Nature, a rich source of bioactive natural products, serves as a massive pool of drug candidates for the pharmaceutical industry. However, the supply of these structurally complex chemicals is costly as most of the natural products are scarce in nature, thus requiring de novo synthesis. The supply chain issue hinders the development of novel therapeutic agents from natural products. Microbial synthesis, based on the expression of biosynthetic genes in a suitable microbial host to produce certain chemicals, is a sustainable strategy to produce complex natural products. However, this strategy requires gaining insights into the biosynthesis of target molecules. Most natural products are biosynthetically unknown or not fully elucidated; thus, the sole application of microbial synthesis strategy to produce a given molecule is challenging. In this review, we highlight a strategy that combines microbial and chemical syntheses to tackle the supply chain issue in developing drugs from natural products. We believe this strategy can revive the drug development pipeline for natural products.
Biological Products/chemistry* ; Aminoglycosides

BACKGROUND: High-level gentamicin and streptomycin disks are not easily available, despite their critical role in detection of high-level resistance to aminoglycosides in enterococci. Therefore, the possibility of applicating home-made disks to test high-level resistance of enterococci to aminoglycosides was evaluated. METHODS: The disk diffusion method using home-made disks was compared with minimal inhibitory concentrations(MIC) in 53 clinical isolates of enterococci, and, the stability of the disks were also evaluated by disk diffusion testing, biweekly, for 14 weeks. RESULTS: The high-level resistance rates to gentamicin(GM) and streptomycin(SM) were 60% and 43%, respectively. Thirty eight % of the enterococci were highly resistant in both GM and SM. The results of the disk diffusion method were consistent with the MIC until 10 weeks after production of the disks. After 12 weeks, the inhibition zones of GM- or SM-susceptible strains decreased by 2.9-3.9 mm, and the discrepancy rates were 5-24% between the results of the MIC and disk diffusion method. The storage temperature of -20degrees C versus -70degrees C showed no difference in the inhibition zone. CONCLUSION: It has been demonstrated that home-made high-level GM and SM disks are stable at -20degrees C for 10 weeks, and the results of disk diffusion method on the disks show they are applicable for the test of susceptibility of aminoglycosides to enterococci.
Aminoglycosides ; Diffusion ; Enterococcus ; Gentamicins ; Streptomycin

As an important aminoglycosides antibiotic, gentamicin has been used clinically over decades. With the development in modern biological technology, the mechanisms of gentamicin action and resistance, its biosynthesis and structural modification were studied in great depth. Meanwhile, its emerging novel bioactivities and potential applications are also under extensive exploration. Here we summarize the latest progresses and prospects towards the future development of gentamicin for more efficient and effective uses.
Aminoglycosides ; biosynthesis ; chemistry ; Gentamicins ; biosynthesis ; chemistry

Since the characteristics of aminoglycoside ototoxicity is typically bilaterally symmetric progression of cochlea-vestibular dysfunction, a unilateral involvement has rarely been reported. However, ototoxicity can be asymmetric or focal after systemic aminoglycoside treatment. The authors report 2 cases of asymmetric or focal audiovestibular deficits in patients treated with systemic aminoglycoside. In such cases, further investigations are also necessary to rule out other possible causes of unilateral sensorineural hearing loss such as cerebellopontine angle tumors.
Aminoglycosides ; Hearing Loss, Sensorineural ; Humans ; Neuroma, Acoustic

