bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered permeability and beta-lactam resistance in a mutant of Mycobacterium smegmatis
Authors: Mukhopadhyay S , Chakrabarti P
Published: October 2018

Beta-lactam resistance in mycobacteria results from an interplay between the following: (i) beta-lactamase production, (ii) affinity of the penicillin-binding proteins (PBPs) for the drugs, and (iii) permeation of the drugs. A laboratory mutant of Mycobacterium smegmatis was studied in order to evaluate the roles of these factors in beta-lactam resistance. Mutant M13 was between 7- and 78-fold more resistant than the wild type to cephaloridine, cefoxitin, cefazolin, cefamandole, and cephalothin. Increased beta-lactamase activity toward these antibiotics was not observed in the mutant. The PBP profiles of the wild type and M13 were comparable. However, the affinities of PBP 1 for the beta-lactams tested were lower for the mutant than for the wild type. The permeation of the drugs measured in intact cells was lower for M13 than for the parent strain. The liposome swelling technique, which could be used for cephaloridine, also supported this view. Reduced permeation was not restricted to the beta-lactams alone. Glycine uptake was also lower in M13. Taken together, the results suggest that decreased affinities of PBP 1 for beta-lactams, combined with the decreased permeability of the cell wall of the mutant, lead to the development of high-level acquired beta-lactam resistance.
Influence of intravenously administered ciprofloxacin on aerobic intestinal microflora and fecal drug levels when administered simultaneously with sucralfate
Authors: Krueger W A , Ruckdeschel G , Unertl K
Published: October 2018

Ciprofloxacin, when given intravenously (i.v.), is secreted in significant amounts via the mucosa into the intestinal lumen. Sucralfate inhibits the antimicrobial activity of ciprofloxacin. The effect of combined therapy on the intestinal flora was investigated in 16 healthy volunteers. They were randomly assigned to two groups. Group A received 2 g of sucralfate orally three times a day for 7 days and 400 mg of ciprofloxacin i.v. twice a day (b.i.d.) starting 3 days after the sucralfate administration began. Group B was given only 400 mg of ciprofloxacin i.v. b.i.d. for 4 days. A total of 9 stool samples were collected from each subject beginning the week before ciprofloxacin was administered and on days -1, 1, 2, 3, 4, 7, 9, and 10 or 11 after commencement of the infusion period. The aerobic fecal flora was determined by standard microbiological methods. Measurements of fecal ciprofloxacin levels were based on high-performance liquid chromatography. Counts of bacteria of the family Enterobacteriaceae decreased in all subjects and were below 10(2) CFU/g in eight of eight subjects (group A) and six of eight subjects (group B) on day 4, but they returned to normal in all but one subject (group A) 10 days after the last infusion. The decreases in levels of bacteria of the family Enterobacteriaceae were not significantly different in groups A and B (Kaplan-Meier test). Staphylococci and nonfermenters responded variably, enterococci and lactobacilli remained unchanged, and candida levels increased transiently in four subjects (two in each group). Maximum fecal drug levels ranged from 251 to 811 microg/g. No significant difference could be found between the two groups. The i.v. application of ciprofloxacin eliminates intestinal bacteria of the family Enterobacteriaceae in a rapid and selective manner. This effect is not affected by simultaneous oral application of sucralfate.
Pharmacokinetics of intravenously and intramuscularly administered cefepime in infants and children
Authors: Reed M D , Yamashita T S , Knupp C K , Veazey J M , Blumer J L
Published: October 2018

The pharmacokinetic characteristics of cefepime were determined after first dose (n = 35) and again under steady-state conditions (n = 31) with a group of 37 infants and children. In eight subjects, a cefepime dose given by intramuscular injection was substituted for an intravenous dose, and disposition characteristics were studied again. Study subjects ranged in age from 2.1 months to 16.4 years, and all had normal renal function. Each patient received 50 mg of cefepime/kg of body weight intravenously every 8 h, up to a total maximum individual dose of 2 g. With the exception of one study patient who received a single cefepime dose for surgical prophylaxis, the patients received cefepime for 2 to 13 days. Elimination half-life (t1/2), steady-state volume of distribution, total body clearance, and renal clearance after first dose administration averaged 1.7 h, 0.35 liter/kg, and 3.1 and 1.9 ml/min/kg, respectively. Although cefepime t1/2 and mean residence time (MRT) were slightly longer for subjects <6 months of age than for older subjects, no differences in cefepime disposition characteristics between first dose and steady-state evaluations were observed. t1/2 (1.8 versus 1.9 h) and MRT (2.3 versus 3.2 h) were slightly prolonged after intramuscular administration, reflecting the influence of absorption from the intramuscular injection site on cefepime elimination. Bioavailability after intramuscular administration averaged 82% (range, 61 to 124%). Fifty-seven percent of the first dose and 88.9% of the last dose were recovered as unchanged drug in urine over the 8- and 24-h sampling periods, respectively. These pharmacokinetic data support a single cefepime dosing strategy for patients > or =2 months of age. The integration of the cefepime pharmacokinetic data generated in our study with the MICs for important pathogens responsible for infections in infants and children supports the administration of a dose of 50 mg of cefepime/kg every 12 h for patients > or =2 months of age to treat infections caused by pathogens for which cefepime MICs are < or =8 mg/liter.
In vitro activity of Bay 12-8039, a new 8-methoxyquinolone
Authors: Fass R J
Published: October 2018

MICs of Bay 12-8039 and comparative antimicrobials were determined for 820 recent clinical isolates. Ciprofloxacin was approximately 2-fold more active than Bay 12-8039 and ofloxacin against Enterobacteriaceae and approximately 8-fold more active against Pseudomonas aeruginosa. Bay 12-8039 was approximately 2- to 16-fold more active than ciproiloxacin and ofloxacin against nonfermenters (except P. aeruginosa), staphylococci, streptococci, enterococci, and anaerobes. As determined by regression analysis, there was a high degree of correlation among quinolone MICs.
Evaluation of growth promotion and inhibition from mycobactins and nonmycobacterial siderophores (Desferrioxamine and FR160) in Mycobacterium aurum
Authors: Bosne-David S , Bricard L , Ramiandrasoa F , DeRoussent A , Kunesch G , Andremont A
Published: October 2018

