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1.  Systematic Approach to Optimizing Specifically Targeted Antimicrobial Peptides against Streptococcus mutans▿  
Previously we reported a novel strategy of “targeted killing” through the design of narrow-spectrum molecules known as specifically targeted antimicrobial peptides (STAMPs) (R. Eckert et al., Antimicrob. Agents Chemother. 50:3651-3657, 2006; R. Eckert et al., Antimicrob. Agents Chemother. 50:1480-1488, 2006). Construction of these molecules requires the identification and the subsequent utilization of two conjoined yet functionally independent peptide components: the targeting and killing regions. In this study, we sought to design and synthesize a large number of STAMPs targeting Streptococcus mutans, the primary etiologic agent of human dental caries, in order to identify candidate peptides with increased killing speed and selectivity compared with their unmodified precursor antimicrobial peptides (AMPs). We hypothesized that a combinatorial approach, utilizing a set number of AMP, targeting, and linker regions, would be an effective method for the identification of STAMPs with the desired level of activity. STAMPs composed of the Sm6 S. mutans binding peptide and the PL-135 AMP displayed selectivity at MICs after incubation for 18 to 24 h. A STAMP where PL-135 was replaced by the B-33 killing domain exhibited both selectivity and rapid killing within 1 min of exposure and displayed activity against multispecies biofilms grown in the presence of saliva. These results suggest that potent and selective STAMP molecules can be designed and improved via a tunable “building-block” approach.
doi:10.1128/AAC.01391-09
PMCID: PMC2863653  PMID: 20211885
2.  An RpoB Mutation Confers Dual Heteroresistance to Daptomycin and Vancomycin in Staphylococcus aureus ▿  
Antimicrobial Agents and Chemotherapy  2010;54(12):5222-5233.
We have previously reported the establishment of a Staphylococcus aureus laboratory strain, 10*3d1, having reduced susceptibility to daptomycin and heterogeneous vancomycin-intermediate S. aureus (VISA) phenotype. The strain was generated in vitro by serial daptomycin selection (Camargo, I. L., H. M. Neoh, L. Cui, and K. Hiramatsu, Antimicrob. Agents Chemother. 52:4289-4299, 2008). Here we explored the genetic mechanism of resistance in the strain by whole-genome sequencing and by producing gene-replaced strains. By genome comparison between 10*3d1 and its parent methicillin-resistant Staphylococcus aureus (MRSA) strain N315ΔIP, we identified five nonsynonymous single nucleotide polymorphisms (SNPs). One of the five mutations was found in the rpoB gene encoding the RNA polymerase β subunit. The mutation at nucleotide position 1862 substituted the 621st alanine by glutamic acid. The replacement of the intact rpoB with the mutated rpoB, designated rpoB(A621E), conferred N315ΔIP with the phenotypes of reduced susceptibility to daptomycin and hetero-VISA. The rpoB(A621E)-mediated resistance conversion was accompanied by a thickened cell wall and reduction of the cell surface negative charge. Being consistent with these phenotypic changes, microarray data showed that the expression of the dlt operon, which increases the cell surface positive charge, was enhanced in the rpoB(A621E) mutant. Other remarkable findings of microarray analysis of the rpoB(A621E) mutant included repression of metabolic pathways of purine, pyrimidine, arginine, the urea cycle, and the lac operon, enhancement of the biosynthetic pathway of vitamin B2, K1, and K2, and cell wall metabolism. Finally, mutations identified in rplV and rplC, encoding 50S ribosomal proteins L22 and L3, respectively, were found to be associated with the slow growth, but not with the phenotype of decreased susceptibility to vancomycin and daptomycin, of 10*3d1.
doi:10.1128/AAC.00437-10
PMCID: PMC2981288  PMID: 20837752
3.  A mecA-Negative Strain of Methicillin-Resistant Staphylococcus aureus with High-Level β-Lactam Resistance Contains Mutations in Three Genes▿  
Antimicrobial Agents and Chemotherapy  2010;54(11):4900-4902.
