 different resistance profiles among the 108 phase I isolates, ranging from resistance to none (19.44%) to all the five cephalosporin (8.33%) and eight different resistance profiles among the 99 phase II isolates, ranging from resistance to none (9.1%) to all the five cephalosporins (36.4%). Among the 108 phase I isolates a total of 71 (65.72%) and out of 99 phase II isolates, a total of 87 (88.0%) could be identified as ESBL producers. Among the isolates, regardless of the phase of the isolation, those characterized by production of ESBL showed overall higher frequency of resistance to cephalosporins (range 19.7-85.9% and 51.7-100% in phase I and phase II, respectively) compared to those for ESBL non-producers (range 0-13.5% and 0-25% in phase I and phase II, respectively). Ten randomly selected isolates from the most common resistance phenotypes probably belonged to a single strain as evident by MIC patterns, genotypic characterization and resistance profile to non-cephalosporin group of antimicrobials thereby pointing out the possibility of an outbreak. CONCLUSIONS: PCR may be regarded as a reliable method for detection of ESBL since in addition to the strains that could be identified as ESBL producers by DDST and E-test ESBL; PCR could demonstrate ESBL production among additional 32 strains (15 in phase I and 17 in phase II). Continued uses of cephalosporin group appear to be a potential risk factor for emergence of ESBL producing K. pneumoniae strains. In addition, as noted in the present study, the rise of resistance to cefepime that has been introduced recently in this country for therapeutic use could be of concern.

Anti-Bacterial Agents↗
PubMed1997

Cephalosporin 3'-phloroglucide esters and 7-(phloroglucidamido) cephalosporins as novel antibacterial agents.

Two series of new phloroglucide derivatives were synthesized that possessed antibacterial activities. The first series includes cephalosporin 3'-phloroglucide esters 19 and 20, which were obtained by condensation of cephalosporin 16 with bioactive phloroglucides 14 and 15, respectively. They exhibited a dual mode of antibacterial action. In comparison with cephalosporins 26 and 27, bearing an acetoxy unit at the C-3' position, the bifunctional cephalosporins 19 and 20 showed a broadened spectrum of activity. Results from the consistent valence force field (CVFF) calculations indicate that the most stable conformational isomer of phenolic acid 14, holding a cis-syn-syn geometry, possessed a cavity. It provides an ideal environment to accommodate metal ions of holoenzymes. Phenolic keto acid 15, however, possessed a trans-anti-syn conformation, which allowed chelation between metal ions and the phenolic hydroxyl groups as well as the carbonyl functionalities. Our biological results show that the cavity formed in phloroglucides plays an important role. The second series includes 7-(phloroglucidamido)cephalosporins 24 and 25, which were synthesized by condensation of cephalosporin 21 with 14 and 15, respectively. Results from the CVFF calculations indicate that cephalosporin 24 also possessed a cavity. Unlike cephalosporin 3'-phloroglucide esters 19 and 20, cephalosporins 24 and 25 were found resistant to beta-lactamases from Staphylococcus aureus 95 and Pseudomonas aeruginosa 18S-H. These new compounds, however, showed notable activities against S. aureus FDA 209P, S. aureus 95, Candida albicans, P. aeruginosa 1101-75, and P. aeruginosa 18S-H.

Anti-Bacterial Agents↗
PubMedDate not supplied

Enzymatic modifications of cephalosporins by cephalosporin acylase and other enzymes.

Semisynthetic cephalosporins are important antibacterials in clinical practice. Semisynthetic cephalosporins are manufactured by derivatizing 7-aminocephalosporanic acid (7-ACA) and its desacetylated form. Microbial enzymes such as D-amino acid oxidase, glutaryl-7-ACA acylase and cephalosporin esterase are being used as biocatalysts for the conversion of cephalosporin C (CEPH-C) to 7-ACA and its desacetylated derivatives. Recent developments in the field of enzymatic modifications of cephalosporin with special emphasis on group of enzymes called as cephalosporin acylase is discussed in this review. Aspects related to screening methods, isolation and purification, immobilization, molecular cloning, gene structure and expression and protein engineering of cephalosporin acylases have been covered. Topics pertaining to enzymatic modifications of cephalosporin by D-amino acid oxidase, cephalosporin methoxylase and beta-lactamase are also covered.

Anti-Bacterial Agents↗
PubMed1998

Class restriction of cephalosporin use to control total cephalosporin resistance in nosocomial Klebsiella.