Heterologous mycobactins and the synthetic FR160 [N4-nonyl,N1,N8-bis(2,3-dihydroxybenzoyl) spermidine hydrobromide (C3 0H4 6N3, O6 Br)] promoted growth in Mycobacterium aurum in low concentrations. They were otherwise highly inhibitory, as opposed to homologous mycobactin, which was strictly growth promoting. Desferrioxamine B (Desferal) had no significant effect on growth.
Characterization of anti-Toxoplasma activity of SDZ 215-918, a cyclosporin derivative lacking immunosuppressive and peptidyl-prolyl-isomerase-inhibiting activity: possible role of a P glycoprotein in Toxoplasma physiology
Authors: Silverman J A , Hayes M L , Luft B J , Joiner K A
Published: October 2018

The immunosuppressive agent cyclosporin A (CsA) also possesses broad-spectrum antimicrobial activity. Previous investigators have reported that the obligate intracellular protozoan Toxoplasma gondii is sensitive to CsA. We have measured the sensitivity of Toxoplasma to 26 CsA derivatives that maintain only a subset of the parent compound's activity. We identified one compound, SDZ 215-918, that is a particularly potent inhibitor of parasite invasion and replication, with a 50% inhibitory concentration of 0.45 microg/ml, which is 10-fold lower than that of CsA. Kinetic studies demonstrate that activity has a rapid onset (half-life, < or = 20 min) and is initially reversible, although long-term exposure (> 24 h) to 5 microg/ml is lethal; in contrast, this concentration had no effect on host cell protein synthesis or cell division. SDZ 215-918 acts directly on the parasite, as demonstrated by inhibition of macromolecular synthesis in host-free extracellular parasites. Inhibition of invasion is due to a reduction in parasite motility. SDZ 215-918 does not bind to cyclophilins, the ubiquitous cyclosporin-binding proteins, but is a potent inhibitor of the mammalian P glycoprotein, a member of the ATP binding cassette transporter superfamily and the pump responsible for multidrug resistance in cancer and parasite cell lines. SDZ 215-918 blocks the efflux of rhodamine 123 from extracellular parasites, consistent with inhibition of a P glycoprotein-like pump. We suggest that a P glycoprotein or a related transporter plays a crucial role in the biology of Toxoplasma and may be a novel target for antiparasitic compounds. Preliminary studies with animals indicate that SDZ 215-918 inhibits parasite growth in vivo; its relationship to CsA may make it suitable for clinical development.
Susceptibility of penicillin-susceptible and -resistant pneumococci to dirithromycin compared with susceptibilities to erythromycin, azithromycin, clarithromycin, roxithromycin, and clindamycin
Authors: Visalli M A , Jacobs M R , Appelbaum P C
Published: October 2018

Agar dilution with incubation in air and CO2 was used to determine the MICs of erythromycin, dirithromycin, azithromycin, clarithromycin, roxithromycin, and clindamycin for 79 penicillin-susceptible, 72 penicillin-intermediate, and 74 penicillin-resistant pneumococci (158 erythromycin-susceptible and 67 erythromycin-resistant pneumococci). MICs obtained in air were usually 1 to 3 dilutions lower than those obtained in CO2. In air, the respective MICs at which 50% (MIC50s) and 90% (MIC90s) of penicillin-susceptible, -intermediate, and -resistant strains are inhibited were as follows: erythromycin, 0.016 and 0.5, 0.03 and > 64, and 2 and > 64 microg/ml; dirithromycin, 0.03 and 0.5, 0.06 and > 64, and 8 and > 64 microg/ml; azithromycin, 0.03 and 0.5, 0.06 and > 64, and 2 and > 64 microg/ml; clarithromycin, 0.016 and 0.06, 0.03 and > 64, and 2 and > 64 microg/ml; roxithromycin, 0.06 and 2, 0.06 and > 64, and 2 and > 64 microg/ml; and clindamycin, 0.03 and 0.06, 0.06 and > 64, and 0.06 and > 64 microg/ml. The MICs of erythromycin, azithromycin, and dirithromycin were very similar; however, clarithromycin MICs were generally 1 to 2 dilutions lower and roxithromycin MICs were 1 to 2 dilutions higher than those of the other compounds tested. Strains resistant to one macrolide were resistant to all macrolides; however, not all macrolide-resistant strains were resistant to clindamycin, and 32 macrolide-resistant (MICs, > or = 28 microg/ml), clindamycin-susceptible (MICs, < or = 0.25 microg/ml) strains were encountered. Time-kill testing of six strains showed similar killing kinetics for all compounds, with 99.9% killing of all strains observed with the compounds only at or above the MIC after 24 h.
Construction and characterization of an OHIO-1 beta-lactamase bearing Met69Ile and Gly238Ser mutations
Authors: Bonomo R A , Knox J R , Rudin S D , Shlaes D M
Published: October 2018

Amino acid changes that influence activity and resistance to beta-lactams and beta-lactamase inhibitors were explored by constructing the Gly238Ser and Met69Ile-Gly238Ser mutants of the OHIO-1 beta-lactamase, a class A enzyme of the SHV family. The Km values of cefotaxime and ceftazidime for OHIO-1 and Met69Ile beta-lactamases were > or = 500 microM. The Km of cefotaxime for the Gly238Ser beta-lactamase was 26 microM, and that of ceftazidime was 105 microM. The Km of cefotaxime for the Met69Ile-Gly238Ser beta-lactamase was 292 microM, and that of ceftazidime was 392 microM. For the beta-lactamase inhibitors clavulanate and sulbactam, the apparent Ki values for the Met69Ile-Gly238Ser enzyme were 0.03 and 0.15 microM, respectively. Relative Vmax values indicate that the Met69Ile-Gly238Ser mutant of the OHIO-1 beta-lactamase possesses cephalosporinase activity similar to that of the Gly238Ser mutant but diminished penicillinase activity. In an Escherichia coli DH5alpha strain that possesses a Met69Ile beta-lactamase of the OHIO-1 family, the added Gly238Ser mutation resulted in a phenotype with qualities that confer resistance to expanded-spectrum cephalosporins and, to a lesser extent, beta-lactamase inhibitors.
A multicenter, randomized study comparing the efficacy and safety of intravenous and/or oral levofloxacin versus ceftriaxone and/or cefuroxime axetil in treatment of adults with community-acquired pneumonia
Authors: File T M , Segreti J , Dunbar L , Player R , Kohler R , Williams R R , Kojak C , Rubin A
Published: October 2018