We previously generated a ceftobiprole-resistant Staphylococcus aureus strain after high inoculum serial passage of a mecA-negative variant of strain COL (R. Banerjee, M. Gretes, L. Basuino, N. Strynadka, and H. F. Chambers, Antimicrob. Agents Chemother. 52:2089-2096, 2008). Genome resequencing of this strain, CRB, revealed that it differs from its parent by five single-nucleotide polymorphisms in three genes, specifically, those encoding PBP4, a low-molecular-weight penicillin-binding protein, GdpP, a predicted signaling protein, and AcrB, a cation multidrug efflux transporter. CRB displayed resistance to a variety of β-lactams but was hypersusceptible to cefoxitin.
doi:10.1128/AAC.00594-10
PMCID: PMC2976154  PMID: 20805396
4.  Cationic Amphiphiles, a New Generation of Antimicrobials Inspired by the Natural Antimicrobial Peptide Scaffold▿  
Antimicrobial Agents and Chemotherapy  2010;54(10):4049-4058.
Naturally occurring cationic antimicrobial peptides (AMPs) and their mimics form a diverse class of antibacterial agents currently validated in preclinical and clinical settings for the treatment of infections caused by antimicrobial-resistant bacteria. Numerous studies with linear, cyclic, and diastereomeric AMPs have strongly supported the hypothesis that their physicochemical properties, rather than any specific amino acid sequence, are responsible for their microbiological activities. It is generally believed that the amphiphilic topology is essential for insertion into and disruption of the cytoplasmic membrane. In particular, the ability to rapidly kill bacteria and the relative difficulty with which bacteria develop resistance make AMPs and their mimics attractive targets for drug development. However, the therapeutic use of naturally occurring AMPs is hampered by the high manufacturing costs, poor pharmacokinetic properties, and low bacteriological efficacy in animal models. In order to overcome these problems, a variety of novel and structurally diverse cationic amphiphiles that mimic the amphiphilic topology of AMPs have recently appeared. Many of these compounds exhibit superior pharmacokinetic properties and reduced in vitro toxicity while retaining potent antibacterial activity against resistant and nonresistant bacteria. In summary, cationic amphiphiles promise to provide a new and rich source of diverse antibacterial lead structures in the years to come.
doi:10.1128/AAC.00530-10
PMCID: PMC2944624  PMID: 20696877
5.  Chromosomally Encoded blaCMY-2 Located on a Novel SXT/R391-Related Integrating Conjugative Element in a Proteus mirabilis Clinical Isolate ▿  
Integrating conjugative elements (ICEs) are mobile genetic elements that can transfer from the chromosome of a host to the chromosome of a new host through the process of excision, conjugation, and integration. Although SXT/R391-related ICEs, originally demonstrated in Vibrio cholerae O139 isolates, have become prevalent among V. cholerae isolates in Asia, the prevalence of the ICEs among Gram-negative bacteria other than Vibrio spp. remains unknown. In addition, SXT/R391-related ICEs carrying genes conferring resistance to extended-spectrum cephalosporins have never been described. Here we carried out a genetic analysis of a cefoxitin-resistant Proteus mirabilis clinical isolate, TUM4660, which revealed the presence of a novel SXT/R391-related ICE, ICEPmiJpn1. ICEPmiJpn1 had a core genetic structure showing high similarity to that of R391 and carried xis and int genes completely identical to those of R391, while an IS10-mediated composite transposon carrying blaCMY-2 was integrated into the ICE. A nucleotide sequence identical to the 3′ part of ISEcp1 was located upstream of the blaCMY-2 gene, and other genes observed around blaCMY-2 in earlier studies were also present. Furthermore, the nucleotide sequences of hot spot 2 and hot spot 4 in ICEPmiJpn1 showed high similarity to that of hot spot 2 in SXTMO10 and with a part of the nucleotide sequence found in P. mirabilis ATCC 29906, respectively. ICEPmiJpn1 was successfully transferred to Escherichia coli, Klebsiella pneumoniae, Salmonella enterica serovar Typhimurium, and Citrobacter koseri in conjugation experiments. These observations suggest that ICEs may contribute to the dissemination of antimicrobial resistance genes among clinically relevant Enterobacteriaceae, which warrants careful observation of the prevalence of ICEs, including SXT/R391-related ICEs.
doi:10.1128/AAC.00111-10
PMCID: PMC2934980  PMID: 20566768
6.  Population Pharmacokinetic-Pharmacogenetic Study of Nevirapine in HIV-Infected Cambodian Patients ▿  
Antimicrobial Agents and Chemotherapy  2010;54(10):4432-4439.
