bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro and in vivo ciprofloxacin pharmacokinetics in human neutrophils
Authors: Garraffo R , Jambou D , Chichmanian R M , Ravoire S , Lapalus P
Published: June 2012

Early in vitro investigations have shown that ciprofloxacin is concentrated within human neutrophils (polymorphonuclear leukocytes [PMNs]) at between 3 and 11 times the extracellular concentration. The elution of ciprofloxacin from cells is relatively rapid when the extracellular concentration is reduced. In order to estimate the in vivo intracellular penetration of ciprofloxacin and to determine its intracellular pharmacokinetics, PMNs were recovered from blood samples drawn from healthy volunteers at different times during a 24-h period after they were given a 750-mg oral dose. High-performance liquid chromatographic determination of ciprofloxacin in serum and cells showed that the intracellular/serum ratio was 3.7 at 1.5 h (maximum concentration of drug in serum), 5.7 at 12 h, and 20 at 24 h. The area under the curve ratio was 3.73. The mean elimination half-lives of ciprofloxacin were 3.7 and 6.2 h in serum and PMNs, respectively. These data show that in vivo findings are in agreement with in vitro findings. The large uptake of ciprofloxacin by PMNs combined with a prolonged intracellular half-life described under the conditions of human therapy should provide the basis for the use of ciprofloxacin in infections caused by susceptible intracellular bacteria.
Inhibitory effects of ciprofloxacin and sparfloxacin on DNA gyrase purified from fluoroquinolone-resistant strains of methicillin-resistant Staphylococcus aureus
Authors: Okuda J , Okamoto S , Takahata M , Nishino T
Published: June 2012

The activities of new quinolones against 140 strains of methicillin-resistant Staphylococcus aureus were determined. From the relationship between the MICs of sparfloxacin and ciprofloxacin, fluoroquinolone-resistant S. aureus 6171 (MIC of sparfloxacin, 200 micrograms/ml; MIC of ciprofloxacin, 100 micrograms/ml) and fluoroquinolone-susceptible S. aureus FDA 209-P were selected for purification of the subunit A and B proteins of their DNA gyrases. The supercoiling activities of reconstituted ArBr (r, resistant) (from strain 6171) and ArBs (s, susceptible) gyrases were 40-fold more resistant to new quinolones than those of AsBs from FDA 209-P and AsBr gyrases. The 50% inhibitory doses of ciprofloxacin and sparfloxacin for AmBm (from mutant 19) and AmBs (m, moderately resistant) gyrases were 15- to 27-fold higher than those for AsBs and AsBm gyrases. These findings indicate that one of the resistance mechanisms of S. aureus against fluoroquinolones is a modification of the gyrase subunit A protein.
Development of resistance in candida isolates from patients receiving prolonged antifungal therapy
Authors: Fan-Havard P , Capano D , Smith S M , Mangia A , Eng R H
Published: June 2012

The impact of prolonged antifungal therapy on the development of resistance was examined in 61 patients with oropharyngeal thrush. Fifty-nine patients had symptomatic human immunodeficiency virus infection, one had lung cancer, and one had metastatic prostate cancer. Cultures of pharyngeal samples from all patients were positive for yeasts and included 57 (93.4%) Candida albicans, 3 (4.9%) Candida glabrata, and 1 (1.6%) Candida krusii. Of 61 patients, 32 (52.5%) were receiving or had recently received antifungal therapy. Clotrimazole was the most commonly prescribed azole, followed by ketoconazole and fluconazole. Two patients had received amphotericin B therapy and one had received flucytosine. The duration of therapy with clotrimazole, ketoconazole, and fluconazole ranged from 3 to 240, 14 to 44, and 7 to 138 days, respectively. There was no overall difference in the susceptibilities of the clinical isolates from treated and untreated patients to amphotericin B, nystatin, flucytosine, clotrimazole, ketoconazole, and fluconazole. A.C. albicans isolate from one patient who had clinically failed on ketoconazole, fluconazole, and amphotericin B was resistant to these drugs. The lack of difference in the susceptibility pattern indicates that clinically significant emergence of resistance does not occur in those patients who receive prolonged antifungal therapy.
Molecular survey of clindamycin and tetracycline resistance determinants in Bacteroides species
Authors: Fletcher H M , Macrina F L
Published: June 2012

We have examined 13 clinical isolates of the intestinal Bacteroides group using DNA probes representing Bacteroides macrolide-lincosamide-streptogramin B (MLS) (ermF) and tetracycline resistance (tetQ) determinants as well as an insertion sequence (IS4351) previously seen in association with erm genes. tetQ-hybridizing sequences were detected in 11 of 13 tetracycline-resistant clinical isolates. On the other hand, ermF-like sequences were detected in only three of eight clindamycin-resistant strains. One isolate displayed low-level, inducible resistance to clindamycin and was sensitive to erythromycin. This same isolate had IS4351-like sequences but was missing ermF-like sequences, in contrast to previous reports which demonstrated the common association of IS4351 and erm genes. Our results suggest the occurrence of unclassified MLS genes in the Bacteroides group and furthermore suggest that IS4351-like sequences are not always linked to Bacteroides ermF-like sequences. Finally, 4 of 13 isolates conjugally transferred tetracycline resistance or linked tetracycline-clindamycin (MLS) resistances, but this process did not involve plasmids.
Inhibitory effects of recombinant human cystatin C on human coronaviruses
Authors: Collins A R , Grubb A
Published: June 2012

Cystatin C, a potent inhibitor of cysteine proteases such as papain and cathepsin B, was examined for its effect on human coronaviruses OC43 and 229e. Both viruses were greater than 99% inhibited by 0.1 mM inhibitor. Endpoint titrations showed that inhibiting activity paralleled that of leupeptin, a serine and cysteine protease inhibitor, and indicated that 1 to 2 microM inhibitor, slightly above physiologic levels, was effective.
Protection of Pseudomonas aeruginosa against ciprofloxacin and beta-lactams by homologous alginate
Authors: Hodges N A , Gordon C A
Published: June 2012