We analysed retrospectively pharmacokinetic parameters of gentamicin and amikacin in 44 and 58 Korean pediatric patients, respectively, with normal renal function. Pharmacokinetic parameters were calculated from two concentrations in serum by method of Sawchuck. There was wide individual variation in peak serum concentrations of gentamicin and amikacin, Administration of the usually recommended doses yielded subtherapeutic concentrations in 47% and 82%, respectevely, of patients in the peak concentrations of gentamicin and amikacin. The volumes of distribution of gentamicin and amikacin in children of over 1 year of age were 0.37+/-0.13L/kg and 0.41+/-0.13L/kg which are greater than those reported from the western countries. We conclude that the wide individual variation and high frequency of subtherapeutic levels in the peak concentrations of gentamicin and amikacin obtained by usually recommended dosage as well as the narrow safety margin of these drugs necessitate monitoring of serum concentration and adjustment of individual dosage regimen early in the course of treatment with aminoglycosides.
Amikacin* ; Aminoglycosides ; Child* ; Gentamicins* ; Humans ; Pharmacokinetics* ; Retrospective Studies

BACKGROUND: The aim of this study was to evaluate antibiotic consumption by adult patients at a single university hospital in Korea between 2001 and 2012. METHODS: We used the 2004 World Health Organization Anatomical Therapeutic Chemical Classification System definition of defined daily doses (DDD) per 1,000 patient-days to calculate the annual antibiotic consumption for 18 antibiotic groups. Chi-square linear-by-linear analysis was performed to evaluate antibiotic consumption trends for each group. RESULTS: Average annual antibiotic consumption during 2001-2012 was 644.6 DDD/1,000 patient-days (standard deviation, 33.3 DDD/1,000 patient-days). Although no statistically significant change was observed during the study period, consumption of first- and second-generation cephalosporins, and aminoglycosides was significantly decreased, while that of beta-lactam/beta-lactamase inhibitors, fourth-generation cephalosporins, carbapenem, glycopeptide, linezolid, colistin, and quinolone increased significantly. CONCLUSION: The total amount of prescribed antibiotics did not change, but the use of broad-spectrum antibiotics increased during the study period.
Adult ; Aminoglycosides ; Anti-Bacterial Agents ; Cephalosporins ; Classification ; Colistin ; Hospitals, University ; Humans ; Korea ; World Health Organization ; Linezolid

Aminoglycosides are one of the clinically relevant antibiotics. They kill bacteria by binding to bacterial 30S subunit of ribosome. Resistance to aminoglycosides occurs by three different mechanisms: 1. Production of an enzyme that modifies aminoglycosides, 2. Impaired entry of aminoglycoside into the cell by altering the OMP permeability, decreasing inner membrane transport, or active efflux, 3. The receptor protein on the 30S ribosomal subunit may be deleted or altered as a result of a mutation. By far, enzymatic modification has been the most important mechanism. In this review, the mechanisms of action and resistance, and the prevalence of resistance due to acquisition of enzymes are briefly described.
Aminoglycosides ; Anti-Bacterial Agents ; Bacteria ; Membranes ; Permeability ; Prevalence ; Ribosome Subunits ; Ribosomes

Spiramycin (SP) belongs to the 16-member macrolide antibiotics. It contains three components,namely SP I, SP II and SP III, which differ structurally in the acylation moieties on the C3 of the lactone. The SP I component contains a hydroxyl group at C3. SP II, and SP III are formed by further acetylation or propionylation of the C3 of SP I, by the same 3-O-acyltransferase (3-O-AT) . The study focused on simplifying spiramycin components. Theoretically, disruption/deletion of the 3-O-AT gene will reduce/stop the acylation of SP I to SP II and SP III. In this study, degenerated primers were designed according to the conserved regions of 3-O-acyltransferase, MdmB and AcyA in the medicamycin and carbomycin producers of S. mycarofaciens and S. thermotolerans, respectively, and an 878bp DNA fragment was amplified from the spiramycin-producer of S. spiramyceticus F21. Blast analysis of the 878bp DNA fragment suggested that it encoded the 3-O-acyltransferase (3-0-AT, sspA) gene for spiramycin biosynthesis. The flanking regions of this 878bp DNA fragment were then amplified by single-oligonucleotide-nested PCR, and a total of 4.3 kb DNA was obtained (3457nt among the 4.3kb fragment was sequenced, and deposited in GenBank DQ642742),covering the whole putative 3-O-acyltransferase gene, sspA. The sspA was then deleted from the S. spiramyceticus F21 genome by double cross-over homologous recombination, mediated by temperature-sensitive plasmid pKC1139. A comparison was done of the components of spiramycins produced by the sspA-deleted mutant strain with that of the parent strain by HPLC analysis, which showed that sspA-deleted mutant produced SP I (72%), SP II (18%), and SP III (9.6%), whereas parent strain produced SP I (7.8%), SP II (67%), and SP III (25%), respectively, demonstrating the role of ssp A in the acylation of SP I into SP II and SP III. The ssp A-deleted mutant strain obtained in this study may be used for the production of SP I, or may serve as a good starter for the construction of spiramycin derivatives.
Acyltransferases ; genetics ; Aminoglycosides ; biosynthesis ; Gene Deletion ; Genes, Bacterial ; genetics ; Genetic Engineering ; methods ; Streptomyces ; enzymology ; genetics

