In vitro antimicrobial activity of T-91825, a novel anti-MRSA cephalosporin, and in vivo anti-MRSA activity of its prodrug, TAK-599

TAK-599 is a water-soluble prodrug of a cephalosporin compound, T-91825. In vitro and in vivo antibacterial activities of T-91825 and TAK-599, respectively, were examined. T-91825 was active against both gram-positive and gram-negative bacteria, unlike vancomycin and linezolid, which are inactive against gram-negative bacteria. The 90% minimum inhibitory concentration of T-91825 against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) was 2 micro g/ml. This activity was comparable to those of vancomycin, linezolid, teicoplanin, and arbekacin. T-91825 was similarly active against vancomycin-intermediate S. aureus. In a time-kill study, T-91825 showed more rapid and distinct decrease of viable cells of two MRSA strains than did vancomycin and linezolid in vitro. The effect of TAK-599 against systemic infection caused by clinical isolates of MRSA in mice was comparable or superior to that of vancomycin, linezolid, teicoplanin, and arbekacin. In addition, TAK-599 at a dose of 20 mg/kg significantly decreased bacterial counts in lungs of mice in an experimental pneumonia model caused by MRSA in which vancomycin and linezolid were totally ineffective at the same dose. These results suggest the usefulness of TAK-599 in the treatment of MRSA infections in humans.

TAK-599, a novel N-phosphono type prodrug of anti-MRSA cephalosporin T-91825: synthesis, physicochemical and pharmacological properties

Crystalline 1 (TAK-599) is a novel N-phosphono prodrug of anti-methicillin-resistant Staphylococcus aureus (MRSA) cephalosporin 2a (T-91825) that has high affinity for penicillin-binding protein (PBP) 2' (IC(50); 0.90 microg/mL) and shows potent in vitro anti-MRSA activity (MIC against MRSA N133; 1.56 microg/mL), comparable to that of vancomycin (1.56 microg/mL). Although 2a had insufficient water solubility (2.3 mg/mL) for parenteral administration, 1 showed excellent water solubility (>100 mg/mL, pH 7) as well as good chemical stability in the solid state and solution. In pharmacokinetic studies, when 1 was administered intravenously to rats and monkeys, it was rapidly converted into 2a in the blood. These results show that 1 (TAK-599) is a highly promising parenteral cephalosporin targeted for MRSA infection.

Autonomic nervous activity and stress hormones induced by hyperbaric saturation diving

This study describes the changes in autonomic nervous activity and stress hormones during a hyperbaric saturation dive up to 4.1 MPa in six subjects. Their autonomic nervous activity was assessed by a power spectrum analysis of heart rate variability (HRV). The levels of plasma epinephrine (E) and norepinephrine (NE), and those of salivary chromogranin A and cortisol, were compared with the pre-dive control levels. Restrained activity of the cardiac vagal nerve was recognized in the early post-dive period by a decrease in high frequency power and by the standard deviation of the HRV. By contrast, enhanced activity of sympathetic nerve was recognized in the early post-dive period by an elevated plasma E, and also in the late 3.1 MPa, 4.1 MPa, and post-dive periods by elevated plasma NE. The levels of plasma E and NE were the most sensitive indicators of sympathetic nervous activity. A joint utilization of HRV parameters with stress hormones may be an effective means of estimating the adaptive responses between hyperbaric and normobaric environments.

In vitro and in vivo antifungal activities of TAK-456, a novel oral triazole with a broad antifungal spectrum

TAK-456 is a novel oral triazole compound with potent and broad-spectrum in vitro antifungal activity and strong in vivo efficacy against Candida albicans and Aspergillus fumigatus. TAK-456 inhibited sterol synthesis of C. albicans and A. fumigatus by 50% at 3 to 11 ng/ml. TAK-456 showed strong in vitro activity against clinical isolates of Candida spp., Aspergillus spp., and Cryptococcus neoformans, except for Candida glabrata. The MICs at which 90% of the isolates tested were inhibited byTAK-456, fluconazole, itraconazole, voriconazole, and amphotericin B were 0.25, 4, 0.5, 0.13, and 0.5 microg/ml, respectively, for clinical isolates of C. albicans and 1, >64, 0.5, 0.5, and 0.5 microg/ml, respectively, for clinical isolates of A. fumigatus. Therapeutic activities of TAK-456 and reference triazoles against systemic lethal infections caused by C. albicans and A. fumigatus in mice were investigated by orally administering drugs once daily for 5 days, and efficacies of the compounds were evaluated by the prolongation of survival. In normal mice, TAK-456 and fluconazole were effective against infection caused by fluconazole-susceptible C. albicans at a dose of 1 mg/kg. In transiently neutropenic mice, therapeutic activity of TAK-456 at 1 mg/kg of body weight against infection with the same strain was stronger than those at 1 mg/kg of fluconazole. TAK-456 was effective against infections with two strains of fluconazole-resistant C. albicans at a dose of 10 mg/kg. TAK-456 also expressed activities similar to or higher than those of itraconazole against the infections caused by two strains of A. fumigatus in neutropenic mice at a dose of 10 mg/kg. These results suggest that TAK-456 is a promising candidate for development for the treatment of candidiasis and aspergillosis in humans.

Efficacy of TAK-457, a novel intravenous triazole, against invasive pulmonary Aspergillosis in neutropenic mice

TAK-457 is an injectable prodrug of TAK-456, which is a novel oral triazole compound with potent antifungal activity. The in vivo efficacy of TAK-457 was evaluated in two models of invasive pulmonary aspergillosis with CDF(1) mice and CBA/J mice with transient neutropenia induced by cyclophosphamide. Against the infection in CDF(1) mice, treatment with 10 mg of TAK-457 and 1 mg of amphotericin B/kg reduced the fungal burden in lungs and rescued all mice. In the infection model with CBA/J mice, TAK-457 at a dose of 10 mg/kg significantly prolonged the survival time of mice, showing significant reduction of lung chitin levels and the plasma beta-D-glucan levels. On the other hand, amphotericin B at 1 mg/kg which was a maximum tolerable dose showed slight but not significant prolongation of survival time of mice, although it also reduced the lung chitin levels and the plasma beta-D-glucan levels to a lower extent but still significantly. These results suggest that TAK-457 is a promising candidate for development for the treatment of invasive aspergillosis in humans.

