bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of two penicillins plus beta-lactamase inhibitors versus cefotaxime in treatment of murine Klebsiella pneumoniae infections
Authors: Fournier J L , Ramisse F , Jacolot A C , Szatanik M , Petitjean O J , Alonso J M , Scavizzi M R
Published: October 2018

The in vivo efficacies of piperacillin, piperacillin plus tazobactam, ticarcillin, ticarcillin plus clavulanic acid, piperacillin plus clavulanic acid, and cefotaxime were compared in a mouse model of pneumonia induced by the SHV-1 beta-lactamase-producer Klebsiella pneumoniae. Each antibiotic was injected either once intraperitoneally at 24 h postinfection or at repeated times during 24 h. The efficacies of the drugs and therapeutic protocols were assessed by counting viable bacteria recovered from the lungs of mice sacrificed at selected times. No emergence of beta-lactam-resistant organisms was detected. Ticarcillin at 300 mg/kg was ineffective. Repeated injections of piperacillin at 300 mg/kg, either alone or in combination with tazobactam (8:1), led to a significant decrease in bacterial counts, but this was followed by bacterial regrowth. The pharmacokinetic analysis demonstrated that this short-lasting antibacterial effect was not due to a failure of piperacillin and/or tazobactam to penetrate the lungs. The combinations of ticarcillin at 300 mg/kg plus clavulanic acid (15:1) and piperacillin at 300 mg/kg plus tazobactam (4:1) were proven to be effective in that they decreased the bacterial burden in the lungs from 10(5) to < 10(3) CFU. This dose effect of tazobactam can be explained by its dose-dependent penetration in the lungs. Cefotaxime at 100 mg/kg and the combination of piperacillin (slightly hydrolyzed by SHV-1) at 300 mg/kg plus clavulanic acid (15:1) led to the best efficacy. Both of these treatments induced a decrease in bacterial counts of nearly 4 log10 units. The survival rates correlated with the quantitative measurements of in vivo bacterial killing. These experimental results obtained from the restricted animal model used here may help in the design of further protocols for clinical trials.
Multifocal outbreaks of metallo-beta-lactamase-producing Pseudomonas aeruginosa resistant to broad-spectrum beta-lactams, including carbapenems
Authors: Senda K , Arakawa Y , Nakashima K , Ito H , Ichiyama S , Shimokata K , Kato N , Ohta M
Published: October 2018

A total of 3,700 Pseudomonas aeruginosa isolates were collected from 17 general hospitals in Japan from 1992 to 1994. Of these isolates, 132 carbapenem-resistant strains were subjected to DNA hybridization analysis with the metallo-beta-lactamase gene (blaIMP)-specific probe. Fifteen strains carrying the metallo-beta-lactamase gene were identified in five hospitals in different geographical areas. Three strains of P. aeruginosa demonstrated high-level imipenem resistance (MIC, > or = 128 micrograms/ml), two strains exhibited low-level imipenem resistance (MIC, < or = 4 micrograms/ml), and the rest of the strains were in between. These results revealed that the acquisition of a metallo-beta-lactamase gene alone does not necessarily confer elevated resistance to carbapenems. In several strains, the metallo-beta-lactamase gene was carried by large plasmids, and carbapenem resistance was transferred from P. aeruginosa to Escherichia coli by electroporation in association with the acquisition of the large plasmid. Southern hybridization analysis and genomic DNA fingerprinting profiles revealed different genetic backgrounds for these 15 isolates, although considerable similarity was observed for the strains isolated from the same hospital. These findings suggest that the metallo-beta-lactamase-producing P. aeruginosa strains are not confined to a unique clonal lineage but proliferated multifocally by plasmid-mediated dissemination of the metallo-beta-lactamase gene in strains of different genetic backgrounds. Thus, further proliferation of metallo-beta-lactamase-producing strains with resistance to various beta-lactams may well be inevitable in the future, which emphasizes the need for early recognition of metallo-beta-lactamase-producing strains, rigorous infection control, and restricted clinical use of broad-spectrum beta-lactams including carbapenems.
Luciferase in vivo expression technology: use of recombinant mycobacterial reporter strains to evaluate antimycobacterial activity in mice
Authors: Hickey M J , Arain T M , Shawar R M , Humble D J , Langhorne M H , Morgenroth J N , Stover C K
Published: October 2018

The development of new drugs and vaccines directed against Mycobacterium tuberculosis is severely impeded by the slow growth of this organism and the need to work under stringent biosafety conditions. These difficulties pose considerable obstacles when animal studies with M. tuberculosis are performed. We investigated whether a novel approach termed luciferase in vivo expression, using an enhanced luciferase-expressing mycobacterial strain, could be used to evaluate antimycobacterial activity in mice. Vectors that expressed firefly luciferase (lux gene) at high levels in the bacillus Calmette-Gu-erin (BCG) strain of Mycobacterium bovis were constructed for use in vivo. One recombinant BCG reporter strain (rBCG-lux) was selected for high-level expression of the lux gene product and for its ability to replicate in mice. Methodology to monitor in vivo growth of the rBCG-lux reporter strain in mice by direct assay of luciferase luminescence in organ homogenates was developed. The utility of this approach for assessing the in vivo efficacies of antimycobacterial compounds was evaluated. The activities of standard antimycobacterial drugs were directly apparent in mice infected with the rBCG-lux reporter strain by statistically significant reductions in spleen luminescence. In addition, antimycobacterial immunity was also evident in BCG-immunized mice, in which suppression of rBCG-lux growth in comparison with that in naive mice was clearly observed. The use of luciferase in vivo expression for the in vivo evaluation of antimycobacterial activity compared favorably with standard CFU determinations in terms of time, labor, expense, and statistical significance but permitted the evaluation of antimycobacterial drugs and immunity in mice in 7 days or less. Thus, the use of this technology can greatly accelerate the process of evaluation of antibiotics and immunogens in animal models for the slowly growing pathogenic mycobacteria.
In vitro bactericidal and in vivo therapeutic activities of a new rifamycin derivative, KRM-1648, against Mycobacterium tuberculosis
Authors: Yamamoto T , Amitani R , Suzuki K , Tanaka E , Murayama T , Kuze F
Published: October 2018

