bluuebunny/crossref_metadata_2025 huggingface dataset:
Susceptibilities of Listeria species isolated from food to nine antimicrobial agents
Authors: Franco Abuín C M , Quinto Fernández E J , Fente Sampayo C , Rodríguez Otero J L , Domínguez Rodríguez L , Cepeda Sáez A
Published: June 2012

The agar dilution method was used to determine the activities of gentamicin, erythromycin, streptomycin, chloramphenicol, ampicillin, sulfamethazine, cephalothin, penicillin G, and tetracycline against 73 strains belonging to the genus Listeria (L. innocua, L. seeligeri, and L. monocytogenes). All strains were isolated from raw milk, cheese, the dairy processing plant, poultry, and the poultry slaughterhouse. Gentamicin, ampicillin, and erythromycin, of which the MICs for 90% of the strains tested for all three species were < or = 5.96 micrograms/ml, were found to be the most active agents studied. Most of the L. innocua strains isolated from poultry and the poultry slaughterhouse were resistant to tetracycline.
Activity of clinafloxacin against multidrug-resistant Enterococcus faecium
Authors: Burney S , Landman D , Quale J M
Published: June 2012

Enterococci resistant to ampicillin, vancomycin, and/or aminoglycosides are a growing clinical problem. We studied the in vitro activity of the new fluoroquinolone clinafloxacin (PD 127,391) against 15 clinical isolates of multidrug-resistant Enterococcus faecium. In kill-kinetic studies, clinafloxacin (1 microgram/ml) was bactericidal against 7 of 12 susceptible isolates, although substantial regrowth occurred in 4 isolates at 48 h. The addition of ampicillin (20 micrograms/ml) resulted in bactericidal activity in all 12 isolates, and no regrowth was seen. For three isolates resistant to clinafloxacin, effective killing was not observed at these concentrations of antibiotics. Clinafloxacin with ampicillin shows promising activity against many of these multiply resistant enterococci.
Increased activity of a new chlorofluoroquinolone, BAY y 3118, compared with activities of ciprofloxacin, sparfloxacin, and other antimicrobial agents against anaerobic bacteria
Authors: Aldridge K E
Published: June 2012

A total of 435 clinical isolates of anaerobes were tested with a broth microdilution method to determine the activity of BAY y 3118 compared with those of other agents against anaerobic bacteria. All strains of Bacteroides capillosus, Prevotella spp., Porphyromonas spp., Fusobacterium spp., Clostridium spp., Eubacterium spp., Peptostreptococcus spp., and Veillonella parvula were susceptible (MICs of < or = 2 micrograms/ml) to BAY y 3118. Against the 315 strains of the Bacteroides fragilis group, five strains required elevated MICs (> or = 4 micrograms/ml) of BAY y 3118. Only imipenem and metronidazole were active against all anaerobes. Overall, BAY y 3118 was more active than ciprofloxacin, sparfloxacin, piperacillin, cefotaxime, and clindamycin against the test isolates.
Evaluation of curative anticryptosporidial activity of paromomycin in a dexamethasone-treated rat model
Authors: Verdon R , Polianski J , Gaudebout C , Marche C , Garry L , Pocidalo J J
Published: June 2012

A dexamethasone-treated rat model of cryptosporidiosis was used to evaluate the curative activity of paromomycin. Although eradication of the parasite could not be demonstrated, statistically significant decreases in oocyst excretion and in the intensity of ileal parasitism were observed in animals receiving 100 mg of paromomycin per kg of body weight per day.
Molecular and genetic analysis of the Bacteroides uniformis cephalosporinase gene, cblA, encoding the species-specific beta-lactamase
Authors: Smith C J , Bennett T K , Parker A C
Published: June 2012

The gene, cblA, encoding the species-specific, clavulanate-susceptible, endogenous cephalosporinase was cloned from Bacteroides uniformis WAL-7088. The nucleotide sequence was determined, and the cblA structural gene was found to be 891 nucleotides, with a 48% G+C composition, which is similar to that of the B. uniformis genome. The cblA open reading frame encoded an Ambler class A beta-lactamase polypeptide precursor of 296 amino acid residues with a predicted molecular weight of 33,450. A beta-lactamase-deficient B. uniformis mutant with increased beta-lactam susceptibility was constructed by insertional inactivation of the chromosomal gene. This mutant was complemented by plasmids bearing the cblA gene, and the resulting strains were resistant to cephaloridine and had a beta-lactamase that comigrated with the parental beta-lactamase on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (30,500 Da) and in isoelectric focusing gels (pI 4.6), confirming a role for this beta-lactamase in resistance.
Comparison of ofloxacin and ceftriaxone for short-course treatment of enteric fever
Authors: Smith M D , Duong N M , Hoa N T , Wain J , Ha H D , Diep T S , Day N P , Hien T T , White N J
Published: June 2012

An open, randomized comparison of ofloxacin (200 mg, every 12 h) given orally for 5 days and ceftriaxone (3 g, once daily) given intravenously for 3 days in the treatment of uncomplicated enteric fever was conducted in Ho Chi Minh City, Vietnam. Salmonella paratyphi type A was isolated from six patients. Salmonella typhi was isolated from 41 patients; 63% of these isolates were resistant to multiple antibiotics: ampicillin, chloramphenicol, sulfamethoxazole, trimethoprim, and tetracycline. Of the culture-confirmed cases, treatment with ofloxacin resulted in complete cure of all 22 patients, whereas 18 of 25 patients treated with ceftriaxone were completely cured (P < 0.01). In the ceftriaxone group, there were six acute treatment failures and one relapse. Mean +/- standard deviation fever clearance times were 81 +/- 25 h for ofloxacin and 196 +/- 87 h for ceftriaxone (P < 0.0001). Short-course treatment with oral ofloxacin (5 days) is significantly better than that with ceftriaxone (3 days) and will be of particular benefit in areas where multiresistant strains of S. typhi are encountered.
Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: resistance to tetracycline, chloramphenicol, and norfloxacin
Authors: Li X Z , Livermore D M , Nikaido H
Published: June 2012