The aims of this ANRS12154 open-label, single-center, multiple-dose pharmacokinetic study were to characterize nevirapine pharmacokinetics in a Cambodian population of HIV-infected patients and to identify environmental and genetic factors of variability, focusing on the CYP2B6, CYP3A5, and ABCB1 (MDR1) genes. A total of 170 Cambodian HIV-infected patients were included. Nevirapine trough concentrations were measured after 18 and 36 months of starting antiretroviral treatment and in samples drawn during a dosing interval in a subset of 10 patients. All data were analyzed by nonlinear mixed-effects modeling. The effect of covariates was investigated using the population pharmacokinetic model. Patients carrying homozygous loss-of-function alleles CYP3A5 6986A>G, CYP2B6 516G>T, CYP2B6 1459C>T, and ABCB1 3435C>T represent 42.4%, 9.2%, 0%, and 18% of the population, respectively. The median nevirapine trough concentrations did not differ after 18 and 36 months of treatment (5,705 ng/ml [range, ≤50 to 13,871] and 5,709 ng/ml [range, ≤50 to 15,422], respectively). Interpatient and intrapatient variabilities of nevirapine apparent clearance were 28% and 17%, respectively. CYP2B6 516G>T and creatinine clearance were found to significantly affect nevirapine apparent clearance. The estimated nevirapine apparent clearances were 2.95 liters/h, 2.62 liters/h, and 1.86 liters/h for CYP2B6 516GG, CYP2B6 516GT, and CYP2B6 516TT genotypes, respectively. The impact of creatinine clearance was small. This study demonstrates that 95% of the patients had sustained nevirapine exposure well above the 3,000-ng/ml threshold. Nevirapine clearance was shown to be affected by CYP2B6 516G>T genetic polymorphism and creatinine clearance, although this explained only part of the interpatient variability, which remains low compared to that for other antiretroviral drugs.
doi:10.1128/AAC.00512-10
PMCID: PMC2944557  PMID: 20696882
7.  Population pharmacokinetic-pharmacogenetic study of nevirapine in HIV-infected Cambodian patients 
Antimicrobial Agents and Chemotherapy  2010;54(10):4432-4439.
The aims of this open-label, single-center, multiple-dose pharmacokinetic study were to characterize nevirapine pharmacokinetics in a Cambodian population of HIV-infected patients and to identify environmental and genetic factors of variability focusing on the CYP2B6, CYP3A5 and ABCB1 (MDR1) genes.
170 Cambodian HIV-infected patients were included. Nevirapine trough concentrations were measured after 18 and 36 months of starting antiretroviral treatment and in samples drawn during a dosing interval in a subset of ten patients. All data were analyzed by nonlinear mixed effect modelling. The effect of covariates was investigated using the population pharmacokinetic model.
Patients carrying homozygous loss of function alleles of CYP3A5 6986A>G, CYP2B6 516G>T, CYP2B6 1459C>T and ABCB1 3435C>T represent 42.4%, 9.2%, 0% and 18% of the population, respectively.
The median nevirapine trough concentrations did not differ after 18 and 36 months of treatment (5705 (≤50 – 13871) ng/mL and 5709 (≤50 – 15422) ng/mL respectively). Interpatient and intrapatient variabilities of nevirapine apparent clearance were 28% and 17%, respectively. CYP2B6 516G>T and creatinine clearance were found to significantly affect nevirapine apparent clearance. Estimated nevirapine apparent clearance was 2.95 L/h, 2.62 L/h and 1.86 L/h for CYP2B6 516GG, 516GT and 516TT genotype, respectively. Impact of creatinine clearance is small.
This study demonstrates that 95% of the patients had a sustained nevirapine exposure well above the 3000 ng/mL threshold. Nevirapine clearance was shown to be affected by CYP2B6 516G>T genetic polymorphism and creatinine clearance, although this explained only part of the interpatient variability which remains low compared to other antiretroviral drugs.
