bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of acute-phase proteins in interleukin-1-induced nonspecific resistance to bacterial infections in mice
Authors: Vogels M T , Cantoni L , Carelli M , Sironi M , Ghezzi P , van der Meer J W
Published: June 2012

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge of granulocytopenic and normal mice enhances nonspecific resistance. Since IL-1 induces secretion of acute-phase proteins, liver proteins which possess several detoxifying effects, we investigated the role of these proteins in the IL-1-induced protection. Inhibition of liver protein synthesis with D-galactosamine (GALN) completely inhibited the IL-1-induced synthesis of acute-phase proteins. GALN pretreatment abolished the protective effect of IL-1 on survival completely (neutropenic mice infected with Pseudomonas aeruginosa) or partially (nonneutropenic mice infected with Klebsiella pneumoniae). Pretreatment with IL-6, a cytokine induced by IL-1, did not reproduce the protection offered after IL-1 pretreatment, nor did it enhance or deteriorate the IL-1-enhanced resistance to infection. A protective effect of IL-1 via effects on glucose homeostasis during the acute-phase response was investigated by comparing plasma glucose levels in IL-1-treated mice and control mice before and during infection. Although glucose levels in IL-1-pretreated mice were somewhat higher in the later stages of infection, no significant differences from levels in control mice were present, and the glucose levels in control-treated animals never fell to hypoglycemic values. We conclude that the IL-1-induced nonspecific resistance is mediated neither by the induction of IL-6 nor by the effects of IL-1 on glucose homeostasis. Acute-phase proteins generated after IL-1 pretreatment, however, seem to play a critical role in the IL-1-induced protection to infection.
Antimicrobial activity of rabbit CAP18-derived peptides
Authors: Larrick J W , Hirata M , Shimomoura Y , Yoshida M , Zheng H , Zhong J , Wright S C
Published: June 2012

A cationic antimicrobial protein of 18 kDa (CAP18) was originally isolated from rabbit granulocytes by using as an assay the agglutination of Re-lipopolysaccharide-coated erythrocytes. The C-terminal 37 amino acids of CAP18 (CAP18(106-142)) make up the lipopolysaccharide-binding domain. Synthetic CAP18(106-142) has broad antimicrobial activity against both gram-positive (50% inhibitory concentration, 130 to 200 nM) and gram-negative (50% inhibitory concentration, 20 to 100 nM) bacteria. Susceptible strains include Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium. Antimicrobial activity is highly dependent on peptide structure. Although a 32-amino-acid peptide resulting from the truncation of 5 amino acids from the C terminus of CAP18(106-142) is highly active, other fragments of CAP18(106-142), including CAP18(106-142) with a truncated N terminus, do not exhibit antimicrobial activity. Unlike previously characterized antimicrobial peptides derived from granulocyte proteins, CAP18(106-142) is active in serum. CAP18(106-142) or a derivative peptide may have therapeutic potential for bacterial sepsis.
In vitro activities of free and liposomal drugs against Mycobacterium avium-M. intracellulare complex and M. tuberculosis
Authors: Mehta R T , Keyhani A , McQueen T J , Rosenbaum B , Rolston K V , Tarrand J J
Published: June 2012

We compared MICs and MBCs of various free- and liposome-incorporated antimicrobial agents against several patient isolates of Mycobacterium avium-M. intracellulare complex and certain American Type Culture Collection strains of M. avium, M. intracellulare, and Mycobacterium tuberculosis. Seven of 19 agents were selected for incorporation into liposomes. The MICs of these agents for 50 and 90% of isolates tested (MIC50s and MIC90s, respectively) ranged from 0.5 to 62 micrograms/ml. Members of the M. avium-M. intracellulare complex were resistant to killing by most of the other agents tested in the free form. However, clofazimine, resorcinomycin A, and PD 117558 showed complete killing of bacteria at concentrations ranging from 8 to 31 micrograms/ml, represented as MBC90s. Among the liposome-incorporated agents, clofazimine and resorcinomycin A had the highest killing effects (MBC90s, 8 and 16 micrograms/ml, respectively). Furthermore, both free and liposome-incorporated clofazimine had equivalent growth-inhibitory and killing effects on all American Type Culture Collection strains of M. avium, M. intracellulare, and M. tuberculosis tested. These results show that the antibacterial activities of certain drugs, particularly those of clofazimine and resorcinomycin, were maintained after the drugs were incorporated into liposomes.
In vitro anti-human immunodeficiency virus (HIV) activity of XM323, a novel HIV protease inhibitor
Authors: Otto M J , Reid C D , Garber S , Lam P Y , Scarnati H , Bacheler L T , Rayner M M , Winslow D L
Published: June 2012

XM323 represents a novel class of potent inhibitors of human immunodeficiency virus (HIV) protease. In vitro studies have shown that inhibition of this enzyme translates into potent inhibition of replication of HIV type 1 (HIV-1) and HIV-2. The inhibition of virus replication was assessed with three assays designed to measure the production of infectious virus, viral RNA, or p24 antigen. The production of mature infectious virions was measured with a yield reduction assay. By this assay, several strains and isolates of HIV-1 and HIV-2 were shown to be susceptible to XM323 in two lymphoid cell lines (MT-2 and H9) and in normal peripheral blood mononuclear cells, with a concentration required for 90% inhibition (IC90) of 0.12 +/- 0.04 microM (mean +/- standard deviation). The production of HIV-1(RF) RNA was measured with an RNA hybridization-capture assay. With this assay, XM323 was shown to be a potent inhibitor of HIV-1(RF) replication, with an IC90 of 0.063 +/- 0.032 microM. A third measure of virus replication, the production of p24 viral antigen, an essential protein component of the virion, was determined with the AIDS Clinical Trial Group-Department of Defense peripheral blood mononuclear cell consensus assay. This assay was used for expanded testing of XM323 against 28 clinical isolates and laboratory strains of HIV-1. XM323 was shown to be equally effective against zidovudine-susceptible and zidovudine-resistant isolates of HIV-1, with an overall IC90 of 0.16 +/- 0.06 microM.
Viral resistance to the thiazolo-iso-indolinones, a new class of nonnucleoside inhibitors of human immunodeficiency virus type 1 reverse transcriptase
Authors: Maass G , Immendoerfer U , Koenig B , Leser U , Mueller B , Goody R , Pfaff E
Published: June 2012

