bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative activities of clavulanic acid, sulbactam, and tazobactam against clinically important beta-lactamases
Authors: Payne D J , Cramp R , Winstanley D J , Knowles D J
Published: June 2012

Clavulanic acid, sulbactam, and tazobactam are inhibitors of a variety of plasmid-mediated beta-lactamases. However, inhibition data for these three inhibitors with a wide range of different plasmid-mediated beta-lactamases have not yet been compared under the same experimental conditions. A number of groups have inferred that clavulanic acid inhibits extended-spectrum TEM and SHV beta-lactamases, but inhibition data have rarely been published. In this study, the 50% inhibitory concentrations of these three beta-lactamase inhibitors for 35 plasmid-mediated beta-lactamases have been determined. Of these 35 beta-lactamases, 20 were extended-spectrum TEM- or SHV-derived beta-lactamases. The other 15 enzymes were conventional-spectrum beta-lactamases such as TEM-1 and SHV-1. Clavulanic acid was a more potent inhibitor than sulbactam for 32 of the 35 plasmid-mediated beta-lactamases tested. In particular, clavulanic acid was 60 and 580 times more potent than sulbactam against TEM-1 and SHV-1, respectively, currently the two most clinically prevalent gram-negative plasmid-mediated beta-lactamases. Statistical analysis of the data of the 50% inhibitory concentrations showed that clavulanic acid was 20 times more active overall than sulbactam against the conventional-spectrum enzymes. In addition, clavulanic acid was 14 times more potent than sulbactam at inhibiting the extended-spectrum enzymes. Tazobactam also showed significantly greater activity than sulbactam against the two groups of beta-lactamases. There were no significant differences between the overall activities of tazobactam and clavulanic acid against the extended-spectrum TEM and SHV enzymes and conventional-spectrum enzymes, although differences in their inhibition profiles were observed.
Comparative serum bactericidal activities of three doses of ciprofloxacin administered intravenously
Authors: Dan M , Poch F , Quassem C , Kitzes R
Published: June 2012

The pharmacokinetics and serum bactericidal activities of three intravenous doses of ciprofloxacin were studied comparatively in 30 patients. Single 200-, 300-, and 400-mg intravenous doses of ciprofloxacin were given over 30 min to 10 patients each, and serum samples were obtained at 0.5, 1, 2, 3, 4, 8, and 12 h after the start of the infusion. Serum drug concentrations were determined by high-pressure liquid chromatography. Pharmacokinetic parameters were estimated by using noncompartmental analysis methods. Serum bactericidal activity against clinical isolates of Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter calcoaceticus, and Staphylococcus aureus was determined for samples obtained at 0.5, 4, 8, and 12 h. Excellent activity was demonstrated up to 12 h by all doses against E. coli and E. cloacae. Much poorer titers were observed for the remaining organisms, although the 400-mg dose prompted improved results against P. aeruginosa with a mean bactericidal titer of 1:2.9 at 8 h. In conclusion, while the 200-mg dose appears to be largely adequate for infections caused by members of the family Enterobacteriaceae, it seems that when P. aeruginosa is involved, 400 mg twice a day or even three times a day is more appropriate. Intravenous ciprofloxacin performs poorly against A. calcoaceticus and S. aureus, even at a higher dose.
Low bioavailability of amoxicillin in rats as a consequence of presystemic degradation in the intestine
Authors: Chesa-Jiménez J , Peris J E , Torres-Molina F , Granero L
Published: June 2012

Several studies have been carried out to elucidate the causes of the low oral bioavailability of amoxicillin in rats. The hepatic first-pass effect of the antibiotic was estimated by comparing the area under the plasma drug concentration-versus-time curve from time zero to infinity (AUC0-infinity) obtained after injecting the drug into a mesenteric vein with the AUC0-infinity value obtained after injecting the drug into the jugular vein of conscious rats. No hepatic first-pass effect was detected. The bioavailability of amoxicillin after intraduodenal administration was only 51%, and the fraction of the dose remaining in the intestine at the end of the experiment was 4.5%. This was far less than the fraction that did not reach systemic circulation, which indicates a presystemic loss of drug, probably at the intestine. In vitro studies corroborated the fact that amoxicillin is subjected to presystemic degradation by intestinal juices and intestinal tissues. The greatest loss of drug occurred in the complete intestine (45% of the initial amount), and it was mainly due to the action of intestinal tissues (28% of the initial amount) but was also due to the action of intestinal juices (15% of the initial amount). The absorption of amoxicillin in three parts of the intestine (upper, middle, and lower) was also evaluated. The largest AUC0-infinity value and the highest plasma drug levels were obtained when amoxicillin absorption took place in the middle intestine. The smallest AUC0-infinity value and the lowest plasma drug levels corresponded to absorption from the upper intestine.
Killing acanthamoebae with polyaminopropyl biguanide: quantitation and kinetics
Authors: Burger R M , Franco R J , Drlica K
Published: June 2012

The two Acanthamoeba species most often implicated in corneal keratitis, A. castellanii and A. polyphaga, were exposed as cysts to polyaminopropyl biguanide (PAPB), a commonly used antimicrobial agent. Killing of amoeba cysts was rapid and extensive, with fewer than 2% of either species surviving 30 s of exposure to > or = 45 ppm of PAPB. Killing kinetics were biphasic, and further exposures of 15 min to 1 h killed greater than 90% of those surviving initial killing. This potency of PAPB, together with its low toxicity to humans when ingested or applied topically, underscores the potential of PAPB as an antiamoebic agent.
Susceptibilities of 177 penicillin-susceptible and -resistant pneumococci to FK 037, cefpirome, cefepime, ceftriaxone, cefotaxime, ceftazidime, imipenem, biapenem, meropenem, and vancomycin
Authors: Spangler S K , Jacobs M R , Appelbaum P C
Published: June 2012