Pseudomonas aeruginosa-derived alginate but no other neutral and negatively charged polysaccharides protected mucoid and nonmucoid strains of that organism against ciprofloxacin, gentamicin, ticarcillin, and ceftazidime. Data indicate that alginate has an intrinsic protective effect which is independent of diffusion, charge, or biofilm phenomena.
Tetracycline resistance in Moraxella (Branhamella) catarrhalis: demonstration of two clonal outbreaks by using pulsed-field gel electrophoresis
Authors: Roberts M C , Pang Y J , Spencer R C , Winstanley T G , Brown B A , Wallace R J
Published: June 2012

Two tetracycline-resistant (Tcr) Moraxella (Branhamella) catarrhalis strains from England were compared with two previously characterized Tcr Texas strains. Both pairs carried the Tet B determinant, which was nontransferable. Pulsed-field gel electrophoresis of their genomic DNA restriction fragments demonstrated that the strains from the same area were identical (clonal); however, the Texas and English strains differed from each other.
Inactivation of enveloped viruses by anthraquinones extracted from plants
Authors: Sydiskis R J , Owen D G , Lohr J L , Rosler K H , Blomster R N
Published: June 2012

To determine the extent of antiviral activity present in a number of plant extracts, hot glycerin extracts were prepared from Rheum officinale, Aloe barbadensis, Rhamnus frangula, Rhamnus purshianus, and Cassia angustifolia and their virucidal effects were tested against herpes simplex virus type 1. All the plant extracts inactivated the virus. The active components in these plants were separated by thin-layer chromatography and identified as anthraquinones. A purified sample of aloe emodin was prepared from aloin, and its effects on the infectivity of herpes simplex virus type 1 and type 2, varicella-zoster virus, pseudorabies virus, influenza virus, adenovirus, and rhinovirus were tested by mixing virus with dilutions of aloe emodin for 15 min at 37 degrees C, immediately diluting the sample, and assaying the amount of infectious virus remaining in the sample. The results showed that aloe emodin inactivated all of the viruses tested except adenovirus and rhinovirus. Electron microscopic examination of anthraquinone-treated herpes simplex virus demonstrated that the envelopes were partially disrupted. These results show that anthraquinones extracted from a variety of plants are directly virucidal to enveloped viruses.
High-pressure liquid chromatography and microbiological assay of serum ofloxacin levels in adults receiving intravenous and oral therapy for skin infections
Authors: Auten G M , Preheim L C , Sookpranee M , Bittner M J , Sookpranee T , Vibhagool A
Published: June 2012

Thirty-two adults hospitalized with skin and skin structure infections received intravenous ofloxacin followed by oral ofloxacin. The standard treatment was 400 mg every 12 h. One patient with renal failure received 400 mg every 24 h. Serum ofloxacin levels were measured (1.5 h postdose and 1 h predose) during intravenous (32 patients) and oral (30 patients) therapy. Levels were assayed by high-pressure liquid chromatography (HPLC) and microbiological assay (MBA). Mean levels +/- standard deviation (in micrograms per milliliter) when measured by MBA after intravenous dosing were (postdose versus predose) 6.23 +/- 2.49 versus 2.42 +/- 1.56, and those after oral dosing were 6.17 +/- 3.25 versus 3.49 +/- 2.77. When measured by HPLC, mean levels +/- standard deviation after intravenous dosing were 5.81 +/- 2.08 versus 2.14 +/- 1.26 and those after oral dosing were 5.63 +/- 2.92 versus 3.41 +/- 2.98. There were no significant differences between levels achieved with oral or intravenous dosing when measured by either MBA or HPLC. Levels in serum did not correlate with side effects. The MICs for 50 and 90% of the 40 aerobic pathogens isolated from 21 patients were 0.5 and 2.0 micrograms/ml, respectively. Cure or improvement was achieved in 30 patients. Intravenous and oral administration of ofloxacin yielded similar levels in serum which were safe and effective in the therapy of skin infections in adult patients.
Penetration of cefotaxime and desacetylcefotaxime into brain abscesses in humans
Authors: Sjölin J , Eriksson N , Arneborn P , Cars O
Published: June 2012

Since clinical trials comparing the efficacies of different antibiotic regimens for treatment of brain abscesses are difficult to perform, the choice of antibiotics must rely on the antibacterial spectrum and the ability of the drug to penetrate into the abscess fluid. The aim of this investigation was to study the ability of cefotaxime and its active metabolite desacetylcefotaxime to penetrate into brain abscesses. Eight patients were given 3 g of cefotaxime intravenously every 8 h. Abscess fluid samples, obtained at surgery at various times after dosing, and blood samples were analyzed for their concentrations of cefotaxime and desacetylcefotaxime by using a newly developed microbiological assay. The brain abscess concentrations of cefotaxime and desacetylcefotaxime were 1.9 +/- 1.7 and 4.0 +/- 2.2 mg/liter, respectively. Simultaneous concentrations in plasma were 2.0 +/- 1.0 and 3.9 +/- 1.8 mg/liter, respectively. With increasing time following cefotaxime dosing there was a significant increase in the abscess:plasma concentration ratio of desacetylcefotaxime. Since both cefotaxime and desacetylcefotaxime penetrate well into the brain abscess, reaching concentrations above the MIC for probable bacteria except gram-negative anaerobes, it is concluded that cefotaxime in combination with metronidazole may be used as an alternative in the treatment of brain abscesses.
The ability of suramin to block CD4-gp120 binding is reversed in the presence of albumin
Authors: Yao X J , Wainberg M A , Richard M , Pollak M
Published: June 2012