Most strains of Pseudomonas aeruginosa are significantly more resistant, even in the absence of R plasmids, to many antimicrobial agents, including beta-lactams, tetracycline, chloramphenicol, and fluoroquinolones, than most other gram-negative rods. This broad-range resistance has so far been assumed to be mainly due to the low permeability of the P. aeruginosa outer membrane. The intrinsic-resistance phenotype becomes further enhanced in "intrinsically carbenicillin-resistant" isolates, which were often assumed to produce outer membranes of even lower permeability. It has been shown, however, that this hypothesis cannot explain the beta-lactam resistance of these isolates (D.M. Livermore and K.W.M. Davy, Antimicrob. Agents Chemother. 35:916-921, 1991). In this study, we examined the uptake of tetracycline, chloramphenicol, and norfloxacin by intact cells using strains showing widely different levels of intrinsic resistance. Their accumulation and the response to the addition of a proton conductor showed that even relatively susceptible strains of P. aeruginosa actively pump out these compounds from the cell and that the efflux activity becomes much stronger in strains showing higher levels of intrinsic resistance. We conclude that the efflux mechanism(s) are likely to contribute significantly to the intrinsic resistance of P. aeruginosa isolates to tetracycline, chloramphenicol, and fluoroquinolones, as does the low permeability of the outer membrane. This conclusion is supported by the observation that the hypersusceptibility to various agents of the mutant K799/61 (W. Zimmermann, Antimicrob. Agents Chemother. 18:94-100, 1980) was apparently caused by the lack of active efflux. Although the hypersusceptibility of this mutant has hitherto been assumed to be solely due to its higher outer membrane permeability, its outer membrane was shown to have a coefficient of permeability to cephaloridine that was not significantly different from that of the parent, resistant strain K799/WT. The strains with elevated intrinsic resistance overproduced two cytoplasmic membrane proteins and one outer membrane protein; at least two of these proteins appeared different from the proteins overproduced in the recently described mutant with a derepressed multidrug efflux system, MexA-MexB-OprK (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993).
Antimalarial activity of WR 243251, a Dihydroacridinedione
Authors: Berman J , Brown L , Miller R , Andersen S L , McGreevy P , Schuster B G , Ellis W , Ager A , Rossan R
Published: June 2012

WR 243251 is a dihydroacridinedione that was evaluated for antimalarial blood schizonticidal activity in vitro and in vivo. The in vitro doses calculated to kill 50% of organisms were 11 nM for a chloroquine-susceptible, mefloquine-resistant standard strain and 25 nM for a chloroquine- and pyrimethamine-resistant standard strain. The total dose needed to cure 100% of mice infected with a drug-susceptible strain of Plasmodium berghei was 12 to 20 mg/kg of body weight for both oral and subcutaneous administration. The regimen needed to cure 100% of Aotus monkeys infected with Plasmodium falciparum was 8 mg/kg/day for 3 days (chloroquine-susceptible strain) and 16 mg/kg/day for 3 days (chloroquine-resistant strain). The 100% curative doses for Aotus monkeys did not increase for parasites previously exposed to subcurative doses. The absolute value of the curative doses of WR 243251 was comparable to or lower than the values for clinical antimalarial agents. The high absolute activity, comparability of activities against susceptible and resistant parasites, and inability to induce resistance by exposure to subcurative doses suggest that WR 243251 has strong potential as a blood schizonticidal agent.
Protective effects of sparfloxacin in experimental pneumonia caused by Chlamydia pneumoniae in leukopenic mice
Authors: Nakata K , Okazaki Y , Hattori H , Nakamura S
Published: June 2012

The in vivo antichlamydial activities of sparfloxacin and reference drugs were examined in a experimental model of pneumonia caused by Chlamydia pneumoniae in leukopenic mice; their in vitro activities were also examined. The most potent agents in vitro were sparfloxacin (MICs for C. pneumoniae Kajaani and IOL 207, (0.031 and 0.031 micrograms/ml, respectively), clarithromycin (0.031 and 0.031 micrograms/ml, respectively), and minocycline (0.031 and 0.031 micrograms/ml, respectively); these were followed by tosufloxacin (0.063 and 0.125 micrograms/ml, respectively) and ofloxacin (0.5 and 0.5 micrograms/ml, respectively). The MBCs of sparfloxacin, tosufloxacin, ofloxacin, clarithromycin, and minocycline for these two strains were 0.063 and 0.063 micrograms/ml, 0.125 and 0.25 micrograms/ml, 1.0 and 1.0 micrograms/ml, 0.125 and 0.125 micrograms/ml, and 0.25 and 0.25 micrograms/ml, respectively. Fatal pneumonia was induced by intranasal inoculation of cyclophosphamide-treated leukopenic mice with C. pneumoniae IOL 207; infiltration of neutrophils and lymphocytes was observed in the lungs of these mice by histopathological examination. The 50% effective dose of sparfloxacin (oral dose of 0.97 mg/kg of body weight) against the pneumonia was the lowest among the drugs tested; this was followed by those of minocycline (2.22 mg/kg), tosufloxacin (3.47 mg/kg), clarithromycin (4.66 mg/kg), and ofloxacin (16.6 mg/kg). The results indicate that it may be worthwhile to use sparfloxacin against C. pneumoniae infections in humans.
Genetic relationship between soxRS and mar loci in promoting multiple antibiotic resistance in Escherichia coli
Authors: Miller P F , Gambino L F , Sulavik M C , Gracheck S J
Published: June 2012

