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FEBS Letters Jul 2003We have clinically isolated a methicillin-resistant Staphylococcus aureus (MRSA) K-1 which exhibits enhanced arbekacin (Abk) resistance. In this study, we investigated a...
We have clinically isolated a methicillin-resistant Staphylococcus aureus (MRSA) K-1 which exhibits enhanced arbekacin (Abk) resistance. In this study, we investigated a molecular mechanism for the overproduction of a bifunctional enzyme catalyzing both 2"-O-phosphorylation and 6'-N-acetylation of aminoglycoside antibiotics that is encoded by aacA-aphD and designated [AAC(6')/APH(2")] and is expressed in MRSA K-1. The sequence analysis of the 5'-adjacent region of the aacA-aphD structural gene in MRSA K-1 showed that 12 bp are deleted from the aacA-aphD promoter region when compared with that in MRSA B-26, which exhibits lower resistance to Abk than K-1. By artificially deleting the 12 bp from the corresponding region in MRSA B-26, we confirmed that the strain increases Abk resistance to the same level as seen in MRSA K-1, which suggests that the 12 bp deletion from the 5'-adjacent region of the aacA-aphD structural gene created a strong promoter to overexpress the bifunctional enzyme.
Topics: Acetylation; Aminoglycosides; Anti-Bacterial Agents; Base Sequence; Blotting, Northern; Catalysis; DNA Primers; DNA, Bacterial; Dibekacin; Genes, Bacterial; Methicillin Resistance; Microbial Sensitivity Tests; Molecular Sequence Data; Phosphorylation; Promoter Regions, Genetic; Sequence Homology, Nucleic Acid; Staphylococcus aureus
PubMed: 12832077
DOI: 10.1016/s0014-5793(03)00644-6 -
Antimicrobial Agents and Chemotherapy May 2003The ant(4')-IIb gene of Pseudomonas aeruginosa BM4492, which encodes an aminoglycoside 4'-O-adenylyltransferase, was identified as a coding sequence of 756 bp...
The ant(4')-IIb gene of Pseudomonas aeruginosa BM4492, which encodes an aminoglycoside 4'-O-adenylyltransferase, was identified as a coding sequence of 756 bp corresponding to a protein with a calculated mass of 27,219 Da. Analysis of the deduced sequence indicated that the protein was related to aminoglycoside 4'-O-adenylyltransferases IIa and Ia found in P. aeruginosa and gram-positive bacteria, respectively. The enzyme conferred resistance to amikacin and tobramycin but not to dibekacin, gentamicin, or netilmicin. The ant(4')-IIb gene had a chromosomal location in five of six clinical isolates of P. aeruginosa tested and was plasmid borne in the remaining strain. The ant(4')-IIb gene was detected by PCR in some clinical strains of P. aeruginosa from the same hospital but not in members of other bacterial genera.
Topics: Amino Acid Sequence; Aminoglycosides; Anti-Bacterial Agents; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Molecular Sequence Data; Open Reading Frames; Pseudomonas aeruginosa
PubMed: 12709326
DOI: 10.1128/AAC.47.5.1584-1588.2003 -
Antimicrobial Agents and Chemotherapy May 2003The aacA29b gene, which confers an atypical aminoglycoside resistance pattern to Escherichia coli, was identified on a class 1 integron from a multidrug-resistant...
The aacA29b gene, which confers an atypical aminoglycoside resistance pattern to Escherichia coli, was identified on a class 1 integron from a multidrug-resistant isolate of Pseudomonas aeruginosa. On the basis of amino acid sequence homology, it was proposed that the gene encoded a 6'-N-acetyltransferase. The resistance gene was cloned into the pET23a(+) vector, and overexpression conferred high-level resistance to the usual substrates of the aminoglycoside N-acetyltransferase AAC(6')-I, except netilmicin. The level of resistance conferred by aacA29b correlated perfectly with the level of expression of the gene. The corresponding C-terminal six-His-tagged AAC(6')-29b protein was purified and found to exist as a dimer in solution. With a spectrophotometric assay, an extremely feeble AAC activity was detected with acetyl coenzyme A (acetyl-CoA) as an acetyl donor. Fluorescence titrations of the protein with aminoglycosides demonstrated the very tight binding of tobramycin, dibekacin, kanamycin A, sisomicin (K(d), =1 micro M) and a weaker affinity for amikacin (K(d), approximately 60 micro M). The binding of netilmicin and acetyl-CoA could not be detected by either fluorescence spectroscopy or isothermal titration calorimetry. The inability of AAC(6')-29b to efficiently bind acetyl-CoA is supported by an alignment analysis of its amino acid sequence compared with those of other AAC(6')-I family members. AAC(6')-29b lacks a number of residues involved in acetyl-CoA binding. These results lead to the conclusion that AAC(6')-29b is able to confer aminoglycoside resistance by sequestering the drug as a result of tight binding.