The in vitro and in vivo activities of a new rifamycin derivative, KRM-1648, against Mycobacterium tuberculosis H37Rv were compared with those of rifampin. Bactericidal activity was evaluated by using a silicone-coated slide culture method. The MBC of KRM-1648 was 0.15 to 0.3 microgram/ml for 24 h of exposure, while that of rifampin was > 160 microgram/ml under the same conditions. Against experimental murine tuberculosis, KRM-1648 exhibited significant therapeutic effects, in terms of prolonged survival times for mice compared with those with rifampin treatment, even at lower doses, such as 1 and 3 mg/kg. At a dose of 3 mg/kg, KRM-1648 was at least as effective as rifampin at 10 mg/kg. The combination of KRM-1648 (3 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg) exhibited much more activity than did rifampin (10 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg). These findings suggest that KRM-1648 is a promising candidate for the treatment of tuberculosis.
Chromosomal beta-lactamase genes of Klebsiella oxytoca are divided into two main groups, blaOXY-1 and blaOXY-2
Authors: Fournier B , Roy P H , Lagrange P H , Philippon A
Published: October 2018

The chromosomally encoded beta-lactamase gene (blaOXY-2) of the wild-type Klebsiella oxytoca SL911 was cloned and sequenced. Its nucleotide sequence similarity with the previously sequenced K. oxytoca beta-lactamase gene (blaOXY-1) (Y. Arakawa, M. Ohta, N. Kido, M. Mori, H. Ito, T. Komatsu, Y. Fujii, and N. Kato, Antimicrob. Agents Chemother. 33:63-70, 1989) is 87.3%, and its amino acid similarity is 89.7%. This group of K. oxytoca beta-lactamases is related to chromosomal beta-lactamases of Citrobacter diversus, Proteus vulgaris, and Yersinia enterocolitica and to the plasmid-mediated extended-spectrum beta-lactamases MEN-1 and Toho-1. By colony hybridization with 86 strains susceptible and resistant to aztreonam, isolated in six countries, K. oxytoca beta-lactamase genes hybridized with either a specific blaOXY-1 DNA probe (668 bp) or a blaOXY-2 DNA probe (723 bp). Thus, beta-lactamase genes could be divided into two groups: blaOXY-1 (47% of the strains) and blaOXY-2 (53% of the strains). A study of isoelectric points confirmed the great variability reported in the literature. However, the two beta-lactamase groups were each represented by four different pIs: for OXY-2, 5.2, 5.7, 6.4, and 6.8, with the 5.2 form representing 59% of all OXY-2 enzymes, and for OXY-1, 7.1, 7.5, 8.2, and 8.8, with the 7.5 form representing 88% of all OXY-1 enzymes.
beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca
Authors: Fournier B , Lagrange P H , Philippon A
Published: October 2018

beta-Lactamase gene promoters of 45 clinical Klebsiella oxytoca isolates resistant to beta-lactams and exhibiting beta-lactamase hyperproduction differed from those in 26 susceptible strains. Direct sequencing revealed one mutation in either the -10 or -35 conserved sequences: a G-to-A transition of the fifth base (67%) or a G-to-T transversion of the first base of the -10 sequence (27%) or a T-to-A transversion in the fourth base in the -35 sequence (4%). One strain carried both the -10 transition and the -35 transversion.
Clarithromycin in treatment of early Lyme disease: a pilot study
Authors: Dattwyler R J , Grunwaldt E , Luft B J
Published: October 2018

Forty-one patients with erythema migrans were enrolled in an open-labelled pilot study of oral clarithromycin, 500 mg twice daily for 21 days, for the treatment of early Lyme disease. Immediately posttherapy, pretreatment signs and symptoms resolved among 91% of the 33 evaluable patients. At 6 months, all 28 of the evaluable patients were well. Clarithromycin shows promise as an effective agent for the treatment of early Lyme disease and warrants further study.
The erythromycin resistance gene from the Bacteroides conjugal transposon Tcr Emr 7853 is nearly identical to ermG from Bacillus sphaericus
Authors: Cooper A J , Shoemaker N B , Salyers A A
Published: October 2018

Tcr Emr 7853, from Bacteroides thetaiotaomicron 7853, is a large chromosomal conjugative transposon which encodes resistance to both tetracycline (Tcr) and erythromycin (Emr). The erythromycin resistance gene of Tcr Emr 7853 did not cross-hybridize with ermF, the Emr gene found on previously studied Bacteroides regular and conjugative transposons. We have cloned and sequenced the erythromycin resistance gene from Tcr Emr 7853. The DNA sequence of this gene was 99.6% identical to that of ermG from Bacillus sphaericus.
Preventive chemotherapy of tuberculosis in Cornell model mice with combinations of rifampin, isoniazid, and pyrazinamide
Authors: Dhillon J , Dickinson J M , Sole K , Mitchison D A
Published: October 2018