We have shown that suramin can directly inhibit the binding of the human immunodeficiency virus type 1 gp120 envelope protein to immobilized CD4, thus helping to explain the previously described antiviral properties of suramin. However, physiological concentrations of serum albumin significantly attenuated suramin's antiviral effects, suggesting that only free suramin has antiviral properties. Reported discrepancies between in vitro and clinical activities of suramin may be due to differences between free suramin levels in experimental assays and those achievable clinically.
Remarkable in vitro and in vivo activities of the hydroxynaphthoquinone 566C80 against tachyzoites and tissue cysts of Toxoplasma gondii
Authors: Araujo F G , Huskinson J , Remington J S
Published: June 2012

Compound 566C80, 2-[trans-4-(4-chlorophenyl)cyclohexyl]-3-hydroxy-1,4-naphthoquinone, was studied for its in vitro and in vivo activities against Toxoplasma gondii. Replication within human foreskin fibroblasts of tachyzoites of seven different strains, five of them isolated from AIDS patients, was inhibited by concentrations as low as 4.8 x 10(-9) M. In vivo, a dose of 100 mg/kg of body weight per day, administered by gavage for 10 days, protected 100% of mice against death due to infection with five different strains of T. gondii, including the highly virulent RH strain. A dose of 50 mg/kg/day protected at least 80% of mice infected with the same inoculum, and a dose as low as 9.3 mg/kg/day protected 40 to 60% of mice. Treatment with 50 mg/kg/day for 30 days completely eradicated parasites from mice infected with four of five strains of T. gondii. 566C80 was active in vitro against the cyst stage of T. gondii at concentrations of 50 to 100 micrograms/ml. In vivo activity against this form of T. gondii was examined in mice infected for 6 weeks with strain ME49 and then treated orally with 100 mg of 566C80 per kg per day for 8 weeks. Treated mice sacrificed at 2-week intervals revealed a steady decline in the numbers of cysts in their brains compared with untreated controls. In addition, mortality as well as clinical signs of brain infection was absent from treated mice, whereas control mice had a high mortality rate and showed clinical signs of central nervous system infection. These results reveal remarkable in vitro and in vivo activities of 566C80 against T. gondii.
Molecular characterization of the class II multiresistance transposable element Tn1403 from Pseudomonas aeruginosa
Authors: Vézina G , Levesque R C
Published: June 2012

Transposon Tn1403 is a 19.9-kb multiresistance class II transposable element originally found on the RPL11 plasmid from a clinical isolate of Pseudomonas aeruginosa. It encodes resistance to ampicillin (PSE-1 beta-lactamase), streptomycin and spectinomycin (aadA and aphC), and chloramphenicol (cat). It has structural homology with the tnpM and tnpI sequences of Tn21 and inverted repeats and res and tnpR sequences of Tn501, but it has no structural homology nor functional complementation with the resolvase gene of Tn21 or Tn3. Sequence analysis revealed long inverted repeats at each extremity of Tn1403 containing 38-bp inverted repeats that were 97.4% similar to those of Tn1721 and 5-bp direct repeats. Transposition assays showed a low frequency of transposition (3.5 x 10(-6)) compared with that of Tn3 (3.3 x 10(-3)) and no resolution of cointegrates.
Anti-human immunodeficiency virus synergism by zidovudine (3'-azidothymidine) and didanosine (dideoxyinosine) contrasts with their additive inhibition of normal human marrow progenitor cells
Authors: Dornsife R E , St Clair M H , Huang A T , Panella T J , Koszalka G W , Burns C L , Averett D R
Published: June 2012

The anti-human immunodeficiency virus (HIV) activity and hemopoietic toxicity of zidovudine (AZT) and didanosine (dideoxyinosine;ddI), alone and in combination, were assessed in a variety of cell types. AZT was more potent than ddI as an inhibitor of HIV in vitro. Synergistic inhibition of HIV by the combination of these agents was observed in MT4 cells, peripheral blood lymphocytes, and macrophages. Toxicity assessment in vitro by using progenitor (erythroid and granulocyte-macrophage) colony-forming assays with normal human bone marrow showed ddI to be less toxic than AZT. Addition of inhibitory concentrations of ddI to AZT resulted in additive inhibition of progenitor CFUs. These in vitro findings suggest that combinations of ddI and AZT at appropriately modified doses may provide an enhanced degree of selectivity in anti-HIV chemotherapy.
Endotoxin-tobramycin additive toxicity on renal proximal tubular cells in culture
Authors: Joly V , Bergeron Y , Bergeron M G , Carbon C
Published: June 2012

Aminoglycoside-induced renal damage is enhanced in animals with Escherichia coli pyelonephritis. Bacterial endotoxin is liberated during antibiotic therapy. The toxic effect of endotoxin and tobramycin, alone or in combination, was investigated in primary cultures of rabbit proximal tubular cells grown to confluence in serum-free medium. Sodium-dependent uptakes of Pi and alpha-methylglucopyranoside (MGP) and enzymatic activities (lactate dehydrogenase [LDH] released as a marker of cell necrosis and gamma-glutamyltransferase [GGT] and N-acetyl-beta-D-glucosaminidase [NAG] present in the homogenate as markers of brush border membrane and lysosome integrity) were measured. Cells were exposed to (i) endotoxin (20 mg/liter), tobramycin (1 mM), or endotoxin plus tobramycin for 48 h, or (ii) endotoxin (100 mg/liter), tobramycin (4 mM), or endotoxin plus tobramycin for 72 h. Endotoxin alone did not alter Pi uptake, but tobramycin inhibited Pi uptake through a decrease in Vmax. The effect was not enhanced by the combination of endotoxin and tobramycin. Endotoxin and tobramycin alone exerted no significant effect upon MGP uptake, but strong inhibition of the Vmax was observed after exposure to a combination of endotoxin plus tobramycin, without alteration of the Km. Endotoxin decreased residual GGT activity in the cell homogenate. Tobramycin increased LDH release in the medium and NAG activity in the homogenate. Endotoxin plus tobramycin resulted in an additive effect upon LDH and NAG activities. In conclusion, by disturbing apical membrane integrity, endotoxin increased tobramycin toxicity in vitro in the absence of serum hormonal mediator.
Fluconazole in the treatment of candidiasis in immunocompromised children
Authors: Viscoli C , Castagnola E , Fioredda F , Ciravegna B , Barigione G , Terragna A
Published: June 2012

