Comparison of in vitro activity of cephalexin, cephradine, and cefaclor

DprA from Neisseria meningitidis: properties and role in natural competence for transformation

DNA processing chain A (DprA) is a DNA-binding protein that is ubiquitous in bacteria and expressed in some archaea. DprA is active in many bacterial species that are competent for transformation of DNA, but its role in Neisseriameningitidis (Nm) is not well characterized. An Nm mutant lacking DprA was constructed, and the phenotypes of the wild-type and ΔdprA mutant were compared. The salient feature of the phenotype of dprA null cells is the total lack of competence for genetic transformation shown by all of the donor DNA substrates tested in this study. Here, Nm wild-type and dprA null cells appeared to be equally resistant to genotoxic stress. The gene encoding DprA_Nm was cloned and overexpressed, and the biological activities of DprA_Nm were further investigated. DprA_Nm binds ssDNA more strongly than dsDNA, but lacks DNA uptake sequence-specific DNA binding. DprA_Nm dimerization and interaction with the C-terminal part of the single-stranded binding protein SSB_Nmwere demonstrated. dprA is co-expressed with smg, a downstream gene of unknown function, and the gene encoding topoisomerase 1, topA.

Characterization of the Neisseria meningitidis Helicase RecG

Neisseria meningitidis (Nm) is a Gram-negative oral commensal that opportunistically can cause septicaemia and/or meningitis. Here, we overexpressed, purified and characterized the Nm DNA repair/recombination helicase RecG (RecG_Nm) and examined its role during genotoxic stress. RecG_Nm possessed ATP-dependent DNA binding and unwinding activities in vitro on a variety of DNA model substrates including a Holliday junction (HJ). Database searching of the Nm genomes identified 49 single nucleotide polymorphisms (SNPs) in the recG_Nm including 37 non-synonymous SNPs (nsSNPs), and 7 of the nsSNPs were located in the codons for conserved active site residues of RecG_Nm. A transient reduction in transformation of DNA was observed in the Nm ΔrecG strain as compared to the wildtype. The gene encoding recG_Nm also contained an unusually high number of the DNA uptake sequence (DUS) that facilitate transformation in neisserial species. The differentially abundant protein profiles of the Nm wildtype and ΔrecG strains suggest that expression of RecG_Nm might be linked to expression of other proteins involved in DNA repair, recombination and replication, pilus biogenesis, glycan biosynthesis and ribosomal activity. This might explain the growth defect that was observed in the Nm ΔrecG null mutant.

Cefaclor into the millennium

We review the discovery and development of the cephalosporins and subsequently cefaclor. Cefaclor is active against a wide range of commonly encountered bacterial pathogens, acting by inhibiting cell wall synthesis. Its in vitro activity compares favourably with other beta-lactam antibiotics. Its pharmacokinetic properties indicate that an 8-hourly dosing schedule is appropriate. In addition a delayed release formulation allowing twice daily dosage has been developed. The efficacy of both formulations of cefaclor has been verified by many clinical trials. Cefaclor has been widely used in infections of the respiratory tract (including otitis media), urinary tract and soft tissues. The results of therapy are summarized. The low incidence of adverse events is highlighted and the beneficial influence of this on compliance is described. Finally, the pharmaco-economics of cefaclor are considered.

Characterization of the inoculum effect with Haemophilus influenzae and beta-lactams