Inhibitory effects of small-molecule CCR5 antagonists on human immunodeficiency virus type 1 envelope-mediated membrane fusion and viral replication

We established a human immunodeficiency virus type 1 (HIV-1) envelope (Env)-mediated membrane fusion assay and examined the small-molecule CCR5 antagonist TAK-779 and its derivatives for their inhibitory effects on HIV-1 Env-mediated membrane fusion and viral replication. The membrane fusion assay is based on HIV-1 long terminal repeat-directed beta-D-galactosidase reporter gene expression in CD4- and CCR5-expressed HeLa (MAGI-CCR5) cells after cocultivation with effector 293T cells expressing HIV-1 Env. Inhibition of HIV-1 replication was also determined in MAGI-CCR5 cells infected with the corresponding cell-free HIV-1. TAK-779 effectively suppressed R5 HIV-1 (strain JR-FL) Env-mediated membrane fusion as well as viral replication. Its 50% inhibitory concentrations (IC(50)s) for membrane fusion and viral replication were 0.87 +/- 0.11 and 1.4 +/- 0.1 nM, respectively. These values corresponded well to the IC(50) for (125)I-RANTES (regulated on activation, T cell expressed, and secreted) binding to CCR5 (1.4 nM). The inhibitory effects of 18 TAK-779 derivatives on membrane fusion differed from one compound to another. However, there was a close correlation among their inhibitory effects on membrane fusion, viral replication, and RANTES binding. The correlation coefficient between their IC(50)s for membrane fusion and viral replication was 0.881. Furthermore, since this assay depends on Env expressed in the effector cells, it is also applicable to the evaluation of CXCR4 antagonists. These results indicate that the HIV-1 Env-mediated membrane fusion assay is a useful tool for the evaluation of entry inhibitors.

Optically active antifungal azoles. XII. Synthesis and antifungal activity of the water-soluble prodrugs of 1-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]-3-[4-(1H-1-tetrazolyl)phenyl]-2-imidazolidinone

1-[(1R,2R)-2-(2,4-Difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]-3-[4-(1H-1-tetrazolyl)phenyl]-2-imidazolidinone (1: TAK-456) was selected as a candidate for clinical trials, but since its water-solubility was insufficient for an injectable formulation, the quaternary triazolium salts 2 were designed as water-soluble prodrugs. Among the prodrugs prepared, 4-acetoxymethyl-1-[(2R,3R)-2-(2,4-difluorophenyl)-2-hydroxy-3-[2-oxo-3-[4-(1H-1-terazolyl)phenyl]-1-imidazolidinyl]butyl]-1H-1,2,4-triazolium chloride (2a: TAK-457) was selected as an injectable candidate for clinical trials based on the results of evaluations on solubility, stability, hemolytic effect and in vivo antifungal activities.

Studies on anti-MRSA parenteral cephalosporins. IV. A novel water-soluble N-phosphono type prodrug for parental administration

A systematic approach for improving the water-solubility of anti-MRSA (methicillin-resistant Staphylococcus aureus) cephalosporin derivatives is described. We first tried to improve the water-solubility of 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-fluoromethoxyiminoacetamido]-3-[(E)-2-(1-methylimidazo[1,2-b]pyridazinium-6-yl)thiovinyl]-3-cephem-4-carboxylate (1a) by substitution of the C-3' pharmacophore. Replacement of the C-3' pharmacophore with a 1-methyl-4-pyridinio group improved the water-solubility without decreasing the anti-MRSA activity. Furthermore, we applied the N-modified prodrug strategy to the C-7 acyl group in order to enhance the water-solubility drastically. Among the compounds prepared, the N-phosphono type prodrugs 2a(1-methylimidazo[1,2-b]pyridazinium derivative) and 2b (1-methyl-4-pyridinio derivative) showed water-solubility appropriate for a product intended for intravenous injection and in vivo anti-MRSA activity comparable to that of vancomycin.

Studies on Anti-MRSA Parenteral Cephalosporins. III. Synthesis and Antibacterial Activity of 7.BETA.-[2-(5-Amino-1,2,4-thiadiazol-3-yl)-2(Z)-alkoxyiminoacetamido]-3-[(E)-2-(1-alkylimidazo[1,2-b]pyridazinium-6-yl)thiovinyl]-3-cephem-4-carboxylates and Related Compounds

In the course of our exploration for a novel cephalosporin derivative having excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), we modified the C-3 linked spacers of cephem derivatives bearing a 1-methylimidazo[1,2-b]pyridazinium-6-yl group at the C-3' position and 2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-cyclopentyloxy-iminoacetyl group at the C-7 position. The optimal spacers were the (E)-2-vinyl and (E)-2-thiovinyl groups seen in 19a and 29aa, respectively. Their anti-MRSA activity was 16 to 32 times as potent as that of cefozopran (CZOP). Focusing on the (E)-2-vinyl and (E)-2-thiovinyl spacers, we further modified the alkoxyimino groups in the C-7 acyl moiety and the 1-alkylimidazo[1,2-b]pyridazinium moieties at the C-3' position and investigated the structure-activity relationships (SAR) of the derivatives. Consequently, we selected 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-fluoromethoxyiminoacetamido]-3-[(E)-2-(1-methylimidazo[1,2-b]pyridazinium-6-yl)thiovinyl]-3-cephem-4-carboxylate (29ca) as a new anti-MRSA parenteral cephalosporin candidate for further biological evaluation. The selected 29ca showed anti-MRSA activity comparable to that of vancomycin (VCM) both in vitro and in vivo, high affinity (IC50)=2.7 microg/ml) for penicillin binding protein 2' (PBP2') of MRSA and potent activity against Gram-negative bacteria as well.

Optically active antifungal azoles. X. Synthesis and antifungal activity of N

New optically active antifungal azoles, N-14-(azolyl)phenyl]- and N-14-(azolylmethyl)phenyl]-N'-[(IR,2R)-2(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(IH-1,2,4-triazol-1-yl)propyllazolones (1, 2, 3), were prepared in a stereocontrolled manner. Compounds 1-3 showed strong antifungal activity against Candida albicans in vitro. Among them, the imidazolidinones 3 showed a broad antifungal spectrum in vitro as well as potent in vivo activity against candidiasis and aspergillosis in mice. The imidazolidinones (3i, j, k) having 1H-1,2,3-triazol-1-yl, 2H-2-tetrazolyl and IH-1-tetrazolyl moieties were found to exert strong protective effect against aspergillosis.

Studies on anti-MRSA parenteral cephalosporins. I. Synthesis and antibacterial activity of 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)- hydroxyiminoacetamido]-3-(substituted imidaz

In order to improve the antibacterial activity of cefozopran (CZOP) against methicillin-resistant Staphylococcus aureus (MRSA), we initiated chemical modification to introduce a 2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-hydroxyimino acetyl group at the C-7 position and a 3- or 6-substituted imidazo[1,2-b]pyridazinium or 5-substituted imidazo[1,2-a]pyridinium group at the C-3' position. Although this approach successfully enhanced the anti-MRSA activity of CZOP two to eight times, a slight decrease in the activity against Gram-negative bacteria including Pseudomonas aeruginosa was involved. Among the novel derivatives, 3-(6-aminoimidazo[1,2-b]pyridazinium-1-yl)methyl-7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)hydroxyiminoacetamido]-3-cephem-4-carboxylate (44a) showed an excellent balance of activity against MRSA and Gram-negative bacteria.

