Amikacin Concentrations Research Articles

Evaluation of Assays to Measure Aminoglycosides in Serum: Comparison of Accuracy and Precision Based on External Quality Assessment.

Aminoglycosides require highly accurate therapeutic drug monitoring owing to their narrow therapeutic windows and toxic side effects. Therapeutic drug monitoring varies in different laboratories, and this difference is mainly due to the use of different analytical techniques. This study aimed to compare the accuracy and precision of immunoassays for the measurement of gentamicin, tobramycin, and amikacin in serum. Human plasma samples were spiked with known concentrations of amikacin, gentamicin, and tobramycin and dispatched to laboratories worldwide. The percentage deviation and coefficient of variation were calculated to compare the accuracy and precision among immunoassays and among antibiotics. We analyzed 273, 534, and 207 amikacin, gentamicin, and tobramycin measurement results, obtained satisfactory rates of 83.9%, 86.3%, and 93.7%, and coefficients of variation ranging from 1.1% to 15.6%, 2.9% to 25.2%, and 1.8% to 27.0%, respectively. The percentage deviation ranged from -7.5% to 6.6%, -20.8% to 18.7%, and -33.2% to 41.5% for amikacin, gentamicin, and tobramycin, respectively. Significant differences were observed in accuracy and precision among assays for all antibiotics. This study demonstrated high variations in results obtained from antibiotic assays conducted at different laboratories worldwide.

Save Carbapenem Campaign: Assessment of Antibiotic Combinations Against Multidrug-Resistant Gram-Negative Bacilli

Background: Infections caused by multidrug-resistant gram-negative bacilli (MDR GNB) are a therapeutic challenge to clinicians. Combination antimicrobial therapy with empirically selected antibiotics is often used to treat these infections. This approach is ill advised because the antibiotics selected may not be optimal because of different killing activity. We aimed to determine the in vitro efficacy of antibiotic combinations devoid of carbapenems to explore potential synergy between antibiotics of different chemical classes. Methods: Prospective, experimental descriptive study of 85 MDR GNB isolated from clinical samples. The minimum inhibitory concentrations (MICs) of ceftazidime, amikacin, imipenem, and ciprofloxacin were determined by broth microdilution. The in-vitro effects of CAZ–AMK, CAZ–CIPRO, IMP–AMK and IMP–CIPRO combinations were studied by checker-board assay. Results: ESBL, AmpC, and MBL production was observed among 62.35%, 27.05%, and 44.70% of the MDR GNB, respectively. Moreover, 27.05% coproduced multiple β-lactamases. The MIC90 ranges were 16 to ≥1028 μg/mL for CAZ; 0.25 to ≥256 μg/mL for Amk, 0.25 to 12 μg/mL for CIPRO; and 0.125 to 512 μg/mL for IMP. CAZ–AMK and IMP–AMK combinations showed synergistic effects in >85% of MDR-GNB, with a fractional inhibitory concentration index ≤0.5. Higher rates of indifference and antagonism were observed with combinations including fluroquinolones. Conclusions: The in vitro antimicrobial activity of antibiotic combinations having third- or fourth-generation cephalosporin with aminoglycosides was comparable to that of imipenem alone or in combination therapy. Combinations devoid of carbapenems should be advocated to prolong the clinical usefulness of this antibiotic groupFunding: NoneDisclosures: None

Evaluation of amikacin use and comparison of the models implemented in two Bayesian forecasting software packages to guide dosing

