Effects of AC-1370, a new semisynthetic cephalosporin, on phagocyte functions

Discovery of quaternized pyridine-thiazole-ruthenium complexes as potent anti-Staphylococcus aureus agents

Quaternization of ruthenium complexes may be a promising strategy for the development of new antibiotics. In response to the increasing bacterial resistance, we integrated the quaternary amine structure into the design of ruthenium complexes and evaluated their antibacterial activity. All the ruthenium complexes showed good antibacterial activity against the tested Staphylococcus aureus (S. aureus). Ru-8 was the most effective antibacterial agent that displayed excellent antibacterial activity against S. aureus (MIC = 0.78-1.56 μg/mL). In vitro experiments showed that all nine ruthenium complexes had low hemolytic toxicity to rabbit erythrocytes. Notably, Ru-8 was found to disrupt bacterial cell membranes, alter their permeability, and induce ROS production in bacteria, all the above leading to the death of bacteria without inducing drug resistance. To further explore the antibacterial activity of Ru-8in vivo, we established a mouse skin wound infection model and a G. mellonella larvae infection model. Ru-8 exhibited significant antibacterial efficacy against S. aureus in vivo and low toxicity to mouse tissues. The Ru-8 showed low toxicity to Raw264.7 cells (mouse monocyte macrophage leukemia cells). This study indicates that the ruthenium complex ruthenium quaternary was a promising strategy for the development of new antibacterial agents.

Discovery of Quaternized Pyridine-Thiazole-Pleuromutilin Derivatives with Broad-Spectrum Antibacterial and Potent Anti-MRSA Activity

The quaternization of compounds has emerged as a promising molecular design strategy for the development of antibiotics. Herein, we report the design, synthesis, antibacterial activities, and structure-activity relationships of a series of novel pleuromutilin derivatives containing a quaternary amine C-14 side chain. Most of these derivatives exhibited broad-spectrum antibacterial activity against the tested bacteria. 10b was the most effective antibacterial agent that displayed excellent antibacterial activity against five clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, remarkable antimycoplasma activity, rapid bactericidal effects, and a strong ability to damage bacterial biofilms. Further mechanistic studies indicated that 10b destroyed bacterial cell membranes to exert its antibacterial effects. Moreover, 10b exhibited high survival protection and potent in vivo antibacterial efficacy (ED₅₀ = 4.94 mg/kg) in a mouse model of systemic MRSA infection. These findings suggest that 10b is a promising candidate for the treatment of multi-drug-resistant infectious diseases, especially MRSA infections.

Microwave assisted synthesis of some new thiazolopyrimidine and pyrimidothiazolopyrimidopyrimidine derivatives with potential antimicrobial activity

Background and objective

A series of thiazolopyrimidine derivatives have been synthesized via multicomponent reaction and tested for biological activities. This research aims to develop a new synthetic method of poly fused pyrimidines under microwave irradiation. 6-Amino-4-aryl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitriles reacted with bromomalono-nitrile to give 3,7-diamino-5-aryl-5H-thiazolo[3,2-a]pyrimidine-2,6-dicarbonitrile more willingly than the isomeric 7H-thiazolo[3,2-a]pyrimidines. Thiazolopyrimidine derivatives reacted with carbon disulphide to produce 11-aryl-11H-1,2,3,4,7,8,9,10-octahydropyrimido[4″,5″:4′,5′]thiazolo[3′,2′-a]pyrimido[4,5-d]pyrimidine-2,4,8,10-tetrathione. The above mentioned reactions were established by using both conventional methods and microwave-assisted irradiation.

Conclusion

This work provides a new method for preparing poly fused pyrimidines. The microwave-assisted technique is preferable due to the yield enhancements attained, time saving, and environmental safety reactions. The newly prepared compounds were verified for their antimicrobial activities. Also, the absorption and emission of some of the prepared compounds were studied.

