bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro selective antibiotic concentrations of beta-lactams for penicillin-resistant Streptococcus pneumoniae populations
Authors: Negri M C , Morosini M I , Loza E , Baquero F
Published: June 2012

Therapeutic regimens containing beta-lactam antibiotics are selecting penicillin-resistant Streptococcus pneumoniae populations all over the world. The selective pressure after 4 h of exposure to different concentrations of amoxicillin, cefixime, cefuroxime, and cefotaxime for low-level or high-level penicillin-resistant S. pneumoniae was evaluated in an in vitro model with mixed populations with penicillin susceptibilities of 0.015, 0.5, 1, and 2 micrograms/ml. The antibiotic concentration selecting for low-level resistance strongly reduced the susceptible population. Increasing antibiotic concentrations tended to decrease the total proportion of penicillin-resistant bacteria because of reduced numbers of the low-level-resistant population. The antibiotic concentration selecting for high-level resistance produced fewer resistant populations, but most of the organisms selected represented high-level resistance. In general, amoxicillin was a good selector for the low-level-resistant population and a poor selector for high-level resistance; cefuroxime and cefotaxime were poor selectors for low-level resistance and better selectors than amoxicillin for high-level penicillin resistance. Cefixime was the best selector of low-level penicillin resistance. When only resistant populations were mixed, the strains with high-level resistance were selected even at low antibiotic concentrations. Determination of the effects of selective antibiotic concentrations on mixed cultures of bacteria expressing different antibiotic resistance levels may help researchers to understand the ecology and epidemiology of penicillin-resistant S. pneumoniae populations.
Placement of alkyl substituents on the C-7 piperazine ring of fluoroquinolones: dramatic differential effects on mammalian topoisomerase II and DNA gyrase
Authors: Gootz T D , McGuirk P R , Moynihan M S , Haskell S L
Published: June 2012

Several substituted analogs of 7-(cis-3,5-dimethylpiperazinyl)-6,8-difluoro-5-amino-1-cyclopropyl quinolone were prepared and tested in a DNA cleavage assay with calf thymus topoisomerase II. Positioning of the methyl groups on the C-7 piperazine ring influenced potency against the mammalian enzyme; the cis-3,5-dimethyl configuration did not stimulate cleavage at drug concentrations less than or equal to 2,000 microM, while the trans configuration was active at drug levels as low as 36 microM. Removal of the cis-methyl groups produced a compound that was only sixfold less potent than the antitumor agent etoposide in stimulating enzyme-mediated DNA cleavage. The cis- and trans-methyl substitutions on the piperazine that conferred potency against the mammalian type II enzyme had little effect on bacterial DNA gyrase cleavage activity, suggesting that an asymmetric barrier exists with the mammalian enzyme which influences productive quinolone interaction, favoring the less bulky trans-3,5-dimethylpiperazine substituent at C-7.
Treatment of Klebsiella pneumoniae septicemia in normal and leukopenic mice by liposome-encapsulated muramyl tripeptide phosphatidylethanolamide
Authors: Melissen P M , van Vianen W , Bakker-Woudenberg I A
Published: June 2012

The effect of free muramyl tripeptide phosphatidylethanolamide (MTPPE) and liposome-encapsulated MTPPE (LE-MTPPE) on Klebsiella pneumoniae septicemia resulting from intraperitoneal bacterial inoculation was investigated in mice. When administering a single prophylactic dose at 24 h before bacterial inoculation, the percentage survival was 55% (MTPPE) or 40% (LE-MTPPE), whereas untreated control mice died. Only repeated prophylactic treatment with LE-MTPPE could further increase survival up to 85%.
Effect of foscarnet induction treatment on quantitation of human cytomegalovirus (HCMV) DNA in peripheral blood polymorphonuclear leukocytes and aqueous humor of AIDS patients with HCMV retinitis. The Italian Foscarnet Study Group
Authors: Gerna G , Baldanti F , Sarasini A , Furione M , Percivalle E , Revello M G , Zipeto D , Zella D
Published: June 2012

The aim of this study was to investigate peripheral blood polymorphonuclear leukocytes and, whenever possible, aqueous humor from 65 AIDS patients with ophthalmoscopically diagnosed human cytomegalovirus (HCMV) retinitis to determine (i) whether patients consistently carry viral DNA and (ii) to what extent foscarnet induction treatment decreases viral DNA levels. HCMV DNA was quantified by PCR using densitometric analysis of hybridization products obtained from external standards and a standard curve from which the number of genome equivalents of test samples, normalized by using an internal amplification control, was interpolated. Results showed that 56 of 65 patients (86.1%) were positive for HCMV DNA prior to induction treatment. Of 41 of the 56 patients (73.2%) whose blood had become DNA negative after induction, only 5 had a high viral load (> 5,000 genome equivalents per 2 x 10(5) polymorphonuclear leukocytes) prior to induction, whereas as many as 13 of the 15 (26.8%) patients remaining DNA positive after induction had a high viral load prior to induction. Finally, of the nine patients (13.8%) with DNA-negative blood prior to induction treatment, three were shifted to foscarnet from ganciclovir, while six were erroneously enrolled in the study. Pre- and postinduction aqueous humor samples were obtained from 12 patients; all of these were DNA positive prior to induction, whereas after induction, 4 became negative, 6 showed a marked decrease in viral DNA, and 2 had nearly stable low DNA levels. In conclusion, PCR is a valuable tool for etiologic diagnosis and monitoring of HCMV retinitis treatment in AIDS patients. HCMV DNA is consistently present in the blood and aqueous humor of all patients with HCMV retinitis. Foscarnet induction treatment is highly effective in suppressing or reducing DNA levels in both blood leukocytes and aqueous humor.
Molecular characterization of an enterobacterial metallo beta-lactamase found in a clinical isolate of Serratia marcescens that shows imipenem resistance
Authors: Osano E , Arakawa Y , Wacharotayankun R , Ohta M , Horii T , Ito H , Yoshimura F , Kato N
Published: June 2012

