Coordination and redox interactions of β-lactam antibiotics with Cu2+ in physiological settings and the impact on antibacterial activity

An increase in the copper pool in body fluids has been related to a number of pathological conditions, including infections. Copper ions may affect antibiotics via the formation of coordination bonds and/or redox reactions. Herein, we analyzed the interactions of Cu²⁺ with eight β-lactam antibiotics using UV-Vis spectrophotometry, EPR spectroscopy, and electrochemical methods. Penicillin G did not show any detectable interactions with Cu²⁺. Ampicillin, amoxicillin and cephalexin formed stable colored complexes with octahedral coordination environment of Cu²⁺ with tetragonal distortion, and primary amine group as the site of coordinate bond formation. These β-lactams increased the solubility of Cu²⁺ in the phosphate buffer. Ceftazidime and Cu²⁺ formed a complex with a similar geometry and gave rise to an organic radical. Ceftriaxone-Cu²⁺ complex appears to exhibit different geometry. All complexes showed 1:1 stoichiometry. Cefaclor reduced Cu²⁺ to Cu¹⁺ that further reacted with molecular oxygen to produce hydrogen peroxide. Finally, meropenem underwent degradation in the presence of copper. The analysis of activity against Escherichia coli and Staphylococcus aureus showed that the effects of meropenem, amoxicillin, ampicillin, and ceftriaxone were significantly hindered in the presence of copper ions. The interactions with copper ions should be taken into account regarding the problem of antibiotic resistance and in the selection of the most efficient antimicrobial therapy for patients with altered copper homeostasis.

Immunomodulatory Properties of Cefaclor:In VivoEffect on Cytokine Release and Lymphoproliferative Response in Rats

The proper and coordinated response of the host immune system to bacterial infections is known to play a central role in the eradication of an infection. Therefore, the impact of antibiotics on both innate and acquired host immunity may be involved in the therapeutic outcome. The aim of this study was to evaluate the effects of the widely used cephalosporin cefaclor on some parameters of the immune system in ex vivo conditions. The results demonstrated that short-term (3 to 6 days) treatment with this antibiotic induced pleiotropic modification of rat spleen cells upon ex vivo stimulation with the polyclonal mitogen PHA, entailing increased lymphoproliferative responses, augmented IFN-gamma, IL-2 and IL-10 synthesis and decreased production of IL-4 and IL-6 in comparison to spleen cells from control rats. The mononuclear spleen cells of healthy rats released larger amounts of IFN-gamma and IL-2 in culture supernatants in response to polyclonal mitogenic stimulation with PHA compared to the spleens of the control rats receiving vehicle only. Simultaneously, the treatment with cefaclor augmented PHA-induced lymphoproliferative responses and reduced the synthesis of IL-4 and IL-6. These data depict a type 1 cytokine inducing and immunostimulatory pharmacological profile that, by activating the innate and acquired immune system, would be synergistic with cefaclor antibacterial activity.

Synthesis, spectral and antibacterial sudies of copper(II) tetraaza macrocyclic complexes

A novel family of tetraaza macrocyclic Cu(II) complexes [CuLX(2)] (where L = N(4) donor macrocyclic ligands) and (X = Cl(-), NO(3) (-)) have been synthesized and characterized by elemental analysis, magnetic moments, IR, EPR, mass, electronic spectra and thermal studies. The magnetic moments and electronic spectral studies suggest square planar geometry for [Cu(DBACDT)]Cl(2) and [Cu(DBACDT)](NO(3))(2) complexes and distorted octahedral geometry to the rest of the ten complexes. The biological activity of all these complexes against gram-positive and gram-negative bacteria was compared with the activity of existing commercial antibacterial compounds like Linezolid and Cefaclor. Six complexes out of twelve were found to be most potent against both gram-positive as well as gram-negative bacteria due to the presence of thio group in the coordinated ligands.

Evaluation of cefaclor oral suspensions stability using reversed phase high performance liquid chromatography and antimicrobial diffusion methods

The effect of temperature stresses on Cefaclor suspensions under different storage conditions for a duration of 14 days was tested. The degradation of Cefaclor was determined on the 2nd, 7th and 14th day after reconstitution using a sensitive and precise Reversed phase High Performance Liquid Chromatographic (RP-HPLC) method. The RSD values for Forticef, Midocef, Ceclor, Cefabac and Cloracef, indicated a good precision of the RP-HPLC method. The limit of detection (LOD) and the limit of quantification (LOQ) were found 0.008 mg/ml and 0.03mg/ml respectively. The antimicrobial effect of Cefaclor suspension was also tested against pathogenic bacteria using the cylinder diffusion method. The RSD values range of the antimicrobial assay for all the Cefaclor compounds were 1.47-3.7%. The LOD and LOQ were 0.2mg/ml and 1mg/ml respectively. During the normal use of Ceclor, Midocef, and Forticef the loss of activity and the degradation were less than 5% on the 14th day of preservation at 4°C. However, the percentage of degradation for Cefabac and Cloracef on the 14th day reached 5 and 6%, respectively. Statistical multiple comparison between the effect of 4°C and 25°C indicated non significant mean differences (P>0.05) for Forticef, Cefabac, Ceclor and Cloraf and significant effect for Midocef (P <0.05). Significant effects were observed between (4oC and 37°C) and (25°C and 37°C) for all except Ceclor. Multiple comparisons between days of storage showed non significant mean difference values at 4°C except Cefabac. However significant results between days were found at 25°C and 37°C except for Midocef between (7th and 14th day). It was found that the pediatric suspensions of Cefaclor in the Jordanian market were stable and contained the amount of active ingredient specified by the United States pharmacopoeias specification (USP) and the British Pharmacopoeias specifications (BP).

[A simple disk diffusion test to identify beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae--application of cephalexin, cefsulodin and cefaclor disks]

Currently, beta-lactamase-negative (BLN) ampicillin-resistant (AR) strains of Haemophilus influenzae are prevalent in Japan. BLNAR strains are defined by the presence of specific mutation(s) in the ftsI gene but are not phenotypically distinguishable by ampicillin (ABPC) susceptibility. In the present study, we showed that cephalexin (CEX), cefsulodin (CFS), and cefaclor (CCL) disk diffusion tests can be effectively used to identify BLNAR strains. A total of 169 clinical isolates of BLN H. influenzae, consisting of 113 of BLNAR and 56 of BLN, ampicillin-susceptible (AS), were included. All the isolates were genetically defined by detection of the TEM gene and partial sequencing of the ftsI gene. The Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution and disk diffusion tests for ABPC provided 20% and 19% false susceptible rates, respectively. Alternatively, 34 cephem agents were tested using disk diffusion. Of the agents tested, CEX, CFS, and CCL disks could effectively discriminate between BLNAR and BLNAS isolates. All the BLNAS isolates showed visible growth inhibitory zones around CEX and CFS disks, but 108 (95.6%) and 106 (93.8%) BLNAR isolates did not. The results indicated 100% predictive values (PVs) for BLNAR and PVs for BLNAS were 91.8% for CEX and 88.9% for CFS. The CLSI-based interpretations for CCL (> or =20 mm) also highly correlated with BLNAR and BLNAS, PVs for BLNAR and for BLNAS being 100% and 93.3%, respectively. With simplicity and discriminability of the test method, we recommend a CEX disk diffusion test in combination with a rapid beta-lactamase test to identify BLNAR isolates in clinical laboratories.

In vitro antimicrobial activity of cefditoren and other oral antibiotics against Streptococcus pneumoniae, isolated from children with community acquired respiratory tract infections

The antibacterial susceptibility to frequently prescribed antibiotics of Streptococcus pneumoniae isolated from the pediatric patients with acute respiratory infectious diseases was investigated in a study of three medical institutions in Korea. Total 143 clinical isolates of S. pneumoniae were available for susceptibility tests between May 2003 and July 2007. Antimicrobial susceptibility data for S. pneumoniae were analyzed by using agents of amoxicillin, cefaclor, cefuroxime, cefdinir, and cefditoren as the test antibiotics. The prevalence of each resistance class, penicillin-resistant S. pneumoniae (PRSP) were high with the proportion of MIC range (susceptible = 8.4%, intermediate resistance = 18.2%, resistance = 73.4%). MIC90 and susceptible (S) rate of antimicrobial agents to the strains tested were amoxicillin (MIC90 = 4 microg/ml, S = 76.2%), cefaclor (MIC90 = 128 microg/ml, S=8.4%), cefuroxime (MIC90 = 16 microg/ml, S = 24.5%), cefdinir (MIC90 = 16 microg/ml, S = 21.8%), and cefditoren (MIC90 = 0.5 microg/ml, S=90.2%) respectively. Against clinical isolates including PRSP, cefditoren demonstrated the strongest antibacterial activity intrinsically among the antibiotics tested. Conclusively, the antimicrobial activity of cefditoren to S. pneumoniae strains isolated from pediatric patients with acute respiratory infection is very high. In South Korea, where the antibiotic resistance ofS. pneumoniae is issued, cefditoren is expected to be used as a primary or secondary antibiotic. Moreover, cefditoren may serve as a useful option for secondary antibiotics after failure of amoxicillin treatment, which is most primarily used for acute respiratory S. pneumoniae infection in children.