Studies on anti-MRSA parenteral cephalosporins. II. Synthesis and antibacterial activity of 7beta-[2-(5-amino-1,2,4- thiadiazol-3-yl)-2(Z)-alkoxyiminoacetamido]-3-(substituted imidaz

In an effort to discover a novel cefozopran (CZOP) derivative having excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), we performed chemical modification of the alkoxyimino moiety and imidazo[1,2-b]pyridazinium group of CZOP. Among the prepared compounds, the cyclopentyloxyimino derivative 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-cyclopentyloxyiminoacetamido]-3-(3,6-diaminoimidazo[1,2-b]pyridazinium-1-yl)methyl-3-cephem-4-carboxylate (20 g) showed the most potent anti-MRSA activity, reflecting its high affinity (IC50 = 1.6 microg/ml) for penicillin binding protein 2' (PBP2'), although its anti-MRSA activity was slightly inferior to that of vancomycin (VCM). In experimental systemic infection in mice, however, 20 g showed activity comparable to that of VCM against MRSA. In addition, 20 g showed activity similar or slightly inferior to that of CZOP against Pseudomonas aeruginosa both in vitro and in vivo. Considering its favorable antibacterial activity profile, 20 g was considered to be the most promising CZOP derivative for further studies.

Establishment of a CCR5-expressing T-lymphoblastoid cell line highly susceptible to R5 HIV type 1

The beta-chemokine receptor CCR5 is considered to be an attractive target for inhibition of CCR5-using (R5 or macrophage-tropic) HIV-1. However, R5 HIV-1 cannot replicate in CD4+ T cell or monocyte lines because of the lack of CCR5 expression on their surface, which apparently hampers discovery and development of effective CCR5 antagonists against HIV-1 replication. In this study, we have established the CCR5-expressing T cell line MOLT-4/CCR5, highly permissive to the replication of R5 HIV-1. The cells express a considerable amount of CCR5 on their surface. When the cells were infected with the R5 HIV-1 strains Ba-L and JR-FL, the virus-induced cytopathic effect (syncytium formation) was observed, and the cells produced large amounts of HIV-1 p24 antigen in the culture supernatants. The analyses of progeny viruses for their coreceptor use and gp120 V3 nucleotide sequence revealed that they were R5 HIV-1. The parental cell line MOLT-4 was much less susceptible to Ba-L and totally insusceptible to JR-FL. Furthermore, MOLT-4/CCR5 cells could support the replication of an R5 clinical isolate, but MOLT-4 cells could not. When TAK-779, a novel small-molecule nonpeptide CCR5 antagonist, was examined for its inhibitory effect on R5 HIV-1 replication in MOLT-4/CCR5 cells, the compound displayed potent antiviral activity, as demonstrated in peripheral blood mononuclear cells. These results indicate that the established cell line will be an extremely useful tool for experiments with R5 HIV-1.

A small-molecule, nonpeptide CCR5 antagonist with highly potent and selective anti-HIV-1 activity

The beta-chemokine receptor CCR5 is considered to be an attractive target for inhibition of macrophage-tropic (CCR5-using or R5) HIV-1 replication because individuals having a nonfunctional receptor (a homozygous 32-bp deletion in the CCR5 coding region) are apparently normal but resistant to infection with R5 HIV-1. In this study, we found that TAK-779, a nonpeptide compound with a small molecular weight (Mr 531.13), antagonized the binding of RANTES (regulated on activation, normal T cell expressed and secreted) to CCR5-expressing Chinese hamster ovary cells and blocked CCR5-mediated Ca2+ signaling at nanomolar concentrations. The inhibition of beta-chemokine receptors by TAK-779 appeared to be specific to CCR5 because the compound antagonized CCR2b to a lesser extent but did not affect CCR1, CCR3, or CCR4. Consequently, TAK-779 displayed highly potent and selective inhibition of R5 HIV-1 replication without showing any cytotoxicity to the host cells. The compound inhibited the replication of R5 HIV-1 clinical isolates as well as a laboratory strain at a concentration of 1.6-3.7 nM in peripheral blood mononuclear cells, though it was totally inactive against T-cell line-tropic (CXCR4-using or X4) HIV-1.

Formation of azole-resistant Candida albicans by mutation of sterol 14-demethylase P450

The sterol 14-demethylase P450 (CYP51) of a fluconazole-resistant isolate of Candida albicans, DUMC136, showed reduced susceptibility to this azole but with little change in its catalytic activity. Twelve nucleotide substitutions, resulting in four amino acid changes, were identified in the DUMC136 CYP51 gene in comparison with a reported CYP51 sequence from a wild-type, fluconazole-susceptible C. albicans strain. Seven of these substitutions, including all of those causing amino acid changes, were located within a region covering one of the putative substrate recognition sites of the enzyme (SRS-1). Polymorphisms within this region were observed in several C. albicans isolates, and some were found to be CYP51 heterozygotes. Among the amino acid changes occurring in this region, only an alteration of Y132 was common among these fluconazole-resistant isolates, which suggests the importance of this residue to the fluconazole resistance of the target enzyme. DUMC136 and another fluconazole-resistant isolate were homozygotes with respect to CYP51, although the typical wild-type, fluconazole-susceptible C. albicans was a CYP51 heterozygote. These findings suggest that part of the fluconazole-resistant phenotype of C. albicans DUMC136 was acquired through a mutation-prone area of CYP51, an area which might promote the formation of fluconazole-resistant CYP51, along with a mechanism(s) which allows the formation of a homozygote of this altered CYP51 in this diploid pathogenic yeast.

Optically active antifungal azoles. VIII. Synthesis and antifungal activity of 1-[(1R,2R)-2-(2,4-difluoro- and 2-fluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]- 3-(4-substituted phenyl)-2(1H,3H)-imidazolones and 2-imidazolidinones

New optically active antifungal azoles, 1-[(1R,2R)-2-(2,4-difluoro- and 2-fluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl ]-3-(4- substituted phenyl)-2(1H,3H)-imidazolones (1,2) and 2-imidazolidinones (3,4), were prepared in a stereocontrolled manner from (1S)-1-[(2R)-2-(2,4- difluoro- and 2-fluorophenyl)-2-oxiranyl]ethanols (15, 16). Compounds 1-4 showed potent antifungal activity against Candida albicans in vitro and in vivo, as well as a broad antifungal spectrum for various fungi in vitro. Furthermore, the imidazolidinones, 3b--e and 4d, e, were found to exert extremely strong growth-inhibitory activity against Aspergillus fumigatus.