A clinical isolate of Serratia marcescens (TN9106) produced a metallo beta-lactamase (IMP-1) which conferred resistance to imipenem and broad-spectrum beta-lactams. The blaIMP gene providing imipenem resistance was cloned and expressed in Escherichia coli HB101. The IMP-1 was purified from E. coli HB101 that harbors pSMBNU24 carrying blaIMP, and its apparent molecular mass was calculated to be about 30 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Kinetic studies of IMP-1 against various beta-lactams revealed that this enzyme hydrolyzes not only various broad-spectrum beta-lactams but also carbapenems. However, aztreonam was relatively stable against IMP-1. Although clavulanate or cloxacillin failed to inhibit IMP-1, Hg2+, Fe2+, or Cu2+ blocked the enzyme's activity. Moreover, the presence of EDTA in the reaction buffer resulted in a decrease in the enzyme's activity. Carbapenem resistance was not transferred from S. marcescens TN9106 to E. coli CSH2 by conjugation. A hybridization study confirmed that blaIMP was encoded on the chromosome of S. marcescens TN9106. By nucleotide sequencing analysis, blaIMP was found to encode a protein of 246 amino acid residues and was shown to have considerable homology to the metallo beta-lactamase genes of Bacillus cereus, Bacteroides fragilis, and Aeromonas hydrophila. The G+C content of blaIMP was 39.4%. Four consensus amino acid residues, His-95, His-97, Cys-176, and His-215, which form putative zinc ligands, were conserved in the deduced amino acid sequence of IMP-1. By determination of the amino acid sequence at the N terminus of purified mature IMP-1, 18 amino acid residues were found to be processed from the N terminus of the premature enzyme as a signal peptide. These results clearly show that IMP-1 is an enterobacterial metallo beta-lactamase, of which the primary structure has been completely determined, that confers resistance to carbapenems and other broad-spectrum beta-lactams.
In vitro antiplasmodial, antiamoebic, and cytotoxic activities of a series of bisbenzylisoquinoline alkaloids
Authors: Marshall S J , Russell P F , Wright C W , Anderson M M , Phillipson J D , Kirby G C , Warhurst D C , Schiff P L
Published: June 2012

Twenty-four bisbenzylisoquinoline alkaloids were screened for antiplasmoidal, antiamoebic, and cytotoxic activities by use of in vitro microtests. Eight of the alkaloids had antiplasmodial activity, with a 50% inhibitory concentration (IC50) of less than 1 microM against a multidrug-resistant strain of Plasmodium falciparum (chloroquine had an IC50 of 0.2 microM). The three alkaloids most active against Entamoeba histolytica, aromoline, isotrilobine, and insularine, had IC50s of 5 to 11.1 microM (metronidazole had an IC50 of 1.87 microM). None of the 24 bisbenzylisoquinoline alkaloids exhibited significant cytotoxicity against the KB cell line, the most toxic being berbamine, with an IC50 of 17.8 microM (the IC50 of podophyllotoxin was 0.008 microM). Bisbenzylisoquinoline alkaloids merit further investigation as potential novel antimalarial agents.
Improvement of outer membrane-permeabilizing and lipopolysaccharide-binding activities of an antimicrobial cationic peptide by C-terminal modification
Authors: Piers K L , Brown M H , Hancock R E
Published: June 2012

Antimicrobial cationic peptides have been discovered in many different organisms and often possess a broad range of activity. In this study, we investigated the mechanisms of actions of melittin and two synthetic peptides, CEME (a cecropin-melittin hybrid) and CEMA, against gram-negative bacteria. CEMA was produced by recombinant DNA procedures and is an analog of CEME with a modified C terminus resulting in two additional positive charges. All three peptides showed good antimicrobial activity against four different gram-negative bacteria, but only CEMA was able to somewhat augment the activity of some conventional antibiotics in synergy studies. Studies using the bacteria Pseudomonas aeruginosa and Enterobacter cloacae showed that the peptides all possessed the ability to permeabilize bacterial outer membranes to the hydrophobic fluorophor 1-N-phenylnaphthylamine and the protein lysozyme, with CEMA being the most active. CEMA also had the strongest relative binding affinity for bacterial endotoxin (lipopolysaccharide). These data collectively indicated that these peptides all cross the outer membrane by the self-promoted uptake pathway and that CEMA is the peptide most effective at accessing this pathway.
Presence of the Listeria tetracycline resistance gene tet(S) in Enterococcus faecalis
Authors: Charpentier E , Gerbaud G , Courvalin P
Published: June 2012

Two hundred thirty-eight tetracycline- and minocycline-resistant clinical isolates of Enterococcus and Streptococcus spp. were investigated by dot blot hybridization for the presence of nucleotide sequences related to tet(S) (first detected in Listeria monocytogenes BM4210), tet(K), tet(L), tet(M), tet(O), tet(P), and tet(Q) genes. The tet(S) determinant was found in 22 strains of Enterococcus faecalis, associated with tet(M) in 9 of these isolates and further associated with tet(L) in 3 of these strains. tet(M) was detected in all strains of Streptococcus spp. and in all but 10 isolates of Enterococcus spp.; tet(L) was found in 93 enterococci and tet(O) was found in single isolates of E. faecalis and Streptococcus milleri. No hybridization with the tet(K), tet(P), and tet(Q) probes was observed. Transfer of tet(S) by conjugation to E. faecalis or to E. faecalis and L. monocytogenes was obtained from 8 of the 10 E. faecalis strains harboring only this tet gene. Hybridization experiments with DNAs of four donors and of the corresponding transconjugants suggested that tet(S) was located in the chromosome. These results indicate that the genetic support of tet(S) in E. faecalis is different from that in L. monocytogenes, where it is carried by self-transferable plasmids, and confirm the notion of exchange of genetic information between Enterococcus and Listeria spp. in nature.
Effect of lactation on single-dose pharmacokinetics of norfloxacin nicotinate in ewes
Authors: Soback S , Gips M , Bialer M , Bor A
Published: June 2012