Pharmacokinetic interaction between cefaclor and bromhexine in healthy Chinese volunteers

OBJECTIVE

To determine the pharmacokinetic interaction between cefaclor and bromhexine in healthy Chinese volunteers.

METHODS

Twelve subjects received a cefaclor (CEF) treatment, a bromhexine (BHX) treatment, and a co-treatment of CEF and BHX with a 3 x 3 Latin square design. The wash-out time between periods was 14 days. The plasma and urine drug concentrations of CEF and BHX were detected by HPLC-UV and LC/MS, respectively.

RESULTS

All the 12 volunteers completed the study. There were no significant differences in AUC 0-t and Cmax of CEF in logarithm between the single administration group of CEF and the co-administration group of CEF with BHX. Two one sided t-test showed that CEF was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, and Clr between the 2 groups. Vd/F was significantly lower in the single CEF group than in the co-administration group of CEF and BHX. There were no significant differences of AUC 0-t and Cmax of BHX in logarithm between the single administration group of BHX and the co-administration group of BHX with CEF. Two one sided t-test showed that BHX was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, Vd/F, and Clr between the 2 groups.

CONCLUSION

There is no significant pharmacokinetic parameter change in the drug absorption, metabolism, and excretion, but Vd/F of CEF significant increases in the co-administration of CEF with BHX. The co-administration of CEF and BHX has no adverse drug interaction. The increase of Vd/F may be a favorable drug interaction, which may be the mechanism of the synergistic effect of the 2 drugs.

INTERACTIONS OF AMOXICILLIN AND CEFACLOR WITH HUMAN RENAL ORGANIC ANION AND PEPTIDE TRANSPORTERS

Amoxicillin and cefaclor are two of the widely used beta-lactam antibiotics in the treatment of urinary tract infections. Both drugs are eliminated mainly by the kidney and rely on renal excretion to exert their antibacterial activities in the urinary tract. Previous studies have suggested the involvement of organic anion and oligopeptide transporters in membrane transport of beta-lactams. The objective of the current study was to examine the kinetics of amoxicillin and cefaclor interactions with human renal transporters human organic anion transporter 1 (hOAT1), human peptide transporter 1 (hPepT1), and human peptide transporter 2 (hPepT2) in detail, both as substrates and as inhibitors. Using fluorescence protein tagging and cell sorting, we established Madin-Darby canine kidney cell lines stably expressing highly functional hOAT1, hPepT1, and hPepT2. Amoxicillin and cefaclor inhibited hOAT1-mediated [(3)H]para-aminohippuric acid uptake (K(i) = 11.0 and 1.15 mM, respectively). However, our uptake study revealed that neither drug was transported by hOAT1. Amoxicillin and cefaclor competitively inhibited hPepT2-mediated [(3)H]glycylsarcosine uptake (K(i) = 733 and 65 muM, respectively), whereas much lower affinity for hPepT1 was observed with both antibiotics. Direct uptake studies demonstrated that amoxicillin and cefaclor were transported by hPepT1 and hPepT2. Kinetic analysis showed that hPepT2-mediated uptake of both drugs was saturable with K(m) of 1.04 mM for amoxicillin and 70.2 muM for cefaclor. hPepT2, and to a lesser extent hPepT1, may play an important role in apical transport of amoxicillin and cefaclor in the renal tubule. hOAT1, in contrast, is not involved in basolateral uptake of these antibiotics.

In vitro investigation of the indirect pathogenicity of beta-lactamase-producing microorganisms in the nasopharyngeal microflora

OBJECTIVE

Nasopharyngeal microflora contains some beta-lactamase-producing microorganisms. In this study, we investigated in vitro on the indirect pathogenicities of Haemophilus parainfluenzae (H. parainfluenzae) and Moraxella catarrhalis (M. catarrhalis) against the antipneumococcul activities of some beta-lactams.

METHODS

We compared the antimicrobial and bactericidal activities of beta-lactams against penicillin-susceptible Streptococcus pneumoniae (PSSP) with or without presence of the enzymes of two species of beta-lactamase-producing microorganisms, H. parainfluenzae and M. catarrhalis.

RESULTS

When adding the enzymes extracted from these two beta-lactamase-producing microorganisms in equivalent amounts of 10(7) CFU/spot, the minimum inhibitory concentrations of amoxicillin (AMPC) and cefaclor (CCL) increased to >64 microg/mL. Even third-generation cephalosporins, such as cefditren (CDTR) and ceftriaxone (CTRX) showed marked increases with the enzyme of M. catarrhalis. In time-kill kinetics, same phenomenon was observed in mixed culture indicating the indirect pathogenicities of distinct bacteria, not extracted enzymes, on the cidal activities of beta-lactams against PSSP. Clavulanic acid (CVA)/AMPC, faropenem (FRPM), and imipenem (IPM) were not affected by these beta-lactamase-producing strains with respect to their activities against PSSP. However, these two beta-lactamase-producing strains and their enzymes did not show any significant influence on the antipneumococcul activities of beta-lactams, until the number of bacterial cells reached >10(8) CFU/mL.

CONCLUSION

Our results suggest that these two species of beta-lactamase-producing microorganisms in the nasopharyngeal microflora may act as indirect pathogens on the antipneumococcul activities of beta-lactams with reflecting their substrate profiles, but this is dependent on sufficient amounts of enzyme for their influence as indirect pathogens.

[Comparison of pharmacokinetics/pharmacodynamics of cefdinir, cefpodoxime proxetil and cefaclor against common bacteria of community acquired infections]

OBJECTIVE

To compare the pharmacokinetics/pharmacodynamics property of cefdinir, cefpodoxime proxetil and cefaclor against common bacteria of community acquired infections and evaluate the recommended regimens.

METHODS

The antibacterial activities of 3 agents against 238 clinical isolates were determined by standard agar dilution test and the pharmacokinetics of these antibiotics in male healthy volunteers were conducted in Latin-square manner. The time over MIC (T > MIC) of serum antibiotic concentrations were calculated with pharmacokinetic equation and MIC.

RESULTS

The value of MIC90 s cefdinir against these bacterial strains except penicillin non-sensitive pneumococci were 0.031-1 mg/L. Cefpodoxime held similar antibacterial activity with cefdinir, but was less potent against staphylococci. Cefaclor had much higher MIC values than other two drugs. After oral administration of 250 mg cefaclor, the drug concentration quickly reached peak concentration of 4.95 mg/L +/- 2.41 mg/L and the eliminative half time was 0.69 h +/- 0.6 h; the Tmax, Cmax and T1/2beta of cefdinir and cefpodoxime after oral administration of 100 mg were 2.5 h +/- 0.48 h, 0.81 mg/L +/- 0.19 mg/L, 1.73 h +/- 0.3 h and 2.38 h +/- 0.43 h, 1.12 mg/L +/- 0.28 mg/L, 1.92 h +/- 0.55 h, respectively. T > MIC of cefdinir in thrice daily administration were longer than 40% of medication interval against most of the tested isolates; no T > MIC period was found in cefpodoxime against staphylococci and the T > MICs of cefaclor after 250 mg oral administration were shorter than expected values against most bacteria.

CONCLUSION

With powerful antibacterial activity, the T > MICs of cefdinir after 100 mg oral administration can meet with the clinical requirement in most infections; PK/PD value of cefpodoxime proxetil against staphylococci is lower than expectancy and 250 mg cefaclor 3 times daily is not enough to the treatment of common community acquired infections, the regimens of cefpodoxime proxetil and cefclor should be furtherly optimized.

Reassessment of cefaclor breakpoints for Haemophilus influenzae

We previously reported that standard methods overestimate cefaclor minimum inhibitory concentrations (MICs) for Streptococcus pneumoniae due to in vitro chemical instability. This study aimed to ascertain if standard methods accurately measure cefaclor MICs to Haemophilus influenzae. Cefuroxime was used as a comparator. Standard NCCLS broth microdilution and E-Test MICs were determined for eight isolates of H. influenzae. Kill curves determined the "bacteriostatic" MIC, defined as the concentration showing no significant growth or kill over six hours taking into account cefaclor instability. On average, cefaclor and cefuroxime bacteriostatic MICs were 0.2 x MIC and 0.6 x MIC determined by NCCLS methodology respectively. The mean MIC determined by NCCLS methodology was 3.0 mg/L for cefaclor and 0.8 mg/L for cefuroxime. Cefaclor MICs by NCCLS methodology were overestimated due to chemical instability over 18-24 hours. The bacteriostatic MICs by kill curve were not significantly different from those of cefuroxime.