The efficacies of rifampin-containing preventive regimens were measured in Cornell model mice in which an initially severe infection with Mycobacterium tuberculosis H37Rv was first treated for 7 weeks with 25 mg of isoniazid and 1,000 mg of pyrazinamide per kg of body weight in the diet and then with one of four test regimens given by daily oral gavage for 6 weeks. These regimens were 15 mg of rifampin per kg alone (R), rifampin plus 25 mg of isoniazid per kg (RH), rifampin plus 150 mg of pyrazinamide per kg (RZ), or rifampin plus isoniazid and pyrazinamide (RHZ). The interval between the rifampin gavage and the gavage with the other drugs ranged from 10 to 45 min, so that interference with rifampin absorption did not occur. Mice were sacrificed at 11 and 20 weeks after the termination of chemotherapy, with each killing being preceded by 3 weeks of high-dose dihydrocortisone treatment. Entire spleens and lungs were cultured. The proportions of mice with positive spleens at either killing time were 74% of 43 mice treated with R, 63% of 41 mice treated with RH, 65% of 43 mice treated with RZ, and 53% of 45 mice treated with RHZ, a just significant (P = 0.04) trend for fewer positive spleens with increasing numbers of drugs in the regimen. However, no trend was found in the corresponding proportions of mice with positive spleens or lungs, which were 81, 63, 65, and 71% for mice treated with R, RH, RZ, and RHZ, respectively. Thus, in the Cornell model, R alone, RH, RZ, and RHZ all had similar efficacies.
Pharmacokinetics of trovafloxacin (CP-99,219), a new quinolone, in rats, dogs, and monkeys
Authors: Teng R , Girard D , Gootz T D , Foulds G , Liston T E
Published: October 2018

The pharmacokinetics of trovafloxacin [CP-99,219; 7-(3-azabicyclo[3.1.0]hexyl)-naphthyridone] were studied in rats, dogs, and monkeys following oral and intravenous administration. After intravenous dosing, the systemic clearances of trovafloxacin in rats, dogs, and monkeys were 12.5, 11.1, and 7.2 ml/min/kg of body weight, respectively, and the respective volumes of distribution were 0.9, 1.7, and 4.3 liters/kg, with corresponding elimination half-lives of 0.7, 1.8, and 7.0 h. After the administration of oral doses of 50, 20, and 20 mg/kg to rats, dogs, and monkeys serum trovafloxacin concentrations reached a maximum at 0.6, 2.3, and 2.3 h, respectively, with respective maximum concentrations of trovafloxacin in serum of 11.5, 3.5, and 5.2 micrograms/ml; the corresponding elimination half-lives were 2.2, 2.5, and 7.5 h. The oral bioavailability of trovafloxacin was 68, 58, and 85% in rats, dogs, and monkeys, respectively. The binding of trovafloxacin to serum proteins was concentration independent, averaging 92, 75, and 66% for rats, dogs, and monkeys, respectively. Trovafloxacin penetrated well into tissues in dogs. The urinary recoveries of unchanged drug were less than 5% in dogs and monkeys, with or without incubation with alkali or Glusulase (beta-glucuronidase and sulfatase). In rats, 99.8% of the orally administered radioactivity was recovered in feces, while 20.6, 3.4, and 67.1% of the radioactive dose in bile duct-cannulated rats were recovered in feces, urine, and bile, respectively. These results suggest that the elimination of trovafloxacin from rats, and possibly from dogs and monkeys, is primarily through biliary excretion.
Influence of maturation and growth on cefetamet pivoxil pharmacokinetics: rational dosing for infants
Authors: Hayton W L , Kneer J , de Groot R , Stoeckel K
Published: October 2018

The pharmacokinetics of intravenous (i.v.) cefetamet and the bioavailability of oral cefetamet pivoxil in infants aged 3.5 to 17.3 months who were hospitalized for urological surgery were characterized. The absorption of cefetamet pivoxil administered in a syrup formulation was 38 +/- 19% (n = 5) for infants, which was comparable to values observed for children and adults. The plasma half-life of i.v. cefetamet was 3.03 +/- 0.96 h (mean +/- standard deviation; n = 20) in the infants. This was not different from the value observed for normal adult subjects but was longer than that reported for children aged 3 to 12 years. Urinary recovery of cefetamet after i.v. administration to infants was 63.4 +/- 17.7% (n = 16), which was less than the 80% recovery found in older children and adults. The steady-state volume of distribution was 399 +/- 116 ml/kg of body weight. It was comparable in size and showed the same dependence on body weight as it did in children and adults. The mean systemic clearance per kilogram of body weight in the infants was lower than that in children and adults, apparently because of immaturity of clearance processes. A model that accounted for maturation and growth with increasing age was developed for the clearance. On the basis of this model, the clearance capacity increased from birth to 5 years by a factor of 4.5 because of maturation. Maturation progressed exponentially, with a half-life of 14 months. This model was used to develop dosing regimen guidelines for pediatric patients aged 3.5 months and older.
Susceptibilities of Candida spp. to antifungal agents visualized by two-dimensional scatterplots of relative growth
Authors: Odds F C , Dams G , Just G , Lewi P
Published: October 2018

The growth of 811 clinical yeast isolates in the presence of single concentrations of antifungal agents was measured spectrophotometrically and expressed as a percentage of growth in inhibitor-free control cultures. Two-dimensional scatterplots of the relative growth data allowed for the simple visual determination of some susceptibility trends, including correlations in relative growth between different agents and in relative susceptibilities between different yeast species. A positive susceptibility correlation was found for relative growth results with the azole antifungal agents fluconazole, itraconazole, and ketoconazole for 504 Candida albicans isolates. The relative growth scatterplots for fluconazole versus itraconazole showed that 50 (9.9%) of 504 C. albicans isolates were outliers with respect to the 95% confidence limits for a line of correlated relative growth established with an initial test panel of 59 isolates of this species. The outlying isolates were relatively less susceptible to fluconazole than to itraconazole under the conditions of the test. Most of the outliers were received in 1993 and 1994; only 3.9% of the isolates received in 1991 and 1992 and 1.7% of the isolates received before 1991 showed this differential susceptibility. In addition, most of the outliers came from patients with human immunodeficiency virus infections. The relative growth scatterplots confirmed the known high susceptibility of most Candida parapsilosis isolates to both fluconazole and itraconazole and the specifically low susceptibility of Candida krusei isolates to fluconazole. The scatterplots also illustrated a tendency towards lower (and correlative) relative growth among oral isolates obtained from AIDS patients who responded to azole antifungal treatment than among isolates from clinical nonresponders.
Stereospecific reduction of virginiamycin M1 as the virginiamycin resistance pathway in Streptomyces virginiae
Authors: Lee C K , Minami M , Sakuda S , Nihira T , Yamada Y
Published: October 2018