MICs of six extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, FK 037, cefpirome, cefepime), three carbapenems (imipenem, meropenem, biapenem), and vancomycin for 49 penicillin-susceptible (S), 77 penicillin intermediate-resistant (I), and 51 penicillin-resistant (R) pneumococci were determined by agar dilution. Compared with ceftazidime (MICs for 90% of strains tested [MIC90s] of 2.0, 16.0, and 16.0 micrograms/ml for S, I, and R strains, respectively), all other cephalosporins yielded lower MICs (MIC90s of 0.06 to 0.125, 0.5 to 1.0, and 1.0 to 2.0 micrograms/ml against S, I, and R strains, respectively). All three carbapenems were very active, with MIC90s, even for R strains, of < or = 1.0 micrograms/ml. All strains were susceptible to vancomycin (MIC90 of 0.5 micrograms/ml).
Beta-lactams versus glycopeptides in treatment of subcutaneous abscesses infected with Staphylococcus aureus
Authors: Wood C A , Wisniewski R M
Published: June 2012

The antibacterial efficacies of the beta-lactam antibiotics nafcillin and cefazolin were compared with those of the glycopeptide antibiotics vancomycin and teicoplanin in rats with subcutaneous abscesses infected with methicillin-susceptible Staphylococcus aureus. Animals were treated with antibiotics or diluent for 3 or 7 days. Rats receiving any antibiotic treatment, with the exception of teicoplanin-treated animals at day 7, had lower bacterial counts in their abscesses than did controls at days 3 and 7. Rats in the nafcillin and cefazolin treatment groups had lower bacterial counts in their abscesses than did rats in the vancomycin and teicoplanin treatment groups at days 3 and 7. The beta-lactam antibiotics were more effective therapy than the glycopeptide antibiotics in rats with subcutaneous abscesses infected with methicillin-susceptible S. aureus. In vitro, animal, and clinical data comparing beta-lactam and glycopeptide treatment of S. aureus infections were reviewed along with the resulting treatment recommendations.
Attenuation by daptomycin of gentamicin-induced experimental nephrotoxicity
Authors: Thibault N , Grenier L , Simard M , Bergeron M G , Beauchamp D
Published: June 2012

Previously, daptomycin was shown to reduce tobramycin nephrotoxicity in vivo (D. Beauchamp, M. Pellerin, P. Gourde, M. Pettigrew, and M. G. Bergeron, Antimicrob. Agents Chemother. 34:139-147, 1990; C. A. Wood, H. C. Finkbeiner, S. J. Kohlhepp, P. W. Kohnen, and D. C. Gilbert, Antimicrob. Agents Chemother. 33:1280-1285, 1989). Female Sprague-Dawley rats were treated with saline (NaCl, 0.9%), daptomycin (10 mg/kg of body weight every 12 h, subcutaneously), gentamicin (30 mg/kg/12 h, intraperitoneally) or with a combination of daptomycin plus gentamicin over a 10-day period. Animals were killed 4, 10, and 20 days after the end of treatment. Four days after the end of drug administration, gentamicin and daptomycin levels in the renal cortices of animals treated with the combination of daptomycin and gentamicin were significantly higher than in those of rats given gentamicin or daptomycin alone (P < 0.01). Despite the higher cortical concentrations of gentamicin, rats given the combination of gentamicin and daptomycin had less reduction in renal cortex sphingomyelinase activity, less evidence of regeneration of cellular cortical cells ([3H]thymidine incorporation into cortex DNA), lower creatinine concentration in serum, and less histopathologic evidence of injury than rats given gentamicin alone. By immunogold technique, both daptomycin and gentamicin were localized to the lysosomes of proximal tubular cells, regardless of whether animals received the drugs alone or in combination. Interestingly, myeloid body formation occurred in both those animals given gentamicin alone and those given daptomycin plus gentamicin. No significant changes were observed for all groups between 10 and 20 days after the end of therapy, suggesting that the toxicity of gentamicin was not delayed by the concomitant injection of daptomycin. The results confirm that daptomycin can attenuate experimental gentamicin nephrotoxicity.
Cloning and sequence analysis of ermQ, the predominant macrolide-lincosamide-streptogramin B resistance gene in Clostridium perfringens
Authors: Berryman D I , Lyristis M , Rood J I
Published: June 2012

The erythromycin resistance determinant from Clostridium perfringens JIR100 has been cloned, sequenced, and shown to be expressed in Escherichia coli. An open reading frame with sequence similarity to erm genes from other bacteria was identified and designated the ermQ gene. On the basis of comparative sequence analysis, it was concluded that the ermQ gene represented a new Erm hybridization class, designated ErmQ. Genes belonging to the ErmQ class were found to be widespread in C. perfringens, since 30 of 38 macrolide-lincosamide-streptogramin B-resistant C. perfringens strains, from diverse sources, hybridized to an ermQ-specific gene probe. The ermQ gene therefore represents the most common erythromycin resistance determinant in C. perfringens.
In vitro and in vivo evaluations of A-80556, a new fluoroquinolone
Authors: Clement J J , Tanaka S K , Alder J , Vojtko C , Beyer J , Hensey D , Ramer N , McDaniel D , Chu D T
Published: June 2012

