Minimum Inhibitory Concentrations Of Amikacin Research Articles

Doxycycline post-exposure prophylaxis could theoretically select for resistance to various antimicrobials in 19 pathobionts: an in silico analysis

ObjectivesDoxycycline post exposure prophylaxis (PEP) has been shown to reduce the incidence of bacterial STIs. However, if there is genetic linkage between resistance to tetracycline and other antimicrobials, then it could also select for resistance to these other antimicrobials. We therefore undertook to evaluate if there is an association between the minimum inhibitory concentrations (MICs) of tetracycline and other antimicrobials in 19 clinically important bacterial species. MethodsMixed-effects linear regression was used to assess if minocycline MICs were associated with the MICs of eight other antimicrobials (ceftriaxone, ampicillin, oxacillin, vancomycin, erythromycin, levofloxacin, amikacin, and trimethoprim-sulfamethoxazole) in 19 bacterial species in the Antimicrobial Testing Leadership and Surveillance (ATLAS) database. ResultsWith the notable exception of vancomycin, where no association was found, strong positive associations were typically found between the MICs of minocycline and each of the eight antimicrobials in each of the species assessed. For example, the minocycline MICs of all the Gram-positive species were positively associated with ampicillin, ceftriaxone, oxacillin and erythromycin MICs (all P-values < 0.001). The only exceptions were ampicillin for Streptococcus pyogenes and ceftriaxone for S. dysgalactiae, where no significant associations were found. Similarly in the Gram-negative species, the minocycline MICs of all the species except Haemophilus influenzae and Stenotrophomonas maltophilia were positively associated with the MICs of ceftriaxone, ampicillin, levofloxacin and amikacin (all P-values < 0.001). ConclusionsThere is a theoretical risk that doxycycline PEP could select for resistance not only to tetracyclines but to a range of other antimicrobials in each of the 19 pathobionts assessed.

Diagnostic Performance of Genotype MTBDRsl Assay (Version 2) for Detecting 2nd Line Drug Resistance TB Compared to Sensititre MycoTBI MIC in MDR-TB Patients

Objective: The diagnostic test aimed to compare the GenoType MTBDRsl assay (version 2) and minimum inhibitory concentration (MIC) using a Sensititre MycoTBI MIC plate to detect quinolone and aminoglycoside resistance. Materials and Methods: One hundred thirty-three remaining samples from individuals diagnosed with multidrug-resistance tuberculosis (MDR-TB) and having tested positive for TB cultures between September 2016 and August 2021 were included in the present study. Results: The sensitivity, specificity, PPV, and NPV using GenoType MTBDRsl version 2 compared to MIC of levofloxacin at greater than 0.5 μg/mL were 87.5% (95% CI of 67.6 to 97.3), 98.16% (93.5 to 99.8), 91.30% (72.0 to 98.9), and 97.2% (92.2 to 99.4). Similarly, for moxifloxacin at 2 mg/dL or greater for resistance, the values were 95.4% (95% CI of 77.2 to 99.9), 98.2% (93.6 to 99.8), 91.3% (72.0 to 98.9), and 99.0% (95.0 to 100). The sensitivity, specificity, and diagnostic performances of GenoType MTBDRsl version 2 compared to the MIC of amikacin of greater than 4 μg/mL and kanamycin of greater than 5 μg/mL were 100% (95% CI of 54.1 to 100), 99.2% (95.7 to 100), 99.2% (42.1 to 99.6), and 85.7% (97.1 to 100). Two location mutations at D94G and D94 N/Y were related to a high level of fluoroquinolone with median MIC values of 8 μg/mL of levofloxacin and greater than 4 of moxifloxacin. The mutation at C-14T did not cause resistance in phenotypic patterns. Conclusion: GenoType MTBDRsl (version 2) and MIC determination using Sensititre MycoTBI MIC plate are consistent with each other. Keywords: Sensititre MycoTBI MIC plate; MTBDRsl assay (version 2); Quinolone resistance; Aminoglycoside resistance

Development and application of neonatal physiology-based pharmacokinetic models of amikacin and fosfomycin to assess pharmacodynamic target attainment.