In a three-way crossover trial, six healthy Finnish-Merino-Awassi ewes were given a single intravenous injection of norfloxacin nicotinate (in a dose equivalent to 25 mg of norfloxacin base per kg of body weight) during nursing, 1 day after weaning, and 1 month after weaning. Blood and milk samples were collected at different time intervals following dosing, and norfloxacin concentrations were determined by a high-performance liquid chromatography assay. The serum drug concentration versus time data were analyzed by a noncompartmental approach which was based on the statistical-moment theory. The total body clearance values were 4.2 +/- 1.3 (injection during nursing), 1.6 +/- 0.3 (injection 1 day after weaning), and 3.1 +/- 0.8 ml/min/kg (injection 1 month after weaning). The mean residence times were 335 +/- 83, 797 +/- 129, and 481 +/- 102 min and terminal half-lives were 266 +/- 51, 603 +/- 94, and 372 +/- 68 min for the respective treatments. The estimated volumes of distribution at steady state were 1.3 +/- 0.1, 1.2 +/- 0.1, and 1.4 +/- 0.2 liter/kg for the respective treatments. Milk norfloxacin concentrations were up to 40 times higher than the corresponding concentrations in serum during lactation. Accordingly, in ewes with 1.5 liter of milk in the udder more than half of the drug in the animal appeared to be in the milk. Therapeutic concentrations of norfloxacin could be detected in the sera of suckling lambs, implicating that fluoroquinolone therapy should be discouraged during breast feeding. In lactating ewes and in ewes with full udders, moment analysis calculations did not show a significant difference between the system moment mean residence time and the system matrix mean residence time values. Thus, the pharmacokinetics of norfloxacin in the three groups could be described by the classical two-compartment open-body model with input and output occurring from the central compartment. The results did not support the existence of a distinguishable milk compartment. Milk secretion seemed to act as one of the clearance processes of the drug when milk was continuously removed.
In vitro activities of 12 orally administered antimicrobial agents against four species of bacterial respiratory pathogens from U.S. Medical Centers in 1992 and 1993
Authors: Barry A L , Pfaller M A , Fuchs P C , Packer R R
Published: June 2012

Clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes, and Moraxella catarrhalis were gathered from 19 different clinical laboratories throughout the continental United States. The in vitro activities of 12 orally administered antimicrobial agents were compared by broth microdilution tests with 3,151 bacterial isolates. Among 890 H. influenzae isolates, 30% were capable of producing beta-lactamase enzymes (12 to 41% in different medical centers). Most of the 619 beta-lactamase-negative H. influenzae strains were susceptible to ampicillicin (MIC, < or = 1.0 micrograms/ml): 5 strains were intermediate in susceptibility (MIC, 2.0 micrograms/ml) and 1 strain was ampilicillin resistant (MIC, 4.0 micrograms/ml). Ninety-two percent of 698 M. catarrhalis strains were beta-lactamase positive. Of 799 S. pneumoniae isolates, 15% were intermediate in susceptibility to penicillin and 7% were resistant to penicillin. The prevalence of penicillin-susceptible pneumococci in different institutions ranged from 63 to 95%. Only 1% of 764 S. pyogenes isolates were resistant to the macrolides, but 5% of S. pneumoniae isolates were macrolide resistant. Only 71% of 58 penicillin-resistant S. pneumoniae isolates were erythromycin susceptible, whereas 97% of the 622 penicillin-susceptible strains were erythromycin susceptible. Penicillin-resistant pneumococci were also relatively resistant to the cephalosporins and amoxicillin. Penicillin-susceptible pneumococci were susceptible to amoxicillin-clavulanic acid (MIC for 90% of isolates tested [MIC90], < or = 0.12/0.06 microgram/ml), cefixime (MIC90, 0.25 microgram/ml), cefuroxime axetil (MIC90, < or = 0.5 microgram/ml), cefprozil (MIC90, < or = 0.5 micrograms/ml), cefaclor (MIC90, 0.5 microgram/ml), and loracarbef (MIC90, 1.0 microgram/ml). Most strains of the other species remained susceptible to the study drugs other than amoxicillin.
Intracellular penetration and activity of BAY Y 3118 in human polymorphonuclear leukocytes
Authors: García I , Pascual A , Perea E J
Published: June 2012

The penetration of a new quinolone (BAY Y 3118) into human polymorphonuclear leukocytes (PMNs) was evaluated by a fluorometric assay. The cellular concentration-to-extracellular concentration (C/E) ratio was higher than 6.3 at extracellular concentrations ranging from 2 to 100 mg/liter. The uptake of BAY Y 3118 was rapid, reversible and nonsaturable. The intracellular penetration of BAY Y 3118 was significantly affected by environmental temperature (C/E ratio at 4 degrees C, 5.4 +/- 0.5; control, 7.5 +/- 0.9; P < 0.05) and cell viability (C/E ratio in dead PMNs, 5.5 +/- 0.8; control 7.5 +/- 0.9; P < 0.05), but it was not affected by metabolic inhibitors. The ingestion of opsonized zymosan or opsonized Staphylococcus aureus significantly decreased the levels of PMN-associated BAY Y 3118. Cell stimulation by a membrane activator, however, significantly increased the intracellular concentration of this quinolone. At therapeutic extracellular concentrations (0.5, 2, and 5 mg/liter), BAY Y 3118 showed intracellular activity greater than that of ciprofloxacin against S. aureus in human PMNs. It was concluded that BAY Y 3118 reaches high intracellular concentrations within human PMNs and remains active intracellularly.
gyrA mutations in quinolone-resistant isolates of the fish pathogen Aeromonas salmonicida
Authors: Oppegaard H , Sørum H
Published: June 2012

