bluuebunny/crossref_metadata_2025 huggingface dataset:
Purification and characterization of a new beta-lactamase from Clostridium butyricum
Authors: Kesado T , Lindqvist L , Hedberg M , Tunér K , Nord C E
Published: June 2012

A highly penicillin-resistant beta-lactamase-producing strain of Clostridium butyricum, strain NBL 3, was isolated. The specific activity of the unpurified beta-lactamase was 0.29 U/mg of protein. The enzyme was purified 1,130-fold by QAE Zetaprep, Sephacryl S-300, and Mono Q column passages. The purified enzyme was judged homogeneous by sodium dodecyl sulfate gradient gel electrophoresis and fast protein liquid chromatography. The enzyme hydrolyzed phenoxymethylpenicillin, benzylpenicillin, ampicillin, and carbenicillin more rapidly than piperacillin and cephaloridine. Cephalothin, cephalexin, cefoxitin, moxalactam, cefotaxime, and imipenem were only slightly hydrolyzed, at less than 1% the rate for phenoxymethylpenicillin. The enzyme was inhibited by clavulanic acid, sulbactam, tazobactam, and p-chloromercuribenzoate. The molecular weight was determined by gel filtration and sodium dodecyl sulfate gradient gel electrophoresis to be 32,000. The isoelectric point was 4.4. Aspartic acid-asparagine, glutamic acid-glutamine, leucine, lysine, alanine, and serine dominated the amino acid composition.
Cross-resistance to fluoroquinolones in multiple-antibiotic-resistant (Mar) Escherichia coli selected by tetracycline or chloramphenicol: decreased drug accumulation associated with membrane changes in addition to OmpF reduction
Authors: Cohen S P , McMurry L M , Hooper D C , Wolfson J S , Levy S B
Published: June 2012

Chromosomal multiple-antibiotic-resistant (Mar) mutants of Escherichia coli, selected on agar containing low concentrations of tetracycline or chloramphenicol, were 6- to 18-fold less susceptible to the fluoroquinolones than were their wild-type E. coli K-12 or E. coli C parental strains. The frequency of emergence of such mutants was at least 1,000-fold higher than that of those selected by the fluoroquinolone norfloxacin directly. When Mar mutants, but not wild-type cells, were plated on norfloxacin, mutants resistant to high levels of norfloxacin (2 micrograms/ml) appeared at a relatively high (approximately 10(-7] frequency. In addition to decreased amounts of OmpF, Mar mutants had other outer membrane protein changes and were four- to eightfold less susceptible to fluoroquinolones than was an ompF::Tn5 mutant lacking only OmpF. Accumulation of [3H]norfloxacin was more than threefold lower in the Mar mutants than in wild-type cells and twofold lower than in the OmpF-deficient derivative. These differences were not attributable to a change in the endogenous active efflux system for norfloxacin in E. coli. Norfloxacin-induced inhibition of DNA synthesis was threefold lower in intact cells of a Mar mutant than in susceptible cells, but this difference was not seen in toluene-permeabilized cells. Insertion of Tn5 into marA (min 34.05 on the chromosome) led to a return of the wild-type patterns of norfloxacin accumulation, fluoroquinolone and other antimicrobial agent susceptibilities, and outer membrane protein profile, including partial restoration of OmpF. These findings together suggest that marA-dependent fluoroquinolone resistance is linked to decreased cell permeability, only part of which can be accounted for by the reduction in OmpF. Once mutated to marA, cells can achieve high levels of quinolone resistance at a relatively high frequency.
Teicoplanin in the treatment of gram-positive-bacterial endocarditis
Authors: Martino P , Venditti M , Micozzi A , Brandimarte C , Gentile G , Santini C , Serra P
Published: June 2012

Intravenous teicoplanin has been used to treat 23 cases of gram-positive-bacterial endocarditis, usually with 3 to 7 mg/kg every 12 h on the first day, followed by 3 to 7 mg/kg every 24 h. For some cases (staphylococcal and enterococcal endocarditis), the dosage was 8 to 14.4 mg/kg per day and/or other antibiotics were given. The mean duration was 48.2 days (range, 23 to 130 days). Of 23 patients, 21 (91.3%) had negative cultures or were cured. A total of 18 patients were treated with teicoplanin alone; of these, 4 had surgery, and all (except 2 who relapsed) were cured. Teicoplanin was combined with one or more antibiotics in five cases; in all cases appropriate cultures were negative, but three patients died during therapy or follow-up. Mild renal impairment was seen in two patients; both were receiving teicoplanin in combination with an aminoglycoside. We conclude that intravenous teicoplanin administered once a day at doses of 7 to 14 mg/kg per day is well tolerated, easy to administer, and may represent an efficacious therapy for gram-positive-bacterial endocarditis.
Nomenclature for tetracycline resistance determinants
Authors: Levy S B , McMurry L M , Burdett V , Courvalin P , Hillen W , Roberts M C , Taylor D E
Published: June 2012

Tetracycline resistance determinants are widespread and distinguishable genetically and biochemically. The nomenclature for this increasing number of determinants has been varied and inconsistent. This communication suggests ways of naming these determinants and their genes and gene products consistent with current genetic terminology.
Continuous infusion of high-dose acyclovir for serious herpesvirus infections
Authors: Fletcher C V , Englund J A , Bean B , Chinnock B , Brundage D M , Balfour H H
Published: June 2012

Thirteen patients with herpesvirus infections who were unresponsive to at least 72 h of intermittent acyclovir administration received high-dose continuous infusion. Steady-state concentrations were maintained at between 20 and 98 mumol/liter. Of 12 patients who had continuous infusion for greater than 5 days, 7 (58%) resolved their infections, as determined by clinical and virologic parameters, suggesting that continuous infusion may succeed in some patients who do not respond to conventional therapy.
In vitro activities of lomefloxacin and temafloxacin against pathogens causing diarrhea
Authors: Segreti J , Nelson J A , Goodman L J , Kaplan R L , Trenholme G M
Published: June 2012