Topics: Acetyltransferases; Amino Acid Sequence; Aminoglycosides; Anti-Bacterial Agents; Drug Resistance, Bacterial; Escherichia coli; Molecular Sequence Data
PubMed: 12709325
DOI: 10.1128/AAC.47.5.1577-1583.2003 -
Antimicrobial Agents and Chemotherapy Mar 2002As seen by the disk diffusion method, the clinical strain of Pseudomonas aeruginosa Pa695, resistant to all extended-spectrum cephalosporins and aminoglycosides,...
As seen by the disk diffusion method, the clinical strain of Pseudomonas aeruginosa Pa695, resistant to all extended-spectrum cephalosporins and aminoglycosides, exhibited an unusual synergistic effect between ceftazidime and imipenem. This isolate produced an extended-spectrum beta-lactamase (ESBL) with a pI of 5.8 that appeared to be chromosomally encoded. Cloning experiments revealed that this ESBL was encoded by bla(GES-1), previously described in an integron from Klebsiella pneumoniae. In P. aeruginosa Pa695, a higher level of resistance to ceftazidime than to ticarcillin was observed, and no synergy between the beta-lactamase inhibitors and extended-spectrum cephalosporins was detected, in contrast to the resistance pattern observed in K. pneumoniae. Further sequence analysis demonstrated that the bla(GES-1) gene cassette was located in a class 1 integron, which contained another sequence corresponding to the fused aac3-Ib and aac6'-Ib' gene cassettes. The fusion product was functional, as was the product of each gene cloned separately: AAC3-I, despite the deletion of the four last amino acids, and AAC6', which carried three amino acid changes compared with the most homologous sequence. The AAC3-I protein conferred an expected gentamicin and fortimicin resistance, and the AAC6', despite the Leu-119-->Ser substitution, yielded resistance to kanamycin, tobramycin, and dibekacin, but slightly affected netilmicin and amikacin, and had no apparent effect on gentamicin. The fusion product conveyed a large profile of resistance, combining the AAC6' activity with a higher level of gentamicin resistance without accompanying fortimicin resistance.
Topics: Acetyltransferases; Aminoglycosides; Anti-Bacterial Agents; Cloning, Molecular; Conjugation, Genetic; DNA, Recombinant; Drug Resistance; Escherichia coli; Genes, Bacterial; Microbial Sensitivity Tests; Plasmids; Pseudomonas aeruginosa; Reverse Transcriptase Polymerase Chain Reaction; beta-Lactam Resistance
PubMed: 11850242
DOI: 10.1128/AAC.46.3.638-645.2002 -
Hinyokika Kiyo. Acta Urologica Japonica Nov 2001The clinical efficacy of a single-day oral administration of levofloxacin (LVFX) for the prevention of urinary tract infections (UTI) after urogenital examinations and...
The clinical efficacy of a single-day oral administration of levofloxacin (LVFX) for the prevention of urinary tract infections (UTI) after urogenital examinations and treatments for outpatients was assessed. A single-day oral administration of LVFX, 100 mg three times a day, was compared to a single dose intra-muscular injection of 100 mg netilmicin sulfate or 100 mg dibekacin sulfate. Three of 219 cases (1.4%) and 7 of 304 cases (2.3%) contracted UTI in the single-day oral administration group and the single dose intra-muscular injection group, respectively. Adverse reactions were observed in 3 of 219 cases (1.4%) and 27 of 304 cases (8.8%) in the single-day oral administration group and the single dose intra-muscular injection group, respectively. In the single dose intra-muscular injection group, UTI and adverse reactions were more severe than in the single-day oral administration group. Therefore, a single-day oral administration of LVFX was superior to a single dose intra-muscular injection of netilmicin sulfate or dibekacin sulfate in the prevention of UTI with less probability of the adverse effects. A single-day oral administration of LVFX was concluded to be sufficient for the prevention of UTI caused by examinations and treatments for outpatients.
Topics: Administration, Oral; Adult; Aged; Aged, 80 and over; Ambulatory Care; Anti-Infective Agents, Urinary; Drug Administration Schedule; Female; Humans; Levofloxacin; Male; Middle Aged; Ofloxacin; Outpatients; Urinary Tract Infections
PubMed: 11771168
DOI: No ID Found -
The Brazilian Journal of Infectious... Jun 2001Arbekacin is an aminoglycoside used in Japan for treating infections caused by gentamicin and oxacillin-resistant S. aureus (ORSA). The objective of this study was to...