Multiple antibiotic resistance in Escherichia coli has typically been associated with mutations at the mar locus, located at 34 min on the E. coli chromosome. A new mutant, marC, isolated on the basis of a Mar phenotype but which maps to the soxRS (encoding the regulators of the superoxide stress response) locus located at 92 min, is described here. This mutant shares several features with a known constitutive allele of the soxRS gene, prompting the conclusion that it is a highly active allele of this gene. The marC mutation has thus been given the designation soxR201. This new mutant was used to examine the relationship between the mar and sox loci in promoting antibiotic resistance. The results of these studies indicate that full antibiotic resistance resulting from the soxR201 mutation is partially dependent on an intact mar locus and is associated with an increase in the steady-state level of mar-specific mRNA. In addition, paraquat treatment of wild-type cells is shown to increase the level of antibiotic resistance in a dose-dependent manner that requires an intact soxRS locus. Conversely, overexpression of MarA from a multicopy plasmid results in weak activation of a superoxide stress response target gene. These findings are consistent with a model in which the regulatory factors encoded by the marA and soxS genes control the expression of overlapping sets of target genes, with MarA preferentially acting on targets involved with antibiotic resistance and SoxS directed primarily towards components of the superoxide stress response. Furthermore, compounds frequently used to induce the superoxide stress response, including paraquat, menadione, and phenazine methosulfate, differ with respect to the amount of protection provided against them by the antibiotic resistance response.
Inhibition of alpha-glucosidase I of the glycoprotein-processing enzymes by 6-O-butanoyl castanospermine (MDL 28,574) and its consequences in human immunodeficiency virus-infected T cells
Authors: Taylor D L , Kang M S , Brennan T M , Bridges C G , Sunkara P S , Tyms A S
Published: June 2012

The 6-O-butanoyl derivative of castanospermine (MDL 28,574) was previously shown to be approximately 30-fold more potent than the naturally occurring molecule at inhibiting the replication of human immunodeficiency virus (HIV) (D. L. Taylor, P. S. Sunkara, P. S. Liu, M. S. Kang, T. L. Bowlin, and A. S. Tyms, AIDS 5:693-698, 1991). We now report that consistent with its improved anti-HIV activity, MDL 28,574 is more effective (50% inhibitory concentration [IC50], 20 microM) than the parent molecule (IC50, 254 microM) at causing the accumulation of glucosylated oligosaccharides in HIV-infected cells by inhibition of glycoprotein processing. These were predominantly of the glucose 3 type, as determined by P4 Bio-Gel analysis after digestion with purified alpha-glucosidase I, indicating that, intracellularly, this enzyme is the major target for inhibition. MDL 28,574, however, was less active (IC50, 1.27 microM) than castanospermine (IC50, 0.12 microM) against the mutual target enzyme, cellular alpha-glucosidase I, in a cell-free assay system. The increased effects of MDL 28,574 against alpha-glucosidase I in cell culture were attributed to the improved cellular uptake of the more lipophilic derivative. Inhibition of this enzyme activity in HIV-infected H9 cells impaired viral glycoprotein processing and resulted in the expression of abnormally configured gp120. This did not affect virus production, but the virions had decreased infectivity which was partially related to a reduced ability to bind to CD4+ T cells.
Activities of the benzoxazinorifamycin KRM 1648 and ethambutol against Mycobacterium avium complex in vitro and in macrophages
Authors: Inderlied C B , Barbara-Burnham L , Wu M , Young L S , Bermudez L E
Published: June 2012

KRM 1648 is a 4-aminobenzoxazine derivative of rifamycin S with potent in vitro activity against the Mycobacterium avium complex (MAC); the MIC for 90% of 24 MAC isolates from AIDS patients was 0.25 microgram/ml as determined by a radiometric broth macrodilution assay. KRM 1648 was bactericidal for MAC isolates in Middlebrook 7H9 broth, with a reduction in viability of 1 to 4 orders of magnitude over 72 h. In human macrophages, KRM 1648 also was bactericidal, with a reduction of 3 to 4 orders of magnitude in CFU per ml of macrophage lysate at a concentration of 1 microgram/ml; however, the bactericidal activity varied approximately 10-fold among the three MAC serovars tested. In growth medium, ethambutol potentiated the effect of KRM 1648, but this potentiation was modest when tested against MAC in macrophages and also varied between MAC strains. KRM 1648 has potential as an antimycobacterial agent for MAC disease, perhaps in combination with other agents so that the use of lower dosages of KRM 1648 than are needed with other rifamycins may be possible.
Activity of KRM 1648 alone or in combination with ethambutol or clarithromycin against Mycobacterium avium in beige mouse model of disseminated infection
Authors: Bermudez L E , Kolonoski P , Young L S , Inderlied C B
Published: June 2012

