Antimicrobial activity, spectrum and pharmacokinetics of old and new orally administered cephems

Comparison of the efficacy and tolerability of once-daily ceftibuten and twice-daily cefprozil in the treatment of children with acute otitis media

In this multicenter, randomized, single (investigator)-masked study, the efficacy and tolerability of once-daily ceftibuten and twice-daily cefprozil were compared in the treatment of acute otitis media in patients 6 months to 10 years of age. Ceftibuten oral suspension 9 mg/kg once daily (maximum dose, 400 mg/d) and cefprozil oral suspension 15 mg/kg twice daily (maximum dose, 1000 mg/d) were given for 10 days. Clinical response, evaluated at the posttreatment visit (days 14 to 16), was rated as clinical cure, improvement, failure, relapse/recurrence, or not assessable. The clinical response was considered successful if the posttreatment assessment was clinical cure or clinical improvement and unsuccessful if the assessment was clinical failure, relapse/recurrence, or not assessable. Tolerability was evaluated by observed and spontaneously reported adverse events. A total of 205 patients were enrolled in the study. The ceftibuten group (51 males, 51 females; mean age, 4.8 years, range, 0.5 to 10.7 years) was similar in demographic characteristics to the cefprozil group (60 males, 43 females; mean age, 4.8 years, range, 0.7 to 10.7 years). In the ceftibuten-treated group, 83.3% (85) of the 102 patients had a successful response compared with 82.5% (85) of the 103 patients in the cefprozil-treated group. The incidence of treatment-related adverse events was similar in both groups, occurring in 5.9% (6) of the ceftibuten-treated patients and 5.8% (6) of the cefprozil-treated patients. Once-daily ceftibuten oral suspension was as effective and well tolerated as twice-daily cefprozil in the treatment of acute otitis media in children. The once-daily dosing schedule for ceftibuten therapy may aid patient compliance, particularly in the pediatric population. Ceftibuten should prove to be a useful alternative in the treatment of acute otitis media.

The antimicrobial activity of cefotaxime: comparative multinational hospital isolate surveys covering 15 years

The "third-generation" cephalosporins (3GC) have emerged as one of the most significant therapeutic entities in the last 15 years. These 3GC compounds (using cefotaxime as a model) have generally maintained their potency and spectrum of activity against important pathogens. However, the continuing popularity of this class associated with local, regional, or national-level use or abuse has led to efficacy reduction against some organism populations associated with selection of Class I cephalosporinase, stably derepressed mutants predominantly among Citrobacter and Enterobacter spp.; emergence of extended-spectrum beta-lactamase producing Enterobacteriaceae (usually Klebsiella spp.), as well as some isolates mimicking Class I-type resistance patterns; and lastly, altered PBP-mediated resistances among pneumococci, Haemophilus influenzae and pathogenic Neisseria spp. Some of these resistance patterns had been present prior to the clinical introduction of 3GCs and have only significantly threatened their use in the last 5 years. Prudent application of these 3GC drugs should be the goal for this decade as follows: 1) use as monotherapy at appropriate doses and frequencies only for organisms with low potential for mutational events; 2) use combination therapy routinely for organisms such as Citrobacter, Enterobacter, some indole-positive protease and Pseudomonas aeruginosa, to minimize emerging resistance clones; 3) use conservatively in high risk patients to minimize "super-colonization" by emerging problem bacteria (e.g. vancomycin-resistant enterococci, Xanthomonas maltophilia etc.); 4) use only those agents among 3GCs that have documented safety, broad clinical applications to all age groups, acceptable pharmacokinetic features and clear cost-saving potential; and 5) use in prophylaxis (surgical procedure, selective decontamination), should be focused toward single-dose or short-course regimens to reduce total hospital-wide exposure to broad-spectrum beta-lactam drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of blood medium supplements on activities of newer cephalosporins tested against enterococci

This comparative study determined the effect of blood on the antienterococcal activities of the newer cephalosporins. Standardized disk diffusion susceptibility tests were performed with 57 strains of enterococci (30 Enterococcus faecalis strains) on Mueller-Hinton agar with and without 5% sheep blood supplementation. Twelve cephalosporins representing five different structural groups (based on the 7-alpha position substitution) were tested. The greatest frequency of activity enhancement by blood was observed with cefdaloxime and cefdinir (7-alpha hydroxyimino group) against E. faecalis. Cephalosporins with a 7-alpha methoxyimino group (cefpodoxime, cefepime, and cefpirome) had marked increases in zone diameters (3 to > 9 mm) when tested with the blood supplement. Cephems with 7-alpha amino or carboxy substitutions did not demonstrate any enhanced activity. Awareness of this phenomenon is important for the interpretation and accuracy of cephalosporin susceptibility testing.

