bluuebunny/crossref_metadata_2025 huggingface dataset:
The anti-human immunodeficiency virus agent 3'-fluorothymidine induces DNA damage and apoptosis in human lymphoblastoid cells
Authors: Sundseth R , Joyner S S , Moore J T , Dornsife R E , Dev I K
Published: October 2018

Patients infected with the human immunodeficiency virus experienced severe hematopoietic toxicity after treatment with the deoxynucleoside analog 3'-fluorothymidine (FLT). Using several methods for the analysis of genome integrity, including histochemical staining of the 3' ends of DNA and both conventional and pulsed-field agarose gel electrophoresis, we demonstrated that FLT caused extensive DNA fragmentation in CEM cells that was not observed when these cells were treated with other, less toxic thymidine analogs. In addition, a distinctive pattern of small DNA fragments that is characteristic of cells in the process of programmed cell death was observed in the genomic DNA of CEM cells treated with FLT. We conclude that FLT induces DNA fragmentation and apoptosis in a human cell line of hematopoietic origin, and we offer this observation as a possible explanation for the severe toxicity of FLT observed in vivo.
Evolution of drug resistance in Salmonella panama isolates in Chile
Authors: Cordano A M , Virgilio R
Published: October 2018

In a search for Salmonella isolates in the environment in Chile in 1975, drug-susceptible strains of Salmonella panama were recovered for the first time from river water and vegetables in the vicinity of Santiago. Two to 3 years later, antibiotic-resistant S. panama began to appear in a variety of sources (meat, animals, vegetables, etc.), giving rise to a human epidemic that involved the entire nation. Of 139 clinical isolates studied, 7 were drug susceptible, 11 were resistant only to nitrofurans, and 3 were streptomycin, spectinomycin, and nitrofuran resistant; none of these 21 isolates harbored plasmid DNA. Most isolates (n = 107) were resistant to nitrofurans (chromosomal) and to streptomycin, spectinomycin, sulfonamides, tetracycline, and mercuric and tellurite salts; this multidrug resistance was encoded on a 218-kb plasmid classified in a number of strains as being in the IncHI2 group. From 1982 to 1993, 11 isolates acquired an additional self-transferable plasmid coding for resistance to any one of ampicillin (61 kb), ampicillin and trimethoprim (65 kb), ampicillin, trimethoprim, streptomycin, and sulfonamides (71 kb), ampicillin, gentamicin, kanamycin, and tetracycline (120 kb), or a nontransferable plasmid of approximately 6 kb encoding resistance to ampicillin or kanamycin. With the exception of ampicillin or ampicillin and trimethoprim resistance, S. panama isolates from foodstuffs, mainly pork meat products, and animals had resistance patterns that were the same as those found in clinical specimens. Remarkably, strains from goats and goat cheese and from shellfish isolated in particular rural regions were either drug susceptible or resistant only to streptomycin-spectinomycin encoded on a mobile genetic element and to nitrofurans. The report describes the arrival of a susceptible S. panama strain, its spread all over the country, and the evolution of progressively complex resistance patterns.
Anti-Clostridium difficile bovine immunoglobulin concentrate inhibits cytotoxicity and enterotoxicity of C. difficile toxins
Authors: Kelly C P , Pothoulakis C , Vavva F , Castagliuolo I , Bostwick E F , O'Keane J C , Keates S , LaMont J T
Published: October 2018

Clostridium difficile diarrhea and colitis result from the actions of bacterial exotoxins on the colonic mucosa. This study examined the ability of hyperimmune bovine colostral antibodies to neutralize the biological effects of these toxins. Anti-C. difficile bovine immunoglobulin concentrate was prepared from the colostral milk of Holstein cows previously immunized with C. difficile toxoids. The anti-C. difficile bovine immunoglobulin concentrate contained high levels of bovine immunoglobulin G specific for C. difficile toxins A and B, as evaluated by enzyme-linked immunosorbent assay. Anti-C. difficile bovine immunoglobulin concentrate neutralized the cytotoxic effects of purified toxin A and toxin B on cultured human fibroblasts, whereas control bovine immunoglobulin concentrate had little toxin-neutralizing activity. Anti-C. difficile bovine immunoglobulin concentrate also blocked the binding of toxin A to its enterocyte receptor and inhibited the enterotoxic effects of C. difficile toxins on the rat ileum, as measured by an increased rat ileal loop weight/length ratio (63% inhibition; P < 0.01), increased mannitol permeability (92% inhibition; P < 0.01), and histologic grading of enteritis (P < 0.01 versus nonimmune bovine immunoglobulin concentrate). Thus, anti-C. difficile bovine immunoglobulin concentrate neutralizes the cytotoxic effects of C. difficile toxins in vitro and inhibits their enterotoxic effects in vivo. This agent may be clinically useful in the prevention and treatment of C. difficile diarrhea and colitis.
Correlation between rhodamine 123 accumulation and azole sensitivity in Candida species: possible role for drug efflux in drug resistance
Authors: Clark F S , Parkinson T , Hitchcock C A , Gow N A
Published: October 2018

A wide variety of prokaryotic and eukaryotic cells exhibit a multidrug resistance (MDR) phenotype, indicating that resistance to potentially toxic compounds is mediated by their active efflux from the cell. We have sought to determine whether resistance to azoles in some strains of Candida species may be due in part to active drug efflux. Rhodamine 123 (Rh123) is a fluorescent compound that is transported by a wide variety of MDR cell types. We have shown that certain azole-resistant strains of Candida albicans, C. glabrata, and C. krusei accumulate less Rh123 than azole-susceptible ones. In C. albicans, Rh123 accumulation was growth phase and temperature dependent and was increased by proton uncouplers and by reserpine, an MDR modulator. This is consistent with an energy-dependent efflux mechanism for Rh123, mediated by an MDR transporter. In C. glabrata, but not in C. albicans, there was competition between Rh123 and fluconazole for efflux. Thus, in C. glabrata, Rh123 and fluconazole appear to be transported via a common MDR-like transporter, whereas in C. albicans, the Rh123 transporter does not appear to transport azoles.
Activity of KRM-1648 alone or in combination with both ethambutol and kanamycin or clarithromycin against Mycobacterium intracellulare infections in beige mice
Authors: Yamamoto T , Amitani R , Suzuki K , Tanaka E , Murayama T , Kuze F
Published: October 2018