Antimicrobial resistance increasingly complicates neonatal sepsis in a global context. Fosfomycin and amikacin are two agents being tested in an ongoing multicenter neonatal sepsis trial. Although neonatal pharmacokinetics (PKs) have been described for these drugs, the physiological variability within neonatal populations makes population PKs in this group uncertain. Physiologically-based pharmacokinetic (PBPK) models were developed in Simcyp for fosfomycin and amikacin sequentially for adult, pediatric, and neonatal populations, with visual and quantitative validation compared to observed data at each stage. Simulations were performed using the final validated neonatal models to determine drug exposures for each drug across a demographic range, with probability of target attainment (PTA) assessments. Successfully validated neonatal PBPK models were developed for both fosfomycin and amikacin. PTA analysis demonstrated high probability of target attainment for amikacin 15 mg/kg i.v. q24h and fosfomycin 100 mg/kg (in neonates aged 0-7 days) or 150 mg/kg (in neonates aged 7-28 days) i.v. q12h for Enterobacterales with fosfomycin and amikacin minimum inhibitory concentrations at the adult breakpoints. Repeat analysis in premature populations demonstrated the same result. PTA analysis for a proposed combination fosfomycin-amikacin target was also performed. The simulated regimens, tested in a neonatal sepsis trial, are likely to be adequate for neonates across different postnatal ages and gestational age. This work demonstrates a template for determining target attainment for antimicrobials (alone or in combination) in special populations without sufficient available PK data to otherwise assess with traditional pharmacometric methods.

Evaluating amikacin minimum inhibitory concentration in trailing growth for Mycobacterium avium complex

BackgroundAmikacin is a first-line drug that must be evaluated when performing an antimycobacterial susceptibility test (AST) for Mycobacterium avium complex (MAC). However, the presence of sporadic trailing growth in MAC makes determining the precise point for reading its minimal inhibitory concentration (MIC) challenging. MethodsSusceptibility was re-tested for 134 MAC clinical isolates using the Sensititre SLOMYCOI panel, the rrs gene was sequenced, and amikacin exposure history was investigated. The MIC50, MIC90, and the epidemiological cut-off value (ECOFF) were calculated using the EUCAST method. ResultsAfter re-testing and ignoring trailing growth, of the 22 M. intracellulare isolates originally classified as resistant to amikacin according to the CLSI guideline, 10 strains were reclassified as intermediate and four as susceptible. Similarly, from the seven resistant M. avium strains, one was reclassified as intermediate and four as susceptible. No rrs gene mutations were detected in any isolates, including resistant strains. When ignoring trailing growth, the calculated MIC50, MIC90, and ECOFF values closely aligned with the EUCAST MIC distribution. ConclusionTo maintain the current CLSI breakpoint, trailing growth should be ignored when reading the amikacin MIC of MAC. To read the MIC at complete bacterial inhibition, the CLSI breakpoint needs to be raised.

The Inhibitory Effects of Amylase and Streptokinase on Minimum Inhibitory Concentration of Antibiotics Used to Treat Gram Negative Bacteria Biofilm Infection on Indwelling Devices.

The study evaluated and compared the effect of adding streptokinase and amylase to antibiotics that are already used in clinical practice to treat Gram negative bacteria biofilm infection on indwelling devices on the antibiotics' minimum inhibitory concentration (MIC). 24h-old biofilms were developed on 96-well plate with eight clinical isolates. MIC of amikacin, cefepime, ceftazidime, colistin, meropenem, and piperacillin-tazobactam, on biofilms were measured before and after the addition of 25U/ml streptokinase and 25μg/ml amylase with microplate reader. The addition of streptokinase reduces the MICs of cefepime, ceftazidime, colistin, meropenem from (16, 16, 8, 4μg/ml) to (8, 1, 1, 0.5μg/ml) in Escherichia coli (isolate 1). While the addition of amylase reduces the MICs of only cefepime, ceftazidime from (16, 16μg/ml) to (2, 4μg/ml) in E. coli (isolate 1). In Pseudomonas aeruginosa (isolate 4), the MICs of amikacin, cefepime, ceftazidime, colistin and meropenem (64, 16, 32, 4, 32μg/ml) reduced to (2, 1, 0.5, 0.25, 0.5μg/ml) with streptokinase and (4, 4, 4, 2, 0.5μg/ml) with amylase respectively. Similar inhibitions were seen in Pseudomonas putida, Proteus mirabilis. We can conclude that the addition of streptokinase and amylase were effective in reducing the MICs of antibiotics that are commonly used to treat Gram negative bacteria biofilm infection on indwelling devices, thereby increasing susceptibility of bacteria to antibiotics. Streptokinase obviously had a greater effect than amylase, implying that it should be prioritized in future in vivo and clinical studies to obtain successful therapy with antibiotics on biofilm infections.