Immunopharmacology of oral betalactams

Among the oral beta-lactam antibiotics only cefaclor has demonstrated a consistent in vitro and in vivo immunopharmacological effect which favors phagocytic chemotaxis and antimicrobial potential by inducing a T-helper 1 or pro-inflammatory response. Together with cefpimizole, cefaclor significantly reduces the minimum bactericidal concentration (MBC) against some bacterial species when cultured together with a suspension of polymorphonuclear leukocytes, as opposed to some other oral beta-lactams, co-amoxiclav and cefixime, which do not show this effect. The pro-inflammatory component of cefaclor's activity explains the clinical success of this antibiotic in a high percentage of cases, even when laboratory tests indicate in vitro resistance by the pathogen.

Effect of antimicrobial agents on chemotaxis of polymorphonuclear leukocytes

The effect of antimicrobial agents on polymorphonuclear (PMN) chemotaxis was investigated. No significant effect was obtained in vitro with penicillins, cephems, macrolides, aminoglycosides or quinolones by the agarose plate method. However, chemotaxis was inhibited at 100 micrograms/ml or less of minocycline and doxycycline. The inhibitory effect on chemotaxis is considered to be due to chelation of Ca-ions by minocycline or doxycycline. The chelation reduced the concentrations of Ca-ions in the PMNs. The chemotactic index of minocycline increased when CaCl2 or A23187 were given in combination. Our findings indicate that a small number of the short lamellipodia were observed in PMNs preincubated with minocycline or doxycycline and these two agents affected the movement of PMNs morphologically.

In vitro and in vivo antimycobacterial activities of a new quinolone, DU-6859a

A new fluoroquinolone, DU-6859a, was studied for its in vitro and in vivo antimycobacterial activities. MIC determination by the agar dilution method with 7H11 medium revealed that DU-6859a had MICs at which 90% of M. kansasii (0.78 microgram/ml), M. marinum (1.56 micrograms/ml), M. scrofulaceum (1.56 micrograms/ml), M. fortuitum (0.39 microgram/ml), M. chelonae subsp. abscessus (6.25 micrograms/ml), and M. chelonae subsp. chelonae (1.56 micrograms/ml) were inhibited were 4 to 32 times lower than those of ofloxacin and sparfloxacin. The MICs of DU-6859a at which 90% of M. tuberculosis (0.2 microgram/ml) and M. avium-M. intracellulare complex (12.5 micrograms/ml each) were inhibited were comparable to those of sparfloxacin but were four- to eightfold lower than those of ofloxacin. Thus, DU-6859a possessed more potent in vitro activity than sparfloxacin and ofloxacin against most mycobacterial species. DU-6859a exerted significant efficacy against infections caused by M. intracellulare and M. chelonae subsp. abscessus induced in mice when it was given at a dose of 1 mg per mouse (ca. 50 mg/kg of body weight) in terms of reducing the frequency of occurrence and the degree of gross pulmonary or renal lesions and bacterial loads in the lungs, spleens, or kidneys. The efficacy of DU-6859a was greater than that of ofloxacin and was more pronounced against M. chelonae infections than against M. intracellulare infections.

beta-Lactam antibiotic modulation of murine neutrophil cytokinesis

Fourteen cephalosporins, 11 penicillins and 1 monobactam were evaluated for their in vitro modulation of murine neutrophil cytokinesis. As a result, the beta-lactam antibiotics were placed into 6 groups based on their effect on random (R) and FMLP-directed (D) migration [Group 1 (no effect): cephalosporin C; Group 2 (R-->D decreases): cloxacillin, cefotaxime, ceftazadime, cefuroxime, cephalothin, cephapirin, cephadine, nafcillin, piperacillin, ticarcillin, ampicillin, oxacillin, aztreonam; Group 3 (R increases D-->): cephaloridine; Group 4 (R increases D increases): cefsulodin; Group 5 (R increases D decreases): cefoperazone, cefoxitin, ceftriaxone, 6-amino-penicillanic acid; Group 6 (R decreases D decreases): cefadroxil, cefazolin, penicillin G, methicillin]. Trypan blue exclusion studies showed that inhibition of R and D by Group 6 beta-lactam antibiotics is not due to overt cytotoxicity. beta-lactam antibiotics inhibiting D also increased neutrophil adherence to plastic at a concentration of 1000 microM. Finally, the [Ca++] inhibitor chlorpromazine significantly abrogates beta-lactam- and FMLP-directed migration at a test concentration of 1 microM.