doi:10.1128/AAC.00512-10
PMCID: PMC2944557  PMID: 20696882
Adult; Aged; Aged, 80 and over; Anti-HIV Agents; blood; pharmacokinetics; therapeutic use; Aryl Hydrocarbon Hydroxylases; genetics; Cytochrome P-450 CYP3A; genetics; Cytochrome P-450 Enzyme System; genetics; Female; HIV Infections; blood; drug therapy; Humans; Male; Middle Aged; Nevirapine; blood; pharmacokinetics; therapeutic use; Oxidoreductases, N-Demethylating; genetics; P-Glycoprotein; genetics; Polymorphism, Genetic; genetics; Young Adult
8.  Treatment with Linezolid or Vancomycin in Combination with Rifampin Is Effective in an Animal Model of Methicillin-Resistant Staphylococcus aureus Foreign Body Osteomyelitis ▿  
Rifampin monotherapy was compared to the combination of linezolid or vancomycin with rifampin in an experimental rat model of methicillin-resistant Staphylococcus aureus (MRSA) chronic foreign body osteomyelitis. MRSA was inoculated into the proximal tibia, and a titanium wire was implanted. Four weeks after infection, rats were treated intraperitoneally for 21 days with rifampin alone (n = 16), linezolid plus rifampin (n = 14), or vancomycin plus rifampin (n = 13). Thirteen animals received no treatment. At completion of treatment, qualitative cultures of the wire and quantitative cultures of the bone (reported as median values) were performed. Quantitative cultures from the control, rifampin monotherapy, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups revealed 4.54, 0.71, 0.10, and 0.50 log10 CFU/gram of bone, respectively. The bacterial load was significantly reduced in all treatment groups compared to that in the control group. Rifampin resistance was detected in isolates from 10, 2, and 1 animal in the rifampin, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups, respectively. Cultures of the removed wire revealed bacterial growth in 1 and 2 animals in the rifampin and linezolid-plus-rifampin groups, respectively, with no growth in the vancomycin-plus-rifampin group and growth from all wires in the untreated group. In conclusion, we demonstrated that combination treatment with linezolid plus rifampin or vancomycin plus rifampin is effective in an animal model of MRSA foreign body osteomyelitis in the context of retention of the infected foreign body.
doi:10.1128/AAC.00740-10
PMCID: PMC3067063  PMID: 21189340
10.  Biochemical and Structural Characterization of the Subclass B1 Metallo-β-Lactamase VIM-4 ▿  
The metallo-β-lactamase VIM-4, mainly found in Pseudomonas aeruginosa or Acinetobacter baumannii, was produced in Escherichia coli and characterized by biochemical and X-ray techniques. A detailed kinetic study performed in the presence of Zn2+ at concentrations ranging from 0.4 to 100 μM showed that VIM-4 exhibits a kinetic profile similar to the profiles of VIM-2 and VIM-1. However, VIM-4 is more active than VIM-1 against benzylpenicillin, cephalothin, nitrocefin, and imipenem and is less active than VIM-2 against ampicillin and meropenem. The crystal structure of the dizinc form of VIM-4 was solved at 1.9 Å. The sole difference between VIM-4 and VIM-1 is found at residue 228, which is Ser in VIM-1 and Arg in VIM-4. This substitution has a major impact on the VIM-4 catalytic efficiency compared to that of VIM-1. In contrast, the differences between VIM-2 and VIM-4 seem to be due to a different position of the flapping loop and two substitutions in loop 2. Study of the thermal stability and the activity of the holo- and apo-VIM-4 enzymes revealed that Zn2+ ions have a pronounced stabilizing effect on the enzyme and are necessary for preserving the structure.
doi:10.1128/AAC.01486-09
PMCID: PMC3067066  PMID: 21149620
11.  Newly Discovered and Characterized Antivirulence Compounds Inhibit Bacterial Mono-ADP-Ribosyltransferase Toxins ▿ †  
The mono-ADP-ribosyltransferase toxins are bacterial virulence factors that contribute to many disease states in plants, animals, and humans. These toxins function as enzymes that target various host proteins and covalently attach an ADP-ribose moiety that alters target protein function. We tested compounds from a virtual screen of commercially available compounds combined with a directed poly(ADP-ribose) polymerase (PARP) inhibitor library and found several compounds that bind tightly and inhibit toxins from Pseudomonas aeruginosa and Vibrio cholerae. The most efficacious compounds completely protected human lung epithelial cells against the cytotoxicity of these bacterial virulence factors. Moreover, we determined high-resolution crystal structures of the best inhibitors in complex with cholix toxin to reveal important criteria for inhibitor binding and mechanism of action. These results provide new insight into development of antivirulence compounds for treating many bacterial diseases.