Bayesian forecasting software can assist in guiding therapeutic drug monitoring (TDM)-based dose adjustments for amikacin to achieve therapeutic targets. This study aimed to evaluate amikacin prescribing and TDM practices, and to determine the suitability of the amikacin model incorporated into the DoseMeRx® software as a replacement for the previously available software (Abbottbase®). Patient demographics, pathology, amikacin dosing history, amikacin concentrations and Abbottbase® predicted TDM targets (area under the curve up to 24 hours, maximum concentration and trough concentration) were collected for adults receiving intravenous amikacin (2012-2017). Concordance with the Australian Therapeutic Guidelines was assessed. Observed and predicted amikacin concentrations were compared to determine the predictive performance (bias and precision) of DoseMeRx®. Amikacin TDM targets were predicted by DoseMeRx® and compared to those predicted by Abbottbase®. Overall, guideline compliance for 63 courses of amikacin in 47 patients was suboptimal. Doses were often lower than recommended. For therapy >48h, TDM sample collection timing was commonly discordant with recommendations, therapeutic target attainment low and 34% of dose adjustments inappropriate. DoseMeRx® under-predicted amikacin concentrations by 0.9mg/L (95% confidence interval [CI] -1.4 to -0.5) compared with observed concentrations. However, maximum concentration values (n=19) were unbiased (-1.7mg/L 95%CI -5.8 to 0.8) and precise (8.6% 95%CI 5.4-18.1). Predicted trough concentration values (n=7) were, at most, 1mg/L higher than observed. Amikacin area under the curve values estimated using Abbottbase® (181mgh/L 95%CI 161-202) and DoseMeRx® (176mgh/L 95%CI 152-199) were similar (P=.59). Amikacin dosing and TDM practice was suboptimal compared with guidelines. The model implemented by DoseMeRx® is satisfactory to guide amikacin dosing.

Time to Peak Concentration of Amikacin in the Antebrachiocarpal Joint Following Cephalic Intravenous Regional Limb Perfusion in Standing Horses

The aim of this study was to determine the time (Tmax) to the maximum concentration (Cmax) of amikacin sulphate in synovial fluid of the radiocarpal joint (RCJ) following cephalic intravenous regional limb perfusion (IVRLP) using 2 g of amikacin sulphate. Cephalic IVRLP was performed with 2 g of amikacin sulphate diluted in 0.9% NaCl to a total volume of 100 mL in six healthy adult mixed breed mares. An Esmarch's rubber tourniquet was applied for 30 minutes and the antibiotic solution was infused through a 23-gauge butterfly catheter. Synovial fluid was collected from the RCJ prior to the infusion and at 5, 10, 15, 20, 25 and 30 minutes after completion of IVRLP. The tourniquet was removed after the last arthrocentesis. Synovial fluid amikacin sulphate concentrations were determined by liquid chromatography/tandem mass spectrometry. The calculated mean Tmax occurred at 15 minutes (range: 10-20 minutes) post-perfusion. The highest synovial fluid amikacin sulphate concentration was noted at 10 minutes in 2 horses, 15 minutes in 2 horses and 20 minutes in 2 horses. The highest mean concentration was 1023 µg/mL and was noted at 20 minutes. Synovial mean concentrations were significantly different between 15 and 30 minutes. In this study no Tmax occurred after 20 minutes; thus, 30 minutes of tourniquet application time appear to be excessive. The 20 minutes duration of tourniquet application appears sufficient for the treatment of the RCJ in cephalic IVRLP using 2 g amikacin sulphate in a total volume of 100 mL.

Indirect Determination of Amikacin by Gold Nanoparticles as Redox Probe.

Amikacin is an aminoglycoside antibiotic used for many gram-negative bacterial infections like infections in the urinary tract, infections in brain, lungs and abdomen. Electrochemical determination of amikacin is a challenge in electroanalysis because it shows no voltammetric peak at the surface of bare electrodes. In this approach, a very simple and easy method for indirect voltammetric determination of amikacin presented in real samples. Gold nanoparticles were electrodeposited at the surface of glassy carbon electrode in constant potential. The effect of several parameters such as time and potential of deposition, pH and scan rates on signal were studied. The cathodic peak current of Au3+ decreased with increasing amikacin concentration. Quantitative analysis of amikacin was performed using differential pulse voltammetry by following cathodic peak current of gold ions. Two dynamic linear ranges of 1.0 × 10-8-1.0 × 10-7 M and 5.0 × 10-7-1.0 × 10-3 M were obtained and limit of detection was estimated 3.0× 10-9 M. The method was successfully determined amikacin in pharmaceutical preparation and human serum. The effect of several interference in determination of amikacin was also studied.