Comparing minimum inhibitory concentrations of amikacin for pulmonary Mycobacterium avium complex disease: An analysis of culture media differences

Mycobacterium avium complex (MAC) is considered a paramount microbe, especially in East Asia, including Japan. The commonly used commercial Minimum Inhibitory Concentrations (MIC) assay using Middlebrook 7H9 (7H9) medium deviates from the latest Clinical and Laboratory Standards Institute (CLSI) guidelines. Alternatively, measurement with cation-adjusted Mueller-Hinton broth (CAMHB) that conforms to CLSI standards is not yet widely available. Following the approval and commercialization of amikacin liposome inhalation suspension (ALIS) in 2021, a more precise evaluation of amikacin (AMK) susceptibility in MAC is necessary for treatment decisions. In the present study, 33 sputum samples were extracted from 27 patients, and MICs of AMK were compared between the frequently used 7H9 and the recommended CAMHB of the isolated MAC strains. The history of exposure to aminoglycosides for each sample was also added as clinical information. The findings indicated that there was only an 18% concordance rate in MIC between the two media, with 19 samples (58%) indicating lower MICs in 7H9 relative to CAMHB. The 17 samples had a history of exposure to aminoglycosides for periods ranging from 1.5 to 28 months. Specifically, 10 samples were exposed to amikacin by inhalation and intravenous injection, and the remaining seven samples had a history of ALIS inhalation. Samples with a prior utilization of aminoglycosides were significantly predisposed to developing resistance to ALIS compared to those without such a history (P = 0.046). Physicians are encouraged to scrutinize the findings of susceptibility testing utilizing CLSI-endorsed MIC assay using CAMHB medium to ascertain the optimal therapeutic approach.

Discovery of Novel Resistance Mechanisms of Vibrio parahaemolyticus Biofilm against Aminoglycoside Antibiotics.

Inappropriate use of antibiotics eventually leads to the emergence of antibiotic-resistant strains and invalidates the treatment of infectious diseases. Aminoglycoside antibiotics (AGAs) are a class of broad-spectrum cationic antibiotics widely used for the treatment of Gram-negative bacterial infections. Understanding the AGA resistance mechanism of bacteria would increase the efficacy of treating these infections. This study demonstrates a significant correlation between AGA resistance and the adaptation of biofilms by Vibrio parahaemolyticus (VP). These adaptations were the result of challenges against the aminoglycosides (amikacin and gentamicin). Confocal laser scanning microscope (CLSM) analysis revealed an enclosure type mechanism where the biological volume (BV) and average thickness (AT) of V. parahaemolyticus biofilm were significantly positively correlated with amikacin resistance (BIC) (p < 0.01). A neutralization type mechanism was mediated by anionic extracellular polymeric substances (EPSs). The biofilm minimum inhibitory concentrations of amikacin and gentamicin were reduced from 32 µg/mL to 16 µg/mL and from 16 µg/mL to 4 µg/mL, respectively, after anionic EPS treatment with DNase I and proteinase K. Here, anionic EPSs bind cationic AGAs to develop antibiotic resistance. Transcriptomic sequencing revealed a regulatory type mechanism, where antibiotic resistance associated genes were significantly upregulated in biofilm producing V. parahaemolyticus when compared with planktonic cells. The three mechanistic strategies of developing resistance demonstrate that selective and judicious use of new antibiotics are needed to win the battle against infectious disease.

Distribution of MIC values of antibacterial drugs for Flavobacteriales isolated from respiratory samples in Russian patients with cystic fibrosis