doi:10.1128/AAC.01164-10
PMCID: PMC3067067  PMID: 21135177
12.  Comparative Studies Evaluating Mouse Models Used for Efficacy Testing of Experimental Drugs against Mycobacterium tuberculosis▿  
Methodologies for preclinical animal model testing of drugs against Mycobacterium tuberculosis vary from laboratory to laboratory; however, it is unknown if these variations result in different outcomes. Thus, a series of head-to-head comparisons of drug regimens in three commonly used mouse models (intravenous, a low-dose aerosol, and a high-dose aerosol infection model) and in two strains of mice are reported here. Treatment with standard tuberculosis (TB) drugs resulted in similar efficacies in two mouse species after a low-dose aerosol infection. When comparing the three different infection models, the efficacies in mice of rifampin and pyrazinamide were similar when administered with either isoniazid or moxifloxacin. Relapse studies revealed that the standard drug regimen showed a significantly higher relapse rate than the moxifloxacin-containing regimen. In fact, 4 months of the moxifloxacin-containing combination regimen showed similar relapse rates as 6 months of the standard regimen. The intravenous model showed slower bactericidal killing kinetics with the combination regimens tested and a higher relapse of infection than either aerosol infection models. All three models showed similar outcomes for in vivo efficacy and relapse of infection for the drug combinations tested, regardless of the mouse infection model used. Efficacy data for the drug combinations used also showed similar results, regardless of the formulation used for rifampin or timing of the drugs administered in combination. In all three infection models, the dual combination of rifampin and pyrazinamide was less sterilizing than the standard three-drug regimen, and therefore the results do not support the previously reported antagonism between standard TB agents.
doi:10.1128/AAC.00595-10
PMCID: PMC3067068  PMID: 21135176
13.  Site-Specific Mutation of Staphylococcus aureus VraS Reveals a Crucial Role for the VraR-VraS Sensor in the Emergence of Glycopeptide Resistance▿  
An initial response of Staphylococcus aureus to encounter with cell wall-active antibiotics occurs by transmembrane signaling systems that orchestrate changes in gene expression to promote survival. Histidine kinase two-component sensor-response regulators such as VraRS contribute to this response. In this study, we examined VraS membrane sensor phosphotransfer signal transduction and explored the genetic consequences of disrupting signaling by engineering a site-specific vraS chromosomal mutation. We have used in vitro autophosphorylation assay with purified VraS[64-347] lacking its transmembrane anchor region and tested site-specific kinase domain histidine mutants. We identified VraS H156 as the probable site of autophosphorylation and show phosphotransfer in vitro using purified VraR. Genetic studies show that the vraS(H156A) mutation in three strain backgrounds (ISP794, Newman, and COL) fails to generate detectable first-step reduced susceptibility teicoplanin mutants and severely reduces first-step vancomycin mutants. The emergence of low-level glycopeptide resistance in strain ISP794, derived from strain 8325 (ΔrsbU), did not require a functional σB, but rsbU restoration could enhance the emergence frequency supporting a role for this alternative sigma factor in promoting glycopeptide resistance. Transcriptional analysis of vraS(H156A) strains revealed a pronounced reduction but not complete abrogation of the vraRS operon after exposure to cell wall-active antibiotics, suggesting that additional factors independent of VraS-driven phosphotransfer, or σB, exist for this promoter. Collectively, our results reveal important details of the VraRS signaling system and predict that pharmacologic blockade of the VraS sensor kinase will have profound effects on blocking emergence of cell wall-active antibiotic resistance in S. aureus.
doi:10.1128/AAC.00720-10
PMCID: PMC3067069  PMID: 21173175
14.  Porphyromonas gingivalis Cysteine Proteinase Inhibition by κ-Casein Peptides ▿  
Porphyromonas gingivalis is a major pathogen associated with chronic periodontitis, an inflammatory disease of the supporting tissues of the teeth. The Arg-specific (RgpA/B) and Lys-specific (Kgp) cysteine proteinases of P. gingivalis are major virulence factors for the bacterium. In this study κ-casein(109-137) was identified in a chymosin digest of casein as an inhibiting peptide of the P. gingivalis proteinases. The peptide was synthesized and shown to inhibit proteolytic activity associated with P. gingivalis whole cells, purified RgpA-Kgp proteinase-adhesin complexes, and purified RgpB proteinase. The peptide κ-casein(109-137) exhibited synergism with Zn(II) against both Arg- and Lys-specific proteinases. The active region for inhibition was identified as κ-casein(117-137) using synthetic peptides. Kinetic studies revealed that κ-casein(109-137) inhibits in an uncompetitive manner. A molecular model based on the uncompetitive action and its synergistic ability with Zn(II) was developed to explain the mechanism of inhibition. Preincubation of P. gingivalis with κ-casein(109-137) significantly reduced lesion development in a murine model of infection.