The in vitro activities of temafloxacin (A63004) and lomefloxacin (SC-47111; NY-198) were compared with those of seven other antibiotics against 146 isolates of bacterial enteric pathogens, including Campylobacter jejuni and Campylobacter coli. Ciprofloxacin was the most active drug against the Salmonella, Shigella, Yersinia, and Vibrio spp. tested. Lomefloxacin, temafloxacin, and difloxacin were the most active drugs tested against Campylobacter spp. (MIC for 90% of strains, 0.125 to 0.25 micrograms/ml).
Cell surface changes in Pseudomonas aeruginosa PAO4069 in response to treatment with 6-aminopenicillanic acid
Authors: Godfrey A J , Bryan L E
Published: June 2012

Pseudomonas aeruginosa PAO4096 was induced for beta-lactamases with 6-aminopenicillanic acid. Surface changes concomitant with beta-lactamase induction were monitored. The surface hydrophobicity of the culture increased during exposure to 6-aminopenicillanic acid. The increase was associated with a change in the distribution of the O antigen in the lipopolysaccharide of treated cells. The hydrophobicity change was reversible and partially inhibited by depressed protein synthesis. The susceptibility of induced cells to rifampin was increased transiently, suggesting increased permeability of the induced cells.
Comparison of in vivo activity of fluconazole with that of amphotericin B against Candida tropicalis, Candida glabrata, and Candida krusei
Authors: Fisher M A , Shen S H , Haddad J , Tarry W F
Published: June 2012

Fluconazole (UK-49,858) is a new oral bis-triazole antifungal agent with demonstrated activity against Candida albicans. Because of the increasing importance of infections due to other species of Candida, we studied the efficacy of fluconazole in a rat model of established systemic candidiasis, using clinical isolates of C. tropicalis, C. glabrata, and C. Krusei. In normal rats, oral fluconazole at both 20 and 80 mg/kg per day for 7 days reduced both kidney and liver titers of C. tropicalis and C. glabrata compared with those in control animals and was only slightly inferior to amphotericin B. Both fluconazole and amphotericin B were ineffective in reducing kidney titers of C. krusei, but amphotericin B was more effective than fluconazole in reducing liver titers. Fluconazole showed no increased efficacy at the higher dose of 80 mg/kg per day compared with 20 mg/kg per day in any experiment. These results suggest that oral fluconazole may be useful in the treatment of established disseminated candidiasis caused by species other than C. albicans. Further in vivo studies are needed, however, to define minimum effective doses and length of therapy and to test additional Candida isolates.
Novel plasmid-mediated beta-lactamase (TEM-10) conferring selective resistance to ceftazidime and aztreonam in clinical isolates of Klebsiella pneumoniae
Authors: Quinn J P , Miyashiro D , Sahm D , Flamm R , Bush K
Published: June 2012

Two clinical isolates of Klebsiella pneumoniae from seriously ill patients in Chicago, Ill., have been identified as resistant to ceftazidime and aztreonam but susceptible to other cephalosporins. This unusual antibiogram was shown to be due to a novel plasmid-mediated beta-lactamase which readily hydrolyzed ceftazidime and aztreonam in addition to penicillins such as piperacillin and carbenicillin. This enzyme and its attendant resistance were transferred to Escherichia coli by conjugation on a 50-kilobase plasmid. Isoelectric focusing revealed a single beta-lactamase band with a molecular weight of 29,000 and an isoelectric point of 5.57 in the resistant isolates and transconjugants. The beta-lactamase inhibitors clavulanic acid and sulbactam restored beta-lactam susceptibility in the resistant isolates. Fifty percent inhibitory concentrations of clavulanic acid and sulbactam were 4.4 and 940 nM, respectively. DNA hybridization studies indicated that this enzyme, designated TEM-10, is related to well-established TEM-type beta-lactamases. However, the TEM-10 enzyme was inhibited by p-chloromercuribenzoate, in contrast to TEM-2 beta-lactamase. On the basis of substrate and inhibition profiles, the TEM-10 enzyme could be easily discriminated from TEM-5 and RHH-I beta-lactamases.
Efficacy of cefmetazole in the treatment of active syphilis in the rabbit model
Authors: Baker-Zander S A , Lukehart S A
Published: June 2012

Cefmetazole, a cephamycin-type antibiotic, was shown to be as effective as standard benzathine penicillin for therapy of active syphilis in the rabbit model. Four groups of six adult male rabbits were inoculated intradermally with 10(6) Treponema pallidum per site, producing primary syphilitic lesions. One week following infection, groups of rabbits were treated with benzathine penicillin (200,000 U intramuscularly weekly for 2 weeks) or cefmetazole (20 or 40 mg/kg per day intramuscularly in four divided doses for 15 days); one group was untreated. Daily dark-field microscopic examination of lesion aspirates demonstrated that the mean times to dark-field negativity were the same for benzathine penicillin- and two cefmetazole-treated groups (1.0. 1.0, and 1.17 days, respectively), while all untreated animals remained dark-field positive for greater than 15 days. Mean maximum lesion diameters in cefmetazole-treated animals (8.7 +/- 1.3 and 8.1 +/- 1.3 mm) were equivalent to those in penicillin-treated animals (8.6 +/- 1.6 mm) and were smaller than observed in untreated animals (12.4 +/- 2.2 mm; P less than 0.01); fewer lesions ulcerated in penicillin- or cefmetazole-treated rabbits than in untreated rabbits (P less than 0.001). Persistent infection was documented in lymph nodes of untreated rabbits; no evidence of latent infection was found in penicillin- or cefmetazole-treated animals.
Pharmacokinetics of ampicillin (2.0 grams) and sulbactam (1.0 gram) coadministered to subjects with normal and abnormal renal function and with end-stage renal disease on hemodialysis
Authors: Blum R A , Kohli R K , Harrison N J , Schentag J J
Published: June 2012