In a cell extract of Streptomyces virginiae, virginiamycin M1 was inactivated in the presence of NADPH, while virginiamycin S remained intact. The inactivated product of virginiamycin M1 was isolated, and structure analysis revealed that the inactivation involves reduction of a C-16 carbonyl group leading to the formation of 16-dihydrovirginiamycin M1. Acetonide and benzylidene acetal derivatives were synthesized from the two hydroxyl groups on C-14 and C-16, and the C-16 stereochemistry was determined by 13C nuclear magnetic resonance spectroscopy. Two methyl groups of the acetonide derivative gave 13C signals of 20.1 and 30.1 ppm, indicating that the relative stereochemistry of the C-14 and C-16 hydroxy groups is syn. Furthermore, irradiation of the benzylidene methine proton gave clear nuclear Overhauser effect enhancement of the C-14 or C-16 methine protons, indicating that H-14 and H-16 were in an axial configuration. From the (14S) absolute configuration of natural virginiamycin M1 and the syn relative configuration for the C-14 and C-16 hydroxyl groups of the inactivated product, the C-16 absolute configuration of the inactivated product was thus identified as R.
Differential in vitro activities of ionophore compounds against Plasmodium falciparum and mammalian cells
Authors: Gumila C , Ancelin M L , Jeminet G , Delort A M , Miquel G , Vial H J
Published: October 2018

Twenty-two ionophore compounds were screened for their antimalarial activities. They consisted of true ionophores (mobile carriers) and channel-forming quasi-ionophores with different ionic specificities. Eleven of the compounds were found to be extremely efficient inhibitors of Plasmodium falciparum growth in vitro, with 50% inhibitory concentrations of less than 10 ng/ml. Gramicidin D was the most active compound tested, with 50% inhibitory concentration of 0.035 ng/ml. Compounds with identical ionic specificities generally had similar levels of antimalarial activity, and ionophores specific to monovalent cations were the most active. Compounds were further tested to determine their in vitro toxicities against mammalian lymphoblast and macrophage cell lines. Nine of the 22 compounds, i.e., alborixin, lonomycin, nigericin, narasin, monensin and its methylated derivative, lasalocid and its bromo derivative, and gramicidin D, most specific to monovalent cations, were at least 35-fold more active in vitro against P. falciparum than against the two other mammalian cell lines. The enhanced ability to penetrate the erythrocyte membrane after infection could be a factor that determines ionophore selectivity for infected erythrocytes.
Potential use of WR6026 as prophylaxis against transfusion-transmitted American trypanosomiasis
Authors: Chiari E , Oliveira A B , Prado M A , Alves R J , Galvão L M , Araujo F G
Published: October 2018

Since transmission of Chagas' disease by the insect vector is under control in Brazil, transmission by blood transfusion is acquiring special relevance in areas where the disease is endemic and also in countries whose populations are free of infection but that are receiving immigrants from areas where the disease is endemic. Gentian violet, a phenylmethane dye, was the first agent used for the chemical prophylaxis of blood destined for transfusion. A concentration of 0.6 mmol of this dye per liter is effective at eliminating trypomastigotes from blood after 24 h of incubation at 4 degrees C. It is the only effective trypanosomicidal agent available. In the search of alternate compounds, we examined a number of synthetic compounds. They were screened for their activities against blood trypomastigotes of the Y, CL, and B229 strains of Trypanosoma cruzi by using two or more dilutions of each compound. We found that compound Q45, a 6-methoxy-8(diethylaminohexylamino)lepidine dihydrochloride, was highly effective at clearing parasites from infected blood. Doses of 65 and 130 micrograms of this compound eliminated trypomastigotes from blood experimentally contaminated with T. cruzi parasites. These results indicate that Q45 is remarkably active against circulating trypomastigotes. Further studies evaluating Q45 as a prophylactic agent for preventing the transmission of T. cruzi by blood transfusion are of interest.
Characterization of beta-lactamase gene blaPER-2, which encodes an extended-spectrum class A beta-lactamase
Authors: Bauernfeind A , Stemplinger I , Jungwirth R , Mangold P , Amann S , Akalin E , Anğ O , Bal C , Casellas J M
Published: October 2018

Plasmidic extended-spectrum beta-lactamases of Ambler class A are mostly inactive against ceftibuten. Salmonella typhimurium JMC isolated in Argentina harbors a bla gene located on a plasmid (pMVP-5) which confers transferable resistance to oxyiminocephalosporins, aztreonam, and ceftibuten. The beta-lactamase PER-2 (formerly ceftibutenase-1; CTI-1) is highly susceptible to inhibition by clavulanate and is located at a pI of 5.4 after isoelectric focusing. The blaPER-2 gene was cloned and sequenced. The nucleotide sequence of a 2.2-kb insert in vector pBluescript includes an open reading frame of 927 bp. Comparison of the deduced amino acid sequence of PER-2 with those of other beta-lactamases indicates that PER-2 is not closely related to TEM or SHV enzymes (25 to 26% homology). PER-2 is most closely related to PER-1 (86.4% homology), an Ambler class A enzyme first detected in Pseudomonas aeruginosa. An enzyme with an amino acid sequence identical to that of PER-1, meanwhile, was found in various members of the family Enterobacteriaceae isolated from patients in Turkey. Our data indicate that PER-2 and PER-1 represent a new group of Ambler class A extended-spectrum beta-lactamases. PER-2 so far has been detected only in pathogens (S. typhimurium, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis) isolated from patients in South America, while the incidence of PER-1-producing strains so far has been restricted to Turkey, where it occurs both in members of the family Enterobacteriaceae and in P. aeruginosa.
Rifampin resistance in Neisseria meningitidis due to alterations in membrane permeability
Authors: Abadi F J , Carter P E , Cash P , Pennington T H
Published: October 2018