A-80556 is a novel fluoroquinolone with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. A-80556 was more active than ciprofloxacin, ofloxacin, lomefloxacin, and sparfloxacin against gram-positive bacteria. A-80556 was particularly active against Staphylococcus aureus (MIC for 90% of isolates [MIC90], 0.12 microgram/ml, relative to fluoroquinolone-susceptible strains) and Streptococcus pneumoniae (MIC90, 0.12 microgram/ml). A-80556 was also the most active of the quinolones tested against ciprofloxacin-resistant S. aureus, with an MIC90 of 4.0 micrograms/ml; that of ciprofloxacin was > 128 micrograms/ml. However, the significance of this activity is not known. A-80556 was slightly less active against Escherichia coli (MIC90, 0.06 microgram/ml) and other enteric organisms than ciprofloxacin (MIC90 for E. coli, < or = 0.03 microgram/ml). A-80556 was slightly less active against Pseudomonas aeruginosa (MIC90, 4.0 micrograms/ml) than ciprofloxacin (MIC90, 2.0 micrograms/ml) and more active against Acinetobacter spp. (respective MIC90s, 0.12 and 0.5 microgram/ml). A-80556 was also the most active compound against anaerobes. Against Bacteroides fragilis, the MIC90 of A-80556 was 2.0 micrograms/ml; that of ciprofloxacin was 16 micrograms/ml. The in vivo efficacy of A-80556 in experimental models with both gram-positive and gram-negative infections was consistent with the in vitro activity and pharmacokinetics and oral absorption in mice.
Optimal times above MICs of ceftibuten and cefaclor in experimental intra-abdominal infections
Authors: Onyeji C O , Nicolau D P , Nightingale C H , Quintiliani R
Published: June 2012

The duration of time that serum drug levels remain above the MIC (time above the MIC) for the pathogen has been shown to be the most significant parameter determining the efficacies of beta-lactam antibiotics. In the described study, we investigated the optimal time above the MIC of ceftibuten and cefaclor using a nonneutropenic mouse model of intra-abdominal infections caused by Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Streptococcus pneumoniae. The abilities of the drugs to protect mice against the organisms were determined in mouse protection tests, and the doses were fractionated to produce various dosing regimens with different times above the MIC. All drug-organism combinations showed a significant correlation (r > 0.9) between drug efficacy and the time above the MIC. Also, with ceftibuten treatment, the different dosing regimens that produced equal times above the MIC resulted in the same efficacy, whereas with cefaclor, an apparent dose-dependent effect was observed. These results showed that for a 100% recovery from K. pneumoniae and E. coli infections, the optimal times above the MIC with ceftibuten treatment were 2.2 and 1.6 h, respectively. Relatively high doses of both antibiotics were required to ensure recovery from S. pneumoniae infections. In vitro time-kill studies demonstrated that cefaclor exhibits a marked inoculum effect against the pathogens, and there was a concentration-dependent killing at a large inoculum size. On the other hand, ceftibuten showed no inoculum effect. It is suggested that optimization of both dose and time above the MIC appears to be necessary for the treatment of S. aureus infections with cefaclor, and this may apply to other beta-lactams tht exhibit marked inoculum effects.
Reversal of clavulanate resistance conferred by a Ser-244 mutant of TEM-1 beta-lactamase as a result of a second mutation (Arg to Ser at position 164) that enhances activity against ceftazidime
Authors: Imtiaz U , Manavathu E K , Mobashery S , Lerner S A
Published: June 2012

The mutation of Arg-244 to Ser (Arg-244-->Ser mutation) in the TEM-1 beta-lactamase has been shown to produce resistance to inactivation by clavulanate in the mutant enzyme and resistance to ampicillin plus clavulanate in a strain of Escherichia coli producing this enzyme. The Arg-164-->Ser mutation in the TEM-1 beta-lactamase (TEM-12 enzyme) is known to enhance the activity of the enzyme against ceftazidime, resulting in resistance to the drug in a strain producing the mutant enzyme (D. A. Weber, C. C. Sanders, J. S. Bakken, and J. P. Quinn, J. Infect. Dis. 162:460-465, 1990). The doubly mutated derivative of the TEM-1 enzyme (Ser-164/Ser-244) retains the characteristics of the Ser-164 mutant enzyme, i.e., enhanced activity against ceftazidime and sensitivity to inactivation by clavulanate. It also confers the same phenotype as the Ser-164 mutant enzyme, i.e., resistance to ceftazidime and ampicillin, with reversal of this resistance in the presence of clavulanate. Thus, the Arg-164-->Ser mutation in the TEM-1 beta-lactamase suppresses the effect of the Arg-244-->Ser mutation which, by itself, reduces the sensitivity of the enzyme to inactivation by clavulanate.
3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors lovastatin and simvastatin inhibit in vitro development of Plasmodium falciparum and Babesia divergens in human erythrocytes
Authors: Grellier P , Valentin A , Millerioux V , Schrevel J , Rigomier D
Published: June 2012

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors lovastatin and simvastatin inhibit the in vitro intraerythrocytic development of Plasmodium falciparum and Babesia divergens, with concentrations inhibiting parasite growth by 50% in the ranges of 10 to 20 and 5 to 10 micrograms.ml-1, respectively. For P. falciparum, the 50% inhibitory concentrations were in the same range whatever the chloroquine susceptibility of the strains tested (strain F32/Tanzania [chloroquine susceptible] or FcB.1/Columbia [resistant]). The stage-dependent susceptibility of P. falciparum to simvastatin was studied by subjecting synchronized cultures to 6-h pulses of drug throughout the 48-h erythrocytic life cycle. The most important inhibitory effects were observed between the 12th and 30th hours of the cycle, corresponding to the trophozoite stage. This period precedes the S phase and the nuclear divisions. Parasites in the newly formed ring stage (time zero to the 6th hour of the cycle) and the schizont stage (30th to 48th hour of the cycle) were weakly or not susceptible to simvastatin pulses.
Inhibitory and bactericidal activities of levofloxacin against Mycobacterium tuberculosis in vitro and in human macrophages
Authors: Mor N , Vanderkolk J , Heifets L
Published: June 2012