Fluconazole, a new triazole derivative, was evaluated in a pilot study of 34 episodes of candidiasis in 24 children. All the patients had predisposing conditions, such as human immunodeficiency virus infection, cancer, organ or bone marrow transplantation, neonatal age and malnutrition, and obstructive uropathy. The drug was administered at 6 mg/kg (body weight) once daily either orally or intravenously. Two patients with fungemia due to Candida parapsilosis required an increased dosage of 12 mg/kg. Clinical and microbiological success was achieved in 30 of 34 cases (88%). Drug-related transaminase increases were observed in two cases (6%). Fluconazole may represent an effective alternative to amphotericin B in the treatment of candidiasis in children. Comparative trials are necessary to assess optimal dosages and efficacy.
Pseudomonas pseudomallei, a common pathogen in Thailand that is resistant to the bactericidal effects of many antibiotics
Authors: Sookpranee T , Sookpranee M , Mellencamp M A , Preheim L C
Published: June 2012

The purpose of this investigation was to identify newer antimicrobial agents that may be useful in the therapy of melioidosis. The in vitro susceptibilities of 199 clinical isolates of Pseudomonas pseudomallei to 22 antibiotics were determined by standard disk diffusion, and those to 13 antibiotics were determined by agar dilution. Over 90% of the isolates were susceptible to imipenem, piperacillin-tazobactam, piperacillin, ceftazidime, ticarcillin-clavulanate, ampicillin-sulbactam, and carumonam by both methods. Standard disk diffusion yielded unacceptably high false-susceptibility results with aztreonam, ciprofloxacin, and temafloxacin. Piperacillin, ceftazidime, imipenem, and ciprofloxacin were not bactericidal for three selected P. pseudomallei strains as determined by time-kill curve methods. Furthermore, addition of ciprofloxacin to piperacillin, ceftazidime, or imipenem did not enhance bactericidal activity. One hundred ninety-four strains showed weak beta-lactamase production that did not increase upon incubation with cefoxitin. These findings suggest that several newer antimicrobial agents may prove useful in the treatment of melioidosis. However, results of susceptibility studies involving P. pseudomallei and newer agents must be interpreted with caution.
In vitro antimycobacterial activities of newly synthesized benzoxazinorifamycins
Authors: Saito H , Tomioka H , Sato K , Emori M , Yamane T , Yamashita K , Hosoe K , Hidaka T
Published: June 2012

Newly synthesized rifamycin derivatives, KRM-1648, KRM-1657, KRM-1668, KRM-1686, and KRM-1687, having the chemical structures of 3'-hydroxy-5'-(4-alkylpiperazinyl)-benzoxazinorifamycins (alkyl residues: isobutyl, propyl, sec-butyl, sec-butyl [R configuration], and sec-butyl [S configuration], respectively), were studied for their in vitro antimycobacterial activities. Representative (KRM-1648) MICs for 90% of the strains tested, determined by the agar dilution method on 7H11 medium, of various pathogenic mycobacteria (9 species, 174 strains) were as follows (in micrograms per milliliter): Mycobacterium tuberculosis (rifampin [RMP]-susceptible strains), less than or equal to 0.0125; M. tuberculosis (RMP-resistant strains), 12.5; M. kansasii, 0.05; M. marinum, less than or equal to 0.0125; M. scrofulaceum, 0.1; M. avium, 1.56; M. intracellulare, 0.1; M. fortuitum, greater than 100; and M. chelonae subsp. abscessus and M. chelonae subsp. chelonae, greater than 100. These values are more than 64 times lower than those of RMP, except for the values against RMP-resistant M. tuberculosis (8 times lower) and those against rapid growers, including M. fortuitum and M. chelonae (the same as those of RMP). The other derivatives had similar levels of in vitro activity against these mycobacteria. When murine peritoneal macrophages in which M. intracellulare was phagocytosed in vitro were cultured in the presence of the benzoxazinorifamycins (1 microgram/ml), much more rapid killing of the organisms ingested in the macrophages was seen compared with when the same amount of RMP was added to the medium. The addition of benzoxazinorifamycins at the concentration of 0.05 micrograms/ml caused more marked suppression of intracellular growth of the organisms compared with addition of RMP. KRM-1648 and KRM-1657 inhibited intracellular growth of M. tuberculosis, and their efficacies were much greater than that of RMP.
Amphotericin B lipid complex therapy of experimental fungal infections in mice
Authors: Clark J M , Whitney R R , Olsen S J , George R J , Swerdel M R , Kunselman L , Bonner D P
Published: June 2012