Rifampin-resistant (Rifr) Neisseria meningitidis strains are known to have single point mutations in the central conserved regions of the rpoB gene. We have demonstrated two distinct resistance phenotypes in strains with identical mutations in this region, an intermediate level of resistance in Rifr clinical isolates and a high level of resistance in mutants selected in vitro. The possible role of membrane permeability in the latter was investigated by measuring MICs in the presence of Tween 80; values for high-level-resistance mutants were reduced to intermediate levels, whereas those for intermediate-level-resistance strains were unaffected. The highly resistant mutants were also found to have increased resistance to Triton X-100 and gentian violet. Sequencing of the meningococcal mtrR gene and its promoter region (which determine resistance to hydrophobic agents in Neisseria gonorrhoeae) from susceptible or intermediate strains and highly resistant mutants generated from them showed no mutation within this region. Two-dimensional gel electrophoresis of two parent and Rif mutant strains showed identical shifts in the pI of one protein, indicating that differences between the parent and the highly Rifr mutant are not confined to the rpoB gene. These results indicate that both permeability and rpoB mutations play a role in determining the resistance of N. meningitidis to rifampin.
Comparison of methodologies for synergism testing of drug combinations against resistant strains of Pseudomonas aeruginosa
Authors: Cappelletty D M , Rybak M J
Published: October 2018

The purpose of this study was to determine if synergism was maintained for various combinations of beta-lactams with an aminoglycoside against four clinical strains and one laboratory strain of Pseudomonas aeruginosa which were resistant, according to the MICs, to the beta-lactams and/or aminoglycoside. The results from both the checkerboard and killing curve methodologies were compared. The laboratory strain (ATCC 27853) was manipulated in vitro by serial passage onto agar containing increasing concentrations of each antibiotic to select for resistance. One clinical isolate (R61) was also serially passed to raise the MIC of piperacillin from 128 to 1,024 micrograms/ml. The fractional inhibitory concentration indices for all isolates indicated indifference for all combination therapies, with values ranging from 0.6 to 3. In contrast, killing curve results for all isolates demonstrated synergism with drug concentrations at either one-fourth or one-half the MIC for each organism. The MIC of piperacillin for the laboratory-manipulated clinical isolate R61 was 1,024 micrograms/ml, and synergism was still observed with concentrations of one-half the MIC of piperacillin and amikacin. For clinical isolate R166, which was beta-lactam and tobramycin resistant, synergism continued to be demonstrated with concentrations of tobramycin (1/16 MIC) in combination with piperacillin and cefepime at 1/2 the MIC. The results of this study indicate that against P. aeruginosa, synergism is observed in spite of resistance to beta-lactams and/or aminoglycosides. Synergism appears to be maintained even at very high MICs (piperacillin, 1,024 micrograms/ml; tobramycin, 128 micrograms/ml) with drug concentrations within achievable therapeutic ranges. With current definitions of synergism there was a complete lack of correlation between the results obtained by the checkerboard and killing curve methodologies, with the fractional inhibitory concentration indices showing indifference and killing curves resulting in synergism. The methodologies and definitions of synergism or antagonism are variable and not standardized and should be reevaluated.
Susceptibilities of non-Pseudomonas aeruginosa gram-negative nonfermentative rods to ciprofloxacin, ofloxacin, levofloxacin, D-ofloxacin, sparfloxacin, ceftazidime, piperacillin, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, and imipenem
Authors: Spangler S K , Visalli M A , Jacobs M R , Appelbaum P C
Published: October 2018

Agar dilution MICs of 10 agents against 410 non-Pseudomonas aeruginosa gram-negative nonfermentative rods were determined. MICs at which 50 and 90% of the isolates were inhibited, respectively, were as follows (in micrograms per milliliter): sparfloxacin, 0.5 and 8.0; levofloxacin, 1.0 and 8.0; ciprofloxacin, 2.0 and 32.0; ofloxacin, 2.0 and 32.0; D-ofloxacin, 32.0 and > 64.0; ceftazidime, 8.0 and 64.0; piperacillin with or without tazobactam, 16.0 and > 64.0; trimethoprim-sulfamethoxazole, 0.5 and > 64.0; imipenem, 2.0 and > 64.0. With the exception of those for Stenotrophomonas maltophilia, Burkholderia cepacia, and Alcaligenes faecalis-A. odorans, agar dilution MICs for all strains tested were within 1 dilution of inhibitory (bacteriostatic) levels as determined by time-kill methodology.
Pharmacokinetics of oral fleroxacin in male and premenopausal female volunteers
Authors: Bertino J S , Nafziger A N
Published: October 2018

The pharmacokinetics of oral fleroxacin were compared in men and premenopausal women. The total volume of distribution of the drug was significantly smaller in women in the single-dose trial. No difference in other pharmacokinetic parameters was noted. Since adverse events appear to occur in women more commonly than in men, dose-response studies of fleroxacin in women may be appropriate.
Inhibition of duck hepatitis B virus replication by 2',3'-dideoxy-3'-fluoroguanosine in vitro and in vivo
Authors: Hafkemeyer P , Keppler-Hafkemeyer A , al Haya M A , von Janta-Lipinski M , Matthes E , Lehmann C , Offensperger W B , Offensperger S , Gerok W , Blum H E
Published: October 2018