CONTEXT: Resistance to most or all cephalosporin antibiotics in Klebsiella species has developed in many European and North American hospitals during the past 2 decades. OBJECTIVE: To determine if restriction of use of the cephalosporin class of antibiotics would reduce the incidence of patient infection or colonization by cephalosporin-resistant Klebsiella. DESIGN: A before-after comparative 2-year trial. SETTING: A 500-bed, university-affiliated community hospital in Queens, NY. PATIENTS: All adult medical and surgical hospital inpatients. INTERVENTION: A new antibiotic guideline excluded the use of cephalosporins except for pediatric infection, single-dose surgical prophylaxis, acute bacterial meningitis, spontaneous bacterial peritonitis, and outpatient gonococcal infection. All other cephalosporin use required prior approval by the infectious disease section. MAIN OUTCOME MEASURE: Incidence of patient infection or colonization by ceftazidime-resistant Klebsiella during 1995 (control period) compared with 1996 (intervention period). RESULTS: An 80.1% reduction in hospital-wide cephalosporin use occurred in 1996 compared with 1995. This was accompanied by a 44.0% reduction in the incidence of ceftazidime-resistant Klebsiella infection and colonization throughout the medical center (P<.01), a 70.9% reduction within all intensive care units (P<.001), and an 87.5% reduction within the surgical intensive care unit (P<.001). A concomitant 68.7% increase in the incidence of imipenem-resistant Pseudomonas aeruginosa occurred throughout the medical center (P<.01). All such isolates except one were susceptible to other antibiotics. CONCLUSION: Extensive cephalosporin class restriction significantly reduced nosocomial, plasmid-mediated, cephalosporin-resistant Klebsiella infection and colonization. This occurred at the price of increased imipenem resistance in P aeruginosa, which remained susceptible to other agents. Thus, an overall reduction in multiply-resistant pathogens was achieved within 1 year.

Adult↗
PubMed1981

Comparison of the renal excretory mechanisms of cefmenoxime and other cephalosporins: effect of para-aminohippurate on renal clearance and intrarenal distribution of cephalosporins in rabbits.

The renal excretory mechanism of cefmenoxime in rabbits was compared with that of 6 other cephalosporins (cefotaxime, deacetylcefotaxime, cefotiam, cefazolin, cephaloridine, and cefsulodin). The clearance ratios (Cf-Drug/CInulin=CRf) of cefmenoxime (337) and cefazolin (73) were considerably higher than those of the 5 other cephalosporins (0.9-20). When p-amino-hippurate (PAH) was administered concurrently with each of the cephalosporins, the CRf values of the cephalosporins except for cefsulodin were significantly decreased. These findings indicate that cefmenoxime and the 5 other cephalosporins except cefsulodin are actively incorporated in the proximal tubular cells and secreted into the tubular lumen. In the case of cefotiam and cefsulodin, glomerular filtration tended to exceed urinary excretion with highest dose of PAH (40 mg/kg/minute), suggesting the possibility of tubular reabsorption of these drugs. On the other hand, glomerular filtration of cefmenoxime and the 4 other cephalosporins did not exceed urinary excretion. The drug concentration ratio of the cortex to medulla indicated that the tubular cell level of cefmenoxime was lower than, higher than, and similar to those of cephaloridine, cefotaxime, and the remaining cephalosporins, respectively. These results demonstrate that the renal excretory mechanisms of cefmenoxime is similar to that of cefazolin but not to that of the remaining cephalosporins.

Aminohippuric Acids↗
PubMed1992

Studies on condensed-heterocyclic azolium cephalosporins. IV. Synthesis and antibacterial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)- alkoxyiminoacetamido]-3-(condensed-heterocyclic azolium)methyl cephalosporins including SCE-2787.

The synthesis and in vitro antibacterial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-alkoxyiminoacetami do] cephalosporins bearing various condensed-heterocyclic azolium groups at the 3 position in the cephalosporin nucleus are described. The thiadiazolyl cephalosporins showed good antibacterial activity against both Gram-positive and Gram-negative bacteria and the MICs of the thiadiazolyl cephalosporins against Pseudomonas aeruginosa was more potent than that of the corresponding 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-alkoxyiminoacetamido]-3- (condensed-heterocyclic azolium)methyl cephalosporins. Also, the thiadiazolyl cephalosporins bearing (imidazo[1,2-b]-pyridazinium-1-yl)methyl groups at the 3 position showed antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Among the cephalosporins tested, 7 beta-[2-(5- amino-1,2,4-thiadiazol-3-yl)-2(Z)-methoxyiminoacetamido]-3-(imidaz o[1,2- b]pyridazinium-1-yl)methyl-3- cephem-4-carboxylate (4, SCE-2787) which exhibited the most potent antibacterial activity and the broadest antibacterial spectrum was selected as a parenteral cephalosporin candidate for further biological evaluation.