Combinatorial effects of antibiotics and enzymes against dual-species Staphylococcus aureus and Pseudomonas aeruginosa biofilms in the wound-like medium.

Bacterial biofilms are one of the major issues in the treatment of chronic infections such as chronic wounds, where biofilms are typically polymicrobial. The synergy between species can occur during most polymicrobial infections, where antimicrobial resistance enhances as a result. Furthermore, self-produced extracellular polymeric substance (EPS) in biofilms results in a high tolerance to antibiotics that complicates wound healing. Since most antibiotics fail to remove biofilms in chronic infections, new therapeutic modalities may be required. Disruption of EPS is one of the effective approaches for biofilm eradication. Therefore, degradation of EPS using enzymes may result in improved chronic wounds healing. In the current study, we investigated the efficacy of trypsin, β-glucosidase, and DNase I enzymes on the degradation of dual-species biofilms of Pseudomonas aeruginosa and Staphylococcus aureus in a wound-like medium. These species are the two most common bacteria associated with biofilm formation in chronic wounds. Moreover, the reduction of minimum biofilm eradication concentration (MBEC) of meropenem and amikacin was evaluated when combined with enzymes. The minimum effective concentrations of trypsin, β-glucosidase, and DNase I enzymes to degrade biofilms were 1 μg/ml, 8 U/ml, and 150 U/ml, respectively. Combination of 0.15 μg/ml trypsin and 50 U/ml DNase I had a significant effect on S. aureus-P. aeruginosa biofilms which resulted in the dispersal and dissolution of all biofilms. In the presence of the enzymatic mixture, MBECs of antibiotics showed a significant decrease (p < 0.05), at least 2.5 fold. We found that trypsin/DNase I mixture can be used as an anti-biofilm agent against dual-species biofilms of S. aureus-P. aeruginosa.

Characterization of biofilm production in different strains of Acinetobacter baumannii and the effects of chemical compounds on biofilm formation.

Acinetobacter baumannii, an important emerging pathogen of nosocomial infections, is known for its ability to form biofilms. Biofilm formation increases the survival rate of A. baumannii on dry surfaces and may contribute to its persistence in the hospital environment, which increases the probability of nosocomial infections and outbreaks. This study was undertaken to characterize the biofilm production of different strains of A. baumannii and the effects of chemical compounds, especially antibiotics, on biofilm formation. In this study, no statistically significant relationship was observed between the ability to form a biofilm and the antimicrobial susceptibility of the A. baumannii clinical isolates. Biofilm formation caused by A. baumannii ATCC 17978 after gene knockout of two-component regulatory system gene baeR, efflux pump genes emrA/emrB and outer membrane coding gene ompA revealed that all mutant strains had less biofilm formation than the wild-type strain, which was further supported by the images from scanning electron microscopy and confocal laser scanning microscopy. The addition of amikacin, colistin, LL-37 or tannic acid decreased the biofilm formation ability of A. baumannii. In contrast, the addition of lower subinhibitory concentration tigecycline increased the biofilm formation ability of A. baumannii. Minimum biofilm eradication concentrations of amikacin, imipenem, colistin, and tigecycline were increased obviously for both wild type and multidrug resistant clinical strain A. baumannii VGH2. In conclusion, the biofilm formation ability of A. baumannii varied in different strains, involved many genes and could be influenced by many chemical compounds.

In vitro elution of amikacin and Dispersin B from a polymer hydrogel.