gyrA mutations in quinolone-resistant isolates of Aeromonas salmonicida have been detected by using PCR to amplify the quinolone resistance-determining region of gyrA and subsequent cloning and sequencing of PCR products. Comparison of nucleotide and derived amino acid sequences of PCR products from quinolone-susceptible and -resistant bacteria revealed a serine 83-to-isoleucine substitution in the gyrase A protein of resistant isolates. One of the resistant isolates differed from the other by a two- to fourfold-higher MIC of the fluoroquinolone enrofloxacin and carried an additional alanine 67-to-glycine substitution, which may contribute to the higher level of resistance.
In vitro activities of enoxacin, enrofloxacin, sparfloxacin, and ciprofloxacin against Escherichia coli strains isolated from diarrheic lambs and kids
Authors: Cid D , Piriz S , Ruiz-Santa-Quiteria J A , Valle J , Garcia S , Vadillo S , de la Fuente R
Published: June 2012

The in vitro activities of four fluoroquinolone compounds were tested against 92 Escherichia coli strains of ovine and caprine origin under aerobic and anaerobic incubation conditions. The four fluoroquinolones proved to be highly effective against the E. coli isolates tested. When bacteria were cultured anaerobically, at least fourfold increases in the MICs of enoxacin for the strains occurred and no detectable changes in enrofloxacin, sparfloxacin, and ciprofloxacin MICs occurred.
Efficacies of different vancomycin dosing regimens against Staphylococcus aureus determined with a dynamic in vitro model
Authors: Duffull S B , Begg E J , Chambers S T , Barclay M L
Published: June 2012

A dynamic in vitro model was used to assess four different vancomycin dosing regimens against Staphylococcus aureus. These regimens achieved peak drug concentrations of 48 micrograms/ml (single dose) and 30 micrograms/ml (dosed every 12 h) and constant concentrations of 16 and 8 micrograms/ml. Analysis of the area under the bacterial concentration-time curve, area under the first moment of the bacterial concentration-time curve, and bacterial elimination rate constant showed no difference in the rate or extent of bacterial killing. The optimal dosing method may be that which achieves the lowest area under the curve while concentrations are maintained above the MBC.
Azole resistance in oropharyngeal Candida albicans strains isolated from patients infected with human immunodeficiency virus
Authors: He X , Tiballi R N , Zarins L T , Bradley S F , Sangeorzan J A , Kauffman C A
Published: June 2012

For 212 oropharyngeal isolates of Candida albicans, the fluconazole MICs for 50 and 90% of strains tested were 0.5 and 16 micrograms/ml, respectively, and those of itraconazole were 0.05 and 0.2 micrograms/ml, respectively. Of 16 isolates for which fluconazole MICs were > 64 micrograms/ml, itraconazole MICs for 14 were < or = 0.8 micrograms/ml and for 2 were > 6.4 micrograms/ml. Most fluconazole-resistant strains remained susceptible to itraconazole; whether itraconazole will prove effective for refractory thrush remains to be shown.
Antimicrobial susceptibilities of clinical isolates of Acinetobacter baumannii from Singapore
Authors: Kuah B G , Kumarasinghe G , Doran J , Chang H R
Published: June 2012

The in vitro activities of 17 antimicrobial agents alone or in combination against 70 clinical isolates of Acinetobacter baumannii from Singapore were determined by broth microdilution. The MICs of amoxicillin, ampicillin, ceftazidime, ceftriaxone, gentamicin, and piperacillin for 90% of the strains were > or = 128 micrograms/ml. Addition of sulbactam to ampicillin produced improved activity, whereas adding tazobactam to piperacillin did not. The MICs of amikacin, ciprofloxacin, and imipenem for 90% of the strains were 32, 32, and 16 micrograms/ml, respectively.
Effectiveness of various antimicrobial agents against Mycobacterium avium complex in the beige mouse model
Authors: Ji B , Lounis N , Truffot-Pernot C , Grosset J
Published: June 2012

The results of five chemotherapeutic experiments in beige mice infected with organisms of the Mycobacterium avium complex are presented. After monotherapy with various antimicrobial agents for 4 weeks, only clarithromycin, amikacin, and ethambutol displayed definite bactericidal effects; sparfloxacin and clofazimine showed modest bacteriostatic effects; and rifampin and rifabutin were totally inactive against the isolate tested. After treatment for 4 weeks, the large quantities of clofazimine that had accumulated in the organs of mice seriously interfered with the enumeration of the CFU and assessment of the efficacy of the treatment. The in vitro synergistic effects of drug combinations against M. avium complex were not confirmed in beige mice. In combination with clarithromycin, amikacin could prevent the selection of clarithromycin-resistant mutants, whereas minocycline could not.
Altered production of penicillin-binding protein 2a can affect phenotypic expression of methicillin resistance in Staphylococcus aureus
Authors: Hackbarth C J , Miick C , Chambers H F
Published: June 2012