An inoculum effect is defined as a four-fold or greater increase in MIC with an increase in bacterial inocula. Haemophilus influenzae was tested for an inoculum effect with ampicillin, cefuroxime, and amoxicillin/clavulanate using the standard initial inocula (5 x 10(5) CFU/mL) and a higher initial inocula (1 x 10(7) CFU/mL). An inoculum effect was observed with both beta-lactamase (TEM-1, ROB-1) positive and beta-lactamase negative strains of H. influenzae when MICs were determined based on turbidity. MICs based on viable cell counts however, demonstrated that only beta-lactamase positive strains of H. influenzae produced an inoculum effect. These observations suggest that MICs determined based on turbidity, using high initial inocula, are not reliable when examining the inoculum effect in H. influenzae. The magnitude of the inoculum effect with beta-lactamase positive strains was beta-lactam dependent (ampicillin > amoxicillin/clavulanate > cefuroxime). beta-lactam kill-curves confirmed the aforementioned results. Addition of the beta-lactamase inhibitor clavulanate completely reversed the inoculum effect in beta-lactamase (TEM-1 and ROB-1) positive strains of H. influenzae with all beta-lactams tested. Introduction of the beta-lactamase gene TEM-1 on plasmid vector pLS88 into a beta-lactamase negative strain of H. influenzae (Rd) produced an inoculum effect based on viable cell counts. In conclusion, our results suggest that the beta-lactam inoculum effect demonstrated by H. influenzae is the result of beta-lactamase production and is poorly assessed by turbidity.

Cefaclor concentration in radicular granuloma after a single oral administration

1. Cefaclor concentrations in radicular granuloma and serum in nonfasting patients after a single oral administration of 500-mg cefaclor were assayed. 2. The mean peak concentrations in radicular granuloma and serum were 2.57 mcg/g and 7.41 mcg/ ml, respectively. The mean ratio of granuloma/serum concentration at the peak time was 0.35. 3. All cefaclor concentrations in radicular granuloma at the peak time exceeded the minimal inhibitory concentration for 90% of oral streptococci (1 mcg/ml) isolated from odontogenic infection.

Effects of prophylactic administration of cefaclor on transient bacteremia after dental extraction

This study was undertaken to investigate the effects of prophylactic administration of cefaclor on bacteremia after dental extraction. Thirty-nine patients were randomly assigned to receive either 1 g cefaclor (19 patients) or placebo (20 patients) 1 h prior to dental extraction. Blood samples for microbiological investigation were collected before, during, and 10 min after surgery, and were processed by lysis filtration under anaerobic conditions. The incidence of bacteremia with viridans streptococci was 79% in the cefaclor group and 50% in the placebo group during extraction. No difference in the incidence or magnitude of bacteremia was observed when the two patient groups were compared.

Cefaclor concentration in pus from abscess caused by odontogenic infection after a single oral administration

1. Cefaclor concentrations in serum and pus from abscess of odontogenic infection after a single oral administration of 500-mg cefaclor were assayed and pus concentrations were compared with minimum inhibitory concentration (MIC) of oral streptococci isolated from odontogenic infection. 2. The mean peak concentrations in serum and pus were found at identical times, 1.5 hr after administration, which were 7.22 and 0.72 micrograms/ml, respectively. 3. The mean ratio of pus:serum concentration at the peak time was 0.10. 4. Most cefaclor concentrations in pus at the peak time (seven of nine cases) exceeded the MIC for 90% of oral streptococci (0.5 micrograms/ml).

Cefaclor concentrations in human serum, gingiva, mandibular bone, and dental follicle following a single oral administration

1. Cefaclor concentrations in human serum (n = 59), gingiva (n = 46), mandibular bone (n = 39), and dental follicle (n = 42) following a single oral administration of cefaclor (500 mg) were measured by the paper disk method. 2. The peak times of serum, gingiva, mandibular bone, and dental follicle were 1.5, 2, 2, and 1.5 hr, respectively. 3. The mean peak concentrations of serum, gingiva, mandibular bone, and dental follicle were 7.58 micrograms/ml, 3.71, 1.59 and 2.42 micrograms/g, respectively. 4. The concentration ratios of gingiva/serum, mandibular bone/serum, and dental follicle/serum at peak times of the tissues were 0.49, 0.18, and 0.32, respectively. 5. Mean cefaclor concentrations in gingiva, mandibular bone, and dental follicle at peak times exceeded MIC for 90% for clinically isolated strains of alpha-hemolytic Streptococci.

