Postantibiotic effect and delay of regrowth in strains carrying mutations that save proteins or RNA.
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The postantibiotic effect (PAE) values found for proteinase-defective (Lon(-)) Escherichia coli and RNase-defective E. coli exposed to antibiotics were reduced (31 to 60% and 35 to 50%, respectively) in comparison with the control (AB1157), and in the recA13 mutant these values were about 0.4 h with all drugs. Nalidixic acid, under anaerobic conditions, induced no PAE (0 to 0.1 h) in AB1157. A delay in regrowth (0.2 to 0.26 h) was noted with dnaA46(Ts), gyrA43(Ts), and gyrB41(Ts) mutants cultured for 2 h at 43 degrees C. These findings suggest that when proteins and RNA are saved, the cell rapidly resumes the original growth rate. (+info)
Ex vivo synergy of arachidonate-enriched serum with ceftazidime and amikacin on multidrug-resistant Pseudomonas aeruginosa.
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Three multidrug-resistant strains of Pseudomonas aeruginosa were incubated ex vivo with sera sampled after a 10 min intravenous infusion of 25 mg/kg of arachidonic acid (AA) in 10 rabbits in the presence of ceftazidime and amikacin. Lipid peroxidation was assessed during bacterial growth. A statistically significant decrease in bacterial cells was found by the interaction of antimicrobials and serum sampled in the middle of infusion and 15 and 30 min after infusion of AA and was accompanied by elevated levels of malonodialdehyde. This effect of AA is probably attributed to lipid peroxidation and raises the possibility of its application in experimental infections. (+info)
In vitro activity, synergism, and testing parameters of amikacin, with comparisons to other aminoglycoside antibiotics.
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The activity of the new aminoglycoside antibiotic, amikacin, was evaluated in vitro against 219 clinical bacterial isolates. One hundred eighty-nine of the 219 strains had agar dilution minimal inhibitory concentration values of 8.0 mug/ml or less for amikacin. Comparative agar dilution studies were performed for gentamicin, kanamycin, and tobramycin. Gentamicin was the most active overall, but tobramycin and amikacin also had significant activity against most bacterial groups. The effects of divalent cations on the susceptibility of Pseudomonas aeruginosa to amikacin were evaluated, and the minimal inhibitory concentration values varied sixfold over a range of divalent cation concentrations from 0.2 to 8.75 mg%. The effects of media and inoculum size on disk susceptibility testing with amikacin were also evaluated. In addition, a synergistic interaction between carbenicillin and amikacin against P. aeruginosa was demonstrated. Amikacin appears to be a promising new broad spectrum antimicrobial agent. (+info)
Aminoglycoside nephrotoxicity: modeling, simulation, and control.
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The main constraints on the administration of aminoglycosides are the risks of nephrotoxicity and ototoxicity, which can lead to acute, renal, vestibular, and auditory toxicities. In the present study we focused on nephrotoxicity. No reliable predictor of nephrotoxicity has been found to date. We have developed a deterministic model which describes the pharmacokinetic behavior of aminoglycosides (with a two-compartment model), the kinetics of aminoglycoside accumulation in the renal cortex, the effects of aminoglycosides on renal cells, the resulting effects on renal function by tubuloglomerular feedback, and the resulting effects on serum creatinine concentrations. The pharmacokinetic parameter values were estimated by use of the NPEM program. The estimated pharmacodynamic parameter values were obtained after minimization of the least-squares objective function between the measured and the calculated serum creatinine concentrations. A simulation program assessed the influences of the dosage regimens on the occurrence of nephrotoxicity. We have also demonstrated the relevancy of modeling of the circadian rhythm of the renal function. We have shown the ability of the model to fit with 49 observed serum creatinine concentrations for a group of eight patients treated for endocarditis by comparison with 49 calculated serum creatinine concentrations (r(2) = 0.988; P < 0.001). We have found that for the same daily dose, the nephrotoxicity observed with a thrice-daily administration schedule appears more rapidly, induces a greater decrease in renal function, and is more prolonged than those that occur with less frequent administration schedules (for example, once-daily administration). Moreover, for once-daily administration, we have demonstrated that the time of day of administration can influence the incidence of aminoglycoside nephrotoxicity. The lowest level of nephrotoxicity was observed when aminoglycosides were administered at 1:30 p.m. Clinical application of this model might make it possible to adjust aminoglycoside dosage regimens by taking into account both the efficacies and toxicities of the drugs. (+info)
Outpatient, sequential, parenteral-oral antibiotic therapy for lower risk febrile neutropenia in children with malignant disease: a single-center, randomized, controlled trial in Argentina.