Altered production of penicillin-binding protein 2a (PBP 2a) may affect the phenotypic expression of resistance in methicillin-resistant Staphylococcus aureus (MRSA). COL, an MRSA strain that constitutively produces PBP 2a, was transformed with a recombinant plasmid containing the two beta-lactamase regulatory genes, blaI and blaR1, with either the beta-lactamase gene, blaZ, or a truncated blaZ. Both of the transformed MRSA strains now produced an inducible PBP 2a, and the MICs of nafcillin, methicillin, and imipenem for these strains were similar to those for the parental strain. A mutation in blaR1 that resulted in the complete repression of PBP 2a production altered the phenotypic expression of methicillin resistance in that strain, as evidenced by efficiency-of-plating experiments. Rather than being homogeneously resistant like COL, the blaR1 mutant strain now appeared to have a small resistant subpopulation. Gene products that regulate PBP 2a production may contribute to the organism's expression of methicillin resistance, but additional chromosomally located factors are required.
Guanylhydrazones in therapy of Pneumocystis carinii pneumonia in immunosuppressed rats
Authors: Walzer P D , Foy J , Runck J , Steele P , White M , Klein R S , Otter B A , Sundberg R J
Published: June 2012

Guanylhydrazones are cationic heteroaromatic drugs similar to the diamidines which are effective in the treatment of African trypanosomiasis and pneumocystosis. On the basis of their antitrypanosomal activity, different guanylhydrazones were selected for evaluation in a rat model of Pneumocystis carinii pneumonia. The most active compounds were the 2-(4'-formylphenyl)-1-methylimidazo-[1,2-a] pyridinium guanylhydrazones which, at a dose of 2 mg/kg/day, were about as effective as trimethoprim-sulfamethoxazole at a dose of 50 mg of trimethoprim per kg/day plus 250 mg of sulfamethoxazole per kg/day. The anti-P. carinii activity of these guanylhydrazone derivatives was found with parenteral but not with oral administration. The 1,3-arylene diketone bis(guanylhydrazones) were generally ineffective, although a triacetyl derivative showed some anti-P. carinii activity. Nitroimidazole guanylhydrazone derivatives were also ineffective. Attempts to improve the therapeutic efficacy of the different guanylhydrazones were limited by problems of toxicity. We conclude that some guanylhydrazone derivatives are potent anti-P. carinii drugs and that further studies should be pursued to develop safer compounds and investigate structure-activity relationships.
Postantibiotic effect of meropenem on members of the family Enterobacteriaceae determined by five methods
Authors: MacKenzie F M , Gould I M , Chapman D G , Jason D
Published: June 2012

The postantibiotic effect (PAE) of meropenem was determined for 11 strains, both clinical isolates and reference strains of members of the family Enterobacteriaceae. The study compares PAE results obtained by five methods used to monitor bacterial regrowth, including viable counting, alone and in combination with impedance; bioluminescence, alone and in combination with impedance; and a morphological technique. After exposure of the test organisms to meropenem (0.1 x to 100 x MIC) for 2 h, concentration-dependent differences in counts by bioluminescence and viable counts were observed, the latter always being lower. The differences varied with the test organism. For example, after exposure of Providentia stuartii NCTC 10318 to 0.1 x MIC, the counts were 5.5 x 10(5) and 2.0 x 10(5) whereas after exposure of Citrobacter freundii MR76 to 0.1 x MIC of meropenem the counts were 2.3 x 10(6) and 6.8 x 10(3) by bioluminescence and viable counting, respectively. The discrepancies were probably due to the relative inability of the viable counting procedure to detect fragile aberrant morphologies and resulted in differences in the calculated PAE values. With methods which do not detect fragile morphologies, the PAE may be underestimated. A general trend was observed for the order of magnitude of the PAEs by the following methods (in order of decreasing magnitude of PAE): (i) morphological technique, (ii) bioluminescence technique alone, (iii) bioluminescence in combination with impedance, (iv) viable counting in combination with impedance, and (v) viable counting alone. It is our opinion that of the methods examined in this study, bioluminescence in combination with impedance best reflects the true values for PAEs, and these results were examined more closely.
Activity of WY-49605 compared with those of amoxicillin, amoxicillin-clavulanate, imipenem, ciprofloxacin, cefaclor, cefpodoxime, cefuroxime, clindamycin, and metronidazole against 384 anaerobic bacteria
Authors: Spangler S K , Jacobs M R , Appelbaum P C
Published: June 2012

The National Committee for Clinical Laboratory Standards agar dilution method was used to compare the in vitro activity of WY-49605 (also called SUN/SY 5555 and ALP-201), a new broad-spectrum oral penem, to those of amoxicillin, amoxicillin-clavulanate, imipenem, ciprofloxacin, cefaclor, cefpodoxime, cefuroxime, clindamycin, and metronidazole against 384 clinically isolated anaerobes. These anaerobic organisms included 90 strains from the Bacteroides fragilis group, 87 Prevotella and Porphyromonas strains, non-B. fragilis group Bacteroides strains, 56 fusobacteria, 55 peptostreptococci, 49 gram-positive non-spore-forming rods, and 47 clostridia. Overall, WY-49605 had an MIC range of 0.015 to 8.0 micrograms/ml, an MIC at which 50% of the isolates are inhibited (MIC50) of 0.25 microgram/ml, and an MIC at which 90% of the isolates are inhibited (MIC90) of 2.0 micrograms/ml. Good activity against all anaerobe groups was observed, except for Clostridium difficile and lactobacilli (MIC50s of 4.0 and 2.0 micrograms/ml, respectively, and MIC90s of 8.0 and 2.0 micrograms/ml, respectively). Imipenem had an MIC50 of 0.03 microgram/ml and an MIC90 of 0.25 microgram/ml. Ciprofloxacin was much less active (MIC50 of 2.0 micrograms/ml and MIC90 of 16.0 micrograms/ml). By comparison, all oral beta-lactams were less active than WY-49605, with susceptibilities as follows: amoxicillin MIC50 of 8.0 micrograms/ml and MIC90 of > 256.0 micrograms/ml), amoxicillin-clavulanate MIC50 of 1.0 microgram/ml and MIC90 of 8.0 micrograms/ml, cefaclor MIC50 of 8.0 micrograms/ml and MIC90 of > 32.0 micrograms/ml, cefpodoxime MIC50 of 4.0 micrograms/ml and MIC90 of > 32.0 micrograms/ml, and cefuroxime MIC50 of 4.0 micrograms/ml and MIC90 of > 32.0 micrograms/ml. Clindamycin was active against all groups except some members of the B. fragilis group, Fusobacterium varium, and some clostridia ( overall MIC50 of 0.5 micrograms/ml and overall MIC90 of 8.0 micrograms/ml). Metronidazole was active (MIC of less than or equal to 4.0 micrograms/ml) against all gram-negative anaerobic rods, but most gram-positive non-spore-forming rods, some peptostreptococci, and some clostridia were less susceptible. To date, WY-49605 is the most active oral beta-lactam against anaerobes: these results suggest clinical evaluation for clinical indications suitable for oral therapy.
Effects of naftifine and terbinafine, two allylamine antifungal drugs, on selected functions of human polymorphonuclear leukocytes
Authors: Vago T , Baldi G , Colombo D , Barbareschi M , Norbiato G , Dallegri F , Bevilacqua M
Published: June 2012