Pharmacokinetic study of cefaclor in chronic maxillary sinusitis

The pharmacokinetics of the maxillary sinus fluid were studied in 42 patients (26 males and 16 females), suffering from chronic maxillary sinusitis, after oral administration of 0.5g or 1g cefaclor. A thin plastic catheter, for sinus secretion sampling, was inserted in the sinus cavity and remained in place throughout the study. Sinus fluid levels of cefaclor (0.5g), measured by agar and well-diffusion microbiological method, ranged between 0.17-0.19, 0.28-0.42, 0.18-0.22 and 0.12-0.16 microgram/ml at 2, 4, 6 and 8 hour intervals respectively. Levels ranging between 0.15-0.26, 0.37-0.90, 0.23-0.27 and 0.16-0.19 microgram/ml were found after the administration of 1g cefaclor at the same time intervals respectively. Higher levels were found in purulent nasal material than in cystic fluid aspirates.

Loracarbef versus cefaclor in the treatment of urinary tract infections in women

In a double-blind, prospective, randomized study, 108 college women with acute urinary tract infections were treated for 7 days with either loracarbef (LY163892) at 200 mg once daily (n = 53) or cefaclor at 250 mg three times daily (n = 55). The cure rates at 5 to 9 days after treatment in the loracarbef and cefaclor groups were 96 and 90%, respectively. Both loracarbef and cefaclor are safe, well tolerated, and effective in the treatment of urinary tract infections in women.

In vitro investigation of BK-218, a new oral and parenteral cephalosporin

The antibacterial activity of BK-218 was similar to that of cefamandole when it was tested against several laboratory strains. The inhibiting effect of BK-218 was greater than that of cephalexin and cefoxitin on penicillin-binding proteins of Escherichia coli HB101. This result was in close correlation with the relative inhibition of radiolabeled glucosamine incorporation (greatest with BK-218) and with the lytic effect (most intensive with BK-218). BK-218 proved to be a good inhibitor for all five of the beta-lactamases that were investigated, although two enzymes (Enterobacter cloacae P99 and Pseudomonas aeruginosa Cilote) hydrolyzed it to some extent.

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.

Absolute bioavailability of cefixime in man

In a four-way cross-over study, the absolute bioavailability of cefixime was determined in 16 healthy volunteers. Each subject received a single 200-mg dose as an intravenous (IV) and oral solution, and 200-mg and 400-mg capsule doses of the drug. Blood and urine samples were collected for 24 hours after each dose. Cefixime was well tolerated after IV and oral doses of the drug and no serious drug-related adverse effects were observed. The maximal serum concentration (Cmax) of cefixime following the 200-mg oral solution and 200-mg and 400-mg capsule doses were 3.22, 2.92, and 4.84 micrograms/mL, respectively. Mean area under the serum concentration time curves (AUC) following the IV, 200-mg oral solution, and 200-mg and 400-mg capsule doses were 47.0, 26.0, 23.6, and 39.4 micrograms.hr/mL, respectively. Mean elimination half-life values of the drug were comparable after oral and IV doses, ranging from 3.2 to 3.5 hours. Based on serum AUC values, the absolute bioavailability of cefixime was 52.3%, 47.9%, and 40.2% after the 200-mg oral solution, 200-mg capsule and 400-mg capsule doses, respectively. Respective ratios based on 24-hour urinary recovery data were 44.7%, 41.7%, and 40.5%. Therefore, the results show that the percent of cefixime adsorbed after 200-mg and 400-mg oral doses was similar.

Haemophilus influenzae: antibiotic susceptibility

Ampicillin resistance was first reported among clinical isolates of Haemophilus influenzae in 1972. Reports of chloramphenicol resistance followed shortly thereafter. The principal mechanism of resistance to these two antibiotics is enzymatic. Although other mechanisms have been described, they are found in comparatively few strains. The genetic information for the inactivating enzymes is plasmid mediated and therefore readily transmissible to susceptible strains. Consequently, effective therapy for invasive disease caused by this pathogen has been seriously compromised. As antibiotic susceptibility became less predictable, in vitro testing became increasingly important. Unfortunately, the standardization of methods for laboratory testing has been slow and complicated by the fastidious nature of the organisms. This review traces the development of antibiotic resistance in H. influenzae, discusses the mechanisms which appear to be important in mediating resistance, explores newer antimicrobial agents which might be useful in the treatment of infection, and analyzes the various approaches to in vitro testing.