Cefodizime host-defence enhancement: considerations of dose-response relationships in healthy volunteers

Studies with cefodizime in animals have shown that this new aminothiazolyl cephalosporin, possessing a broad antibacterial spectrum, positively influences a number of immunological parameters. In most investigations in which different dosage regimens were compared, a bell-shaped dose-response relationship was determined, i.e. activity after higher doses returned to near-baseline levels. This finding is typical of most immunomodulating agents. On this basis, the results obtained in healthy subjects were reviewed. Studies for investigating the biological response modifying (BRM) properties of cefodizime have been conducted in this population with either 2 g once daily i.v. or--in the majority--with 2 x 2 g/day i.v. After seven days of treatment with 1 x 2 g daily, no relevant changes could be demonstrated in healthy subjects, whereas there was an increase in monocyte and granulocyte chemotaxis in a parallel group of patients with multiple myeloma. In contrast, treatment with 2 x 2 g daily induced higher lymphocyte responsiveness and significantly increased nonspecific phagocytosis of both neutrophils and monocytes. The experience in healthy volunteers clearly demonstrates that the latter dose, usually the highest required for antibiotic treatment with cefodizime, is still located on the upward slope of the dose-response curve of positive BRM effects.

Cefodizime: the Japanese clinical experience

In a clinical trial conducted in Japan from 1985-1988, the efficacy of cefodizime was studied in 2,227 adult and 449 pediatric patients. Of these, 1,366 adult and 203 pediatric patients had pathogens isolated and were evaluable. Cefodizime was effective in 78.8% of the adult patients, and adverse reactions occurred in 2.3%. In pediatric patients cefodizime was effective in 91.1% of the cases, and adverse reactions developed in 5.1%. A very high concentration of cefodizime is achieved in blood soon after administration and its penetration into tissues is also high. Moreover, cefodizime exhibits phagocytosis enhancement activity. The above-mentioned excellent efficacy rates, low rates of side effects and enhancement of phagocytic activity make cefodizime an antibiotic of choice in adult and pediatric patients.

Effects of anti-infectious agents on polymorphonuclear neutrophils

Polymorphonuclear neutrophils play a crucial role in host defences against infectious diseases. New trends in anti-infectious therapy require knowledge of the possible interactions between the drugs and the natural defence system. This overview summarizes some of the in vitro data on the effects of anti-infectious agents on neutrophils. The relevance for the clinical situation is discussed.

Effects of imipenem and cefmetazol on lymphocyte receptors CD2, Fc and C3b of complement

We studied the influence of Imipenem and Cefmetazol (50 mg/l) on lymphocyte receptors CD2, Fc and C3b of complement. The lymphocytes were obtained from human blood and mice axillary ganglions. Cefmetazol significantly increases the binding capacity of human lymphocyte receptors CD2 to sheep red blood cells while Imipenem does not alter this binding. The number of Fc lymphocyte receptors for the constant fraction of IgG is found to be significantly increased when the lymphocytes are incubated in vitro with Imipenem and Cefmetazol. When the lymphocytes are treated with these antibiotics there is an increase in the receptors capable of binding to fraction C3b of the complement.