Levofloxacin exhibited twofold greater inhibitory and bactericidal activities than ofloxacin against either extracellular or intracellular tubercle bacilli. The activities of both drugs against extracellular and intracellular bacteria were about the same, despite the accumulation of the drugs in macrophages at a level four- to fivefold greater than that in the extracellular medium. The activities of both drugs against intracellular bacteria were largely associated with the short, 2-h pulsed exposures of the infected macrophages to the concentrations which correspond to those attainable in blood during the period of the maximum concentration of drug in serum.
Levels of dapsone and pyrimethamine in serum during once-weekly dosing for prophylaxis of Pneumocystis carinii pneumonia and toxoplasmic encephalitis
Authors: Opravil M , Joos B , Lüthy R
Published: June 2012

Concentrations of dapsone, monoacetyldapsone, and pyrimethamine were determined in 36 serum samples from human immunodeficiency virus-infected patients on prophylaxis with once-weekly administration of dapsone-pyrimethamine (200 mg of dapsone-75 mg of pyrimethamine). During day 1 after ingestion, median levels of 1,038 ng of dapsone per ml and 356 ng of pyrimethamine per ml were found. During days 6 to 7, the dapsone level fell to < 20 ng/ml in five of nine serum samples, but the pyrimethamine level remained elevated (125 ng/ml). Concurrent, but separately ingested, didanosine administration did not seem to decrease the drug concentrations.
Dextranase enhances antibiotic efficacy in experimental viridans streptococcal endocarditis
Authors: Mghir A S , Cremieux A C , Jambou R , Muffat-Joly M , Pocidalo J J , Carbon C
Published: June 2012

In endocarditis, exopolysaccharide production by viridans streptococci has been associated with delayed antimicrobial efficacy in cardiac vegetations. We compared the efficacies of temafloxacin alone and in combination with dextranase, an enzyme capable of hydrolyzing 20 to 90% of the bacterial glycocalyx, in a rabbit model of endocarditis. In in vivo experiments, rabbits were infected intravenously with 10(8) Streptococcus sanguis organisms and were treated 6 days later with temafloxacin (50 mg/kg of body weight intramuscularly twice a day) alone or combined with dextranase (1,000 U per rabbit per day intravenously). After 4 days of treatment (day 11), the animals were sacrificed and vegetations were quantitatively cultured. For ex vivo experiments, rabbits were infected as stated above and, on day 11, vegetations were excised aseptically and incubated in vitro in rabbit serum alone (control) or with temafloxacin or temafloxacin plus dextranase at concentrations similar to peak levels in plasma. In vitro, dextranase alone had no antimicrobial effect. In vivo and ex vivo, temafloxacin combined with dextranase was more effective than temafloxacin alone (P < 0.05). Our results suggest that dextranase is able to increase the effects of temafloxacin by reducing the amount of bacterial glycocalyx in infected vegetations, as confirmed in vitro by electron microscopy showing a markedly reduced amount of glycocalyx and a more clearly visible fibrin matrix.
Virucidal effect of myeloperoxidase on human immunodeficiency virus type 1-infected T cells
Authors: Chochola J , Yamaguchi Y , Moguilevsky N , Bollen A , Strosberg A D , Stanislawski M
Published: June 2012

Myeloperoxidase is virucidal to human immunodeficiency virus type 1 (HIV-1) in the persistently infected CEM human T-cell line or in acutely infected human peripheral blood mononuclear cells, as judged by viral infectivity and P24 radioimmunoassay. HIV-1 was specifically inactivated by low doses of the human myeloperoxidase (1.4 to 14.3 mU/ml) and the cells were spared. A higher enzyme concentration (143 mU/m) was cytotoxic, but uninfected CEM cells and normal lymphocytes were resistant to > or = 143 mU of myeloperoxidase per ml. The enzyme was virucidal with the Cl- present in medium and did not require exogenous H2O2. Catalase, an antioxidant enzyme, partially inhibited the virucidal effect of myeloperoxidase. Hence, the H2O2 probably came from the HIV-infected cells themselves. These in vitro findings indicate that the myeloperoxidase system is capable of inactivating HIV-1 of infected cells.
Use of biotinylated beta-lactams and chemiluminescence for study and purification of penicillin-binding proteins in bacteria
Authors: Dargis M , Malouin F
Published: June 2012

A new reagent for the detection of penicillin-binding proteins (PBPs) was developed. An N-hydroxysuccinimide ester of biotin was used to tag beta-lactam antibiotics with free side chain amino groups such as ampicillin (BIO-AMP), 6-aminopenicillanic acid (BIO-APA), and 7-aminocephalosporanic acid (BIO-ACA). Bacterial PBPs from cells or isolated cytoplasmic membranes of Escherichia coli, Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pneumoniae were labeled with BIO-AMP, subjected to electrophoresis on sodium dodecyl sulfate (SDS)-polyacrylamide gels, and transferred onto nitrocellulose membranes. Electrophoretic PBP profiles were detected on blots, using colorimetric or chemiluminescence systems, on the basis of the interaction of BIO-AMP-PBP complexes and a streptavidin-peroxidase conjugate. The chemiluminescent reaction permitted a high sensitivity of detection, and PBP profiles could be determined within seconds. All PBP profiles were similar to those obtained with a traditional PBP labeling technique with 125I-labeled penicillin V, except that an additional unidentified PBP (approximately 55,000 Da) was labeled with BIO-AMP in E. coli and H. influenzae. Differences in the intensities of labeling for specific PBPs were observed between the chemiluminescent and radioactive labeling agents and were attributed to the differences in their affinities for PBPs. Similarly, BIO-AMP, BIO-APA, and BIO-ACA produced different PBP profiles. We also investigated the use of BIO-AMP in PBP purification. BIO-AMP-PBP complexes from a mixture of H. influenzae proteins were allowed to bind to avidin immobilized on an agarose support in a microcentrifuge tube. After several washes in the presence of salts, PBPs were eluted by boiling and treatment with SDS. The eluted proteins were separated by electrophoresis on SDS-polyacrylamide gels, and biotinylated proteins were identified on blots by a chemiluminescence reaction. Biotinylation of beta-lactams is rapid, safe, and inexpensive. Our results demonstrate the feasibility of using biotinylated beta-lactams as nonradioactive reagents for the study of PBPs and for the purification of these proteins.
Pharmacokinetic and pharmacodynamic approach for comparing two therapeutic regimens using amikacin
Authors: Staneva M , Markova B , Atanasova I , Terziivanov D
Published: June 2012