Five hundred ninety patients were enrolled in a prospective, multicenter, randomized trial comparing the efficacy and safety of 7 to 14 days of levofloxacin treatment with that of ceftriaxone and/or cefuroxime axetil in the management of community-acquired pneumonia in adults. Patients received either intravenous and/or oral levofloxacin (500 mg once daily) or the comparative agents, parenteral ceftriaxone (1 to 2 g once to twice daily) and/or oral cefuroxime axetil (500 mg twice daily). Erythromycin or doxycycline could be added to the comparator arm at the investigator's discretion. The decision to use an intravenous or oral antimicrobial agent for initial therapy was made by the investigator. Clinical and microbiological evaluations were completed at the baseline, during treatment, 5 to 7 days posttherapy, and 3 to 4 weeks posttherapy. Four hundred fifty-six patients (226 given levofloxacin and 230 administered ceftriaxone and/or cefuroxime axetil) were evaluable for clinical efficacy. Streptococcus pneumoniae and Haemophilus influenzae were isolated in 15 and 12%, respectively, of clinically evaluable patients. One hundred fifty atypical pathogens were identified: 101 were Chlamydia pneumoniae, 41 were Mycoplasma pneumoniae, and 8 were Legionella pneumophila. Clinical success at 5 to 7 days posttherapy was superior for the levofloxacin group (96%) compared with the ceftriaxone and/or cefuroxime axetil group (90%) (95% confidence interval [CI] of -10.7 to -1.3). Among patients with typical respiratory pathogens who were evaluable for microbiological efficacy, the overall bacteriologic eradication rates were superior for levofloxacin (98%) compared with the ceftriaxone and/or cefuroxime axetil group (85%) (95% CI of -21.6 to -4.8). Levofloxacin eradicated 100% of the most frequently reported respiratory pathogens (i.e., H. influenzae and S. pneumoniae) and provided a >98% clinical success rate in patients with atypical pathogens. Both levofloxacin and ceftriaxone-cefuroxime axetil eradicated 100% of the S. pneumoniae cells detected in blood culture. Drug-related adverse events were reported in 5.8% of patients receiving levofloxacin and in 8.5% of patients administered ceftriaxone and/or cefuroxime axetil. Gastrointestinal and central and peripheral nervous system adverse events were the most common events reported in each treatment group. In conclusion, these results demonstrate that treatment with levofloxacin is superior to ceftriaxone and/or cefuroxime axetil therapy in the management of community-acquired pneumonia in adults.
Rapid assessment of antibiotic effects on Escherichia coli by bis-(1,3-dibutylbarbituric acid) trimethine oxonol and flow cytometry
Authors: Jepras R I , Paul F E , Pearson S C , Wilkinson M J
Published: October 2018

The effects of selected antibiotics on Escherichia coli were studied by flow cytometry with the fluorescent anionic membrane potential probe bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. The actions of azithromycin, cefuroxime, and ciprofloxacin at five times the MIC on E. coli were compared by the traditional CFU assay and flow cytometry. Changes in viable counts of bacteria determined with DiBAC4(3) and by flow cytometry following treatment with the antibiotics showed trends similar to those found by the CFU assays. However, viable counts determined by flow cytometry following antibiotic treatment were 1 to 2 logs higher than those determined by the corresponding CFU assays. All the results obtained by flow cytometry were provided within 10 min after sampling, whereas the conventional CFU assay results took at least 18 h. The results indicated that flow cytometry is a sensitive analytical technique that can rapidly monitor the physiological changes of individual microorganisms following antibiotic action and can provide information on the mode of action of a drug. The membrane potential probe DiBAC4(3) provides a robust flow cytometric indicator for bacterial cell viability.
Comparative antianaerobic activities of the ketolides HMR 3647 (RU 66647) and HMR 3004 (RU 64004)
Authors: Ednie L M , Jacobs M R , Appelbaum P C
Published: October 2018

HMR 3647 (RU 66647) and HMR 3004 (RU 64004), two ketolides, had MICs at which 50% of the strains are inhibited (MIC50s) of 0.06 to 0.125 microg/ml and MIC90s of 16.0 microg/ml against 352 anaerobes. MIC50s and MIC90s of erythromycin, azithromycin, clarithromycin, and roxithromycin were 0.5 to 2.0 microg/ml and 32.0 to >64.0 microg/ml, respectively. HMR 3647 and HMR 3004 were more active against non-Bacteroides fragilis-group anaerobes (other than Fusobacterium mortiferum, Fusobacterium varium, and Clostridium difficile).
Comparative susceptibilities of various animal-pathogenic mycoplasmas to fluoroquinolones
Authors: Hannan P C , Windsor G D , de Jong A , Schmeer N , Stegemann M
Published: October 2018

The in vitro activities of six antimicrobial agents were tested against 162 mycoplasma strains of eight species isolated from poultry and livestock at different geographic sites. Tiamulin was most active (MICs at which 90% of the isolates were inhibited [MIC90s], 0.025 to 0.25 microg/ml); enrofloxacin and danofloxacin had near equivalent activities (MIC90s, 0.05 to 1.0 microg/ml), but were much more active than flumequine (MIC90s, 1 to 50 microg/ml). The MIC90s of tylosin and oxytetracycline were 0.25 to > 100 microg/ml and 0.25 to 100 microg/ml, respectively.
A Novel Extended-Spectrum TEM-Type β-Lactamase (TEM-52) Associated with Decreased Susceptibility to Moxalactam in
Klebsiella pneumoniae
Authors: Poyart Claire , Mugnier Pierre , Quesne Gilles , Berche Patrick , Trieu-Cuot Patrick
Published: October 2018