In vitro and in vivo efficacy of the triazole TAK-187 against Cryptococcus neoformans

Multiple isolates of Cryptococcus neoformans, including those with fluconazole resistance, were tested to assess the in vitro activity of the new triazole TAK-187. MICs of TAK-187 were at least eightfold lower than those of fluconazole, and fungicidal concentrations for most isolates were 4 microg/ml or less. TAK-187 also was evaluated as intermittent therapy using two dosages in a rabbit model of experimental cryptococcal meningitis. Compared to daily treatment with fluconazole, as little as two doses of TAK-187 given 7 days apart were found to be effective. Plasma and cerebrospinal fluid TAK-187 concentrations were many times higher than MICs and fungicidal concentrations. Based upon its therapeutic efficacy and long half-life in the rabbit model, TAK-187 should be investigated for intermittent dosing in treatment or suppression of cryptococcal infections in humans.

[In vitro specific binding of Shiga toxin 1 and 2 by TAK-751S (Gb3 analog)]

TAK-751S is a synthetic trisaccharide coupled to Chromosorb P using a spacer sequence of 8-methoxycarboyloctyl (MCO). Its chemical structure is similar to a human receptor (Gb3) of Stx produced by enterohemorrhagic Escherichia coli (EHEC). In vitro efficacy of TAK-715S was studied by using ACHN cultured cell assay, which is sensitive and specific for measuring low level of Stx. Under various conditions, TAK-715S was mixed with purified Stx1 and Stx2, and residual free toxins in the solution were measured by using ACHN cells. TAK-715S was demonstrated to bind specifically to Stx1 and Stx2 under the condition similar to a human intestine while Chromsorb P did not bind to any Stx. The binding activity was stable in the presence of various processed foods, fresh vegetables and fruits. Antibiotics such as fosfomycin, kanamycin and norfloxacin did not disturb its binding capability. Minimum inhibitory concentrations of these antibiotics against Staphylococcus aureus FDA209P or E. coli NIHJ JC-2 neither changed after incubating with TAK-751S for 60 min at 37 degrees C. These results suggest that TAK-751S can be given orally with various foods and antibiotics for the elimination of Stx1 and Stx2 in the gut of patients with EHEC infections.

Therapeutic efficacy of cefozopran in a murine model of haematogenous pneumococcal meningitis

Antimicrobial regimens for the treatment of pneumococcal meningitis are not established. We have produced a murine model of haematogenous pneumococcal meningitis and have examined its usefulness for determining the required dosage and term of antimicrobial agents. Streptococcus pneumoniae serotype 6 was injected intraperitoneally (inoculum: about 1 x 10(4) CFU) into mice. Although half of the mice died within 2 days, the surviving mice showed positive bacterial cultures, increase of the protein level, decrease of the glucose level and infiltration of polymorphonuclear leucocytes into cerebrospinal fluids (CSF). When cefozopran was administered subcutaneously twice a day for 1-3 days starting 2 days after infection, dose- and duration-dependent effects were observed and all mice treated with 20 mg/kg of cefozopran for 3 days survived. The penetration rate of cefozopran from blood to CSF in infected mice was 44.7%, which was 6 times higher than that obtained in uninfected mice. This model may be useful for investigating the pathogenesis of haematogenous pneumococcal meningitis and its therapy.

Modified agar dilution susceptibility testing method for determining in vitro activities of antifungal agents, including azole compounds

In vitro activities of antifungal agents, including azole compounds, against yeasts were easily determined by using RPMI-1640 agar medium and by incubating the plates in the presence of 20% CO2. The end point of inhibition was clear by this method, even in the case of azole compounds, because of the almost complete inhibition of yeast growth at high concentrations which permitted weak growth of some Candida strains by traditional methods. MICs obtained by the agar dilution method were similar to those obtained by the broth dilution method proposed by the National Committee for Clinical Laboratory Standards.

[Possibility of drug design of beta-lactam antibiotics effective for multiresistant gram-positive pathogens]

Since infectious diseases are caused by various bacteria and most of them are treated empirically, broad-spectrum antibiotics are required. To expand the spectrum, an imidazopyridazinium group and aminothiadiazole group were introduced to 3- and 7-side chain of cephem nucleus, respectively. The resulting compound, cefozopran, was able to permeate not only outer membrane of Pseudomonas aeruginosa but also envelope of gram-positive bacteria, which functioned as a barrier to antipseudomonal cephalosporins, and showed potent activity against wide variety of bacteria including those which produced a large amount of cephalosporinase and were resistant to third-generation cephalosporins. In spite of the broad antibacterial spectrum, cefozopran only weakly affected gastrointestinal flora of mice and prevented colonization by MRSA.

Therapeutic effects of cefozopran against experimental mixed urinary tract infection with Enterococcus faecalis and Pseudomonas aeruginosa in mice

The therapeutic activity of cefozopran, a new semisynthetic parenteral cephalosporin, was compared with those of ceftazidime, ampicillin, imipenem/cilastatin and ofloxacin against an ascending mixed urinary tract infection induced in mice with Enterococcus faecalis TN2005 and Pseudomonas aeruginosa P9. Cefozopran significantly reduced viable cell counts of both organisms in the kidneys. Ceftazidime, imipenem/cilastatin and ofloxacin were active against only P. aeruginosa, and ampicillin was active against only E. faecalis.

Optically active antifungal azoles. VII. Synthesis and antifungal activity of stereoisomers of 2-[(1R,2R)-2-(2, 4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl) propyl]-4-[4-(2,2,3,3-tetrafluoropropoxy)phenyl]-3(2H,4H)-1,2,4-triazo lone (TAK-187)

2-[(1R,2R)-2-(2,4-Difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2, 4-triazol-1-yl)propyl]-4-[4-(2,2,3,3,tetrafluoropropoxy) phenyl]-3(2H, 4H)-1,2,4-triazolone [(1R,2R)-1: TAK-187] is a new antifungal agent selected as a candidate for clinical trials. The three stereoisomers [(1S,2S)-, (1R,2S)- and (1S,2R)-1] of this compound were prepared to clarify the relationship between the stereochemistry and the biological activities. In vitro and in vivo assays of antifungal activity revealed that TAK-187 [(1R,2R)-1] is the most potent among the four stereoisomers. Furthermore, TAK-187 was found to exert strong and selective inhibitory effect on the sterol synthesis in Candida albicans as compared with that in rat liver.