Streptococcus pneumoniae in vitro development of resistance to amoxicillin/clavulanic acid, cefaclor, levofloxacin and azithromycin

The purpose of this study was to determine effect of repeated exposure to sub-inhibitory concentrations of amoxicillin/clavulanic acid on the development of resistance in Streptococcus pneumoniae. Other agents, azithromycin, cefaclor and levofloxacin, were also tested. Twenty S. pneumoniae were passaged for 9 days in the presence of sub-inhibitory concentrations of each antimicrobial agent and MICs determined by NCCLS macro-dilution method. There was a four-fold increase in amoxicillin/clavulanic acid MICs for 2 of 20 isolates. Three of 9 tested against cefaclor, 11 of 13 tested against azithromycin and 9 of 20 tested against levofloxacin showed > or =4-fold increase. Amoxicillin/clavulanic acid was the most stable of the agents tested. Cefaclor MICs were also fairly stable. Azithromycin and levofloxacin MICs were most affected.

Detection of penicillin-binding protein 2b gene alteration in Streptococcus mitis by polymerase chain reaction

Three isolates of beta-lactam-resistant streptococci from the saliva of healthy adults were identified as Streptococcus mitis. Minimum inhibitory concentrations (MICs) were 2 to 4 micro g/ml for ampicillin (ABPC) and 64 to more than 128 micro g/ml for cefaclor (CCL). To determine the position of base alterations of the penicillin-binding protein 2b ( pbp2b) gene, upstream primers containing possible mutation points were designed, and used for polymerase chain reaction (PCR), together with a downstream primer. Alterations adjacent to the conserved motifs of the pbp2b gene were apparent. DNA sequencing data indicated replacements in deduced amino acid sequences in all resistant isolates: from threonine to alanine just after the serine-serine-asparagine (SSN) motif, and from alanine to glycine two residues downstream of the lysine-threonine-glycine (KTG) motif. These changes were the same as those in penicillin-resistant Streptococcus pneumoniae (PRSP), suggesting importance for the enzymatic activity of the protein. Thus, Beta-lactam susceptibility of S. mitis may be partially predicted by PCR using our primer set for pbp2b.

Reassessment of the cefaclor breakpoint for Streptococcus pneumoniae

Discrepancies between proven clinical success of cefaclor and its relatively poor activity in vitro were investigated against eight pneumococcal isolates. The bacteriostatic minimum inhibitory concentration (MIC) (the concentration resulting in no growth/kill relative to the starting inoculum) was derived from time kill studies. Bioassay results demonstrated an in vitro half-life of >24 and 9 h for cefuroxime and cefaclor, respectively. The mean NCCLS MIC for cefaclor was 1.4 and 0.3 mg/l for cefuroxime. The corresponding mean bacteriostatic MICs were 0.24 and 0.16 mg/l. Whilst cefaclor NCCLS MICs were significantly higher compared with cefuroxime MICs (P = 0.00058) there was no statistical differences between the bacteriostatic MICs (P = 0.259). Bacteriostatic MIC determination established that cefaclor and cefuroxime are equally active against pneumococci.

PK–PD modelling of the effect of cefaclor on four different bacterial strains

The effect of cefaclor against relevant bacterial strains was studied by employing a combined in vivo pharmacokinetic (PK)-in vitro pharmacodynamic (PD) approach. For this purpose selected isolates of Escherichia coli, Moraxella catarrhalis, Haemophilus influenzae and Streptococcus pneumoniae were exposed in vitro to the interstitial cefaclor profile obtained in vivo in the interstitial space fluid of human tissue after administration of commonly used doses of cefaclor and the change in the number of colony forming units per millilitre (CFU/ml) versus time was monitored. Fitting of the data using a modified E(max)-model resulted in a set of mean pharmacodynamic parameters (k0, k(max), EC50) for each bacterial strain. The parameters derived from these experiments were used in a computer-simulation of the antibacterial effects for different dosing regimens and formulations of cefaclor, notably an immediate (IR) and a modified (MR) release formulation. Dosage regimens were compared using the ratio between the number of bacteria remaining after 24 h of a given treatment (N24h). The results indicate that the number of bacteria of all investigated strains killed per day is equivalent when the same daily dose is administered twice a day with the MR dosage form than when given three times a day with the IR dosage form, in spite of the fact that the MR dosage form has approximately 20% lower bioavailability. Best results were obtained with the three-times a day regimen of the MR formulation. In conclusion, the present in vivo-PK/in vitro-PD simulations of the antimicrobial effects of cefaclor indicate that a twice-daily treatment with a MR formulation may offer a convenient and safe alternative to the conventional tid treatment.

Beta-lactam resistance in Streptococcus mitis isolated from saliva of healthy subjects

The purpose of this study was to examine the percentage of Beta-lactam-resistant streptococcal carriers in healthy adults, and to investigate the relationships among minimum inhibitory concentrations (MICs) of Beta-lactams, alterations in the penicillin-binding protein genes ( pbp genes), and the affinity of penicillin-binding proteins (PBPs) for ampicillin (ABPC) in Streptococcus mitis. We also compared numbers of surviving bacteria at various ABPC concentrations in both ABPC-susceptible and -resistant S. mitis strains. The percentages of subjects carrying ABPC- and cefaclor (CCL)-resistant streptococci were 52% (27 of 52 subjects) and 100%, respectively. S. mitis, including both antibiotic-susceptible and -resistant strains, were classified into five groups according to the pbp gene mutations that resulted in alterations of the deduced amino-acid sequence in the homology boxes of PBPs. All ABPC-resistant strains showed alterations in PBP1A, 2X, and 2B, while no or only PBP2X alterations were detected in the susceptible strains. These results suggest that the accumulation of pbp gene mutations is strongly related to the MIC of ABPC for S. mitis. In the resistant strains, the affinity of PBPs for ABPC was reduced in comparison with that in the susceptible strains, and the bactericidal effect of ABPC was also reduced. Therefore, we should be aware of conditions such as infective endocarditis that are caused by Beta-lactam-nonsusceptible streptococci in the normal oral flora.

[Susceptibility of Branhamella catarrhalis to antibiotics]

A total of 98 isolates of Branhamella catarrhalis were examined for their susceptibility to antibiotics using serial dilution method. Nitrocefin test was employed for detection of beta-lactamase activity. It was found that most of the isolates (71%) were resistant to ampicillin. Resistance to this antibiotic was accompanied by ability to beta-lactamase production. On the other hand, all isolates were susceptible to amoxicillin + clavulanic acid combination. Almost all isolates were susceptible to cefaclor (99%), cefuroxime (94%), cefotaxime (100%), ciprofloxacin (100%), tetracycline (91%), cotrimoxazole (93%) and erythromycin (93%).

Microbiological analysis of infected root canals from symptomatic and asymptomatic teeth with periapical periodontitis and the antimicrobial susceptibility of some isolated anaerobic bacteria

The purpose of the present study was to investigate the correlation between the composition of the bacterial flora isolated from infected root canals of teeth with apical periodontitis with the presence of clinical signs and symptoms, and to test the antibiotic susceptibility of five anaerobic bacteria mostly commonly found in the root canals of symptomatic teeth against various substances using the E-test. Microbial samples were taken from 48 root canals, 29 symptomatic and 19 asymptomatic, using adequate techniques. A total of 218 cultivable isolates were recovered from 48 different microbial species and 19 different genera. Root canals from symptomatic teeth harbored more obligate anaerobes and a bigger number of bacterial species than the asymptomatic teeth. More than 70% of the bacterial isolates were strict anaerobes. Statistical analysis used a Pearson Chi-squared test or a one-sided Fisher's Exact test as appropriate. Suggested relationships were found between specific microorganisms, especially gram-negative anaerobes, and the presence of spontaneous or previous pain, tenderness to percussion, pain on palpation and swelling amoxicillin, amoxicillin + clavulanate and cephaclor were effective against all the strains tested. The lowest susceptibility rate was presented by Prevotella intermedia/nigrescens against Penicillin G. Our results suggested that specific bacteria are associated with endodontic symptoms of infected teeth with periapical periodontitis and the majority of the anaerobic bacterial species tested were susceptible to all antibiotics studied.