Susceptibility testing interpretive criteria and drug stability for cefdinir, cefetamet, and cefpodoxime against Neisseria gonorrhoeae

Cefdinir, cefetamet, and cefpodoxime, three orally administered cephalosporins, were tested against 100 strains of Neisseria gonorrhoeae having various antimicrobial susceptibility patterns. Triplicate testing of each organism strain was performed for all agar dilution and disk diffusion tests. Cefdinir was the most active compound (MIC90) micrograms/ml) especially against gonococci with chromosomal-mediated resistance to penicillin. The recommended susceptible interpretive criteria were as follows: for the 5-micrograms cefdinir disk, > or = 31 mm (MIC correlate, < or = 0.25 microgram/ml); for the 10-micrograms cefetament disk, > or = 29 mm (MIC correlate, < or = 0.5 microgram/ml; for the 30-micrograms cefetamet disk, > or = 31 mm (MIC correlate, < or = 0.5 microgram/ml); and for the 10-micrograms cefpodoxime disk, > or = 29 mm (MIC correlate, < or = 0.5 microgram/ml). No organisms resistant to these new cephalosporins were detected. Cefdinir, cefetamet, and defpodoxime were stable in GC agar medium for at least 21 days when stored at 2 degrees-5 degrees C.

Cefdinir (FK482), an orally administered cephalosporin in vitro activity comparison against recent clinical isolates from five medical centers and determination of MIC quality control guidelines

Cefdinir, a new oral cephalosporin, was compared to cefaclor, cefadroxil, cefixime, and cefuroxime against greater than 5000 recent aerobic clinical isolates. This multicenter study revealed broad-spectrum cefdinir activity against all Enterobacteriaceae (MIC50s, 0.06-2 micrograms/ml) except Enterobacter cloacae, Morganella morganii, Proteus vulgaris, and Serratia marcescens (MIC50s, greater than or equal to 4 micrograms/ml). Oxacillin-susceptible staphylococci (MIC90s, 0.5-2 micrograms/ml), beta-hemolytic Streptococcus group B (MIC90, 0.06 micrograms/ml), and Acinetobacter lwoffii were also susceptible to cefdinir. The activity of cefdinir was similar to that of cefixime and cefuroxime against Gram-negative organisms and superior to all tested oral cephems when tested against Gram-positive cocci. None of the cephalosporins were active against oxacillin-resistant Staphylococcus spp., enterococci, Pseudomonas spp., or Xanthomonas maltophilia. MIC quality control range guidelines were established for the strains recommended by the National Committee for Clinical Laboratory Standards documents.

Parameters characterizing the in vitro activity of cefixime, a new oral broad spectrum cephalosporin, against respiratory and urinary pathogens

The wide and potent in vitro activity of cefixime, a new oral broad spectrum cephalosporin, has been confirmed on a collection of respiratory and urinary pathogens recently isolated in Italy. The new cephem emerged as the most bactericidal of all the comparators tested against several fast as well as slowly-growing gram-negative species including Enterobacteria, Haemophilus and Moraxella, irrespective of their ability to synthetize beta-lactamases. Among the gram-positive species Streptococcus pyogenes and S. pneumoniae were effectively covered. Cefixime activity was not adversely influenced by several important variables such as pH (over the range from 5 to 8), inoculum size (from 10(5) to 10(8) CFU per ml) and the presence of 50% human serum or urine. Time-kill tests confirmed a pronounced bactericidal potency of the drug especially towards common respiratory pathogens (H. influenzae, M. catarrhalis, S. pneumoniae and S. pyogenes). Killing of urinary strains was optimal at cefixime concentrations reached in urine since eradication, except for Proteus mirabilis, was enhanced with increasing levels of the drug. The absence of an untoward paradoxic effect on the rate of cefixime bactericidal action was confirmed by employing a dynamic bladder model simulating the pharmacokinetic parameters of the drug after a single 200 mg daily dosage. Interactions of cefixime with several other drugs that may be employed in combination therapy were generally prone to provide indifference and synergism while antagonism was never observed. Favorable interactions were also registered when cefixime acted with other antibiotics on partially resistant species such as Staphylococci and Pseudomonas. The new cephem seems to provide excellent opportunities for expanding oral cephalosporin therapy to a wide range of infections produced by susceptible pathogens in the adult and pediatric populations.

