Predicting permeation of compounds across the outer membrane of P. aeruginosa using molecular descriptors

The ability Gram-negative pathogens have at adapting and protecting themselves against antibiotics has increasingly become a public health threat. Data-driven models identifying molecular properties that correlate with outer membrane (OM) permeation and growth inhibition while avoiding efflux could guide the discovery of novel classes of antibiotics. Here we evaluate 174 molecular descriptors in 1260 antimicrobial compounds and study their correlations with antibacterial activity in Gram-negative Pseudomonas aeruginosa. The descriptors are derived from traditional approaches quantifying the compounds' intrinsic physicochemical properties, together with, bacterium-specific from ensemble docking of compounds targeting specific MexB binding pockets, and all-atom molecular dynamics simulations in different subregions of the OM model. Using these descriptors and the measured inhibitory concentrations, we design a statistical protocol to identify predictors of OM permeation/inhibition. We find consistent rules across most of our data highlighting the role of the interaction between the compounds and the OM. An implementation of the rules uncovered in our study is shown, and it demonstrates the accuracy of our approach in a set of previously unseen compounds. Our analysis sheds new light on the key properties drug candidates need to effectively permeate/inhibit P. aeruginosa, and opens the gate to similar data-driven studies in other Gram-negative pathogens.

High rates of plasmid cotransformation in E. coli overturn the clonality myth and reveal colony development

The concept of DNA transfer between bacteria was put forth by Griffith in 1928. During the dawn of molecular cloning of DNA in the 1980s, Hanahan described how the transformation of DNA plasmids into bacteria would allow for cloning of DNA fragments. Through this foundational work, it is widely taught that a typical transformation produces clonal bacterial colonies. Using low concentrations of several plasmids that encode different fluorescent proteins, under the same selective antibiotic, we show that E. coli bacteria readily accept multiple plasmids, resulting in widespread aclonality and reveal a complex pattern of colony development. Cotransformation of plasmids occurs by either CaCl2 or by electroporation methods. A bacterium rod transformed with three plasmids-each expressing a high level of a unique fluorescent protein-and replated on agar, appears to reassign a random number of the three fluorescent plasmids to its daughter cell during cell division. The potential to simultaneously follow multiple lineages of clonally related bacteria in a bacteria colony would allow for mosaic analysis of gene function. We show that clonally related bacterium rods self-organize in a fractal growth pattern and can remain linked during colony development revealing a potential target against microbiota growth.

The effect of medical therapy on IOP control in Ghana

BACKGROUND

To investigate IOP control following twelve months of continuous medical therapy in Ghana.

METHODS

This retrospective case series included 163 glaucoma patients diagnosed at a referral eye center between 1996 and 2006. Information collected included age, gender, IOP at presentation, six months and one year post treatment and types of anti-glaucoma medications prescribed. Optimal IOP control was defined according to results from the Advanced Glaucoma Intervention Study (AGIS), which demonstrated arrest of visual field progression in patients with IOP < 18 mmHg at all visitations: Level 1 (post-treatment IOP ≤ 21 mmHg); Level 2 (≤ 18 mmHg) and level 3 (≤ 16 mmHg). The principal outcome measure was the achievement of IOP <18 mmHg at six months and twelve month visitations.

RESULTS

One hundred sixty three patients were analyzed. These included 68 males (41.7%) and 95 females (58.3%). The mean age was 57±16 (median 59 years; range 7 - 95 years). There was no significant difference in age (p=0.35) or mean IOP (p=0.08) between genders. The mean pre-treated IOP of 31.9±8.9 mmHg significantly decreased to 21.3±6.6 mmHg at 6 months (p=0.001), with 57.4% of eyes at Level 1 IOP control, 25.3% at Level 2 and 15.4% at Level 3 and decreased further at 12 months to 20.7±6.9 mmHg (p=0.48) with 69.7% of eyes at Level 1, 34.4% at Level 2, and 12.4% at Level 3.

CONCLUSIONS

Current medical regimen is insufficient to reduce IOP to target levels as defined in the Advanced Glaucoma Intervention Study.

Adult-onset primary open angle glaucoma does not localize to chromosome 2cen-q13 in North American families

Glaucoma is one of the leading causes of irreversible blindness in the world and is characterized by elevated intraocular pressure, optic nerve atrophy, and progressive visual field loss. Primary open angle glaucoma (POAG) is the most common subtype of glaucoma in the United States. Recently, Stoilova and coworkers [Genomics 1996;36:142-150] identified a locus for POAG on chromosome 2 (2cen-q13) in families primarily located in the United Kingdom. We examined families with POAG identified within the US for linkage to the 2cen-q13 locus. A total of 18 families with POAG were used in the analysis. Of 77 family members, 46 were classified as affected and 31 were either glaucoma suspects or considered normal. Eight highly polymorphic and informative markers flanking and distributed throughout the region were used. Parametric lod score analysis was performed using both a dominant and recessive low penetrance or 'affecteds-only' model. Multipoint affected sibpair exclusion mapping was also performed. Lod score (both models) and sibpair analysis excluded linkage of the POAG phenotype to the 2cen-q13 region in these families. These data suggest that the chromosome 2cen-q13 locus does not explain a substantial amount of genetic variation in familial POAG.

Retinal vein occlusion after trabeculectomy with mitomycin C

PURPOSE

To evaluate acute retinal vein occlusion as a potential complication of trabeculectomy with mitomycin C in cases of advanced glaucoma.

METHODS

The records of three patients who developed retinal vein occlusions immediately after uncomplicated trabeculectomy with mitomycin C were reviewed.

RESULTS

All three patients had advanced open-angle glaucoma with total cupping of the optic nerve, severe visual field loss, and evidence of systemic vascular disease. A marked decrease in intraocular pressure was noted in the postoperative period in all of the patients.

CONCLUSION

A shift in the lamina cribrosa, associated with the perioperative intraocular pressure change, may have contributed to occlusion of the venous outflow system in these susceptible patients.