The in vivo activities of KRM-1648 alone or in combination with both ethambutol (EB) and kanamycin (KM) or clarithromycin (CAM) were tested against Mycobacterium intracellulare infections in beige mice. KRM-1648 was more active than rifampin (RFP) when each drug was used alone, and the efficacy of KRM-1648 was similar to those of both kanamycin and clarithromycin. The combination KRM-1648-KM-EB was strongly active and rapidly reduced the numbers of bacilli both in lungs and in spleens compared with RFP-KM-EB. The combination KRM-1648-CAM had greater therapeutic effects than RFP-CAM; this difference in efficacy was more pronounced for lungs than for spleens. These findings suggest that KRM-1648 is a promising candidate for combination therapy with other potent antimycobacterial drugs.
Anticytomegaloviral activity of methotrexate associated with preferential accumulation of drug by cytomegalovirus-infected cells
Authors: Wachsman M , Hamzeh F M , Saito H , Lietman P S
Published: October 2018

We extend the observation that inhibitors of pyrimidine biosynthesis are active against human cytomegalovirus by demonstrating that methotrexate (MTX) has preferential activity against cytomegalovirus replication. The 50% and 90% inhibitory concentrations of MTX for inhibition of cytomegaloviral DNA replication at 3 days postinfection in MRC-5 cells were 0.05 and 0.2 microM, respectively. No cell toxicity was observed in uninfected confluent cells at the highest concentration tested (1 microM). Under similar conditions (3 days of treatment with 0.2 microM MTX), intracellular dTTP pools were diminished in cytomegalovirus-infected cells (87% decrease relative to untreated infected cells, P < 0.001) but were not reduced in uninfected cells. A potential explanation for the preferential antiviral effect of MTX was that human cytomegalovirus-infected cells preferentially accumulated MTX. Increased intracellular accumulation and increased polyglutamation of MTX were observed in cytomegalovirus-infected cells compared with uninfected cells. Increased uptake of [3H]MTX by cytomegalovirus-infected cells was first observed at 48 h postinfection, with threefold-higher accumulation within infected cells. By 96 h, accumulation had increased to approximately fourfold in comparison with uninfected cells. The uptake of [3H]MTX was saturable and was blocked by addition of unlabelled MTX. Intracellular MTX in infected cells was almost entirely in the polyglutamated form, as demonstrated by thin-layer chromatography, whereas intracellular MTX was almost exclusively in the parent form in uninfected cells.
Sequences of beta-lactamase genes encoding CTX-M-1 (MEN-1) and CTX-M-2 and relationship of their amino acid sequences with those of other beta-lactamases
Authors: Bauernfeind A , Stemplinger I , Jungwirth R , Ernst S , Casellas J M
Published: October 2018

Amino acid sequences determined either by protein sequencing or by DNA sequencing are identical for cefotaximases CTX-M-1 and MEN-1, whereas CTX-M-2 is 84% identical to CTX-M-1/MEN-1. Both beta-lactamases are distantly related to other plasmidic class A enzymes (homology to TEM-1 is 38.1% for CTX-M-1/MEN-1 and 36.5% for CTX-M-2); the closest relationship was with the chromosomal beta-lactamase of Klebsiella oxytoca E23004 (homologies of 74.5% for CTX-M-1/MEN-1 and 77.9% for CTX-M-2). The cefotaximases CTX-M-1/MEN-1 and CTX-M-2 represent two members of a new subgroup of plasmidic class A beta-lactamases.
Susceptibility of melanized and nonmelanized Cryptococcus neoformans to the melanin-binding compounds trifluoperazine and chloroquine
Authors: Wang Y , Casadevall A
Published: October 2018

Cryptococcus neoformans is an opportunistic fungal pathogen which becomes heavily melanized in the presence of phenolic substrates such as L-dopa. Various drugs are known to bind to melanin with high affinity, including the antipsychotic agent trifluoperazine and the antimalarial agent chloroquine. We hypothesized that drugs which bind melanin may have different toxicities for melanized and nonmelanized C. neoformans cells. The effects of trifluoperazine and chloroquine or C. neoformans were determined by measuring cell viability after exposure to these drugs. Cell viability was measured by CFU determination and flow cytometry with propidium iodide staining. Melanized cells were more susceptible than nonmelanized cells to the fungicidal effects of trifluoperazine. Chloroquine had no fungicidal effect on either melanized or nonmelanized C. neoformans under the conditions studied. Flow cytometry of trifluoperazine-treated C. neoformans cells stained with the mitochondrial stain dihydrorhodamine 123 revealed fluorescence changes consistent with mitochondrial damage. Our results indicate that melanized and nonmelanized C. neoformans cells can differ in susceptibility to certain drugs and suggest that strategies which target melanin may be productive for antifungal-drug discovery.
In vitro activities of rifabutin, azithromycin, ciprofloxacin, clarithromycin, clofazimine, ethambutol, and amikacin in combinations of two, three, and four drugs against Mycobacterium avium
Authors: Yajko D M , Sanders C A , Madej J J , Cawthon V L , Hadley W K
Published: October 2018

