In vitro activity and beta-lactamase stability of two oral cephalosporins, ceftetrame (Ro 19-5247) and cefetamet (Ro 15-8074)

Stability in the presence of widespread beta-lactamases. A prerequisite for the antibacterial activity of beta-lactam drugs

Bacterial resistance to the beta-lactam drugs is extremely widespread, as a result of extensive drug use. Loss of susceptibility is primarily attributable to hydrolysis by inactivating enzymes, namely the beta-lactamases. While the number of characterised beta-lactamases may exceed 100, only a few are a problem in the treatment of community-acquired infections (TEM-1, TEM-2, SHV-1, BRO-1). Chromosomally mediated and extended-spectrum beta-lactamases are usually dominant in nosocomial pathogens where oral antibiotic therapy is seldom used. Therefore, the threat posed by beta-lactamases must be considered in general practice. Several effective strategies have been implemented in order to overcome beta-lactamase-mediated resistance, e.g. use of non-beta-lactam drugs or beta-lactamase inhibitors. Another option has been the development of new beta-lactam compounds that possess a high intrinsic stability against the hydrolytic action of common beta-lactamases. Among these compounds, the oral third generation cephalosporins represent an important breakthrough. Cefetamet pivoxil, a new oral third generation cephalosporin, is characterised by excellent antimicrobial potency against Enterobacteriaceae, and Moraxella (Branhamella) catarrhalis and Haemophilus influenzae, irrespective of their ability to produce beta-lactamases. The Gram-positive respiratory pathogens, Streptococcus pyogenes and penicillin-susceptible S. pneumoniae, are also satisfactorily covered. The activity of cefetamet has recently been corroborated in a survey conducted in Italy involving 4191 isolates. However, cefetamet shows no activity against enterococci, staphylococci, Listeria, alpha-streptococci, Pseudomonas, Acinetobacter and anaerobes. Given this antibacterial profile, cefetamet pivoxil may provide a useful alternative to other oral antibacterial agents in the empirical therapy of acute community-acquired respiratory and urinary tract infections. From the results of the Italian survey, cefetamet emerged as the only agent among those considered (which included cefuroxime, cefaclor, cefalexin, cefadroxil, ampicillin, amoxicillin/clavulanic acid, ampicillin/sulbactam, doxycycline, erythromycin and clindamycin) that might be selected as the drug of choice in the empirical therapy of outpatient infections.

Parenteral-oral switch in the management of paediatric pneumonia

In phase I of a 2-phase study, 56 evaluable children (0.8 to 5 years) with lobar or segmental pneumonia received intravenous or intramuscular ceftriaxone 50 mg/kg/day for 2 days followed by oral cefetamet pivoxil 20 mg/kg/day in 2 divided doses to complete 7 days of treatment. All patients achieved a clinical cure. In phase II, a randomised open multicentre study, 62 children with pneumonia received an identical regimen to phase I (arm A), and 59 children received ceftriaxone 50 mg/kg/day for 1 day followed by 6 days' treatment with cefetamet pivoxil 20 mg/kg/day (arm B). Patients from phase I and arm A were combined giving a total of 118 evaluable patients in arm A. At the end of treatment, 100% of patients in arm A and 96% in arm B achieved a clinical cure; cure was maintained in 99 and 98% of patients, respectively. Two (4%) patients in arm B failed therapy; in both cases, factors other than treatment failure may have accounted for the poor response. 11 and 12% of patients in treatment arms A and B, respectively, experienced adverse events; gastrointestinal events (nausea and/or vomiting) were reported in 9 and 8% of patients, respectively. In conclusion, 1 or 2 days' treatment with parenteral ceftriaxone before switching to oral cefetamet pivoxil was safe and effective in the treatment of childhood pneumonia. Therefore, parenteral-oral switch is a feasible treatment option in the treatment of serious paediatric community-acquired pneumonia.