Haemophilus influenzae bla(ROB-1) mutations in hypermutagenic deltaampC Escherichia coli conferring resistance to cefotaxime and beta-lactamase inhibitors and increased susceptibility to cefaclor

The clinical use of cefaclor has been shown to enrich Haemophilus influenzae populations harboring cefaclor-hydrolyzing ROB-1 beta-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or beta-lactams plus beta-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in H. influenzae. In order to establish which bla(ROB-1) mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to beta-lactamase inhibitors, a plasmid harboring bla(ROB-1) was transformed into hypermutagenic strain Escherichia coli GB20 (DeltaampC mutS::Tn10), and this construct was used in place of H. influenzae bla(ROB-1). Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected beta-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the bla(ROB-1) gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169-->Ser169 or the Arg164-->Trp164 substitution or the double amino acid change Arg164-->Trp164 and Ala237-->Thr237. ROB-1 mutants that were resistant to beta-lactams plus beta-lactamase inhibitors and that harbored the Arg244-->Cys244 or the Ser130-->Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if bla(ROB-1) mutants were selected by cefaclor, this drug would prevent the further evolution of this beta-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or beta-lactamase inhibitors.

[Antibacterial activity of cefpodoxime against clinical isolates in 2000 and 2001]

As the post-marketing surveillance of cefpodoxime proxetil (Banan), MICs of cefpodoxime (CPDX, an active form of Banan) against 1090 clinical isolates of 22 species from 15 medical institutions all over Japan from June 2000 to March 2001 were measured using the broth microdilution method approved by the Japanese Society of Chemotherapy and compared with those of oral cephem antibacterials, cefaclor, cefdinir, cefditoren, and cefcapene. In this study, remarkable change in the activity of CPDX was observed in Streptococcus pneumoniae and Haemophilus influenzae compared with the susceptibility in the studies before Banan was launched. This cause is considered to be the increase in the incidence of the following resistant strains: penicillin-intermediate S. pneumoniae (47.3%), penicillin-resistant S. pneumoniae (PRSP, 15.1%), and beta-lactamase-negative ampicillin-resistant (BLNAR) H. influenzae (24.0%), which were scarcely isolated in 1989 when Banan was launched. Other tested drugs also exhibited low activity against these resistant strains. However, CPDX showed comparatively good activity with MIC90 of 2 micrograms/mL against PRSP. Against methicillin-susceptible Staphylococcus spp., Streptococcus pyogenes, Streptococcus agalactiae, and Moraxella catarrhalis, CPDX also showed comparatively good activity with MIC90 of < or = 4 micrograms/mL, which was almost equal to that in the studies before its marketing. Against quinolones-resistant Neisseria gonorrhoeae, CPDX showed excellent activity with MIC90 of 0.5 microgram/mL. Against members of the family Enterobacteriaceae except for Citrobacter freundii, Enterobacter spp., Proteus vulgaris, and Morganella morganii, CPDX showed good activity. However, in Escherichia coli, Klebsiella spp. Proteus spp., and Providencia spp., there are some high-resistant strains to all tested drugs including CPDX. Against Peptostreptococcus spp., MIC90 of CPDX was 8 micrograms/mL and its MIC range was widely distributed from 0.03 to 32 micrograms/mL, which were similar to those in the studies before its marketing. In this study, CPDX showed the decrease in the activity against several species as did other drugs tested, but against most of species tested, CPDX maintained good activity. Furthermore, it is necessary to pay much attention to the trend of resistant strains.

An unusual abdominal mass in a renal transplant recipient

Renal transplant recipients are at increased risk of malignancy and infection. We present the case of a 72-year-old-man with recurrent bladder carcinoma, abdominal aortic aneurysm repair, and end-stage renal failure due to renovascular disease. He received a cadaveric renal allograft into his left iliac fossa, was given cyclosporin A, azathioprine, and prednisolone triple therapy immunosuppression, and had no rejection episodes. He presented four years post-transplantation with a two-year history of intermittent sweats and fevers. Previous episodes had been investigated with no firm diagnosis made. This time he had right iliac fossa pain of three weeks' duration. Examination revealed a tender mass. Investigations showed unchanged graft function, but elevated inflammatory indices. Ultrasonography and computed tomography detailed an infiltrating mass associated with the sigmoid colon, which colonoscopy failed to visualise. At laparotomy a 6-cm tumor was removed, with adherent sigmoid colon and bladder dome. Macroscopically the mass was an abscess, and microscopy found acute and chronic inflammatory giant cells and fibrillary masses suggestive of actinomycosis, with no malignancy. The patient recovered uneventfully on antibiotics. At six months' follow-up, examination, inflammatory markers, and radiographic imaging showed no evidence of recurrence. Twelve months later the patient died of rupture of his proximal abdominal aorta. There was no evidence of recurrence at postmortem examination. We conclude with a brief review of actinomycosis in transplant recipients.

[The influence of medicine to the expression of cell adhesion molecule in experimental otitis media with effusion]

OBJECTIVE

To study the influence of Cefaclor and Prednisonum to the expression of cell adhesion molecule in experimental otitis media with effusion (OME).

METHOD

SD rats models of OME were made using formalin killed nontypeable Hemophilus influenzae and the expression of adhesion molecules Mac-1 and L-Selectin was analysed by flow cytometry using white blood cell obtained by cardiac puncture in control, bacterial and medicine groups. The pathology of middle ear mucosa was investigated to understand the relationship between the expression of adhesion molecules and the pathology.

RESULT

It was found that the expression of adhesion molecules Mac-1 and L-Selection in bacteria group increased obviously with pathological change of the middle ear mucosa. Cefaclor and Prednisonum could decrease the expression of adhesion molecules and inhibited the leukocyte accumulation in the middle ear cavity though there was no significant differences except for the L-Selectin in the Cefaclor group between the bacteria group and the medicine group.

CONCLUSION

Dead bacteria in the middle ear may act as an antigen to induce the inflammatory response and effusion of the middle ear. The expression of adhesion molecules Mac-1 and L-Selectin is highly related to the inflammatory response. Cefaclor and Prednisonum may improve otitis media with effusion, which may related to the decreasing expression of Mac-1 and L-Selectin.

[Microbiological and clinical studies of Haemophilus influenzae isolated at Kitakyushu Municipal Medical Center from 1996 through 1999]

Epidemiological and microbiological studies were carried out using 575 strains of Haemophilus influenzae isolated from clinical specimens at Kitakyushu municipal medical center from January 1996 through December 1999. The strains isolated multiply were excluded. The strains of H. influenzae did not increase for 4 years, and were detected more in summer season, peaked in July, and less in winter season. Like the cases of Streptococcus pneumoniae, most (91.8%) of the strains was detected in the specimens from the respiratory tract, and also they were isolated mainly from infants under 4-years old (25.6%) and adults over 65-years old (24.2%) MICs of 7 antimicrobial agents, such as ampicillin (ABPC), sulbactam/ABPC, cefaclor, imipenem, panipenem, meropenem (MEPM), and levofloxacin (LVFX) were determined using broth microdilution methods. Among 575 strains of H. influenzae isolated from clinical specimens, 51 ABPC-resistant strains (8.9%) produced beta-lactamase, and 67 strains (11.6%) were beta-lactamase negative ampicillin resistant H. influenzae. The ABPC-resistant strains existed in 20.5%. Both of MEPM and LVFX showed excellent antimicrobial activity against H. influenzae including ABPC-resistant strains. Four cases of meningitis were reviewed. All of H. influenzae isolated possessed type b capsular antigen. All patients recovered by appropriate antimicrobial treatment. But one adult patient developed serious sequela.

Determination of antimicrobial activity of Cefaclor on common respiratory tract pathogens in Pakistan

OBJECTIVE

To determine the antimicrobial activity of Cefaclor against common respiratory tract pathogens isolated from patients in Pakistan.

SETTING

Department of Microbiology, Liaquat National Postgraduate Medical Centre, Karachi.

METHOD

A laboratory analysis was done on 466 isolates of respiratory tract pathogens collected from 13 laboratories from all over Pakistan. Antibiotic sensitivity test was done by Kirby Bauer disc diffusion method and MIC of Cefaclor was determined by 'E' test.

RESULT

Of the 163 Streptococcus pneumoniae, 87 Moraxella catarrhalis and 216 Haemophilus influenzae > 95% isolates were susceptible to Cefaclor. The MIC 90 of all these pathogens were < 2 ug.

CONCLUSION

Resistance of respiratory tract pathogens to the 2nd generation Cephalosporin, Cefaclor is very low. MIC 90 of Cefaclor against all three common respiratory tract pathogens is < 2 ug, which indicates that Cefaclor would be effective in more than 90% of cases infected with these bacteria.