The antiviral activity of 2',3'-dideoxy-3'-fluoroguanosine (FdG) or its triphosphate was evaluated in the duck hepatitis B virus (DHBV) system in vitro and in vivo. In primary DHBV-infected hepatocytes FdG results in a dose-dependent inhibition of viral replication with a nearly complete inhibition at a concentration of 1 microM. Also in vivo, FdG treatment of DHBV-infected ducklings reduces DHBV DNA replication by more than 90%. These data demonstrate that FdG is a strong inhibitor of DHBV replication in vitro and in vivo.
Pharmacokinetics in nonhuman primates of a prototype carbapenem active against methicillin-resistant Staphylococcus aureus
Authors: Sundelof J G , Thompson R , White K M , Sasor M W , Cama L , Kropp H
Published: October 2018

Pharmacokinetic parameters were determined for imipenem-cilastatin and a carbapenem antibiotic, L-695,256, active against methicillin-resistant Staphylococcus aureus in rhesus monkeys and a chimpanzee. L-695,256 had larger areas under the concentration-time curve than imipenem-cilastatin (30 +/- 5 versus 24 +/- 1 micrograms.h/ml in the rhesus monkeys and 77 versus 60 micrograms.h/ml in the chimpanzee) and a longer half-life at beta phase (1.2 +/- 0.1 versus 0.6 +/- 0.1 h in the rhesus monkeys and 1.0 versus 0.8 h in the chimpanzee). Resistance to hydrolysis by the renal dehydropeptidase-I allowed L-695,256 to be administered as a single agent.
In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to four fluoroquinolones (levofloxacin, d-ofloxacin, ofloxacin, and ciprofloxacin), cefpirome, and meropenem
Authors: Hoppe J E , Rahimi-Galougahi E , Seibert G
Published: October 2018

The in vitro activities of levofloxacin, ofloxacin, d-ofloxacin, ciprofloxacin, cefpirome, and meropenem against 34 clinical isolates each of Bordetella pertussis and Bordetella parapertussis were determined by agar dilution on Mueller-Hinton agar supplemented with 5% horse blood. Levofloxacin was as active as ciprofloxacin against both species (MIC, 0.06 microgram/ml) and more active than ofloxacin and d-ofloxacin. Cefpirome was more active against B. pertussis (MIC, 1.0 microgram/ml) than against B. parapertussis (MIC, > 2 micrograms/ml), while the reverse was true for meropenem (MIC, 2.0 micrograms/ml against B. pertussis and 1.0 microgram/ml against B. parapertussis).
Efficacy of clarithromycin versus that of clindamycin for single-dose prophylaxis of experimental streptococcal endocarditis
Authors: Vermot D , Entenza J M , Vouillamoz J , Glauser M P , Moreillon P
Published: October 2018

Clarithromycin is compared with clindamycin for single-dose prophylaxis of streptococcal endocarditis in rats. Human-like kinetics of the two antibiotics prevented endocarditis in animals challenged with both small and large amounts of bacterial inocula. Clarithromycin was marginally superior to clindamycin against small amounts of inocula. Clarithromycin may be considered for endocarditis chemoprophylaxis in human.
Influence of experimental rat model of multiple organ dysfunction on cefepime and amikacin pharmacokinetics
Authors: Mimoz O , Jacolot A , Padoin C , Quillard J , Tod M , Louchahi K , Samii K , Petitjean O
Published: October 2018

We adapted an experimental model of multiple organ dysfunction to study the alterations it induces in the pharmacology of cefepime and amikacin. The half-lives of both antibiotics were significantly prolonged because of nonsignificant enhancement of the volume of distribution and reduced renal elimination. In the presence of multiple organ dysfunction, the concentration of each antibiotic in the lungs, compared with that in the lungs of healthy controls, was significantly decreased, despite similar concentrations in plasma, indicating that the application of a standard antibiotic concentration in plasma could lead to underdosage in tissues during the initial days of therapy.
In vitro susceptibilities of clinical and environmental isolates of Cryptococcus neoformans to five antifungal drugs
Authors: Franzot S P , Hamdan J S
Published: October 2018

A total of 53 Cryptococcus neoformans strains, including clinical and environmental Brazilian isolates, were tested for their susceptibilities to amphotericin B, 5-flucytosine, ketoconazole, fluconazole, and itraconazole. The tests were performed according to the National Committee of Clinical Laboratory Standards recommendations (document M27-P). In general, there was a remarkable homogeneity of results for all strains, and comparable MICs were found for environmental and clinical isolates. This paper represents the first contribution in which susceptibility data for Brazilian C. neoformans isolates are provided.
Survey of Klebsiella pneumoniae producing extended-spectrum beta-lactamases: prevalence of TEM-3 and first identification of TEM-26 in France
Authors: Soilleux M J , Morand A M , Arlet G J , Scavizzi M R , Labia R
Published: October 2018

Crude extracts from 115 extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates were analyzed biochemically. The TEM-3 type was encountered 108 times, SHV types were encountered 7 times, and the TEM-26 type was encountered only once. For the last one, the gene was identified; an adenine was detected at position 925, as in blaTEM-26B not in blaTEM-26.
Reaction of roxithromycin and clarithromycin with macrolide-inactivating enzymes from highly erythromycin-resistant Escherichia coli
Authors: O'Hara K , Yamamoto K
Published: October 2018