Thiazolo-iso-indolinone derivatives with high specificity toward the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) were identified. The most potent compound, BM +51.0836, inhibited HIV-1 RT at a 50% inhibitory concentration of 90 nM in vitro. In cell culture assays, similar 50% inhibitory concentrations were obtained with high specificity for HIV-1. These substances were equally active against a zidovudine-resistant isolate. No antiviral effect was observed with an HIV-2 isolate. HIV-1 isolates resistant to the thiazolo-iso-indolinones were generated in cell culture, and the nucleotide sequences of the respective RT genes were analyzed subsequently. Comparison of the deduced amino acid sequences with the wild-type sequence showed an amino acid change at position 181 (Tyr to Cys). Substitutions of amino acid Lys-101 and Lys-103 as well as Tyr-181 and/or Tyr-188 by site-directed mutagenesis led to resistance against the thiazolo-iso-indolinones. A chimeric HIV-2 RT, substituted with amino acids at positions 179 to 190 from HIV-1, acquired only partial susceptibility to BM +51.0836.
Effect of mutational alteration of Asn-128 in the putative GTP-binding domain of tetracycline resistance determinant Tet(O) from Campylobacter jejuni
Authors: Grewal J , Manavathu E K , Taylor D E
Published: June 2012

The deduced amino acid sequence of Campylobacter jejuni Tet(O), cloned in Escherichia coli, has shown that it contains the five highly conserved sequences of the GTP-binding domain found in other GTPases. Asn-128 belongs to the G4 motif of such a domain and is involved in hydrogen bonding with the guanine ring of the nucleotide. Substitution of Asn-128 by 11 other amino acids resulted in a decrease in tetracycline resistance, indicating that tetracycline resistance conferred by Tet(O) is related to GTP binding. The effect of the mutations on the GTP-binding domain is discussed with the EF-Tu-GDP complex as a model.
Bioavailability of syrup and tablet formulations of cefetamet pivoxil
Authors: Ducharme M P , Edwards D J , McNamara P J , Stoeckel K
Published: June 2012

Two studies examining the bioavailability of cefetamet pivoxil in healthy male subjects were conducted. In the first, the bioavailabilities of the 250-mg (M250) and M500 tablet formulations of cefetamet pivoxil to be marketed were compared with that of a tablet used in clinical trials. All products were given with food at a dose of 500 mg. In the second study, the bioavailability of the syrup formulation was evaluated under both fasting and nonfasting conditions and compared with that of the M500 tablet formulation given with food. The absolute bioavailabilities of the M500 and M250 tablets (55.0% +/- 8.0% and 55.7% +/- 7.0%, respectively) were not significantly different from that of the clinical-trial formulation (49.8% +/- 8.5%). The newer tablet formulations exhibited faster absorption as evidenced by higher peak concentrations (3.8 [M500] and 3.9 [M250] mg/liter compared with 3.2 mg/liter for the clinical-trial formulation), a shorter time to peak concentration, and a shorter mean absorption time. The syrup formulation was found to have significantly lower absolute bioavailability (37.9% +/- 6.0%) compared with that of the M500 tablet (58.4% +/- 9.0%) when both were given with food. Food had no significant effect on the bioavailability of the syrup, which averaged 34.0% +/- 8.6% under fasting conditions, although absorption was delayed by food (mean absorption time increased from 2.2 to 3.9 h). This contrasts with the results of previous studies documenting significant increases in tablet bioavailability with food. Despite the lower bioavailability of the syrup, unbound-cefetamet concentrations are expected to remain above the MICs for 90% of the strains tested for susceptible organisms for approximately 10 h of the usual 12-h dosing interval with both syrup and tablet formulations of cefetamet pivoxil given with food.
Immunological effects of amphotericin B and liposomal amphotericin B on splenocytes from immune-normal and immune-compromised mice
Authors: Schindler J J , Warren R P , Allen S D , Jackson M K
Published: June 2012

The immunological effects of amphotericin B and liposomal amphotericin B were studied in vitro by measuring B- and T-lymphocyte proliferation on splenocytes from immune-normal, cyclosporine-compromised, and cyclophosphamide-compromised mice. Cellular viability of cells from immune-normal mice was also evaluated. The concentrations used (0, 0.5, 1, 2, 4, 8, and 16 micrograms/ml) encompassed clinically relevant doses. Amphotericin B consistently reduced the abilities of B cells and T cells to proliferate, especially when administered at higher than clinically relevant doses. Direct cytotoxicity probably played only a minor role, since viability studies showed that, compared with its liposomal analog, amphotericin B reduced the number of viable cells by no more than 10%. Clinically relevant doses of liposomal amphotericin B (A. S. Janoff, L. T. Boni, M. C. Popescu, S. R. Minchey, P. R. Cullis, T. D. Madden, T. Tarashi, S. M. Gruner, E. Shyamsunder, M. W. Tate, R. Mendelsohn, and D. Bonner, Proc. Natl. Acad. Sci. USA 85:6122-6126, 1988; R. Mehta, G. Lopez-Berestein, R. Hopfer, K. Mills, and R. L. Juliano, Biochim. Biophys. Acta 770:230-234, 1984) did not inhibit any of the immune parameters examined. Liposomes may, therefore, be a useful means of delivering more drug to a host infected with a fungal organism without further compromising the patient's already suppressed immune system.
Electron microscopic study of the effect of zinc on Tritrichomonas foetus
Authors: Benchimol M , Almeida J C , Lins U , Gonçalves N R , de Souza W
Published: June 2012