doi:10.1128/AAC.00466-10
PMCID: PMC3067070  PMID: 21173178
15.  Quantifying Diffusion in a Biofilm of Streptococcus mutans▿  
In biofilms, diffusion may limit the chemical activity of nutrients, toxic compounds, and medicines. This study provides direct, noninvasive insight into the factors that will most effectively limit the transport of antibiotics and biocides in biofilms. Self-diffusion coefficients have been determined for a number of fluorescent probes in biofilms of Streptococcus mutans using fluorescence correlation spectroscopy. The effects of probe size and charge and the roles of biofilm pH, ionic strength, and heterogeneity were studied systematically. The relative diffusion coefficients (D in the biofilm divided by that in water) decreased with increasing probe size (3,000-molecular-weight [3K], 10K, 40K, 70K, and 2,000K dextrans). Studies using variably charged substrates (tetramethylrhodamine, Oregon Green, rhodamine B, and rhodamine 6G) showed that the self-diffusion coefficients decreased with an increasing negative charge of the fluorescent probes. No significant effect was observed for changes to the ionic strength (10−4 to 10−1 M) or pH (4 to 9) of the biofilm. Biofilm heterogeneity was responsible for variations of ca. one order of magnitude in the diffusion coefficients.
doi:10.1128/AAC.01329-10
PMCID: PMC3067071  PMID: 21189346
16.  Oxidative Stress Induction of the MexXY Multidrug Efflux Genes and Promotion of Aminoglycoside Resistance Development in Pseudomonas aeruginosa ▿  
Exposure to reactive oxygen species (ROS) (e.g., peroxide) was shown to induce expression of the PA5471 gene, which was previously shown to be required for antimicrobial induction of the MexXY components of the MexXY-OprM multidrug efflux system and aminoglycoside resistance determinant in Pseudomonas aeruginosa. mexXY was also induced by peroxide exposure, and this too was PA5471 dependent. The prospect of ROS promoting mexXY expression and aminoglycoside resistance recalls P. aeruginosa infection of the chronically inflamed lungs of cystic fibrosis (CF) patients, where the organism is exposed to ROS and where MexXY-OprM predominates as the mechanism of aminoglycoside resistance. While ROS did not enhance aminoglycoside resistance in vitro, long-term (8-day) exposure of P. aeruginosa to peroxide (mimicking chronic in vivo ROS exposure) increased aminoglycoside resistance frequency, dependent upon PA5471 and mexXY. This enhanced resistance frequency was also seen in a mutant strain overexpressing PA5471, in the absence of peroxide, suggesting that induction of PA5471 by peroxide was key to peroxide enhancement of aminoglycoside resistance frequency. Resistant mutants selected following peroxide exposure were typically pan-aminoglycoside-resistant, with mexXY generally required for this resistance. Moreover, PA5471 was required for mexXY expression and aminoglycoside resistance in these as well as several CF isolates examined.
doi:10.1128/AAC.01495-10
PMCID: PMC3067074  PMID: 21173187
17.  Characterization of the Novel CMT Enzyme TEM-154 ▿  
TEM-154, identified in Portugal in 2004, associated the substitutions observed in the extended-spectrum β-lactamase (ESBL) TEM-12 and in the inhibitor-resistant penicillinase (IRT) TEM-33. This enzyme exhibited hydrolytic activity against ceftazidime and a low level of resistance to clavulanic acid. Surprisingly, the substitution Met69Leu enhanced the catalytic efficiency of oxyimino β-lactams conferred by the substitution Arg164Ser. Its discovery confirms the dissemination of the complex mutant group of TEM enzymes in European countries.