In vitro activities of LY163892, cefaclor, and cefuroxime

The in vitro activity of LY163892, a synthetic oral cephalosporin, was compared with those of cefaclor and cefuroxime against 1,193 clinical isolates. MIC ranges and MICs for 50 and 90% of isolates of the three cephalosporins were comparable. The activities of LY163892 and cefaclor were, however, highly inoculum dependent against beta-lactamase-positive Haemophilus influenzae and Staphylococcus aureus; that of cefuroxime was not. LY163892 and cefuroxime appeared stable in microdilution trays stored at 5 and -20 degrees C for 5 weeks, in contrast to cefaclor which remained stable for more than a week only at -5 degrees C.

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.

In vitro and in vivo antibacterial activities of T-2588, a new oral cephalosporin, compared with those of other oral beta-lactam antibiotics

T-2588, the pivaloyloxymethyl ester of T-2525, [6R, 7R]-7-[(z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetoamido] -3- [(5-methyl-2H-tetrazol-2-yl)methyl]-3-cephem-4-carboxylic acid, is a new oral cephalosporin. T-2525 had a widely expanded antibacterial spectrum against gram-negative and gram-positive bacteria. T-2525 was more active in vitro than cefaclor, cephalexin, and amoxicillin against members of the family Enterobacteriaceae and Branhamella catarrhalis. Moreover, it exhibited superior in vitro activity against Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria gonorrhoeae. T-2525 was highly stable to various beta-lactamases, which were classified as Richmond and Sykes types Ia, Ib, Ic, III, IV, and Vc. It had high affinities for the lethal (essential) penicillin-binding proteins of Escherichia coli, Clostridium perfringens, and Bacteroides fragilis. T-2588 had excellent therapeutic effect on systemic infections in mice with various species of gram-negative bacteria, including beta-lactamase-producing bacteria.

Influence of growth medium and supplement on growth of Haemophilus influenzae and on antibacterial activity of several antibiotics

In the present study, five non-beta-lactamase- and five beta-lactamase-producing strains of Haemophilus influenzae were used to determine whether three different growth media, Mueller-Hinton broth and agar, brain heart infusion broth and agar, and tryptic soy broth and agar, and their added supplements (0.2% hemin-0.1% IsoVitaleX, 1% hemin-1% IsoVitaleX, 2% sheep blood, 10% Fildes enrichment, 5% Fildes enrichment, 1% supplement B, 5% horse erythrocytes, and 2% hemoglobin-1% IsoVitaleX) would influence the growth rate of this microorganism and the antibacterial activity of eight antibiotics, including ampicillin, tetracycline, chloramphenicol, gentamicin, cefamandole, erythromycin, trimethoprim-sulfamethoxazole (TMP-SMX), and cefoperazone. The growth curve studies were carried out with an initial inoculum of 10(4) bacteria per ml, and MICs were determined with an inoculum of 5 X 10(5) microorganisms. Mueller-Hinton broth, brain heart infusion broth, and tryptic soy broth enriched with 5% Fildes resulted in a maximal growth of more than 10(8) CFU/ml at 24 h. When 10% Fildes or 2% sheep blood was added as enrichment to Mueller-Hinton broth, a considerable reduction in the growth rate of H. influenzae strains resulted (P less than 0.01). Significant variations in MICs (P less than 0.01) were observed with chloramphenicol, TMP-SMX, erythromycin, and cefoperazone when brain heart infusion agar, Mueller-Hinton agar, or tryptic soy agar was used. Chloramphenicol, gentamicin, erythromycin, and TMP-SMX were all affected by the different enrichments added to Mueller-Hinton agar. MICs were in general higher with 5% Fildes enrichment and lower with 1% supplement B. Cefoperazone was the only drug which exhibited a lower MIC in 5% Fildes enrichment for ampicillin-resistant H. influenzae strains.