Rifamycins are active against slowly growing mycobacteria, such as Mycobacterium tuberculosis and Mycobacterium kansasii, but the majority of rifamycins thus far investigated both in vitro and in vivo are inactive or have only modest activity against the Mycobacterium avium complex (MAC). We investigated the activity of three doses of the semisynthetic benzoxazinorifamycin KRM 1648, alone or in combination with ethambutol or clarithromycin, in beige mice challenged with the MAC strain 101. Our results show the following. (i) KRM 1648 was significantly effective against MAC infection as determined by the reduction of the number of bacteria in the blood, liver, and spleen when administered at doses of 20 and 40 mg/kg of body weight per day but not at 10 mg/kg/day, compared with untreated controls. (ii) KRM 1648 (40 mg/kg/day) administered in combination with ethambutol (100 mg/kg/day) resulted in significant reduction in bacteremia compared with values for untreated controls (P 0.001), KRM 1648 alone (P = 0.019), and ethambutol alone (P = 0.003). Furthermore, the combination of KRM 1648 and ethambutol was associated with a significant decrease of the number of bacteria in the spleen and the liver compared with values for both untreated controls and each drug alone (P < 0.001 for all comparisons). (iii) KRM 1648 (40 mg/kg/day) administered in combination with clarithromycin (200 mg/kg/day) resulted in a significant decrease of the number of bacteria in the blood and the spleen compared with the number for untreated controls (P < 0.001 for all comparisons). In our experience, using MAC 101 as the challenging organism, KRM 1648 is the first the number of bacteria in the blood and spleen compared with the number for untreated controls (P >0.001 for all comparions). In our experience, using MAC 101 as the challenging organism, KRM 1648 is the first rifamycin with significant activity in vivo against MAC infection in beige mice.
Efficacy of azithromycin as a causal prophylactic agent against murine malaria
Authors: Andersen S L , Ager A L , McGreevy P , Schuster B G , Ellis W , Berman J
Published: June 2012

The efficacy of the newly marketed azalide azithromycin was compared with that of the clinical agent doxycycline in a murine model of sporozoite-induced malaria. Drug was administered once; Plasmodium yoelii sporozoites were administered 2 h later; survival at day 60 was determined. For parenterally administered drug, 160 mg of azithromycin or doxycycline per kg of body weight was 100% effective; 40 mg of azithromycin per kg was 80% effective, but 40 mg of doxycycline per kg was 40% effective. Orally administered azithromycin was somewhat less effective than parenterally administered drug, consistent with the 37% clinical oral bioavailability of this agent. For orally administered azithromycin, 160 mg/kg was 100% effective and 40 mg/kg was 40% effective. The efficacy of azithromycin in comparison with that of doxycycline and the known prolonged levels of azithromycin in the livers of humans suggest that azithromycin has potential as a clinical causal prophylactic agent for malaria.
Contribution of VanY D,D-carboxypeptidase to glycopeptide resistance in Enterococcus faecalis by hydrolysis of peptidoglycan precursors
Authors: Arthur M , Depardieu F , Snaith H A , Reynolds P E , Courvalin P
Published: June 2012

The vanR, vanS, vanH, vanA, and vanX genes of enterococcal transposon Tn1546 were introduced into the chromosome of Enterococcus faecalis JH2-2. Complementation of this portion of the van gene cluster by a plasmid encoding VanY D,D-carboxypeptidase led to a fourfold increase in the vancomycin MIC (from 16 to 64 micrograms/ml). Multicopy plasmids pAT80 (vanR vanS vanH vanA vanX) and pAT382 (vanR vanS vanH vanA vanX vanY) conferred similar levels of vancomycin resistance to JH2-2. The addition of D-alanine (100 mM) to the culture medium restored the vancomycin susceptibility of E. faecalis JH2-2/pAT80. The pentapeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala partially replaced pentadepsipeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Lac when the strain was grown in the presence of D-alanine. In contrast, resistance mediated by pAT382 was almost unaffected by the addition of the amino acid. Expression of the vanY gene of pAT382 resulted in the formation of the tetrapeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala, indicating that a portion of the cytoplasmic precursors had been hydrolyzed. These results show that VanY contributes to glycopeptide resistance in conditions in which pentapeptide is present in the cytoplasm above a threshold concentration. However, the contribution of the enzyme to high-level resistance mediated by Tn1546 appears to be moderate, probably because hydrolysis of D-alanyl-D-alanine by VanX efficiently prevents synthesis of the pentapeptide.
Inhibition of sterol biosynthesis in Saccharomyces cerevisiae and Candida albicans by 22,23-epoxy-2-aza-2,3-dihydrosqualene and the corresponding N-oxide
Authors: Balliano G , Milla P , Ceruti M , Carrano L , Viola F , Brusa P , Cattel L
Published: June 2012

The abilities of 22,23-epoxy-2-aza-2,3-dihydrosqualene and the corresponding N-oxide, 22,23-epoxy-2-aza-2,3-dihydrosqualene-N-oxide, to inhibit sterol biosynthesis were studied in microsomes and cells of Saccharomyces cerevisiae and Candida albicans. 22,23-Epoxy-2-aza-2,3-dihydrosqualene, which differs from the other inhibitor only in lacking oxygen at position 2, exhibited higher inhibitory properties in all preparations tested. The different levels of effectiveness of the two azasqualene derivatives were evident mostly in microsomes from S. cerevisiae (the 50 inhibitory concentrations of the 2-aza derivative and the corresponding N-oxide on oxidosqualene cyclase were 30 and 120 microM respectively) and in cell cultures of the same strain (1 order of magnitude separated the inhibitory activities of the two compounds on sterol biosynthesis). A possible explanation for the differences between 22,23-epoxy-2-aza-2,3-dihydrosqualene and the corresponding N-oxide arose from the study of their metabolic fates in vivo and in vitro. While the 2-aza derivative did not undergo any transformation, the N-oxide compound was actively reduced to the corresponding amine in microsomes and in cells of both yeast strains. 22,23-Epoxy-2-aza-2,3-dihydrosqualene-N-oxide seems to behave as a proinhibitor of sterol biosynthesis, becoming active only after transformation into the active form 22,23-epoxy-2-aza-2,3-dihydrosqualene.
Cloning and nucleotide sequence of Pseudomonas aeruginosa DNA gyrase gyrA gene from strain PAO1 and quinolone-resistant clinical isolates
Authors: Kureishi A , Diver J M , Beckthold B , Schollaardt T , Bryan L E
Published: June 2012