AIMTo analyze if the response factors of different aminoglycoside antibiotics detected by evaporative light-scattering detector (ELSD) are the same. If they are, then ELSD can be applied to the quality analysis of this class of antibiotics.

METHODSThe response factors of five different aminoglycosides (amikacin, sisomicin, netilmicin, etimicin and vertilmicin) detected by ELSD were determined by using a Diamonsil C18 column (150 mm x 4.6 mm, 5 microns) as analytical column and 0.2 mol.L-1 trifluoroacetic acid-methanol (94:6) as mobile phase at a flow rate of 0.6 mL.min-1, the temperature of the drift tube was set at 110 degrees C, and the flow of carrier gas at 2.80 L.min-1. Detector responses (A) and the amount of injection of each substance (m) were fitted to the logarithmic regression: logA = blogm + loga.

RESULTSThe linear regression equation obtained were amikacin: Y = 1.46X + 5.07, gamma = 0.9997; sisomicin: Y = 1.51X + 5.03, gamma = 0.9997; netilmicin: Y = 1.52X + 4.88, gamma = 1.000; etimicin: Y = 1.46X + 4.85, gamma = 0.9999; vertilmicin: Y = 1.41X + 4.90, gamma = 0.9998. The differences between them were negligible.

CONCLUSIONDifferent aminoglycosides can give the same responses with ELSD detection. So, the HPLC-ELSD methods can be applied to the analysis of impurities, the control of the ratio of multi-components drug and the determination of new substances by using another substance as reference, etc.

BACKGROUND: Aminoglycosides are useful for the treatment of aerobic gram-negative infections, and this is despite the narrow therapeutic index and the potential nephrotoxicity and ototoxicity. Once daily dosing of aminoglycosides has recently been suggested as an alternative method to multiple daily dosing. We compared the two dosing regimens of aminoglycosides for the development of nephrotoxicity. METHODS: This study was conducted as part of an ongoing quality improvement program. For the administration of aminoglycosides in adult patients with suspected or documented gram-negative infection, multiple daily dosing was used until April 2005 and thereafter once daily dosing was recommended. RESULTS: A total of 85 patients who received aminoglycoside for more than 3 days from March to August 2005 were available for analysis (40 in the once daily dosing group and 45 in the multiple daily dosing group). The mean duration of administration was 7.7 (range: 3-19) days in the once daily dosing group and 8.0 (range: 3-31) days in the multiple daily dosing group (p=0.83). Aminoglycoside-associated nephrotoxicity was observed in a patient in the once daily dosing group (2.5% vs 0%, respectively, p=0.48). CONCLUSIONS: No significant difference in the development of nephrotoxicity was found between the two dosing regimens for aminoglycosides, but this finding had low statistical power. This may be due to underdosing of aminoglycosides in the multiple daily dosing group.
Acute Kidney Injury ; Adult ; Aminoglycosides* ; Drug Administration Schedule ; Humans ; Quality Improvement