Objective. Analysis of the distribution of the values of the minimum inhibitory concentrations (MIC) of a number of antibacterial drugs in relation to representatives of the order Flavobacteriales isolated from respiratory samples from patients with cystic fibrosis of the Russian Federation by the method of double serial dilutions. Materials and Methods. The distribution of the values of MIC of a number of antibacterial drugs was evaluated in relation to 100 strains of bacteria, representatives of the order Flavobacteriales, isolated from respiratory samples from patients with cystic fibrosis from 60 regions of the Russian Federation as part of a routine microbiological examination. Of these, 75 representatives of Chryseobacterium spp., among which C. arthrospherae – 28, C. formosense – 1, C. gambrini – 3, C. gleum – 10, C. indologenes – 20, C. joostei – 1, C. oraniemense – 10, C. shandongense – 2 strains, 4 strains of Elizabethkingia spp., among which 2 – E. miricola, and one strain of E. meningoseptica and E. anopheles, respectively, as well as 21 strains of E. falsenii. Identification of all isolated cultures was carried out using MALDI-ToF mass spectrometry (Bruker, Germany). The MIC values were determined for 17 antimicrobial drugs: amikacin, amoxicillin/clavulanate, aztreonam, cefotaxime, ceftazidime, ceftazidime/avibactam, ceftolozane/ tazobactam, ciprofloxacin, colistin, ertapenem, gentamicin, imipenem, meropenem, piperacillin/ tazobactam, tigecycline, tobramycin and trimethoprim/sulfamethoxazole using Sensititre kits DKMGN. Results. The MIC values of colistin, cefotaxime and tobramycin more than 8 µg/ml, as well as more than 2 µg/ml with respect to ertapenem was demonstrated for 100% of isolates. For most strains, the MIC values of imipenem and meropenem were more than 4 µg/ml. MIC of ceftazidime against 20% of Chryseobacterium spp. strains was up to 2 µg/ml. Indicators of MIC of amikacin in relation to Elizabethkingia spp. strains were 32 µg/ml or more. For 38% of the strains of Chryseobacterium spp. and E.falsenii, this value did not exceed 8 µg/ml. As in the case of amikacin, all Elizabethkingia spp. strains demonstrated high levels of gentamicin MIC – 8 µg/ml (25% of strains) and more (75% of strains). For 20% of all tested strains, the MIC value was in the range of ≤ 2 µg/ml. In relation to half of the tested isolates, the MIC values for ceftazidime/avibactam, as well as ceftolozane/tazobactam were at the level of up to 2⁄4 µg/ml inclusive. More than a third of the strains had a level of MIC ciprofloxacin up to 0.25 µg/ml inclusive. For 25% of strains, the level of MIC of tigecycline was up to 0.5 µg/ml, inclusive, the lowest MIC indicators for the tested group of strains were demonstrated for trimethoprim/sulfamethoxazole: for 88% of strains, the MIC value was ≤ 1⁄19 µg/ml, for another 9% of strains, this indicator was 2⁄38 µg/ml. Conclusions. Representatives of the order Flavobacteriales are a group of microorganisms characterized by multiple antibiotic resistance. Most strains isolated from patients with cystic fibrosis in the Russian Federation retain low MIC values for trimethoprim/sulfamethoxazole.

Biofilm Formation of Staphylococcus aureus from Pets, Livestock, and Wild Animals: Relationship with Clonal Lineages and Antimicrobial Resistance.

This study aimed to compare the biofilm formation ability of Staphylococcus aureus isolated from a wide range of animals and study the association between biofilm formation and antimicrobial resistance and genetic lineages. A total of 214 S. aureus strains isolated from pets, livestock, and wild animals were evaluated regarding their ability to form biofilms by the microtiter biofilm assay and their structure via confocal scanning laser microscopy. Statistical analysis was used to find an association between biofilm formation and antimicrobial resistance, multidrug resistance, sequence types (STs), spa and agr-types of the isolates. The antimicrobial susceptibility of 24 h-old biofilms was assessed against minimum inhibitory concentrations (MIC) and 10× MIC of amikacin and tetracycline, and the biomass reduction was measured. The metabolic activity of biofilms after antimicrobial treatment was evaluated by the XTT assay. All isolates were had the ability to form biofilms. Yet, significant differences in biofilm biomass production were detected among animal species. Multidrug resistance had a positive association with biofilm formation as well as methicillin-resistance. Significant differences were also detected among the clonal lineages of the isolates. Both tetracycline and amikacin were able to significantly reduce the biofilm mass. However, none of the antimicrobials were able to eradicate the biofilm at the maximum concentration used. Our results provide important information on the biofilm-forming capacity of animal-adapted S. aureus isolates, which may have potential implications for the development of new biofilm-targeted therapeutics.