Cephalosporins↗
PubMed1992

Studies on condensed-heterocyclic azolium cephalosporins. V. Synthesis and antibacterial activity of 3-(condensed-triazolo-pyridinium, -pyrimidinium, and -pyridazinium)-methyl cephalosporins.

As a part of our studies on cephalosporins bearing condensed-heterocyclic azolium methyl groups at the 3 position in the cephalosporin nucleus, we describe here the synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)2(Z)-methoxyiminoacetamido] cephalosporins (1-16, 7 beta-[2-(2-amino-5-chlorothiazol-4-yl)-2(Z)- methoxyiminoacetamido] cephalosporins (17,18) and 7 beta-[2-(5-amino- 1,2,4-thiadiazol-3-yl)-2(Z)-methoxyiminoacetamido) cephalosporins (19-23) containing a variety of condensed-heterocyclic triazolium methyl groups at the 3 position in the cephalosporin nucleus. These cephalosporins exhibited potent antibacterial activity, and it appears that condensed-heterocyclic triazolium as well as condensed-heterocyclic imidazolium rings are effective moieties for improving antibacterial activity and the spectrum of activity. Among the cephalosporins tested, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(5- methyl[1,2,3]triazolo-[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (9) and 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(6- methoxy[1,2,4]triazolo[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (11) showed good antibacterial activity.

Cephalosporins↗
PubMed2003

Treatment with a broad-spectrum cephalosporin versus piperacillin-tazobactam and the risk for isolation of broad-spectrum cephalosporin-resistant Enterobacter species.

Receipt of a broad-spectrum cephalosporin is a strong risk factor for isolation of broad-spectrum cephalosporin-resistant Enterobacter species, and yet the risk from other broad-spectrum beta-lactams hydrolyzed by group 1 beta-lactamases has not been well characterized. We compared the risk conferred by broad-spectrum cephalosporins to that conferred by piperacillin-tazobactam, alone or in combination with an aminoglycoside or a fluoroquinolone. A retrospective cohort was monitored from treatment onset until a broad-spectrum cephalosporin-resistant Enterobacter strain was isolated or the patient was discharged. There were 447 patients in the piperacillin-tazobactam group and 2,341 patients in the broad-spectrum cephalosporin group. Groups were similar in age (mean, 62.5 years). The piperacillin-tazobactam group had a smaller percentage of men (32% versus 44%, P < 0.001) and a lower rate of intensive care unit stay (25% versus 38%, P < 0.001) but a higher rate of surgery (41% versus 26%, P < 0.001). Groups differed in the distribution of comorbidities. Resistant Enterobacter strains were isolated from 62 patients, 2% in each group (hazard ratio [RR] = 1.02 [P = 0.95]). In multivariable analysis, risk was similar among treatment groups (RR = 0.71 [P = 0.32]). Intensive care unit stay and surgery were associated with increased risk (RR = 4.53 [P < 0.001] and RR = 1.97 [P = 0.015], respectively), fluoroquinolones were protective (RR = 0.24 [P = 0.003]), and aminoglycosides did not affect risk (RR = 0.98 [P = 0.95]). The protective effect of fluoroquinolones against isolation of broad-spectrum cephalosporin-resistant Enterobacter spp. and the equivalence in risk associated with piperacillin-tazobactam and broad-spectrum cephalosporins may have important clinical and epidemiologic implications.

Anti-Bacterial Agents↗
PubMed1982

Prevention of cephalosporin nephrotoxicity by other cephalosporins and by penicillins without significant inhibition of renal cortical uptake.

Prevention of cephalosporin nephrotoxicity in animal models by probenecid or p-aminohippurate requires treatment regimen that produce sustained inhibition of cortical accumulation of the toxic antibiotic. In contrast, cephaloridine nephrotoxicity in the rabbit can be prevented by a limited single dose of cephalothin. In the present report further studies were done in which it was demonstrated that cephaloridine nephrotoxicity can be prevented by doses of other cephalosporins or penicillins that produce little or no reduction of the cortical concentrations of toxic cephalosporin. More limited studies revealed similar protection by benzylpenicillin against cephaloglycin, also without reduction of cortical concentration. Finally, similar limited-dose administration of penicillin eliminated tha additive toxicity of cefazolin and neomycin. This selective protection against the toxic cephalosporins by the less toxic or nontoxic cephalosporins and by the penicillins, without inhibition of overall cortical accumulation of the toxic antibiotic, may provide a subcellular probe for the study of the molecular basis of cephalosporin nephrotoxicity.