The single-dose pharmacokinetics of intravenously administered ampicillin (2.0 g) and sulbactam (1.0 g) were studied in normal subjects and in patients with various degrees of creatinine clearance (CLCR). Six normal subjects (CLCR, greater than 60 ml/min), six patients with mild renal failure (CLCR, 31 to 60 ml/min), four patients with severe renal failure (CLCR, 7 to 30 ml/min), and four patients requiring maintenance hemodialysis (CLCR, less than 7 ml/min) were studied. The terminal half-lives for ampicillin and sulbactam more than doubled in patients with severe renal failure compared with subjects with normal renal function and mild renal insufficiency. CLCR significantly correlated with ampicillin (r = 0.88) and sulbactam (r = 0.54) total body clearance. Mean steady-state volume of distribution and nonrenal clearance for ampicillin and sulbactam were not affected by renal function. Hemodialysis approximately doubled the ampicillin and sulbactam total body clearance. Mean totals of 34.8 +/- 4.0% of the ampicillin dose and 44.7 +/- 3.2% of the sulbactam dose were removed during a 4-h hemodialysis treatment. A slight rebound in concentrations in serum after hemodialysis was observed for both drugs in all four subjects. In hemodialysis patients, the ampicillin half-life was 17.4 +/- 8.0 h and the sulbactam half-life was 13.4 +/- 7.4 h. The ampicillin and sulbactam half-lives were appreciably altered during the hemodialysis period (means of 2.2 and 2.3 h, respectively). The nearly parallel decrease in total body clearance, with volume of distribution and nonrenal clearance remaining relatively constant, suggests that the same ratio of ampicillin to sulbactam is appropriate regardless of renal function. An adjustment of the ampicillin (2.0 g) and sulbactam (1.0 g) dose to twice daily would be appropriate in patients with a CLCR between 7 and 30 ml/min. Doses should be given every 24 h for those undergoing maintenance hemodialysis. On hemodialysis days, doses should be given after hemodialysis.
Susceptibility of human immunodeficiency virus type 1 replication in vitro to acyclic adenosine analogs and synergy of the analogs with 3'-azido-3'-deoxythymidine
Authors: Smith M S , Brian E L , De Clercq E , Pagano J S
Published: June 2012

The replication of human immunodeficiency virus in vitro is inhibited by some acyclic adenosine derivatives, such as 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)-2,6-diaminopurine [(S)-HPMPDAP], as well as by 3'-azido-3'-deoxythymidine (AZT). In a human T-lymphocyte cell line, C3, at 6 days postinfection, the 50% effective concentration (EC50) of AZT was 0.02 microM and the 90% effective concentration (EC90) was 0.33 microM; for PMEA, the EC50 was 1.9 microM and the EC90 was 27 microM. For (S)-HPMPDAP, the EC50 was 2.3 microM and the EC90 was 36 microM. Most combinations of AZT and PMEA produced a synergistic effect. In the T-cell line C3, the combination indices for 50 to 90% inhibition of virus replication ranged from 0.25 to 1.25. Combinations of PMEA (or other members of this group) with AZT appear to be worth further study for the possible treatment of acquired immunodeficiency syndrome.
Broad-spectrum in vivo antiviral activity of 7-thia-8-oxoguanosine, a novel immunopotentiating agent
Authors: Smee D F , Alaghamandan H A , Cottam H B , Sharma B S , Jolley W B , Robins R K
Published: June 2012

A novel immunopotentiating agent, 5-amino-3-beta-D-ribofuranosylthiazolo [4,5-d]pyrimidine-2,7(3H,6H)-dione (7-thia-8-oxoguanosine), lacks virus-inhibitory properties in vitro but induces interferon and potentiates immune functions, such as natural killer cell activity. It was evaluated in rodent models to determine the spectrum of antiviral activity and effective treatment regimens. At 50 to 200 mg/kg given as single or divided intraperitoneal (i.p.) doses 1 day before virus inoculation, significant protection was afforded to mice infected i.p. with Semliki Forest, San Angelo, banzi, and encephalomyocarditis viruses. Similarly, suckling rats were protected from an intranasal challenge with rat coronavirus. Against San Angelo virus, treatments could be delayed to 1 day post-virus inoculation and still show a beneficial effect. The compound was moderately effective in mice infected i.p. with herpes simplex virus type 2 or intranasally with vesicular stomatitis virus. No activity was seen against influenza B virus in mice when the analog was administered one time pre-virus inoculation or in multiple doses given before and after the virus inoculation. Nor was there a prophylactic effect against herpetic skin lesions on mice. This immune modulator may have promise for the treatment of a variety of virus infections.
Effects of the immunomodulating agent R837 on acute and latent herpes simplex virus type 2 infections
Authors: Bernstein D I , Harrison C J
Published: June 2012