[Activity of different antimicrobial agents against penicillin-resistant Streptococcus pneumoniae]

Since the first strains of penicillin-resistant Streptococcus pneumoniae were isolated in the 1960s, the rate of resistance has increased world- wide, though with geographic variations. Currently, the prevalence and patterns of antibiotic resistance in this microorganism vary widely from one country to another, as well as within in the same country. In our study we evaluated the in vitro susceptibility of 299 isolates of S. pneumoniae from patients with community-acquired respiratory tract infections from 1998-2000 to different antimicrobial agents. The following resistance results were obtained: 32.11% to penicillin, 4.35% to amoxicillin, 3.68% to amoxicillin-clavulanic acid, 69.9% to cefaclor, 32.44% to cefpodoxime, 34.11% to cefuroxime, and 24.41% to azithromycin. For cefixime and ceftibuten there are no NCCLS breakpoint criteria.

Desirable and undesirable immunotropic effects of antibiotics: immunomodulating properties of cefaclor

The effect exerted on complex immunoregulatory functions of the immune system is an important criterion when selecting an antibiotic. When assessing the effect of an antibiotic on the immune system, one should also take into consideration the existence of functional relationships between the immune system and the nervous and hormonal systems. Among these three systems, there are common factors that modify biological processes. This makes it possible for the antibiotic not only to interact directly with the elements of the immune system, but also to exert indirect influences on potential neurotropic and endocrinotropic effects of the drug. Besides highly effective bactericidal activity, cefaclor demonstrates the ability to exert a favorable effect on some of the specific and non-specific immune responses and immunoregulation mechanisms, which may be important from a clinical point of view. Cefaclor enhances phagocytosis and bactericidal activity of granulocytes and macrophages, and favorably modifies the cooperation of monocytes and T lymphocytes. In this way, it corrects, both in vivo and in vitro, the immunoregulatory disturbances induced and aggravated by an infection. This effect is reflected by an improvement in the impaired immunoregulating activity of T lymphocytes, and is manifest both as an increase in suppressive activity and a correction of the monokine level ratio in relation to the decrease of proinflammatory monokine IL-1 and a relative increase of antiinflammatory IL-1ra. By normalizing the disturbed immunoregulation mechanism, cefaclor enhances the protective potential of the immune reaction while it also reduces the risk of immunogenic clinical complications such as persistent inflammatory conditions and allergic and/or autoaggressive responses. Such immunomodulating properties of cefaclor may be useful in the clinical treatment of patients with immune disorders leading to chronic inflammation and secondary allergic or autoaggressive reactions.

Clinical and pro-host effects of cefaclor in prophylaxis of recurrent otitis media in HIV-infected children

The aim of this study was to evaluate the efficacy of cefaclor in the prophylaxis of recurrent acute otitis media (AOM) in human immunodeficiency virus (HIV)-infected children. The study was carried out in children born between 1 January 1986 and 31 December 1996 who had been vertically HIV infected Patients who had experienced recurrent AOM between October 1997 and March 1998 (period 1) were eligible for the trial. Recurrent AOM was defined as the occurrence in the same patient of three or more episodes of AOM within 6 months of the observation period. Patients recruited for this trial received cefaclor at a dose of 20 mg/kg once daily for 6 months between April and September 1998 (period 2). Clinical observation was carried out in periods 1 and 2 and for the first 6 months after prophylaxis, i.e. October 1998 - March 1999 (period 3). Natural killer-cell activity, phagocytosis and myeloperoxidase activity were determined before and at the end of the prophylactic period. For each period, CD4-cell count measurement and CD4-positive cell class were recorded. Seventeen children were recruited for this trial. No significant differences were observed in natural killer-cell activity between periods 1 and 2, nor were any significant differences observed in CD4-positive cell class or CD4-positive cell count between the three periods. However, cefaclor administration was associated with a reduction in the number of AOM episodes in 100% of cases and a mean increase in myeloperoxidase activity in 57% of cases. This suggests that cefaclor may be useful in the prophylaxis of recurrent AOM in HIV-infected children.

[The frequency of Streptococcus pneumoniae strains and sensitivity surveillance for several antibiotics in Gifu Prefecture]

The frequency and the antibacterial sensitivity of Streptococcus pneumoniae strains isolated from 6 key hospitals (in 5 areas) and 1 otorhinolaryngology clinic in Gifu Prefecture from February to March, 1999, were investigated with several antibiotics. A total of 128 strains of Streptococcus pneumoniae were isolated throughout the study: 47 strains (36.7%) of penicillin-susceptible S. pneumoniae (PSSP), 51 strains (39.8%) of penicillin-intermediate S. pneumoniae (PISP), and 30 strains (23.4%) of penicillin-resistant S. pneumoniae (PRSP); the resistant bacteria being relatively prominent. In these hospitals, PSSP was isolated by 38.8% in all the key hospitals and by 30% in the otolaryngology clinic with almost no discernible difference. PISP was isolated by 63.3%, higher in the otolaryngology clinic and PRSP by 28.6%, higher in the key hospitals conversely. The MIC90s in PISP and PRSP were determined with the antibiotics. In result, only cefditoren (CDTR) showed favorable antibacterial activities with the MIC90 of 0.78 microgram/ml among penicillins or oral cephems. The MIC90s of carbapenems such as imipenem (IPM), meropenem (MEPM), and panipenem (PAPM) were less than 0.39 microgram/ml; particularly, PAPM showed the highest antibacterial activities. Among new quinolones such as tosufloxacin (TFLX), levofloxacin (LVFX), sparfloxacin (SPFX), and ciprofloxacin (CPFX), TFLX showed the highest antibacterial activities with the MIC90 of 0.39 microgram/ml. Other agents showed very low antibacterial activities as the MIC90s were 25 micrograms/ml in minocycline (MINO) and more than 100 micrograms/ml in clarithromycin (CAM) and clindamycin (CLDM).

Cefaclor, a cephalosporin antibiotic, delays gastric emptying rate by a CCK-A receptor-mediated mechanism in the rat

Studies in vitro suggest that cephalosporin antibiotics release the gut hormone cholecystokinin. Cholecystokinin is known to inhibit gastric emptying. Here we examine the effects of cefaclor on gastric emptying and intestinal motility. Male Sprague-Dawley rats were fitted with gastric cannulas. Following a 3-week recovery, the rate of gastric emptying of saline, peptone (4.5%) or cefaclor was determined after instillation into the gastric cannula, while intestinal transit was measured by using the propagation of arabic gum + charcoal mixture given intraduodenally. Gastric emptying of saline was significantly delayed by the addition of cefaclor (3, 10, 30 or 100 mM). The CCK-A antagonist SR-27897B (1 mg kg(-1), i.p.) reversed the delay induced by 10 mM cefaclor, whereas the CCK-B antagonist CI-988 (1 mg kg(-1), i.p.) had no significant effect. In capsaicin-treated rats, 10 mM cefaclor emptied more rapidly than in vehicle-treated animals. Thirty-minute intestinal transit was increased at 30 and 100 mM of cefaclor, while the gastric acid secretion following cefaclor instillation was no different than the group which received saline. The cephalosporin antibiotic cefaclor appears to be a potent stimulant of CCK release from gut endocrine cells, resembling the effects of peptone. Cefaclor delays gastric emptying via capsaicin-sensitive afferent pathways, which involve CCK-A receptor interaction.

The efficacy and safety of cefaclor in respiratory infections amongst Pakistani children

PURPOSE

To evaluate the efficacy and safety of Cefaclor in respiratory tract infections amongst Pakistani children.

PATIENTS AND METHODS

Multicenter, open label and non-comparative study was done to evaluate the response in terms of symptoms (In vivo) and bacterial cultures (In Vitro) to Cefaclor amongst children with respiratory tract infection between the ages 2 months to 12 years. Each patient was asked to visit the doctor on three occasions i.e., Day 0 (Initial evaluation prior to commencement of study), Day 4 (During therapy assessment and confirmation of compliance) and Day 10 (End of therapy assessment and compliance evaluation). Representative swab specimens (Throat swabs, Ear swabs or Sputum) were collected from the infected site on day 0 and day 10 for culture and sensitivity. Patients were also assessed by the evaluators on each visit in terms of clinical symptomatic response and information collected was documented on a prescribed data base form.