Animals↗
PubMed1988

Mechanism of cephalosporin-induced hypoprothrombinemia: relation to cephalosporin side chain, vitamin K metabolism, and vitamin K status.

The mechanism of cephalosporin-induced hypoprothrombinemia has been investigated in hospitalized patients, with respect to cephalosporin structure, vitamin K metabolism, and vitamin K status. Cephalosporins containing side chains of N-methylthiotetrazole (latamoxef, cefmenoxime, cefoperazone, cefotetan, cefamandole) or methyl-thiadiazole (cefazolin) all caused the transient plasma appearance of vitamin K1 2,3-epoxide in response to a 10-mg intravenous dose of vitamin K1, whereas two cephalosporins without a heterocyclic side chain (cefotaxime and cefoxitin) did not. The plasma accumulation of vitamin K1 2,3-epoxide was qualitatively similar to, but quantitatively less than, that produced by the oral anticoagulant phenprocoumon. Patients eating normally had plasma vitamin K1 concentrations (176 to 1184 pg/mL) that were within the normal range (150 to 1550 pg/mL) and their clotting tests remained consistently normal for all antibiotics tested. Patients on total parenteral nutrition had lower plasma vitamin K1 concentrations (50 to 790 pg/mL) but normal clotting before starting antibiotic therapy. Of 19 parenterally fed patients, all seven treated with latamoxef developed hypoprothrombinemia, PIVKA-II and a decrease of protein C within four days whereas 12 patients treated with cefotaxime or cefoxitin showed no clotting changes. Latamoxef-associated hypoprothrombinemia was readily reversible by 1 mg of vitamin K1 given intravenously, but hypoprothrombinemia and sub-normal plasma vitamin K1 could recur within two to three days. The data suggest that NMTT-cephalosporins are inhibitors of hepatic vitamin K epoxide reductase and that a lower nutritional-vitamin K status predisposes to hypoprothrombinemia.

Adult↗
PubMed2001

Targeted inactivation of the mecB gene, encoding cystathionine-gamma-lyase, shows that the reverse transsulfuration pathway is required for high-level cephalosporin biosynthesis in Acremonium chrysogenum C10 but not for methionine induction of the cephalosporin genes.

Targeted gene disruption efficiency in Acremonium chrysogenum was increased 10-fold by applying the double-marker enrichment technique to this filamentous fungus. Disruption of the mecB gene by the double-marker technique was achieved in 5% of the transformants screened. Mutants T6 and T24, obtained by gene replacement, showed an inactive mecB gene by Southern blot analysis and no cystathionine-gamma-lyase activity. These mutants exhibited lower cephalosporin production than that of the control strain, A. chrysogenum C10, in MDFA medium supplemented with methionine. However, there was no difference in cephalosporin production between parental strain A. chrysogenum C10 and the mutants T6 and T24 in Shen's defined fermentation medium (MDFA) without methionine. These results indicate that the supply of cysteine through the transsulfuration pathway is required for high-level cephalosporin biosynthesis but not for low-level production of this antibiotic in methionine-unsupplemented medium. Therefore, cysteine for cephalosporin biosynthesis in A. chrysogenum derives from the autotrophic (SH(2)) and the reverse transsulfuration pathways. Levels of methionine induction of the cephalosporin biosynthesis gene pcbC were identical in the parental strain and the mecB mutants, indicating that the induction effect is not mediated by cystathionine-gamma-lyase.

Acremonium↗
PubMed1990

Studies on orally active cephalosporin esters. V. A prodrug approach for oral delivery of 3-thiazoliomethyl cephalosporin.

Oral delivery of 3-thiazoliomethyl cephalosporin 1 was attempted through a prodrug approach by applying thiamine chemistry. The 3-thiazoliomethyl group was modified to a ring-opened structure with no ionic charge, and the 4-carboxyl group was converted to pivaloyloxymethyl ester. Lipophilicity of the resulting derivatives (8-10) was suitable for passive absorption from the intestinal tract, and chemical stability in phosphate buffer solution (pH 6.86) was moderate. When administered orally to mice, these derivatives were mainly transformed to a novel 3-spiro cephalosporin 11, and desired reconversion to the 3-thiazoliomethyl cephalosporin was minor. Isomerization to delta 2-cephalosporin 14 was also observed. These results showed that the derivatives (8-10) tested in this study did not serve as orally active prodrugs of 3-thiazoliomethyl cephalosporin 1.