Many antimycotic agents negatively affect the natural immune response. Typically, these drugs impair polymorphonuclear leukocyte (PMN) production of superoxide anion, chemotaxis, or the killing of pathogens. Allylamines are a new class of antimycotic compounds with a new mechanism of antifungal action, i.e., inhibition of the fungal squalene epoxidase. The trial that we describe aimed to evaluate the effects of two allylamines, terbinafine and naftifine, on selected functions of PMNs, i.e., superoxide anion production, chemotaxis, and killing of Candida albicans blastospores. Terbinafine and naftifine on their own did not affect superoxide anion production when they were added to PMNs. When PMNs were preincubated with allylamines and were then stimulated by N-formyl-Met-Leu-Phe or phorbol 12-myristate 13-acetate, superoxide anion production was increased (priming effect). Since intracellular free calcium (Ca2+i) is involved in the control of superoxide anion production, we evaluated the effects of the allylamines on the Ca2+i concentration ([Ca2+]i). In the presence of terbinafine or naftifine, the [Ca2+]i increased in a dose-dependent manner; the source of Ca2+i was not extracellular since it was not affected by extracellular calcium chelation with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In the presence of terbinafine or naftifine, chemotaxis of PMNs was not impaired. Terbinafine and naftifine slightly but significantly increased the killing of C. albicans blastospores (P < 0.05 at 10 and 100 microM). In conclusion, in contrast to imidazole-like drugs, the allylamine antimycotic compounds terbinafine and naftifine enhance selected functions of PMNs.
Comparison of inhibition of Escherichia coli topoisomerase IV by quinolones with DNA gyrase inhibition
Authors: Hoshino K , Kitamura A , Morrissey I , Sato K , Kato J , Ikeda H
Published: June 2012

In order to examine the inhibitory activities of quinolones against topoisomerase IV, both subunits of this enzyme, ParC and ParE, were purified from Escherichia coli. The specific activity of topoisomerase IV decatenation was found to be more than five times greater than that of topoisomerase IV relaxation. Thus, the decatenation activity of topoisomerase IV seems the most relevant activity for use in studies of drug inhibition of this enzyme. Although topoisomerase IV was less sensitive to quinolones than DNA gyrase, the 50% inhibitory concentrations for decatenation were significantly lower than those for type I topoisomerases. Moreover, there was a positive correlation between the inhibitory activity against topoisomerase IV decatenation and that for DNA gyrase supercoiling. These results imply that topoisomerase IV could be a target for the quinolones in intact bacteria and that quinolones could inhibit not only supercoiling of DNA gyrase but also decatenation of topoisomerase IV when high concentrations of drug exist in bacterial cells.
Susceptibilities of Mycoplasma hominis, Mycoplasma pneumoniae, and Ureaplasma urealyticum to new glycylcyclines in comparison with those to older tetracyclines
Authors: Kenny G E , Cartwright F D
Published: June 2012

The glycylcyclines are new tetracycline derivatives that include the N,N-dimethylglycylamido derivative of minocycline (DMG-MINO) and the N,N-dimethylglycylamido derivative of 6-demethyl-6-deoxytetracycline (DMG-DMDOT). The susceptibilities of Mycoplasma pneumoniae, Mycoplasma hominis, and Ureaplasma urealyticum to DMG-MINO, DMG-DMDOT, tetracycline, doxycycline, and minocycline were determined by the agar dilution method. The glycylcyclines with MICs at which 50% of the isolates are inhibited of 0.25 to 0.5 micrograms/ml for M. pneumoniae were two- to fourfold more active than tetracycline and had the same activity as minocycline and doxycycline. Tetracycline-susceptible M. hominis strains were four- to eightfold more susceptible to the glycylcyclines (0.12 to 0.25 micrograms/ml) than to tetracycline. Strains of M. hominis known to be resistant to tetracycline, doxycycline, and minocycline because of the tet(M) determinant were as susceptible to the glycylcyclines as the tetracycline-susceptible strains. For tetracycline-susceptible U. urealyticum strains, the glycylcyclines showed the same activity as tetracycline (MICs at which 50% of the isolates are inhibited of 1 to 2 micrograms/ml). Tetracycline-resistant strains of U. urealyticum were resistant to doxycycline and minocycline and showed variable susceptibility to the glycylcyclines (range, 0.5 to 32 micrograms/ml). In view of the increasing resistance of M. hominis and U. urealyticum strains to tetracyclines, the glycylcyclines have promise, pending assessment of their pharmacokinetic and safety profiles.
In vitro antimycoplasmal activities of rufloxacin and its metabolite MF 922
Authors: Furneri P M , Bisignano G , Cerniglia G , Nicoletti G , Cesana M , Tempera G
Published: June 2012