RESULTS

A total of 160 patients were enrolled in the study, of whom 15 were lost to follow-up between the first and second visit and a further 38 were lost by the 3rd visit. Thus 107 patients completed the study as per protocol. Otitis media and Upper respiratory tract infection were the predominant ailments amongst the cases enrolled. One or more bacteria were isolated in 75 (46%) instances, the maximum number of isolates being from ear swabs of Otitis media patients. Beta haemolytic Streptococcus (group A,C,F,G) seen in 18 cases was the most common pathogen reported followed by Staphylococcus aureus, H. influenzae and Streptococcus pneumoniae in 13,12 and 11 cases respectively. Sensitivity of Cefaclor for bacteria commonly seen in the respiratory tract was greater than 90% in most of the cases. Evaluation of the 42 culture proven cases for patients who completed the study showed that Cefaclor had a 93% efficacy for indicated bacteria and 54% for non-indicated bacteria. In Vivo analysis of Cefaclor (i.e. on the basis of symptomatic response) showed that 96% cases had a symptomatic response by the second visit, which improved to 97% by the third visit. Only 15 non-serious adverse events were observed in 160 patients, none of the cases necessitated discontinuation of drug. Mild gastrointestinal symptom was the most common adverse event reported.

CONCLUSION

Cefaclor was found to be a safe and efficacious drug in the treatment of bacterial respiratory tract infections amongst Pakistani children.

Assessment of the susceptibility of Streptococcus pneumoniae to cefaclor and loracarbef in 13 countries

Between July 1998 and July 1999, 2,644 clinical isolates of Streptococcus pneumoniae were collected from 27 study centers in 13 countries and their susceptibilities to penicillin, cefaclor and loracarbef were determined by E-test" (AB BIODISK, Solna, Sweden). Overall, 96.3% of isolates were penicillin-susceptible (79.8%) or -intermediate (16.6%) (MIC, < or = 1 microg/ml). Rates of penicillin-resistant S. pneumoniae isolation varied widely and were highest in the study centers tested in New Zealand (10.9%), Canada (10.0%), Mexico (9.1%) and the United States (5.1%). Low rates of penicillin-resistance were found in the study centers tested in Russia (0%), Turkey (0%), Brazil (0.5%), Germany (0.6%), Philippines (1.6%), Italy (2.1%), United Kingdom (2.3%), Australia (3.0%) and Poland (3.1%). Using recently published NCCLS interpretative breakpoints (M100-S10, 2000), 87.2% (median) of all isolates tested were cefaclor-susceptible and 87.8% (median) of all isolates tested were loracarbef-susceptible. Of the penicillin-susceptible S. pneumoniae isolates, 99.5% were susceptible to both cefaclor and loracarbef. Susceptibility to cefaclor and loracarbef was also retained by 30.8% and 32.9% of penicillin-intermediate isolates, respectively. These findings are in contrast to recent publications reporting lower cefaclor and loracarbef activities using non-validated interpretative criteria. In conclusion, rates of penicillin resistance among recent clinical isolates of pneumococci remain low in many centers worldwide. Cefaclor and loracarbef demonstrated excellent in vitro activity against recent clinical isolates of penicillin-susceptible and many isolates of penicillin-intermediate S. pneumoniae.

Susceptibility of Streptococcus pneumoniae and Haemophilus influenzae to cefditoren, and provisional interpretive criteria

In vitro cefditoren antimicrobial activity was tested by broth microdilution and disk diffusion methods against 300 Streptococcus pneumoniae and 299 Haemophilus influenzae isolates. MICs were also determined for three comparison drugs. The MICs of cefditoren were very comparable to those of cefotaxime against both species. If penicillin-resistant pneumococci are to be considered not susceptible to cefditoren, the tentative MIC breakpoints for cefditoren of < or = 0.25 microg/ml for susceptible and > or 1.0 microg/ml for resistant could be selected. With these breakpoints, all penicillin-susceptible pneumococci were cefditoren-susceptible, as were 85% of penicillin-intermediate strains. Provisional zone diameter breakpoints would be > or = 26 mm for susceptible and < or = 20 mm for resistant. If penicillin-resistant pneumococcal infections are shown to clinically respond to cefditoren therapy, then a susceptible MIC breakpoint of < or = 1.0 microg/ml would be appropriate, with a corresponding zone diameter breakpoint of > or = 21 mm. A susceptible MIC breakpoint of < or = 0.5 or < or = 1.0 microg/ml is appropriate for H. influenzae, but lack of correlation between cefditoren MICs and disk diffusion zone diameters when testing H. influenzae leads us to make no recommendations at this time regarding cefditoren disk tests for H. influenzae.

E test for studying in vitro activity of seven antimicrobial agents against penicillin-susceptible and penicillin-resistant pneumococci

OBJECTIVE

To evaluate the comparative activity of seven oral antimicrobial agents against 100 strains of Streptococcus pneumoniae (S. pneumoniae).

METHODS

Total 100 strains of S. pneumoniae were collected from general hospitals in Beijing from June 1996 to June 1997. E test method was used to detect the minimum inhibitory concentration (MIC) values of the following seven drugs against S. pneumoniae: penicillin, amoxicillin/clavulanate, cefaclor, cefuroxime, ceftriaxone, azithromycin and ofloxacin. The breakpoint of susceptibility categories was defined according to NCCLS.

RESULTS

74% of isolates were susceptible (S, MIC 0.06 mg/L) to penicillin, and 5% were penicillin resistant (R, MIC 2 mg/L). The intermediately resistant (I, MIC 0.1-1 mg/L) rate to penicillin was 21%. The total rates of R or I were 26% for penicillin, 6% for both amoxicillin/clavulanate and ceftriaxone, 9% for cefuroxime, 66% and 68% for azithromycin and ofloxacin respectively. Overall 94%, 94% and 91% of the pneumococcal isolates were susceptible to amoxicillin/clavulanate, ceftriaxone and cefuroxime respectively. S. pneumoniae was highly resistant to azithromycin tested as a representative of macrolides (MIC50 and MIC90 both > 256 mg/L, R rate 66%), and had a highly intermediately resistant rate to ofloxacin (I rate 62%).

CONCLUSIONS

Our data suggest that in vitro activity of oral amoxicillin/clavulanate was as good as ceftriaxone and cefuroxime. It can be considered as an alternative compound in the treatment of community acquired pneumoniae and other respiratory tract infections caused by multiresistant S. pneumoniae.

Antimicrobial activity and in vitro susceptibility test development for cefditoren against Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus species

Cefditoren, a third generation orally administered aminothiazolyl cephalosporin, has demonstrated bactericidal activity against many Gram positive and negative bacterial pathogens and stability against clinically important beta-lactamases. Cefditoren was compared to cefaclor, cefixime, and penicillins against 1 435 recently isolated strains of streptococci (312 Streptococcus pneumoniae, 165 viridans group streptococci, 142 beta-haemolytic streptococci), Haemophilus influenzae (521 strains), and Moraxella catarrhalis (295 strains). Streptococcus pneumoniae and viridans group streptococci had penicillin nonsusceptible rates of 37.8 and 35.8%, respectively. Cefditoren (MIC(90) in microg/ml/% susceptible) activity against all tested H. influenzae (0.03/100) and M. catarrhalis (0.06-0.5/100) was comparable to cefixime and significantly greater than cefaclor. Cefditoren (MIC(90), 0.5 microg/ml) was 4- to 128-fold more active than comparison beta-lactams against the pneumoococci and was the most potent beta-lactam (including penicillin) versus beta-haemolytic streptococci. Cefditoren pharmacokinetics demonstrate a T(1/2) of 1.5-2 h and C(max) values of 2.8 and 4.6 microg/ml, respectively with 200 or 400 mg doses of cefditoren pivoxil; plasma concentrations exceed 1 microg/ml for 4 to 6 hours (33-50% of dosing interval). Consequently, a susceptible MIC of </= 1 microg/ml or </= 2 microg/ml was proposed with zone diameter correlates of >/= 18 and >/= 15 mm (5-microg disk) for all cited fastidious species tested. Categorical agreement between MIC and disk tests was 94.6 to 100% with a correlation coefficient (r) range of 0.50 to 0.90 for streptococci. H. influenzae intermethod comparison results using the same interpretive criteria were in complete agreement, but exhibited a low r = 0.39. Cefditoren clearly possesses the most potent activity among currently studied oral cephalosporins or penicillin against commonly isolated bacterial pathogens causing bronchitis, pneumonia, sinusitis, or pharyngitis and was active against nearly all penicillin-resistant streptococci at </= 0.5 microg/ml. Expanded clinical investigations seem warranted.