To characterize the in vitro elution of amikacin and Dispersin B (β-N-acetylglucosaminidase) in a degradable hydrogel. In vitro, prospective study. Amikacin (group A; 40 mg/mL), Dispersin B (group D; 70 μg/mL), or combined amikacin and Dispersin B (group AD; 40 mg/mL and 70 μg/mL, respectively) were added to a hydrogel. Ten aliquots per group were incubated in phosphate-buffered saline that was exchanged at 1, 4, 8, 12, and 24 hours and then once daily for 10 days. Eluted amikacin and Dispersin B were quantitated by using an amikacin reagent kit and a Dispersin B enzyme-linked immunosorbent assay kit, respectively. Time point drug concentrations were compared between groups by using repeated-measures analysis of variance, and total drug elution was compared by using an area under the curve calculation. Amikacin alone, Dispersin B alone, and amikacin and Dispersin B combined together underwent rapid elution in the first 24 hours, followed by a gradual decrease over 10 days. The concentration of Dispersin B eluted in group D was higher at 1 day and lower from day 5 to day 10 compared with that in group AD. The concentration of amikacin eluted in group A was higher at 1, 4, and 8 hours and on day 10 and lower on day 1 compared with that in group AD. The total elution of amikacin was greater from group AD compared with that from group A (P = .02). Combining amikacin and Dispersin B had an affect on the total elution of amikacin but not Dispersin B. The combination of amikacin and Dispersin B in a degradable hydrogel could allow local treatment of complex infections without the requirement for multiple invasive procedures.

Using of the Sensititre MycoTB Plate Method for the Detection of Anti-tuberculous Drug Susceptibility of Rifampin Resistant Mycobacterium tuberculosis Complex Isolates

Members of the Mycobacterium tuberculosis complex (MTBC) are the causative agents of tuberculosis (TB). Rifampin resistance in the clinical isolates of MTBC is an important indicator for multidrug resistant-TB (MDR-TB) cases. In this study, it was aimed to evaluate whether the Sensititre MycoTB plaque method is suitable for the routine use in determining drug susceptibility of rifampin resistant MTBC strains. Xpert MTBC/ RIF positive rifampin resistant 100 MTBC isolates were included in the study. Xpert MTBC/RIF (Cepheid, USA) test were performed after the samples were processed by homogenization and decontamination and acid-fast staining. Rifampin resistant clinical samples were cultured in automated MGIT/BACTEC 960 (Becton Dickinson, USA) system and acid fast bacteria (AFB) were investigated. The anti-TB drug susceptibility tests of all culture positive AFB and cord factor identified as MTBC by using a cart test (MPB64, Capilla TB-Neo, Tauns Laboratories, Inc., Numazu, Japan) were performed with the Löwenstein-Jensen proportion method (LJPM) and Sensititre MycoTB (Trek Diagnostic Systems, Cleveland, OH, USA) methods. For the comparison of the methods used, the tests were performed simultaneously. The standard LJPM was performed according to the previously described procedures by World Health Organization and the Sensititre MycoTB plate method was performed as defined by the manufacturer. The final concentrations of isoniazide, rifampin, rifabutin, ethambutol, ofloxacin, moxifloxacin amikacin, kanamycin, cycloserine, ethionamide and p-aminosalicylic acid in Löwenstein-Jensen media for LJPM were 0.2 µg/ml, 40.0 µg/ml, 20.0 µg/ml, 2.0 µg/ml, 2.0 µg/ml, 1.0 µg/ml, 4.0 µg/ml, 30.0 µg/ml, 30.0 µg/ml, 40.0 µg/ml, 40.0 µg/ml and 1.0 µg/ ml, respectively. The results were obtained in 14 days for all of the drugs in the Sensititre MycoTB plate method and in 28-42 days in the LJPM. In this study, the sensitivity and specificity percentages of the Sensititre MycoTB method and the categorical agreement between the two methods were calculated. The sensitivity and specificity percentages of the Sensititre MycoTB plate method were between 84.4-100% and 95.6- 100%, respectively. The categorical agreements between the two methods were 92-100% for the drugs tested in the study. Ethambutol was found to have the lowest sensitivity (84.4%) and specificity (95.6%). The sensitivities of isoniazide, ofloxacin, streptomycin, kanamycin, ethionamide and p-aminosalicylic acid were 98.8%, 90.0%, 94.3%, 87.5%, 91.7% and 95.6%, respectively, while rifampicin, rifabutin, moxifloxacin, amikacin, cycloserine were calculated as 100%. The specificities of isoniazid, rifampicin, rifabutin, ofloxacin, moxifloxacin, amikacin, kanamycin, and cycloserine were found to be 100%, streptomycin, ethionamide and p-aminosalicylic specificity were 96.9%, 97.4% and 98.9% respectively. The categorical agreement was 96-100% in all tested drugs except ethambutol (92%). As a result, although the cost is high, owing to the short incubation period, easy to perform, the possibility for evaluating both first and second line anti-TB drugs simultaneously, determination of minimum inhibitory concentration values of the drugs, long shelf life, high sensitivity, specificity and the categorical agreement values, the Sensititre MycoTB method was determined as an effective method that can be used especially in laboratories where the workload and the MDR-TB cases are high.

