Structure-activity relationships related to ceftizoxime (FK 749)

In vitro and in vivo antibacterial activities of CS-807, a new oral cephalosporin

CS-807 is a new oral prodrug of R-3746, a cephalosporin derivative, with potent in vitro and in vivo antibacterial activity against both gram-positive and gram-negative bacteria. The susceptibility of about 1,200 clinical isolates to R-3746 was determined by the agar dilution method. Ninety percent or more of pathogens such as Staphylococcus aureus, streptococci, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, indole-positive and indole-negative Proteus spp., Providencia rettgeri, and Haemophilus influenzae were inhibited at concentrations ranging less than or equal to 0.01 to 1.56 micrograms/ml. Furthermore, at a concentration of 3.13 micrograms/ml, 50% or more of Staphylococcus epidermidis, Morganella morganii, Citrobacter freundii, and Serratia marcescens strains were also inhibited. Pseudomonas aeruginosa and Xanthomonas maltophilia were resistant to R-3746. The activity of R-3746 was scarcely influenced by several growth conditions. R-3746 was highly resistant to hydrolysis by beta-lactamases derived from various species of bacteria. Killing-curve studies demonstrated bactericidal activity of R-3746 at concentrations above the MIC. R-3746 showed high affinity for penicillin-binding proteins 1, 3, and 4 of Staphylococcus aureus and 1A, 1Bs, and 3 of Escherichia coli. Systemic infections in mice caused by various pathogens, including beta-lactamase-producing strains, responded well to therapy with oral doses of CS-807.

Relation of structural properties of beta-lactam antibiotics to antibacterial activity

There has been remarkable progress in the development of new antimicrobial agents as the result of structural modifications of the cephalosporin nucleus. It has been possible to predict many aspects of the antimicrobial activity of new agents and to recognize the structural modifications that contribute to overcoming the continued problem of bacterial resistance. The activity of beta-lactams against gram-positive species depends primarily on their affinity for the enzymes referred to as penicillin-binding proteins. Resistance of gram-positive species to beta-lactams is either due to altered penicillin-binding proteins or, more commonly, due to the presence of beta-lactamases, which are usually plasmid-mediated and inducible. The activity of beta-lactams against gram-negative aerobic and anaerobic bacteria is the result of the way in which the compounds pass through the porin channels in the outer wall, resist inactivation by beta-lactamases, and bind to the penicillin-binding proteins. The basic cephalosporin nucleus consists of the essential beta-lactam ring fused to a dihydrothiazine ring. It is possible to modify this structure to increase antibacterial activity. Changes in moieties at position 3 affect pharmacologic activity but can also cause a marked increase or decrease in activity against staphylococci and Pseudomonas species. The presence of the thiomethyltetrazole group at position 3 has been associated with an alteration in prothrombin synthesis and with disulfiram reactions. Modifications of the cephem nucleus at position 7 by addition of methoxy groups increase beta-lactamase stability but decrease activity against gram-positive species because of lower affinity for penicillin-binding proteins. The more useful acyl side chains have been those that contain a 2-aminothiazolyl moiety, which causes increased affinity of the molecules for penicillin-binding proteins of gram-negative bacteria and streptococcal species. Iminomethoxy groups provide beta-lactamase stability against the common plasmid beta-lactamases such as those of Staphylococcus aureus and the TEM, SHV-1, OXA, and PSE enzymes found in Enterobacteriaceae and Pseudomonas aeruginosa, as well as the chromosomally mediated K-1 and P99 enzymes of Enterobacter. A propylcarboxy group increases beta-lactamases stability and also provides activity against P. aeruginosa and some Acinetobacter. Conversely, this particular grouping reduces the beta-lactamase induction capabilities of a compound, as well as its ability to function as a beta-lactamase inhibitor.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of growth medium on the in vitro activities of second- and third-generation cephalosporins against Streptococcus faecalis

The influence of culture medium of the MICs of eight cephalosporins for 45 strains of Streptococcus faecalis was investigated. The MICs of cephalothin, cefamandole, and cefoperazone were not substantially influenced by the type of culture medium used. In contrast, MICs of cefuroxime, ceftizoxime, cefotaxime, cefmenoxime, and ceftriaxone varied markedly with both the commercial brand and the blood content of the broth used. The use of Mueller-Hinton broths (from Oxoid Ltd., GIBCO Diagnostics, and Difco Laboratories) supplemented with 5% lysed sheep blood frequently resulted in MICs that were greater than or equal to 16 times lower than the MICs obtained with these same broths without blood. Similar, but less marked, patterns were observed when supplemented and unsupplemented brain heart infusion and Sceptor broths were used. The influence of the broth on MICs suggests a complex interaction between some cephalosporins, medium components, and organisms. The cephalosporins that were affected by media share an identical moiety at the 7-acyl position (cefuroxime is slightly different), but this structure is not shared by those cephalosporins that were not affected. This commonality in structure at the 7-acyl position may be partially responsible for the observed results.