Cefetamet pivoxil clinical pharmacokinetics

Cefetamet pivoxil is an orally absorbed prodrug ester of the microbiologically active cephalosporin, cefetamet. The prodrug ester is completely hydrolysed to the active compound cefetamet on its first pass through the gut wall, the liver or both. Cefetamet is classified as a third generation cephalosporin with excellent activity against streptococci, Enterobacteriaceae, Neisseria and Haemophilus species. It has enhanced stability against beta-lactamases compared with penicillins and first and second generation cephalosporins. The antibacterial spectrum is comparable with that of cefotaxime except for its poor activity against staphylococci. Following a 20-minute zero-order intravenous infusion, cefetamet had a rapid distribution phase followed by a monoexponential decline. The average pharmacokinetic parameters from 152 healthy volunteers were: total body clearance 136 ml/min (8.16 L/h); renal clearance 119 ml/min (7.14 L/h); nonrenal clearance 17 ml/min (1.02 L/h); volume of distribution at steady-state 0.29 L/kg; terminal elimination half-life 2.2 hours; 88% of the dose recovered in the urine. Cefetamet is not extensively bound to plasma proteins. Consequently, these data indicate that cefetamet is predominantly eliminated unchanged by the kidney via glomerular filtration with possibly a minor component of tubular secretion. Cefetamet has a relatively small apparent volume of distribution consistent with that of other beta-lactam antibiotics. Results following ascending intravenous doses of cefetamet in healthy young male volunteers demonstrated that the pharmacokinetics of intravenous cefetamet are independent of the dose. The absolute bioavailability of cefetamet tablets following oral cefetamet pivoxil administration is enhanced by the presence of food. Under fed conditions, 50 to 60% of the final oral dose is absorbed into the systemic circulation. This food effect is observed when cefetamet pivoxil is administered within 1 hour of a meal. Food also produces a slight delay in the time to reach peak plasma concentrations of this drug. Changes in fluid volume intake with cefetamet pivoxil administration have no effect on the bioavailability of this drug. Similar absorption characteristics have been observed for all of the tablet dosage formulations studied during clinical development. The absolute bioavailability of the final syrup dosage formulation was between 38 and 47%. Little improvement in the bioavailability of this preparation has been observed with food. The absorption and disposition of cefetamet in human subpopulations [i.e. children, elderly (< 75 years of age), renal impairment, liver disease and patients taking concomitant drugs] have been studied extensively. Only impaired renal function appears to significantly alter the elimination of this drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Cefetamet pivoxil. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefetamet pivoxil is an oral third-generation cephalosporin which is hydrolysed to form the active agent, cefetamet. Cefetamet has excellent in vitro activity against the major respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and group A beta-haemolytic streptococci; it is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis, but has poor activity against penicillin-resistant S. pneumoniae. Cefetamet has marked activity against Neisseria gonorrhoeae and possesses a broad spectrum of activity against Enterobacteriaceae. Both staphylococci and Pseudomonas spp. are resistant to cefetamet. Cefetamet pivoxil has been investigated in the treatment of both upper and lower community-acquired respiratory tract infections and has demonstrated equivalent efficacy to a number of more established agents, namely cefaclor, amoxicillin and cefixime. In patients with group A beta-haemolytic streptococcal pharyngotonsillitis, a 7-day course of cefetamet pivoxil was as effective as a 10-day course of the standard agent, phenoxymethylpenicillin, in this indication. In complicated urinary tract infections, cefetamet pivoxil showed similar efficacy to cefadroxil, cefaclor and cefuroxime axetil. Cefetamet pivoxil was effective in the treatment of otitis media, pneumonia, pharyngotonsillitis and urinary tract infections in children. Preliminary data indicate that single dose cefetamet pivoxil can effectively eradicate N. gonorrhoeae from both men and women. Cefetamet pivoxil has a tolerability profile similar to that of other oral cephalosporins, with gastrointestinal effects being the most commonly reported adverse events. To date, no symptoms of carnitine deficiency have been reported with cefetamet pivoxil. Cefetamet pivoxil offers effective alternative oral therapy for outpatient treatment of community-acquired respiratory tract infections, with the advantage of improved activity against H. influenzae and increased beta-lactamase stability. However, its use in areas with a high incidence of penicillin-resistant S. pneumoniae is likely to be limited. Cefetamet pivoxil is also effective in the treatment of urinary tract infections, although further trials are required to define any comparative advantages over other oral agents.