Preliminary disk diffusion susceptibility testing criteria for cefdaloxime (RU29246, HR-916 metabolite), a new orally administered cephalosporin

Cefdaloxime (formerly RU29246; Hoechst-Roussel Pharmaceuticals Inc., Somerville, N.J.) a new active component of the HR-916 ester, was tested by dilution and two disk (10- and 30-micrograms) diffusion susceptibility tests against 391 clinical isolates. Interpretive criteria were proposed for three potential MIC breakpoints of less than or equal to 1, less than or equal to 2, and less than or equal to 4 micrograms/ml. Analyses by regression line and error rate bounding methods minimized false-susceptible (very major) errors and produced a greater than or equal to 90% absolute interpretive agreement between susceptibility test methods. The less than or equal to 2-micrograms/ml breakpoint seemed optimal when 10-micrograms disks and the available human pharmacokinetics were used. The following inhibition zone diameter criteria were proposed: susceptible, greater than or equal to 19 mm; resistant, less than or equal to 15 mm. These recommendations for clinical trials should remain tentative until additional information about cefdaloxime formulations, pharmacokinetics, and patient outcomes can be correlated with in vitro susceptibility test results.

Interpretive criteria for disk diffusion tests using 5-microgram cefdinir disks with rapidly growing clinical isolates

Preliminary interpretive zone diameter criteria were calculated for the 5-micrograms cefdinir disk diffusion test by using two potential MIC breakpoints (less than or equal to 0.5 and less than or equal to 1 micrograms/ml). The absolute agreement between tests ranged from 85.9 to 92.4%, and the false-susceptibility errors were principally contributed by the Enterobacter spp. (2.2% error). One proposed criterion was greater than or equal to 20-mm zone diameter (less than or equal to 1 micrograms/ml) for susceptibility and less than or equal to 16-mm zone diameter (greater than 2 micrograms/ml) for resistance to cefdinir. Clinical laboratory users of the disk diffusion method should be cautioned about the possibility of very major interpretive errors among enterobacter isolates.

Antibacterial activity of the investigational oral and parenteral cephalosporin BK-218

BK-218 is a novel cephalosporin with a dual route of administration and spectrum of activity most similar to that of second-generation cephalosporins. BK-218 was active against Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis but strains resistant to penicillins had higher MICs. BK-218 had greater activity (8-fold) than cefuroxime or cefaclor against oxacillin-susceptible Staphylococcus spp. Moderate BK-218 activity was observed against Neisseria gonorrhoeae and commonly isolated Enterobacteriaceae such as Escherichia coli (MIC90, 1 mg/l), Klebsiella spp. (MIC90, 2 mg/l), and Proteus mirabilis (MIC90, 2 mg/l). The following organisms were generally BK-218-resistant (MIC90, greater than 16 mg/l): Bacteroides fragilis, Pseudomonas spp., Acinetobacter spp., Xanthomonas maltophilia, Citrobacter spp., Enterobacter spp., indole-positive Proteus, Serratia spp., enterococci and oxacillin-resistant staphylococci.

In vitro activity of RU29246. The metabolite of a new HR916 cephalosporin ester

Compound RU29246 (RU) is the active metabolite of an orally absorpted cephalosporin ester HR916. The RU spectrum of activity includes the majority of Enterobacteriaceae species, Haemophilus influenzae, pathogenic Neisseria spp., Moraxella catarrhalis, Acinetobacter antiratus, staphylococci, and Streptococcus spp. Pseudomonas species and enterococci were routinely resistant to RU. The RU spectrum was most similar to cefixime against the Gram-negative bacilli and to cefuroxime against the Gram-positive organisms. RU was bactericidal and its mean inhibitory concentrations (MICs) were not greatly increased by high inoculum concentrations. Many strains producing various beta-lactamases generally remained susceptible to RU by MIC tests. However, isolates with extended broad spectrum beta-lactamases capable of hydrolyzing cefotaxime and ceftazidime were also resistant to RU. Broth and agar RU MICs were comparable. Its activity was increased against enterococci in the presence of blood products.