Klebsiella pneumoniae
NEM865 was isolated from the culture of a stool sample from a patient previously treated with ceftazidime (CAZ). Analysis of this strain by the disk diffusion test revealed synergies between amoxicillin-clavulanate (AMX-CA) and CAZ, AMX-CA and cefotaxime (CTX), AMX-CA and aztreonam (ATM), and more surprisingly, AMX-CA and moxalactam (MOX). Clavulanic acid (CA) decreased the MICs of CAZ, CTX, and MOX, which suggested that NEM865 produced a novel extended-spectrum β-lactamase. Genetic, restriction endonuclease, and Southern blot analyses revealed that the resistance phenotype was due to the presence in NEM865 of a 13.5-kb mobilizable plasmid, designated pNEC865, harboring a Tn
3
-like element. Sequence analysis revealed that the
blaT
gene of pNEC865 differed from
bla
TEM-1
by three mutations leading to the following amino acid substitutions: Glu
104
→Lys, Met
182
→Thr, and Gly
238
→Ser (Ambler numbering). The association of these three mutations has thus far never been described, and the
blaT
gene carried by pNEC865 was therefore designated
bla
TEM-52
. The enzymatic parameters of TEM-52 and TEM-3 were found to be very similar except for those for MOX, for which the affinity of TEM-52 (

K
i

, 0.16 μM) was 10-fold higher than that of TEM-3 (

K
i

, 1.9 μM). Allelic replacement analysis revealed that the combination of Lys
104
, Thr
182
, and Ser
238
was responsible for the increase in the MICs of MOX for the TEM-52 producers.
KY-62, a Polyene Analog of Amphotericin B, for Treatment of Murine Candidiasis
Authors: Graybill John R. , Najvar Laura K. , Fothergill Annette , Hardin Thomas , Rinaldi Michael , Lambros Chris , Regen Steven L.
Published: October 2018

KY-62 is a water-soluble analog of amphotericin B. In vitro testing of five clinical isolates of
Candida albicans
showed KY-62 to have potency similar to that of amphotericin B. KY-62 was administered to mice infected intravenously with
C. albicans
. In vivo, KY-62 was effective in immunocompetent mice, with potency similar to that of amphotericin B. KY-62 was well tolerated up to 30 mg/kg of body weight per dose, an amount that would be lethal with amphotericin B. KY-62 was less effective in mice rendered neutropenic with 5-fluorouracil. The addition of flucytosine had little effect. KY-62 may have potential for clinical development.
Kenyan
Plasmodium falciparum
Field Isolates: Correlation between Pyrimethamine and Chlorcycloguanil Activity In Vitro and Point Mutations in the Dihydrofolate Reductase Domain
Authors: Nzila-Mounda A. , Mberu E. K. , Sibley C. H. , Plowe C. V. , Winstanley P. A. , Watkins W. M.
Published: October 2018

Sixty-nine Kenyan
Plasmodium falciparum
field isolates were tested in vitro against pyrimethamine (PM), chlorcycloguanil (CCG), sulfadoxine (SD), and dapsone (DDS), and their dihydrofolate reductase (DHFR) genotypes were determined. The in vitro data show that CCG is more potent than PM and that DDS is more potent than SD. DHFR genotype is correlated with PM and CCG drug response. Isolates can be classified into three distinct groups based on their 50% inhibitory concentrations (IC
50
s) for PM and CCG (
P
< 0.01) and their DHFR genotypes. The first group consists of wild-type isolates with mean PM and CCG IC
50
s of 3.71 ± 6.94 and 0.24 ± 0.21 nM, respectively. The second group includes parasites which all have mutations at codon 108 alone or also at codons 51 or 59 and represents one homogeneous group for which 25- and 6-fold increases in PM and CCG IC
50
s, respectively, are observed. Parasites with mutations at codons 108, 51, and 59 (triple mutants) form a third distinct group for which nine- and eightfold increases in IC
50
s, respectively, of PM and CCG compared to the second group are observed. Surprisingly, there is a significant decrease (
P
< 0.01) of SD and DDS susceptibility in these triple mutants. Our data show that more than 92% of Kenyan field isolates have undergone at least one point mutation associated with a decrease in PM activity. These findings are of great concern because they may indicate imminent PM-SD failure, and there is no affordable antimalarial drug to replace PM-SD (Fansidar).
In Vitro and In Vivo Inhibition of Murine Gamma Herpesvirus 68 Replication by Selected Antiviral Agents
Authors: Neyts Johan , De Clercq Erik
Published: October 2018

We have evaluated the susceptibility of the murine gamma herpesvirus 68 (MHV-68) to a variety of antiviral agents. The acyclic nucleoside phosphonate analogs cidofovir [(
S
)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine], (
S
)-1-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), and adefovir [9-(2-phosphonylmethoxyethyl)adenine] efficiently inhibited the replication of the virus in Vero cells (50% effective concentrations [EC
50
s], 0.008, 0.06, and 2.2 μg/ml, respectively). Acyclovir, ganciclovir, and brivudin [(
E
)-5-(2-bromovinyl)-2′-deoxyuridine] had equipotent activities (EC
50
s, 1.5 to 8 μg/ml), whereas foscarnet and penciclovir were less effective (EC
50
s, 23 and ≥30 μg/ml, respectively). The novel N-7-substituted nucleoside analog S2242 [7-(1,3-dihydroxy-2-propoxymethyl)purine] inhibited MHV-68 replication by 50% at 0.2 μg/ml. The susceptibilities of MHV-68 and Epstein-Barr virus (EBV) to cidofovir, HPMPA, adefovir, and acyclovir were found to be comparable. However, for penciclovir, ganciclovir, brivudin, and S2242, major differences in the sensitivity of MHV-68 and EBV were observed, suggesting that MHV-68 is not always an optimal surrogate for the study of antiviral strategies for EBV. When evaluated with a model for lethal MHV-68 infections in mice with severe combined immunodeficiency, cidofovir proved to be very efficient in protecting against virus-induced mortality (100% survival at 50 days postinfection), whereas acyclovir, brivudin, and adefovir had little or no effect.
In Vitro Activity of Sanfetrinem and Affinity for the Penicillin-Binding Proteins of
Streptococcus pneumoniae
Authors: Sifaoui Farid , Varon Emmanuelle , Kitzis Marie-Dominique , Gutmann Laurent
Published: October 2018