At concentrations of 3.1 to 24 mM, zinc inhibits the multiplication of and kills the pathogenic protozoan Tritrichomonas foetus. Transmission electron microscopy showed that the hydrogenosome, a organelle which is involved in the metabolism of pyruvate and the site of formation of molecular hydrogen, constitutes the main site of the initial effect of zinc. The hydrogenosomal vesicle increases its electron density and dimension. Electron spectroscopy imaging and the electron energy loss spectrum showed the presence of zinc, calcium, and oxygen in the electron-dense areas of the hydrogenosome.
Increased renal uptake of gentamicin in endotoxemic rats receiving concomitant thromboxane A2 antagonist therapy
Authors: Tardif M , Bergeron Y , Beauchamp D , Bergeron M G
Published: June 2012

This report describes the effects of endotoxin and a thromboxane receptor antagonist, L-655,240, on kidney function and the intrarenal pharmacokinetics of aminoglycosides. The rationale for these studies was that thromboxane antagonists may eventually be used in combination with aminoglycosides in patients with gram-negative sepsis and endotoxemia. As aminoglycosides are nephrotoxic and endotoxin has already been shown to increase the renal uptake of gentamicin, we investigated the possibility that thromboxane antagonists might interfere with the nephrotoxic potential of both substances. A decrease in the volume of distribution and an increase in the intracortical concentration of gentamicin were observed in animals given endotoxin. Compared with animals given endotoxin alone, those which received endotoxin plus L-655,240 had significant accumulation of gentamicin in the renal cortex and medulla, as determined by the area under the concentration-time curve, and a significant reduction in the total clearance of the antibiotic (P < 0.05). This difference in uptake could not be attributed to hypotension or changes in the glomerular filtration rate or renal plasma flow. L-655,240 alone did not modify gentamicin pharmacokinetics but did decrease p-aminohippuric acid secretion. Thromboxane antagonists in the context of endotoxemia increase intrarenal uptake of aminoglycosides. If these compounds are to be used as therapeutic agents when endotoxin is present, their influence on renal handling of nephrotoxic drugs needs to be considered. Multiple-dosing regimens deserve investigation.
In vitro evaluation of phosphorothioate oligonucleotides targeted to the E2 mRNA of papillomavirus: potential treatment for genital warts
Authors: Cowsert L M , Fox M C , Zon G , Mirabelli C K
Published: June 2012

Papillomaviruses induce benign proliferative lesions, such as genital warts, in humans. The E2 gene product is thought to play a major role in the regulation of viral transcription and DNA replication and may represent a rational target for an antisense oligonucleotide drug action. Phosphorothioate oligonucleotides complementary to E2 mRNAs were synthesized and tested in a series of in vitro bovine papillomavirus (BPV) and human papillomavirus (HPV) models for the ability to inhibit E2 transactivation and virus-induced focus formation. The most active BPV-specific compounds were complementary to the mRNA cap region (ISIS 1751), the translation initiation region for the full-length E2 transactivator (ISIS 1753), and the translation initiation region for the E2 transrepressor mRNA (ISIS 1755). ISIS 1751 and ISIS 1753 were found to reduce E2-dependent transactivation and viral focus formation in a sequence-specific and concentration-dependent manner. ISIS 1755 increased E2 transactivation in a dose-dependent manner but had no effect on focus formation. Oligonucleotides with a chain length of 20 residues had optimal activity in the E2 transactivation assay. On the basis of the above observations, ISIS 2105, a 20-residue phosphorothioate oligonucleotide targeted to the translation initiation of both HPV type 6 (HPV-6) and HPV-11 E2 mRNA, was designed and shown to inhibit E2-dependent transactivation by HPV-11 E2 expressed from a surrogate promoter. These observations support the rationale of E2 as a target for antiviral therapy against papillomavirus infections and specifically identify ISIS 2105 as a candidate antisense oligonucleotide for the treatment of genital warts induced by HPV-6 and HPV-11.
Activity of quinolones in the Ames Salmonella TA102 mutagenicity test and other bacterial genotoxicity assays
Authors: Mamber S W , Kolek B , Brookshire K W , Bonner D P , Fung-Tomc J
Published: June 2012

Eight quinolones were examined for their bacterial mutagenicity in the Ames Salmonella TA102 assay and for their effects in other bacterial genotoxicity assays. In the quantitative Ames plate incorporation assay, all eight quinolones induced His+ deletion reversion in Salmonella tester strain TA102, with maximum reversion observed at about two to eight times the MIC. The quinolones also induced the SOS response. At quinolone concentrations close to the MIC, SOS cell filamentation gene sulA was induced in sulA::lacZ fusion strain Escherichia coli PQ37. RecA-mediated cleavage of lambda repressor in lambda::lacZ fusion strain E. coli BR513 was measurable at about 10 times the MIC, though no induction occurred at 20 micrograms of nalidixic or oxolinic acid per ml. Genotoxicity of quinolones also was observed in the Bacillus subtilis DNA repair assay, in which the mutant strain M45 (recA) was more susceptible to quinolones than its parent strain, H17 (rec+). The results from these analyses indicate that quinolones induce SOS functions and are mutagenic in bacteria; these properties correspond to their antimicrobial activities.
Relationship between antibacterial activity and porin binding of lactoferrin in Escherichia coli and Salmonella typhimurium
Authors: Naidu S S , Svensson U , Kishore A R , Naidu A S
Published: June 2012