The efficiencies of two dosage schedules of amikacin (2 x 10 mg/kg of body weight per 24 h and 1 x 20 mg/kg/24 h intramuscularly for 5 days) against Pseudomonas aeruginosa sepsis in rabbits were compared. Blood samples were drawn at various times after the first application, and amikacin concentrations in serum were assayed microbiologically. The dynamics of the bactericidal effect of amikacin was simulated in vitro with the same strain of P. aeruginosa. No regrowth was found with the 20-mg/kg dose when the bacterial inoculum was in contact with experimental and theoretically predicted serum amikacin concentrations. The killing effect was present even when the drug levels decreased considerably below the MIC. The interrelationship between simulated amikacin concentrations in serum and the corresponding average killing rates was described appropriately by the standard Emax model. The higher amikacin dose performed its bacterial effect faster and the drug persisted longer in the blood. The two amikacin regimens were therapeutically equivalent, but the once-daily schedule had some advantages over the twice-daily drug administration which became evident when both the pharmacokinetic and the pharmacodynamic parameters of the drug were considered.
Cloning and sequence analysis of the gene for a carbapenem-hydrolyzing class A beta-lactamase, Sme-1, from Serratia marcescens S6
Authors: Naas T , Vandel L , Sougakoff W , Livermore D M , Nordmann P
Published: June 2012

Serratia marcescens S6 produces a pI 9.7 carbapenem-hydrolyzing beta-lactamase that is probably encoded by the chromosome (Y. Yang, P. Wu, and D. M. Livermore, Antimicrob. Agents Chemother. 34:755-758, 1990). A total of 11.3 kb of genomic DNA from this strain was cloned into plasmid pACYC184 in Escherichia coli. After further subclonings, the carbapenem-hydrolyzing beta-lactamase gene (blaSme-1) was sequenced (EMBL accession number Z28968). The gene corresponded to an 882-bp open reading frame which encoded a 294-amino-acid polypeptide. This open reading frame was preceded by a -10 and a -35 region consistent with a putative promoter sequence of members of the family Enterobacteriaceae. This promoter was active in E. coli and S. marcescens, as demonstrated by primer extension analysis. N-terminal sequencing showed that the Sme-1 enzyme had a 27-amino-acid leader peptide and enabled calculation of the molecular mass of the mature protein (29.3 kDa). Sequence alignment revealed that Sme-1 is a class A serine beta-lactamase and not a class B metalloenzyme. The earlier view that the enzyme was zinc dependent was discounted. Among class A beta-lactamases, Sme-1 had the greatest amino acid identity (70%) with the pI 6.9 carbapenem-hydrolyzing beta-lactamase, NMC-A, from Enterobacter cloacae NOR-1. Comparison of these two protein sequences suggested a role for specific residues in carbapenem hydrolysis. The relatedness of Sme-1 to other class A beta-lactamases such as the TEM and SHV types was remote. This work details the sequence of the second carbapenem-hydrolyzing class A beta-lactamase from an enterobacterial species and the first in the genus Serratia.
Itraconazole for experimental pulmonary aspergillosis: comparison with amphotericin B, interaction with cyclosporin A, and correlation between therapeutic response and itraconazole concentrations in plasma
Authors: Berenguer J , Ali N M , Allende M C , Lee J , Garrett K , Battaglia S , Piscitelli S C , Rinaldi M G , Pizzo P A , Walsh T J
Published: June 2012

Itraconazole and amphotericin B were compared by using a newly developed model of invasive pulmonary aspergillosis in rabbits immunosuppressed with methylprednisolone and cyclosporin A (CsA). Both itraconazole at 40 mg/kg (given orally) and amphotericin B at 1 mg/kg (given intravenously) had in vivo antifungal activity in comparison with controls. At these dosages, amphotericin B was more effective than itraconazole in reducing the tissue burden (log10 CFU per gram) of Aspergillus fumigatus (P < 0.05) and the number of pulmonary lesions (P < 0.01). However, there was considerable variation in the near-peak concentrations of itraconazole in plasma (median, 4.15 micrograms/ml; range, < 0.5 to 16.8 micrograms/ml) and a strong inverse correlation between concentrations of itraconazole in plasma and the tissue burden of A. fumigatus. An inhibitory sigmoid maximum-effect model predicted a significant pharmacodynamic relationship (r = 0.87, P < 0.001) between itraconazole concentrations in plasma and antifungal activity as a function of the tissue burden of A. fumigatus. This model demonstrated that levels in plasma of greater than 6 micrograms/ml were associated with a significantly greater antifungal effect. Levels in plasma of less than 6 micrograms/ml were associated with a rapid decline in the antifungal effect. Itraconazole, in comparison with amphotericin B, caused a twofold elevation of CsA levels (P < 0.01) but was less nephrotoxic (P < 0.01). This study of experimental pulmonary aspergillosis demonstrated that amphotericin B at 1 mg/kg/day was more active but more nephrotoxic than itraconazole at 40 mg/kg/day, that itraconazole increased concentrations of CsA in plasma, and that the antifungal activity of itraconazole strongly correlated with concentrations in plasma in an inhibitory sigmoid maximum-effect model. These findings further indicate the importance of monitoring concentrations of itraconazole in plasma as a guide to increasing dosage, improving bioavailability, and optimizing antifungal efficacy in the treatment of invasive pulmonary aspergillosis.
Outbreak of vancomycin-, ampicillin-, and aminoglycoside-resistant Enterococcus faecium bacteremia in an adult oncology unit
Authors: Montecalvo M A , Horowitz H , Gedris C , Carbonaro C , Tenover F C , Issah A , Cook P , Wormser G P
Published: June 2012