Against penicillin-susceptible pneumococci, the activity of sanfetrinem was similar to those of penicillin, amoxicillin, cefotaxime, imipenem, and meropenem, while against penicillin-resistant strains, sanfetrinem and the carbapenems exhibited superior activity (MICs at which 90% of strains are inhibited, ≤1 μg/ml). PBP 1a in the penicillin-susceptible strain and PBP 1a and PBP 2b in the more resistant isolates seemed to be the essential penicillin-binding proteins for imipenem and sanfetrinem.
Sequences of Homologous β-Lactamases from Clinical Isolates of
Serratia marcescens
with Different Substrate Specificities
Authors: Matsumura Naoki , Minami Shinzaburo , Mitsuhashi Susumu
Published: October 2018

Genes for two group 1 β-lactamases, SRT-1 and SST-1, were sequenced. These β-lactamases were produced by clinical isolates of
Serratia marcescens
, isolates GN16694 and GN19450, respectively. The resulting enzymes were 96% identical. SRT-1 hydrolyzed oxyimino cephalosporins, but SST-1 hardly hydrolyzed them. At residue 213 in the third motif, which is conserved among group 1 β-lactamases, SRT-1 and SST-1 had Lys and Glu, respectively. By site-directed mutagenesis, the substitution of Glu by Lys at residue 213 in SST-1 resulted in an enzyme that hydrolyzed oxyimino cephalosporins.
Microbiologic Efficacy of Azithromycin and Susceptibilities to Azithromycin of Isolates of
Chlamydia pneumoniae
from Adults and Children with Community-Acquired Pneumonia
Authors: Roblin Patricia M. , Hammerschlag Margaret R.
Published: October 2018

Chlamydia pneumoniae
was eradicated from the nasopharynges of 26 of 33 (78.8%) evaluable children and adults with community-acquired pneumonia who were treated with azithromycin. We tested 55 isolates of
C. pneumoniae
obtained from 46 of these patients against azithromycin. The MIC at which 90% of the isolates were inhibited and the minimal chlamydiacidal concentration at which 90% of strains tested were killed of azithromycin for these isolates were both 0.5 μg/ml. Seven patients remained culture positive after treatment. The MICs of azithromycin for isolates from two patients increased fourfold after therapy. However, all the patients with persistent infection improved clinically. Further studies of treatment of
C. pneumoniae
infection, utilizing culture, are needed both to assess efficacy and to monitor for the possible development of antibiotic resistance.
Comparison of Strategies Using Cefpirome and Ceftazidime for Empiric Treatment of Pneumonia in Intensive Care Patients
Authors: Wolff M.
Published: October 2018

In an international, multicenter, open-label, randomized comparative study, adult patients in intensive care units were enrolled to receive cefpirome intravenously at 2 g twice daily or ceftazidime intravenously at 2 g three times daily for the empiric treatment of pneumonia. Randomization was performed after a double stratification according to the investigator’s initial choice of monotherapy or combination therapy and then on the basis of the severity of disease. The primary endpoint was the clinical response at the end of treatment in the intent-to-treat population. Data for all patients were reviewed by a blinded observer. Of the 400 enrolled patients, 201 received cefpirome (monotherapy, 56%) and 199 received ceftazidime (monotherapy, 51%). Pneumonia was hospital acquired for 75% of the patients. Clinical failures rates were 34 versus 36% (odds ratio = 0.922; upper bound of 90% confidence interval = 1.301) in the intent-to-treat analysis for cefpirome and ceftazidime, respectively. For the cefpirome and ceftazidime groups, there were 35 versus 30% clinical failures among monotherapy-stratified patients, respectively, and 34 versus 42% clinical failures among combination therapy-stratified patients, respectively. The rates of clinical failures in the per-protocol analysis were 38 and 42%, respectively. In the population of patients evaluable for bacteriologic efficacy, eradication or presumed eradication was obtained for 71% (172 of 241) and 70% (162 of 230) of the pathogens isolated from the patients receiving cefpirome and ceftazidime, respectively. The mortality rates within 2 weeks after the end of treatment were similar (cefpirome group, 31%; ceftazidime group, 26%), as were the percentages of patients with at least one treatment-related adverse event (17 and 19%, respectively). An empiric treatment strategy with cefpirome at 2 g twice daily is equivalent in terms of efficacy and tolerance to ceftazidime at 2 g three times daily for the treatment of pneumonia in patients in intensive care units.
In Vitro and In Vivo Antibacterial Activities of S-4661, a New Carbapenem
Authors: Tsuji Masakatsu , Ishii Yoshikazu , Ohno Akira , Miyazaki Shuichi , Yamaguchi Keizo
Published: October 2018

The in vitro and in vivo antibacterial activities of S-4661, a new 1β-methylcarbapenem, were compared with those of imipenem, meropenem, biapenem, cefpirome, and ceftazidime. The activity of S-4661 against methicillin-susceptible staphylococci and streptococci was comparable to that of imipenem, with an MIC at which 90% of the strains tested were inhibited (MIC
90
) equal to 0.5 μg/ml or less. S-4661 was highly active against members of the family
Enterobacteriaceae
,
Haemophilus influenzae
, and
Moraxella catarrhalis
, with MIC
90
s ranging from 0.032 to 0.5 μg/ml. Against imipenem-resistant
Pseudomonas aeruginosa
, S-4661 was the most active among test agents (MIC
90
, 8 μg/ml). Furthermore, S-4661 displayed a high degree of activity against many ceftazidime-, ciprofloxacin-, and gentamicin-resistant isolates of
P. aeruginosa
. The in vivo efficacy of S-4661 against experimentally induced infections in mice caused by gram-positive and gram-negative bacteria, including penicillin-resistant
Streptococcus pneumoniae
and drug-resistant
P. aeruginosa
, reflected its potent in vitro activity and high levels in plasma in mice. We conclude that S-4661 is a promising new carbapenem for the treatment of infections caused by gram-positive and -negative bacteria, including penicillin-resistant
S. pneumoniae
and drug-resistant
P. aeruginosa.
Characterization of In40 of
Enterobacter aerogenes
BM2688, a Class 1 Integron with Two New Gene Cassettes,
cmlA2
and
qacF
Authors: Ploy Marie-Cécile , Courvalin Patrice , Lambert Thierry
Published: October 2018