The effect of lactoferrin (Lf) on bacterial growth was tested by measuring conductance changes in the cultivation media by using a Malthus-AT system and was compared with the magnitude of 125I-labeled Lf binding in 15 clinical isolates of Escherichia coli. The binding property was inversely related to the change in bacterial metabolic rate (r = 0.91) and was directly related to the degree of bacteriostasis (r = 0.79). The magnitude of Lf-bacterium interaction showed no correlation with the MIC of Lf. In certain strains, Lf at supraoptimal levels reduced the bacteriostatic effect. Thus, the Lf concentration in the growth media was critical for the antibacterial effect. The cell envelopes of Salmonella typhimurium 395MS with smooth lipopolysaccharide (LPS) and its five isogenic rough mutants revealed 38-kDa porin proteins as peroxidase-labeled-Lf-reactive components in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (ligand blot) analysis. However, in the whole cell binding assay, parent strain 395MS demonstrated a very low interaction with 125I-Lf. On the other hand, Lf interaction gradually increased in correspondence with the decrease in LPS polysaccharide moiety in the isogenic rough mutants. Conductance measurement studies revealed that the low-level-Lf-binding (low-Lf-binding) strain 395MS with smooth LPS was relatively insusceptible to Lf, while the high-Lf-binding mutant Rd was more susceptible to Lf. These data suggested a correlation between Lf binding to porins and the Lf-mediated antimicrobial effect. The polysaccharide moiety of LPS shielded porins from the Lf interaction and concomitantly decreased the antibacterial effect.
Use of a predictor panel to evaluate susceptibility testing methods for ampicillin-sulbactam
Authors: Bradford P A , Sanders C C
Published: June 2012

A predictor panel of clinical isolates that produce a variety of types and amounts of beta-lactamases was used to assess the accuracies of a variety of susceptibility tests for ampicillin-sulbactam. Combinations of ampicillin-sulbactam in ratios of 1:1 and 2:1 and with sulbactam held constant at concentrations of 4 and 8 micrograms/ml were examined in dilution tests performed in agar and broth. In addition, disks containing 10/10, 20/10, 20/20, and 20/30 micrograms of ampicillin-sulbactam were examined in diffusion tests. The results indicated that the MICs obtained in broth microdilution tests performed with each of the four combinations differed, on average, less than twofold. Of the disks tested, the 20/10-micrograms ampicillin-sulbactam disk provided the best separation between susceptible and resistant strains when interpretive criteria for resistance was a zone size of < or = 16 mm and that for susceptibility was a zone size of > or = 21 mm. This disk also gave the highest overall agreement with MICs, regardless of the combination used in the broth microdilution test. Discrepancies between agar and broth microdilution MICs were greater than twofold, on average, and this necessitated recommendation of separate criteria for the two methods. Thus, a predictor panel was very useful in identifying the parameters of susceptibility tests that were most accurate in identifying strains that were susceptible and resistant to ampicillin-sulbactam.
Cytochrome P-450 complex formation by dirithromycin and other macrolides in rat and human livers
Authors: Lindstrom T D , Hanssen B R , Wrighton S A
Published: June 2012

Some macrolide antibiotics cause clinical drug interactions, resulting in altered metabolism of concomitantly administered drugs, via formation of an inactive cytochrome P-450 complex. In the present study, the formation of a cytochrome P-450 type I binding spectrum and a metabolic intermediate complex by troleandomycin and dirithromycin was assessed in liver microsomes obtained from untreated rats and phenobarbital- or dexamethasone-pretreated rats. Troleandomycin produced a type I binding spectrum and metabolic intermediate complex in microsomes from dexamethasone- and phenobarbital-pretreated rats. Dirithromycin did not produce a detectable type I binding spectrum but formed a small cytochrome P-450 metabolic intermediate complex (6% of that formed by troleandomycin) in microsomes from dexamethasone-pretreated rats only. The formation of a cytochrome P-450 type I binding spectrum and a metabolic intermediate complex by troleandomycin, erythromycin, dirithromycin, and erythromycylamine was also assessed in microsomes prepared from human livers. Troleandomycin and erythromycin formed a type I binding spectrum and a metabolic intermediate complex which were larger in microsomes from subjects on barbiturate therapy than in microsomes from subjects with no recent barbiturate exposure. Erythromycylamine did not form a detectable type I binding spectrum with any of the human microsomal samples, but a small metabolic intermediate complex was formed with microsomes from a subject on phenobarbital, phenytoin, and propranolol therapy. Dirithromycin did not form a detectable type I binding spectrum or a metabolic intermediate complex in any human liver sample. Preclinical quantitation of the human metabolic intermediate complex may be helpful in predicting the possibility of clinical drug interactions of new drug candidates.
Effects of interleukin-8 on nonspecific resistance to infection in neutropenic and normal mice
Authors: Vogels M T , Lindley I J , Curfs J H , Eling W M , van der Meer J W
Published: June 2012