Presence of ROB-1 beta-lactamase correlates with cefaclor resistance among recent isolates of Haemophilus influenzae

beta-Lactamase production in Canadian isolates of Haemophilus influenzae has remained relatively constant (25-35%) over the last decade despite increasing cefaclor resistance (MIC >/= 32 mg/L). TEM (294/324, 90.7%) and ROB-1 (30/324, 9.3%) prevalence rates among 324 isolates of H. influenzae obtained from across Canada in 1997-1998 were similar (P > 0.05) to previously published reports. However, 66. 7% (26/39) of cefaclor-resistant isolates were ROB-1-positive (P < 0. 001) and the remaining four ROB-1-positive isolates were cefaclor-intermediate (MIC 16 mg/L). Susceptibilities to loracarbef (P < 0.001) and cefprozil were also reduced in the presence of ROB-1 while the activities of cefuroxime, cefotaxime, cefixime and imipenem were similar in both TEM- and ROB-1-positive solates.

Interrelationship between the pharmacokinetics and pharmacodynamics of cefaclor advanced formulation in patients with acute exacerbation of chronic bronchitis

Cefaclor advanced formulation (cefaclor AF) is an extended-release form of the oral cephalosporin cefaclor. When cefaclor AF 750 mg twice-daily and cefaclor immediate release 500 mg three-times-a-day are compared there is a skew to the right of the pharmacokinetic profile and higher levels are achieved. Based on this pharmacokinetic finding, we examined the relationship between the bacterial susceptibility to cefaclor (MIC), the achieved cefaclor AF serum and sputum concentrations, and in vivo eradication of the bacteria in 36 patients with acute exacerbations of chronic bronchitis. The mean peak concentrations in serum and sputum 5 h after administration were 8.6 microg/ml (95% CI: 8.1 microg/ml - 9.1 microg/ml) and 1.5 microg/ml (95% CI: 1.4 microg/ml - 1.7 microg/ml), respectively. Cefaclor was always detectable 8 h after administration. At post therapy, treatment was successful in 31 (86.1%) patients. Cefaclor concentrations in serum persisted above the MIC for more than 40% of dosing interval in 31 subjects, and those in sputum in 24 patients. Treatment was successful in all subjects with percent of time above the MIC in serum of >40%, whereas the time that levels in sputum stayed above the MIC was not the pharmacodynamic parameter that correlated best with therapeutic efficacy for cefaclor. Our data demonstrate that when cefaclor AF is dosed twice-daily, the in vivo pharmacodynamic susceptibility breakpoint is 8 microg/ml. The good activity and pharmacokinetics of cefaclor AF provide serum concentrations higher than the MIC of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis for more than 40% of the validated dosing interval. Therefore, it might be considered for first choice treatment of acute exacerbations of chronic bronchitis.

Control of c-fos expression in STC-1 cells by peptidomimetic stimuli

Enteroendocrine cells respond to nutrient and non-nutrient stimuli in the gut lumen. The intestinal hormone cholecystokinin (CCK) is secreted in response to luminal fatty acids, amino acids, peptides and proteins. The peptidomimetic cephalosporins have been reported to provide model, stable, compounds with similar secretagogue activity to peptide. Putative luminal stimuli also influence transcriptional activity in enteroendocrine cells, but the mechanisms are uncertain. In the present study we have investigated the control of c-fos expression in STC-1 cells (an enteroendocrine cell line). Peptidomimetics stimulated calcium-dependent release of CCK, and increased intracellular calcium, phosphorylation of p42/44 mitogen-activated protein kinase (MAP kinase) and c-fos mRNA abundance. Hypotonic stress also increased p42/44 MAP kinase phosphorylation and c-fos mRNA, but not CCK release. The increase in c-fos mRNA was strikingly potentiated by peptidomimetics in hypotonic medium. Increased c-fos expression, but not CCK release, was suppressed by the MAP kinase (MEK) inhibitor PD98059, and by the tyrosine kinase inhibitor genistein. We conclude that in STC-1 cells, peptidomimetics act through the p42/44 MAP kinase pathway to increase c-fos expression but not exocytosis. Moreover, a putative non-nutritive stimulus, hypotonic stress, may interact with this pathway to enhance c-fos expression, independently of hormone release.

Macrolide antibiotics inhibit nitric oxide generation by rat pulmonary alveolar macrophages

There is evidence that macrolide antibiotics are effective in the treatment of chronic airway inflammatory diseases, probably through actions other than their antibacterial properties. In order to determine whether macrolides affect the nitric oxide-generating system in the respiratory tract, rat pulmonary alveolar macrophages (PAMs) were studied in vitro. The release of NO was assessed by direct measurement with a specific amperometric sensor for this molecule, and the expression of type II NO synthase (NOS) messenger ribonucleic acid (mRNA) was determined by Northern blotting. Incubation of PAMs with lipopolysaccharide from Escherichia coli and recombinant human interferon-gamma caused release of NO, which was accompanied by induction of type II NOS mRNA. The release of NO was reduced by coincubation of cells with the macrolides erythromycin, clarithromycin and josamycin in a concentration-dependent manner, the maximal inhibition being 73+/-10, 81+/-6 and 84+/-9%, respectively, but was not altered by amoxycillin or cefaclor. These macrolides likewise inhibited the induction of type II NOS mRNA, whereas no inhibitory effects were observed with amoxycillin or cefaclor. These results suggest that macrolide antibiotics specifically inhibit type II NO synthase gene expression and consequently reduce NO production by rat pulmonary alveolar macrophages, which might result in attenuation of airway inflammation.

[Investigation of the antibacterial activity of faropenem against Streptococcus pneumoniae]

We evaluated the antibacterial activity of faropenem against penicillin-susceptible Streptococcus pneumoniae (PSSP) and penicillin-resistant S. pneumoniae (PRSP). It was shown that the minimum inhibitory concentrations against 90% of the clinically isolated strains (MIC90) of faropenem, penicillin G, cefaclor, cefcapene, and cefditoren against PSSP were 0.032, 0.063, 2, 0.25, and 0.125 micrograms/ml, respectively. While those against PRSP were 0.5, 2, > 128, 1, and 1 micrograms/ml, respectively. Furthermore, we evaluated the bactericidal activity, at the level of 1/4, 1, and 4 MIC, of faropenem and the above four reference antibacterial agents against PSSP and PRSP. Against PSSP No. 127, a sensitive strain to both penicillin G and cefcapene, faropenem showed almost the same bactericidal activity as those of reference agents. Against PSSP No. 108, a penicillin-susceptible and cephem-resistant strain, and PRSP No. 57, a resistant strain to both of penicillin and cephem, faropenem of 1 MIC showed bactericidal activity, but reference agents needed 4 MIC to show bactericidal activity.

[In vitro activities of levofloxacin and other antibiotics against fresh clinical isolates]

In this study, the in vitro activity of levofloxacin (LVFX) against 1,020 fresh bacterial clinical isolates was compared with the activities of a range of ofloxacin, ciprofloxacin (CPFX), ampicillin (ABPC), cefaclor, cefpodoxime, methicillin and benzylpenicillin. The clinical isolates except Vibrio cholerae were collected in Japan during 1998 from patients with infectious diseases. MICs were determined using the agar dilution method according to the recommendations by the Japan Society of Chemotherapy. Some isolates of methicillin resistant Staphylococcus aureus (MRSA) and coagulase negative Staphylococcus were resistant to fluoroquinolones, but the MIC50 of LVFX against MRSA was 6.25 micrograms/ml. LVFX was the most active against MRSA among the antibiotics tested. Most of Staphylococcus epidermidis strains were susceptible to the fluoroquinolones. LVFX showed greater activity against all streptococci strains compared with fluoroquinolones tested. In particular, all Streptococcus pneumoniae strains including PRSP were susceptible to LVFX at < or = 1.56 micrograms/ml. Among Enterococcus, ABPC showed superior activity against Enterococcus faecalis but many isolates of Enterococcus species were resistant to ABPC. LVFX was more active against to these Enterococcus species compared with other fluoroquinolones. On the other hand, LVFX and CPFX showed similar activity against isolates of Enterobacteriaceae. CPFX had an MIC50/90 of 0.20, 0.39 microgram/ml and LVFX showed an MIC50/90 of 0.78, 1.56 micrograms/ml against Pseudomonas aeruginosa. LVFX (MIC50/90 0.10, 0.20 microgram/ml) was more active against Acinetobacter species than CPFX (MIC50/90 0.10, 0.39 microgram/ml). Haemophilus influenzae, Branhamella (Moraxella) catarrhalis and V. cholerae were inhibited by low concentration of the fluoroquinolones tested. The MIC90 of LVFX and CPFX were < or = 0.10 microgram/ml against above three species. Some isolates of Neisseria gonorrhoeae and Campylobacter species were moderately resistant to the fluoroquinolones tested but the MIC50 of LVFX and CPFX were < or = 0.39 microgram/ml. Among anaerobes, Propionibacterium acnes was more susceptible than Peptostreptococcus species, and the MIC90 of beta-lactams and fluoroquinolones tested were < or = 0.78 microgram/ml. In conclusion, this study, performed on large number of strains, confirmed an excellent and wide spectrum antibacterial activity of LVFX compared with the fluoroquinolones and beta-lactams tested. And our results suggest that LVFX may be useful in the treatment of various bacterial infections.