R837 is an immune modulator with no in vitro activity against herpes simplex virus (HSV). We evaluated topical R837 as therapy for genital HSV type 2 infection using the guinea pig model of this disease. Furthermore, we investigated the effect of R837 therapy on acute and latent neural HSV infections. Therapy initiated 12 h after viral inoculation and given twice a day significantly reduced the acute neural infection so that HSV was recovered from only 1 of 64 neural tissue specimens obtained from R837 recipients compared with 43 of 56 specimens obtained from placebo recipients (P less than 0.0001). R837 initiated 36 h after HSV inoculation and given once a day also significantly reduced the total mean lesion score of the acute disease from 14.1 +/- 4.3 to 2.6 +/- 5.3 (P less than 0.0001) and shortened the period of vaginal HSV shedding from 6.9 +/- 1.7 to 3.2 +/- 1.4 days (P less than 0.001). R837-treated animals also developed fewer HSV recurrences than did controls (2.0 +/- 1.7 versus 5.1 +/- 1.7; P less than 0.0002). Latent HSV was detected in 23 of 24 dorsal root ganglia explant cultures from placebo recipients but in only 2 of 30 cultures from R837-treated animals, and HSV in these 2 cultures was detectable only with the addition of a demethylating agent. Topical R837 exhibited in vivo anti-HSV activity, reducing both acute and latent neural infections as well as acute and recurrent genital disease.
Aminoglycoside uptake increased by tet gene expression
Authors: Merlin T L , Davis G E , Anderson W L , Moyzis R K , Griffith J K
Published: June 2012

The expression of extrachromosomal tet genes not only confers tetracycline resistance but also increases the susceptibilities of gram-negative bacteria to commonly used aminoglycoside antibiotics. We investigated the possibility that tet expression increases aminoglycoside susceptibility by increasing bacterial uptake of aminoglycoside. Studies of [3H]gentamicin uptake in paired sets of Escherichia coli HB101 and Salmonella typhimurium LT2 expressing and not expressing tet showed that tet expression accelerates energy-dependent [3H]gentamicin uptake. Increased [3H]gentamicin uptake was accompanied by decreased bacterial protein synthesis and bacterial growth. Increased aminoglycoside uptake occurred whether tet expression was constitutive or induced, whether the tet gene was class B or C, and whether the tet gene was plasmid borne or integrated into the bacterial chromosome. tet expression produced no measurable change in membrane potential, suggesting that tet expression increases aminoglycoside uptake either by increasing the availability of specific carriers or by lowering the minimum membrane potential that is necessary for uptake.
In vitro bactericidal activities of gentamicin, cefazolin, and imipenem in peritoneal dialysis fluids
Authors: Halstead D C , Guzzo J , Giardina J A , Geshan A E
Published: June 2012

Continuous ambulatory peritoneal dialysis is an important modality of therapy for patients with renal disease. However, peritonitis continues to be a major risk factor and is usually treated by intraperitoneal administration of antimicrobial agents. Few data are available concerning the stability of antimicrobial agents in peritoneal dialysis solution beyond 48 h. Our investigation was designed to establish the chemical and biological stability of gentamicin alone and in combination with cefazolin in peritoneal dialysis solution at 6 and 72 h by an immunoassay and by an in vitro bactericidal test against American Type Culture Collection (Rockville, Md.) strains of Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. In addition, uninfected peritoneal dialysis effluent was inoculated with three American Type Culture Collection strains and gentamicin or imipenem. Gentamicin alone or in combination with cefazolin was not altered chemically and was bactericidal for Staphylococcus spp. but not P. aeruginosa. In contrast, imipenem was active against both Staphylococcus spp. and P. aeruginosa. Undefined factors other than inactivation of gentamicin may be responsible for the lack of bactericidal activity and treatment failure of Pseudomonas infections.
Hybridization analysis of three chloramphenicol resistance determinants from Clostridium perfringens and Clostridium difficile
Authors: Rood J I , Jefferson S , Bannam T L , Wilkie J M , Mullany P , Wren B W
Published: June 2012

The chloramphenicol resistance determinant from a nonconjugative strain of Clostridium perfringens was cloned and shown to be expressed in Escherichia coli. Subcloning and deletion analysis localized the resistance gene, catQ, to within a 1.25-kilobase (kb) partial Sau3A fragment. The catQ gene contained internal HindII, HaeIII, and DraI restriction sites and was distinct from the catP gene, which was originally cloned (L. J. Abraham, A. J. Wales, and J. I. Rood Plasmid 14:37-46, 1985) from the conjugative C. perfringens R plasmid, pIP401. Hybridization studies were carried out with a 0.35-kb DraI-P fragment of pJIR260 as an internal catQ-specific probe and a 0.38-kb EcoRV-HinfI fragment of pJIR62 as an internal catP-specific gene probe. The results showed that the catP and catQ genes were not similar and that neither probe hybridized with cat genes from other bacterial genera. However, the catP gene was similar to the cloned catD gene from Clostridium difficile. Comparative studies with both catP and catD probes showed that these genes had significant restriction identity. We therefore suggest that these genes were derived from a common source.
Intrarenal distribution of vancomycin in endotoxemic rats
Authors: Ngeleka M , Auclair P , Tardif D , Beauchamp D , Bergeron M G
Published: June 2012

We previously observed that the intrarenal distribution of aminoglycosides was modified by Escherichia coli endotoxin in the absence of any major renal physiological disturbance or histological changes. In the present study, we evaluated the role of E. coli endotoxin on the intrarenal distribution of vancomycin. At the beginning of the experiment, female Sprague-Dawley rats were infused intravenously with saline (control) or endotoxin (0.25 mg/kg) during 15 min. Thereafter, saline was constantly infused for the following 4 h. Two hours after the beginning of the infusion, animals were injected intravenously with a single dose of vancomycin (20 mg/kg). The drug levels in serum; renal cortex, medulla, and papilla; and urine were evaluated from 0.08 to 24 h after injection. Analysis of the area under the curve of the drug concentration in the different kidney components versus time showed a higher accumulation of vancomycin in the renal cortex and medulla in the endotoxin-infused rats than in the normal rats (P less than 0.01). Endotoxin was associated with an increase in the half-life in serum (P less than 0.01) and a lower elimination rate constant. The total clearance of vancomycin from plasma was significantly decreased in endotoxin-treated rats (P less than 0.01). These results demonstrate that endotoxin modifies the renal handling of vancomycin.
In vitro activities of several new macrolide antibiotics against Mycobacterium avium complex
Authors: Naik S , Ruck R
Published: June 2012