Comparative antibacterial activity of a new oral cephalosporin, BMY-28100

BMY-28100 is a new oral cephalosporin which had in vitro activity superior to that of cephalexin and cefaclor against staphylococci, beta-hemolytic streptococcal species, and Streptococcus pneumoniae. It inhibited beta-lactamase-producing Haemophilus influenzae, Neisseria gonorrhoeae, 50% of Streptococcus faecalis isolates, Listeria monocytogenes, and 50 to 75% of Escherichia coli and Klebsiella species at less than or equal to 8 micrograms/ml, but high producers of beta-lactamase were resistant. Enterobacter, Citrobacter, Morganella, Providencia, and Pseudomonas species and Bacteroides fragilis were resistant. BMY-28100 was more stable than cefaclor against hydrolysis by beta-lactamases.

In vitro antibacterial effects of cephalosporins

Data from many studies on the antibacterial effects of cephalosporins are reviewed. Variations in reports from different workers occur because of the composition of the strains used to carry out determination of minimum inhibitory concentrations (MICs). For this reason, standard MIC50/MIC90 data are used sparingly. Where data are available, the activity has been expressed as the mode activity against fully sensitive strains of a species; and the activity against resistant strains is specified, as far as the data allow, for the mechanisms of resistance exhibited.

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

Ceftetrame (Ro 19-5247) and cefetamet (Ro 15-8074), two new orally administered aminothiazolyl imimomethoxy cephalosporins, inhibited hemolytic streptococci and Streptococcus pneumoniae at less than or equal to 0.5 micrograms/ml but were less active against staphylococci than were cephalexin and cefaclor. They did not inhibit S. faecalis, S. faecium, Listeria monocytogenes, Corynebacterium JK species, or Pseudomonas aeruginosa. Haemophilus influenzae, Branhamella catarrhalis, and Neisseria gonorrhoeae, including ampicillin-resistant isolates, were inhibited at less than 0.25 micrograms/ml. Both agents inhibited Escherichia coli, Klebsiella pneumoniae, K. oxytoca, Proteus mirabilis, Salmonella species, Shigella species, Citrobacter diversus, and Aeromonas hydrophila resistant to ampicillin, cephalexin, and cefaclor at less than or equal to 2 micrograms/ml, although many isolates of Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens resistant to cefotaxime were not inhibited by these agents. A marked inoculum effect was noted for Enterobacteriaceae carrying the Richmond-Sykes type 1A chromosomally mediated beta-lactamases, but plasmid-mediated beta-lactamases did not hydrolyze the compounds. Both drugs inhibited the chromosomally mediated beta-lactamase of E. cloacae, P99.

In vitro evaluation of cefixime (FK027, FR17027, CL284635): spectrum against recent clinical isolates, comparative antimicrobial activity, beta-lactamase stability, and preliminary susceptibility testing criteria

Cefixime, a new orally absorbed cephalosporin, was compared by in vitro testing with other oral beta-lactams, including cephalexin, cefaclor, cefuroxime, amoxicillin, and amoxicillin + clavulanate. Enterobacteriaceae were inhibited by lower concentrations of cefixime than any of the reference drugs; 90% and 95% were inhibited by less than or equal to 1.0 and less than or equal to 8.0 micrograms/ml, respectively. Cefixime was the least active among these drugs against staphylococci, with only 31% of 1106 strains inhibited by less than or equal to 8.0 micrograms/ml and less than 1% by less than or equal to 1.0 microgram/ml. Enterococci and pseudomonads were not susceptible to any of the drugs tested. Penicillin-resistant pneumococci were relatively resistant to cefixime, but penicillin-susceptible pneumococci were very susceptible to cefixime. Other streptococci were generally susceptible to all compounds tested, with relative activities of amoxicillin greater than cefaclor and cefuroxime greater than cefixime greater than cephalexin. Cefixime was inactive against Bacteroides species. A slight inoculum effect occurred with cefixime with inocolum concentrations varying from 10(5) to 10(6) colony forming units per milliliter, but this was more marked at 10(7) colony forming units per milliliter. Cefixime was resistant to hydrolysis by seven common beta-lactamases. It inhibited the hydrolysis of nitrocefin only by type 1 cephalosporinases. The disk diffusion zone diameter breakpoints for the 30-micrograms cefixime disk were determined by regression analysis to be greater than or equal to 27 mm (susceptible) and less than or equal to 23 mm (resistant), respectively corresponding to minimal inhibitory concentration breakpoints of less than or equal to 1.0 and greater than or equal to 4.0 micrograms/ml. Because of the high interpretive error rate (13.8%) and the occurrence of these breakpoints on the parabolic portion of the regression curve, we recommend further evaluation of cefixime disks with lower potencies.