Antimicrobial activity of RU29246 (HR916 metabolite) compared with four other oral beta-lactams tested against more than 5000 clinical isolates

The activity of RU29246, the active metabolite of the oral cephalosporin ester HR916, was compared in a multicenter study with that of the four oral beta-lactam antibiotics cephalexin, cefaclor, cefixime and amoxicillin/clavulanate (amoxicillin/CA). RU29246 was generally 2- to 8-fold more active than the other oral cephalosporins and comparable to amoxicillin/CA against staphylococci, and was the most active cephalosporin against group B streptococci. All four cephalosporins were ineffective against enterococci. RU29246 was the only cephalosporin consistently active against Acinetobacter, but all beta-lactam antibiotics had poor activity against Pseudomonas spp. and Xanthomonas maltophilia. RU29246 was comparable to cefixime and more active than the other cephalosporins against members of the family Enterobacteriaceae. However, all of the antibiotics had poor activity against Enterobacter cloacae and Serratia marcescens. Quality control reference ranges for the quality control organisms Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 are proposed for the broth dilution method based on data derived from this multicenter study.

In vitro activity evaluations of cefdinir (FK482, CI-983, and PD134393). A novel orally administered cephalosporin

Cefdinir, a so-called third-generation oral cephalosporin was tested in vitro against over 700 pathogens from patients with bacteremia. Cefdinir was very active against the Enterobacteriaceae with a 50% minimum inhibitory concentration (MIC50) value range of less than or equal to 0.03-8 micrograms/ml. The enteric species having the highest MIC90S (greater than or equal to 16 micrograms/ml) were Citrobacter freundii, and the enterobacters, Morganella morganii, Proteus vulgaris, and Serratia marcescens. Cefdinir was generally two- to fourfold less active than cefixime, but markedly more potent with a wider spectrum compared with older oral cephalosporins, cefaclor or cefuroxime. In contrast to cefixime, cefdinir inhibited Staphylococcus aureus (MIC90, 1 micrograms/ml) and other staphylococci. Pneumococci, beta-hemolytic streptococci, Haemophilus influenzae, Moraxella catarrhalis, and pathogenic Neisseria spp. (MIC90S, 0.12-0.5 micrograms/ml) were cefdinir susceptible, but Pseudomonas aeruginosa, oxacillin-resistant staphylococci and Bacteroides fragilis gr. strains were resistant. Cefdinir was generally bactericidal with a minimal inoculum effect at 10(6) colony-forming units per spot. Cefdinir beta-lactamase hydrolysis by some recently described extended broad spectrum beta-lactamases was suspected. Cefdinir exhibited a wide, balanced spectrum for an oral cephalosporin indicating possible clinical use against susceptible pathogens in respiratory tract, urinary tract, genital and cutaneous infections.

Antibacterial activity of ceftibuten, a new oral third generation cephalosporin

Ceftibuten, a new oral third generation cephalosporin, was found to be the most active beta-lactam drug tested against members of the Enterobacteriaceae, inhibiting most strains at less than 4 micrograms/ml. All isolates of Branhamella catarrhalis, Haemophilus influenzae, and Neisseria spp. were highly susceptible to ceftibuten. Penicillin-sensitive pneumococci and pathogenic beta-hemolitic streptococci were also killed by ceftibuten. The antibacterial activity of this new drug, which results in rapid lysis of susceptible cells, was not significantly affected by serum, pH, inoculum size, media composition and growth conditions. Ceftibuten is characterized by a remarkable resistance to inactivation by most beta-lactamases synthetized by common gram-positive and gram-negative pathogens. The potent in vitro activity of ceftibuten in conjunction with its favorable pharmacokinetic profile render this new molecule an attractive candidate for the treatment of respiratory and urinary tract infections sustained by susceptible pathogens.