In vitro and in vivo antibacterial properties of FK 027, a new orally active cephem antibiotic

FK 027 was more active than cefaclor, cephalexin, and amoxicillin against stock strains of a wide variety of gram-negative bacteria, including such opportunistic pathogens as Citrobacter and Enterobacter species and Serratia marcescens. FK 027 was significantly more active than the three reference drugs against clinical isolates of Escherichia coli, Klebsiella pneumoniae, indole-positive and -negative Proteus species, Providencia species, Haemophilus influenzae, and Neisseria gonorrhoeae. It was less active than cefaclor, cephalexin, and amoxicillin against staphylococci, but it was similar to cefaclor in its activity against streptococci. With few exceptions, FK 027 was active against strains of E. coli, K. pneumoniae, and Proteus mirabilis that were resistant to the reference agents. The bactericidal activity of FK 027 against various gram-negative bacteria, including Proteus species, Citrobacter freundii, Enterobacter aerogenes, and S. marcescens, was greater than that of cefaclor, cephalexin, and amoxicillin. The therapeutic activities of FK 027 in mice infected with gram-negative bacilli were far superior to the activities of cefaclor, cephalexin, and amoxicillin, but they were inferior to the activities of these reference drugs against infection with Staphylococcus aureus.

Ceftizoxime: a beta-lactamase-stable, broad-spectrum cephalosporin. Pharmacokinetics, adverse effects and clinical use

Ceftizoxime is an iminomethoxy aminothiazolyl cephalosporin that inhibits a wide variety of aerobic, anaerobic gram-positive and gram-negative bacteria. The majority of Enterobacteriaceae are inhibited by less than or equal to 1 microgram/ml as are streptococcal species with the exception of Streptococcus faecalis. Staphylococcus aureus are inhibited by 3-8 micrograms/ml, while methicillin-resistant. aureus are resistant. Bacteroides fragilis are inhibited by 16-64 micrograms/ml. It inhibits Pseudomonas aeruginosa at usually achievable concentrations. Ceftizoxime is overall similar in antibacterial activity to cefotaxime and moxalactam. Ceftizoxime is not hydrolyzed by common plasmid and chromosomal beta-lactamases. Serum levels of ceftizoxime after intramuscular and intravenous injection are similar to those of cefotaxime and moxalactam. The half-life is 1.6 to 1.9 hours in normal individuals. The compound is not metabolized and is cleared from the body by glomerular filtration. Ceftizoxime enters most body fluids, including the cerebrospinal fluid, to produce therapeutic concentrations against clinically important bacteria. Ceftizoxime accumulates in the presence of renal failure, but it is removed from the body by hemodialysis and peritoneal dialysis. Ceftizoxime has proved to be an effective chemotherapeutic agent when used as treatment for pneumonia, urinary tract infections, osteomyelitis, septic arthritis, meningitis, peritonitis, gonorrhea, including penicillinase-producing isolates, and gynecological infections. No major adverse reactions have been associated with the use of ceftizoxime and it has produced neither disulfram -like reactions nor bleeding.

In vitro activity and beta-lactamase stability of cefodizime, an aminothiazolyl iminomethoxy cephalosporin

Cefodizime, an iminomethoxy aminothiazolyl cephalosporin similar to moxalactam and ceftazidime, was less active (minimal inhibitory concentration, 1.6 to 12 micrograms) than cefazolin or cefotaxime against Staphylococcus aureus and Staphylococcus epidermidis. It inhibited Haemophilus and Neisseria spp. at less than 0.5 microgram/ml. It did not inhibit methicillin-resistant staphylococci, enterococci, or Listeria spp. and was 8- to 32-fold less active than cefotaxime, moxalactam, or ceftazidime against Escherichia coli, Citrobacter spp., Klebsiella pneumoniae, Providencia spp., and Serratia spp. Cefotaxime-resistant Enterobacter cloacae, Citrobacter freundii, and Proteus vulgaris were resistant to cefodizime. Cefodizime was less active than cefoxitin or moxalactam against Bacteroides fragilis. Cefodizime was not hydrolyzed by common plasmid or chromosomal beta-lactamases, and it inhibited type I beta-lactamases.

Antibacterial activity and beta-lactamase stability of ceftazidime, an aminothiazolyl cephalosporin potentially active against Pseudomonas aeruginosa

The in vitro activity and beta-lactamase stability of ceftazidime were evaluated against 700 gram-positive and gram-negative bacteria. Ceftazidime was less active than penicillins or older cephalosporins against Staphylococcus spp. and Streptococcus spp., and it did not inhibit Streptococcus faecalis, Listeria, or anaerobic species. Ceftazidime was as active as ceftizoxime and moxalactam and more active than cefoperazone against Escherichia coli. Klebsiella, and Proteus mirabilis with minimal inhibitory concentrations of less than 0.2 mg/liter. Ceftazidime also inhibited Enterobacter, Citrobacter, Salmonella, and Shigella at concentrations below 0.2 mg/liter. Most Morganella, Proteus rettgeri, Proteus vulgaris, and Proteus inconstans were inhibited at concentrations below 1 mg/liter, similar to the concentrations for moxalactam, ceftizoxime, and cefotaxime. Ceftazidime was the most active agent tested against Pseudomonas aeruginosa, with a mean minimal inhibitory concentration of 1.6 mg/liter. It inhibited carbenicillin-, piperacillin-, cefoperazone-, and cefsulodin-resistant Pseudomonas. Minimal inhibitory and minimal bactericidal concentrations were similar, with the exception of some Pseudomonas values at 10(7) colony-forming units. Use of different media did not alter minimal inhibitory concentration values. Ceftazidime was not hydrolyzed by staphylococcal beta-lactamase or plasmid beta-lactamase of the TEM-1, TEM-2, SHV-1, OXA-1, PSE-1, PSE-2 types or by inducible beta-lactamases of the cephalosporinase type. Ceftazidime provides an extremely active agent against aerobic and facultative gram-negative bacteria.