The in vitro activities of 12 macrolide compounds against 28 Mycobacterium avium complex strains isolated from patients with acquired immunodeficiency syndrome were determined by the conventional proportion method and by the BACTEC method. Clarithromycin (A-56268; TE-031), a new macrolide compound, was the most active agent tested, inhibiting 90% of strains at an MIC of 4 micrograms/ml by the BACTEC method. Roxithromycin (RU 28965) and erythromycylamine inhibited 90% of strains at 16 micrograms/ml. The organisms showed high levels of resistance to most other macrolide compounds.
In vitro susceptibilities of Chlamydia pneumoniae (Chlamydia sp. strain TWAR)
Authors: Chirgwin K , Roblin P M , Hammerschlag M R
Published: June 2012

The in vitro susceptibilities of two clinical isolates of Chlamydia pneumoniae from Brooklyn, N.Y., were determined for tetracycline, erythromycin, sulfamethoxazole, ciprofloxacin, and three new macrolides--azithromycin, clarithromycin, and roxithromycin. Clarithromycin was the most active drug tested, followed by the other macrolides, tetracycline, and ciprofloxacin.
Antifungal susceptibility of 44 clinical isolates of Fusarium species determined by using a broth microdilution method
Authors: Reuben A , Anaissie E , Nelson P E , Hashem R , Legrand C , Ho D H , Bodey G P
Published: June 2012

The MICs and minimum fungicidal concentrations of amphotericin B, natamycin, miconazole, itraconazole, and flucytosine against 17 isolates of Fusarium solani, 14 isolates of Fusarium moniliforme, 10 isolates of Fusarium oxysporum, and 3 isolates of Fusarium semitectum were determined by a broth microdilution method. Amphotericin B and natamycin were the most active agents tested and failed to show any inoculum size effect. In contrast, miconazole and itraconazole showed poor inhibitory and fungicidal activities, and the inoculum size had a major effect on the results. Flucytosine had no activity against any of the isolates tested.
Sensitive biological detection method for tetracyclines using a tetA-lacZ fusion system
Authors: Chopra I , Hacker K , Misulovin Z , Rothstein D M
Published: June 2012

A sensitive microbiological detection system for tetracyclines, utilizing an Escherichia coli strain containing a cloned tetA-lacZ gene fusion, is described. Expression of beta-galactosidase by the fusion plasmid pUB3610 remained subject to regulatory control by the TetR repressor protein, with the presence of tetracyclines in the growth medium leading to a 12-fold induction of beta-galactosidase synthesis. Because synthesis of beta-galactosidase was influenced to a small extent by the carbon source and the addition of cyclic AMP to the medium, cells were grown in the presence of cyclic AMP to enhance the sensitivity of the assay. All commonly marketed tetracyclines and some derivatives at concentrations as low as 0.1 ng/ml could be detected in the growth medium. A plate assay utilizing the fusion plasmid that detects 1 ng of tetracycline has also been developed.
In vitro emergence of quinolone-resistant mutants of Escherichia coli, Enterobacter cloacae, and Serratia marcescens
Authors: Watanabe M , Kotera Y , Yosue K , Inoue M , Mitsuhashi S
Published: June 2012

Norfloxacin- and ciprofloxacin-resistant mutants of several Enterobacter cloacae and Serratia marcescens isolates occurred at frequencies of greater than or equal to 10(-7)/CFU, which were higher than those of Escherichia coli isolates, in accordance with the increasing emergence of less-susceptible or resistant strains in clinical isolates of E. cloacae and S. marcescens.
Failure of adjunctive cytomegalovirus intravenous immune globulin to improve efficacy of ganciclovir in patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis: a phase 1 study
Authors: Jacobson M A , O'Donnell J J , Rousell R , Dionian B , Mills J
Published: June 2012

Six men with acquired immunodeficiency syndrome (AIDS) and cytomegalovirus (CMV) retinitis, treated with combined ganciclovir induction therapy and hyperimmune globulin (CMV-IGIV) for 10 days followed by CMV-IGIV alone, had a median time to retinitis progression shorter (7 days) than had eight historical controls given ganciclovir maintenance therapy (54 days; P = 0.06) and similar to that in eight controls given ganciclovir for 10 days only (19 days; P = 0.97). CMV-IGIV, which also failed to inhibit CMV replication in blood and urine, did not appear to add markedly to the efficacy of ganciclovir in acquired immunodeficiency syndrome-associated CMV retinitis.
Purification and characterization of inducible beta-lactamases in Aeromonas spp
Authors: Iaconis J P , Sanders C C
Published: June 2012

beta-Lactamases from Aeromonas hydrophila and A. sobria were purified and characterized. Both species produced beta-lactamases that were inducible by either cefoxitin or imipenem. These species were resistant to ampicillin and cephalothin but not imipenem. Isoelectric focusing of sonic extracts revealed one band at pI 8.0 and a second band at pI 7.0 for A. hydrophila. Likewise, A. sobria produced two bands, one at pI 8.4 and the other at pI 7.0. Two enzymes from each species were separated by flatbed electrofocusing gel and purified to homogeneity. The molecular weight of the pI 7.0 enzyme (A1) from both species was estimated to be 42,500, whereas the pI 8.0 (A2h) and 8.4 (A2s) enzymes of A. hydrophila and A. sobria had molecular weights of 31,500 and 35,000, respectively, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The relative Vmax values for cephalothin, penicillin, and imipenem for these enzymes indicated that A1 was primarily a cephalosporinase while A2h and A2s were penicillinases highly active against carbapenems. A1 was susceptible to inhibition by cloxacillin, while the A2 enzymes were inhibited by clavulanic acid and EDTA and required zinc for activity. Thus, there appear to be two distinct inducible beta-lactamases in A. hydrophila and A. sobria that play an important role in the beta-lactam resistance of these species.
Paradoxical activity of beta-lactam antibiotics against Proteus vulgaris in experimental infection in mice
Authors: Ikeda Y , Fukuoka Y , Motomura K , Yasuda T , Nishino T
Published: June 2012