Multidrug therapy is recommended for treatment of Mycobacterium avium complex (MAC) bacteremia in patients with AIDS. Azithromycin, clarithromycin, rifabutin, ciprofloxacin, ethambutol, clofazimine, and amikacin have all been suggested for use in treating MAC bacteremia, but the most active combinations of these drugs have not been identified, nor has the minimum number of drugs needed for effective therapy been determined. To address the former, the in vitro bactericidal activities of all two-, three-, and four-drug combinations of these seven agents was determined by using 10 blood-derived strains of MAC isolated from patients with AIDS. The activities of the 132 drug combinations were compared by statistical analysis of survival means (analysis of variance) and further evaluated by determining the percentage of strains considered susceptible to each combination. When susceptibility was defined as a decrease in CFU of > or = 2 log10, no two- or three-drug combination and only two four-drug combinations were active against all 10 MAC strains. When a less stringent definition was applied (> or = 1 log10 decrease in CFU), 1 two-drug combinations, 9 three-drug combinations, and 31 four-drug combinations showed activity against all 10 strains. Eighteen selected drug combinations were also tested for intracellular activity in MAC-infected J774 cells. Combinations which contained amikacin as a component were considerably less active against intracellular MAC organisms than against organisms in broth. The opposite result was obtained for the combination of clarithromycin plus clofazimine.
Cerebrospinal fluid ceftazidime kinetics in patients with external ventriculostomies
Authors: Nau R , Prange H W , Kinzig M , Frank A , Dressel A , Scholz P , Kolenda H , Sörgel F
Published: October 2018

Ceftazidime has proven to be effective for the treatment of bacterial meningitis caused by multiresistant gram-negative bacteria. Since nosocomial central nervous system infections are often accompanied by only a minor dysfunction of the blood-cerebrospinal fluid (CSF) barrier, patients with noninflammatory occlusive hydrocephalus who had undergone external ventriculostomy were studied (n = 8). Serum and CSF were drawn repeatedly after the administration of the first dose of ceftazidime (3 g over 30 min intravenously), and concentrations were determined by high-performance liquid chromatography by using UV detection. The concentrations of ceftazidime in CSF were maximal at 1 to 13 h (median, 5.5 h) after the end of the infusion and ranged from 0.73 to 2.80 mg/liter (median, 1.56 mg/liter). The elimination half-lives were 3.13 to 18.1 h (median, 10.7 h) in CSF compared with 2.02 to 5.24 h (median, 3.74 h) in serum. The ratios of the areas under the concentration-time curves in CSF and serum (AUCCSF/AUCS) ranged from 0.027 to 0.123 (median, 0.054). After the administration of a single dose of 3 g, the maximum concentrations of ceftazidime in CSF were approximately four times higher than those after the administration of 2-g intravenous doses of cefotaxime (median, 0.44 mg/liter) and ceftriaxone (median, 0.43 mg/liter) (R. Nau, H. W. Prange, P. Muth, G. Mahr, S. Menck, H. Kolenda, and F. Sörgel, Antimicrob. Agents Chemother. 37:1518-1524, 1993). The median AUCCSF/AUCS ratio of ceftazidime was slightly below that of cefotaxime (0.12), but it was 1 order of magnitude above the median AUCCSF/AUCS of ceftriaxone (0.007) (Nau et al., Antimicrob. Agents Chemother. 37:1518-1524, 1993). The concentrations of ceftazidime observed in CSF were above the MICs for most Pseudomonas aeruginosa strains. However, they are probably not high enough to be rapidly bactericidal. For this reason, the daily dose should be increased to 12 g in cases of P. aeruginosa infections of the central nervous system when the blood-CSF barrier is minimally impaired.
Distribution of azithromycin into brain tissue, cerebrospinal fluid, and aqueous humor of the eye
Authors: Jaruratanasirikul S , Hortiwakul R , Tantisarasart T , Phuenpathom N , Tussanasunthornwong S
Published: October 2018

To measure the concentrations of azithromycin in the central nervous system, 20 patients with brain tumors (group I) received a single 500-mg oral dose of azithromycin either 24, 48, 72, or 96 h prior to the tumor removal operation and 10 patients with cataracts undergoing surgery (group II) and 7 patients scheduled to undergo lumbar puncture (group III) received the same dose of azithromycin 24 h prior to the operation or procedure. Serum from all patients, brain tissue from group I, aqueous humor from group II, and cerebrospinal fluid from group III were assayed for azithromycin concentration. The mean concentrations of azithromycin in brain tissue 24, 48, 72, and 96 h after administration were 2.63 +/- 2.58, 3.64 +/- 3.81, 0.74 +/- 0.37, and 0.41 micrograms/g, respectively. In contrast, the concentrations of azithromycin in cerebrospinal fluid and aqueous humor of the eye were very low or undetectable. Therefore, these data show that azithromycin appears to be widely distributed into brain tissue but not into cerebrospinal fluid or aqueous humor of the eye.
Oligonucleotide probes for detection of cephalosporinases among Bacteroides strains
Authors: Mastrantonio P , Cardines R , Spigaglia P
Published: October 2018

Two oligonucleotide probes selected from the sequences of cepA and cfxA genes, respectively, were used to detect beta-lactamase production among strains of the Bacteroides fragilis group. By using these probes, colony hybridization was shown to be a specific and rapid method for identifying the more prevalent beta-lactamase, CepA, and the rarer CfxA enzyme among B. fragilis strains.
Macrolide susceptibility of Mycoplasma hyorhinis isolated from piglets
Authors: Kobayashi H , Morozumi T , Munthali G , Mitani K , Ito N , Yamamoto K
Published: October 2018