PHENOTYPIC DETECTION OF EFFLUX MECHANISM IN AMIKACIN-RESISTANT ACINETOBACTER ISOLATES FROM TWO DIFFERENT STATES IN SOUTH INDIA

Acinetobacter has already gained resistance to the majority of antibiotics available. Aminoglycosides are commonly used to treat invasive infections. Aminoglycoside resistance is associated with decreased drug absorption, aminoglycoside modification, and aminoglycoside efflux. The aim of this study was to detect the presence of an efflux mechanism in amikacin-resistant Acinetobacter isolated from hospital wards using Carbonyl Cyanide 3- Chlorophenylhydrazone (CCCP). One hundred isolates of Acinetobacter were isolated from tertiary care hospitals in two distinct South Indian states. Antibacterial susceptibility patterns were discovered between 2017 and 2019. Amikacin minimum inhibitory concentration (MIC) for resistant Acinetobacter isolates was determined using Clinical and Laboratory Standards Institute (CLSI) standards. The efflux system activity was determined using CCCP. Among 100 Acinetobacter baumannii isolates, 49 isolates with amikacin resistance were found. The MIC’s of Acinetobacter ranged between 2 – 1024 μg/mL for the amikacin studied. After treatment with the efflux pump inhibitor, 38.77% of isolates became less resistant to amikacin, as determined by phenotypic detection of efflux pumps, showing a decrease in antibiotic MICs of at least four fold. The data demonstrated the importance of efflux pump activity conferring amikacin resistance on Acinetobacter clinical isolates.

Amikacin for the treatment of carbapenem-resistant Klebsiella pneumoniae infections: clinical efficacy and toxicity

Infections by carbapenem-resistant Klebsiella pneumoniae (CRKp) are an increasing global threat with limited therapeutic options. Our objective was to evaluate clinical and microbiological outcomes of patients treated with amikacin for CRKp infections. We did a retrospective cohort of patients > 18years old, with CRKp infections treated with amikacin in two tertiary care hospitals in Porto Alegre, Brazil. The impact of clinical factors, antibiotic treatment, and amikacin minimum inhibitory concentration (MIC) on patients' 30-day mortality was assessed. Microbiological clearance and nephrotoxicity (assessed by RIFLE score) were evaluated as secondary outcomes. A Cox regression analysis was done for mortality. We included 84 patients for analysis. Twenty-nine (34.5%) patients died in 30days. Amikacin MIC values ranged from 0.125 to 8μg/mL and did not influence on mortality, regardless of the prescribed dose of this antibiotic (P = 0.24). Bacterial clearance occurred in 17 (58.6%) of 29 patients who collected subsequent cultures. Two (16.6%) of the 12 persistently positive cultures changed the amikacin susceptibility profile from susceptible to intermediate. Twenty-nine (37.2%) patients developed acute kidney injury (AKI): risk 13, injury 11, and failure 5. Risk factors for AKI were higher baseline eGFR (P < 0.01) and combination therapy with colistin (P = 0.02). Comparing patients who received combination with colistin vs polymyxin B, AKI occurred in 60.0% vs 20.6%, respectively, P < 0.01. Fifteen of the 16 (16.6%) patients who developed renal injury or failure were receiving colistin. In conclusion, amikacin was an effective treatment for CRKp infections. Within susceptible range, amikacin MIC values did not influence on clinical outcomes. Combination therapy of amikacin and colistin was highly nephrotoxic and should be used with caution.

Chlorhexidine leads to the evolution of antibiotic-resistant Pseudomonas aeruginosa.

Antimicrobial resistance is a major public-health concern. We evaluate chlorhexidine role in selection of resistant Pseudomonas aeruginosa mutants and their antibiotic cross-resistance. Mutation frequency and mutation rate after short-term exposure to sub-inhibitory concentrations of chlorhexidine were compared to those after spontaneous chlorhexidine-exposure, in P. aeruginosa PAO1 strain. Chlorhexidine-resistant mutants were generated, either by serial passage in increasing chlorhexidine concentrations or by single exposure to lethal chlorhexidine concentration. The generated mutants were tested for cross-resistance to different antibiotics, by determination of minimum inhibitory concentrations (MIC). The accompanied phenotypic changes in membrane permeability, outer membrane proteins (OMP), and efflux function were evaluated. The effect of exposure to chlorhexidine on MexAB-OprM, MexEF-oprN, and MexXY efflux pumps expression was investigated. No significant change was recorded between the mutation frequencies and mutation rates after short-term exposure to sub-inhibitory concentrations of chlorhexidine and after spontaneous chlorhexidine-exposure, in P. aeruginosa PAO1 strain. Twelve stable mutants, with ≥ eight-fold increase in chlorhexidine MIC, were generated. Several mutants showed increase in the MIC of colistin, cefepime, ceftazidime, meropenem, ciprofloxacin, and amikacin; seven mutants expressed meropenem cross-resistance. This was accompanied by decreased outer membrane permeability and changes in OMP. Using efflux pump inhibitor, chlorhexidine resistance was reverted in most isolates. Exposure to sub-inhibitory concentration of chlorhexidine induced the expression of MexXY efflux pump. Some resistant mutants had overexpressed MexXY efflux pump. Chlorhexidine can select P. aeruginosa strains with antibiotic cross-resistance. This necessitates implementing special protocols for chlorhexidine use and re-evaluation of its benefit versus risk in personal-care products.