An outbreak of bacteremia caused by Enterococcus faecium with high-level resistance to vancomycin (MIC of > or = 256 micrograms/ml), ampicillin (MIC of > or = 64 micrograms/ml), and gentamicin or streptomycin (MIC of > or = 2,000 micrograms/ml) occurred in an adult oncology unit from June 1991 to May 1992. Active surveillance for the presence of this organism in stool or perianal cultures was begun in September 1991. Between June 1991 and May 1992, seven patients with bacteremia and 22 noninfected carriers of the organism in stool were identified. The vanA gene, tested for by PCR and gene probe, was present in all isolates evaluated. All bacteremic patients also had resistant E. faecium present in a stool or perianal culture; the stool isolates tested were closely related to the respective blood isolates as determined by pulsed-field gel electrophoresis. Antibiotic regimens using high-dose ampicillin and an aminoglycoside were ineffective with four patients. Five patients (71%) had multiple positive blood cultures; four of these patients died. Following a multiple logistic regression analysis, it was found that bacteremic patients received a significantly greater number of total antibiotic days compared with noninfected stool carriers (P = 0.019). The emergence of E. faecium with high-level resistance to vancomycin, ampicillin, and aminoglycosides underscores the importance of performing susceptibility testing on all clinically significant isolates. In the neutropenic adult oncology patient, bacteremia with this organism is of probable gastrointestinal origin, is often persistent, and is refractory to treatment with ampicillin in combination with an aminoglycoside. Prolonged use of antibiotics may predispose patients with gastrointestinal colonization to develop bacteremia.
In vitro activities of OPC-17116, a new quinolone; ofloxacin; and sparfloxacin against Chlamydia pneumoniae
Authors: Roblin P M , Montalban G , Hammerschlag M R
Published: June 2012

The in vitro susceptibilities of 12 strains of Chlamydia pneumonia to a new quinolone, OPC-17116; ofloxacin; and sparfloxacin were determined. OPC-17116 was slightly less active than sparfloxacin but more active than ofloxacin, with a MIC for 90% of strains tested and a minimal chlamydiacidal concentration for 90% of strains tested of 0.5 micrograms/ml.
Spectrum of activity of soluble intercellular adhesion molecule-1 against rhinovirus reference strains and field isolates
Authors: Ohlin A , Hoover-Litty H , Sanderson G , Paessens A , Johnston S L , Holgate S T , Huguenel E , Greve J M
Published: June 2012

The antiviral potency of soluble intercellular adhesion molecule-1 (ICAM-1; the major receptor for human rhinoviruses) was determined for a subset of American Type Culture Collection reference serotypes and field isolates of rhinovirus. The results indicate that soluble ICAM-1 exhibits a broad spectrum of activity against rhinoviruses and that field isolates have a sensitivity indistinguishable from that of laboratory strains.
Morphological effects of lipopeptides against Aspergillus fumigatus correlate with activities against (1,3)-beta-D-glucan synthase
Authors: Kurtz M B , Heath I B , Marrinan J , Dreikorn S , Onishi J , Douglas C
Published: June 2012

The lipopeptide antifungal agents, echinocandins, papulacandins, and pneumocandins, kill Candida albicans by inhibiting glucan synthesis. For this fungus, there is a good correlation of in vitro enzyme inhibition with in vitro assays of MICs. Semisynthetic lipopeptides such as cilofungin, LY303366, L-693,989, and L-733,560 have activity in vivo against Aspergillus infections but appear to be inactive in broth dilution in vitro tests (MICs, > 128 micrograms/ml). To understand how compounds which lack activity in vitro can have good in vivo activity, we monitored the effect of pneumocandins on the morphology of Aspergillus fumigatus and A, flavus strains by light microscopy and electron microscopy and related the changes in growth to inhibition of glucan synthesis. Pneumocandin B0 caused profound changes in hyphal growth; light micrographs showed abnormally swollen germ tubes, highly branched hyphal tips, and many cells with distended balloon shapes. Aspergillus electron micrographs confirmed that lipopeptides produce changes in cell walls; drug-treated germlings showed very stubby growth with thick walls and a conspicuous dark outer layer which was much thicker in the subapical regions. The rest of the hyphal tip ultrastructure was unaffected by the drug, indicating considerable specificity for the primary target. The drug-induced growth alteration produced very compact clumps in broth dilution wells, making it possible to score the morphological effect macroscopically. The morphological changes could be assayed quantitatively by using conventional broth microdilution susceptibility assay conditions. We defined the endpoint as the lowest concentration required to produce the morphological effect and called it the minimum effective concentration to distinguish it from the no-growth endpoints used in MIC determinations. The minimum effective concentration assay was related to inhibition of glucan synthase activity in vitro and may provide a starting point for development of susceptibility testing methods for lipopeptides.
Mouse-human immunoglobulin G1 chimeric antibodies with activities against Cryptococcus neoformans
Authors: Zebedee S L , Koduri R K , Mukherjee J , Mukherjee S , Lee S , Sauer D F , Scharff M D , Casadevall A
Published: June 2012