Gastrointestinal colonization by methicillin-resistant Staphylococcus aureus in immunosuppressed mice

ICR mice were inoculated intranasally with methicillin-resistant Staphylococcus aureus (MRSA) N133, and the inoculated MRSA was quantitatively recovered from the ceca and feces. The viable counts of the MRSA recovered from ceca correlated well with those from feces. Some mice eliminated MRSA from the cecum by 14 days after inoculation. Intraperitoneal administration of cyclophosphamide at a dose of 200 mg/kg 3 days before inoculation inhibited the elimination of the MRSA from both ceca and feces. All mice treated with cyclophosphamide excreted more than 10(4) CFU of the MRSA per g of feces for at least 70 days, indicating persistent colonization of the MRSA in the gastrointestinal tract. Some beta-lactam antibiotics decreased the colonization level, but others did not. The colonization level was suggested to depend on the antibacterial activity of the antibiotic against the MRSA and the degree of disturbance of intestinal flora by the antibiotic.

Avoidant personality disorder and taijin kyoufu: sociocultural implications of the WHO/ADAMHA International Study of Personality Disorders in Japan

This paper discusses the characteristics of avoidant personality disorder in a cultural context based on the Japanese concept of taijin kyoufu as well as that of DSM-III-R and DSM-IV social phobia. Sixty-six patients were given the International Personality Disorder Examination and questionnaires including the Beck Anxiety Inventory. Among the 23 DSM-III-R personality disorder patients, 8 patients were diagnosed as having avoidant personality disorder. Six of them were suffering from taijin kyoufu symptoms. Among 27 ICD personality disorder patients, 22 patients were diagnosed as having ICD anxious personality disorder. All DSM avoidant patients were included in the ICD anxious group. These findings suggest that patients with avoidant personality disorder have had a long history of difficulties and share common personality problems with a milder form of taijin kyoufu, which is conceptually different from social phobia.

Penicillin-binding protein 5 as an inhibitory target of cefozopran in Enterococcus faecalis

The concentration of cefozopran which inhibits binding of [14C]benzylpenicillin to penicillin-binding protein (PBP) 5 of Enterococcus faecalis TN2OO5 by 50% was 11 mg/L, and its MIC was 12.5 mg/L. Ceftazidime and cefmenoxime, which were inactive at 100 mg/L, showed no affinity for PBP 5 at this concentration. Ampicillin, benzylpenicillin and imipenem showed higher affinity for PBPs 3/4 and PBP 5 than cefozopran, and their MICs were lower than that of cefozopran. No correlation between MICs of the test compounds and the affinity for PBP 1, 2 or 6 was found. These results suggest that cefozopran exhibits antimicrobial activity against E. faecalis TN2OO5 by binding to PBP 5.

Optically active antifungal azoles. VI. Synthesis and antifungal activity of N-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazo l-1- yl)propyl]-N'-(4-substituted phenyl)-3(2H,4H)-1,2,4-triazolones and 5(1H,4H)-tetrazolones

A new series of optically active antifungal azoles, N-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-tria zol-1- yl)propyl]-N'-(4-substituted phenyl)-3(2H,4H)-1,2,4-triazolones (1,2) and 5(1H,4H)-tetrazolones (3), were prepared from the triflate derivative of (1S)-1-[(2R)-2-(2,4-difluorophenyl)-2-oxiranyl]ethanol (13) by an SN2 displacement reaction with the anion of an azolone (17-19) and subsequent ring-opening reaction with 1H-1,2,4-triazole. The optically active oxiranylethanol 13 was synthesized from methyl (R)-lactate in a stereo-controlled manner. The azolones 1-3 prepared showed potent antifungal activities in vitro and in vivo.

Optically active antifungal azoles. IV. Synthesis and antifungal activity of (2R,3R)-3-azolyl-2-(substituted phenyl)-1-(1H-1,2,4-triazol-1-yl)-2-butanols

(2R,3R)-3-Azolyl-2-(substituted phenyl)-1-(1H-1,2,4-triazol-1-yl)-2-butanols (III) were prepared from (2R,3S)-3-methyl-2-(substituted phenyl)-2-(1H-1,2,4-triazol-1-yl)methyloxiranes (21a-f) by a ring-opening reaction with 1H-1,2,3-triazole and 1H-tetrazole and evaluated for antifungal activity against Candida albicans in vitro and in vivo. The optically active oxiranes (21a--f) which serve as the key synthetic intermediates, were synthesized from 1-[(2R)-2-(3,4,5,6-tetrahydro-2H-pyran-2-yl)oxypropanoyl]morpholin e (24) and substituted phenylmagnesium bromide (23) via six steps in a stereocontrolled manner. The 3-(1H-1,2,3,-triazol-1-yl)-(IIIa) and 3-(2H-2-tetrazolyl)-2-butanol (IIId) derivatives showed strong protective effects against candidosis in mice.

Optically active antifungal azoles. V. Synthesis and antifungal activity of stereoisomers of 3-azolyl-2-(substituted phenyl)-1-(1H-1,2,4-triazol-1-yl)-2- butanols

The (2S,3S)-, (2R,3S)- and (2S,3R)-stereoisomers of (2R,3R)-3-azolyl-2-(substituted phenyl)-1-(1H-1,2,4-triazol-1-yl)-2-butanols [(2R,3R)-1a--d] were prepared and evaluated for antifungal activity against Candida albicans in vitro and in vivo to clarify the relationships between stereochemistry and biological activities. The results revealed that the in vitro antifungal activity in each set of the four stereoisomers [(2R,3R)-, (2S,3S)-, (2R,3S)- and (2S,3R)-1a--d] definitely paralleled the in vivo antifungal activity against candidosis in mice, and the order of potency was (2R,3R) >> (2R,3S) > or = (2S,3S) > or = (2S,3R). In addition, the four stereoisomers in each set were assessed for sterol biosynthesis-inhibitory activities in C. albicans and rat liver. The (2R,3R)-isomer was found to exert a strong and selective inhibitory effect on the sterol synthesis in C. albicans as compared with that in rat liver.

Enterococcus faecalis aggravates pyelonephritis caused by Pseudomonas aeruginosa in experimental ascending mixed urinary tract infection in mice

Mixed urinary tract infection was caused by simultaneous inoculation of 10(4) CFU each of Enterococcus faecalis TN2005 and Pseudomonas aeruginosa P9 into the bladders of CBA/J mice. Both organisms proliferated in the kidneys, and viable cell counts of E. faecalis TN2005 reached a peak level of 4.1 x 10(5) CFU per pair of kidneys within the first 24 h, while P. aeruginosa P9 counts increased more slowly. The number of P. aeruginosa P9 cells peaked at 8.3 x 10(6) CFU per pair of kidneys 5 days after infection. Five days after mixed infection, infiltration of neutrophils into the renal pelvis and renal medulla was observed. Immunohistochemical staining revealed the presence of E. faecalis antigen in the renal medulla. P. aeruginosa antigen was detected mainly in the renal pelvis 5 days after infection and in the renal medulla as well as the renal pelvis 14 days after infection. Mixed infection induced pyelonephritis within 5 days after mixed infection, while it was not observed until 14 days after infection with P. aeruginosa P9 alone. P. aeruginosa P9 inoculated together with E. faecalis TN2005 was more resistant to eradication from the kidneys by beta-lactam antibiotics than P. aeruginosa P9 inoculated alone. These results suggest that E. faecalis TN2005 invades the renal medulla first in mixed urinary tract infection and induces histological changes which lead to aggravation of the pyelonephritis caused by P. aeruginosa P9.