The in vitro activities of rufloxacin and its metabolite, MF 922, were compared with those of ofloxacin, ciprofloxacin, erythromycin, and minocycline against Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma fermentans, and Ureaplasma urealyticum. Rufloxacin, MF 922, and ciprofloxacin shared similar activities against all mycoplasmas tested. (MICs for 90% of isolates tested [MIC90s], 0.5 to 4 micrograms/ml. Ofloxacin had the lowest MIC90s for U. urealyticum, M. fermentans, and M. hominis (MIC90s, 0.25 to 1 micrograms/ml) and erythromycin had the lowest MIC90 for M. pneumoniae (MIC90, 0.004 micrograms/ml).
Efficacy of escalating doses of liposomal amphotericin B (AmBisome) against hematogenous Candida lusitaniae and Candida krusei infection in neutropenic mice
Authors: Karyotakis N C , Anaissie E J
Published: June 2012

Immunosuppressed CF1 mice were infected intravenously with two strains of Candida krusei and four strains of Candida lusitaniae (two of which were resistant to amphotericin B). Mice were treated with 1 or 2 mg of amphotericin B desoxycholate per kg of body weight per day or escalating doses of liposomal amphotericin B (8 to 30 mg/kg/day) or were left untreated. Higher doses of liposomal amphotericin B were as effective as standard dose of amphotericin B desoxycholate in prolonging survival but were significantly more effective in reducing the fungal burden in the kidneys of animals infected with both C. krusei strains and the C. lusitaniae strains that were susceptible to amphotericin B desoxycholate. This advantage of liposomal amphotericin B therapy could not be demonstrated in mice infected with the C. lusitaniae strains that were resistant to amphotericin B desoxycholate.
In vivo efficacies of beta-lactam-beta-lactamase inhibitor combinations against a TEM-26-producing strain of Klebsiella pneumoniae
Authors: Rice L B , Carias L L , Shlaes D M
Published: June 2012

We examined the efficacies of the beta-lactam-beta-lactamase inhibitor combinations ampicillin-sulbactam and piperacillin-tazobactam in the treatment of intra-abdominal abscesses caused by a TEM-26-producing strain of Klebsiella pneumoniae. At lower doses, both combinations reduced abscess colony counts by more than 3 log10 CFU/g from that of untreated controls, but treatment with these drugs was inferior to treatment with imipenem. Increasing the doses of the combinations resulted in a further decrease in abscess CFU to a level where both were similar to imipenem in efficacy. These results suggest that the beta-lactam-beta-lactamase inhibitor combinations ampicillin-sulbactam and piperacillin-tazobactam may be viable alternatives for the treatment of serious infections caused by susceptible extended-spectrum beta-lactamase-producing strains of K. pneumoniae.
Clarithromycin, dapsone, and a combination of both used to treat or prevent disseminated Mycobacterium avium infection in beige mice
Authors: Bermudez L E , Inderlied C B , Kolonoski P , Petrofsky M , Young L S
Published: June 2012

Bacteremic infection caused by organisms of the Mycobacterium avium complex (MAC) is common in patients with AIDS. We evaluated both clarithromycin and dapsone alone and in combination for the treatment and prevention of disseminated MAC disease in beige mice. In the therapeutic model, C57BL/6 beige mice were infected intravenously with strain 101 of MAC (serovar 1). After 1 week postinfection, mice were given clarithromycin (200 mg/kg of body weight per day) and dapsone (15 mg/kg of body weight per day) alone or in combination by gavage. Treatment with clarithromycin resulted in a significant reduction in bacteremia and the numbers of CFU of MAC in the liver and spleen. Treatment with dapsone had no effect on the mycobacterial counts in blood, liver, or spleen, and the combination of dapsone with clarithromycin was no better than clarithromycin as a single agent. Clarithromycin and dapsone were used to prevent systemic disease in beige mice infected orally with MAC 101. Clarithromycin prophylaxis was associated with a significant reduction in the numbers of bacteria in the liver, spleen, and appendix compared with those in controls. Prophylaxis with dapsone resulted in a mild reduction in the numbers of MAC in the spleen but not in the other tissues. Clarithromycin both treats and prevents MAC disease in beige mice. Dapsone has no therapeutic effect, but it does have a slight prophylactic effect, and in combination with clarithromycin it does not abrogate the effect of clarithromycin.
Nitric oxide donor-mediated killing of bioluminescent Escherichia coli
Authors: Virta M , Karp M , Vuorinen P
Published: June 2012

The antimicrobial activities of two nitric oxide-releasing compounds against Escherichia coli were investigated by using recombinant E. coli cloned with a luciferase gene from Pyrophorus plagiophthalamus. Since luciferase uses intracellular ATP to generate visible light which can be measured from living cells in real time, we wanted to compare the extent to which cell viability parallels light emission. Results from luminescence measurements and CFU counts were in good agreement, and the decrease in light emission was shown to provide a rapid and more sensitive indication of cytotoxicity.
Penetration of piperacillin-tazobactam into bronchial secretions after multiple doses to intensive care patients
Authors: Jehl F , Muller-Serieys C , de Larminat V , Monteil H , Bergogne-Berezin E
Published: June 2012

