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result(s) for
"A. Brahma"
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Twelve-year analysis of microbial keratitis trends at a UK tertiary hospital
by
Fullwood, C
,
Carley, F
,
Brahma, A K
in
692/308/174
,
692/699/3161
,
Acanthamoeba - isolation & purification
2017
Purpose
To investigate the frequencies, trends, and
in vitro
drug susceptibilities of the causative pathogens in microbial keratitis in Manchester Royal Eye Hospital.
Patients and methods
Corneal scrape results recorded by the microbiology service between 2004 and 2015 were extracted from an established database. A total of 4229 corneal scrape specimens were identified from an established database. First-line antibiotic treatment in our centre during the study period was ofloxacin and second line was cefuroxime and gentamicin.
Results
Mean age was 45.9±21.0. A total of 1379 samples (32.6%) were culture positive. One hundred forty-eight (10.7%) specimens cultured multiple organisms. Of the 1539 organisms identified, 63.3% were Gram-positive bacteria, 27.3% Gram-negative bacteria, 7.1% fungi, and 2.3%
Acanthamoebae
. A decreasing trend in Gram-positive isolates was found together with a stable trend in Gram negatives and an increasing trend in
Acanthamoeba
and fungi. There appeared to be a significant increasing trend of
Moraxella
infection (
P
=0.001). In all, 83.1 and 90.8% of Gram-positive and -negative isolates tested were susceptible to ofloxacin, respectively. Cefuroxime covered 86.6% of Gram-positive and 61.4% of Gram-negative isolates, whereas gentamicin covered 88.8 and 96.5% of Gram-positive and -negative isolates, respectively.
Conclusion
We found a change in the type of Gram-negative organisms isolated over time, with the
Moraxella
species on the rise. Reassuringly, no significant increase in resistance was observed
in vitro
for any of the commonly used antibiotics. Ofloxacin remains a good first-line antibiotic treatment but duo-therapy does have broader coverage and should be considered in non-responsive cases.
Journal Article
To leave or to stay: direct fitness through natural nest foundation in a primitively eusocial wasp
2019
Dispersing from the natal nest to found new nests is an avenue for gaining direct fitness for workers in some primitively eusocial insects, especially in species with a perennial nesting cycle where males are present throughout the year. Such nest foundation is difficult to study in nature or in small laboratory cages. Hence, we have investigated the dynamics of nest foundation by workers of the primitively eusocial wasp
Ropalidia marginata
inside closed walk-in cages so that we could locate and observe every event of nest foundation. Starting with nine parent nests we observed the dispersal of female workers that initiated 9 single-foundress and 20 multiple-foundress nests. Wasps congregated outside their parent nests and engaged in dominance–subordinate interactions before initiating multiple foundress nests. The most dominant wasps of such aggregations became queens, and among the others, some joined the new nests as cofoundresses to become workers while the others remained in the parent nests. Solitary foundresses never participated in such off-nest aggregations. Solitary foundresses and future queens of multiple foundress nests engaged in self-feeding behaviour outside their parent nests, a behaviour not performed by wasps that did not initiate new nests. Queens of new nests gained immediate direct fitness. Although the cofoundresses continued to gain only indirect fitness, they are expected to have a higher probability of gaining direct fitness in the future as compared to the corresponding probability in their much larger parent nests. These findings underscore the importance of direct fitness in the evolution of cooperation in primitively eusocial insects.
Journal Article
Nutrition induced direct fitness for workers in a primitively eusocial wasp
2021
Eusocial insects are characterised by a reproductive caste differentiation such that egg-laying is restricted to a small number of queens. The majority of the colony members function as non-reproducing workers and gain indirect fitness by rearing the offspring of the reproductives. In primitively eusocial species, some workers can also get direct fitness by sneaking in some eggs in the presence of the queens, replacing the queens and becoming new queens, or initiating new nests. Here we aimed to understand the factors that permit some workers to gain direct fitness and alter the number of workers doing so, using the primitively eusocial wasp
Ropalidia marginata
. We transplanted 12 naturally occurring colonies into large laboratory cages where there was adequate space for the workers to leave their natal nests and initiate new colonies. We compared six control colonies that we provided with ad libitum food placed near the nest to six test colonies in which we hand-fed the wasps in addition to the ad libitum food. Wasps in test colonies consumed more food, showed more aggression, replaced their queens, and initiated new nests significantly more often than those in control colonies. When considering all 12 colonies, the rates of queen replacement and nest foundation were significantly positively correlated with food consumption rates. The additional nutrition gained by hand-fed wasps appears to help workers in test colonies to develop their ovaries and lay eggs, implying that they are nutritionally castrated in control colonies.
Journal Article
Use of Margin to Absorb Variation in Design Specifications: An Analysis Using the Margin Value Method
by
Isaksson, O.
,
Brahma, A.
,
Wynn, D. C.
in
design margin
,
design optimisation
,
Design specifications
2022
Predicting the impact of changes in a design can be challenging, especially for complex designs. Margins are often built into the designs which can absorb the knock-on effect of such changes, erroneously allocating which can however, lead to propagation. A method for localising and sizing margins in an incremental design context is the Margin Value Method. This paper adapts MVM in the context of uncertainty in input specifications. It discusses possible ways to allocate them in a design such that undesirable effects of margins are minimised while preventing change propagation.