Comparative antimicrobial activity of ceftibuten against multiply-resistant microorganisms from Belgium

To study the activity of ceftibuten, we obtained multiply-resistant isolates from approximately 20 hospitals in Belgium. Against Enterobacteriaceae, all of the tested comparative compounds were more active than cefaclor, and ceftibuten and tigemonam were the most active of the agents tested. Ceftibuten MIC50s were less than or equal to 1 microgram/ml for most enteric bacilli species and 85% of strains were susceptible (less than or equal to 8 micrograms/ml). This level of activity compared favorably to that recorded for cefaclor (less than or equal to 8 micrograms/ml), cefetamet (less than or equal to 4 micrograms/ml), and cefteram (less than or equal to 1 microgram/ml), that is, 37%, 69%, and 59%, respectively. Ceftibuten, cefetamet, cefteram, and tigemonam were highly active against isolates of Haemophilus influenzae and Neisseria gonorrhoeae. None of the comparative agents were as active as cefaclor against staphylococcal isolates. Against streptococci, cefteram was the most active, and tigemonam the least active of the agents. The MIC90s of ceftibuten for strains of Streptococcus pneumoniae and Streptococcus pyogenes were 2 micrograms/ml and 0.5 microgram/ml, respectively. Strains of Streptococcus agalactiae were resistant to both ceftibuten and tigemonam; cefaclor and cefteram inhibited 100% of isolates of this species. Strains of Enterococcus faecalis and Pseudomonas aeruginosa were consistently resistant to all of the compounds. Overall, ceftibuten exhibited potent activity against many multiply-resistant clinical isolates.

Antimicrobial activity and beta-lactamase stability of BMY-28232, parent compound of an oral cephalosporin

BMY-28232, an aminothiazolyl imino methoxy cephalosporin which is available as an orally absorbed acetoxyethyl ester, inhibited strains of methicillin-susceptible Staphylococcus aureus, hemolytic streptococci, Streptococcus pneumoniae, Escherichia coli, Klebsiella species, and many strains of Proteus and Providencia stuartii at concentrations less than 1 microgram/ml, including isolates resistant to cephalexin and cefaclor. It had activity similar to that of cefixime, but was more active against methicillin-susceptible staphylococci. BMY-28232 was a poor substrate for beta-lactamases but was destroyed by the new TEM-3 enzyme, and had less activity against Enterobacter species, Citrobacter freundii, and Proteus vulgaris isolates. Methicillin-resistant staphylococci, Pseudomonas species, enterococci, Listeria monocytogenes, Corynebacterium jeikeium, Bacteroides fragilus and some strains of Clostridium species were resistant to BMY-28232.

Antimicrobial activity and stability to beta-lactamase of BMY-28271, a new oral cephalosporin ester

BMY-28271, the acetoxyethyl ester of BMY-28232, 7-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3(Z) -propen-1-yl-3- cephem-4-carboxylic acid, is a new oral cephalosporin. BMY-28232 has a widely expanded spectrum with high activity against gram-positive and gram-negative bacteria. BMY-28232 is far more active than cefixime or cefteram against Staphylococcus aureus and Staphylococcus epidermidis. Against gram-negative bacteria, the activity of BMY-28232 was comparable to or somewhat weaker than that of cefixime or cefteram. BMY-28232 was a poor substrate for various beta-lactamases. Orally administered BMY-28271 had a good therapeutic effect on systemic infections with S. aureus and some gram-negative bacteria in mice. Oral BMY-28271 was efficacious against S. aureus Smith infection: the efficacy of BMY-28271 was 80 to 90 times higher than that of cefixime or cefteram.

Comparative in vitro activity and beta-lactamase stability of FK482, a new oral cephalosporin