Tolerance and disposition of cefpimizole in normal human volunteers after intramuscular administration

Cefpimizole sodium (AC-1370, U-63196E) was administered intramuscularly in doses from 100 mg (0.5 ml) to 2,000 mg (two 3.5-ml doses) to healthy human volunteers in three double-blind placebo and positive-controlled (cefotaxime, cephalothin) single-dose studies and in two multiple-dose studies. Mild transient pain was observed at the injection site, but no erythema, petechia, necrosis, or atrophy was noted. Creatinine phosphokinase values were increased during the study in the cefpimizole- and placebo-treated groups but began to return to normal toward the end of the study period (day 5). They were not paralleled by a similar magnitude of elevation in serum glutamic oxalacetic transaminase and lactate dehydrogenase or by pain and tenderness. There were no clinically meaningful or statistically significant changes (P greater than 0.5) or trends in vital signs and no other patterns of drug-related clinical abnormalities noted in any of the laboratory measurements evaluated (hematology, chemistry, urinalysis). No serious side effects occurred during or after the study. Cefpimizole was well tolerated locally and systemically by all the subjects at all administered dosage levels. Cefpimizole concentrations in serum (microbiological assay) remained above 1 microgram/ml at 12 h after drug administration for all dose levels. The median peak concentrations in plasma for the 500- and 1,000-mg twice-daily dosages of cefpimizole were, respectively, 21.6 and 45.5 micrograms/ml on day 1, 16.2 and 43.7 micrograms/ml on day 3, and 20.1 and 41.4 micrograms/ml on day 6 of the study. The apparent terminal disposition half-life throughout the study was about 2.0 h. The median amounts of cefpimizole excreted in the urine for the first 12 h of each day evaluated were 370 and 1,071 mg on day 1, 416 and 972 mg on day 3, and 370 and 975 mg on day 6 for the 500- and 1,000-mg twice-daily dosages, respectively. Dose proportionally of cefpimizole was obtained for the 500- and 1,000-mg and the 2,000-mg groups. The absorption, distribution, and elimination of cefpimizole after multiple-dose intramuscular administration were uniform, were linear in relation to dose, and did not result in drug accumulation.

Interaction of beta-lactam antibiotics with the bactericidal activity of leukocytes against Escherichia coli

The effect of beta-lactam antibiotics on phagocytosis and intracellular killing of four isogenic Escherichia coli strains differing in their 0- and K antigens was studied by adopting the rat polyvinyl-sponge model. The penicillins mezlocillin, ticarcillin and piperacillin rendered all four isogenic E. coli strains more susceptible to intraleukocyte killing; the cefalosporins tested exhibited inhomogenous effects; lamoxactam was marginally effective, whereas cefoxitin was completely ineffective; cefotaxime caused an increase in intracellular killing of the capsule-defective mutant only. The beta-lactam promoted increase in intracellular killing could be inhibited by alpha-methylmannoside but not by alpha-methylglucoside. Free-flow electrophoretic separation of mezlocillin-treated bacteria and guinea pig erythrocytes revealed that co-migration of E. coli and erythrocytes respectively could be inhibited by alpha-methylmannoside but not by alpha-methylglucoside. These data indicate that mezlocillin interferes with the mannose sensitive adhesins of E. coli.

Pharmacokinetics and dose proportionality of cefpimizole in normal humans after intramuscular administration

The pharmacokinetics of cefpimizole (free acid equivalents of cefpimizole sodium), a broad-spectrum cephalosporin antibiotic, were evaluated after intramuscular administration of single doses (dose range, 100 to 1,000 mg) and multiple doses (dose range, 500 to 2,000 mg) given b.i.d. for 6 or 11 days. The kinetics after intramuscular administration correspond to a one-compartment model with first-order input. The apparent volume of distribution of the absorbed dose averaged 18.6 +/- 3.4 (standard deviation) liters for 58 individuals; the absorption-phase and elimination-phase rate constants averaged 2.53 +/- 1.16 h-1 (half-life, 0.27 h) and 0.338 +/- 0.041 h-1 (half-life, 2.05 h), respectively; and the mean residence time was 3.43 +/- 0.43 h. The total body clearance of the absorbed dose after single-dose intramuscular administration was 102 +/- 13 ml/min. The primary route of elimination was renal with 73 to 83% of the administered dose excreted in the urine as unchanged drug. Renal clearance averaged 81 +/- 13 ml/min. Dose proportionality was obtained from area under the plasma curve, concentration maximum in plasma, and cumulative urinary excretion levels. Multiple-dose evaluation of intramuscular administration of cefpimizole indicated no apparent change in the absorption or elimination phases after b.i.d. dosing for 6 or 11 days. The kinetic parameters determined from multiple-dose plasma and urine levels were in close agreement with the same parameters calculated from single-dose results. No apparent accumulation of cefpimizole occurred, and nondetectable levels of drug were observed in the 24-h plasma and 24- to 48-h urine specimen after administration of the last dose. The kinetics of cefpimizole after intramuscular administration were similar to the kinetics obtained after intravenous infusion.