The activities of two new 14-membered-ring macrolide antibiotics, roxithromycin (RXM) and clarithromycin (CAM), against highly erythromycin (EM)-resistant Escherichia coli strains were evaluated. Pretreatment of macrolide phosphotransferase (MPH) (2') I-producing strains with EM increased the MICs of EM and CAM without any noticeable change in the MIC of RXM. The MPH (2') II-producing strain was more susceptible to CAM, while the EM esterase-producing strains were more susceptible to RXM than EM. Pretreatment of these latter two strains with EM did not alter their susceptibility to either RXM or CAM. In addition, the compounds were assessed as substrates for inactivation by crude enzyme preparations. Of the 14-membered-ring macrolides, RXM was the least favored substrate for MPH (2') I or II. CAM and RXM were substrates for the EM esterase but were the least preferred of the 14-membered-ring macrolides.
In vitro activities of oxazolidinones U-100592 and U-100766 against penicillin-resistant and cephalosporin-resistant strains of Streptococcus pneumoniae
Authors: Mason E O , Lamberth L B , Kaplan S L
Published: October 2018

Two oxazolidinones and ceftriaxone, imipenem, rifampin, and vancomycin were tested against 162 penicillin-intermediate and 68 penicillin-resistant strains of pneumococci. U-100592 is two- to fourfold more active than U-100766 against penicillin-resistant pneumococci. The MICs of U-100592 at which 90% of the isolates were inhibited were 0.25 and 0.5 microgram/ml for penicillin-intermediate and -resistant strains, respectively, and 0.5 microgram/ml for ceftriaxone-susceptible, -intermediate, and -resistant strains. U-100592 MICs for 7 of 230 strains (2 from blood, 3 from middle-ear fluid, and 2 from the upper respiratory tract) were 1 microgram/ml.
Inhibition of 2,3-oxidosqualene-lanosterol cyclase in Candida albicans by pyridinium ion-based inhibitors
Authors: Goldman R C , Zakula D , Capobianco J O , Sharpe B A , Griffin J H
Published: October 2018

The N-(4E,8E)-5,9,13-trimethyl-4,8,12-tetradecatrien-1- ylpyridinium and N-(4E,8E)-5,9,13-trimethyl-4,8,12-tetradecatrien-1- ylpicolinium cations were evaluated for their ability to inhibit 2,3-oxidosqualene-lanosterol cyclase activity in Candida albicans. Both compounds inhibited fungal growth, were fungicidal, and resulted in the accumulation of squalene epoxide concurrent with a decrease in ergosterol, monomethyl sterols, and lanosterol, as was expected for the specific inhibition of 2,3-oxidosqualene-lanosterol cyclase activity. These compounds are electron-poor aromatic mimics of a monocyclized transition state or high-energy intermediate formed from oxidosqualene, which may explain their selective action.
Comparison of effects of famciclovir and valaciclovir on pathogenesis of herpes simplex virus type 2 in a murine infection model
Authors: Thackray A M , Field H J
Published: October 2018

The effects of famciclovir (FCV) and valaciclovir (VACV) were compared in a cutaneous infection model for herpes simplex virus type 2 (HSV-2). The compounds were administered orally from day 1 to day 5 postinfection. Both compounds reduced local inflammation and virus replication in the skin. FCV markedly reduced mortality and virus replication in the nervous system. On the cessation of therapy after 5 days, when the levels of infectious virus in the tissues were reduced to below the level of detection, there followed a rebound of virus replication in the ganglia and brain stems of mice that had been treated with VACV. The recurrence of infection in the brain stem occurred on three separate occasions. No such recurrences were observed following FCV treatment. When ganglia were explanted from survivors 6 weeks later, latent virus was shown to be reactivated in all 10 of 10 control, untreated mice. The number of mice whose ganglia yielded virus was reduced to 60% in mice that had been treated with VACV, whereas no mice that had been treated with FCV had evidence of latent infection by this test.
Na+/H+ antiport activity conferred by Bacillus subtilis tetA(L), a 5' truncation product of tetA(L), and related plasmid genes upon Escherichia coli
Authors: Cheng J , Baldwin K , Guffanti A A , Krulwich T A
Published: October 2018

An Escherichia coli transformant expressing the Bacillus subtilis tetA(L) gene from a weak promoter was challenged by growth on medium with low, increasing tetracycline concentrations. Changes in the substrate preference ratios of the TetA(L)-mediated resistances and antiports were examined in view of recent findings suggesting that TetA(L) catalyzes efflux of Na+ in exchange for protons in addition to having the ability to catalyze metal-tetracycline/H+ antiport. After growth of the transformant on 1 microgram or more of tetracycline per ml for 12 to 15 h, the tetA(L) gene in the plasmid was found to be disrupted by an IS10 element 50 bp from the 5' end of the coding sequence. This disrupted recombinant plasmid, pKB1, conferred greater tetracycline resistance and higher levels of membrane metal-tetracycline/proton antiport than the original plasmid, pJTA1, but conferred lower NA+ resistance and Na+/H+ antiport levels than the original plasmid. The results indicate that the 5' end of the gene is necessary for optimal Na+/H+ antiport but that some such activity as well as robust tetracycline/H+ antiport persists in its absence. Two plasmid genes, tet(K) and qacA, were compared with tetA(L) vis-à-vis their abilities to enhance the Na+/H+ antiporter activity of everted vesicles from E. coli transformants. tet(K), which is more closely related to tetA(L), catalyzed 22Na+ uptake by energized vesicles, whereas the less closely related qacA gene did not.
Sequence of quinolone resistance-determining region of gyrA gene for clinical isolates and for an in vitro-selected quinolone-resistant strain of Coxiella burnetii
Authors: Musso D , Drancourt M , Osscini S , Raoult D
Published: October 2018