A robust LC-MS/MS method for amikacin: application to cellular uptake and pharmacokinetic studies.

Background: Aminoglycosides are last-resort antibiotics for bacterial infections due to concerns of nephrotoxicity. A robust method is needed to correlate the magnitude of drug accumulation in the kidneys and the onset of nephrotoxicity.Materials & methods: A LC-MS/MS assay was developed, circumventing common limitations associated with conventional assays. To demonstrate its applicability, renal cellular uptake and rat pharmacokinetic studies were performed with amikacin. Results: To improve elution, the mobile phases were optimized with 60mM ammonium hydroxide (pH=11.2). An extended quantifiable range was achieved with different ionization modes. Kidney cells incubated with escalating amikacin concentrations showed increased uptake. Single-dose pharmacokinetics of amikacin were reasonably characterized. Conclusion: This assay will facilitate future studies on improving amikacin-associated nephrotoxicity.

The effect of aminoglycosides on horizontal gene transfer in Klebsiella pneumoniae

Antibiotic-resistant bacteria represent a global risk to public health. Horizontal gene transfer, a common mechanism for genetic exchange in bacteria, plays an essential role in the acquisition of resistance genes. In this work, we evaluated the effect of sub-lethal concentrations of antibiotics on plasmid transfer by conjugation and transformation in the opportunistic pathogen Klebsiella pneumoniae. Despite not being naturally competent, this bacterium could acquire extracellular DNA from various plasmids at a very low frequency, which increased upon incubating cells with the aminoglycoside antibiotics amikacin and gentamicin. Transfer by conjugation analyzed using a clinical isolate carrying plasmid pNDM-1 also increased in the presence of sub-lethal concentrations of antibiotics. An RNAseq analysis showed differential expression of several genes when cells were incubated in the presence of sub-lethal concentrations of amikacin suggesting metabolic and regulatory changes, as well as alteration of cell envelope components that could affect the uptake of foreign DNA. These results suggest that sub-lethal concentrations of some aminoglycosides, in particular amikacin, can promote the transfer of resistance-bearing genetic elements in K. pneumoniae, which is relevant for understanding the spread of resistance determinants in this human pathogen.

Amikacin nomogram for treatment of adult cystic fibrosis exacerbations based on an external evaluation of a population pharmacokinetic model.