The effect of treatment with interleukin-8 (IL-8), a neutrophil-activating cytokine, was investigated in normal and neutropenic mice infected with a lethal dose of Pseudomonas aeruginosa, Klebsiella pneumoniae, or Plasmodium berghei. Intraperitoneal (i.p.) IL-8 treatment was associated with accelerated death when IL-8 was administered shortly before i.p. infection with P. aeruginosa or shortly after i.p. infection with P. aeruginosa and K. pneumoniae. Histopathological analyses demonstrated a tendency to more severe organ lesions in IL-8-treated mice. Only nonneutropenic mice that received IL-8 shortly before the infectious challenge and at the site of infection were protected by IL-8. Whether IL-8 is protective of or detrimental to the survival of infection appeared to depend on the presence of bacteria at the injection site and on the presence of neutropenia. IL-8 may be an important participant in the cascade of interacting cytokines that is induced by the lethal infectious challenge.
In vitro activity of CP-99,219, a new fluoroquinolone, against clinical isolates of gram-positive bacteria
Authors: Eliopoulos G M , Klimm K , Eliopoulos C T , Ferraro M J , Moellering R C
Published: June 2012

The in vitro activity of the fluoroquinolone CP-99,219 against gram-positive bacteria was compared with those of five other antimicrobial agents. Against ciprofloxacin-susceptible staphylococci and against streptococci, MICs were < or = 0.12 and < or = 0.5 microgram/ml, respectively. CP-99,219 was also more active than ciprofloxacin against ciprofloxacin-resistant staphylococci, most enterococci, Leuconostoc spp., and lactobacilli.
Powerful bactericidal activity of sparfloxacin (AT-4140) against Mycobacterium tuberculosis in mice
Authors: Lalande V , Truffot-Pernot C , Paccaly-Moulin A , Grosset J , Ji B
Published: June 2012

The bactericidal activities of various monotherapies and combined regimens were compared in mice at different stages after infection with Mycobacterium tuberculosis. These therapies mimicked the initial and continuation phases of chemotherapy for human tuberculosis. As monotherapy, the bactericidal activity of sparfloxacin (SPFX) was dose related; the activity of SPFX at 100 mg/kg of body weight was comparable to that of rifampin (RMP) and was significantly greater than those of isoniazid (INH), pyrazinamide (PZA), or ofloxacin (OFLO) during both the initial and continuation phases of chemotherapy. During the initial phase, the addition of SPFX did not enhance or diminish the activities of the combinations INH-RMP-PZA or RMP-PZA; the combinations SPFX-PZA-streptomycin (SM) and SPFX-PZA-kanamycin (KANA) displayed powerful bactericidal activity. Because the area under the plasma concentration-time curve of SPFX (100 mg/kg) in mice is similar to that of SPFX (400 mg) in humans, the promising bactericidal activity displayed by SPFX in mice might be achieved in humans by administration of the drug in a clinically tolerated dosage. In addition, the combinations SPFX-PZA-SM and SPFX-PZA-KANA may be useful for the treatment of multidrug-resistant tuberculosis.
Molecular basis of rifampin resistance in Mycobacterium leprae
Authors: Honore N , Cole S T
Published: June 2012

Rifampin is currently the most potent drug used in leprosy control programs. We show that the rifampin resistance which emerged in nine patients with lepromatous leprosy, who had received rifampin monotherapy, stemmed from mutations in the rpoB gene, which encodes the beta subunit of RNA polymerase of Mycobacterium leprae. In eight cases missense mutations were found to affect a serine residue, Ser-425, while in the remaining mutant a small insertion was found close to this site. These findings will be of use for the development of a rapid screening procedure, involving the polymerase chain reaction, for monitoring the emergence of rifampin-resistant M. leprae strains.
Effect of obesity on vancomycin pharmacokinetic parameters as determined by using a Bayesian forecasting technique
Authors: Vance-Bryan K , Guay D R , Gilliland S S , Rodvold K A , Rotschafer J C
Published: June 2012

Few data exist concerning the effect of obesity on the pharmacokinetic parameters of vancomycin. The purpose of this investigation was to assess the effect of obesity on vancomycin pharmacokinetic parameters in 95 nonobese and 135 obese adult patients (age range, 18 to 92 years) receiving vancomycin. All subjects had normal renal function as defined by a creatinine concentration in serum of < or = 1.5 mg/dl (mean estimated creatinine clearance +/- 1 standard deviation, 76 +/- 34; range, 23 to 215 ml/min). Vancomycin concentrations in serum were determined by the fluorescence polarization immunoassay. All data for vancomycin concentration in serum versus time for each course of therapy were fitted by using a two-compartment Bayesian forecasting program. Subjects were stratified into nine groups on the basis of the percent difference between actual body weight (ABW) and lean body weight (LBW) (> -10%, -10 to 0%, > 0 to 10%, > 10 to 20%, > 20 to 30%, > 30 to 40%, > 40 to 50%, > 50 to 60%, > 60%). Analysis of variance with post hoc Scheffe's testing revealed that statistically significant differences occurred in terminal disposition half-life (t1/2 beta) between the extremes of modestly obese (group 4) and morbidly obese (group 9, P < 0.05) patients. Similar analysis with distribution volume (V) identified significant differences in patients at or near their LBW (groups 2 to 4) and patients who were morbidly obese (groups 8 and 9, P < 0.05). Multiple regression models for the pharmacokinetic parameters V, t1/2beta, and vancomycin total body clearance were developed to assess the joint predictive power of LBW, ABW, and percent over LBW, controlling for the effects of age, initial creatinine concentration in serum, initial creatinine clearance, and gender. In the final model for V, both ABW and percent over LBW were independent and significant predictors. For total body clearance, only ABW was significant and predictive. Percent over LBW was a significant and independent predictor of t1/2beta. LBW is not predictive of these pharmacokinetic parameters and should not be used for initial dosing. On the basis of these data, ABW appears to be superior to LBW for calculating initial dose requirements for vancomycin.
Cloning and nucleotide sequence of the Campylobacter jejuni gyrA gene and characterization of quinolone resistance mutations
Authors: Wang Y , Huang W M , Taylor D E
Published: June 2012