Enterobacter aerogenes
BM2688, which is resistant to multiple antibiotics, and its aminoglycoside-susceptible derivative BM2688-1 were isolated from the same clinical sample. Strain BM2688 harbored plasmid pIP833, which carries a class 1 integron, In40, containing (in addition to
qacEΔ1
and
sul1
, which are characteristic of class 1 integrons) four gene cassettes:
aac(6′)-Ib
,
qacF
,
cmlA2
, and
oxa-9
. The
cmlA2
gene had 83.7% identity with the previously described nonenzymatic chloramphenicol resistance
cmlA1
gene. The
qacF
gene conferred resistance to quaternary ammonium compounds and displayed a high degree of similarity with
qacE
(67.8% identity) which, however, has been found as part of a cassette with a very different 59-base element. The
oxa-9
gene was not expressed due to a lack of promoter sequences. Study of the antibiotic-susceptible derivative BM2688-1 indicated that a 3,148-bp deletion between the 3′ end of the
aac(6′)-Ib
gene and the 3′ conserved segment of In40 was responsible for the loss of resistance. The occurrence of this DNA rearrangement, which did not involve homologous sequences, suggests that the In40 integrase could promote recombination at secondary sites.
Accumulation of Amphotericin B in Human Macrophages Enhances Activity againstAspergillus fumigatusConidia: Quantification of Conidial Kill at the Single-Cell Level
Authors: Jahn Bernhard , Rampp Albert , Dick Christian , Jahn Andreas , Palmer Michael , Bhakdi Sucharit
Published: October 2018

A cytofluorometric assay that allowed assessment of damage to phagocytosedAspergillus fumigatusconidia at the single-cell level was developed. After ingestion by monocyte-derived macrophages (MDMs), conidia were reisolated by treatment of the cells with streptolysin O, a pore-forming toxin with lytic properties on mammalian cells but not on fungi. The counts obtained by staining of damaged conidia with propidium iodide and quantification by cytofluorometry correlated with colony counts. By the use of this method, we demonstrate that MDMs differentiated in vitro by low-dose granulocyte-macrophage colony-stimulating factor and gamma interferon have only a limited capacity to damageAspergillusconidia in vitro. The killing rate 12 h after phagocytosis was found to be only 10 to 15%. However, intracellular loading of the phagocytes with amphotericin B (AmB) dose dependently enhanced the anticonidial activity. Preincubation of macrophages with only 1 μg of AmB per ml resulted in an uptake of 18 fg of AmB/cell, leading to killing rates of 50 to 60%. The experimental protocol provides a new tool for the rapid quantification of anticonidial activity againstA. fumigatusin vitro. Intracellular accumulation of AmB may represent an important factor underlying the efficacy of this antifungal drug in the prophylaxis and treatment ofAspergillusinfections.
Characterization of Mutations in therpoBGene That Confer Rifampin Resistance inStaphylococcus aureus
Authors: Aubry-Damon Hélène , Soussy Claude-James , Courvalin Patrice
Published: October 2018

Mutations in the rifampin resistance-determining (Rif) regions of therpoBgene ofStaphylococcus aureusmutants obtained during therapy or in vitro were analyzed by gene amplification and sequencing. Each of the resistant clinical isolates, including five nonrelated clones and two strains isolated from the same patient, and of the 10 in vitro mutants had a single base pair change that resulted in an amino acid substitution in the β subunit of RNA polymerase. Eight mutational changes at seven positions were found in cluster I of the central Rif region. Certain substitutions (His481/Tyr and Asp471/Tyr [S. aureuscoordinates]) were present in several mutants. Substitutions Gln468/Arg, His481/Tyr, and Arg484/His, which conferred high-level rifampin resistance, were identical or in the same codon as those described in other bacterial genera, whereas Asp550/Gly has not been reported previously. Substitutions at codon 477 conferred high- or low-level resistance, depending on the nature of the new amino acid. The levels of resistance of in vivo and one-step in vitro mutants carrying identical mutations were similar, suggesting that no other resistance mechanism was present in the clinical isolates. On the basis of these data and the population distribution of more than 4,000 clinicalS. aureusisolates, we propose ≤0.5 and ≥8 μg/ml as new breakpoints for the clinical categorization of this species relative to rifampin.
Pharmacodynamics of Gatifloxacin in Cerebrospinal Fluid in Experimental Cephalosporin-Resistant Pneumococcal Meningitis
Authors: Lutsar Irja , Friedland Ian R. , Wubbel Loretta , McCoig Cynthia C. , Jafri Hasan S. , Ng Winston , Ghaffar Faryal , McCracken George H.
Published: October 2018

The purpose of this study was to evaluate the cerebrospinal fluid (CSF) pharmacodynamics of a new fluoroquinolone, gatifloxacin (AM-1155), in experimental pneumococcal meningitis. The penetration of gatifloxacin into CSF, calculated as the percentage of the area under the concentration-time curve (AUC) in CSF over the AUC in blood, was 46 to 56%. Gatifloxacin showed linear pharmacokinetics in CSF, and 1 h after intravenous dosages of 7.5, 15, or 30 mg/kg of body weight, peak CSF concentrations were 0.46 ± 0.08 (mean ± standard deviation), 0.94 ± 0.16, and 1.84 ± 0.5 μg/ml, respectively. The elimination half-life of gatifloxacin in CSF was 3.8 to 5.6 h (compared with 2.7 to 3.2 h in blood). There was a significant interrelationship among the highest measured values of gatifloxacin in blood and CSF/minimal bactericidal concentration (
C
peak
/MBC), the time antibiotic concentrations exceeded the MBC (
T
> MBC), and AUC/MBC (
r
= 0.94); in single-dose experiments, each correlated significantly with the bacterial killing rate. Divided-dose regimens, resulting in greater
T
> MBC values but lower
C
peak
/MBC ratios, were more effective in terms of bacterial clearance compared with corresponding single-dose regimens. Gatifloxacin therapy was as effective as currently recommended regimens (e.g., a combination of ceftriaxone and vancomycin) against this highly cephalosporin-resistant pneumococcal strain. The bactericidal activity of gatifloxacin in CSF was closely related to the AUC/MBC ratio, but maximal activity was achieved only when drug concentrations exceeded the MBC for the entire dosing interval.
Antiparasitic Effects of the Intra-Golgi Transport Inhibitor Megalomicin
Authors: Bonay Pedro , Durán-Chica Isabel , Fresno Manuel , Alarcón Balbino , Alcina Antonio
Published: October 2018