FK482 is an oral aminothiazolyl hydroxyimino cephalosporin with a C-3 vinyl group. Its activity was compared with those of cephalexin, cefuroxime, cefixime, and amoxicillin-clavulanate. FK482 inhibited 90% of Staphylococcus aureus isolates at 1 micrograms/ml and 90% of Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus pneumoniae isolates at less than or equal to 0.012 micrograms/ml, superior to cephalexin and cefuroxime and similar to cefixime. It did not inhibit oxacillin-resistant S. aureus. FK482 inhibited 90% of Enterococcus faecalis isolates at 8 micrograms/ml. Although 90% of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella species, and Shigella species isolates were inhibited by less than or equal to 2 micrograms/ml, FK482 was less active than cefixime against Citrobacter, Enterobacter, Morganella, Serratia, and Providencia species, with MICs for many isolates of greater than 8 micrograms/ml. FK482 inhibited Haemophilus influenzae and Neisseria gonorrhoeae at concentrations comparable to that of cefixime and superior to those of cephalexin and cfaclor. Bacteroides and Pseudomonas species were resistant. FK482 was not hydrolyzed by the TEM-1 and TEM-2 beta-lactamases but was hydrolyzed by TEM-3 and the Proteus vulgaris enzyme. It had a high affinity for chromosomal beta-lactamases.

In vitro activities of new oral beta-lactams and macrolides against Campylobacter pylori

The in vitro activities of amoxicillin, cefuroxime, ceftetrame, cefetamet, cefixime, tigemonam, erythromycin, roxithromycin, and dirithromycin against 30 clinical isolates of Campylobacter pylori were determined by an agar dilution technique. Roxithromycin and amoxicillin (MICs for 90% of isolates tested, 0.01 and 0.06 micrograms/ml, respectively) were the most active antibiotics tested, but all strains were susceptible to all antimicrobial agents tested.

beta-Lactamase stability and in vitro activity of oral cephalosporins against strains possessing well-characterized mechanisms of resistance

The in vitro activity of four oral cephalosporins was assessed in dilution tests with 50 isolates of the family Enterobacteriaceae possessing well-characterized mechanisms of resistance to beta-lactam antibiotics. The interaction of the drugs with a broad array of beta-lactamases was also determined in spectrophotometric assays and tests for enzyme induction. Overall, the percentages of strains susceptible to each of the study drugs were 82% for cefixime, 62% for cefuroxime, 58% for cephalexin, and 44% for cefaclor. The poor activity of the older cephalosporins was due to a high degree of susceptibility to hydrolysis by both plasmid-mediated and chromosomally mediated beta-lactamases. For cefaclor, higher MICs were associated with higher levels of plasmid-mediated beta-lactamases in the strains. Resistance to cefuroxime was seen primarily among strains expressing high levels of class I or IV beta-lactamase. Resistance to cefixime was seen only among strains expressing high levels of class I enzymes. Neither cefixime nor cefuroxime was a strong inducer of class I beta-lactamases, although enzyme induction did appear to play a role in cefuroxime resistance in a strain of Serratia marcescens. The consistently greater activity of cefixime over cefuroxime was found not to be due to greater drug permeation into the cell. Rather, it appeared to result from the high affinity of the drug for target enzymes.

In vitro antibacterial properties of cefetamet and in vivo activity of its orally absorbable ester derivative, cefetamet pivoxil

The in vitro activity of cefetamet, the microbiologically active metabolite of the orally administered prodrug cefetamet pivoxil, was compared with that of cephalexin, cefaclor, cefuroxime and amoxicillin. Cefetamet was highly active against Enterobacteriaceae, Neisseria spp., Vibrio spp., Haemophilus influenzae and streptococci other than enterococci. Cefetamet inhibited cefaclor-resistant species such as Proteus vulgaris, Providencia stuartii, Providencia rettgeri and Serratia marcescens. Staphylococci, Pseudomonas aeruginosa and cephalosporinase-overproducing strains of Enterobacter cloacae were resistant to cefetamet. The superior activity of cefetamet compared with older oral beta-lactam antibiotics against a large number of gram-negative pathogens correlated with enhanced stability towards beta-lactamases. In accordance with the in vitro findings, cefetamet pivoxil showed good activity in experimental infections in the mouse and rat, suggesting satisfactory bioavailability in these animals after oral administration.