Optically active antifungal azoles. III. Synthesis and antifungal activity of sulfide and sulfonamide derivatives of (2R,3R)-2-(2,4-difluorophenyl)-3-mercapto-1-(1H-1,2,4-triazol-1-yl)-2-b utanol

In an effort to find potent antifungal agents, optically active sulfur-containing triazole derivatives, sulfides (3) and sulfonamides (4), were prepared and evaluated for antifungal activity against Candida albicans in vitro and in vivo. The sulfides (3) were prepared by the reaction of (2R,3R)-2-(2,4-difluorophenyl)-3-mercapto-1-(1H-1,2,4-triazol-1-yl )-2-butanol (1) with various heteroarylmethyl chlorides in the presence of sodium methoxide. The sulfonamides (4) were synthesized starting from the disulfide (15) in three steps including oxidation of the corresponding sulfenamides (17). Some of the sulfur-containing triazole derivatives (3, 4) showed strong protective effects against candidosis in mice.

Effectiveness in psychiatric care. III: Psychoeducation and outcome for patients with major affective disorder and their families

This hypothesis-generating study had the objective of dissecting the process of psychiatric care in an attempt to understand outcomes for patients and their families. In all, 24 patients who carried a DSM-III diagnosis of major affective disorder were identified 12-18 months after hospital admission. The patients, their families, and their doctors were interviewed using instruments measuring delivery of treatment and achievement of treatment goals; findings were then correlated with resolution of the index episode and patient global outcome. Delivery of patient and family psychoeducation was associated with better resolution of the index episode and better global outcome.

Optically active antifungal azoles. I. Synthesis and antifungal activity of (2R,3R)-2-(2,4-difluorophenyl)-3-mercapto-1-(1H-1,2,4-triazol-1-yl)-2-b utanol and its stereoisomers

(2R,3R)-2-(2,4-Difluorophenyl)-3-mercapto-1-(1H-1,2,4-triazol-1-yl )-2-butano l [(2R,3R)-7] and its stereoisomers [(2S,3R)-, (2S,3S)- and (2R,3S)-7] were prepared from the optically active oxiranes 6 by a newly developed ring-opening reaction and evaluated for antifungal activity. The thiol (2R,3R)-7 showed extremely potent antifungal activity in vitro and in vivo. The optically active oxirane (2R,3S)-6, a useful intermediate for the synthesis of sulfur-containing antifungal azoles 5, was synthesized from methyl (R)-lactate [(R)-8] via eight steps in a stereocontrolled manner. The key step in the synthesis is the Grignard reaction of an amide derivative [(R)-12a] of (R)-lactic acid with 2,4-difluorophenyl-magnesium bromide (13).

Optically active antifungal azoles. II. Synthesis and antifungal activity of polysulfide derivatives of (2R,3R)-2-(2,4-difluorophenyl)-3-mercapto-1-(1H- 1,2,4-triazol-1-yl)-2-butanol

In an effort to find potent antifungal agents, a variety of optically active triazole derivatives with a polysulfide structure, 3, 4 and 5, were prepared and evaluated for antifungal activity against Candida albicans in vitro and in vivo. The symmetrical polysulfides 3 (m = 2-4) were obtained by an oxidative coupling reaction of (2R,3R)-2-(2,4-difluorophenyl)-3-mercapto-1-(1H-1,2,4-triazol-1-yl )-2-butanol (1) or by the treatment of its thiocarbonate derivative 8 with potassium tert-butoxide. The unsymmetrical disulfides 5 were synthesized by the reaction of the thiol 1 with Bunte salts 11 or the thiosulfinate 12 or by the reaction of the thiocarbonate 8 with various thiols 13. All of these polysulfides showed potent antifungal activity against candidosis in mice.

Ferrocins, new iron-containing peptide antibiotics produced by bacteria. Taxonomy, fermentation and biological activity

A Gram-negative bacterium was found to produce new iron-containing peptide antibiotics, ferrocins A, B, C and D, and the producing bacterium was characterized and identified as Pseudomonas fluorescens YK-310. These new antibiotics showed antibacterial activity against Gram-negative bacteria in vitro. Although the ferrocins showed similar antibacterial activity against both Escherichia coli and Pseudomonas aeruginosa on the standard assay media, they showed strong therapeutic effects selectively against P. aeruginosa in experimentally infected mice.

Therapeutic effect of cefozopran (SCE-2787), a new parenteral cephalosporin, against experimental infections in mice

The therapeutic effect of cefozopran (SCE-2787), a new semisynthetic parenteral cephalosporin, against experimental infections in mice was examined. Cefozopran was more effective than cefpiramide and was as effective as ceftazidime and cefpirome against acute respiratory tract infections caused by Klebsiella pneumoniae DT-S. In the model of chronic respiratory tract infection caused by K. pneumoniae 27, cefozopran was as effective as ceftazidime. The therapeutic effect of cefozopran against urinary tract infections caused by Pseudomonas aeruginosa P9 was superior to that of cefpirome and was equal to those of ceftazidime and cefclidin. In addition, cefozopran was more effective than ceftazidime and was as effective as flomoxef in a thigh muscle infection caused by methicillin-sensitive Staphylococcus aureus 308A-1. Against thigh muscle infections caused by methicillin-resistant S. aureus N133, cefozopran was the most effective agent. The potent therapeutic effect of cefozopran in those experimental infections in mice suggests that it would be effective against respiratory tract, urinary tract, and soft tissue infections caused by a variety of gram-positive and gram-negative bacteria in humans.

In vitro and in vivo activities of SCE-2787, a new parenteral cephalosporin with a broad antibacterial spectrum

SCE-2787, a new cephalosporin having a condensed azolium moiety in the 3 position and an aminothiadiazolyl group in the 7 beta side chain, was evaluated for its in vitro and in vivo activities in comparison with those of ceftazidime, flomoxef, cefpirome, and E1040. Against methicillin-susceptible strains of Staphylococcus aureus and Staphylococcus epidermidis, SCE-2787 was more active than ceftazidime and E1040 and was as active as flomoxef and cefpirome, with MICs for 90% of strains tested (MIC90s) being 1.56 micrograms/ml or less. SCE-2787 was also active against Pseudomonas aeruginosa, for which the MIC90 was 6.25 micrograms/ml, which was lower than that of cefpirome and comparable to that of ceftazidime. SCE-2787 was marginally active against methicillin-resistant strains of staphylococci and Enterococcus faecalis, although its MIC90s were the lowest among those of the antibiotics tested. The activities of SCE-2787 against Streptococcus species, most members of the family Enterobacteriaceae, and Haemophilus influenzae exceeded those of ceftazidime and flomoxef and were comparable to those of cefpirome. Furthermore, MIC90s of SCE-2787 were significantly lower than those of ceftazidime for ceftazidime-resistant isolates of Citrobacter freundii and Enterobacter cloacae. SCE-2787 was resistant to hydrolysis by various types of beta-lactamases, including the Bush group 1 beta-lactamases, and had low affinities for these enzymes, with Km or Ki values of greater than 100 microM. The in vitro activity of SCE-2787 was reflected in its efficacy in mouse protection tests. Thus, SCE-2787 appears to be a promising cephalosporin that should be further evaluated in clinical trials.