The macrolide antibiotic megalomicin (MGM) has been shown to inhibit vesicular transport between the medial- and trans-Golgi, resulting in the undersialylation of cellular proteins (P. Bonay, S. Munro, M. Fresno, and B. Alarcón, J. Biol. Chem. 271:3719–3726, 1996). Due to the effects of MGM on the Golgi and on the replication of enveloped viruses, we decided to test whether it has any antiparasitic activity. The results showed that MGM has potent activity against the epimastigote stage of
Trypanosoma cruzi
, producing a 50% inhibitory concentration (IC
50
) of 0.2 μg/ml. Furthermore, MGM was also active against the intracellular replicative, amastigote form of
T. cruzi
, completely preventing its replication in infected murine LLC/MK2 macrophages at a dose of 5 μg/ml. Although less potent, MGM was also active against
Trypanosoma brucei
epimastigotes (IC
50
, 2 μg/ml) and
Leishmania donovani
and
Leishmania major
promastigotes (IC
50
, 3 and 8 μg/ml, respectively). MGM also blocked intracellular replication of the asexual stage of
Plasmodium falciparum
-infected erythrocytes at 1 μg/ml. Finally, MGM was active in an in vivo model, resulting in the complete protection of BALB/c mice from death caused by acute
T. brucei
infection and significantly reducing the parasitemia. These results suggest that MGM is a potential drug for the treatment of veterinary and human parasitic diseases.
In Vivo Efficacy of ABT-255 against Drug-Sensitive and -Resistant
Mycobacterium tuberculosis
Strains
Authors: Oleksijew Andy , Meulbroek Jon , Ewing Patty , Jarvis Ken , Mitten Mike , Paige Lenette , Tovcimak Ann , Nukkula Mike , Chu Daniel , Alder Jeffrey D.
Published: October 2018

Current therapy for pulmonary tuberculosis involves 6 months of treatment with isoniazid, pyrazinamide, rifampin, and ethambutol or streptomycin for reliable treatment efficacy. The long treatment period increases the probability of noncompliance, leading to the generation of multidrug-resistant isolates of
Mycobacterium tuberculosis
. A treatment option that significantly shortened the course of therapy, or a new class of antibacterial effective against drug-resistant
M. tuberculosis
would be of value. ABT-255 is a novel 2-pyridone antibacterial agent which demonstrates in vitro potency and in vivo efficacy against drug-susceptible and drug-resistant
M. tuberculosis
strains. By the Alamar blue reduction technique, the MIC of ABT-255 against susceptible strains of
M. tuberculosis
ranged from 0.016 to 0.031 μg/ml. The MIC of ABT-255 against rifampin- or ethambutol-resistant
M. tuberculosis
isolates was 0.031 μg/ml. In a murine model of pulmonary tuberculosis, 4 weeks of oral ABT-255 therapy produced a 2- to 5-log
10
reduction in viable drug-susceptible
M. tuberculosis
counts from lung tissue. Against drug-resistant strains of
M. tuberculosis
, ABT-255 produced a 2- to 3-log
10
reduction in viable bacterial counts from lung tissue. ABT-255 is a promising new antibacterial agent with activity against
M. tuberculosis
.
Compartmental Pharmacokinetics and Tissue Drug Distribution of the Pradimicin Derivative BMS 181184 in Rabbits
Authors: Groll Andreas H. , Sein Tin , Petraitis Vidas , Petraitiene Ruta , Callender Diana , Gonzalez Corina E. , Giri Neelam , Bacher John , Piscitelli Stephen , Walsh Thomas J.
Published: October 2018

The pharmacokinetics of the antifungal pradimicin derivative BMS 181184 in plasma of normal, catheterized rabbits were characterized after single and multiple daily intravenous administrations of dosages of 10, 25, 50, or 150 mg/kg of body weight, and drug levels in tissues were assessed after multiple dosing. Concentrations of BMS 181184 were determined by a validated high-performance liquid chromatography method, and plasma data were modeled into a two-compartment open model. Across the investigated dosage range, BMS 181184 demonstrated nonlinear, dose-dependent kinetics with enhanced clearance, reciprocal shortening of elimination half-life, and an apparently expanding volume of distribution with increasing dosage. After single-dose administration, the mean peak plasma BMS 181184 concentration (
C
max
) ranged from 120 μg/ml at 10 mg/kg to 648 μg/ml at 150 mg/kg; the area under the concentration-time curve from 0 to 24 h (AUC
0–24
) ranged from 726 to 2,130 μg · h/ml, the volume of distribution ranged from 0.397 to 0.799 liter/kg, and the terminal half-life ranged from 4.99 to 2.31 h, respectively (
P
< 0.005 to
P
< 0.001). No drug accumulation in plasma occurred after multiple daily dosing at 10, 25, or 50 mg/kg over 15 days, although mean elimination half-lives were slightly longer. Multiple daily dosing at 150 mg/kg was associated with enhanced total clearance and a significant decrease in AUC
0–24
below the values obtained at 50 mg/kg (
P
< 0.01) and after single-dose administration of the same dosage (
P
< 0.05). Assessment of tissue BMS 181184 concentrations after multiple dosing over 16 days revealed substantial uptake in the lungs, liver, and spleen and, most notably, dose-dependent accumulation of the drug within the kidneys. These findings are indicative of dose- and time-dependent elimination of BMS 181184 from plasma and renal accumulation of the compound after multiple dosing.
Antitrypanosomal Activity of a New Triazine Derivative, SIPI 1029, In Vitro and in Model Infections
Authors: Bacchi Cyrus J. , Vargas Marcus , Rattendi Donna , Goldberg Burt , Zhou Weicheng
Published: October 2018