Susceptibility of new beta-lactams to the expanded-spectrum beta-lactamase CTX-1

Forty-three clinical isolates of enterobacteria were selected for the production of the new plasmid-mediated expanded-spectrum beta-lactamase CTX-1. The geometric means of MICs were ranged as follows: ticarcillin, greater than 4096 mg/l; ticarcillin + clavulanic acid (2 mg/l), 64-87 mg/l; LY 163892, 8.0-69.1 mg/l; cefotaxime, 5.7-26.4 mg/l; temocillin, 8.0-21.8 mg/l; Ro 158074, 4.0-18.7 mg/l aztreonam, 1.0-14.4 mg/l and BMY 28142, 1.4-2.8 mg/l. Moxalactam, imipenem and CM 40876 were resistant to hydrolysis and MICs were lower than 2.0 mg/l. A high protective effect on cefotaxime (MIC less than or equal to 0.5 mg/l) was obtained by sulbactam (4 mg/l). Escherichia coli transconjugants from each species showed similar levels of MICs.

In vitro and in vivo antibacterial activities of ME1207, a new oral cephalosporin

ME1207 (pivaloyloxymethyl ester of ME1206) is a new oral cephalosporin. ME1206 is (6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(methoxyimino)- acetamido]-3-[(Z)-2-(4-methylthiazol-5-yl)-ethyl]-cephem-4-carboxy lic acid. The susceptibilities of about 1,600 clinical isolates to ME1206 were determined by the agar dilution method. ME1206 showed a broad spectrum of activity against gram-positive and gram-negative bacteria. ME1206 was more active than cefaclor, T-2525, and cefixime against Staphylococcus aureus and Staphylococcus epidermidis. Against gram-negative bacteria, the activity of ME1206 was comparable with that of T-2525, but ME1206 was less active than cefixime. Against Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria gonorrhoeae, ME1206 had high activity (MIC, less than or equal to 0.05 microgram/ml). ME1206 was stable against various beta-lactamases, except beta-lactamases from Providencia rettgeri, Pseudomonas cepacia, and Escherichia coli W3630 (Rms213). The 50% effective doses of ME1207 after oral administration against systemic infections in mice were comparable with those of T-2588 against gram-negative bacteria and about one-fourth that of T-2588 against Staphylococcus aureus Smith.

Determination of cefetamet and its orally active ester, cefetamet pivoxyl, in biological fluids by high-performance liquid chromatography

Two different, simple and rapid high-performance liquid chromatographic methods with ultraviolet detection, using a common sample work-up procedure, were developed for the determination of cefetamet, an in vitro active cephalosporin, and its orally absorbed pivaloyloxymethyl ester, cefetamet pivoxyl. After protein precipitation with perchloric acid, plasma samples were analysed on C18 reversed-phase columns with 4 mM perchloric acid-acetonitrile (83:17, v/v) and 0.1 M phosphate buffer (pH 6.5)-acetonitrile (60:40, v/v) as mobile phases for the determination of cefetamet and cefetamet pivoxyl, respectively. Urine samples were diluted with water and analysed in the same manner, using 4 mM perchloric acid-acetonitrile (85:15, v/v). The limits of quantification were 0.2, 0.5 and 20 micrograms/ml for the determination of cefetamet and cefetamet pivoxyl in plasma and cefetamet in urine, respectively. The intra-assay precision was less than or equal to 1.5% for cefetamet and less than or equal to 2.3% for cefetamet pivoxyl. The inter-assay precision for cefetamet was less than or equal to 2.4%. Cefetamet was stable in human plasma when stored at -20 degrees C for three months or at 22 degrees C for 24 h. For the determination of cefetamet pivoxyl, which was extremely unstable in plasma (greater than 70% degradation in 1 h), samples were drawn into vacutainers containing citric acid and immediately added to sodium fluoride. The method for cefetamet was successfully applied to several thousand plasma and urine samples from humans, dogs and rats. No unchanged drug could be detected in human or dog plasma after the administration of cefetamet pivoxyl.

Cefetamet pivoxil: bacteriostatic and bactericidal activity of the free acid against 355 gram-negative rods

The in vitro activity of the free acid of cefetamet pivoxil (Ro 15-8075) was tested against 355 clinical isolates, namely enteropathogenic bacteria, glucose non-fermentative gram-negative rods (excluding Pseudomonas aeruginosa) and Legionella pneumophila. Ceftriaxone was included in the study as reference compound. Although the free acid of the orally active cephalosporin was generally weaker than ceftriaxone, it inhibited 88.2% and 94.5% of Enterobacteriaceae and Vibrionaceae at a concentration of 4 mg/l and 8 mg/l or less, respectively. Campylobacter jejuni proved resistant to both compounds. The activity of the new compound against glucose non-fermentative gram-negative rods was generally insufficient to be of promise for broad clinical use. Although the compound was at least twofold more active than ceftriaxone against Pseudomonas acidovorans, Pseudomonas alcaligenes and Pseudomonas cepacia, the former was at least two dilution steps less active than the latter against 14 species of the other less common glucose non-fermentative organisms.