The amphotericin B lipid complex (ABLC), which is composed of amphotericin B and the phospholipids dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol, was evaluated for its acute toxicity in mice and for its efficacy in mice infected with a variety of fungal pathogens. ABLC was markedly less toxic to mice when it was administered intravenously; it had a 50% lethal dose of greater than 40 mg/kg compared with a 50% lethal dose of 3 mg/kg for Fungizone, the desoxycholate form of amphotericin B. ABLC was efficacious against systemic infections in mice caused by Candida albicans, Candida species other than C. albicans, Cryptococcus neoformans, and Histoplasma capsulatum. ABLC was also efficacious in immunocompromised animals infected with C. albicans, Aspergillus fumigatus, and H. capsulatum. Against some infections, the efficacy of ABLC was comparable to that of Fungizone, while against other infections Fungizone was two- to fourfold more effective than ABLC. Against several infections. Fungizone could not be given at therapeutic levels because of intravenous toxicity. ABLC, with its reduced toxicity, could be administered at drug levels capable of giving a therapeutic response. ABLC should be of value in the treatment of severe fungal infections in humans.
Pharmacodynamic parameters and toxicity of netilmicin (6 milligrams/kilogram/day) given once daily or in three divided doses to cancer patients with urinary tract infection
Authors: Van der Auwera P , Meunier F , Ibrahim S , Kaufman L , Derde M P , Tulkens P M
Published: June 2012

The pharmacologic parameters and toxicity of netilmicin (6 mg/kg/day) given once daily (qd) or thrice daily (tid) for the treatment of urinary tract infections were studied in a randomized prospective study of 60 cancer patients. The overall efficacy was 96%. Nephrotoxicity, assessed by the measure of urinary excretion of phospholipids, was lower for the patients receiving the qd regimen than for those receiving the tid regimen. Elevation of serum creatinine (20% over baseline) occurred in one patient receiving the qd regimen and in three receiving the tid regimen. Cochleotoxicity, assessed by pure-tone audiometry (250 to 18,000 Hz) occurred in one patient receiving the qd regimen and none receiving the tid regimen. Concentrations in sera were measured on days 1 and 5. No significant accumulation was observed in either group. Median serum bactericidal titers, expressed as reciprocal values (percentage of the sera with a titer greater than or equal to 8), were measured against 25 test organisms in samples collected 6 h after the administration of netilmicin and were, for the qd group, 16 (82%) against members of the family Enterobacteriaceae and less than 2 (8%) against Pseudomonas aeruginosa, and for the tid group, 4 (57%) against members of the Enterobacteriaceae and less than 2 (0%) against P. aeruginosa. The rate of killing in serum was rapid (2 to 3 log in 2 h against P. aeruginosa; 3 to 5 log in 2 h against members of the Enterobacteriaceae) and correlated with the sampling time and hence the concentration in serum of netilmicin. The duration of the postantibiotic effect in serum depended also on the strain and the sampling time of the serum.
Characterization of a beta-lactamase found in Eikenella corrodens
Authors: Lacroix J M , Walker C
Published: June 2012

Eleven strains of Eikenella corrodens with beta-lactamase activity were isolated from a patient with refractory periodontitis who had previously been treated with penicillin antibiotics. These strains were relatively resistant to benzylpenicillin, amoxicillin, and ampicillin (MICs, greater than or equal to 64 micrograms/ml); susceptible to amoxicillin-clavulanate (2:1) (MICs, less than or equal to 4 micrograms/ml); and moderately susceptible to cephalothin and cephaloridine (MICs, 0.12 to 16 micrograms/ml). The addition of 1 microgram of potassium clavulanate, a beta-lactamase inhibitor, per ml resulted in a significant increase in the susceptibilities of these strains to penicillins but not to cephalosporins. Potassium clavulanate had no effect on non-beta-lactamase-producing strains. Enzyme production was constitutive since activity was not increased when cells were cultivated in the presence of benzylpenicillin. Enzyme activity was strongly inhibited by potassium clavulanate, sulbactam, and iodine; weakly inhibited by cloxacillin, imipenem, and moxalactam; but not inhibited by aztreonam, EDTA, or p-chloromercuribenzoate. By gel infiltration, the enzyme had an estimated molecular mass of 29 kDa. Isoelectric focusing of the partially purified enzyme gave a major beta-lactamase band at pH 5.50 and a minor band at pH 5.60. Plasmids were not detected in any of the 11 beta-lactamase-positive strains. This enzyme is considered to belong to class 2a of the Bush classification scheme.
Association of two resistance mechanisms in a clinical isolate of Enterobacter cloacae with high-level resistance to imipenem
Authors: Lee E H , Nicolas M H , Kitzis M D , Pialoux G , Collatz E , Gutmann L
Published: June 2012

Carbapenem resistance was studied in a clinical isolate of Enterobacter cloacae, strain 201 (MIC of imipenem and meropenem, 16 micrograms/ml). This strain was analyzed comparatively with the carbapenem-susceptible parent strain 200, an equally susceptible revertant, 201-Rev, and in vitro-selected mutants with different levels of carbapenem resistance. All strains produced similarly high amounts of the same cephalosporinase (pIapp = 8.8). Strain 201 apparently lacked two major outer membrane proteins of ca. 37 and 38 kDa, while 201-Rev produced only the 37-kDa protein. The permeability coefficient, determined with cephaloridine, was reduced up to ninefold in the resistant strains which also showed a substantial reduction in the uptake of [14C]meropenem. The introduction of the plasmid-borne ampD gene (whose product decreases the expression of ampC) resulted in almost complete cessation of cephalosporinase production in all strains and a substantial decrease in the MICs of the carbapenems which remained, however, 8- to 16-fold higher than those determined for the susceptible strains containing the ampD gene. This "residual" resistance was attributed to reduced outer membrane permeability. The contribution of cephalosporinase production was verified in a reverse experiment, in which the introduction of ampC into a low-level cephalosporinase producer resulted in a fourfold increase in the carbapenem MICs. From these results, we infer that reduced outer membrane permeability and high-level cephalosporinase production can operate in conjunction in clinical isolates of E. cloacae to confer imipenem resistance.
In vitro and in vivo evaluation of tiacumicins B and C against Clostridium difficile
Authors: Swanson R N , Hardy D J , Shipkowitz N L , Hanson C W , Ramer N C , Fernandes P B , Clement J J
Published: June 2012