Journal Article
Non-spherical aluminum nanoparticles fabricated using picosecond laser ablation
by
Swamulu, A. Brahma
,
Podagatlapalli, G. Krishna
,
Rao, S. Venugopal
in
Ablation
,
Aluminum
,
Ceramics
2020
We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl
3
) with ∼2 ps laser pulses at an input energy of ∼350 µJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ∼340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ∼280 nm. Additionally, coarse structures with a period of ∼700 nm were observed.
Journal Article
Penetrating keratoplasty: indications, outcomes, and complications
2009
Purpose
Corneal transplantation is the most common form of transplantation with approximately 2500 grafts undertaken annually in the United Kingdom. The modern day success of transplantation is attributed to eye bank storage techniques, ocular pharmacology, and improved surgical techniques.
Methods
This retrospective case note review identified 203 penetrating keratoplasties (PKs) performed during a period from 1 January 2000 to 31 December 2003 at Manchester Royal Eye Hospital. Preoperative risk factors, surgical technique, postoperative complications, and Snellen acuity were analysed.
Results
The mean age of the recipient group was 56.7 years, with 107 right eyes and 96 left eyes. The mean follow-up was 61 months. The overall 5-year survival was 82%, with keratoconus and corneal dystrophies at 93 and 89%, respectively. Visual acuity had improved to 6/12 or better in 48% of patients postoperatively, compared with 8% preoperatively. Forty-three donor grafts (21%) underwent at least a single episode of endothelial rejection. Glaucoma was a finding in 37 (18%) of patients following PK. In all, 16 grafts of 15 patients were noted to have suffered microbial keratitis (MK), an incidence of 8%.
Conclusions
PK is currently an effective long-term treatment option for improving visual function. An overall survival rate of 82% over 5 years is comparable with other published studies and is largely dependent on recipient factors. This report emphasises the significant complications of immunological rejection, glaucoma, and microbial keratitis, which continue to limit success.
Journal Article
Floating drug delivery of nevirapine as a gastroretentive system
by
Brahma, Reddy
,
Samyuktha, Rani
,
Vedha Hari, B
in
Controlled release technology
,
Dosage and administration
,
Drug delivery systems
2010
A multiple-unit floating drug delivery system based on gas formation technique was developed, in order to prolong the gastric residence time and to increase the overall bioavailability of the dosage form. The floating bead formulations were prepared by dispersing nevirapine together with calcium carbonate in a mixture of sodium alginate and hydroxypropyl methylcellulose solution and then dripping the dispersion into an acidified solution of calcium chloride. Calcium alginate beads were formed, as the alginate underwent ionotropic gelation by calcium ions, and carbon dioxide developed from the reaction of carbonate salts with acid. The obtained beads were able to float due to CO 2 -gas formation and the gas entrapment by the polymeric membrane. The prepared beads were evaluated for percent drug loading, drug entrapment efficiency, morphology, surface topography, buoyancy, in-vitro release, and release kinetics. The formulations were optimized for different weight ratios of the gas-forming agent and sodium alginate. The beads containing higher amounts of calcium carbonate demonstrated an instantaneous, complete, and excellent floating ability over a period of 24 hours. The increased amount of the gas forming agent did not affect the time to float, but increased the drug release from the floating beads, while increasing the coating level of the gas-entrapped membrane, increased the time to float, and slightly retarded the drug release. Good floating properties and sustained drug release were achieved. Finally, these floating beads seemed to be a promising gastroretentive drug delivery system.
Journal Article
Impact of First Healthcare Provider on Acanthamoeba Keratitis Course: How to Overcome Poor Prognosis in Acanthamoeba Keratitis Treatment? A Single Tertiary Center, Observational Study
by
Brahma, Arun
,
Chidambaram, Jaya
,
Przybek-Skrzypecka, Joanna
in
Acanthamoeba
,
corneal ulcer
,
diagnosis
2023
To assess the difference in course and final visual outcome of
keratitis (AK) patients based on the first healthcare provider (HCP) seen.
Retrospective observational cohort study of AK patients admitted to the Manchester Royal Eye Hospital between 2003 and 2017. HCPs were grouped (Group 1: Optometrists, Opticians; Group 2: General Practitioners (GPs); Group 3: Ophthalmologists) and the data analyzed on demographics, risk factors, clinical history, clinical features, and
subspecies.
Forty-one patients with unilateral culture-proven AK were included. Median time to consultation with first HCP was 7 days (IQR 4-14 days), while mean time to the correct diagnosis of AK was 15 days (IQR 7-29 days). Patients saw an optician, optometrist or ophthalmologists significantly earlier than GPs (median 4 days, vs 15 or 5 days, respectively, p = 0.04). Bacterial keratitis was the most common initial clinical diagnosis (43%). The shortest time to making the AK diagnosis (median 11 days) and the highest rate of initiating AK treatment started at the first visit (38%) were both in the ophthalmologists' group. No significant differences were observed in initial and final visual acuity between HCP groups (p = 0.36).
AK patients often seek ocular help earlier from optometrists and opticians than medical doctors. Final clinical outcomes did not significantly differ based on the first HCP seen, but ophthalmologists were more likely to make the diagnosis of AK and initiate anti-amoebal therapy faster than other HCPs. Greater education and collaboration between ophthalmologists and other HCPs to increase awareness of AK are needed.
Journal Article