The Pseudomonas aeruginosa DNA gyrase gyrA gene was cloned and sequenced from strain PAO1. An open reading frame of 2,769 bp was found; it coded for a protein of 923 amino acids with an estimated molecular mass of 103 kDa. The derived amino acid sequence shared 67% identity with Escherichia coli GyrA and 54% identity with Bacillus subtilis GyrA, although conserved regions were present throughout the sequences, particularly toward the N terminus. Complementation of an E. coli mutant with a temperature-sensitive gyrA gene with the PAO1 gyrA gene showed that the gene is expressed in E. coli and is able to functionally complement the E. coli DNA gyrase B subunit. Expression of PAO1 gyrA in E. coli or P. aeruginosa with mutationally altered gyrA genes caused a reversion to wild-type quinolone susceptibility, indicating that the intrinsic susceptibility of the PAO1 GyrA to quinolones is comparable to that of the E. coli enzyme. PCR was used to amplify 360 bp of P. aeruginosa gyrA encompassing the so-called quinolone resistance-determining region from ciprofloxacin-resistant clinical isolates from patients with cystic fibrosis. Mutations were found in three of nine isolates tested; these mutations caused the following alterations in the sequence of GyrA: Asp at position 87 (Asp-87) to Asn, Asp-87 to Tyr, and Thr-83 to Ile. The resistance mechanisms in the other six isolates are unknown. The results of the study suggested that mechanisms other than a mutational alteration in gyrA are the most common mechanism of ciprofloxacin resistance in P. aeruginosa from the lungs of patients with cystic fibrosis.
In vivo efficacy of a broad-spectrum cephalosporin, ceftriaxone, against penicillin-susceptible and -resistant strains of Streptococcus pneumoniae in a mouse pneumonia model
Authors: Moine P , Vallée E , Azoulay-Dupuis E , Bourget P , Bédos J P , Bauchet J , Pocidalo J J
Published: June 2012

The increasing emergence of penicillin-resistant (Pr) strains of Streptococcus pneumoniae could pose a therapeutic problem in the next few years. Ceftriaxone (CRO), a broad-spectrum cephalosporin, exhibits a smaller increase in MICs against Pr S. pneumoniae strains than amoxicillin (AMO) (usually referred as to the "gold standard" therapy for pneumococcal infections). Therefore, we compared their respective efficacies in a leukopenic Swiss mouse model of pneumococcal pneumonia. Infection was induced with two serotype 19 strains: a penicillin-susceptible (Ps) strain (MICs of < 0.01 for penicillin, 0.03 for AMO, and 0.03 for CRO) and a Pr strain (MICs of 4 for penicillin, 2 for AMO, and 0.5 for CRO). Untreated mice died within 2 or 3 days. Against the Ps strain, the minimal protective dose (two subcutaneous injections at 12-h intervals for 3 days) for both CRO and AMO was 5 mg/kg of body weight (87% survivors). Ten-fold-increased doses of CRO (50 mg/kg) gave similar protection (75% survivors) against the Pr strain, whereas 20- and 40-fold-increased doses of AMO protected 0 and 34% of the animals, respectively, against the Ps strain. CRO had a marked and prolonged antibacterial effect in the lungs (2.7-log-unit reduction of CFU in 24 h after a single 50-mg/kg injection) against the Pr strain in comparison with AMO. A standard dosage of 50 mg of CRO per kg in mice resulted in peak levels in serum and protein binding comparable to those observed with 1 g given intravenously in humans. This dosage remained effective against a highly Pr S. pneumoniae strain in this model. The microbiological activity and pharmacodynamic and pharmacokinetic properties of CRO (time during which concentrations exceed the MIC for the test pathogen [delta t MIC], > or less than 8 h; and peak/MIC ratio, >90 for free active drug) accounted for its efficacy relative to AMO (50 mg/kg: delta t MIC, <2; peak/MIC ratio, <25) against the highly Pr S. pneumoniae strain used in this study.
Effect of fialuridine on replication of mitochondrial DNA in CEM cells and in human hepatoblastoma cells in culture
Authors: Colacino J M , Malcolm S K , Jaskunas S R
Published: June 2012

Fialuridine (FIAU) is a nucleoside analog with potent activity against hepatitis B virus in vitro and in vivo. In this report, the effect of FIAU on mitochondrial DNA (mtDNA) replication in vitro was investigated. CEM cells, a cell line derived from human T cells, were incubated for 6 days in up to 20 microM FIAU. Total cellular DNA was isolated, normalized for the number of cells, and slot hybridized to a probe specific for mtDNA sequences. Treatment of CEM cells with FIAU did not result in a dose-dependent decrease in the amount of mtDNA. In contrast, dideoxycytidine (ddC) inhibited mtDNA replication by 50% at a concentration of approximately 0.1 microM. After 6 days of incubation, both compounds displayed a 50% toxic dose at a concentration of approximately 2 microM in CEM cells and approximately 34 microM in human hepatoblastoma cells (HepG2). In further experiments, CEM cells were incubated for 15 days in up to 2.5 microM FIAU, and again, no inhibition of mtDNA was observed. Over a 6-day incubation, FIAU, at concentrations of up to 200 microM, also failed to inhibit mtDNA replication in either HepG2 or HepG2 cells which constitutively replicate duck hepatitis B virus. In contrast, ddC inhibited mtDNA replication in these cells with a 50% inhibitory concentration of approximately 0.2 microM over a 6-day incubation. Treatment of cells with either FIAU or ddC resulted in a dose-dependent increase in lactate levels in the cell medium, indicating that any effect of FIAU on mitochondrial function may not be related to inhibition of mtDNA replication on the basis of the in vitro data. Alternative explanations for mitochondrial toxicity are considered.
Assays to detect and characterize human immunodeficiency virus type 1 (HIV-1) receptor antagonists, compounds that inhibit binding of the HIV-1 surface glycoprotein, gp120, to the CD4 receptor on human T lymphocytes
Authors: Clancy J , Tait-Kamradt A , Petitpas J , Manousos M , McGuirk P R , Subashi T , Watts P , Wondrack L
Published: June 2012