[A case of penicillin-resistant pneumococcal pneumonia and penicillin-binding proteins of the clinical isolates]

We experienced a case of a 68-year-old female with beta-lactam antibiotics including penicillin G (PCG) resistant pneumococcal pneumonia, leading to death during the treatment with ceftizoxime (CZX). We reported the clinical course and the mechanism of resistance of isolated bacteria. The present case is the first in Japan. Minimum inhibitory concentration (MIC) against Streptococcus pneumoniae 88031 isolated from the present case was 1.56 micrograms/ml in PCG and 6.25 micrograms/ml in CZX, showing PCG resistance. The isolate was no beta-lactamase production and serotype 23. The drug susceptibility in 34 strains of S. pneumoniae which were isolated as causative organism of respiratory infection in our department in 1988 was studied. PCG high resistant strain (PCG MIC greater than 1.56 micrograms/ml) was only observed in the isolated strain in the present case and PCG low sensitive strains (PCG MIC = 0.1-1.0 micrograms/ml) were observed in 3 strains (8.8%). The CZX resistance was observed only in the present case. The detection of penicillin-binding protein (PBP) and binding affinity of beta-lactam antibiotics were studied using PCG sensitive strain, S. pneumoniae type I (preserved strain PCG MIC = 0.05 micrograms/ml, CZX MIC = 0.1 micrograms/ml, CMX MIC = 0.025 micrograms/ml) and PCG resistant strain, S. pneumoniae 88031. The result obtained showed that PBP1a, detected in sensitive strain type I, was not detected in resistant strain 88031 and PBP1b was increased. The binding of 14C-PCG of PCG resistant strain to PBP1b showed lower affinity for CZX and CMX than PCG sensitive strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular cloning and nucleotide sequence determination of the regulator region of mecA gene in methicillin-resistant Staphylococcus aureus (MRSA)

Molecular cloning and nucleotide sequence analysis were performed for the identification of the regulator genes of methicillin resistance in the genome of a MRSA strain N315. Two open reading frames (orfs) were identified in the 5'-flanking region of the mecA gene. Predicted amino acid sequences of these orfs showed extensive homology to the co-inducer and the repressor protein of the penicillinase (PCase) production in Staphylococcus aureus as well as in Bacillus licheniformis. These orfs are considered to encode putative co-inducer and repressor proteins specific for the regulation of methicillin resistance in MRSA.

Inhibition of prostaglandin E2-stimulated cAMP accumulation by lipopolysaccharide in murine peritoneal macrophages

Treatment of murine peritoneal macrophages with 100 nM prostaglandin E2 (PGE2) produced a rapid biphasic increase in intracellular cAMP that was maximal at 1 min and sustained through 20 min. Pretreatment of macrophages with 100 ng/ml of lipopolysaccharide (LPS) for 60 min prior to PGE2 decreased the magnitude of cAMP elevation by 50%, accelerated the decrease of cAMP to basal levels, and abolished the sustained phase of cAMP elevation. The effect of LPS was concentration-dependent, with maximal effect at 10 ng/ml in cells incubated in the presence of 5% fetal calf serum and at 1 microgram/ml in the absence of fetal calf serum. LPS also inhibited cAMP accumulation in cells treated with 100 microM forskolin, but the decrease was about half that seen in cells treated with PGE2. LPS concentrations that inhibited cAMP accumulation produced a 30% increase in soluble low Km cAMP phosphodiesterase activity while having no effect on particulate phosphodiesterase activity. The nonspecific phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, as well as the more specific inhibitors rolipram and Ro-20-1724 were effective in inhibiting soluble phosphodiesterase activity in vitro, producing synergistic elevation of cAMP in PGE2-treated cells, and blocking the ability of LPS to inhibit accumulation of cAMP. Separation of the phosphodiesterase isoforms in the soluble fraction by DEAE chromatography indicated that LPS activated a low Km cAMP phosphodiesterase. The enzyme(s) present in this peak could be activated 6-fold by cGMP and were potently inhibited by low micromolar concentrations of Ro-20-1724 and rolipram. Using both membranes from LPS-treated cells and membranes incubated with LPS, no decrease in adenylylcyclase activity could be attributed to LPS. Although effects of LPS on the rate of synthesis of cAMP cannot be excluded, the present evidence is most consistent with a role for phosphodiesterase activation in the inhibitory effects of LPS on cAMP accumulation in murine peritoneal macrophages.

[Mechanism of beta-lactam-resistance in methicillin-resistant Staphylococcus aureus]

The role of penicillin-binding protein (PBP) 2' in the expression of beta-lactam-resistance was investigated using methicillin-resistant Staphylococcus aureus (MRSA) strains with different level of resistance. Both high- and moderate-level MRSA produced very similar PBP 2' with low affinities for beta-lactam antibiotics. Affinities of antibiotics for PBP 2' (I50, concentration which inhibits [14C] benzylpenicillin-binding by 50%) correlated well with their antibacterial activities (MIC) in a high-level MRSA, but did not in a moderate-level MRSA. High-level MRSA contained a larger amount of PBP 2' than moderate-level MRSA, and the amount of PBP 2' decreased by increasing the temperature of the culture; the extent of decrease was larger in a strain which was sensitive at 37 degrees C than a strain which exerted relatively high level resistance even at 40 degrees C. A cephamycin-resistant, methicillin-sensitive strain began to synthesize PBP 2' by adding cephamycin-type antibiotics to the medium and consequently acquired resistance to methicillin. Latent MRSA producing no PBP 2' generated clones which produced PBP 2' constitutively and were highly resistant to all beta-lactams. These results suggest that the presence of PBP 2' is critical for the expression of beta-lactam-resistance in MRSA and the degree of the resistance depends mainly on the amount of PBP 2' which differs from strain to strain and is influenced by environments such as temperature and the presence of inducer.