Passive antibody administration is a potentially useful approach for the therapy of human Cryptococcus neoformans infections. To evaluate the efficacy of the human immunoglobulin G1 (IgG1) constant region against C. neoformans and to construct murine antibody derivatives with reduced immunogenicities and longer half-lives in humans, two mouse-human IgG1 chimeric antibodies were generated from the protective murine monoclonal antibodies 2D10 (IgM) and 18B7 (IgG1). The 2D10 mouse-human IgG1 chimeric antibody (ch2D10) had significantly lower binding affinity than its parent murine antibody (m2D10), presumably because of a loss of avidity contribution on switching from IgM to IgG. The 18B7 mouse-human IgG1 chimeric antibody (ch18B7) had higher affinity for cryptococcal polysaccharide antigen than its parent murine antibody (m18B7). ch18B7 and ch2D10 promoted phagocytosis of C. neoformans by primary human microglial cells and the murine J774.16 macrophage-like cell line. ch18B7 and m18B7 enhanced fungistatic or fungicidal activity of J774.16 cells and prolonged the survival of lethally infected mice. We conclude that the human IgG1 constant chain can be effective in mediating antifungal activity against C. neoformans. ch18B7 or similar antibodies are potential candidates for passive antibody therapy of human cryptococcosis.
Pharmacokinetics of ceftriaxone during plasma exchange in polyarteritis nodosa patients
Authors: Fauvelle F , Lortholary O , Tod M , Guillevin L , Louchahi M , Léon A , Petitjean O
Published: June 2012

Plasma exchange (PE) is currently being used to treat a variety of disorders involving immune complexes, such as polyarteritis nodosa. This procedure removes endogenous toxic components that accumulate in patients with this disease, but it also removes drugs. Plasma-protein binding and the volume of distribution (V) are two kinetic parameters which strongly affect the efficiency of drug removal by PE. Drugs that are highly bound to plasma proteins and have a low V may show a marked decrease in plasma levels as a result of PE. Because ceftriaxone exhibits saturable plasma-protein binding, which influences its pharmacokinetic parameters, particularly its V, we evaluated its removal during PE therapy in this nonrandomized crossover study. Twelve polyarteritis nodosa patients undergoing PE were studied. Each patient was given ceftriaxone intravenously in doses of 1 and 3 g on days 4 and 11, respectively, immediately before (n = six patients; group I) and 6 h before (n = six patients; group II) PE. Plasma was assayed for ceftriaxone by high-pressure liquid chromatography. The mean amounts eliminated +/- standard deviations were 230.8 +/- 38.5 mg (1 g) and 750.0 +/- 168.5 mg (3 g) for group I and 161.0 +/- 66.0 mg (1 g) and 347.0 +/- 121.0 mg (3 g) for group II. The drug fractions eliminated by PE were 23.0% +/- 3.9% (1-g dose) and 24.9% +/- 5.6% (3-g dose) for group I (P > 0.05), and 16.6% +/- 5.9% (1-g dose) and 11.5% +/- 4.0% (3-g dose) for group II (P < 0.05). These results showed that the drug fraction eliminated decreased when V increased only when the distribution phase of ceftriaxone had been completed (group II). These findings suggest that PE may influence ceftriaxone disposition and that it would be better to administer the drug after PE to assure its therapeutic efficacy.
Phase I trial of valaciclovir, the L-valyl ester of acyclovir, in patients with advanced human immunodeficiency virus disease
Authors: Jacobson M A , Gallant J , Wang L H , Coakley D , Weller S , Gary D , Squires L , Smiley M L , Blum M R , Feinberg J
Published: June 2012

Valaciclovir, the L-valyl ester of acyclovir, is rapidly and extensively converted in humans to acyclovir after oral administration by first-pass metabolism. A phase I study was conducted in two cohorts of volunteers with advanced human immunodeficiency virus (HIV) disease (absolute CD4 lymphocyte count of < 150 cells per microliters) who received oral valaciclovir at dosages of 1,000 or 2,000 mg four times daily for 30 days. All patients were clinically stable without any changes in underlying HIV-related medications for > or = 6 weeks prior to entry in study; these medications were continued throughout the study. Multiple-dose administration of valaciclovir showed a generally favorable safety profile. Nausea, vomiting, diarrhea, and abdominal pain each were reported in < or = 31% of the patients; of these symptoms, only one episode of diarrhea was considered causally related to valaciclovir exposure. Four patients developed neutropenia (two at each dose level) which was not clinically significant. There were no renal or neurologic adverse events. Valaciclovir was rapidly absorbed and converted to acyclovir, with plasma valaciclovir levels generally undetectable or levels of < or = 0.4 microgram/ml. After 3 h postdosing, valaciclovir was not detectable in plasma. Acyclovir was measurable in plasma as early as 15 min following valaciclovir dosing, and plasma concentrations of acyclovir greatly exceeded those of valaciclovir. The mean values for the maximum concentration of drug in plasma, time to maximum concentration of drug in plasma, area under the concentration-time curve from 0 h to infinity, and apparent half-life of acyclovir obtained after single- and multiple-dose valaciclovir administration in HIV-infected patients were similar to those reported in normal healthy volunteers. The time to maximum concentration in serum and half-life of acyclovir after valaciclovir administration were approximately 2 and 3 h, respectively, which were similar to those reported after oral administration of acyclovir itself. The mean trough and peak acyclovir concentrations and the daily area under the concentration-time curve acyclovir values at steady state were 2.5 and 8.4 micrograms/ml and 120 h micrograms/ml, respectively, after a dosage of 2,000 mg of valaciclovir four times daily. These values were approximately fivefold greater than those achieved with high dosages of oral acyclovir (800 mg, five times daily) and were not affected by continued use of medications necessary for management of advanced HIV disease. Thus, 2,000 mg of valaciclovir given orally four times daily should be evaluated for its potential efficacy in suppressing cytomegalovirus and other herpes group virus infections not optimally managed with current oral acyclovir therapy.
Effectiveness of antimicrobial treatment against Borrelia burgdorferi infection in mice
Authors: Moody K D , Adams R L , Barthold S W
Published: June 2012