Effect of ciprofloxacin on phagocytosis

Certain aspects of the relationship between host defence mechanisms and the new quinoline derivative ciprofloxacin in comparison to norfloxacin and ofloxacin were studied. Ciprofloxacin did not affect chemotaxis of human polymorphonuclear leucocytes in agarose. In leucocytes exposed to ciprofloxacin, norfloxacin and ofloxacin neither the chemiluminescent response to opsonized zymosan and formyl-methionyl-leucyl-phenylalanine nor the phagocytic or bactericidal activity was affected. However, killing of Staphylococcus aureus by human polymorphonuclear leucocytes exposed to subinhibitory concentrations of ciprofloxacin was enhanced. The results show that the quinolines tested do not directly influence phagocytic cells, but a subinhibitory concentration can make bacteria more susceptible to phagocytosis and killing.

In vitro comparative antimicrobial activity of cefpimizole against clinical isolates from five medical centers

Cefpimizole was compared with cefoperazone and cefotaxime against 6,599 clinical bacterial isolates from five medical centers. Cefoperazone and cefotaxime were both more active and provided a greater spectrum of antimicrobial coverage than cefpimizole. Some of the cefpimizole minimum concentrations inhibiting 50% of tested strains were as follows: Citrobacter freundii and Enterobacter cloacae, 16 micrograms/ml; Escherichia coli and Klebsiella pneumoniae, 2.0 micrograms/ml; Proteus mirabilis, 1.0 microgram/ml; Pseudomonas aeruginosa, 16 micrograms/ml; Staphylococcus spp., 32 micrograms/ml; and the enterococci, greater than 32 micrograms/ml.

In vitro antimicrobial susceptibility testing using 30 microG and 75 microG U63196-E (cefpimizole AC-1370) disks

U63196-E, a new cephalosporin, was evaluated for its antimicrobial spectrum and its application to standardized in vitro susceptibility test methods. The proposed criteria for the 75-micrograms U63196-E disk are greater than or equal to 18 mm (less than or equal to 16 micrograms/ml) = susceptible and less than or equal to 14 mm (greater than 32 micrograms/ml) = resistant. These limits are preferred to the 30 micrograms disk and produce only 4.2% major and very major interpretive errors. Previously published interpretive criteria for the 75 micrograms cefoperazone disk were confirmed.

Pharmacokinetics of cefpimizole in normal humans after single- and multiple-dose intravenous infusions