Structure-function studies of Ser-289 in the class C beta-lactamase from Enterobacter cloacae P99

Site-directed mutagenesis of Ser-289 of the class C beta-lactamase from Enterobacter cloacae P99 was performed to investigate the role of this residue in beta-lactam hydrolysis. This amino acid lies near the active site of the enzyme, where it can interact with the C-3 substituent of cephalosporins. Kinetic analysis of six mutant beta-lactamases with five cephalosporins showed that Ser-289 can be substituted by amino acids with nonpolar or polar uncharged side chains without altering the catalytic efficiency of the enzyme. These data suggest that Ser-289 is not essential in the binding or hydrolytic mechanism of AmpC beta-lactamase. However, replacement by Lys or Arg decreased by two- to threefold the kcat of four of the five beta-lactams tested, particularly cefoperazone, cephaloridine, and cephalothin. Three-dimensional models of the mutant beta-lactamases revealed that the length and positive charge of the side chain of Lys and Arg could create an electrostatic linkage to the C-4 carboxylic acid group of the dihydrothiazine ring of the acyl intermediate which could slow the deacylation step or hinder release of the product.

[Selection of antibacterial therapy for treatment of infections in elderly patients]

Examination of 60 elderly outpatients with lower respiratory tract infections (LRTI) revealed that 73 per cent of the patients isolated the pathogen associations and only 27 per cent isolated the monocultures. Grampositive cocci including Streptococcus pneumoniae were isolated from 70 per cent of the patients, Haemophilus influenzae and H.parainfluenzae were isolated from 20 per cent of the patients and Acinetobacter spp., Citrobacter spp., Enterobacter spp., Proteus spp. and Pseudomonas aeruginsa were isolated from 10 per cent of the patients. The patients were treated with ciprofloxacin, cefaclor or amoxycillin/clavulanic acid. Ciprofloxacin proved to be the most efficient agent. The regimens of the ofloxacin use in a dose of 400 mg orally once a day or in a dose of 200 mg intravenously twice a day for 2-4 days followed by the oral use for 6-8 days in the treatment of 24 patients with LRTI hospitalized into a therapeutic unit were compared. it was shown (pharmacokinetically as well) that the regiment with the drug use in the single dose was more efficient. Lomefloxacin was suggested to be the most advantageous drug in the treatment of elderly patients with LRTI because of its easy use, practically no dependence of the pharmacokinetics on the patient age and almost no nephrotoxic action.

The effects of the morphological response of Enterobacteriaceae to cephalosporins on PAE and CERT

PAE and CERT values of cefaclor, loracarbef and cefuroxime (0.1-100 x MIC) were established for 8 E. coli, 3 K. pneumoniae and 2 P. mirabilis isolates. Cell enumeration was by impedance (IMP) monitoring in combination with either bioluminescence (BIOL) or viable counting (VC). Morphology was determined by interference contrast microscopy. After 2 h exposure to cefaclor, loracarbef and cefuroxime; concentration-dependent differences in counts were seen by BIOL and VC, varying from a mean value of 0.07 x log10 after exposing the P. mirabilis isolates to 0.1 x MIC cefaclor to a mean value of 2.24 x log10 after exposing the E. coli strains to 100 x MIC cefuroxime. Higher concentrations gave rise to fragile morphological forms including spheroplasts and lower concentrations to less fragile forms such as long bacilli. The longest PAE and CERT values were obtained after exposing the E. coli strains to 100 x MIC cefaclor with mean values of 4.07 and 4.87 h, respectively. Corresponding values were PAE and CERT values of 2.17 and 2.60 h for 100 x cefuroxime and 3.45 and 2.91 h for 100 x MIC loracarbef. By the Student's t-test, PAE values determined by IMP/BIOL and IMP/VC were found to be significantly different, whereas CERT values were found not to be significantly different. PAE and CERT are concentration dependent and vary with specific antibiotic/organism combinations.

A comparative investigation of the restorative effects of roxithromycin on neutrophil activities

The effects of roxithromycin, a macrolide antibiotic, on neutrophil activities were investigated in six seriously handicapped patients with severe mental retardation. Neutrophil activities were evaluated by flow cytometry using a heparinized blood analysis method. All six patients showed decreased levels of neutrophil phagocytosis, intracellular killing, and CD11b expression. Treatment with roxithromycin in vitro selectively restored the decreased phagocytic and bactericidal activities of neutrophils in these patients. There was no significant restorative effect with cefaclor, ofloxacin, or aztreonam. These results suggest the need to consider therapeutic effects of antibiotics on neutrophil functions in patients at increased risk for bacterial infections due to decreased neutrophil activities.

Comparison of cefaclor and cefuroxime axetil in the treatment of acute otitis media with effusion in children who failed amoxicillin therapy

This trial compared the efficacy and safety of a 10-day treatment course of cefaclor and cefuroxime axetil in the treatment of acute otitis media with effusion in children who failed therapy with amoxicillin. This was an investigator-blind, randomized, parallel treatment group study. To be included, patients must have received treatment with a standard clinical regimen of amoxicillin for at least 48 hours and not more than 10 days, with the last dose within 72 hours of randomization. Patients who met the entry criteria were randomly assigned to one of two antibiotic treatment groups. Cefaclor and cefuroxime axetil suspensions were administered twice daily for a total daily dose of 40 mg/kg and 30 mg/kg, respectively. Physical examination, pneumatic otoscopy and tympanogram were performed to evaluate efficacy to therapy. Therapeutic equivalence was established by ruling out a difference (cefaclor minus cefuroxime axetil) of 15% in percentages of clinical success (cure plus improvement). Safety evaluation was performed by assessment of clinical adverse events. In the intent-to-treat analysis post-therapy (1-6 days after completion of therapy), 96 of 104 (92.3%) cefaclor-treated patients had clinical success compared to 90 of 101 (89.1%) cefuroxime axetil patients. The 95% confidence limits on the difference between proportions of favorable outcomes (cefaclor minus cefuroxime axetil) was from -4.8% to +11.2%. At termination of the study (day 10-16 after completion of therapy), 86 of 104 (82.7%) cefaclor patients and 84 of 101 (83.2%) cefuroxime axetil patients had favorable clinical outcomes (95% confidence interval: -10.8% to +9.9%). Thirty-two (30.8%) of the 104 patients in the cefaclor treatment group reported at least one adverse event, with rhinitis reported in 9 (8.7%) patients and cough increased in 7 (6.7%) patients. Thirty-six (35.6%) of the 101 patients in the cefuroxime axetil treatment group reported at least one event, with diarrhea reported in 11 (10.9%) of patients and rhinitis in 10 (9.9%) patients. Cefaclor and cefuroxime axetil were equally effective in the treatment of patients with acute otitis media with effusion who had failed therapy with amoxicillin. Significantly fewer patients treated with cefaclor reported diarrhea, which is the most frequently reported adverse event in children treated with antibiotics for this disease.

Cefaclor: a contemporary look at susceptibility of key pathogens from around the globe

The orally administered cephalosporin antibiotic, cefaclor, has been available for clinical use in many countries since 1979. Because widespread antibiotic use is often cited as a factor in the emergence of bacterial resistance to antibiotics, we sought to determine the degrees of resistance to cefaclor expressed by key pathogens recently isolated in 10 countries widely distributed around the world. Using the E-test, minimal inhibitory concentrations (MIC) were determined for cefaclor and several comparator antibiotics against approximately 700 fresh clinical isolates of each of six bacterial species. The results demonstrated that > 90% of Haemophilus influenzae (beta-lactamase producing and non-producing), Haemophilus parainfluenzae (beta-lactamase producing and non-producing), Moraxella catarrhalis (> 90% beta-lactamase producing), and methicillin-susceptible Staphylococcus aureus, and 85% of Escherichia coli were susceptible to cefaclor at the NCCLS interpretive breakpoints. MIC distributions showed that there has been no change in the activity of cefaclor against penicillin-susceptible strains of Streptococcus pneumoniae since 1977.

3-trifluoromethylcarbacephems: synthesis of broad spectrum antibacterial compounds

The enhanced stability of the carbacephem nucleus over the corresponding cephalosporin nucleus has allowed the synthesis of 7-arylglycyl-3-trifluoromethyl-carbacephems. These unique carbacephems possess broad spectrum activity and high stability to both plasmid and chromosomally mediated beta-lactamases.