Administration, Oral↗
PubMed1978

Semisynthetic cephalosporins with antifungal activity: laboratory studies on 2-pyridinethiol 1-oxide cephalosporins.

Cephalosporins are chemotherapeutic agents whose spectrum and use are limited to antibacterial activity. Therefore, it was of interest to find several new semisynthetic cephalosporins which possess in vitro antifungal activity against Trichophyton mentagrophytes, Candida albicans and certain other yeasts. Five new cephalosporins containing the 2-pyridinethiol 1-oxide grouping were examined. Four with this heterocyclic moiety in the 3-position were found to have activity. One with the grouping in the 7-acyl-side chain was inactive. The degree of the antifungal activity was influenced by the substituent at the 7-position. The cephalosporin with a p-hydroxyphenylglycyl side chain was the most potent against the fungal strains studied. Despite this in vitro antifungal activity, none of the compounds protected mice against a systemic Candida albicans infection. All of these cephalosporins had broad spectrum in vitro and in vivo antibacterial activity.

Animals↗
PubMed1997

Studies on 3'-quaternary ammonium cephalosporins--III. Synthesis and antibacterial activity of 3'-(3-aminopyrazolium) cephalosporins.

The synthesis and in vitro antibacterial activity of 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]cephalos porins bearing N-mono or dialkyl and carbamoyl aminopyrazolium, and five- or six-membered rings fused to the 3-aminopyrazolium methyl groups at the 3-position, are described. Aminopyrazolium methyl cephalosporins (23e, f, i), with fused saturated and unsaturated rings were especially effective against Staphylococcus strains compared to 3-amino-2-methylpyrazolium methyl cephalosporin (1). Among the cephalosporins prepared in this work, 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3-(4,5, 6, 7-tetrahydro-1-pyrazolo[1,5-a]pyrimidinio)methyl-3-cephem-4-carbox ylate (23f) showed a good balance of antibacterial activity against both Gram-positive bacteria including Staphylococcus aureus and Gram-negative bacteria including P. aeruginosa. An imidazopyrazolium group at the 3-position in, for example, cephalosporin (23i) was particularly effective for improving antibacterial activity against MRSA.

Cephalosporins↗
PubMed1991

Dual-action cephalosporins: cephalosporin 3'-quaternary ammonium quinolones.

When cephalosporins exert their biological activity by reacting with bacterial enzymes, opening of the beta-lactam ring can lead to expulsion of the 3'-substituent. A series of cephalosporins was prepared in which antibacterial quinolones were linked to the 3'-position through a quaternary nitrogen. Like the 3'-ester-linked dual-action cephalosporins reported earlier, these compounds demonstrated a broad spectrum of antibacterial activity derived from cephalosporin-like and quinolone-like components, suggesting a dual mode of action.

Animals↗
PubMed1984

Comparative antibacterial activities of 7 alpha-methoxy cephalosporins and 7 beta-methoxyiminoacetamido cephalosporins against Bacteroides fragilis.

The in vitro antibacterial activities of the newly developed 7 alpha-methoxy cephalosporins and 7 beta-methoxyiminoacetamido cephalosporins against 67 clinical isolates of Bacteroides fragilis and their resistance to the hydrolytic action of a beta-lactamase produced by B. fragilis were simultaneously compared. The minimal inhibitory concentrations that inhibited 90% of the 7 alpha-methoxy cephalosporins, cefoxitin, cefmetazole, moxalactam, and cefotetan, against the isolates were 4, 8, 8, and 16 micrograms/ml, respectively, and these antibiotics were entirely resistant to hydrolysis by beta-lactamases (0.10 mumol/h per mg of protein) of the isolates. By contrast, 7 beta-methoxyiminoacetamido cephalosporins represented by cefotaxime, ceftizoxime, and cefmenoxime were not effective, as indicated by the minimal inhibitory concentrations that inhibited 90%, 64, 32, and 128 micrograms/ml, respectively. Their antibacterial activities clearly corresponded to their resistance to the hydrolytic action of the beta-lactamase: namely, the correlation coefficients in regression curves of cefotaxime, ceftizoxime, and cefmenoxime, which were expressed by the antibacterial activity (x axis) and the beta-lactamase activity (y axis) were 0.098, 0.034, and 0.163, respectively.

Bacteroides fragilis↗