Twenty strains of Mycoplasma hyorhinis were investigated for their in vitro susceptibilities to 15 antimicrobial agents by broth and agar dilution methods. Two of the 20 field strains showed low susceptibility to 14- and 16-membered macrolide antimicrobial agents tested. The two field strains were considered inducibly resistant to macrolides.
Susceptibilities of Mycoplasma pneumoniae, Mycoplasma hominis, and Ureaplasma urealyticum to a new quinolone, trovafloxacin (CP-99,219)
Authors: Kenny G E , Cartwright F D
Published: October 2018

The susceptibilities of mycoplasmas to a new quinolone, trovafloxacin (CP-99,219), were compared with those to sparfloxacin and ofloxacin. Mycoplasma pneumoniae was as susceptible to trovafloxacin (MIC = 0.25 microgram/ml) as to sparfloxacin and fourfold less susceptible to ofloxacin. Mycoplasma hominis was highly susceptible to trovafloxacin (MIC = 0.06 microgram/ml) and sparfloxacin (MIC = 0.03 microgram/ml) and less susceptible to ofloxacin (MIC = 0.5 microgram/ml). Ureaplasma urealyticum was most susceptible to trovafloxacin, with susceptibilities ranging from 0.06 to 0.5 microgram/ml compared with 0.25 to 1.0 microgram of sparfloxacin per ml and 1 to 4 micrograms of ofloxacin per ml.
Altered peptidoglycan composition in vancomycin-resistant Enterococcus faecalis
Authors: de Jonge B L , Handwerger S , Gage D
Published: October 2018

The muropeptide compositions of isogenic vancomycin-resistant and -susceptible Enterococcus faecalis strains were analyzed by reverse-phase high-performance liquid chromatography combined with amino acid analysis and fast atom bombardment mass spectrometry. Peptidoglycan of the susceptible strain contained pentapeptides as stem peptides, whereas peptidoglycan of the isogenic resistant strain was composed of muropeptides with tetrapeptide stem peptides. Despite the synthesis of lactate-terminating peptidoglycan precursors, no lactate-containing muropeptides were detected in peptidoglycan of the resistant strain. These findings indicate that either lactate-terminating precursors are not incorporated into peptidoglycan of the resistant strain or that the lactate residues are removed from peptidoglycan during synthesis.
Emergence of high rates of antimicrobial resistance among viridans group streptococci in the United States
Authors: Doern G V , Ferraro M J , Brueggemann A B , Ruoff K L
Published: October 2018

Three hundred fifty-two blood culture isolates of viridans group streptococci obtained from 43 U.S. medical centers during 1993 and 1994 were characterized. Included were 48 isolates of "Streptococcus milleri," 219 S. mitis isolates, 29 S. salivarius isolates, and 56 S. sanguis isolates. High-level penicillin resistance (MIC, > or = 4.0 micrograms/ml) was noted among 13.4% of the strains; for 42.9% of the strains, penicillin MICs were 0.25 to 2.0 micrograms/ml (i.e., intermediate resistance). In general, amoxicillin was slightly more active than penicillin. The rank order of activity for five cephalosporins versus viridans group streptococci was cefpodoxime = ceftriaxone > cefprozil = cefuroxime > cephalexin. The percentages of isolates resistant (MIC, > or = 2 micrograms/ml) to these agents were 15, 17, 18, 20, and 96, respectively. The rates of resistance to erythromycin, tetracycline, and trimethoprim-sulfamethoxazole were 12 to 38%. Resistance to either chloramphenicol or ofloxacin was uncommon (i.e., < 1%). In general, among the four species, S. mitis was the most resistant and "S. milleri" was the most susceptible.
Quantitative correlation between susceptibility and OprJ production in NfxB mutants of Pseudomonas aeruginosa
Authors: Masuda N , Gotoh N , Ohya S , Nishino T
Published: October 2018

Various Pseudomonas aeruginosa PAO1 NfxB mutants were isolated on agar plates containing cefpirome and ofloxacin. They were classified into type A and type B, based on the degrees of changes in their susceptibilities. Type A mutants were four to eight times more resistant to ofloxacin, erythromycin, and new zwitterionic cephems, i.e., cefpirome, cefclidin, cefozopran, and cefoselis, than was the parent strain, PAO1. In contrast, type B mutants were more resistant to tetracycline and chloramphenicol, as well as ofloxacin, erythromycin, and the new zwitterionic cephems, than was PAO1, and they were four to eight times more susceptible to carbenicillin, sulbenicillin, imipenem, panipenem, biapenem, moxalactam, aztreonam, gentamicin, and kanamycin that was PAO1. The changes in susceptibilities of type B mutants were greater than those of type A mutants. The susceptibilities of both type A and type B mutants were restored to the level of PAO1 by transformation with plasmid pNF111, which contained the wild-type nfxB gene, demonstrating that they are NfxB mutants. Immunoblot analysis with a monoclonal antibody to OprJ revealed that type B mutants produced larger amounts of outer membrane protein OprJ than did type A mutants and that PAO1 produced an undetectable amount of it. Moreover, transconjugants obtained with the different types of NfxB mutants as the donor strains showed almost the same phenotypes as the corresponding donor strains. These results suggest that there are at least two nfxB mutations that show different phenotypes and that production of OprJ is associated with changes in susceptibilities of NfxB mutants.
Molecular characterization of the BRO beta-lactamase of Moraxella (Branhamella) catarrhalis
Authors: Bootsma H J , van Dijk H , Verhoef J , Fleer A , Mooi F R
Published: October 2018