We report the sequence of the quinolone resistance-determining region of the gyrA genes of either susceptible or low-level-resistant clinical isolates of Coxiella burnetii. The sequences of low-level (MICs, 4 micrograms/ml) and high-level (MICs, 8 and 16 micrograms/ml) resistant strains stepwise selected in vitro were also determined. The gene sequences of all of the clinical isolates and that of the in vitro-selected low-level-resistant strain were identical. Sequence analysis of the in vitro-selected high-level-resistant strain revealed a nucleotide mutation leading to an amino acid substitution of Gly in place of Glu at position 87 of the GyrA amino acid sequence. These results indicate that high-level resistance to ciprofloxacin is associated with a nucleotide mutation in gyrA, whereas low-level resistance to quinolones is not.
Activities of the glycylcyclines N,N-dimethylglycylamido-minocycline and N,N-dimethylglycylamido-6-demethyl-6-deoxytetracycline against Nocardia spp. and tetracycline-resistant isolates of rapidly growing mycobacteria
Authors: Brown B A , Wallace R J , Onyi G
Published: October 2018

Susceptibilities to the new semisynthetic tetracycline (Tet) compounds N,N-dimethylglycylamido-minocycline (DMG-MINO) and N,N-dimethylglycylamido-6-demethyl-6-deoxytetracycline (DMG-DMDOT) were compared with those to doxycycline, minocycline, and Tet for 198 Tet-resistant (Tetr) and 33 Tet-susceptible (Tets) clinical isolates of rapidly growing mycobacteria (RGM) including the Mycobacterium fortuitum group, Mycobacterium abscessus, Mycobacterium chelonae, and Mycobacterium mucogenicum and 68 isolates belonging to six taxa of Nocardia spp. All Tetr RGM were highly susceptible to the glycylcyclines. The MICs at which 50 and 90% of isolates are inhibited were < or = 0.125 and < or = 0.25 microgram/ml, respectively, for DMG-DMDOT and < or = 0.25 and 1 microgram/ml, respectively, for DMG-MINO. The MIC of DMG-DMDOT at which 50% of Tetr strains are inhibited was the same as that for Tets strains for each of the four taxa of RGM. The new agents were less active against Nocardia spp. MICs of DMG-DMDOT were comparable to those of minocycline except for the MICs for Nocardia brasiliensis sensu stricto, the new taxon Nocardia pseudobrasiliensis, and some isolates of Nocardia nova, against which they were four- to eightfold more active. The MICs of DMG-DMDOT were consistently lower than those of DMG-MINO for RGM. This class of drugs offers exciting therapeutic potential for RGM and for selected species of Nocardia.
Intracellular activities of RP 59500 (quinupristin-dalfopristin) and sparfloxacin against Enterococcus faecium
Authors: Herrera-Insúa I , Jacques-Palaz K , Murray B E , Rakita R M
Published: October 2018

RP 59500, a combination of the streptogramins quinupristin and dalfopristin, and sparfloxacin are new antibiotics with good in vitro activities against Enterococcus faecium, which is an increasingly important nosocomial pathogen with resistance to multiple antimicrobials. Since fluoroquinolones and related macrolides have displayed high intracellular concentrations inside host cells, we evaluated the intracellular activities of these agents inside neutrophils against three strains each of vancomycin-susceptible E. faecium (VSEF) and vancomycin-resistant E. faecium (VREF). At concentrations equal to four times the MIC, RP 59500 and sparfloxacin decreased the number of intracellular VSEF organisms, while both antibiotics were at best bacteriostatic against intracellular VREF strains. At concentrations equal to one-fourth of the MIC, both antibiotics were bacteriostatic against intracellular VSEF strains but were ineffective in inhibiting the growth of VREF strains. Despite their anticipated markedly higher intracellular human neutrophil (PMN) concentrations, RP 59500 and sparfloxacin activities in medium alone were equal to or greater than those inside PMNs against almost all strains. We conclude that the intracellular PMN concentrations of these antibiotics may not be directly related to their intracellular activities in our assay. The reason for the differences in their activities against VSEF versus VREF remains undefined.
Frequency of drug resistance in Plasmodium falciparum: a nonsynergistic combination of 5-fluoroorotate and atovaquone suppresses in vitro resistance
Authors: Gassis S , Rathod P K
Published: October 2018

A combination of 5-fluoroorotate and atovaquone eliminated Plasmodium falciparum in long-term cultures more efficiently than either compound alone. The improved potency came not through synergistic activity but through decreased frequency of drug resistance. In support of this finding, it was shown that 5-fluoroorotate and atovaquone do not act in a synergistic fashion, that 5-fluoroorotate-resistant and atovaquone-resistant P. falciparum organisms generated in vitro do not show cross-resistance, and that the frequency of simultaneous resistance to the two compounds approached the product of their individual resistance frequencies. To demonstrate the last finding, and establish proof of principle, an in vitro method was developed for measuring the frequency of drug resistance in P. falciparum. By this method, it was shown that the frequency of resistance to 10(-7) M 5-fluoroorotate was about 10(-6) and the frequency of resistance to 10(-8) M atovaquone was about 10(-5); the frequency of simultaneous resistance to a combination of 10(-7) M 5-fluoroorotate and 10(-8) M atovaquone was less than 5 x 10(-10). On the basis of additional measurements, it was estimated that the frequency of simultaneous resistance to higher, pharmacologically more relevant, concentrations of 10(-6) M 5-fluoroorotate and 10(-7) M atovaquone would be less than 10(-17). Control experiments demonstrated that these drug combinations did not cause increased toxicity to mammalian cells in culture. On this basis, it is predicted that a combination of 5-fluoroorotate and atovaquone will successfully eliminate typical malarial infections in animals and in human patients at doses that are readily tolerated.