Three structurally-related impurities in norvancomycin drug substance

Looking Back to Amycolatopsis: History of the Antibiotic Discovery and Future Prospects

The emergence of antibiotic-resistant pathogenic bacteria in recent decades leads us to an urgent need for the development of new antibacterial agents. The species of the genus Amycolatopsis are known as producers of secondary metabolites that are used in medicine and agriculture. The complete genome sequences of the Amycolatopsis demonstrate a wide variety of biosynthetic gene clusters, which highlights the potential ability of actinomycetes of this genus to produce new antibiotics. In this review, we summarize information about antibiotics produced by Amycolatopsis species. This knowledge demonstrates the prospects for further study of this genus as an enormous source of antibiotics.

Determination of norvancomycin epidemiological cut-off values (ECOFFs) for Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus hominis

OBJECTIVES

To determine the epidemiological cut-off values (ECOFFs) of norvancomycin for Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus hominis.

METHODS

We collected 1199 clinical isolates of Staphylococcus species from five laboratories located in four cities in China. MICs and inhibitory zone diameters of norvancomycin were determined by broth microdilution and the disc diffusion method, separately. ECOFFs of norvancomycin for four species were calculated by ECOFFinder software following EUCAST principles. Methicillin and vancomycin resistance genes (mecA/mecC and vanA/vanB/vanC/vanD/vanE) were screened for by PCR in all isolates. Pearson correlation and χ2 test were used to calculate the correlation of MICs and inhibition zone diameters, and MICs and resistance genes, respectively.

RESULTS

MICs of norvancomycin for all strains from five laboratories fell in the range of 0.12-2 mg/L. ECOFFs of norvancomycin were determined to be 2 mg/L for S. epidermidis and S. haemolyticus and 1 mg/L for S. aureus and S. hominis. A weak correlation was observed between MIC values and zone diameters for S. haemolyticus (r = -0.36) and S. hominis (r = -0.26), while no correlation was found for S. epidermidis and S. aureus. The mecA gene was detected in 63.1% of Staphylococcus, whereas no isolate carried mecC, vanA, vanB, vanC, vanD or vanE. ECOFFs of norvancomycin were not correlated with mecA gene carriage in Staphylococcus species.

CONCLUSIONS

ECOFFs of norvancomycin for four Staphylococcus species were determined, which will be helpful to differentiate WT strains. The correlation of MICs and zone diameters of norvancomycin was weak in Staphylococcus species.

Treatment of Severe Acute Bacterial Keratitis in Rabbits Using Continuous Topical Ocular Instillation with Norvancomycin

Purpose

Efficacy of norvancomycin (NVCM) through continuous topical ocular instillation drug delivery (CTOIDD) system for treating severe acute bacterial keratitis infection with Staphylococcus aureus was investigated.

Methods

Rabbits with bacterial keratitis were treated using CTOIDD with NVCM (n=13), topical NVCM eye drops (n=11), and CTOIDD with saline (n=8). Clinical signs of keratitis in all groups were assessed consecutively for a week. Bacterial quantification of excised corneas was counted on the fourth and eighth days. Histopathologic examinations were performed to assess inflammatory cell infiltration on the eighth day.

Results

All signs of bacterial keratitis were alleviated in CTOIDD with NVCM according to criteria, and the CTOIDD-NVCM group had significantly less inflammation than CTOIDD-saline (p<0.05), and eye drop-NVCM (p<0.05). Two eyes in the eye drop-NVCM group, four eyes in the CTOIDD-saline group had corneal perforation (CP), while none of the rabbits showed CP in the CTOIDD-NVCM group. Bacterial counts were significantly less in the CTOIDD with NVCM group in comparison to the eye drop-NVCM (p<0.05), and CTOIDD-saline (p<0.05) groups. Severe inflammation and marked inflammatory cell infiltration were found in histopathologic examinations in the CTOIDD-saline and eye drop-NVCM groups, while significantly less inflammation was documented in the CTOIDD-NVCM (p<0.05) group.

Conclusion

CTOIDD with NVCM effectively reduced the severity and treated acute bacterial S. aureus keratitis infection in a rabbit model. The presented approach of CTOIDD with NVCM appears to be a promising therapeutic approach for severe acute bacterial keratitis.

Comparative Assessment of Distribution Characteristics and Ocular Pharmacokinetics of Norvancomycin Between Continuous Topical Ocular Instillation and Hourly Administration of Eye Drop

Background

The aim of this study was to compare the distribution characteristics and ocular pharmacokinetics of norvancomycin (NVCM) in ocular tissues of the anterior segment between continuous topical ocular instillation and hourly administration of eye drop in rabbits.

Methods

Sixty rabbits were randomly divided into two groups: continuous topical ocular instillation drug delivery (CTOIDD) group and eye drop (control) group. In the CTOIDD group, NVCM solution (50 mg/mL) was perfused to the ocular surface using the CTOIDD system at 2 mL/h up to 10 h and the same solution was administered at one drop (50 μL) per hour for 10 h in the control group. Animals (N=6 per time-point per group) were humanely killed at 2, 4, 6, 10, and 24 h to analyze their ocular tissues and plasma. The concentrations of NVCM in the conjunctiva, cornea, aqueous humour, iris, ciliary body and plasma were measured by HPLC with photodiode array detector. The pharmacokinetic parameters were calculated by Kinetica 5.1.

Results

The highest concentrations of NVCM for the CTOIDD group and control group were 2105.45±919.89 μg/g and 97.18±43.14 μg/g in cornea, 3033.92±1061.95 μg/g and 806.99±563.02 μg/g in conjunctiva, 1570.19±402.87 μg/g and 46.93±23.46 μg/g in iris, 181.94±47.11 μg/g and 15.38±4.00 μg/g in ciliary body, 29.78±4.90 μg/mL and 3.20±1.48 μg/mL in aqueous humour, and 26.89±5.57 μg/mL and 1.90±1.87 μg/mL in plasma, respectively. The mean NVCM levels significantly increased at all time-points in cornea, iris, and ciliary body (p<0.05) in the CTOIDD group. The AUC_0–24 values in the CTOIDD group were 27,543.70 μg·h/g in cornea, 32,514.48 μg·h/g in conjunctiva, 8631.05 μg·h/g in iris, 2194.36 μg·h/g in ciliary body and 343.9 μg·h/mL in aqueous humour, which were higher than for the eye drop group in all tissues.

Conclusion

Since continuous instillation of NVCM with CTOIDD could reach significantly higher concentrations and was sustained for a longer period compared with hourly administration of eye drop, CTOIDD administered NVCM could be a possible method to treat bacterial keratitis.

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Dolyemycins A and B, two novel cyclopeptides isolated from Streptomyces griseus subsp. griseus HYS31

Two novel cyclopeptides with special skeleton, namely, dolyemycins A (1) and B (2) were isolated from Streptomyces griseus subsp. griseus HYS31 by bio-guided isolation. Their structures were elucidated by detailed analysis of spectroscopic data. These two compounds were cyclopeptides containing eleven amino acids including five unusual amino acids (hydroxyglycine, 3-hydroxyleucine, 3-phenylserine, β-hydroxy-O-methyltyrosine, 2,3-diaminobutyric acid) in both of them and an extra nonprotein amino acids (3-methylaspartic acid) in Dolyemycin B only. Dolyemycins A and B performed antiproliferative activity against human lung cancer A549 cells with IC₅₀ values of 1.0 and 1.2 µM, respectively.