In patients with cystic fibrosis (CF), amikacin is the alternative for the treatment of acute pulmonary exacerbations associated with pathogens resistant to tobramycin. Population pharmacokinetic (PK) models of amikacin in adult patients with CF have been previously published. However, current dosing recommendations remain disputed (Illamola et al. Clin Pharmacokinet. 2018;57(10):1217-1228). We perform here the first external evaluation of a published amikacin adult CF population PK model and propose a dosing nomogram for initial dosing. We retrospectively collected demographic, biological, and clinical data from the medical records of adult patients who had received intravenous amikacin. To assess the predictive performance of this model we applied visual comparison of predictions to observations, calculation of bias and inaccuracy, and simulation-based diagnostics. Monte Carlo simulations from the evaluated model were used to compare maximum concentration/minimum inhibitory concentration achieved with different dosing regimens. A total of 91 concentrations from 19 adult patients with CF were collected for external evaluation. The model predicted amikacin concentrations with reasonable bias (7.2% [95% confidence interval, CI: -0.7% to 15.0%]) and inaccuracy (18.2% [95% CI: 12.0%-24.4%]). Our simulations with this model suggest that administered amikacin doses must be adjusted to creatinine clearance and also adjusted to body weight (doses from 20 to 45 mg/kg/d). According to these simulations, we developed the Montreal amikacin nomogram to optimize amikacin dosing regimens in patients with CF. In conclusion, we developed the first nomogram to optimize initial amikacin dosing regimens in patients with CF based on this external evaluation of a recently published amikacin population PK model.

Regression Analysis of the Relationship between Probability of Renal Function Impairment and Serum Trough Concentration of Amikacin

Regression Analysis of the Relationship between Probability of Renal Function Impairment and Serum Trough Concentration of Amikacin

Emergence of clinical isolates of highly carbapenem-resistant Klebsiella pneumoniae co-harboring blaNDM-5 and blaOXA-181 or -232 in Nepal

ObjectivesThe aim of this study was to describe the emergence in Nepal of clinical isolates of Klebsiella pneumoniae harboring both blaNDM-5 and blaOXA-181/-232. MethodsSix clinical isolates of K. pneumoniae highly resistant to carbapenems and aminoglycosides were obtained from inpatients in Nepal. Their whole genomes were sequenced by a next generation sequencer. ResultsThe minimum inhibitory concentrations of meropenem, amikacin and ciprofloxacin were ≥128 μg/ml, >1024 μg/ml and ≥256 μg/ml, respectively. All six isolates co-harbored blaNDM-5, blaOXA-181 or -232 and rmtB. Of them, 1 also harbored rmtF. The blaNDM-5, blaOXA-232 and rmtB in all six isolates were located on plasmids. Of the six isolates tested, one isolate harbored two copies of blaOXA-181 and rmtF on the chromosome. ConclusionsThis is the first report of clinical isolates of K. pneumoniae co-harboring blaNDM-5, blaOXA-181 or -232 and rmtB in Nepal. These strains were highly carbapenem- and aminoglycoside-resistant, and belonged to ST147 or ST395. Of them, ST147 isolate harbored two copies of blaOXA-181 on the chromosome.

Enhanced Amikacin Diffusion With Ultrasound and Microbubbles in a Mechanically Ventilated Condensed Lung Rabbit Model.

The poor diffusion of intravenous antibiotics in lung tissue makes nosocomial pneumonia challenging to treat, notably in critical patients under mechanical ventilation. The combination of ultrasound and microbubbles (USMB) is an emerging method for non-invasive and targeted enhancement of uptake of various drugs in several organs. This study aims to evaluate if USMB may increase amikacin concentration in condensed lung tissues in a mechanically ventilated rabbit model. When applied 60 or 160 min after the beginning of an intravenous amikacin infusion, USMB increased amikacin concentration in the condensed lung tissue by 1.33 (p = 0.025) or 1.56-fold (p = 0.028) respectively. When applied 70 min after the beginning of an intravenous amikacin infusion, USMB increased amikacin concentration in the muscle tissue by 2.52 (p = 0.025). In conclusion, this study demonstrates that USMB is a promising method for the targeted delivery of amikacin in mechanically ventilated condensed lung, thus opening new therapeutic fields against lung infections.