Drug sensitivity of low growing non-­­tuberculous mycobactria

Objective — analysis of drug resistance (DR) of some types of low growing non-­tuberculous mycobactria (NTMB) by the method of double serial microdilutions of drugs of different groups to determine the minimum inhibitory concentra­tions (MIC) in a liquid culture medium using the TREK Diagnostic Systems test system, Thermo Scientific SLOWMYCO for low growing mycobacteria.&#x0D; Materials and methods. Investigated 122 strains of low growing NTMB (M. avium, M. intracellulare, M. gordonae, M. kansasii, M. xenopi, M. malmoense and M. simiae), which were isolated in a liquid nutrient medium during sputum inoculation. DR was determined by the culture method using the TREK Diagnos­tic Systems kits (panel for low growing NTMB, which allows to determine the MIC of 13 drugs). The results were interpreted using an automatic bacteriological analyzer Sensititre Vizion System TREK Diagnostic Systems (USA).&#x0D; Results and discussion. Was found that for most M. avium strains the MIC of amikacin was 16.0—32.0 µg/ml, for ciprofloxacin — 16.0 µg/ml and higher, clarithromycin — 2.0—4.0 µg/ml, doxycycline — 16.0 µg/ml and above, ethambutol — 8.0—16.0 µg/ml. The MIC spectrum of ethionamide was distributed in the range from 1.2 to more than 20.0 µg/ml. MIC of isoniazid for most strains of M. avium was more than 8.0 µg/ml, linezolid — 16.0—32.0 µg/ml, moxifloxacin — 2.0—4.0 µg/ml, rifabutin — 0.25 µg/ml, rifampicin 4.0 µg/ml and above, streptomycin 64 µg/ml and above, and trimethoprim/sulfamethoxazole — more than 8.0/152 µg/ml. For M. intracellulare strains, in general, a similar situation with the M. avium strains with the MIC spectrum was observed. The work also provides MICs for the strains M. gordonae, M. kansasii, M. xenopi, M. simiae and M. malmoense. Based on the determination of the DR, the MIC50 and MIC90 values of each preparation of the SLOWMYCO panel were calculated for the studied species of low growing NTMB. Comparison of the MIC50 and MIC90 values with the limiting drug concentrations made it possible to determine the drugs effective against the studied types of NTMs.&#x0D; Conclusions. Determination of DR by the micromethod of serial dilutions in a liquid nutrient medium showed that most of the studied strains of low growing NTMPs are sensitive to clarithromycin and rifabutin. Amikacin, linezolid, and moxifloxacin were also quite effective. At the same time, drugs such as ethambutol, isoniazid, streptomycin, trimethoprim/sulfamethoxazole, suppressed the growth of the studied strains mainly in high concentrations, significantly exceeding the critical one.Until now, there is no single criterion for determining the DR NTM, and for the method used in this work, recommended by the Institute for Clinical and Laboratory Standards (USA), there are limitations in the interpretation of the results due to the untreated limit concentrations of drugs for various types of NTM. This is especially true for MAC, which play a major role in the development of mycobacteriosis. It was shown that the resistance profile of M. avium strains included the largest number of SLOWMYCO panel preparations compared to other types of NTMB, which dictates the need for studies aimed at comparing the results of in vitro DST with the effectiveness of therapy.

Invitro activity of arbekacin against multidrug-resistant gram-negative bacilli.