Comparative antibacterial activity of an arylglycyl oral cephalosporin, LY164846

LY164846 is a semisynthetic arylglycyl cephalosporin which can be absorbed orally. It had in vitro activity comparable to that of cefaclor against beta-hemolytic streptococcal species and was two- to fourfold more active than cephalexin. Enterococci and Listeria species were resistant, and its activity against staphylococci was similar to that of other oral cephalosporins. Although some Bacteroides species were inhibited, the MICs for 25% were greater than or equal to 16 micrograms/ml. LY164846 was hydrolyzed by Staphylococcus aureus beta-lactamase and by cephalosporinases, but it was more stable than cefaclor.

The in vitro activity of the newer beta-lactam antibiotics against 124 strains of gram-negative bacilli

The MIC values of 99 isolates of Enterobacteriaceae to 11 of the newer beta-lactam antibiotics, and 25 isolates of Pseudomonas aeruginosa to 9 of these drugs were compared with representatives of the established beta-lactam antibiotics and gentamicin. The MIC values for the newer agents were significantly lower in comparison with the older reference compounds. The potential clinical use of these newer antibiotics is discussed.

In vitro activity of Ro 15-8074, a new oral cephalosporin, against Neisseria gonorrhoeae

Ro 15-8074, a new cephalosporin the pivaloyloxymethylester of which (Ro 15-8075) is orally absorbable, showed greater in vitro activity than cefaclor against 48 Neisseria gonorrhoeae strains, including 25 penicillinase-producing strains. Unlike cefaclor, Ro 15-8074 was unaffected by increase in inoculum size, and it exhibited a remarkable stability against gonococcal beta-lactamase hydrolysis.

Penetration of cefaclor into bronchial mucosa

Bronchial mucosal biopsy specimens were obtained during fibreoptic bronchoscopy in 30 patients receiving a new oral cephalosporin antibiotic, cefaclor (10 had 250 mg, 10 had 500 mg, and 10 had 1000 mg every eight hours). In 10 patients (from all dosage groups) cefaclor was undetectable in the bronchial mucosa but in every case the serum concentration was low, suggesting incomplete absorption. The mean (SD) bronchial mucosal concentration after 250 mg was 3.78 (1.77) micrograms/g (range 2.1-5.8 micrograms/g, n = 4), after 500 mg 4.43 (2.04) micrograms/g (range 2.0-7.1 micrograms/g, n = 8), and after 1000 mg 7.73 (2.76) micrograms/g (range 5.0-12.7 micrograms/g, n = 6). A significantly higher concentration in the bronchial mucosa was achieved with 1000 mg than with 250 mg (p less than 0.05) or 500 mg (p less than 0.025). These concentrations should be effective against Streptococcus pneumoniae, most strains being inhibited below 1.0 microgram/ml. The concentrations were within one dilution of the minimal inhibitory concentration for Haemophilus influenzae, most strains being inhibited below 4.0 micrograms/ml. Some strains of H influenzae will not be inhibited by the concentrations of cefaclor found in the bronchial mucosa, particularly those that are ampicillin resistant.