Cointegration as a mechanism for the evolution of a KPC-producing multidrug resistance plasmid in Proteus mirabilis

ABSTRACT The incidence and transmission of Klebsiella pneumoniae carbapenemase (KPC) producing plasmids have been well documented. However, the evolutionary dynamics of KPC plasmids and their fitness costs are not well characterized. Here, two carbapenemase-producing plasmids from Proteus mirabilis, pT18 and pT211 (both carrying bla KPC-2), were characterized through whole genome sequencing. pT211 is a 24.2 kbp N-type plasmid that contains bla KPC-2 and a single copy of the IS6-family insertion sequence IS26. pT18 is a 59 kbp cointegrate plasmid comprised of sequences derived from three different plasmids: a close relative of pT211 (containing bla KPC-2), an FII-33 plasmid (bla TEM-1B, bla CTX-M-65, rmtB and fosA3) and a rolling-circle plasmid. The segments of pT18 derived from each of the different plasmids are separated by copies of IS26, and sequence analysis indicated that pT18 was likely generated by both conservative and replicative IS26-mediated cointegrate formation. pT18 and pT211 were transferred into Escherichia coli DH5α separately to assess the impact of plasmids on host fitness. Only DH5α harbouring pT18 grew slower than the wild type in antibiotic-free media. However, in sub-inhibitory concentrations of fosfomycin and amikacin, cells containing pT18 grew faster than the wild type, and the minimum concentrations of fosfomycin and amikacin required to observe an advantage for plasmid-carrying cells were 1/3 and 1/20 the DH5α MIC, respectively. This study highlights the importance of the role of cointegrate plasmids in the dissemination of antibiotic resistance genes between pathogenic bacterial species, and highlights the importance of sub-inhibitory concentrations of antibiotics to the persistence of such plasmids.

Amikacin-resistant Acinetobacter species mediated by the aphA6 gene associated with clinical outcome at an academic complex hospital in KwaZulu-Natal Province, South Africa.

Drug-resistant Acinetobacter species present serious therapeutic and infection control policy challenges globally. Although aminoglycosides have played a crucial role in the treatment of infections with multidrug-resistant (MDR) Acinetobacter spp., recent reports indicate that these bacteria are developing resistance to aminoglycosides around the globe. To determine the association between amikacin resistance and clinical outcomes of patients. The minimum inhibitory concentrations (MICs) of amikacin against Acinetobacter spp. and genes associated with resistance were also investigated. Clinical information from 107 patients with Acinetobacter spp. cultured from clinical specimens was recorded during ward rounds at an academic complex hospital in KwaZulu-Natal Province, South Africa, including clinical outcomes, history of antibiotics prescribed and microbiological investigations. The 107 Acinetobacter isolates were investigated for susceptibility to antimicrobial agents in use at local hospitals. Genes related to amikacin resistance (aphA6 and aacA4) were investigated by polymerase chain reaction (PCR) and sequencing. Analysis was performed on the relationship between clinical outcomes and antimicrobial resistance patterns, as well as on the amikacin MICs in resistant isolates (n=6) v. their PCR results. The majority (5/6, 83.3%) of patients with amikacin-resistant Acinetobacter infection were discharged, and 1/6 (16.7%) died. No underlying clinical factors were significantly associated with clinical outcome. Amikacin resistance was observed in 6/107 isolates (5.6%), with MICs of 32 µg/mL (n=3) and ≥64 µg/mL (n=3) for the amikacin-resistant isolates. All 6 of these isolates were also extensively drug-resistant (XDR). The aphA6 gene (797 base pair) was detected in all amikacin-resistant isolates. Most tested Acinetobacter isolates were susceptible to amikacin, underscoring the crucial role of this antibiotic in the treatment of MDR Acinetobacter spp. in our hospital. The emergence of XDR isolates is of serious concern and necessitates close monitoring and surveillance.

Synergetic Effects of Combined Treatment of Colistin With Meropenem or Amikacin on Carbapenem-Resistant Klebsiella pneumoniae in vitro.