doi:10.1128/AAC.01359-10
PMCID: PMC3067075  PMID: 21173189
18.  Interaction Potential of Etravirine with Drug Transporters Assessed In Vitro ▿  
Etravirine is a novel nonnucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of HIV-1 infections. ABC transporters potentially mediate clinically relevant drug-drug interactions. We assessed substrate characteristics and the inhibitory and inductive potential of etravirine on ABC transporters. Etravirine did not inhibit P-gp/ABCB1 and was not transported by the tested ABC transporters but was a potent inhibitor of BCRP/ABCG2. Etravirine induced several ABC transporters, especially BCRP/ABCG2. These data demonstrate that etravirine has the potential for drug-drug interactions by modulation of expression and function of several ABC transporters.
doi:10.1128/AAC.01527-10
PMCID: PMC3067076  PMID: 21189339
19.  In Vitro Activity and In Vivo Efficacy of Anidulafungin in Murine Infections by Aspergillus flavus ▿  
Anidulafungin (AFG) showed high activity against 27 strains of Aspergillus flavus by use of broth microdilution and disk diffusion methods. This drug was effective in vivo in a murine model of disseminated infection with five isolates tested. AFG was able to prolong survival and reduce tissue burden of infected mice but not able to reduce galactomannan serum concentrations. The AFG serum levels were above the corresponding minimum effective concentrations (MEC) for all of the strains tested.
doi:10.1128/AAC.01282-10
PMCID: PMC3067077  PMID: 21149624
20.  The Tea Catechin Epigallocatechin Gallate Suppresses Cariogenic Virulence Factors of Streptococcus mutans▿  
Streptococcus mutans, the primary etiologic agent of dental caries, possesses a series of virulence factors associated with its cariogenicity. Alternatives to traditional antimicrobial treatment, agents selectively inhibiting the virulence factors without necessarily suppressing the resident oral species, are promising. The anticariogenic properties of tea have been suggested in experimental animals and humans. Tea polyphenols, especially epigallocatechin gallate (EGCg), have been shown to inhibit the growth and glucosyltransferases activity of S. mutans. However, their effects on biofilm and cariogenic virulence factors of oral streptococci other than glucosyltransferases have not been well documented. In this study, we investigated the biological effect of EGCg on the virulence factors of S. mutans associated with its acidogenicity and acidurity. The antimicrobial effects of EGCg on S. mutans biofilm grown in chemically defined medium were also examined. EGCg inhibited growth of S. mutans planktonic cells at an MIC of 31.25 μg/ml and a minimal bactericidal concentration (MBC) of 62.5 μg/ml. EGCg also inhibited S. mutans biofilm formation at 15.6 μg/ml (minimum concentration that showed at least 90% inhibition of biofilm formation) and reduced viability of the preformed biofilm at 625 μg/ml (sessile MIC80). EGCg at sub-MIC levels inhibited acidogenicity and acidurity of S. mutans cells. Analysis of the data obtained from real-time PCR showed that EGCg significantly suppressed the ldh, eno, atpD, and aguD genes of S. mutans UA159. Inhibition of the enzymatic activity of F1Fo-ATPase and lactate dehydrogenase was also noted (50% inhibitory concentration between 15.6 and 31.25 μg/ml). These findings suggest that EGCg is a natural anticariogenic agent in that it exhibits antimicrobial activity against S. mutans and suppresses the specific virulence factors associated with its cariogenicity.
doi:10.1128/AAC.01016-10
PMCID: PMC3067078  PMID: 21149622
22.  Inhibitors of Endoplasmic Reticulum α-Glucosidases Potently Suppress Hepatitis C Virus Virion Assembly and Release▿  
α-Glucosidases I and II are endoplasmic reticulum-resident enzymes that are essential for N-linked glycan processing and subsequent proper folding of glycoproteins. In this report, we first demonstrate that downregulation of the expression of α-glucosidase I, II, or both in Huh7.5 cells by small hairpin RNA technology inhibited the production of hepatitis C virus (HCV). In agreement with the essential role of α-glucosidases in HCV envelope glycoprotein processing and folding, treatment of HCV-infected cells with a panel of imino sugar derivatives, which are competitive inhibitors of α-glucosidases, did not affect intracellular HCV RNA replication and nonstructural protein expression but resulted in the inhibition of glycan processing and subsequent degradation of HCV E2 glycoprotein. As a consequence, HCV virion assembly and secretion were inhibited. In searching for imino sugars with better antiviral activity, we found that a novel imino sugar, PBDNJ0804, had a superior ability to inhibit HCV virion assembly and secretion. In summary, we demonstrated that glucosidases are important host factor-based antiviral targets for HCV infection. The low likelihood of drug-resistant virus emergence and potent antiviral efficacy of the novel glucosidase inhibitor hold promise for its development as a therapeutic agent for the treatment of chronic hepatitis C.