The pharmacokinetics of antibiotics used to treat peritoneal dialysis-associated peritonitis

Antibiotics continue to be used frequently to treat CAPD-associated peritonitis. Selection of appropriate antibiotic doses and routes of administration has been based largely upon clinical experience. Early pharmacokinetic studies utilized patients being treated with IPD. The relevance of these studies to CAPD remains unknown. Little information exists on the effects of peritonitis on peritoneal drug transport. Until the effects of peritonitis during CAPD are better understood, pharmacokinetic data will be of limited value in designing specific treatment recommendations for this common complication of peritoneal dialysis.

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.

Susceptibility of Haemophilus influenzae type b to cefaclor and influence of inoculum size

Cefaclor appeared to be an effective antibiotic against both beta-lactamase-positive and beta-lactamase-negative strains of Haemophilus influenzae type b when tested with 10(5) colony-forming units per ml. With inocula in excess of 10(6) colony-forming units per ml, these organisms were neither inhibited nor killed at concentrations of 400 micrograms/ml. This inoculum effect was also demonstrated in time-kill curve studies.

A double-blind study of cefaclor and amoxycillin in home and hospital-acquired infections

Eighty-seven patients admitted to hospital for a variety of reasons and who had, or subsequently developed, an infection were treated with either cefaclor or amoxycillin, 150 mg 3-times daily, on a double-blind basis. Two patients were excluded from te final analysis as the infecting organisms would normally be resistant to both antibiotics. Forty (93%) patients treated with cefaclor and 40 (95.2%) treated with amoxycillin responded satisfactorily. Of the patients with a hospital-acquired infection, 93.3% of the cefaclor group and 94.3% of the amoxycillin group responded satisfactorily. The differences between the groups were not significant. A greater number of organisms were sensitive to cefaclor, confirming its broader spectrum of activity. It is concluded that cefaclor is a useful first-line antibiotic which could be particularly useful in hospital-acquired infections.

Cefaclor pharmacokinetic parameters: serum concentrations determined by a new high-performance liquid chromatographic technique

Pharmacokinetic parameters of cefaclor were studied in eight patients after an oral dose of 250 mg. Serum samples were obtained before and on 19 occasions after oral administration. Cefaclor serum concentrations were determined by a new high-performance liquid chromatographic technique.

Bactericidal activity of cefoperazone with CP-45,899 against large inocula of beta-lactamase-producing Haemophilus influenzae

Bactericidal activity of cefoperazone, alone and in combination with the beta-lactamase inhibitor CP-45,899, was tested against inocula of 10(7) colony-forming units of beta-lactamase-producing isolates of Haemophilus influenzae type b per ml. Of 19 strains tested, 10 required greater than or equal to 64 microgram of cefoperazone per ml for killing, whereas no strains were killed by less than 64 microgram of CP-45,899 per ml. Synergy occurred with the combination of 4 microgram of each agent per ml against 9 of the 10 cefoperazone-resistant strains.

Cefaclor in management of streptococcal pharyngitis, otitis media, and skin infections

Cefaclor, a semisynthetic cephalosporin antibiotic for oral use, was studied by 62 clinical investigators in six countries in 3,084 adult and pediatric patients. The pooled data reveal that satisfactory clinical responses were obtained in 96% of the streptococcal pharyngitis cases, 93% of the cases of otitis media, and 97% of skin infections. Administration of this antibiotic was associated with a low incidence of adverse reactions, including 73 gastrointestinal and 34 hypersensitivity reactions. Of particular clinical interest were the outstanding results obtained in the treatment of otitis media.

A pharmacological study of cefaclor in the newborn infant

The absorption and excretion of cefaclor were studied in 10 newborn infants. A mean peak serum concentration of 7.7 microgram/ml was achieved at 1 hour after an oral dose of 7.5 mg/kg. It is concluded that cefaclor is a well absorbed and tolerated cephalosporin for use in newborn infants.

The cephalosporins: activity and clinical use

The cephalosporin antibiotics have been employed with increasing frequency since their introduction into clinical practice in the early 1960s. With the exception of cephaloridine, cephalosporin compounds are not associated with the production of significant untoward effects. The availability of newer cephalosporins, both oral and parenteral, with enhanced antibacterial activity, has expanded the clinical indications for administration of these antibiotics.