The purpose of this study was to investigate the synergistic and bactericidal effects of combinations of colistin with meropenem or amikacin in vitro and provide laboratory data needed for development of therapeutic strategies for the treatment of carbapenem-resistant Klebsiella pneumoniae (CRKP) infection. We found that minimum inhibitory concentration (MIC) of colistin, meropenem and amikacin were 2~32, 4~256, and 1~16384 μg/ml, respectively. The minimum bactericidal concentration of the antibiotics was either 1× or 2×MIC. Treatments of 6 CRKP isolates at 1 μg/ml colistin completely killed 2 of them and suppressed 4 others growth. 4 CRKP isolates at 16 μg/ml meropenem or amikacin completely killed and suppressed 2 others growth. 2 CRKP isolates showed synergic effects in all colistin combination and 3 CRKP isolates showed synergic effects in part of colistin combination. Our data suggest that colistin in combination with either meropenem or amikacin could be a valid therapeutic option against colistin-resistant CRKP isolates. Moreover, the combination of colistin-amikacin is less expensive to treat CRKP infections in Eastern Heilongjiang Province.

Antibiotics and antifungals in silicone oil

BackgroundAntimicrobials may be injected into silicone oil-filled eyes with endophthalmitis, but the interaction with oil is unclear. The purpose of the experiment is to determine whether vancomycin, amikacin, and amphotericin B mix with silicone oil.MethodsUsing the relative proportions of the human eye, 4 ml of 1000 centistokes silicone oil was centrifuged with 0.1 ml of vancomycin 1 mg/0.1 ml, amikacin 0.4 mg/0.1 ml, or amphotericin B 5 µg/0.1 ml in vitro and eluted. The aqueous was immediately analyzed with a liquid chromatographer/mass spectrometer and after 24 h.ResultsWithin 24 h, a mean of 26.9 μmol/L of vancomycin, 0 nmol/L of amikacin, and 0 nmol/L of amphotericin B were recovered. When the concentrations of amikacin and amphotericin B were increased 100-fold, 0 nmol/L of amikacin and 75.7 µmol/L of amphotericin B were recovered.ConclusionsVancomycin and amphotericin B partially mixed with the silicone oil. Amikacin was not recovered from the antibiotic–silicone oil mixture.

Clonal Dissemination of Clinical Isolates of Acinetobacter baumannii Carriers of 16S rRNA Methylase Genes in an Oncological Hospital in Recife, Brazil.

16S rRNA methylases confer high-level resistance to aminoglycosides which are used to treat serious infections caused by gram-negative bacteria, such as Acinetobacter spp. Some genes encoding these enzymes are disseminated worldwide, while others were detected in only some countries. The objective was to characterize the susceptibility profile to aminoglycosides (amikacin and gentamicin) of clinical isolates of Acinetobacter spp. from an oncological hospital in Recife, and given the resistance to both antimicrobials, to characterize minimal inhibitory concentrations (MICs) of amikacin, gentamicin and tobramycin, the occurrence of 16S rRNA methylase genes (armA, rmtB, rmtC and rmtD) and of ß-lactamase gene (blaKPC) and the clonal profile. Isolates resistant to both antimicrobials, amikacin and gentamicin, were selected by disk diffusion technique in Mueller-Hinton agar and identified. Broth microdilution was conducted to determine MICs of amikacin, gentamicin, and tobramycin. These isolates were subjected to polymerase chain reaction and pulsed-field gel electrophoresis. Among 23 analyzed isolates, 12 (52.2%) were resistant to gentamicin and amikacin and identified as Acinetobacter baumannii. Among these, 11 (91.7%), 12 (100%), and 9 (75%) isolates showed respectively MICs >256 µg/mL of amikacin, >64 µg/mL of gentamicin, and >64 µg/mL of tobramycin. The armA gene was found in 12 (100%) isolates and 6 (50%) showed coexistence of armA, rmtB, and rmtC genes. The rmtD and blaKPC genes were not detected. These isolates showed high genetic similarity (92%) and were classified as clone A. Elaboration and fulfillment of measures are thus essential to prevent the spread of this resistance mechanism.