doi:10.1128/AAC.01319-10
PMCID: PMC3067080  PMID: 21173177
23.  In Vitro Effect of qnrA1, qnrB1, and qnrS1 Genes on Fluoroquinolone Activity against Isogenic Escherichia coli Isolates with Mutations in gyrA and parC ▿  
This article provides an analysis of the in vitro effect of qnrA1, qnrB1, and qnrS1 genes, combined with quinolone-resistant Ser83Leu substitutions in GyrA and/or Ser80Arg in ParC, on fluoroquinolone (FQ) resistance in isogenic Escherichia coli strains. The association of Ser83Leu substitution in GyrA, Ser80Arg substitution in ParC, and qnr gene expression increased the MIC of ciprofloxacin to 2 μg/ml. qnr genes present in E. coli that harbored a Ser83Leu substitution in GyrA increased mutant prevention concentration (MPC) values to 8 to 32 μg/ml. qnr gene expression in E. coli may play an important role in selecting for one-step FQ-resistant mutants.
doi:10.1128/AAC.00927-10
PMCID: PMC3067081  PMID: 21173174
24.  Posaconazole Serum Concentrations among Cardiothoracic Transplant Recipients: Factors Impacting Trough Levels and Correlation with Clinical Response to Therapy▿  
Fifty-six serum posaconazole trough levels were measured in 17 cardiothoracic transplant recipients. Initial levels were ≤0.5, 0.51 to 0.99, and ≥1 μg/ml for 47, 29, and 24% of patients, respectively. Median trough levels associated with therapeutic success were higher than those associated with failure (1.55 versus 0.34 μg/ml; P = 0.006). Patients with levels consistently >0.5 μg/ml were more likely to have successful outcome (P = 0.055). Age ≥65 years, oral administration, and absence of proton pump inhibitors were associated with higher levels of posaconazole (P = 0.006, 0.006, and 0.001, respectively).
doi:10.1128/AAC.01325-10
PMCID: PMC3067082  PMID: 21189337
25.  Comparative Efficacy and Safety of Moxifloxacin and Clindamycin in the Treatment of Odontogenic Abscesses and Inflammatory Infiltrates: a Phase II, Double-Blind, Randomized Trial▿  
Moxifloxacin penetrates well into oromaxillary tissue and covers the causative pathogens that show an increasing resistance to standard antibiotics. Clinical reports suggest that moxifloxacin may be effective for the treatment of odontogenic infections that can lead to serious complications. The objective of this prospective, randomized, double-blind, multicenter study was to compare the efficacies and safeties of moxifloxacin and clindamycin for the medical treatment of patients with gingival inflammatory infiltrates and as an adjuvant therapy for patients with odontogenic abscesses requiring surgical treatment. Patients received either 400 mg moxifloxacin per os once daily or 300 mg clindamycin per os four times daily for 5 days consecutively. The primary efficacy endpoint was the percent reduction in patients' perceived pain on a visual analogue scale at days 2 to 3 from baseline. Primary analysis included 21 moxifloxacin- and 19 clindamycin-treated patients with infiltrates and 15 moxifloxacin- and 16 clindamycin-treated patients with abscesses. The mean pain reductions were 61.0% (standard deviation [SD], 46.9%) with moxifloxacin versus 23.4% (SD, 32.1%) with clindamycin (P = 0.006) for patients with infiltrates and 55.8% (SD, 24.8%) with moxifloxacin versus 42.7% (SD, 48.5%) with clindamycin (P = 0.358) for patients with abscesses. A global efficacy assessment at days 2 to 3 and 5 to 7 showed faster clinical responses with moxifloxacin in both abscess and infiltrate patients. Rates of adverse events were lower in moxifloxacin- than in clindamycin-treated patients. In patients with inflammatory infiltrates, moxifloxacin was significantly more effective in reducing pain at days 2 to 3 of therapy than clindamycin. No significant differences between groups were found for patients with odontogenic abscesses.
doi:10.1128/AAC.01267-10
PMCID: PMC3067083  PMID: 21173173

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