In previous papers (Y. Ikeda and T. Nishino, Antimicrob. Agents Chemother. 32:1073-1077, 1988; Y. Ikeda, T. Nishino, and T. Tanino, Antimicrob. Agents Chemother. 31:865-869, 1987), we reported that many of the 7-aminothiazolyl cephalosporins, such as cefmenoxime, showed paradoxically reduced activity against Proteus vulgaris at higher concentrations, whereas these paradoxical effects were not observed for other types of cephalosporins, such as cefbuperazone and cefoperazone. In this study, we compare the therapeutic effect of cefmenoxime with that of cefbuperazone and explore the in vivo paradoxical effect of cefmenoxime by using an experimental infection model in mice. In an intraperitoneal infection with P. vulgaris 11, the survival rate with cefmenoxime was increased to 43% at 3.13 mg/kg but was lower at higher doses. On the other hand, cefbuperazone did not show such a paradoxical therapeutic effect. In mice infected with P. vulgaris 11, cefmenoxime levels in both serum and peritoneal washings were rapidly reduced and beta-lactamase activities in the peritoneal cavity were increased at higher cefmenoxime doses. These findings suggested that high levels of cefmenoxime at the infection site induced increased production of beta-lactamase, which then rapidly inactivated the antibiotic. We conclude that the paradoxical therapeutic effect of cefmenoxime against P. vulgaris occurs by the same mechanisms as the in vitro effect and that the high beta-lactamase inducibility and low beta-lactamase stability may account for the paradoxical therapeutic effect of cefmenoxime against P. vulgaris.
Pharmacokinetics and dose proportionality of cefmetazole in healthy young and elderly volunteers
Authors: Borin M T , Peters G R , Smith T C
Published: June 2012

The pharmacokinetics and dose proportionality of cefmetazole were studied in 24 healthy volunteers (12 young and 12 elderly). Each volunteer received single 0.5-, 1-, and 2-g doses of cefmetazole administered intravenously over 5 min according to a three-way crossover design. Serial plasma and urine samples were collected over a 24-h period following dosing and assayed for cefmetazole by a high-performance liquid chromatography method. Results of the dose proportionality portion of the study indicated that cefmetazole pharmacokinetics are linear and proportional with dose in both age groups. Comparisons of pharmacokinetic parameters between the young and elderly groups indicated that the systemic clearance was significantly lower in elderly than in young volunteers (92.4 versus 112 ml/min). Additionally, creatinine clearance was significantly lower in elderly (74.1 ml/min) than in young (92.9 ml/min) subjects. No significant differences between age groups were observed for volume of distribution, urinary recovery, terminal half-life, nonrenal clearance, or renal clearance, although half-life was slightly prolonged in elderly volunteers relative to that in young volunteers (1.54 versus 1.34 h), and renal clearance was slightly lower in elderly than in young volunteers (83.7 versus 96.1 ml/min). Both systemic and renal clearance were significantly correlated with creatinine clearance. These results indicate that the observed age-related differences in the pharmacokinetics of cefmetazole are most likely due to differences in renal function between the two age groups. The small reduction in cefmetazole elimination in the elderly would not warrant dose adjustment in this population.
Pharmacokinetics and bioavailability of intravenous-to-oral enoxacin in elderly patients with complicated urinary tract infections
Authors: Marchbanks C R , Mikolich D J , Mayer K H , Zinner S H , Dudley M N
Published: June 2012

The pharmacokinetics of oral fluoroquinolone antibiotics in normal volunteers have been studied extensively; however, limited patient data exist. Enoxacin steady-state pharmacokinetics and bioavailability were determined following repeated 400-mg intravenous (i.v.) and oral dosing by using compartmental and noncompartmental methods in 10 elderly (mean age, 73.8 years) men with complicated urinary tract infections. Average peak enoxacin concentrations following i.v. and oral dosing were 8.15 and 5.45 mg/liter, respectively. Mean values for major pharmacokinetic parameters (noncompartmental) were similar following i.v. and oral administration, respectively: area under the concentration-time curve from 0 to 12 h, 47.6 and 41.0 mg.h/liter; volume of distribution or volume of distribution/bioavailability, 1.61 and 1.99 liters/kg; total body clearance or total body clearance/bioavailability, 2.58 and 3.01 ml/min per kg; and half-life, 8.2 and 9.1 h. Parameters from analysis of enoxacin plasma concentration data by using a two-compartment pharmacokinetic model also revealed marked similarities between the two administration routes. Enoxacin was highly bioavailable (mean, 86.97%) following oral administration.
Potentiation of chloroquine activity against Plasmodium falciparum by the peroxidase-hydrogen peroxide system
Authors: Malhotra K , Salmon D , Le Bras J , Vilde J L
Published: June 2012