In vitro activity of an oral iminomethoxy aminothiazolyl cephalosporin, R-3746

The in vitro activity of R-3746, an iminomethoxy aminothiazolyl cephalosporin with a CH2OCH3 moiety at position 3, was compared with those of other antibiotics. R-3746 inhibited the majority of hemolytic streptococci (groups A, B, C, F, and G) and Streptococcus pneumoniae at less than 0.06 micrograms/ml, which was comparable to the activity of amoxicillin, 2- to 8-fold more active than cefixime, and 16- to 64-fold more active than cefaclor and cephalexin. Ninety percent of beta-lactamase-producing Haemophilus influenzae and Neisseria gonorrhoeae were inhibited at a concentration 0.25 micrograms/ml, but it was less active against Branhamella spp. It did not inhibit (MIC, greater than 16 micrograms/ml) enterococci, viridans group streptococci, or methicillin-resistant staphylococci. The MICs of R-3746 for 90% of strains tested for Escherichia coli; Klebsiella pneumoniae; Citrobacter diversus; Proteus mirabilis; and Salmonella, Shigella, and Yersinia spp. were less than or equal to 1 micrograms/ml. It was two- to eightfold less active than cefixime but was markedly superior to cefaclor, cephalexin, amoxicillin-clavulanate, and trimethoprimsulfamethoxazole. R-3746 inhibited 50% of Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Morganella spp., Providencia spp., Proteus vulgaris, and Serratia marcescens at less than or equal to 8 micrograms/ml. Pseudomonas spp. were resistant. Fifty percent of Clostridium spp. were inhibited by 0.5 micrograms/ml, but MICs for Bacteroides spp. were greater than 128 micrograms/ml. R-3746 was not appreciably hydrolyzed by most chromosomal and plasmid-mediated beta-lactamases.

BMY-28100, a new oral cephalosporin: antimicrobial activity against nearly 7,000 recent clinical isolates, comparative potency with other oral agents, and activity against beta-lactamase producing isolates

The antimicrobial activity of BMY-28100 was tested against approximately 7,000 bacterial pathogens in a multicenter, multiphased collaborative investigation. The BMY-28100 spectrum and antimicrobial potency was most similar to that of cefaclor and superior to that of cephalexin among currently available cephalosporins. Species that had greater than or equal to 90% of clinical strains inhibited by BMY-28100 (less than or equal to 8.0 micrograms/ml) were: Citrobacter diversus, Escherichia coli, Klebsiella spp., Proteus mirabilis, Salmonella spp., Branhamella catarrhalis, Haemophilus influenzae, Neisseria gonorrhoeae, N. meningitidis, methicillin-susceptible Staphylococcus supp., Streptococcus pneumoniae, S. pyogenes, S. agalactiae, S. bovis, serogroup C and G streptococci, Listeria monocytogenes and gm-positive anaerobes. BMY-28100 inhibited 9% more of the 6286 fresh clinical isolates at less than or equal to 8.0 micrograms/ml than cefaclor at the same concentration. BMY-28100 was generally bactericidal, but MICs for some species were markedly increased when an inoculum concentration of 10(7) CFU/ml was used. Strains producing plasmid-mediated beta-lactamases (TEM, OXA, SHV, HMS) were susceptible to BMY-28100, cefaclor, and cefuroxime. BMY-28100 was less active against strains producing chromosomal-mediated beta-lactamases (Types I and IV). BMY-28100 was not hydrolyzed significantly by the tested plasmid-mediated beta-lactamases, but was destroyed by Type I cephalosporinases and Klebsiella K1 enzymes.