A rapid increase in the prevalence of beta-lactamase-producing Moraxella (Branhamella) catarrhalis strains has been noticed during the last decades. Today, more than 80% of strains isolated worldwide produce beta-lactamase. To investigate beta-lactamase(s) of M. catarrhalis at the molecular level, the BRO-1 beta-lactamase gene (bla) was isolated as part of a 4,223-bp HindIII fragment. Sequence analysis indicated that bla encodes a polypeptide of 314 amino acid residues. Insertional inactivation of bla in M. catarrhalis resulted in complete abrogation of beta-lactamase production and ampicillin resistance, demonstrating that bla is solely responsible for beta-lactam resistance. Comparison with other beta-lactamases suggested that M. catarrhalis beta-lactamase is a unique enzyme with conserved residues at the active sites. The presence of a signal sequence for lipoproteins suggested that it is lipid modified at its N terminus. In keeping with this assumption was the observation that 10% of beta-lactamase activity was found in the membrane compartment of M. catarrhalis. M. catarrhalis strains produce two types of beta-lactamase, BRO-1 and BRO-2, which differ in their isoelectric points. The BRO-1 and BRO-2 genes from two ATCC strains of M. catarrhalis were sequenced, and only one amino acid difference was found between the predicted products. However, there was a 21-bp deletion in the promoter region of the BRO-2 gene, possibly explaining the lower level of production of BRO-2. The G + C content of bla (31%) was significantly lower than those of the flanking genes (47 and 50%), and the overall G + C content of the M. catarrhalis genome (41%). These results indicate that bla was acquired by horizontal gene transfer from another, still unknown species.
Clinical strain of Staphylococcus aureus inactivates and causes efflux of macrolides
Authors: Wondrack L , Massa M , Yang B V , Sutcliffe J
Published: October 2018

Searching through a collection of 124 Staphylococcus aureus clinical strains, we found one isolate, strain 01A1032, that inactivates 14- and 16-membered macrolides. The products of inactivation were purified from supernatant fluids of cultures exposed to erythromycin for 3 h and were found to be identical to products of inactivation from Escherichia coli strains that encode either an EreA or EreB esterase. Further, strain 01A1032 was shown to be resistant to azithromycin, a 15-membered macrolide, by an alternate mechanism, efflux. Thus, strain 01A1032 harbors determinants encoding an esterase activity that hydrolyzes 14- and 16-membered macrolides and a macrolide efflux system.
Effect of imipenem on monoclonal antibody-mediated protection against Escherichia coli O18K5
Authors: Frasa H , Benaissa-Trouw B , Tavares L , van Kessel K , Hustinx W , Schellekens J , Kraaijeveld K , Verhoef J
Published: October 2018

Flow cytometry revealed that the binding of immunoglobulin M monoclonal antibodies (MAbs) to Escherichia coli O18K5 was modulated by exposure of the bacteria to subinhibitory concentrations of imipenem. The binding of anti-K5 MAb was decreased, while the binding of anti-O18 MAb was increased. In addition, anti-lipid A MAbs bound only to imipenem-treated bacteria. The biological effect of MAb binding was investigated in BALB/c mice by determination of the levels of bacteremia, tumor necrosis factor (TNF) in serum and survival after intraperitoneal challenge with bacteria preincubated with MAb. Neither MAb alone (150 micrograms per animal) proved to be protective against untreated bacteria. Anti-lipid A MAb on its own, in contrast to anti-K5 and anti-O18 MAbs, was not protective against imipenem-treated bacteria. Only combinations which included anti-O18 MAb and anti-K5 MAb exerted in mice enhanced protection against smooth E. coli O18K5 as well as imipenem-treated E. coli O18K5. This was reflected by reduced TNF levels in serum and increased survival. The addition of anti-lipid A MAb to the combination of anti-K5 MAb and anti-O18 MAb reduced serum TNF levels in mice, but not significantly.
A novel antiviral agent which inhibits the endonuclease of influenza viruses
Authors: Tomassini J E , Davies M E , Hastings J C , Lingham R , Mojena M , Raghoobar S L , Singh S B , Tkacz J S , Goetz M A
Published: October 2018

A novel anti-influenza virus compound, flutimide, was identified in extracts of a recently identified fungal species, Delitschia confertaspora (F. Pelaez, J.D. Polishook, M. Valldosera, and J.Guarro, Mycotaxon 50:115-122, 1994). The compound, a substituted 2,6-diketopiperazine, selectively inhibited the cap-dependent transcriptase of influenza A and B viruses and had no effect on the activities of other polymerases. Similar to the 4-substituted 2,4-dioxobutanoic acids, a series of transcriptase inhibitors which we described previously (J. Tomassini, H. Selnick, M.E. Davies, M.E. Armstrong, J. Baldwin, M. Bourgeois, J.Hastings, D. Hazuda, J. Lewis, W. McClements, G. Ponticello, E. Radzilowski, G. Smith, A. Tebben, and A. Wolfe, Antimicrob. Agents Chemother. 38:2827-2837, 1994), this inhibitor, which is a natural product, affected neither the initiation nor the elongation of influenza virus mRNA synthesis, but it specifically targeted the cap-dependent endonuclease of the transcriptase. Additionally, the compound was inhibitory to the replication of influenza A and B viruses in cell culture. The selective antiviral properties of this compound further demonstrate the utility of influenza virus endonuclease as a target of antiviral agents.
Effect of recombinant human gamma interferon on intracellular activities of antibiotics against Listeria monocytogenes in the human macrophage cell line THP-1
Authors: Scorneaux B , Ouadrhiri Y , Anzalone G , Tulkens P M
Published: October 2018