Activation of the cAMP cascade inhibits an early event involved in murine macrophage Ia expression

The ability of interferon-gamma (IFN gamma) to increase class II major histocompatibility complex (class II MHC) gene products in murine macrophages involves activation of Na+/H+ exchange (Prpic V., Yu, S. F., Figueiredo, F., Hollenbach, P. W., Gawdi, G., Herman, B., Uhing, R. J., and Adams, D. O. (1989) Science 244, 469-471). The ability of IFN gamma to increase class II MHC gene product expression is inhibited by a variety of agents. In the present studies, the involvement of cAMP-dependent protein kinase in modulating IFN gamma-induced expression of MHC gene products and the mechanism of regulation were assessed in macrophages treated with agents which activated cAMP-dependent protein kinase by different molecular mechanisms. Prostaglandin E2 (PGE2) produced a rapid (within 30 s) dose-dependent elevation of cAMP which was paralleled by the activation of cAMP-dependent protein kinase. The elevation of cAMP by PGE2 was still evident at 1 h and maintained through a 4-h incubation. Concentrations of PGE2 which activated the protein kinase produced a dose-dependent inhibition of surface expression of I-A and transcription of class II MHC genes. Inhibition of IFN gamma-induced class II MHC gene product expression was also observed in macrophages treated with agents which activated cAMP-dependent protein kinase by postreceptor mechanisms. Dibutyryl-cAMP (0.01-1 mM), 25 microM forskolin, 0.1 micrograms/ml cholera toxin, and 3-isobutyl-1-methylxanthine (0.1-1 mM) each suppressed IFN gamma-induced cell surface I-A expression, class II MHC gene transcription, and 22Na+ influx. The results are consistent with the suggestion that activation of cAMP-dependent protein kinase regulates an early transductional event initiated by IFN gamma, perhaps Na+/H+ exchange, which is involved in regulating transcription of class II MHC genes and their subsequent expression.

Emergence of methicillin-resistant clones from cephamycin-resistant Staphylococcus aureus

Staphylococcus aureus strains specifically resistant to cephamycin antibiotics have been found among recent clinical isolates. These strains formed penicillin-binding protein (PBP) 2' and became phenotypically resistant to methicillin after induction with cefoxitin. Other cephamycin-type antibiotics also induced methicillin-resistance, whereas non-cephamycin-type cephalosporins such as cefmenoxime and ceftizoxime did not do so. The clones that constitutively synthesized PBP 2' arose from the cephamycin-resistant strains at a frequency of 10(-5). They were indistinguishable from clinically isolated methicillin-resistant S. aureus (MRSA). Cephamycin-resistant S. aureus may be a source for emerging MRSA.

Induction of beta-lactamase in Proteus vulgaris

Various beta-lactam antibiotics, including monocyclic beta-lactams, induced the beta-lactamase of Proteus vulgaris; when clinical isolates were induced by benzylpenicillin, each strain produced a single beta-lactamase but the activity per milligram dry weight differed from strain to strain. The beta-lactamases of the P. vulgaris strains were heterogeneous with respect to their isoelectric points, but had almost the same specific activities, substrate specificities and Michaelis constants. The kinetics of beta-lactamase formation were investigated in three strains, each with a different beta-lactamase activity. Differential rates of enzyme synthesis and peak activity depended on the concentration of inducer. The plots of the reciprocals of the differential rates versus the reciprocals of the inducer concentrations were linear, and the maximum rate of enzyme synthesis and the concentration of the inducer giving half-maximum induction were determined from this double reciprocal plot. The maximum rates of enzyme synthesis were different in the three strains. The kinetic analysis of beta-lactamase formation revealed that the beta-lactamase activities in a single bacterial species were determined by differences in the rate of enzyme synthesis and not by differences in the properties of the enzyme.

Interactions of formylamino- and methoxy-substituted beta-lactam antibiotics with beta-lactamases

Cephem and nocardicin-type monocyclic beta-lactam antibiotics with a formylamino substituent were highly resistant to hydrolysis by both penicillinases and cephalosporinases. Among antibiotics with a methoxy substituent, an N-sulfonated monocyclic beta-lactam antibiotic, sulfazecin was resistant to beta-lactamases, but cephem antibiotics were sensitive to the cephalosporinase of Enterobacter cloacae. The resistance of the antibiotics to the beta-lactamases depended primarily on the presence of the substituent, but affinity for the beta-lactamases was affected not only by the substituent but also by the presence of other side chains. Formylamino compounds and sulfazecin were as good inducers of beta-lactamases as semisynthetic 7-methoxycephalosporins, but naturally occurring 7-methoxycephalosporins were poor inducers. The inducer activities of the antibiotics were not necessarily related to their beta-lactamase stabilities. The stabilities of the compounds to the beta-lactamases were well reflected in their antibacterial activities against beta-lactamase producing bacteria.

Formadicins, new monocyclic beta-lactam antibiotics of bacterial origin. I. Taxonomy, fermentation and biological activities

A Gram-negative bacterium produces new monocyclic beta-lactam antibiotics with a formylamino substituent, named formadicins A, B, C and D. The producing bacterium was taxonomically characterized and designated as Flexibacter alginoliquefaciens sp. nov. YK-49. Formadicins have narrow antibacterial spectra. They are highly active against some species of Pseudomonas, Proteus and Alcaligenes. Of the four, formadicin C shows the most potent antibacterial activity. Several amino acids such as glycine, D-alanine and D-leucine were antagonistic against formadicins. Formadicins, especially formadicins A and C having the formylamino substituent bound to the 3-position of a beta-lactam nucleus, were highly resistant to hydrolysis by various types of beta-lactamases. Formadicins A and C showed affinity for penicillin-binding proteins (PBPs) 1A and 1B in Pseudomonas aeruginosa IFO 3080, but formadicin B and nocardicin A showed affinity only for PBP 1B. Formadicins A and C did not lyse Escherichia coli LD-2 solely at their MICs, but when combined with mecillinam each induced a rapid lysis of this organism.

Effect of beta-lactamase induction on susceptibility to cephalosporins in Enterobacter cloacae and Serratia marcescens

For Enterobacter cloacae GN5797 and Serratia marcescens 72-2, which produce inducible beta-lactamases and respond antagonistically to many combinations of cephalosporins, the changes in beta-lactamase activity and sensitivity to cephalosporins were examined during semi-continuous cultivation in which the concentration of inducers was decreased by two-fold dilution of the culture every 30 min starting from 1 h after the addition of inducers. The levels of beta-lactamase, which peaked at 0.5-2 h after induction, decreased concomitantly with the disappearance of the inducers in the culture, and returned to the uninduced levels by 6 h. The ability of cefoxitin and cefmetazole to induce beta-lactamases was more potent than that of cefazolin and cefotiam. The sensitivity to some cephalosporins, judged by the MIC and bactericidal effect, was slightly decreased at an early stage of induction, and reverted to the uninduced levels within several hours after the inducers were depleted.