In this study, we examined the potential interactions between antimalarial (chloroquine, quinine, and mefloquine) and oxidant reagents. The data indicate that their effects enhance those of one another in vitro. The viability of Plasmodium falciparum in culture was assessed by [3H]hypoxanthine incorporation during 24 h of incubation in the presence of lactoperoxidase, glucose-glucose oxidase, hydrogen peroxide, chloroquine, quinine, and mefloquine, either alone or in combination. At subinhibitory concentrations, a significant inhibition was produced by the following combinations: lactoperoxidase plus hydrogen peroxide, lactoperoxidase plus glucose-glucose oxidase, lactoperoxidase plus hydrogen peroxide or glucose-glucose oxidase plus chloroquine or quinine but not with mefloquine. Deletion of any component from the system markedly decreased the toxic effect on P. falciparum. This toxic effect was not inhibited by catalase. These results indicate that the peroxidase-hydrogen peroxide system and antimalarial drugs can potentiate each other to inhibit the growth of P. falciparum.
Trimethoprim resistance in Escherichia coli isolates from a geriatric unit
Authors: Heikkilä E , Sundström L , Huovinen P
Published: June 2012

The frequency of trimethoprim resistance among Escherichia coli isolates from urine samples collected at Turku City Hospital, Turku, Finland, remained at 40% during 1984 to 1988. The proportion of highly resistant (MIC, greater than or equal to 1,024 micrograms/ml) isolates increased, however, and most of these harbored the type I dihydrofolate reductase gene. Only a few isolates possessed type II or VII genes.
Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae
Authors: Venditti M , Gelfusa V , Tarasi A , Brandimarte C , Serra P
Published: June 2012

The in vitro susceptibilities of 10 isolates of Erysipelothrix rhusiopathiae to 16 antimicrobial agents were determined. Penicillin and imipenem were the most active agents, followed by piperacillin, cefotaxime, ciprofloxacin, pefloxacin, and clindamycin. Some resistance was observed with erythromycin, tetracycline, and chloramphenicol. Activity was poor or absent with vancomycin, teicoplanin, daptomycin, trimethoprim-sulfamethoxazole, gentamicin, and netilmicin.
Improvement of amphotericin B activity during experimental cryptococcosis by incorporation into specific immunoliposomes
Authors: Dromer F , Barbet J , Bolard J , Charreire J , Yeni P
Published: June 2012

Cryptococcosis is an opportunistic infection that is responsible for increased morbidity and mortality in patients with the acquired immunodeficiency syndrome. The high toxicity of the antifungal agent that is mainly used against cryptococcosis, amphotericin B (AMB), accounts for the need for new treatments, especially in patients with the acquired immunodeficiency syndrome because of the high relapse rate of cryptococcosis. Drug targeting may be one of these alternate treatments. Since we have demonstrated that an immunoglobulin G1 (IgG1) anti-Cryptococcus neoformans serotype A monoclonal antibody (E1) was protective during experimental cryptococcosis in mice, we investigated whether specific targeting of AMB with liposomes that bear E1 would improve the therapeutic index of the drug. For that purpose, in vitro and in vivo experiments were designed to compare the specificities and activities of these liposomes with those of control immunoliposomes bearing a nonrelated IgG1 monoclonal antibody (CY34). The immunoliposomes were prepared by covalently linking E1 or CY34 and small unilamellar vesicles. When immunoliposomes were incubated with yeast cells, only E1-bearing liposomes recognized C. neoformans. In vivo, mice that were treated 24 h after infection with one injection of AMB (0.12 mg/kg of body weight) intercalated into E1-bearing liposomes survived significantly longer than did those given the same dose of AMB alone or AMB intercalated into nontargeted liposomes or control immunoliposomes. None of the mice that were given control treatments did statistically better than those that were given AMB. Keeping in mind that this kind of therapy requires knowledge of the antigenic type of the infecting organism, the results suggest that specific targeting of small doses of AMB improve the efficacy of AMB and might be an alternative to the use of larger doses of AMB.
Inhibition of Pseudomonas aeruginosa elastase and Pseudomonas keratitis using a thiol-based peptide
Authors: Burns F R , Paterson C A , Gray R D , Wells J T
Published: June 2012

Pseudomonas aeruginosa elastase is a zinc metalloproteinase which is released during P. aeruginosa infections. Pseudomonas keratitis, which occurs following contact lens-induced corneal trauma, can lead to rapid, liquefactive necrosis of the cornea. This destruction has been attributed to the release of both host-derived enzymes and the bacterial products P. aeruginosa elastase, alkaline protease, exotoxin A, and lipopolysaccharide endotoxin. A synthetic metalloproteinase inhibitor, HSCH2 (DL)CH[CH2CH(CH3)2]CO-Phe-Ala-NH2, which we previously showed to be a potent inhibitor of corneal collagenase and alkali-induced corneal ulceration, was tested as a potential inhibitor of P. aeruginosa elastase. Inhibition constants (Kis) for the resolved diastereomers were determined with the chromogenic substrate furylacryloyl-glycyl-L-leucyl-L-alanine. One isomer had a Ki of 0.3 microM, while the other had a Ki of 0.4 microM. The more potent diastereomer was evaluated in vivo in experimentally induced Pseudomonas keratitis in rabbits. Following inoculation of one cornea of each rabbit, topical treatment with a 1 mM solution of the inhibitor significantly delayed the onset of corneal melting and perforation, as compared with the results for the control and gentamicin-treated groups. This protective effect suggests that the inhibitor may have a therapeutic application by delaying the progression of corneal destruction in Pseudomonas keratitis.
In vitro activity of sparfloxacin (CI-978; AT-4140) for clinical Legionella isolates, pharmacokinetics in guinea pigs, and use to treat guinea pigs with L. pneumophila pneumonia
Authors: Edelstein P H , Edelstein M A , Weidenfeld J , Dorr M B
Published: June 2012