Human immunodeficiency virus type 1 infects human helper T lymphocytes by an interaction between gp120, the viral coat protein, and the T-cell receptor CD4. Two microtiter-based immunoassays, an enzyme-linked immunosorbent assay (ELISA) and a particle concentration fluorescence assay, were developed to measure gp120-CD4 binding and were then used to screen a variety of compounds for the inhibition of this interaction. Additional protocols, called "consumption assays," were defined to distinguish inhibitors which functioned by sequestering either gp120 or CD4 to prevent the final effective bimolecular interaction. Monoclonal antibodies of defined specificity and compounds known from other published studies to inhibit gp120-CD4 binding were tested in an attempt to validate the assays used in the study. Once the capacity of these assays to detect known gp120-CD4 inhibitors was confirmed, they were used to screen synthetic agents and fermentation broths for novel compounds that might be used as human immunodeficiency virus receptor antagonists. A 2,4-diaminoquinazoline, CP-101,816-1, was found to inhibit this interaction (50% inhibitory concentration in ELISA, 32.5 micrograms/ml) and to interact more strongly with CD4 than with gp120 in the consumption assays. The identification of a novel inhibitor, a 2,4-diaminoquinazoline, confirmed that such assays are useful for the detection of human immunodeficiency virus type 1 receptor antagonists.
Ticarcillin-clavulanic acid pharmacokinetics in preterm neonates with presumed sepsis
Authors: Burstein A H , Wyble L E , Gal P , Diaz P R , Ransom J L , Carlos R Q , Forrest A
Published: June 2012

The objective of the reported study was to characterize the pharmacokinetics of ticarcillin and clavulanic acid in premature low-birth-weight (less than 2,200 g) neonates with presumed sepsis. Eleven infants received 12 courses of ticarcillin-clavulanic acid at 75 mg/kg of body weight intravenously every 12 h. Blood samples were collected at 0.5, 1.5, 4, and 8 h following the infusion of the initial dose. The concentrations of ticarcillin and clavulanic acid were determined by a microbiologic assay. Median (interpatient coefficients of variation) values for the volume of the central compartment, total steady-state volume, distributional clearance, total clearance, and terminal elimination half-life for ticarcillin were 0.030 liter/kg (21%), 0.26 liter/kg (48%), 0.41 liter/h/kg (47%), 0.047 liter/h/kg (47%), and 4.2 h (45%), respectively. For clavulanic acid the parameters were 0.28 liter/kg (32%), 0.36 liter/kg (34%), 11 liters/h/kg (36%), 0.12 liters/h/kg (72%), and 1.95 h (40%), respectively. Our results suggest that the current dosing recommendations of 75 mg/kg every 12 h risk subtherapeutic clavulanic acid concentrations and that 50 mg/kg every 6 h is a more rational dosing strategy.
Comparison of aminoglycoside pharmacokinetics in Asian, Hispanic, and Caucasian patients by using population pharmacokinetic methods
Authors: Jhee S S , Burm J P , Gill M A
Published: June 2012

A population pharmacokinetic model for aminoglycosides was developed from 24 Hispanic, 16 Asian, and 22 Caucasian patients. A nonparametric expectation maximization algorithm for population modeling was used. With this one-compartment model, the parameters were the slope of the apparent volume of distribution versus weight (VS) and the slope of the elimination rate constant versus the creatinine clearance rate (KS). The mean VS (+/- standard deviation) was not different at 0.264 (+/- 0.05), 0.248 (+/- 0.055), and 0.260 (+/- 0.080) liter/kg of body weight for Asian, Hispanic, and Caucasian populations, respectively (P > 0.10). The KS means +/- standard deviations were 0.00424 +/- 0.00129, 0.00404 +/- 0.00160 and 0.00394 0.00103 [h(ml/min/1.73 m2)]-1 +/- for Hispanic, Asian, and Caucasian populations, respectively. Again, there was no statistical difference among the groups (P > 0.10). In conclusion, there are no differences in aminoglycoside pharmacokinetics among Asian, Hispanic, and Caucasian patients.
Analysis by PCR and direct DNA sequencing of gyrA mutations associated with fluoroquinolone resistance in Enterococcus faecalis
Authors: Korten V , Huang W M , Murray B E
Published: June 2012

A region of gyrA, the gene encoding subunit A of DNA gyrase, that is known to be associated with resistance was amplified and sequenced from 16 Enterococcus faecalis and Enterococcus faecium isolates. Six ciprofloxacin-resistant clinical isolates (MICs of ciprofloxacin, 32 to 64 micrograms/ml) and one multistep resistant laboratory mutant of E. faecalis (MIC of ciprofloxacin, 128 micrograms/ml) contained a change from serine to arginine or to isoleucine at codon 83 or a change from glutamic acid to lysine or to glycine at codon 87 (Escherichia coli GyrA coordinates); these changes have been associated with fluoroquinolone resistance in other species. No difference in the region studied was found in two ciprofloxacin-resistant E. faecium isolates (MICs, 32 micrograms/ml) or in four laboratory derived, spontaneous ciprofloxacin-resistant mutants of E. faecalis (MICs, 8 to 16 micrograms/ml), suggesting that other mechanisms may be responsible for fluoroquinolone resistance in some enterococci.
Effect of in vivo macrophage colony-stimulating factor on fungistasis of bronchoalveolar and peritoneal macrophages against Cryptococcus neoformans
Authors: Nassar F , Brummer E , Stevens D A
Published: June 2012