Arbekacin is a broad-spectrum aminoglycoside with activity against some Gram-positive and Gram-negative bacteria. Arbekacin minimum inhibitory concentration (MIC) values were determined for 296 drug-resistant Gram-negative bacilli, and compared to previously determined plazomicin, amikacin, gentamicin, and tobramycin MIC values. The MIC values required to inhibit 50% and 90% of isolates (MIC50 and MIC90, respectively) were 16 and >128 μg/ml, respectively. Arbekacin showed similar MIC50 values to amikacin and gentamicin, a lower MIC50 value than tobramycin, and a higher MIC50 value than plazomicin.

Synergistic Effect of Tazobactam on Amikacin MIC in Acinetobacter baumannii Isolated from Burn Patients in Tehran, Iran

Burn is still an important global public health challenge. Wound colonization of antibiotic resistant bacteria such as Acinetobacter baumannii can lead to high morbidity and mortality in burn patients. The aim of this study was to evaluate the inhibitory effect of tazobactam on efflux pump, which can cause aminoglycoside resistant in A. baumannii isolated from burn patients. In this study, 47 aminoglycoside resistant A. baumannii spp. were obtained from burn patients, admitted to the Shahid Motahari Burns Hospital in Tehran, Iran, during June-August 2018. The inhibitory effect of tazobactam against adeB such as efflux pump was evaluated by minimum inhibitory concentration (MIC) determination of amikacin alone and in combination with tazobactam. Fractional inhibitory concentration index (FIC) was used to determine the efficacy of tazobactam/amikacin combination. Further, semi-quantitative Real- Time PCR was performed to quantify the expression rates of the adeB gene before and after addition of tazobactam/amikacin. The MIC values were significantly reduced when a combined amikacin and tazobactam was utilized. The most common interaction observed was synergistic (78.2%), followed by additive effects (21.8%), as per FIC results. The adeB mRNA expression levels were found to be downregulated in 60.7% of isolates treated with tazobactam. Tazobactam can have impact on resistance to aminoglycoside by inhibiting efflux pump. Thus, the combination of tazobactam with amikacin can be used as an alternative treatment approach in multidrug resistant A. baumannii infections.

Carbapenem-Resistant Klebsiella pneumoniae Outbreak in a Neonatal Intensive Care Unit: Risk Factors for Mortality.

The aim of our study was to determine the factors associated with mortality in neonates with carbapenem-resistant Klebsiella pneumoniae (CRKP). This retrospective, single-center study was conducted in the Neonatal Intensive Care Unit of Harran University Faculty of Medicine between January 2017 and July 2018 who had CRKP growth in their blood, urine or cerebrospinal fluid cultures. The discharged group was designated as the control group (Group 1), whereas the group that faced mortality was classified as the case group (Group 2). The demographic data, clinical findings and laboratory and microbiological results of the two groups were compared to identify risk factors. A total of 58 patients (36 in Group 1 and 22 in Group 2) exhibited CRKP growth during the study period. Low birth weight (p = 0.039), previous antifungal (p = 0.002) or amikacin use (p = 0.040), congenital anomalies (p = 0.002), total parenteral nutrition (TPN) administration (p = 0.002), surgery (p = 0.035), thrombocytopenia (p = 0.007), low platelet mass index (p = 0.011), elevated C-reactive protein (p = 0.004), high carbapenem minimum inhibitory concentration (MIC) (p = 0.029) and high amikacin MIC (p = 0.019) were associated with mortality. In a multivariate regression analysis, previous antifungal use (p = 0.028), congenital anomalies (p = 0.032) and TPN use (p = 0.013) were independent factors in predicting mortality. Previous antifungal use, congenital anomalies and TPN use were found to be independent risk factors for mortality in neonates with CRKP infection.

Evaluation of antibacterial and enhancement of antibiotic action by the flavonoid kaempferol 7-O-β-D-(6″-O-cumaroyl)-glucopyranoside isolated from Croton piauhiensis müll