The gyrA gene of Campylobacter jejuni UA580, which encodes the A subunit of DNA gyrase, was cloned and its nucleotide sequence was determined. An open reading frame of 2,589 nucleotides was identified, which could code for a polypeptide of 863 amino acids with a M(r) of 97 kDa. Both the nucleotide sequence and the putative amino acid sequence show ca. 50% identity with those of other gyrA genes from gram-positive and gram-negative bacteria. The locations of the gyrA gene on genome maps of both C. jejuni UA580 and Campylobacter coli UA417 were determined. Six nalidixic acid-resistant isolates of C. jejuni were shown to carry mutations in gyrA. Three clinical isolates had Thr-86-to-Ile substitutions. Three laboratory mutants had substitutions of Thr-86 to Ile, Asp-90 to Ala, and Ala-70 to Thr, respectively. The mutation at Thr-86, which is homologous to Ser-83 in Escherichia coli, was associated with high-level resistance to ciprofloxacin in C. jejuni.
Pharmacodynamics of a fluoroquinolone antimicrobial agent in a neutropenic rat model of Pseudomonas sepsis
Authors: Drusano G L , Johnson D E , Rosen M , Standiford H C
Published: June 2012

We examined the impact of dose fractionation and altered MICs on survivorship in a neutropenic rat model of Pseudomonas aeruginosa sepsis employing the new fluoroquinolone antibiotic lomefloxacin. Once-daily administration of a drug dose which produced a high peak concentration/MIC (peak/MIC) ratio (ca. 20/1) produced significantly better survivorship compared with regimens employing the same daily dose but on a more fractionated schedule. The use of a smaller dose, producing lower (< 10/1) peak/MIC ratios, did not show this effect, as once-daily and twice-daily regimens produced equivalent results (the area under the concentration-time curve/MIC ratio was linked to survivorship). Challenge with resistant mutants selected for altered MICs of fluoroquinolones (two and four times the MIC for the parent strain, respectively) resulted in markedly diminished survivorship. Challenge with the parent strain and use of a drug dose which produced a peak/MIC ratio identical to that for animals challenged with the mutant for which the MIC was four times that for the parent strain and treated with the larger drug dose produced survivorship curves which were not different. For this animal model, peak/MIC ratio was linked to survivorship, particularly when high ratios (10/1 to 20/1) were obtained. At lower doses, producing peak/MIC ratios < 10/1, the area under the concentration-time curve relative to the MIC appeared to be most closely linked to outcome. The time that levels in plasma exceeded the MIC did not influence survivorship. The hypothesis most likely to explain these findings is that higher peak/MIC ratios can suppress the parent strain and mutant organisms (gyrA and transport mutants) for which the MIC is higher but limited (no more than eight times that for the parent strain).
Suppression of polymorphonuclear leukocyte bactericidal activity by suramin
Authors: Roilides E , Paschalides P , Freifeld A , Pizzo P A
Published: June 2012

Suramin is a polyanionic compound with potent antineoplastic properties. Because polymorphonuclear leukocytes (PMNs) are a crucial component of host defenses against bacteria and fungi, the effects of suramin on PMN function were studied in vitro. PMNs from healthy donors were incubated with concentrations of suramin of 1 to 1,000 micrograms/ml (within and exceeding the therapeutic range) for 30 min, and PMN functional parameters were subsequently assessed. Suramin had no effect on viability, chemotaxis to N-formylmethionyl leucyl phenylalanine, phagocytosis of Candida albicans, or superoxide anion production in response to phorbol myristate acetate and formylmethionyl leucyl phenylalanine. Fungicidal activity against C. albicans blastoconidia was unaffected at a suramin concentration of < 500 micrograms/ml, whereas at higher concentrations a slight suppression was observed (P = 0.04). Bactericidal activity against Staphylococcus aureus was significantly suppressed by concentrations of > or = 100 micrograms/ml (P < 0.01). Phagocytosis of S. aureus was also significantly impaired at > or = 10 micrograms/ml (P < 0.05). The presence of 10% human serum during pretreatment did not abrogate the suramin-induced suppression of bactericidal activity. Treatment of PMNs with granulocyte colony-stimulating factor (4,000 U/ml) for 30 min prior to the addition of suramin (250 micrograms/ml) improved the bactericidal defect (P = 0.02). The PMN functional impairment may be related to increased susceptibility to bacterial infections, and granulocyte colony-stimulating factor may improve the defect.
Activity of ampicillin-sulbactam and oxacillin in experimental endocarditis caused by beta-lactamase-hyperproducing Staphylococcus aureus
Authors: Pefanis A , Thauvin-Eliopoulos C , Eliopoulos G M , Moellering R C
Published: June 2012