Antimicrobial activity and spectrum of ceftibuten (7432-S, SCH 39720)--a review of United States and Canadian results

Preliminary in vitro studies of ceftibuten in the United States and Canada have demonstrated a potent activity against enteric bacilli (greater than 90% of routine clinical isolates), Haemophilus influenzae, Moraxella catarrhalis, Neisseria spp., most B-hemolytic streptocci, and Streptococcus pneumoniae. Ceftibuten was demonstrated to be bactericidal, minimally influenced by high inocula, beta-lactamase stable, an inhibitor of type Ia beta-lactamase, and potentially usable against some Enterobacteriaceae strains capable of destroying other newer cephalosporins (ceftazidime and cefixime). In vitro test methods have been standardized, and preliminary quality control guidelines have been proposed for clinical trials. The ceftibuten spectrum seems best suited for therapy of urinary tract, respiratory, and genital tract infections as an alternative to older oral cephalosporins, recently marketed esters (cefuroxime axetil), and cefixime.

[Antibacterial activity and beta-lactamase stability of eleven oral cephalosporins]

Oral cephalosporins (cefixime, cefdinir, cefetamet, ceftibuten, cefpodoxime, loracarbef, cefprozil, cefuroxime, cefaclor, cefadroxil and BAY 3522) were compared by their antibacterial profile including stability against new beta-lactamases. Both activity and antibacterial spectrum of compounds structurally related to third generation parenteral cephalosporins (of the oximino class) were superior to established compounds. Activity against staphylococci was found to be highest for cefdinir, cefprozil and BAY 3522. Cefetamet, ceftibuten and cefixime demonstrate no clinically meaningful antistaphylococcal activity while the other compounds investigated demonstrate intermediate activity. The antibacterial spectrum was broadest for cefdinir and cefpodoxime. New oral cephalosporins are equally inactive as established compounds against Enterobacter spp., Morganella, Listeria, Pseudomonas and Acinetobacter spp., methicillin-resistant staphylococci, Enterococcus spp., penicillin-resistant pneumococci and anaerobes. New extended broad-spectrum betalactamases (TEM-3, TEM-5, TEM-6, TEM-7, SHV-2, SHV-3, SHV-4, SHV-5, CMY-1, CMY-2, and CTX-M) are active against the majority of oral cephalosporins. Ceftibuten, cefetamet, cefixime and cefdinir were stable against some of these enzymes even to a higher extent than parenteral cephalosporins. New oral cephalosporins should improve the therapeutic perspectives of oral cephalosporins due to their higher activity against pathogens marginally susceptible to established compounds (higher multiplicity of maximum plasma concentrations over MICs of the pathogens) and furthermore by including in their spectrum organisms resistant to established absorbable cephalosporins (e.g. Proteus spp., Providencia spp., Citrobacter spp., and Serratia spp.).

Current trends and new perspectives in antibiotic therapy

During the last ten years, limitless numbers of antimicrobials were produced by the pharmaceutical industry and some have been marketed. The main objectives of new drugs are to overcome the expanding problems of resistant bacteria, to fill the gaps of spectrum of previous agents. These objectives are progressively reached by new beta-lactams, penems, fluoroquinolones; in general practice, new oral cephalosporins are becoming available. To overcome toxicity problems new concepts in antibiotic usage such as intermittent aminoglycoside regimens are suggested. Research in antibiotics, the discovery of new molecules or the re-evaluation of older drugs constitute dynamic trends in antibiotic therapy.

Antibacterial activity and beta-lactamase stability of MDL 19,592, an oral cephalosporin

We compared the in vitro activity and beta-lactamase stability of MDL 19,592, an orally absorbed cephalosporin, with that of cephalexin and cefaclor. It inhabited Staphylococcus aureus at less than or equal to 4 micrograms/ml, Streptococcus pyogenes at 0.25 microgram/ml, sero groups B, C and G streptococci at 1 microgram/ml, and Streptococcus pneumoniae at 2 micrograms/ml. It was slightly more active than cefaclor and cephalexin. MDL 19,592 did not significantly inhibit Enterobacteriaceae, enterococci, Listeria monocytogenes, Pseudomonas aeruginosa, and Acinetobacter spp. strains (MIC greater than or equal to 32 micrograms/ml). MDL 19,592 was not hydrolyzed by the plasmid beta-lactamases TEM-1 and SHV-1 of Klebsiella but was hydrolyzed by the TEM-3, Staphylococcus aureus beta-lactamase, and the chromosomal-mediated Enterobacter cloacae P99 enzymes.