The activities of sparfloxacin, ciprofloxacin, and erythromycin for 21 clinical Legionella isolates were determined by agar and broth dilution susceptibility testing and by growth inhibition assays in guinea pig alveolar macrophages (sparfloxacin and ciprofloxacin). All three antimicrobial agents had roughly equivalent activities when buffered charcoal yeast extract agar medium supplemented with 0.1% alpha-ketoglutarate was used as the test medium; the MICs for 90% of strains were 1.0 micrograms/ml for erythromycin and sparfloxacin and 0.5 microgram/ml for ciprofloxacin. Buffered charcoal yeast extract medium supplemented with 0.1% alpha-ketoglutarate inhibited the activities of all the antimicrobial agents tested, as judged by the susceptibility of a control Staphylococcus aureus strain. Broth macrodilution MICs for two L. pneumophila strains in buffered yeast extract supplemented with 0.1% alpha-ketoglutarate were less than or equal to 0.03 microgram/ml for sparfloxacin, 0.06 microgram/ml for ciprofloxacin, and 0.25 microgram/ml for erythromycin; only erythromycin was inhibited by this medium. Ciprofloxacin and sparfloxacin (both 0.25 microgram/ml) reduced bacterial counts of two L. pneumophila strains grown in guinea pig alveolar macrophages by 2 log10 CFU/ml, but regrowth occurred over a 3-day period. Sparfloxacin, but not ciprofloxacin (both 1 microgram/ml), caused a 3- to 4-day postantibiotic effect. Pharmacokinetic and therapy studies of sparfloxacin were performed in guinea pigs with L. pneumophila pneumonia. For the pharmacokinetic study, sparfloxacin was given (10 mg/kg of body weight) to infected guinea pigs by the intraperitoneal route; peak levels in serum and lung were 2.6 micrograms/ml and 1.6 micrograms/g, respectively, at 1 h, with a terminal-phase half-life of elimination from serum of 5 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Evaluation of the anti-influenza virus activities of 1,3,4-thiadiazol-2-ylcyanamide (LY217896) and its sodium salt
Authors: Colacino J M , DeLong D C , Nelson J R , Spitzer W A , Tang J , Victor F , Wu C Y
Published: June 2012

1,3,4-Thiadiazol-2-ylcyanamide (LY217896) and its sodium salt were shown to be effective against influenza A and B viruses in vitro and in the mouse model. In nondividing confluent MDCK cells, the 50% inhibitory concentration of LY217896 ranged from 0.37 to 1.19 micrograms/ml against various strains of influenza A virus and from 0.75 to 1.54 micrograms/ml against various strains of influenza B virus, with no apparent cytotoxicity. However, at a concentration of 0.31 microgram/ml, LY217896 inhibited the replication of dividing MDCK cells. LY217896 (9 mg/m2 of body surface area per day) administered in the diet, in the drinking water, by oral gavage, by intraperitoneal injection, or by aerosolization was well tolerated and protected CD-1 mice infected with a lethal dose of influenza A or B virus. Effective administration of the compound could be delayed for up to 96 h postinfection. Virus titer was reduced by 1 to 2 log10 units in lungs of mice given LY217896 in the drinking water. Mice treated initially with protective levels of LY217896 were resistant to a subsequent challenge of influenza virus in the absence of the compound, indicating that the animals were able to develop immunity to the initial infection. Administration of LY217896 to uninfected mice did not induce interferon-like activity or interfere with natural killer cell function. In the ferret, LY217896 was effective in preventing fever induced by influenza virus.
Novel plasmid-mediated beta-lactamase (MIR-1) conferring resistance to oxyimino- and alpha-methoxy beta-lactams in clinical isolates of Klebsiella pneumoniae
Authors: Papanicolaou G A , Medeiros A A , Jacoby G A
Published: June 2012

Klebsiella pneumoniae isolates from 11 patients at the Miriam Hospital were identified as resistant to cefoxitin and ceftibuten as well as to aztreonam, cefotaxime, and ceftazidime. Resistance could be transferred by conjugation or transformation with plasmid DNA into Escherichia coli and was due to the production of a beta-lactamase with an isoelectric point of 8.4 named MIR-1. In E. coli, MIR-1 conferred resistance to aztreonam, cefotaxime, ceftazidime, ceftibuten, ceftriaxone, and such alpha-methoxy beta-lactams as cefmetazole, cefotetan, cefoxitin, and moxalactam. In vitro, MIR-1 hydrolyzed cephalothin and cephaloridine much more rapidly than it did penicillin G, ampicillin, or carbenicillin. Cefotaxime was hydrolyzed at 10% the rate of cephaloridine. Cefoxitin inactivation could only be detected by a microbiological test. The inhibition profile of MIR-1 was similar to that of chromosomally mediated class I beta-lactamases. Potassium clavulanate had little effect on cefoxitin or cefibuten resistance and was a poor inhibitor of MIR-1 activity. Cefoxitin or imipenem did not induce MIR-1. The gene determining MIR-1 was cloned on a 1.4-kb AccI-PstI fragment. Under stringent conditions, probes for TEM-1 and SHV-1 genes and the E. coli ampC gene failed to hybridize with the MIR-1 gene. However, a provisional sequence of 150 bp of the MIR-1 gene proved to be 90% identical to the sequence of ampC from Enterobacter cloacae but only 71% identical to that of E. coli, thus explaining the lack of hybridization to the E. coli ampC probe. Plasmid profiles of the 11 K. pneumoniae clinical isolates were not identical, but each contained a plasmid from 40 to 60 kb that hybridized with the cloned MIR-1 gene. Both transfer-proficient and transfer-deficient MIR-1 plasmids belonged to the N incompatibility group. Thus, the resistance of these K. pneumoniae strains was the result of plasmid acquisition of a class I beta-lactamase, a new resistance determinant that expands the kinds of beta-lactam resistance capable of spread by plasmid dissemination among clinical isolates.