A recently developed diaminotriazine derivative [
O
,
O
′-bis(1,2-dihydro-2,2-tetramethylene-4,6-diamino-
S
-triazin-1-yl)-1,6-hexanediol dihydrochloride; T-46; SIPI 1029] was examined for activity against African trypanosomes in in vitro and in vivo model systems. In vitro, SIPI 1029 was 50% inhibitory for growth of bloodstream trypomastigotes of four strains of
Trypanosoma brucei brucei
and
Trypanosoma brucei rhodesiense
at 0.15 to 2.15 nM (50% inhibitory concentrations). In in vivo mouse laboratory models of
T. b. rhodesiense
clinical isolate infections, SIPI 1029 was curative for 12 of 13 isolates at ≤10 mg/kg of body weight/day for 3 days. In eight infections, a single dose was ≥60% curative, and in six of these, a dose of ≤5 mg/kg was sufficient for ≥60% cure rates. A number of these isolates were resistant to the standard trypanocide melarsoprol (Arsobal) and/or the diamidines diminazene aceturate (Berenil) and pentamidine. SIPI 1029 was also curative in combination with
dl
-α-difluoromethylornithine (Ornidyl) in a
T. b. brucei
central nervous system model infection. Some evidence of toxicity was found in dosage regimens of 10 mg/kg/day for 2 or 3 days in which deaths were observed in 6 of 65 animals given this dosage regimen. The activity of SIPI 1029 in this study indicates that this class of compounds (diaminotriazines) should be explored as leads for new human and veterinary trypanocides.
A New Approach for Early Assessment of the Epileptogenic Potential of Quinolones
Authors: Delon Annie , Pariat Claudine , Courtois Philippe , Bouquet Serge , Couet William
Published: October 2018

The epileptogenic potential of pefloxacin and norfloxacin, two quinolone antibiotics, was investigated in vivo in three different animal species by measuring drug concentrations in cerebrospinal fluid (CSF), which is part of the biophase, at the onset of convulsions. Interestingly, the pefloxacin-to-norfloxacin concentration ratios in CSF were virtually constant across the species (7.0, 6.6, and 6.0 in mice, rats, and rabbits, respectively), suggesting that this approach could be used to predict the relative epileptogenic potential of quinolones in humans.
In Vitro Susceptibilities of
Chlamydia pneumoniae
Strains Recovered from Atherosclerotic Coronary Arteries
Authors: Gieffers Jens , Solbach Werner , Maass Matthias
Published: October 2018

Chlamydia pneumoniae
strains have been recovered from arteriosclerotic coronary arteries, but their antibiotic susceptibility profiles have not yet been examined. We report in vitro susceptibility data for five cardiovascular
C. pneumoniae
isolates. These strains did not differ significantly from respiratory strains in their patterns of susceptibility to azithromycin, erythromycin, roxithromycin, ofloxacin, doxycycline, rifampin, and penicillin G. Roxithromycin was the most active macrolide, and rifampin was the most effective drug overall.
PMX-622 (Polymyxin B-Dextran 70) Does Not Alter In Vitro Activities of 11 Antimicrobial Agents
Authors: Fuchs Peter C. , Barry Arthur L. , Brown Steven D.
Published: October 2018

Because of its capacity to neutralize the lethality of gram-negative bacterial endotoxic lipopolysaccharides, PMX-622 (polymyxin B bound to dextran 70) is being developed for possible adjunctive therapy of gram-negative sepsis. In this study, it was determined that the in vitro antimicrobial activity of PMX-622 was minimal and that it does not interfere with the in vitro antimicrobial activity of 11 antibiotics commonly used to treat gram-negative infections.
Gonococcal Resistance to β-Lactams and Tetracycline Involves Mutation in Loop 3 of the Porin Encoded at the
penB
Locus
Authors: Gill M. J. , Simjee S. , Al-Hattawi K. , Robertson B. D. , Easmon C. S. F. , Ison C. A.
Published: October 2018

penB
is a chromosomal mutation that confers resistance to β-lactams and tetracyclines and reduced susceptibility to quinolones in
Neisseria gonorrhoeae
. It is linked to the porin gene (
por
) and requires the increased expression of an efflux pump due to
mtr
. Transformation of a susceptible gonococcus (strain H1) with chromosomal DNA from strain FA140 (
penA mtr penB
; porin serovar IB1) and conjugal transfer of a β-lactamase-expressing plasmid was used to produce isogenic strains for determination of equilibrium periplasmic penicillin concentrations by the method of Zimmermann and Rosselet (W. Zimmermann and A. Rosselet, Antimicrob. Agents Chemother. 12:368–372, 1977). In transformants with the Mtr and PenB phenotypes, equilibrium concentrations of penicillin were reduced. DNA sequence analysis of
por
from isogenic
penB
and
penB
+
transformants revealed 14 sequence differences; nine of these differences resulted in amino acid changes. Three amino acid changes were found in the putative gonococcal equivalent of the pore-constricting loop 3 of
Escherichia coli
OmpF. Two of these changes (Gly-101–Ala-102→Asp-Asp) result in an increased negative charge at this position in
por
loop 3. PCR products comprising the complete
por
gene from strain FA140 were transformed into strain H1-2 (
penA mtr
; porin serovar IB-3), with the resulting transformants having the antibiotic susceptibility phenotype associated with
penB. penB
-like mutations were found in loop 3 of clinical isolates of gonococci with chromosomally mediated resistance to penicillin. We conclude that
penB
is a mutation in loop 3 of
por
that reduces porin permeability to hydrophilic antibiotics and plays an important role in the development of chromosomally mediated resistance to penicillin and tetracycline in gonococci.