Arbekacin is an aminoglycoside used in Japan for treating infections caused by gentamicin and oxacillin-resistant S. aureus (ORSA). The objective of this study was to determine the in vitro antimicrobial activity of arbekacin against 454 clinical isolates of ORSA. The isolates were consecutively collected between January and July, 2000, from patients hospitalized in 8 Brazilian medical centers. The antimicrobial susceptibility testing was performed by disk diffusion method according to NCCLS recommendations. The vast majority of the isolates, 453 strains (99.8%), were considered susceptible to arbekacin based on the criteria proposed by the Requirements for Antibiotic Products of Japan. Only 1 isolate (0.2%) was classified as resistant. On the other hand, high rates of resistance were demonstrated for other aminoglycosides, such as gentamicin (97.6% resistance) and amikacin (97.0% resistance). Resistance rate was also high for ciprofloxacin (98.0%). All isolates were considered susceptible to vancomycin. The excellent in vitro antimicrobial activity of arbekacin demonstrated in this study indicates that this antimicrobial agent may play an important role in the treatment of severe ORSA infections, especially those that show poor clinical response with vancomycin monotherapy. Since the aminoglycosides should not be used as monotherapy to treat Gram positive infections, further studies evaluating in vitro and in vivo synergistic activity of arbekacin combinations are necessary to clarify the clinical role of this aminoglycoside.
Topics: Aminoglycosides; Anti-Bacterial Agents; Brazil; Dibekacin; Drug Resistance, Microbial; Hospitals; Humans; Microbial Sensitivity Tests; Oxacillin; Penicillin Resistance; Penicillins; Staphylococcal Infections; Staphylococcus aureus
PubMed: 11506776
DOI: 10.1590/s1413-86702001000300005 -
The Journal of Antibiotics Oct 2000Fourteen different aminoglycoside antibiotics (AGs) were challenged with aminoglycoside acetyltransferases (AACs) of actinomycete origin in order to examine their...
Fourteen different aminoglycoside antibiotics (AGs) were challenged with aminoglycoside acetyltransferases (AACs) of actinomycete origin in order to examine their 'double stage activity' that is arbitrarily defined as antibiotic activity retainable after enzymatic modification. In kanamycin (KM)-group AGs tested [KM, dibekacin (DKB), amikacin and arbekacin (ABK)], ABK retained activity after acetylations by AAC(3), AAC(2') and AAC(6'). DKB also retained a weak activity after acetylation by AAC(2'). In gentamicin (GM)-group AGs tested [GM, micronomicin, sisomicin (SISO), netilmicin (NTL) and isepamicin], GM, SISO and NTL retained activites after acetylation by AAC(2'). In neomycin (NM)-group AGs tested [ribostamycin, NM, paromomycin], NM retained activity after acetylation by AAC(6') and AAC(2'). None of astromicin (ASTM)-group AGs tested (ASTM and istamycin B) retained activity after acetylation by AAC(2') and AAC(6'). The activities of acetylated ABK derivatives by AAC(3) and AAC(2') were distinctively high, compared to the others. Streptomyces lividans TK21 containing the cloned aac genes were markedly sensitive to AGs that retained activities after acetylation, indicating the substantial effect of 'double stage activity'.
Topics: Acetylation; Acetyltransferases; Actinomycetales; Aminoglycosides; Anti-Bacterial Agents; Bacillus subtilis; Carbohydrate Sequence; Chromatography, Thin Layer; Drug Resistance, Microbial; Microbial Sensitivity Tests; Molecular Sequence Data; Streptomyces
PubMed: 11132963
DOI: 10.7164/antibiotics.53.1168 -
Antimicrobial Agents and Chemotherapy Sep 2000Enterococcus faecalis LC40 is an ampicillin-susceptible clinical isolate with high-level gentamicin resistance due to the aac(6')-Ie-aph(2")-Ia aminoglycoside resistance... (Comparative Study)
Comparative Study
Enterococcus faecalis LC40 is an ampicillin-susceptible clinical isolate with high-level gentamicin resistance due to the aac(6')-Ie-aph(2")-Ia aminoglycoside resistance gene. The combination of ampicillin plus arbekacin reduced mean bacterial vegetation counts significantly more than ampicillin alone or ampicillin plus gentamicin in a rabbit model of aortic-valve endocarditis caused by E. faecalis LC40.
Topics: Aminoglycosides; Ampicillin; Animals; Anti-Bacterial Agents; Dibekacin; Disease Models, Animal; Drug Resistance, Microbial; Drug Therapy, Combination; Endocarditis, Bacterial; Enterococcus faecalis; Gentamicins; Gram-Positive Bacterial Infections; Microbial Sensitivity Tests; Rabbits; Treatment Outcome
PubMed: 10952613
DOI: 10.1128/AAC.44.9.2545-2546.2000 -
Journal of Pharmacy & Pharmaceutical... 1998The purpose of this work was to predict plasma peak and trough levels of an aminoglycoside antibiotic in patients with severe illness in an intensive care unit by a...