Using a rat model of aortic valve infective endocarditis, we previously found that oxacillin was equally effective against an oxacillin-susceptible strain of Staphylococcus aureus and a beta-lactamase-hyperproducing borderline oxacillin-susceptible strain of S. aureus; also, ampicillin-sulbactam was less effective than oxacillin against both isolates and at low doses was less effective against the borderline-susceptible strain than against the fully oxacillin-susceptible strain (C. Thauvin-Eliopoulos, L. B. Rice, G. M. Eliopoulos, and R. C. Moellering, Jr., Antimicrob. Agents Chemother. 34:728-732, 1990). In the present study, we extended this work, using alternative treatment schedules and additional bacterial strains. Extending treatment with low doses of ampicillin-sulbactam (500 and 250 mg/kg of body weight per day, respectively) to 6.5 days resulted in equalization of effectiveness against the previously studied strains BOSSA-1 and OSSA-1 (3.75 +/- 1.61 log10 and 4.71 +/- 1.79 log10 CFU of residual viable bacteria per g, respectively). Against the borderline oxacillin-susceptible strain BOSSA-1, increasing the sulbactam dosage from 500 to 2,000 mg/kg/day while maintaining a fixed dose of ampicillin (1,000 mg/kg/day) by continuous infusion resulted in lower bacterial counts (4.93 +/- 1.84 log10 versus 3.65 +/- 1.26 log10 CFU of residual viable bacteria per g, respectively), but this difference was of only borderline significance; differences in efficacy between the low-dose and high-dose sulbactam regimens were exaggerated when intermittent intravenous administration was used (6.19 +/- 1.90 log10 versus 3.37 +/- 1.41 log10 CFU/g, respectively; P < 0.001). However, for any individual sulbactam dosage, the model of administration (continuous versus intermittent infusion) did not affect the activity of the regimen. When additional strains were used in the model, oxacillin and ampicillin-sulbactam (1,000 plus 2,000 mg/kg/day) were equally effective against both oxacillin-susceptible and borderline oxacillin-resistant strains of S. aureus. These results support the predictions that oxacillin would be clinically effective in the treatment of infections caused by borderline oxacillin-susceptible strains of S. aureus and that, except at very low doses, ampicillin-sulbactam would also be as effective against borderline-susceptible strains as against fully oxacillin-susceptible strains of S. aureus.
In vitro activity of RP59500, an injectable streptogramin antibiotic, against vancomycin-resistant gram-positive organisms
Authors: Collins L A , Malanoski G J , Eliopoulos G M , Wennersten C B , Ferraro M J , Moellering R C
Published: June 2012

The in vitro activity of RP59500, a streptogramin antibiotic, against 146 clinical isolates of vancomycin-resistant gram-positive bacteria was examined. Five strains of the species Enterococcus casseliflavus and Enterococcus gallinarum, for which the MIC of vancomycin was 8 micrograms/ml, were also studied. Twenty-eight vancomycin-susceptible strains of Enterococcus faecalis and Enterococcus faecium were included for comparison. The drug was highly active against Leuconostoc spp., Lactobacillus spp., and Pediococcus spp. (MICs, < or = 2 micrograms/ml). RP59500 was more active against vancomycin-susceptible strains of E. faecium than E. faecalis (MICs for 90% of the strains [MIC90s], 1.0 versus 32 micrograms/ml). Vancomycin-resistant strains of E. faecalis were as resistant to RP59500 as vancomycin-susceptible strains (MIC90, 32 micrograms/ml), but some vancomycin-resistant E. faecium strains were relatively more resistant to the new agent (MIC90, 16; MIC range, 0.5 to 32 micrograms/ml) than were vancomycin-susceptible organisms of this species.
2-Acetylpyridine 5-[(dimethylamino)thiocarbonyl]-thiocarbonohydrazone (1110U81) potently inhibits human cytomegalovirus replication and potentiates the antiviral effects of ganciclovir
Authors: Hamzeh F M , Spector T , Lietman P S
Published: June 2012

We studied the effects of 2-acetylpyridine 5-[(dimethylamino)thiocarbonyl]-thiocarbonohydrazone (1110U81 or A1110U), a potent inhibitor of the ribonucleotide reductases encoded by herpes simplex virus types 1 and 2 and by varicella-zoster virus, against human cytomegalovirus (HCMV) replication in infected MRC-5 cells. We show that 1110U81 is a potent inhibitor of HCMV DNA replication (50% inhibitory concentration [IC50], 3.6 microM; IC90, 5.6 microM) and also potentiates the effects of ganciclovir (GCV) against HCMV. The IC90 of GCV is reduced from 65 microM when GCV alone is given to 2.8 microM when GCV is combined with 1110U81 at a molar ratio of 1:1.
Comparison of high-level gentamicin-resistant Enterococcus faecium isolates from different continents
Authors: Woodford N , Morrison D , Cookson B , George R C
Published: June 2012

Eight clinical isolates of Enterococcus faecium highly resistant to gentamicin (MIC, > 1,000 mg/liter) from patients in six hospitals on three continents were investigated for evidence of spread of either a clone of high-level gentamicin-resistant (HLGR) E. faecium or wide dissemination of a gentamicin resistance (Gmr) plasmid. A combination of ribotypes, plasmid profiles, and extended antimicrobial susceptibilities enabled us to distinguish all but two of the isolates and did not suggest clonal dissemination of a single strain. Two isolates from hospitals situated close together appeared identical by these methods. All of the isolates carried Gmr plasmids which appeared to be closely related following digestion with restriction endonucleases. Cross-hybridization studies confirmed extensive DNA homology between these plasmids. The fragments of these plasmids which hybridized with a probe specific for the aac6'aph2" resistance gene did not resemble those seen in the Gmr transposon Tn5281, which was characterized previously in E. faecalis HH22. This study suggests that there has been widespread dissemination of a single Gmr plasmid and its derivatives amongst isolates of HLGR E. faecium, although a Gmr plasmid from an HLGR E. faecium isolated in the United States showed little homology with the other Gmr plasmids studied.
In vitro antimicrobial activity of a new antibiotic, MDL 62,879 (GE2270 A)
Authors: Goldstein B P , Berti M , Ripamonti F , Resconi A , Scotti R , Denaro M
Published: June 2012