Quantitation of ceftetrame in human plasma and urine by high-performance liquid chromatography

A method is described for quantifying ceftetrame, the acid metabolite of methylene (6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(methoxyimino)acetamido]-3- [(5-methyl-2H-tetrazol-2-yl)-methyl]-8-oxo-5-thia-1-azabicyclo[4.2 .0]oct-2-ene-2-carboxylate pivalate, an orally active cephalosporin. Sodium benzylpenicillin is added to the plasma as the reference standard. The compounds are extracted from plasma or urine using a Bond Elut phenyl column. An aliquot of the methanol eluate is analyzed by high-performance liquid chromatography using a Waters Nova-Pak phenyl column and a UV detector set to 225 nm. The ratios of the peak heights for ceftetrame and sodium benzylpenicillin are calculated and converted to concentrations of analyte with calibration curves that are generated from the analysis of analyte-free plasma or urine fortified with various amounts of ceftetrame and a fixed amount of sodium benzylpenicillin. For plasma, the limit of quantitation for the assay is 0.48 microgram/ml and the inter-assay precision (relative standard deviation) is 9.3%. For urine, the limit of quantitation for the assay is 19.1 micrograms/ml, and the inter-assay precision is 4.9%.

Comparative in vitro activity of the two new oral cephalosporin metabolites RO 19-5247 and RO 15-8074

A total of 629 clinical strains of gram positive and gram negative bacteria were tested for their susceptibility to RO 19-5247, RO 15-8074, and other antimicrobial agents. Both RO 19-5247 and RO 15-8074 had good activity against strains of Enterobacteriaceae; however, resistance was found among some strains of Enterobacter, Citrobacter, Klebsiella and Morganella spp. Both compounds showed moderate to poor active against Acinetobacter spp., Pseudomonas aeruginosa, staphylococci and Streptococcus faecalis. Against strains of Haemophilus influenzae, Neisseria gonorrhoeae, Gardnerella vaginalis, Streptococcus pneumoniae and streptococci (not enterococci), each compound was highly active in vitro. RO 19-5247 and RO 15-8074 had comparable activity to cotrimoxazole, ceftazidime and ceftizoxime. Each new compound had considerably better activity then did cefaclor and amoxicillin/potassium clavulanate.

In vitro activity and beta-lactamase stability of the oral cephalosporin BMY-28100

BMY-28100 was compared with cephalexin, cefaclor, cefixime, and cefteram and found to be more active than the reference cephalosporins against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, and Clostridium difficile. BMY-28100 was the next most active, after cefteram, against Streptococcus pyogenes and Streptococcus pneumoniae. Against gram-negative bacteria, BMY-28100 showed similar activity to that of cefaclor. The antimicrobial activity of BMY-28100, including bactericidal activity, against Staphylococcus aureus was less affected by penicillinase-production than was that of cefaclor. BMY-28100 was more stable than cefaclor against various types of penicillinases, especially against the penicillinase from Staphylococcus aureus.

Preliminary antimicrobial susceptibility interpretive criteria for cefetamet (Ro 15-8074) and cefteram (Ro 19-5247) disk tests

Preliminary interpretive zone criteria were calculated for cefetamet (Ro 15-8074) and cefteram (Ro 19-5247) by using 10- and 30-micrograms disks and three possible MIC susceptibility breakpoints. Absolute interpretive agreement between MICs and zone size criteria ranged from 91.8 to 97.2%. Very major errors (false susceptibility) were less than or equal to 1.2% for both cephalosporin disk tests. Morganella morganii strains appeared to produce the highest rates of very major interpretive errors with cefetamet disks.

Comparative in vitro antibacterial activities of two new oral cephalosporins, ceftetrame (Ro 19-5247) and cefetamet (Ro 15-8074)

The in vitro activities of two new oral cephalosporins, ceftetrame (Ro 19-5247) and cefetamet (Ro 15-8074), were tested against 990 clinical bacterial isolates in comparison with that of cephalexin. Both compounds were more active than cephalexin against gram-negative bacteria, inhibiting most isolates of the family Enterobacteriaceae at concentrations of less than or equal to 4 micrograms/ml, but were not active against Acinetobacter species, most Pseudomonas species, Campylobacter jejuni, and Flavobacterium meningosepticum. Ceftetrame was also more active than cephalexin against most streptococcal isolates and as active as cephalexin against methicillin-susceptible Staphylococcus aureus; against the latter cefetamet was ineffective.