Listeria monocytogenes is a facultative intracellular pathogen which enters cells by endocytosis and reaches phagolysosomes from where it escapes and multiplies in the cytosol of untreated cells. Exposure of macrophages to gamma interferon (IFN-gamma) restricts L. monocytogenes to phagosomes and prevents its intracellular multiplication. We have tested whether IFN-gamma also modulates the susceptibility of L. monocytogenes to antibiotics. We selected drugs from three different classes displaying marked properties concerning their cellular accumulation and subcellular distribution, namely, ampicillin (not accumulated by cells but present in cytosol), azithromycin (largely accumulated by cells but mostly restricted to lysosomes), and sparfloxacin (accumulated to a fair extent but detected only in cytosol). We used a continuous line of myelomonocytic cells (THP-1 macrophages), which display specific surface receptors for IFN-gamma, and examined the activity of these antibiotics against L. monocytogenes Hly+ (virulent variant) and L. monocytogenes Hly- (a nonvirulent variant defective in hemolysin production). Untreated THP-1 and phorbol myristate acetate-differentiated THP-1 were permissive for infection and multiplication of intracellular L. monocytogenes Hly+ (virulent variant). All three antibiotics tested were bactericidal against this Listeria strain when added to an extracellular concentration of 10x their MIC. After preexposure of THP-1 to IFN-gamma, L. monocytogenes Hly+ was still phagocytosed but no longer grew intracellularly. The activity of ampicillin became almost undetectable (antagonistic effect), and that of azithromycin was unchanged (additive effect with that of IFN-gamma), whereas that of sparfloxacin was markedly enhanced (synergy). A similar behavior (lack of bacterial growth, associated with a loss of activity of ampicillin, an enhanced activity of sparfloxacin, and unchanged activity of azithromycin) was observed in cells infected with L. monocytogenes Hly-. This modulation of antibiotic activity, which we ascribe to the change of subcellular localization of L. monocytogenes caused by IFN-gamma or by the lack of virulence factor, could result from a change in bacterial responsiveness to antibiotics, a modification of the drug activity, or differences in drug bioavailabilities between cytosol and phagosomes.
Sequence and characterization of a novel chromosomal aminoglycoside phosphotransferase gene, aph (3')-IIb, in Pseudomonas aeruginosa
Authors: Hächler H , Santanam P , Kayser F H
Published: October 2018

A novel, probably chromosomally encoded, aminoglycoside phosphotransferase gene was cloned on a 2,996-bp PstI fragment from Pseudomonas aeruginosa and designated aph (3')-IIb. It coded for a protein of 268 amino acids that showed 51.7% amino acid identity with APH (3')-II [APH(3') is aminoglycoside-3' phosphotransferase] from Tn5. Two other open reading frames on the cloned fragment showed homology to a signal-transducing system in P. aeruginosa.
Directly repeated insertion of 9-nucleotide sequence detected in penicillin-binding protein 2B gene of penicillin-resistant Streptococcus pneumoniae
Authors: Yamane A , Nakano H , Asahi Y , Ubukata K , Konno M
Published: October 2018

We investigated the molecular mechanism of 50 penicillin-resistant Streptococcus pneumoniae strains (penicillin: MIC, > or = 0.125 microgram/ml) having neither class A nor class B mutations in the penicillin-binding protein 2B gene (pbp2b). An analysis of the nucleotide sequences of the pbp2b genes from seven strains revealed an unique direct repeat of 9 nucleotides (TGGTATACT) between active-site serine (residue 385) and Ser-X-Asn (residues 442 to 444) motifs. The same insertion was detected in 13 strains.
Increasing antibiotic resistance in clinical isolates of Aeromonas strains in Taiwan
Authors: Ko W C , Yu K W , Liu C Y , Huang C T , Leu H S , Chuang Y C
Published: October 2018

A total of 234 clinical isolates of Aeromonas, primarily A. hydrophila, were collected for the present study. Most were isolates from blood. By the agar dilution method, more than 90% of the Aeromonas strains were found to be susceptible to moxalactam, ceftazidime, cefepime, aztreonam, imipenem, amikacin, and fluoroquinolones, but they were more resistant to tetracycline, trimethoprim-sulfamethoxazole, some extended-spectrum cephalosporins, and aminoglycosides than strains from the United States and Australia.
In vitro activities of semisynthetic pneumocandin L-733,560 against fluconazole-resistant and -susceptible Candida albicans isolates
Authors: Martinez-Suarez J V , Rodriguez-Tudela J L
Published: October 2018

Lipopeptide L-733,560 is a water-soluble derivative of pneumocandin B0 that exhibits enhanced anti-Candida activity. We investigated the in vitro activity of L-733,560 compared with those of amphotericin B, flucytosine, and itraconazole, against fluconazole-resistant (n = 44) and fluconazole-susceptible (n = 46) Candida albicans isolates. Tests were performed with a photometer-read broth microdilution method with RPMI-2% glucose and National Committee for Clinical Laboratory Standards reference strains. Except for those of itraconazole, MICs were not significantly different between the two groups of isolates, as expected for agents with different mechanisms of action. L-733,560 was the most active agent against C.albicans, with MICs for 50 and 90% of the strains tested of 0.01 and 0.06 microgram/ml, respectively.
Trophozoite elimination in a rat model of Pneumocystis carinii pneumonia by clinically achievable plasma deferoxamine concentrations
Authors: Merali S , Chin K , Grady R W , Clarkson A B
Published: October 2018

In a rat model of Pneumocystis carinii pneumonia, a 3-week infusion of deferoxamine producing concentrations in plasma of > or = 1.5 micrograms m-1 eliminated the trophozoite life cycle stage. Since this concentration is well below that routinely achieved in patients treated for iron overload, deferoxamine has promise as a therapy for AIDS-associated P.carinii pneumonia.
In vitro and in vivo activities of SCH 56592 against Blastomyces dermatitidis
Authors: Sugar A M , Liu X P
Published: October 2018