MDL 62,879 (GE2270 A) is a new peptide antibiotic that inhibits protein synthesis through an interaction with elongation factor Tu. MDL 62,879 was very active against gram-positive clinical isolates, particularly staphylococci and enterococci, for which MICs for 90% of isolates were < or = 0.13 micrograms/ml. It was equally active against isolates resistant to beta-lactams, erythromycin, gentamicin, and glycopeptides. It also had activity against Mycobacterium tuberculosis. MDL 62,879 had moderate bactericidal activity against staphylococci.
Antibacterial activity of NM394, the active form of prodrug NM441, a new quinolone
Authors: Yoshida T , Mitsuhashi S
Published: June 2012

The in vitro antibacterial activity of NM394 was compared with those of other new quinolones. NM394 showed potent and broad-spectrum antibacterial activity against 2,606 recent clinical isolates. The activity of NM394 against gram-positive bacteria was 2- to 16-fold less than that of tosulfoxacin and sparfloxacin but was comparable to that of ofloxacin. Only against Streptococcus pyogenes was the activity of NM394 equal to that of sparfloxacin. Against gram-negative bacteria, NM394 showed antibacterial activity equal to that of ciprofloxacin. Against quinolone-resistant Pseudomonas aeruginosa (norfloxacin MIC, > 6.25 micrograms/ml), the activity of NM394 was greater than those of the other agents tested. NM394 was rapidly bactericidal at concentrations near the MIC. NM394 inhibited supercoiling activities of DNA gyrase purified from Staphylococcus aureus, Escherichia coli, and P. aeruginosa; the 50% inhibitory concentrations were 18.0, 0.41, and 2.05 micrograms/ml, respectively.
Mercury released from dental "silver" fillings provokes an increase in mercury- and antibiotic-resistant bacteria in oral and intestinal floras of primates
Authors: Summers A O , Wireman J , Vimy M J , Lorscheider F L , Marshall B , Levy S B , Bennett S , Billard L
Published: June 2012

In a survey of 640 human subjects, a subgroup of 356 persons without recent exposure to antibiotics demonstrated that those with a high prevalence of Hg resistance in their intestinal floras were significantly more likely to also have resistance to two or more antibiotics. This observation led us to consider the possibility that mercury released from amalgam ("silver") dental restorations might be a selective agent for both mercury- and antibiotic-resistant bacteria in the oral and intestinal floras of primates. Resistances to mercury and to several antibiotics were examined in the oral and intestinal floras of six adult monkeys prior to the installation of amalgam fillings, during the time they were in place, and after replacement of the amalgam fillings with glass ionomer fillings (in four of the monkeys). The monkeys were fed an antibiotic-free diet, and fecal mercury concentrations were monitored. There was a statistically significant increase in the incidence of mercury-resistant bacteria during the 5 weeks following installation of the amalgam fillings and during the 5 weeks immediately following their replacement with glass ionomer fillings. These peaks in incidence of mercury-resistant bacteria correlated with peaks of Hg elimination (as high as 1 mM in the feces) immediately following amalgam placement and immediately after replacement of the amalgam fillings. Representative mercury-resistant isolates of three selected bacterial families (oral streptococci, members of the family Enterobacteriaceae, and enterococci) were also resistant to one or more antibiotics, including ampicillin, tetracycline, streptomycin, kanamycin, and chloramphenicol. While such mercury- and antibiotic-resistant isolates among the staphylococci, the enterococci, and members of the family Enterobacteriaceae have been described, this is the first report of mercury resistance in the oral streptococci. Many of the enterobacterial strains were able to transfer mercury and antibiotic resistances together to laboratory bacterial recipients, suggesting that the loci for these resistances are genetically linked. Our findings indicate that mercury released from amalgam fillings can cause an enrichment of mercury resistance plasmids in the normal bacterial floras of primates. Many of these plasmids also carry antibiotic resistance, implicating the exposure to mercury from dental amalgams in an increased incidence of multiple antibiotic resistance plasmids in the normal floras of nonmedicated subjects.
Clarithromycin therapy of experimental Treponema pallidum infections in hamsters
Authors: Alder J , Jarvis K , Mitten M , Shipkowitz N L , Gupta P , Clement J
Published: June 2012

Clarithromycin was shown to be effective therapy for Treponema pallidum infections in hamsters. Clarithromycin therapy was effective when initiated either 1 or 8 days after infection. The delay in initiation of therapy allowed an active infection to develop. The treponemal burden in lymph tissue of treated hamsters was eradicated, as determined by dark-field microscopy and by inoculation of lymph material into susceptible hamsters. Treatments with clarithromycin and the 14-hydroxy metabolite of clarithromycin were equally effective. Therapy with clarithromycin and penicillin was not antagonistic and did not appear to be synergistic when the two drugs were given concurrently. Pharmacokinetic evaluation of clarithromycin in hamsters showed that the doses which produced effective therapy yielded concentrations in serum similar to those routinely achieved in human sera. These findings demonstrate that clarithromycin is effective in treating active or incubating syphilis in the hamster model and could be useful in treating humans.
Curative and preventive anticryptosporidium activities of sinefungin in an immunosuppressed adult rat model
Authors: Brasseur P , Lemeteil D , Ballet J J
Published: June 2012

An immunosuppressed rat model was used to investigate the anti-Cryptosporidium parvum activity of sinefungin. In infected animals, oral sinefungin therapy resulted in a dose-related suppression of oocyst shedding, which correlated with oocyst disappearance from ileal sections. When administered prior to or on the day of oocyst challenge, sinefungin successfully prevented infection. These data suggest that sinefungin could be considered as a candidate molecule in the treatment of human cryptosporidiosis, considered to be the most significant enteric opportunistic infection in AIDS.