Effect of inoculum size and beta-lactamase production on in vitro activity of new cephalosporins against Haemophilus species

Sixty-three strains of Haemophilus species, 38 of which were beta-lactamase producers (37 H. influenzae type b, 1 H. parainfluenzae) and 25 of which were beta-lactamase negative (20 H. influenzae, 5 H. parainfluenzae), were tested for susceptibility to cefoxitin, moxalactam (LY127935) (Lilly), cefsulodin (CGP 7174 E, Ciba), and cefoperazone (T 1551, Pfizer). Cefsulodin was relatively inactive at both low and high inocula. LY127935 and cefoperazone displayed inoculum-dependent bactericidal activity. Cefoxitin displayed little inoculum effect against beta-lactamase-producing strains: 8 and 16 microgram/ml killed at least 90% of those tested at 10(4) and 10(6) colony-forming units per ml, respectively.

Cefaclor in the treatment of susceptible infections in infants and children

Fifjty-two outpatients, aged from six months to 17 years, and suffering from Group A streptococcal pharyngitis, skin and soft tissue infection, urinary tract infection, or otitis media were enrolled in the study. The dosage of cefaclor was 20 to 40 mg/kg/day in three or four divided doses for ten days. In 43 children given either cefaclor suspension or capsules, plasma level estimations were performed. Cefaclor readily produces therapeutic plasma levels in children. Cefaclor appears to be a safe, well tolerated and effective antimicrobial agent in children. It has a distinct advantage over other antibiotics in children with Haemophilus influenzae otitis media and should be considered as a primary drug in treatment of otitis media.

[In vitro activity of cefaclor against Haemophilus influenzae in comparison to various oral chemotherapeutic agents (author's transl)]

The antibacterial activity of cefaclor against 100 non-beta-lactamase producing and 11 beta-lactamase producing isolates of Haemophilus influenzae was compared with that of cephalexin, ampicillin, chloramphenicol, tetracycline and co-trimoxazole. A new standardized microtiter dilution technique was used. Cefaclor showed greater activity than did cephalexin and inhibited beta-lactamase producing H. influenzae isolates. Ampicillin was the most active compound against non-beta-lactamase producing isolates. One of our strains was resistant to chloramphenicol and one resistant to tetracycline.

[The antibacterial efficacy of cefaclor against bacteria resistant to ampicillin, tetracycline and co-trimoxazole (author's transl)]

The antibacterial activity of the new oral cephalosporin cefaclor was investigated using 623 freshly isolated bacterial strains. A high degree of efficacy of cefaclor was noticed against Escherichia coli, Proteus mirabilis and Klebsiella. Nearly all strains which were sensitive to ampicillin, tetracycline and co-trimoxazole were also inhibited by cefaclor. Some of the strains resistant to the three above-mentioned antibiotics were also sensitive to cefaclor as follows: all of ten P. mirabilis strains resistant to co-trimoxazole, 54% of the E. coli strains resistant to ampicillin, tetracycline and co-trimoxazole, and 18% of the Klebsiella strains resistant to tetracycline and co-trimoxazole.

Summary of laboratory studies on the antibacterial activity of cefaclor

Laboratory aspects of cefaclor, a new orally-effective cephalosporin antibiotic, are summarized. On the basis of data from a variety of studies, the useful antibacterial spectrum of cefaclor is shown to include all classes of bacteria that are generally susceptible to cephalothin and cephalexin. Cefaclor has a significant potency advantage over cephalexin against many Enterobacteriaceae, Haemophilus sp. and Streptococcus pneumoniae. Bacteria that are susceptible to cefaclor are killed by concentrations at or near the inhibitory concentration. In vitro enzymatic hydrolysis experiments have shown that cefaclor is a relatively good substrate for several beta-lactamases. Orally administered cefaclor is effective in protection of mice from the lethal effects of intraperitoneal challenges with cefaclor-susceptible bacteria. The chemical instability of cefaclor, test medium composition and inoculum density influence the results of in vitro susceptibility tests with cefaclor. Methods for routine susceptibility testing are described.