There has been a rapid increase in the incidence and prevalence of opportunistic bacterial infections. Inappropriate use of current antibiotics has continuously contributed to the emergence of resistance to conventional antibiotic therapy. Therefore, the search for natural molecules that are able to combat infections is of great public interest, and many of these compounds with antimicrobial properties can be obtained from phytochemical studies of medicinal plants. In this context, this study reports the isolation and characterization of the flavonoid, kaempferol 7-O-β-D-(6″-O-cumaroyl)-glucopyranoside, from Croton piauhiensis leaves. Additionally, the intrinsic antimicrobial action of the compound and its enhancement against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains were assessed. The minimum inhibitory concentration (MIC) of the compound was determined using broth microdilution assays. To evaluate the modulatory effect of the flavonoid, the MIC of antibiotics amikacin and gentamicin, belonging to the class aminoglycosides was assessed, with and without the compound in sterile microplates. The results of intrinsic antibacterial activity tests revealed that the compound had no antibacterial activity against strains tested at concentrations <1024 μg/mL. The combination of the flavonoid at a concentration of 128 μg/mL with gentamicin presented synergistic effects against S. aureus 10 and E. coli 06, and also reduced the MIC from 16 μg/mL to 4 μg/mL and 8 μg/mL, respectively. Amikacin also showed synergistic effects against S. aureus 10 and E. coli 06. We also observed reduced MIC for both, from 128 μg/mL to 32 μg/mL; however, antagonism for P. aeruginosa increased the MIC from 16 μg/mL to 64 μg/mL. The combination of the flavonoid with the aminoglycosides may be an alternative to potentiate the expected results in treatment against S. aureus and E. coli, since their association leads to a synergistic effect, reducing the MIC of these drugs and decreasing the dose necessary for therapeutic success.

Comparison of the Effect of Phenylalanine Arginine Beta Naphthylamide (PAβN) and Curcumin on Minimum Inhibitory Concentration of Aminoglycosides on Pseudomonas aeruginosa Clinical Isolates

Background and Objective: Efflux pump inhibitors (EPIs) can block efflux pumps and are helpful in potentiating the activity of aminoglycosides against Pseudomonas aeruginosa. The present study compared the effects of phenylalanine-arginine beta naphthylamide (PAβN) and curcumin on aminoglycoside minimum inhibitory concentration (MIC) on Pseudomonas aeruginosa clinical isolates. Materials and Methods: For this descriptive-analytical study, 100 clinical isolates of Pseudomonas aeruginosa were collected and identified by differential diagnostic tests. The MICs of amikacin, gentamicin, and tobramycin were evaluated before and after adding EPIs using a micro-broth dilution test. Results: The bacteria were isolated from different types of samples, including urine (26 isolates), sputum (37 isolates), ulcers (20 isolates), catheters (eight isolates), blood (five isolates), feces (two isolates), and eyes (two isolates). Overall, 60 of the isolates were obtained from males (mean age = 47.85), and 40 from females (mean age = 44.76). In the MIC test, 11 (25.5), 15 (34.8), and 18 (41.8) isolates were resistant to amikacin, gentamicin, and tobramycin, respectively. Significant reductions in the MICs of amikacin, gentamicin, and tobramycin were observed after adding curcumin in 54-100 of aminoglycoside-resistant isolates, while fewer changes in the MICs of aminoglycosides were seen against these clinical isolates after adding PAβN (36-55). Conclusion: Curcumin and PAβN can potentiate the effect of aminoglycosides on clinical isolates of Pseudomonas aeruginosa and change their susceptibility pattern due to efflux pump inhibition. However, our outcomes detected that curcumin was more effective than the PAβN against the aminoglycoside-resistant isolates of P. aeruginosa.

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.

13-(2-Methylbenzyl) Berberine Is a More Potent Inhibitor of MexXY-Dependent Aminoglycoside Resistance than Berberine.

We previously showed that berberine attenuates MexXY efflux-dependent aminoglycoside resistance in Pseudomonas aeruginosa. Here, we aimed to synthesize berberine derivatives with higher MexXY inhibitory activities. We synthesized 11 berberine derivatives, of which 13-(2-methylbenzyl) berberine (13-o-MBB) but not its regiomers showed the most promising MexXY inhibitory activity. 13-o-MBB reduced the minimum inhibitory concentrations (MICs) of various aminoglycosides 4- to 128 fold for a highly multidrug resistant P. aeruginosa strain. Moreover, 13-o-MBB significantly reduced the MICs of gentamicin and amikacin in Achromobacter xylosoxidans and Burkholderia cepacia. The fractional inhibitory concentration indices indicated that 13-o-MBB acted synergistically with aminoglycosides in only MexXY-positive P. aeruginosa strains. Time-kill curves showed that 13-o-MBB or higher concentrations of berberine increased the bactericidal activity of gentamicin by inhibiting MexXY in P. aeruginosa. Our findings indicate that 13-o-MBB inhibits MexXY-dependent aminoglycoside drug resistance more strongly than berberine and that 13-o-MBB is a useful inhibitor of aminoglycoside drug resistance due to MexXY.