The new triazole derivative SCH 56592 has been tested in a National Committee for Clinical Laboratory Standards-adapted in vitro susceptibility test, and its activity against 12 isolates of Blastomyces dermatitidis yeast-like forms has been compared with those of amphotericin B, itraconazole, and fluconazole. SCH 56592 was the most active of the four compounds, with an MIC at which 90% of the isolates are inhibited of 0.06 microgram/ml and a minimal fungicidal concentration at which 90% of the isolates are inhibited of 4 micrograms/ml. The results of the treatment of mice infected with B. dermatitidis with three different doses of SCH 56592 (25, 5, or 1 mg/kg of body weight), amphotericin B (1 mg/kg), or itraconazole (150 mg/kg) confirmed the potent activity of SCH 56592. Survival was prolonged at each dose of SCH 56592, and sterilization of the lungs occurred in the high-dose group but not in the groups treated with itraconazole or fluconazole. SCH 56592 is a promising new azole antifungal drug that should be studied in humans with blastomycosis.
Pyrimethamine pharmacokinetics in human immunodeficiency virus-positive patients seropositive for Toxoplasma gondii
Authors: Jacobson J M , Davidian M , Rainey P M , Hafner R , Raasch R H , Luft B J
Published: October 2018

Pyrimethamine pharmacokinetics were studied in 11 human immunodeficiency virus (HIV)-positive patients who were seropositive for exposure to Toxoplasma gondii and were taking zidovudine (AIDS Clinical Trials Group Protocol 102). Pyrimethamine was administered at 50 mg daily for 3 weeks to achieve steady state, and pharmacokinetic profiles were determined after administration of the last dose. Noncompartmental and compartmental analyses were performed. Population pharmacokinetic analysis assuming a one-compartment model yielded the following estimates: area under the 24-h concentration-time curve, 42.7 +/- 12.3 micrograms.h/ml; halflife, 139 +/- 34 h; clearance, 1.28 +/- 0.41 liters/h; volume of distribution, 246 +/- 641; and absorption rate constant, 1.5 +/- 1.3 liters/h. These values are similar to those seen in subjects without HIV infection. Pyrimethamine pharmacokinetics did not differ significantly in those subjects who were intravenous drug users. Adverse effects were noted in 73% of those initially enrolled in this study, leading to discontinuation for 38%. No association was noted between pyrimethamine levels and the incidence of adverse events. No significant differences were seen in zidovudine pharmacokinetic parameters obtained from studies performed before and during treatment with pyrimethamine. In summary, pyrimethamine exhibited pharmacokinetics in HIV-infected patients that were similar to those in non-HIV-infected subjects and it did not alter the pharmacokinetics of zidovudine in these patients.
6,7-disubstituted 2,4-diaminopteridines: novel inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase
Authors: Jackson H C , Biggadike K , McKilligin E , Kinsman O S , Queener S F , Lane A , Smith J E
Published: October 2018

Four novel, disubstituted diaminopteridines have been identified which antagonize the uptake of a folate precursor (para-aminobenzoic acid) by rat-derived Pneumocystis carinii maintained in short-term axenic culture at concentrations ranging from 4.5 to 26 microM. The compounds were at least 10 to 100 times more active than trimethoprim in this assay. None of these entities exhibited toxicity to mammalian cell lines at < 100 microM. The same structures also caused significant inhibition of Toxoplasma gondii tachyzoite replication within Madin-Darby bovine kidney cells at concentrations ranging from 0.1 to 10 microM. Three of the structures (GR92754, AH10639, and AH2504) were at least an order of magnitude more potent than the standard anti-T. gondii agent, pyrimethamine. All three entities were also significantly more potent and selective than pyrimethamine as inhibitors of T. gondii dihydrofolate reductase (DHFR), with 50% inhibitory concentrations within the range of 0.018 to 0.033 microM. One of these compounds, 6,7-dibutyl-2,4-diaminopteridine (GR92754), was also a potent and selective inhibitor of P. carinii DHFR (50% inhibitory concentration, 0.082 microM). GR92754 is the first DHFR inhibitor described that exhibits greater potency, selectivity, and intracellular activity against both organisms than any of the DHFR agents used clinically, namely, trimethoprim, pyrimethamine, and trimetrexate. This information could provide the starting point for examination of the pharmacokinetic and therapeutic potential of GR92754 and related chemical entities with animal models.
Antibacterial activities of epiroprim, a new dihydrofolate reductase inhibitor, alone and in combination with dapsone
Authors: Locher H H , Schlunegger H , Hartman P G , Angehrn P , Then R L
Published: October 2018

Epiroprim (EPM; Ro 11-8958) is a new selective inhibitor of microbial dihydrofolate reductase. EPM displayed excellent activity against staphylococci, enterococci, pneumococci, and streptococci which was considerably better than that of trimethoprim (TMP). EPM was also active against TMP-resistant strains, although the MICs were still relatively high. Its combination with dapsone (DDS) was synergistic and showed as in vitro activity superior to that of the TMP combination with sulfamethoxazole (SMZ). The EPM-DDS (ratio, 1:19) combination inhibited more than 90% of all important gram-positive pathogens at a concentration of 2 + 38 micrograms/ml. Only a few highly TMP-resistant staphylococci and enterococci were not inhibited. EPM was also more active than TMP against Moraxella catarrhalis, Neisseria meningitidis, and Bacteroides spp., but it was less active than TMP against all other gram-negative bacteria tested. Atypical mycobacteria were poorly susceptible to EPM, but the combination with DDS was synergistic and active at concentrations most probably achievable in biological fluids (MICs from 0.25 +/- 4.75 to 4 + 76 micrograms/ml). EPM and the EPM-DDS combination were also highly active against experimental staphylococcal infections in a mouse septicemia model. The combination EPM-DDS has previously been shown to exhibit activity in Pneumocystis carinii and Toxoplasma models and, as shown in the present study, also shows good activity against a broad range of bacteria including many strains resistant to TMP and TMP-SMZ.
Comparison of D0870, a new triazole antifungal agent, to fluconazole for inhibition of Candida albicans cytochrome P-450 by using in vitro assays
Authors: Venkateswarlu K , Denning D W , Manning N J , Kelly S L
Published: October 2018