Although antimicrobial agents are effective therapy for early Lyme disease, optimal treatment schedules have not been conclusively established. The efficacy of various dosages of eight antibiotics used for borreliosis treatment was evaluated for C3H/HeNCrIBR mice, which reproducibly develop persistent infection, arthritis, and carditis when inoculated with Borrelia burgdorferi. Amoxicillin-clavulanic acid, ceftriaxone, and high-dose penicillin G effectively eliminated infection and disease. Oxytetracycline, doxycycline, chloramphenicol, erythromycin, and azithromycin failed to cure infected mice. There was a correlation between peak serum antibiotic concentrations in mice, as determined by agar well diffusion bioassays, and therapeutic levels in humans. When experimentally inoculated mice were treated at 1 week postinfection with ceftriaxone (16 mg/kg of body weight twice daily for 5 days) and monitored for up to 90 days, all treated mice were free of spirochetes and had no gross or histologic lesions. This antibiotic regimen at days 7 to 11 postinoculation eliminated the spirochetes so that there were no relapses during the 90-day observation period. For experimentally inoculated mice treated with ceftriaxone at 7 or 14 days postinfection, arthritis, carditis, and infection were eliminated. When treatment began at 30 and 90 days after inoculation, infection and active cardiac and arthritic lesions were eradicated; however, residual mild synovitis and vasculitis persisted in some mice. In comparison with inoculated, untreated mice, ceftriaxone therapy at 7, 14, 30, and 90 days postinfection abrogated the development of antibody titers against B. burgdorferi. Having the potential to determine the presence of the spirochete through culture and histologic lesions makes the B. burgdorferi-inoculated C3H mouse model a valuable adjunct in evaluating chemotherapeutic options for Lyme disease.
Differential antiviral activities and intracellular metabolism of 3'-azido-3'-deoxythymidine and 2',3'-dideoxyinosine in human cells
Authors: Mukherji E , Au J L , Mathes L E
Published: June 2012

Dideoxynucleosides such as 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxyinosine (ddI) can effectively inhibit the replication of human immunodeficiency virus (HIV) in T lymphoid cells. There is evidence that HIV can infect and replicate in other cells including monocytoid cells and macrophages. The present study compared the antiretroviral activities of ddI and AZT in three lineages of human cells, i.e., MOLT4 (T lymphocytoid, CD4+), U937 (monocytoid, CD4+), and HT1080 (fibroblastoid, CD4-) cells. Feline leukemia virus, a retrovirus that causes immunodeficiency in cats, was used to infect the cells. The drug concentrations needed to reduce the viral p27 antigen titers in cell lysates by 50% (IC50s) were determined. The data show that AZT and ddI inhibited viral replication in all three cell lines. The IC50s of AZT were 0.02, 1.75, and 2.31 microM in MOLT4, HT1080, and U937 cells, respectively. For ddI, the IC50s were 4.31, 9.52, and 43.5 microM, respectively. These data indicate differential antiviral activities of ddI and AZT in the different cells with the following rank order of drug sensitivity: MOLT4 > HT1080 > U937. A study of the intracellular metabolism of [3H]AZT and [3H]ddI shows that the antiretroviral activities of AZT and ddI in the three cell lines correlated with the levels of their intracellular triphosphate metabolites.
Use of the chromosomal class A beta-lactamase of Mycobacterium fortuitum D316 to study potentially poor substrates and inhibitory beta-lactam compounds
Authors: Galleni M , Franceschini N , Quinting B , Fattorini L , Orefici G , Oratore A , Frère J M , Amicosante G
Published: June 2012

Sixteen different compounds usually considered beta-lactamase stable or representing potential beta-lactam inhibitors and inactivators were tested against the beta-lactamase produced by Mycobacterium fortuitum. The compounds exhibiting the most interesting properties were BRL42715, which was by far the best inactivator, and CGP31608 and ceftazidime, which were not recognized by the enzyme. These compounds thus exhibited adequate properties for fighting mycobacterial infections. Although cloxacillin, dicloxacillin, cefoxitin, and CP65207-2 exhibited poor inhibitory efficiency against the enzyme, they were also rather poor substrates and might be considered potential antimycobacterial agents. By contrast, CGP31523A and ceftamet were good substrates.
Decreased counts of blood neutrophils, monocytes, and platelets in human immunodeficiency virus-infected children and young adults treated with diethyldithiocarbamate
Authors: Shenep J L , Hughes W T , Flynn P M , Roberson P K , Behm F G , Fullen G H , Kovnar S G , Guito K P , Brodkey T O
Published: June 2012

Nineteen young human immunodeficiency virus-infected patients were randomized to receive 400 mg of oral diethyldithiocarbamate (DTC) per m2 or placebo weekly for 12 weeks. Changes in blood CD4+ lymphocytes were not significantly different between groups. However, neutrophil, monocyte, and platelet counts consistently decreased during DTC treatment, suggesting DTC-mediated myelosuppression.
Clinical trial of fusidic acid for lepromatous leprosy
Authors: Franzblau S G , Chan G P , Garcia-Ignacio B G , Chavez V E , Livelo J B , Jimenez C L , Parrilla M L , Calvo R F , Williams D L , Gillis T P
Published: June 2012

Fusidic acid was assessed for antileprosy activity in nine lepromatous leprosy patients. Patients received fusidic acid at either 500 mg/day for 12 weeks or 750 mg/day for 4 weeks followed by 500 mg/day for 8 weeks. All patients showed time-dependent clinical improvement and decreases in bacillary morphological index, radiorespirometric activity and PCR signal, and in serum phenolic glycolipid I. Fusidic acid appears to be a weakly bactericidal antileprosy agent which may have a role in the multidrug treatment of leprosy pending an evaluation of lepra-reaction-suppressive activity.