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BACKGROUND: Recent reports and previous randomized trials conducted at the authors' institution suggested that children with lower risk febrile neutropenic (LRFN) may benefit from substitution of oral antibiotic therapy for parenteral therapy. The objective of this study was to determine the efficacy of parenteral-oral outpatient therapy in the management of children with LRFN who were receiving treatment for malignant disease. METHODS: From August 2000 to April 2002, 135 children with a median age of 7.5 years (range, 1.6-15.8 years) who had a total of 177 episodes of LRFN were included in a prospective, randomized, single-institution trial. Children with LRFN received a single dose of ceftriaxone and amikacin and completed a risk-assessment work-up. All patients were discharged immediately and, at 24 hours, were allocated randomly to two groups: Group A (89 episodes) received oral ciprofloxacin, and Group B (88 episodes) received intravenous ceftriaxone. RESULTS: Most patients (61% in Group A and 51% in Group B) were receiving treatment for leukemia (P value not significant [NS]). Twenty-eight children (31%) in Group A and 22 children (25%) in Group B displayed unexplained fever (P value NS). No significant differences in sites of initial infection were found between the two groups. The median duration of neutropenia was 4.2 days and 4.7 days for Group A and Group B, respectively (P value NS); the median duration of fever was 2.3 days and 2.6 days, respectively (P value NS); and the median duration of antibiotic treatment was 4.5 days and 4.8 days, respectively (P value NS). The overall results of the study were excellent. Only four treatment failures in Group A (5%) and 6 treatment failures in Group B (7%) were observed. These patients were readmitted to the hospital and did well with appropriate treatment. CONCLUSIONS: In children with LRFN who are receiving treatment for malignant disease, outpatient oral ciprofloxacin after 24 hours of a single dose of intravenous ceftriaxone and amikacin was as safe and efficacious as parenteral ceftriaxone. Outpatient management and early antibiotic withdrawal were safe for both groups. (+info)
Comparative vestibulotoxicity of different aminoglycosides in the Guinea pigs.
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The histopathological alterations in the vestibule due to aminoglycosides are well defined. Although there are reports comparing the vestibulotoxic effects of the many aminoglycosides, this is the first study to compare the effects of the most commonly used aminoglycosides i.e., streptomycin, gentamicin, amikacin and netilmicin administered both transtympanically and systemically. The transtympanic and systemic administration of each aminoglycoside caused similar histopathological alterations in the vestibule. The most severe degeneration in the cristae ampullaris, utriculus and sacculus was observed after streptomycine administration. The severity of the vestibular damage in terms of magnitude was in the order of streptomycine, gentamicin, amikacin, and netilmicin. (+info)
Discordant resistance to kanamycin and amikacin in drug-resistant Mycobacterium tuberculosis.
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It is generally thought that there is full cross-resistance in Mycobacterium tuberculosis between the aminoglycoside drugs kanamycin and amikacin. However, kanamycin resistance and amikacin susceptibility were seen in 43 of 79 (54%) multidrug-resistant Estonian isolates, indicating that there might be a need to test the resistance of M. tuberculosis isolates to both drugs. (+info)
Treatment of febrile neutropenic patients with cancer who require hospitalization: a prospective randomized study comparing imipenem and cefepime.
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BACKGROUND: The objective of the current study was to compare the efficacy and safety of imipenem and cefepime in the treatment of adult patients with cancer who had fever and neutropenia requiring hospitalization according to Infectious Disease Society of America criteria. METHODS: In the current prospective randomized clinical trial at a university-affiliated tertiary cancer center, adult patients with cancer who had fever (> or = 38.3 degrees C or > or = 38.0 degrees C for > 2 hours) and neutropenia (< or = 500/mm(3) or < 1000/mm(3) but declining) requiring hospitalization were randomized to receive either cefepime or imipenem. Vancomycin or amikacin was added on suspicion of gram-positive or gram-negative bacterial infection, respectively. RESULTS: Patients who received an imipenem regimen or a cefepime regimen were comparable in terms of age, gender, underlying malignancy, prior transplantation, degree and trend of neutropenia, and presence of central venous catheters (P > or = 0.3). An intent-to-treat analysis showed a 68% response rate to the imipenem regimen, compared with a 75% response rate to the cefepime regimen (P = 0.2). The rates of antibiotic-related adverse events and superinfections also were comparable (P = 0.6). There was no difference in response among patients who received imipenem or cefepime alone compared with patients who also received vancomycin or amikacin (P = 1.0). Leukemia was the only independent risk factor associated with a poor outcome (odds ratio, 4.6; 95% confidence interval, 1.9-10.7; P < 0.0001). CONCLUSIONS: Imipenem and cefepime had similar efficacy and safety profiles in the treatment of adult cancer patients with fever and neutropenia who required hospitalization. The addition of either vancomycin or amikacin may not be necessary. (+info)