Tiacumicins B and C are members of a novel group of 18-membered macrolide antibiotics with in vitro activity against Clostridium difficile. The MICs against 15 strains of C. difficile were 0.12 to 0.25 microgram/ml for tiacumicin B, 0.25 to 1 microgram/ml for tiacumicin C, and 0.5 to 1 microgram/ml for vancomycin. The resistance frequency for both compounds against C. difficile was less than 2.8 x 10(-8) at four and eight times the MIC. The in vivo activities of the tiacumicins against two strains of C. difficile were compared with that of vancomycin in a hamster model of antibiotic-associated colitis. Oral therapy with 0.2, 1, or 5 mg of tiacumicin B or C per kg of body weight protected 100% of clindamycin-treated hamsters exposed to C. difficile ATCC 9689. Oral treatment with identical doses of vancomycin produced a prolonged, dose-dependent survival of hamsters, but it did not prevent the development of fatal colitis at doses of up to 5 mg/kg. When clindamycin-treated animals were exposed to another strain of C. difficile, both tiacumicin B and vancomycin were protective at 5 mg/kg, but not at lower doses. Tiacumicin C was not tested in vivo against the second strain of C. difficile. No tiacumicin B or C was detected in the sera of hamsters treated with single oral doses of 25 mg/kg, while antibiotic levels in the ceca of these hamsters reached 248 micrograms/ml and 285 mg/ml for tiacumicins B and C, respectively. The tiacumicins demonstrated in vitro and in vivo potencies against C. difficile and achieved high concentrations in the cecum, but not the serum, of hamsters after oral administration.
Comparison of the effects of the new azalide antibiotic, azithromycin, and erythromycin estolate on rat liver cytochrome P-450
Authors: Amacher D E , Schomaker S J , Retsema J A
Published: June 2012

Erythromycin and some other macrolide antibiotics can first induce a cytochrome P-450 isozyme similar to the one induced in rats by pregnenolone-16 alpha-carbonitrile and then inhibit it by forming a stable cytochrome P-450-metabolite complex. The purpose of this study was to compare azithromycin, a novel 15-membered ring azalide, and erythromycin estolate for the potential to cause hepatic microsomal enzyme induction and inhibition in Sprague-Dawley rats. The daily oral administration of 800 mg of erythromycin estolate per kg for 7 days resulted in statistically significant elevations of NADPH-cytochrome c reductase, erythromycin N-demethylase (3.2-fold), and total cytochrome P-450 content. Approximately 40% of cytochrome P-450 was complexed with erythromycin metabolite. In contrast, the daily administration of 200 mg of azithromycin per kg for 7 days caused significant elevations of N-demethylase (2.5-fold) only and did not produce any increases in total cytochrome P-450 content or NADPH-cytochrome c reductase. No complexed cytochrome P-450 was detected in the azithromycin-dosed rats despite liver concentrations of azithromycin that were 118 times greater than the liver concentrations of erythromycin estolate in erythromycin estolate-dosed rats. Although the short-term oral administration of azithromycin produced hepatic accumulation of the drug and elevated azithromycin demethylase activity, there was no other evidence of hepatic cytochrome P-450 induction or inactivation via cytochrome-metabolite complex formation. In contrast to erythromycin estolate, azithromycin is not expected to inhibit its own metabolism or that of other drugs via this pathway.
Mechanisms of interaction among subinhibitory concentrations of antibiotics, human polymorphonuclear neutrophils, and gram-negative bacilli
Authors: Mandell L A , Afnan M
Published: June 2012

Our hypothesis was that pretreatment of bacteria with subinhibitory concentrations (sub-MICs) of antibiotics enhances the susceptibility of the organisms to killing by human polymorphonuclear neutrophils (PMNs). Our purpose was to study a variety of drugs with different mechanisms of action and to determine whether the mechanism and locus of action altered the sub-MIC effect. The following outcome measures were used: ingestion and killing of bacteria by PMNs, bacterial killing in the absence of phagosome formation, and binding requirements of the bacteria to PMNs. The antibiotics used were representative of a variety of classes, including beta-lactams (piperacillin and imipenem) and quinolones (ciprofloxacin). Bacterial uptake and killing were measured by using standard techniques, and results were analyzed by using the analysis-of-variance technique and Dunnett's t test. Pretreatment of Escherichia coli with all drugs showed significantly enhanced killing of bacteria by PMNs, which was independent of ingestion by the phagocytes. Even in the absence of phagosome formation, statistically significant killing persisted with piperacillin-pretreated bacteria but not with imipenem- or ciprofloxacin-pretreated organisms. The opsonization experiments showed that contact between bacteria and PMNs was necessary for killing to occur. The sub-MIC effect appears to be independent of the locus or mechanism of action of the antibiotic. It results in enhanced killing by PMNs which is independent of ingestion and also may persist even in the absence of phagosome formation. Killing is dependent upon specific contact between bacteria and an intact phagocyte.
Cefonicid versus clindamycin prophylaxis for head and neck surgery in a randomized, double-blind trial, with pharmacokinetic implications
Authors: Swanson D , Maxwell R A , Johnson J T , Wagner R L , Yu V L
Published: June 2012