The penetration of piperacillin-tazobactam in eight mechanically ventilated intensive care patients (age, 56.0 +/- 12.2 years, and weight, 76.5 +/- 15.2 kg [means +/- standard deviations]) with bacterial pneumonia was investigated. They were given intravenous doses of piperacillin (4 g) and tazobactam (0.5 g) as 30-min infusions every 6 h. The kinetic study was performed after the fourth dose on day 2 of treatment. Samples of blood and bronchial secretions (BS) were collected before the fourth dosing and 0.5, 1, 2, 4, and 6 h after the end of infusion. Drug concentrations in both sera and BS were measured by high-performance liquid chromatography. Concentrations (in micrograms per milliliter) in serum were 184.80 +/- 63.03 and 40.03 +/- 30.79 for piperacillin and 23.05 +/- 7.53 and 4.86 +/- 4.54 for tazobactam at 0.5 and 6 h, respectively, after the end of infusion. The corresponding concentrations (in micrograms per milliliter) in BS were 29.33 +/- 25.08 and 20.25 +/- 19.11 for piperacillin and 6.86 +/- 4.25 and 4.25 +/- 2.78 for tazobactam. The percentages for the extent of penetration of piperacillin and tazobactam, as defined by the BS/serum area under the curve ratio, were 35.70 and 78.42%, respectively. These data indicate good penetration of both piperacillin and tazobactam into BS. The concentrations of tazobactam in BS are persistent and high enough to exceed the values found to be effective in vitro against the tazobactam-susceptible beta-lactamases produced by the most important pathogens responsible for nosocomial pneumonia.
Phosphatidylazidothymidine and phosphatidyl-ddC: assessment of uptake in mouse lymphoid tissues and antiviral activities in human immunodeficiency virus-infected cells and in Rauscher leukemia virus-infected mice
Authors: Hostetler K Y , Richman D D , Sridhar C N , Felgner P L , Felgner J , Ricci J , Gardner M F , Selleseth D W , Ellis M N
Published: June 2012

During the early stages of human immunodeficiency virus (HIV) infection, although symptoms are absent and viral replication in peripheral blood mononuclear cells is low, substantial levels of HIV replication can be documented in lymphoid tissue [G. Pantaleo, C. Graziosi, J.F. Demarest, L. Butini, M. Montroni, C.H. Fox, J.M. Orenstein, D.P. Kotler, and A.S. Fauci, Nature (London) 362:355-358, 1993, and J. Embretsen, M. Zupancic, J.L. Ribas, A. Burke, P. Racz, K. Tenner-Tacz, and A.T. Haase, Nature (London) 362:359-362, 1993]. This observation suggests that earlier treatment of HIV infection may be indicated and that strategies for enhancing drug targeting to the lymphoid tissue reservoris of HIV infection may be beneficial. To address this issue, we synthesized dioleoylphosphatidyl-ddC (DOP-ddC) and dipalmitoylphosphatidyl-3'-azido-3'-deoxythymidine (DPP-AZT), phospholipid prodrugs which form lipid bilayers and which are readily incorporated into liposomes. The anti-HIV activity of DOP-ddC was similar to that of ddC in HIV type 1-infected HT4-6C cells, but DPP-AZT was considerably less active than AZT in HT4-6C cells. Liposomes containing DOP-[3H]ddC or DPP-[3H]AZT administered intraperitoneally to mice produced greater levels of total radioactivity over time in plasma, spleen, and lymphoid tissue relative to the results with [3H]ddC and [3H]AZT, respectively. DPP-AZT administered intraperitoneally in liposomes as a single daily dose to mice infected with Rauscher leukemia virus prevented increased spleen weight and reverse transcriptase levels in serum with a dose-response roughly comparable to that of AZT given continuously in the drinking water. DOP-ddC, DPP-AZT, and lipid conjugates of other antiretroviral nucleosides may provide higher levels of drug over time in plasma and in lymph nodes and spleen, important reservoirs of HIV infection, and may represent an interesting alternative approach to antiviral nucleoside treatment of AIDS.
Possible implications of doxycycline-rifampin interaction for treatment of brucellosis
Authors: Colmenero J D , Fernández-Gallardo L C , Agúndez J A , Sedeño J , Benítez J , Valverde E
Published: June 2012

We studied the possible interaction between rifampin and doxycycline in 20 patients with brucellosis treated randomly with either doxycycline and streptomycin or doxycycline and rifampin. The doxycycline levels in the plasma of patients in the group treated with rifampin were significantly lower than those in the plasma of patients treated with doxycycline and streptomycin. Furthermore, clearance in patients treated with rifampin was significantly higher than that in patients treated with doxycycline and streptomycin, and consequently, the elimination half-life and the area under the concentration-time curve were significantly lower. There was no therapeutic failure or relapse in the group treated with doxycycline and streptomycin, whereas 2 of 10 patients in the group treated with doxycycline and rifampin had a therapeutic failure or relapse. The plasma doxycycline levels had an inverse correlation with plasma rifampin levels. In the group treated with rifampin, those who were rapid acetylators had lower levels of doxycycline. In conclusion, combined treatment with rifampin reduces the levels of doxycycline in plasma. These data suggest that therapeutic failures or relapses may result from this interaction.
Effect of magnesium complexation by fluoroquinolones on their antibacterial properties
Authors: Lecomte S , Baron M H , Chenon M T , Coupry C , Moreau N J
Published: June 2012

By using infrared and 19F nuclear magnetic resonance spectroscopies, we localized the binding site and measured the affinity of magnesium for six fluoroquinolones. It was proven that magnesium is situated between the ketone and the carboxylate groups. We determined the binding constants for the 1:1 Mg(2+)-drug complex in solution. Sparfloxacin and pefloxacin, with affinity constants (Ka) of (10.1 +/- 0.6) x 10(2) M-1 and (21 +/- 1) x 10(2) M-1, respectively, were the least and the most bound, respectively. The trend of the affinities of the assayed fluoroquinolones for magnesium was correlated with their antimicrobial activities against four bacteria and with their accumulation by these bacteria. The reference strain, Escherichia coli KL16, and two resistant mutants, NalA (gyrase mutation) and NalB (uptake defect), plus Staphylococcus aureus 209P were used. It appeared that, in every case, an impairment of accumulation is responsible for the increase in the MICs observed upon the addition of magnesium.