Macrophage colony-stimulating factor (M-CSF) given subcutaneously at a dose of 2.5 mg/kg of body weight (4.75 x 10(6) U/kg) to CD-1 male mice 8 to 12 weeks old was found to enhance significantly the fungistasis of bronchoalveolar macrophages (BAM) against Cryptococcus neoformans. When M-CSF was given 1, 3, 7, 9, or 13 days before an ex vivo challenge with C. neoformans, fungistasis was increased (P ranged from < 0.05 to < 0.001) compared with that induced by control BAM. A maximum effect was seen by days 1 and 3 after administration of M-CSF. Twenty-one days after M-CSF, BAM did not produce significantly enhanced fungistasis. M-CSF also significantly enhances the fungistatic effect of peritoneal macrophages (PM) if given 1, 3, and 7 days prior to testing against C. neoformans in comparison with control PM (P ranged from < 0.05 to < 0.001). PM did not produce enhanced fungistasis 9 or 13 days after administration of M-CSF. These studies demonstrating in vivo enhancement of anticryptococcal activity of macrophages with M-CSF provide a rationale for in vivo use of M-CSF to enhance resistance to infection with C. neoformans.
Effect of bismuth subsalicylate on ciprofloxacin bioavailability
Authors: Rambout L , Sahai J , Gallicano K , Oliveras L , Garber G
Published: June 2012

A single oral dose of 528 mg of bismuth subsalicylate (30 ml of Pepto-Bismol) had no significant effect on the plasma pharmacokinetics of a single oral dose of 750 mg of ciprofloxacin administered to 12 healthy volunteers (six men and six women). These results suggest that ciprofloxacin bioavailability will not be significantly decreased by single doses of bismuth subsalicylate when the two medications are administered simultaneously.
Inactivation of the macrolide antibiotics erythromycin, midecamycin, and rokitamycin by pathogenic Nocardia species
Authors: Yazawa K , Mikami Y , Sakamoto T , Ueno Y , Morisaki N , Iwasaki S , Furihata K
Published: June 2012

A survey of five Nocardia spp. with respect to susceptibility towards three macrolides (erythromycin, rokitamycin, and midecamycin) showed that the Nocardia spp. have different susceptibility profiles. Most of the resistance was due to the inactivation of the macrolides by phosphorylation, glycosylation, reduction, deacylation, or a combination thereof.
Emerging in vitro resistance to quinolones in penicillinase-producing Neisseria gonorrhoeae strains in Hawaii
Authors: Knapp J S , Ohye R , Neal S W , Parekh M C , Higa H , Rice R J
Published: June 2012

The susceptibilities of 37 penicillinase-producing strains of Neisseria gonorrhoeae (PPNG), isolated in Hawaii from December 1991 through January 1994, were determined to ciprofloxacin and ofloxacin, fluoroquinolone agents currently recommended by the Centers for Disease Control and Prevention as alternative regimens for the treatment of uncomplicated gonorrhea. Nine isolates (24.3%) exhibited decreased susceptibilities (MICs, > or = 0.06 microgram/ml) to ciprofloxacin and ofloxacin. Ciprofloxacin MICs for three isolates (8.1%) were 2.0 micrograms/ml; these isolates belonged to the auxotype/serovar class Pro/IB-7 and possessed the 3.2-MDa beta-lactamase and the 24.5-MDa conjugative plasmids. Six strains for which ciprofloxacin MICs were 0.06 to 0.125 microgram/ml belonged to a variety of gonococcal phenotypes. Strains for which ciprofloxacin MICs were 2.0 micrograms/ml were isolated from persons who had traveled to, or were sexual contacts of persons who had recently traveled to, Southeast Asia. Persons infected with these isolates had been treated with ceftriaxone (250 mg intramuscularly, single dose); therefore, none of these cases were associated with clinical failure following the use of fluoroquinolone therapy. Further studies are needed to confirm the clinical and public health significance of increased in vitro resistance to ciprofloxacin and ofloxacin in N. gonorrhoeae.
In vitro activity of dirithromycin against Chlamydia trachomatis
Authors: Segreti J , Kapell K S
Published: June 2012

Dirithromycin is a new macrolide antibiotic with an active metabolite, erythromycylamine. We evaluated the in vitro activities of both drugs against 16 isolates of Chlamydia trachomatis and compared them with that of doxycycline. In vitro susceptibility testing was performed with McCoy cell monolayers. The MIC was defined as the lowest concentration of antibiotic without inclusions. The MBC was defined as the lowest concentration of antibiotic yielding no inclusions after passage onto 24-h-old antibiotic-free McCoy cell monolayers. Dirithromycin and erythromycylamine appeared to be equally effective against these 16 strains of C. trachomatis (MIC for 90% of strains tested, 1 mg/ml; MBC for 90% of strains tested, 2 micrograms/ml). Both were less active than doxycycline (MIC for 90% of strains tested, 0.06 micrograms/ml; MBC for 90% of strains tested, 0.12 micrograms/ml). The combination of dirithromycin and erythromycylamine appeared to be additive.
N,N-dimethylglycyl-amido derivative of minocycline and 6-demethyl-6-desoxytetracycline, two new glycylcyclines highly effective against tetracycline-resistant gram-positive cocci
Authors: Goldstein F W , Kitzis M D , Acar J F
Published: June 2012