Perioperative single-dose antibiotic prophylaxis of cefonicid was compared with clindamycin in a prospective, randomized, double-blind trial of patients undergoing oncologic head and neck surgery. Antibiotics were administered intravenously beginning 1 to 2 h preoperatively. Cefonicid, 1 g, was given as a single dose. Clindamycin, 600 mg, was administered every 8 h for a total of four doses. Blood and wound drainage samples were collected for 24 h following the dose of cefonicid and assayed for total and free cefonicid concentrations, using reverse-phase high-performance liquid chromatography. Although total concentrations of cefonicid in both serum and wound drainage exceeded the MIC for 90% of the isolates of common bacterial pathogens for 24 h, free concentrations in serum and wound drainage (11.0 and 14.9% of total concentrations) were subinhibitory within 6 h following administration. Free concentrations of cefonicid in the postoperative wound drainage were subinhibitory for the entire study period, both perioperatively and postoperatively. Postoperative wound infection occurred significantly (P less than 0.05) more frequently in patients receiving cefonicid (24%) as compared with those receiving clindamycin (8.2%). The relatively low free levels of cefonicid achieved in serum and wound drainage were attributed to the high degree of protein binding (89% in serum) and may be related to the poor clinical outcome.
Comparison of Enterococcus raffinosus with Enterococcus avium on the basis of penicillin susceptibility, penicillin-binding protein analysis, and high-level aminoglycoside resistance
Authors: Grayson M L , Eliopoulos G M , Wennersten C B , Ruoff K L , Klimm K , Sapico F L , Bayer A S , Moellering R C
Published: June 2012

We reidentified our laboratories' collections of 57 enterococcal isolates previously classified as Enterococcus avium by the API Rapid Strep identification system (Analytab Products, Plainview, N.Y.) with the identification criteria recommended by Facklam and Collins (R. R. Facklam and M. D. Collins, J. Clin. Microbiol. 27: 731-734, 1989). Thirty isolates were identified as true E. avium, 25 isolates were identified as E. raffinosus, and 2 isolates were identified as E. pseudoavium. E. raffinosus could be differentiated from E. avium on the basis of penicillin susceptibility, as follows: MIC for 50% of E. raffinosus isolates tested (MIC50), 32 micrograms/ml; MIC90, 64 micrograms/ml (range, 4 to 64 micrograms/ml); E. avium MIC50, 1 microgram/ml; MIC90, 2 micrograms/ml (range, 0.5 to 2 micrograms/ml). No strains produced detectable beta-lactamase. Penicillin-binding protein (PBP) analysis of all E. raffinosus isolates demonstrated the unique pattern reported previously (M. D. Collins, R. R. Facklam, J. A. E. Farrow, and R. Williamson, FEMS Microbiol. Lett. 57:283-288, 1989); however, a number of newly identified PBPs were noted. Of 25 isolates, 13 had an additional PBP of 77 kDa (designated PBP 6*), while all isolates possessed a 52-kDa PBP (PBP 7) and a 46-kDa PBP (PBP 8). The presence or absence of PBP 6* did not correlate with penicillin susceptibility; however, PBP 7 demonstrated many features suggestive of low penicillin-binding affinity and may represent a possible mechanism for the relative resistance of this species to penicillin, although this hypothesis remains speculative since attempts to develop a penicillin-hypersusceptible E. raffinosus mutant were unsuccessful. E. raffinosus isolates were significantly more likely to exhibit high-level resistance to kanamycin than E. avium strains were (P < 0.001; chi-square); however, no strains demonstrated high-level resistance to gentamicin. No trend toward increasing penicillin resistance was noted among this collection of E. avium and E. raffinosus isolates collected over the past 35 and 14 years, respectively. Relative resistance to penicillin may be a helpful differentiating feature between E. avium and E. raffinosus when assessment of raffinose metabolism is not possible or is indeterminant.
Evaluation of the hepatotoxic potential of minocycline
Authors: Böcker R , Estler C J , Ludewig-Sandig D
Published: June 2012

Minocycline (25 to 100 micrograms/g) dose dependently increased serum glutamic oxalacetic transaminase, urea, and bilirubin levels, and the hepatic triglyceride content in mice. In animals pretreated with phenobarbital to enhance minocycline metabolism, the effects on liver triglycerides were attenuated, while the changes in serum glutamic oxalacetic transaminase, urea, and bilirubin were enhanced. It is concluded that part of the toxic effects of minocycline may be produced by a metabolite of minocycline.
6-N-substituted derivatives of adenine arabinoside as selective inhibitors of varicella-zoster virus
Authors: Koszalka G W , Averett D R , Fyfe J A , Roberts G B , Spector T , Biron K , Krenitsky T A
Published: June 2012

A series of 6-alkylaminopurine arabinosides were synthesized and found to inhibit varicella-zoster virus (VZV). The antiviral activities of these nucleosides were limited to VZV. None of the other viruses tested in the herpesvirus family were affected. The in vitro antiviral potencies of the 18 arabinosides correlated with their efficiencies as substrates of the VZV-encoded thymidine kinase in all but one case. The arabinosides of 6-methylaminopurine and 6-dimethylaminopurine were the most potent analogs, with 50% inhibitory concentrations against VZV of 3 and 1 microM, respectively. They were not cytotoxic to uninfected MRC-5 cells, human Detroit 98 cells, or mouse L cells (50% inhibitory concentration, greater than 100 microM). Neither 6-methylaminopurine arabinoside nor 6-dimethylaminopurine arabinoside was detectably phosphorylated by either adenosine kinase or 2'-deoxycytidine kinase. These two alkylaminopurine arabinosides were also resistant to deamination catalyzed by adenosine deaminase. The VZV-dependent phosphorylation of these nucleosides offers the possibility of a potent and highly selective therapy for VZV infection.
Use of intravenous gamma globulin to passively immunize high-risk children against respiratory syncytial virus: safety and pharmacokinetics. The RSVIG Study Group
Authors: Groothuis J R , Levin M J , Rodriguez W , Hall C B , Long C E , Kim H W , Lauer B A , Hemming V G
Published: June 2012