D0870 was 12 to 15 times more active than fluconazole in experiments to determine the MIC for growth arrest for two isolates of Candida albicans. A biochemical comparison of in vitro sterol biosynthesis in cell extracts showed only a twofold superiority of D0870 over fluconazole. A large differentiation (10-fold) in 50% saturating concentrations obtained by examining the binding of the azoles to microsomal P-450 was observed in a type II binding spectrophotometric assay, possibly reflecting the differential affinity for more than one P-450 enzyme. Additional mechanisms besides affinity for the target enzyme sterol 14 alpha-demethylase, such as differential intracellular accumulation of drug, may contribute to the differences in antifungal activity.
Bisbenzylisoquinolines as modulators of chloroquine resistance in Plasmodium falciparum and multidrug resistance in tumor cells
Authors: Frappier F , Jossang A , Soudon J , Calvo F , Rasoanaivo P , Ratsimamanga-Urverg S , Saez J , Schrevel J , Grellier P
Published: October 2018

Ten naturally occurring bisbenzylisoquinolines (BBIQ) and two dihydro derivatives belonging to five BBIQ subgroups were evaluated in vitro for their ability to inhibit Plasmodium falciparum growth and, in drug combination, to reverse the resistance to chloroquine of strain FcB1. The same alkaloids were also assessed in vitro for their potentiating activity against vinblastine with the multidrug-resistant clone CCRF-CEM/VLB, established from lymphoblastic acute leukemia. Three of the BBIQ tested had 50% inhibitory concentrations of less than 1 microM. The most potent antimalarial agent was cocsoline (50% inhibitory concentration, 0.22 microM). Regarding the chloroquine-potentiating effect, fangchinoline exhibited the highest biological activity whereas the remaining compounds displayed either antagonistic or slight synergistic effects. Against the multidrug-resistant cancer cell line, fangchinoline was also by far the most active compound. Although there were clear differences between the activities of tested alkaloids, no relevant structure-activity relationship could be established. Nevertheless, fangchinoline appears to be a new biochemical tool able to help in the comprehension of the mechanism of both chloroquine resistance in P. falciparum and multidrug resistance in tumor cells.
Bacteriostatic and bactericidal activities of benzoxazinorifamycin KRM-1648 against Mycobacterium tuberculosis and Mycobacterium avium in human macrophages
Authors: Mor N , Simon B , Heifets L
Published: October 2018

Inhibitory and bactericidal activities of KRM-1648 were determined against Mycobacterium tuberculosis and M. avium residing in human monocyte-derived macrophages and extracellular M. tuberculosis and M. avium. MICs and MBCs of KRM-1648 against intracellular and extracellular bacteria were substantially lower than those of rifampin. The MICs and MBCs of either drug against the intracellular bacteria were only twofold lower than or equal to the values found for extracellular bacteria. The prolonged effect of KRM-1648 found in this study is probably associated with high ratios of intracellular accumulation, which were 50- to 100-fold higher than that found for rifampin. Further studies on intracellular distribution of KRM-1648 and on the sites of actual interaction between the drug and bacteria residing in macrophages are necessary, as well as evaluation of combined effects of KRM-1648 with other drugs in long-term macrophage culture experiments.
In vitro and in vivo evaluations of LB20304, a new fluoronaphthyridone
Authors: Oh J I , Paek K S , Ahn M J , Kim M Y , Hong C Y , Kim I C , Kwak J H
Published: October 2018

In vitro activity of LB20304 against 1,231 clinical isolates was evaluated and compared with those of ciprofloxacin, sparfloxacin, lomefloxacin, and ofloxacin. LB20304 demonstrated the most potent activity against gram-positive bacteria. It was 32- to 64-fold more active than ciprofloxacin against methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus, methicillin-resistant Staphylococcus epidermidis, and Streptococcus pneumoniae (penicillin G resistant). LB20304 was also highly active against most members of the family Enterobacteriaceae. Its activity was more potent than those of sparfloxacin, ofloxacin, and lomefloxacin and comparable to that of ciprofloxacin. The protective activities of LB20304 against systemic infections caused by gram-positive bacteria in mice were superior to those of ciprofloxacin and sparfloxacin. Against infections by gram-negative bacteria, LB20304 was slightly less active than ciprofloxacin.
Prevalence of resistance to three fluoroquinolones: assessment of levofloxacin disk test error rates and surrogate predictors of levofloxacin susceptibility. AST Surveillance Group
Authors: Fuchs P C , Barry A L , Brown S D
Published: October 2018

More than 3,000 consecutive clinical bacterial isolates from 10 U.S. medical centers were subjected to standard broth microdilution and disk diffusion tests to determine their susceptibilities to levofloxacin, ofloxacin, D-ofloxacin, and ciprofloxacin. Levofloxacin was confirmed to be twice as active as ofloxacin and to have activity comparable to that of ciprofloxacin, with minor variations in activity against some species. The prevalence of resistant isolates was 7.1% to levofloxacin, 9.3% to ciprofloxacin, and 11.2% to ofloxacin. The susceptibilities of some species to the quinolones were less than those reported in previous studies. Pseudomonas aeruginosa isolates had the greatest variability in their susceptibilities to the three drugs between the participating centers. Two proposed zone size breakpoints for levofloxacin disk tests yielded similar low error rates. Ofloxacin and ciprofloxacin susceptibility test results correlated reasonably well with those of levofloxacin and could be used as surrogate indicators of levofloxacin susceptibility, but that resulted in some serious errors, and thus, direct testing of levofloxacin susceptibility is preferable. Replicate testing of standard quality control strains confirmed the established and proposed quality control parameters for all three quinolones tested.