The pharmacokinetics of cefpimizole (free acid equivalents of cefpimizole sodium), a broad-spectrum cephalosporin antibiotic, were determined after single- and multiple-dose 20-min intravenous infusions of 1, 2, and 4 g. The kinetics of single-dose administration of cefpimizole correspond to a two-compartment model with an average apparent volume of distribution of 20.0 +/- 3.5 liters, a distribution rate constant of 2.24 +/- 1.00 h-1, and a terminal rate constant of 0.358 +/- 0.036 h-1 (half-life, 1.9 h). The total body clearance was 118.6 +/- 20.2 ml/min. The primary route of elimination for cefpimizole was the renal route, with approximately 80% of the administered dose excreted as the parent compound. The elimination rate constant, as calculated from urinary excretion data, was 0.339 +/- 0.043 h-1, which is in close agreement with the terminal rate constant for plasma. Renal clearance of cefpimizole was 96.2 +/- 17.3 ml/min. Dose proportionality over the three dose levels was obtained from area under the plasma curve and cumulative urinary excretion data. The results of the multiple-dose study indicated that no apparent change in the distribution or elimination kinetics of cefpimizole occurred after the administration of 1-, 2-, and 4-g doses for 7 days, three times a day. The kinetics from the multiple-dose study were in close agreement with those from the single-dose study. No accumulation of cefpimizole occurred, and nondetectable levels was observed 24 h after administration of the last dose. Peaks that could be attributed to metabolites of cefpimizole were not observed during high-pressure liquid chromatographic analysis of either plasma or urine specimens.

Changing patterns of resistance to new beta-lactam antibiotics. In vitro efficacy of cefoperazone against bacterial pathogens

No evidence for significant increase in resistance to cefoperazone was detected in susceptibility test surveillance programs or in the literature through 1983, but rare endemic resistance to cefoperazone and some other newer beta-lactams was found. Medical centers contemplating the use of a third-generation drug for cost-containment should be aware of the susceptibility of isolates in their hospitals, and the drug's ability to withstand beta-lactamase hydrolysis by local pathogens. The possible dangers of inducible cephalosporins in certain Enterobacteriaceae and strains of Pseudomonas aeruginosa are discussed in the light of the physical and chemical characteristics of the newer antimicrobial agents. Criteria for judging the values of investigational beta-lactams are presented. These focus on the interaction of antimicrobial agents with host defense mechanisms and circulating blood elements.

In vitro evaluation of U63196-E (AC-1370): antimicrobial activity, beta-lactamase stability, and beta-lactamase inhibition

Upjohn compound U63196 -E (formerly AC-1370) is a new semisynthetic cephalosporin with a broad spectrum of antimicrobial activity that includes Pseudomonas aeruginosa (minimum inhibitory concentration, 8.0 micrograms/ml), nearly all members of the Enterobacteriaceae, and most gram-positive cocci except enterococci and staphylococci resistant to to methicillin. The compound was stable to most commonly isolated beta-lactamases, especially TEM-1, TEM-2, and P-99; the highest rates of hydrolysis of U63196 -E were by PSE enzymes (23.4-92.5% of the relative hydrolysis rate of cephaloridine). Compared to eight other beta-lactams, U63196 -E was a poor inhibitor of beta-lactamases.

Stimulation of granulocyte functions in vitro by imipenem and the renal enzyme inhibitor MK 0791

Imipenem and the renal enzyme inhibitor MK 0791 (dehydropeptidase-I) were tested separately and in a 1:1 combination to delineate their effects on granulocyte functioning. Each component, as well as the combination product, was found to increase granulocyte adherence and chemotaxis at therapeutic concentrations. Phagocytosis and chemiluminescence were not found to be significantly altered by any of the drug combinations.

Mechanism of action of AC-1370 on phagocyte functions

The mechanism of action of a new semisynthetic cephalosporin AC-1370 on phagocyte functions was investigated. AC-1370 enhanced phagocytic functions of macrophages and neutrophils. AC-1370 bound to 27.4% of mouse peritoneal resident cells. Most of the AC-1370-binding cells were macrophages, and few neutrophils bound AC-1370. Culture supernatant of mouse macrophages cultured with AC-1370 significantly augmented phagocytic functions of mouse neutrophils. This activity of the culture supernatant of AC-1370-stimulated macrophages was abolished by digestion with trypsin but not by heat treatment at 56 degrees C for 30 min. The mechanism of the activation of phagocyte functions by AC-1370 is proposed as follows. First, AC-1370 binds to macrophages and causes their activation. Second, trypsin-sensitive and heat-stable soluble factor(s) is released from these macrophages. And finally, neutrophil functions are activated by the factor(s).