Infants with cardiopulmonary disease develop severe illness from respiratory syncytial virus (RSV) infection. Safety, feasibility, and pharmacokinetics of intravenous gamma globulin (IVIG) to prevent RSV illness were studied in 23 high-risk infants in a phase I trial. IVIG with an RSV neutralizing antibody titer of 1:1,100 in 5% solution was given monthly over a 2- to 4-h period in a clinical setting during the RSV season. The first group (n = 7) received 500 mg/kg of body weight, the second group (n = 9) received 600 mg/kg, and the third group (n =7) received 750 mg/kg. Serum was drawn prior to infusion and 2, 14, and 30 days after infusion. Total immunoglobulin G and RSV A2 and RSV B neutralizing antibody levels were obtained after the first IVIG infusion. Two children developed mild reversible pulmonary edema (group receiving 600 mg/kg per dose), and one developed hives and wheezing during one infusion (group receiving 500 mg/kg per dose). Twelve children developed subsequent RSV infection during two RSV seasons (November to April) over a 2-year follow-up period; 9 of 12 developed infection during the infusion year. Eleven illnesses were mild; one child died of progressive RSV illness (group receiving 500 mg/kg per dose). A cumulative infusion effect was not observed. IVIG appears safe and feasible in an outpatient setting, and at 750 mg/kg per dose, a target RSV antibody level of greater than or equal to 1:100 was achieved.
Gentamicin pharmacokinetics in patients with malignancies
Authors: Bertino J S , Booker L A , Franck P , Rybicki B
Published: June 2012

The pharmacokinetics of gentamicin were investigated in 880 patients with leukemia (24 patients), other malignancies (211 patients), or no malignancies (645 patients) by using data collected by our Clinical Pharmacy Service. A significant difference was seen in the initial calculated creatinine clearance between the patients with leukemia and the other two groups. No differences in gentamicin pharmacokinetics were seen in patients with other malignancies versus those with no malignancies. Patients with leukemia had significantly faster drug clearance compared with those in the other two groups. A poor predictive value was found for total body clearance of gentamicin versus the initial calculated creatinine clearance in all groups. Multiple logistic regression analysis showed that only the initial calculated creatinine clearance differed in the leukemic group compared with those in the other patients. Our data suggest that no pharmacokinetic difference exists for gentamicin in patients with malignancies.
Analysis of genetic localization of the type I trimethoprim resistance gene from Escherichia coli isolated in Finland
Authors: Heikkilä E , Sundström L , Skurnik M , Huovinen P
Published: June 2012

Among a collection of clinical Escherichia coli isolates, the type I dihydrofolate reductase (DHFR) mediating trimethoprim resistance was generally observed to be chromosomally determined. Only a minority of isolates carried the type I DHFR gene simultaneously on a plasmid. The majority of E. coli isolates studied also hybridized with a probe specific for the transposition gene tnsC of transposon Tn7; and in most of these isolates, Tn7 was found to be inserted into a preferred site in the E. coli chromosome. A minority of isolates that harbored the type I DHFR gene in the chromosome lacked a complete Tn7. Some of these harbored the type I DHFR gene inserted in a structure similar to that containing the gene for streptomycin resistance in Tn21. In the other isolates that were negative for a complete Tn7, the sequences upstream of the type I DHFR gene were demonstrated to be homologous to those flanking the type I DHFR gene in Tn7. This could indicate that the antibiotic resistance region of Tn7 may occur independently of this transposon. In two isolates, no sequences resembling Tn7 or Tn21 were found adjacent to the type I DHFR gene.
Tetracycline resistance in Peptostreptococcus species
Authors: Roberts M C
Published: June 2012

Of 15 Peptostreptococcus sp. strains isolated between 1975 and 1984, 13 hybridized with the Tet K, Tet M, or Tet O determinant. A donor Peptostreptococcus anaerobius strain carrying the three determinants could transfer Tet M to P. anaerobius and Fusobacterium nucleatum recipients but not to an Enterococcus faecalis recipient, while neither Tet K nor Tet O was transferred.
Cloning and nucleotide base sequence analysis of a spectinomycin adenyltransferase AAD(9) determinant from Enterococcus faecalis
Authors: LeBlanc D J , Lee L N , Inamine J M
Published: June 2012

Enterococcus faecalis LDR55, a human clinical isolate, is resistant to tetracycline (Tcr), erythromycin (Emr), and high levels (greater than 2,000 micrograms/ml) of spectinomycin (Spr) but not streptomycin. Filter matings between strain LDR55 and E. faecalis OG1-RF produced transconjugants with the following resistance phenotypes: Tcr Emr Spr, Tcr Emr, Tcr Spr, and Tcr only but never Emr or Spr only. The genetic determinant encoding resistance to spectinomycin was cloned in Streptococcus sanguis Challis from pDL55, a 26-kb plasmid harbored by a Tcr Spr transconjugant. Subcloning experiments yielded a 1.1-kb ClaI-NdeI fragment that encoded very high-level Spr in S. sanguis (10 mg/ml) and Escherichia coli (50 mg/ml). Cell extracts of cultures obtained from Spr strains expressed adenylating activity for spectinomycin but not for streptomycin, indicating that Spr was due to an AAD(9) activity. The nucleotide base sequence of the 1.1-kb ClaI-NdeI fragment contained a single 750-base open reading frame. The protein predicted from the open reading frame consisted of 250 amino acids and had a calculated size of approximately 28,000 daltons, similar to the size estimated from maxicell analysis (29,000 daltons). The deduced amino acid sequence of the streptococcal AAD(9) was compared with that of the AAD(9) encoded by staphylococcal transposon Tn554. The two proteins shared approximately 39% amino acid identity, which was expanded to 53% when conservative amino acid changes were included. When the streptococcal protein was compared with an AAD(3")(9) protein of E. coli, the degrees of identity were 27 and 47%, on the basis of actual amino acids and conservative replacements, respectively. The cloning and nucleotide base sequence analyses of the spectinomycin AAD(9) determinant from E. faecalis that results in high-level Spr when transferred to S. sanguis or E. coli are presented.