PURPOSE
The purpose of this work was to predict plasma peak and trough levels of an aminoglycoside antibiotic in patients with severe illness in an intensive care unit by a novel approach. Plasma levels were predicted based on the values of 15 physiological measurements using an artificial neural network (ANN) simulator.
METHOD
A data set of 15 physiological measurements for 30 patients was used to develop the model. The ANN structure consisted of three layers: an input layer comprised of 15 processing elements, a hidden layer comprised of 10 processing elements with a sigmoid function as an activation function, and an output layer of two processing elements (peak and trough levels). The weight between neurons was trained according to the delta rule back-propagation of errors algorithm. Predicted values were obtained by "leave-one-out" experiments by both ANN and multiple linear regression analysis (MLRA).
RESULTS
The correlation coefficients between observed and predicted values obtained by ANN prediction using standardized data sets were r=0.825 and r=0.854 for peak and trough levels, respectively. The correlation coefficients obtained by MLRA were r=0. 037 and r=0.276 for peak and trough levels, respectively. These results indicate that ANN shows better performance in prediction of aminoglycoside plasma levels from patients' physiological measurements than MLRA.
CONCLUSIONS
Prediction of plasma levels of antibiotic in patients with severe illness by ANN was superior to the standard statistical method. Standardization of input data was found to be important for better prediction. ANN has some advantages over standard statistical methods, as it can recognize complex relationships in the data.
Topics: Aminoglycosides; Anti-Bacterial Agents; Critical Illness; Dibekacin; Humans; Intensive Care Units; Middle Aged; Neural Networks, Computer; Regression Analysis
PubMed: 10948396
DOI: No ID Found -
Antimicrobial Agents and Chemotherapy Jul 2000Daptomycin, a lipopeptide antibiotic, has broad activity against gram-positive organisms, similar to vancomycin; however, its mechanism of action differs, resulting in...
In vitro activities of daptomycin, arbekacin, vancomycin, and gentamicin alone and/or in combination against glycopeptide intermediate-resistant Staphylococcus aureus in an infection model.
Daptomycin, a lipopeptide antibiotic, has broad activity against gram-positive organisms, similar to vancomycin; however, its mechanism of action differs, resulting in interference with cell membrane transport and a more rapid bactericidal activity. In light of increasing need for alternative treatments against intermediate-resistant Staphylococcus aureus, there is revitalized interest in this antibiotic. We, therefore, evaluated the activity of daptomycin alone or in combination in an in vitro infection model against two glycopeptide intermediate-resistant S. aureus (GISA) isolates. Newly designed regimens of daptomycin at 4 and 6 mg/kg of body weight every 24 h (q24h) were compared to the previous regimen of 3 mg/kg q12h. Daptomycin MICs and minimal bactericidal concentrations (MBCs) (MIC/MBC) for Mu-50, HIP5836 (992), and MRSA-67 were 0.5/1.0, 0.5/1.0, and 0.125/0.5 microgram/ml, respectively. MICs and MBCs of arbekacin for the three strains were 2.0/8.0, 0. 125/0.5, and 0.125/0.25 microgram/ml, respectively. Vancomycin and gentamicin MICs and MBCs for the three strains were 8.0/8.0, 8.0/8.0, and 0.5/1.0 microgram/ml and 128/128, 0.5/1.0, and 0.25/0.5 microgram/ml, respectively. Our experience with daptomycin in an in vitro infection model has shown significant kill against the two GISA strains (Mu-50 and 992) (P < 0.03). We also noted that kill was related to a total dose effect for 992, in which simulated daptomycin in vivo dosages of 6 mg/kg q24h and 3 mg/kg q12h produced similar kill and 4 mg/kg q24h resulted in significant regrowth (P = 0.05). Combination therapy with arbekacin resulted in synergistic activity against Mu-50. Daptomycin area under the concentration-time curve/MIC and C(max)/MIC ranges for GISA isolates were 80 to 116 and 6 to 12, respectively, and ranges for MRSA-67 were 320 to 461 and 24 to 48, respectively, and appeared to have an association with kill (i.e., decreased CFU/milliliter) at 24 and 48 h. Therefore, these experiments suggest that daptomycin alone or in combination could provide an alternative for the treatment of GISA.
Topics: Aminoglycosides; Anti-Bacterial Agents; Daptomycin; Dibekacin; Drug Resistance, Microbial; Drug Therapy, Combination; Gentamicins; Humans; Microbial Sensitivity Tests; Models, Biological; Staphylococcal Infections; Staphylococcus aureus; Vancomycin
PubMed: 10858356
DOI: 10.1128/AAC.44.7.1925-1929.2000