The in vitro activities of the N,N-dimethylglycyl-amino derivative of minocycline (DMG-MINO) and 6-dimethyl-6-dexoxytetracycline (DMG-DMDOT), members of a new generation of tetracyclines, were evaluated by an agar dilution method and were compared with those of tetracycline and minocycline against 224 tetracycline-resistant and 73 tetracycline-susceptible recent clinical isolates of gram-positive cocci, including multiple-antibiotic-resistant methicillin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae. The MICs of DMG-MINO and DMG-DMDOT were up to 500- to 2,000-fold lower than those of tetracycline against methicillin-resistant S. aureus and Streptococcus pneumoniae (MIC for 50% of strains tested [MIC50], < 0.06 microgram/ml). Against Streptococcus groups A, B, C, and G and Enterococcus faecalis, the MIC50 was 0.5 microgram/ml. MIC50s were greater only for coagulase-negative staphylococci (2 micrograms/ml). These data indicate that DMG-MINO and DMG-DMDOT are very potent drugs, and further in vitro and in vivo studies are warranted.
Penetration of cefotetan into suction skin blister fluid and tissue homogenates in patients undergoing abdominal surgery
Authors: Mazzei T , Tonelli F , Novelli A , Ficari F , Mazzoni C , Anastasi A , Periti P
Published: June 2012

The penetration of cefotetan (2-g intravenous bolus) into the suction blister fluid and tissue homogenates of 11 patients was investigated. Mean concentrations in tissue were significantly lower than contemporary suction blister fluid levels. These data show that the determination of beta-lactam concentrations by the tissue homogenate method may seriously underestimate the actual antibiotic levels in extracellular fluid.
Point mutations in Staphylococcus aureus PBP 2 gene affect penicillin-binding kinetics and are associated with resistance
Authors: Hackbarth C J , Kocagoz T , Kocagoz S , Chambers H F
Published: June 2012

In Staphylococcus aureus, penicillin-binding protein 2 (PBP 2) has been implicated in non-PBP 2a-mediated methicillin resistance. The PBP 2 gene (pbpB) was cloned from an expression library of a methicillin-susceptible strain of S. aureus (209P), and its entire sequence was compared with that of the pbpB gene from strains BB255, BB255R, and CDC6. Point mutations that resulted in amino acid substitutions near the conserved penicillin-binding motifs were detected in BB255R and CDC6, two low-level methicillin-resistant strains. Penicillin binding to PBP 2 in both BB255R and CDC6 is altered, and kinetic analysis indicated that altered binding of PBP 2 by penicillin was due to both lower binding affinity and more rapid release of bound drug. These structural and biochemical changes may contribute to the strains' resistance to beta-lactam antibiotics.
Sequence identity with type VIII and association with IS176 of type IIIc dihydrofolate reductase from Shigella sonnei
Authors: Barg N L , Register S , Thomson C , Amyes S
Published: June 2012

An uncommon dihydrofolate reductase (DHFR), type IIIc, was coded for by Shigella sonnei that harbors plasmid pBH700 and that was isolated in North Carolina. The trimethoprim resistance gene carried on pBH700 was subcloned and sequenced. The nucleotide sequence of the gene encoding type IIIc DHFR was identical to the gene encoding type VIII DHFR. The type IIIc amino acid sequence was approximately 50% similar to those of DHFRs commonly found in enteric bacteria. Furthermore, this gene was flanked by IS176 (IS26), an insertion sequence usually associated with those of aminoglycoside resistance genes. The gene for type IIIc DHFR was located by hybridization within a 1,993-bp PstI fragment in each of eight conjugative plasmids from geographically diverse strains of S. sonnei. Each plasmid also conferred resistance to ampicillin, streptomycin, and sulfamethoxazole and belonged to incompatibility group M. Plasmids carrying this new trimethoprim resistance gene, which is uniquely associated with IS176, have disseminated throughout the United States.
Effects of macro- and microcirculatory functions on ceftriaxone concentrations in tissues of patients with stage IV peripheral arterial occlusive disease
Authors: Hirschl M , Kundi M , Hirschl A M , Georgopoulos A
Published: June 2012

The objective of the study was to determine the ceftriaxone levels achievable within lesions (toe or forefoot area) in patients with septic gangrene and to investigate the relationship between macro- and microcirculatory parameters and antibiotic concentration. Fifteen patients with severe chronic peripheral occlusive disease received an intravenous injection of 2 g of ceftriaxone. Antibiotic levels in venous and capillary blood and in an exudative part of the lesion were measured. Macrocirculatory functions were assessed by Doppler sonography, plethysmography, and angiography; microcirculatory functions were assessed by quantitative capillaroscopy and fluorescence video microscopy. The mean antibiotic concentrations measured between 4 and 8 h after injection were 92 +/- 26 micrograms/ml in venous blood and 84 +/- 46 micrograms/ml in capillary blood. The concentration in tissue reached its maximum 4 h after injection; the average concentration at between 2 and 8 h was 95 +/- 55 micrograms/ml. Only dynamic capillary parameters showed significant (P < 0.01) correlations to antibiotic levels in tissue. Significantly (P < 0.01) higher levels in tissue were observed in patients with adequate microcirculatory functions (138 +/- 48 micrograms/ml) than in patients with poor microcirculatory function (51 +/- 26 micrograms/ml). Microcirculatory dysfunction appears to be the limiting factor for tissue antibiotic levels. However, even those patients with poor microcirculatory function showed tissue antibiotic levels that were above the MICs for the pathogens most frequently isolated from gangrenous lesions. Therefore, intravenous application was found to be adequate and additional measures such as intra-arterial therapy or Bier's occlusion are basically unnecessary. Our finding that microcirculatory function is the limiting factor for the tissue antibiotic concentration is corroborated by computations based on a three-compartment model.