16 results on '"Dickson AR"'
Search Results
2. Evaluation of three protocols for direct susceptibility testing for gram negative-Enterobacteriaceae from patient samples in Uganda with SMS reporting
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Dickson Aruhomukama, Walusimbi Talemwa Magiidu, George Katende, Robert Innocent Ebwongu, Douglas Bulafu, Rajab Kasolo, Hellen Nakabuye, David Musoke, and Benon Asiimwe
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Medicine ,Science - Abstract
Abstract In Uganda, the challenge of generating and timely reporting essential antimicrobial resistance (AMR) data has led to overreliance on empirical antibiotic therapy, exacerbating the AMR crisis. To address this issue, this study aimed to adapt a one-step AMR testing protocol alongside an SMS (Short Message Service) result relay system (SRRS), with the potential to reduce the turnaround time for AMR testing and result communication from 4 days or more to 1 day in Ugandan clinical microbiology laboratories. Out of the 377 samples examined, 54 isolates were obtained. Notably, E. coli (61%) and K. pneumoniae (33%) were the most frequently identified, majority testing positive for ESBL. Evaluation of three AMR testing protocols revealed varying sensitivity and specificity, with Protocol A (ChromID ESBL-based) demonstrating high sensitivity (100%) but no calculable specificity, Protocol B (ceftazidime-based) showing high sensitivity (100%) and relatively low specificity (7.1%), and Protocol C (cefotaxime-based) exhibiting high sensitivity (97.8%) but no calculable specificity. ESBL positivity strongly correlated with resistance to specific antibiotics, including cefotaxime, ampicillin, and aztreonam (100%), cefuroxime (96%), ceftriaxone (93%), and trimethoprim sulfamethoxazole (87%). The potential of integrating an SRRS underscored the crucial role this could have in enabling efficient healthcare communication in AMR management. This study underscores the substantial potential of the tested protocols for accurately detecting ESBL production in clinical samples, potentially, providing a critical foundation for predicting and reporting AMR patterns. Although considerations related to specificity warrant careful assessment before widespread clinical adoption.
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- 2024
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3. Investigating the evolution and predicting the future outlook of antimicrobial resistance in sub-saharan Africa using phenotypic data for Klebsiella pneumoniae: a 12-year analysis
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Dickson Aruhomukama and Hellen Nakabuye
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Antimicrobial resistance ,Evolution ,Future outlook ,Africa ,Microbiology ,QR1-502 - Abstract
Abstract Background Antimicrobial resistance (AMR) is a major public health challenge, particularly in sub-Saharan Africa (SSA). This study aimed to investigate the evolution and predict the future outlook of AMR in SSA over a 12-year period. By analysing the trends and patterns of AMR, the study sought to enhance our understanding of this pressing issue in the region and provide valuable insights for effective interventions and control measures to mitigate the impact of AMR on public health in SSA. Results The study found that general medicine patients had the highest proportion of samples with AMR. Different types of samples showed varying levels of AMR. Across the studied locations, the highest resistance was consistently observed against ceftaroline (ranging from 68 to 84%), while the lowest resistance was consistently observed against ceftazidime avibactam, imipenem, meropenem, and meropenem vaborbactam (ranging from 92 to 93%). Notably, the predictive analysis showed a significant increasing trend in resistance to amoxicillin-clavulanate, cefepime, ceftazidime, ceftaroline, imipenem, meropenem, piperacillin-tazobactam, and aztreonam over time. Conclusions These findings suggest the need for coordinated efforts and interventions to control and prevent the spread of AMR in SSA. Targeted surveillance based on local resistance patterns, sample types, and patient populations is crucial for effective monitoring and control of AMR. The study also highlights the urgent need for action, including judicious use of antibiotics and the development of alternative treatment options to combat the growing problem of AMR in SSA.
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- 2023
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4. Medically important bacteria isolated from commercial herbal medicines in Kampala city indicate the need to enhance safety frameworks
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Abdul Walusansa, Jesca. L. Nakavuma, Savina Asiimwe, Jamilu. E. Ssenku, Dickson Aruhomukama, Tahalu Sekulima, Hussein. M. Kafeero, Godwin Anywar, Esther Katuura, Alice Nabatanzi, Nathan. L. Musisi, Arthur. K. Tugume, and Esezah. K. Kakudidi
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Medicine ,Science - Abstract
Abstract The high global bacterial infection burden has created need to investigate the neglected potential drivers of pathogenic bacteria, to inform disease prevention. Kampala is facing a proliferation of herbalists, selling herbal medicine (HM), of largely unregulated microbiological quality. We evaluated the bacterial contamination burden in HM sold in Kampala, to support evidence-based redress. The total viable loads (TVL), total coliform counts (TCC), E. coli counts, and prevalence of selected bacterial strains in 140 HM were examined using conventional culture, following the guidelines of World Health Organization (WHO), and Uganda National Drug Authority (NDA). Data were analyzed using D'Agostino-Pearson test, frequencies, proportions, Chi-square, and Mann–Whitney U test with STATA version-15.0. Fifty (35.7%), fifty-nine (42.1%), and twelve (8.6%) HM were unsafe for human use because they exceeded WHO’s permissible limits for TVL, TCC, and E. coli counts respectively. Solids had significantly higher mean TVL than liquids. Violation of NDA’s guidelines was significantly associated with high TVL. Fifty-nine bacteria, viz., Klebsiella pneumoniae (n = 34; 57.6%), Escherichia. coli (12; 20.3%), Staphylococcus aureus (7; 11.9%), Klebsiella oxytoca (3; 5.1%), Bacillus cereus, Pseudomonas aeruginosa, and Enterobacter spp. (1; 1.7% each), were isolated from 45 (32.1%) samples. These bacteria can cause severe clinical diseases, and promote deterioration of HM potency.
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- 2022
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5. The need to improve antimicrobial susceptibility testing capacity in Ugandan health facilities: insights from a surveillance primer
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Duku Chaplain, Butti Ben Asutaku, Muhammad Mona, Douglas Bulafu, and Dickson Aruhomukama
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Antimicrobial resistance ,Surveillance ,Microbiology labs ,Mulago Hospital ,Uganda ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Lab-based surveillance (LBS) of antimicrobial resistance (AMR) is not systematically implemented in Uganda. We aimed to identify the gaps in establishing regular LBS of AMR in Uganda. Methods This was a retrospective records review. It was done at Mulago Hospital (MH) Microbiology Lab (MHL). It analyzed lab records on bacteria and their antimicrobial susceptibility profiles (ASPs) over 6 months. Since MH is the national referral hospital, we hypothesized that (1) MHL is the best resourced and that any limitations seen here are amplified in labs at regional referral hospitals (RRHs) and health centers (HCs); (2) data from MHL on LBS mirrors that from labs at RRHs and HCs; (3) the state of records from MHL show lab performance and the presence or absence of standard operating procedures (SOPs), as would be the case at RRHs and HCs. Results The lab got 1760 samples over the six months. The most common sample was urine (659, 37.4%). From the 1760 samples, data on 478 bacterial isolates were available. Urine gave the most isolates (159, 33.3%). Most of the isolates were gram-negative (267, 55.9%). Escherichia coli (100, 37%) was the most common gram-negative (of the Enterobacteriaceae). Pseudomonas aeruginosa (17, 6%) was the most common gram-negative (of the non-Enterobacteriaceae). The gram-negative bacteria were highly resistant to β-lactams. These were highly sensitive to carbapenems. The Staphylococcus aureus were highly resistant to β-lactams. The gram-positive bacteria were highly sensitive to vancomycin. ASPs for all bacterial categories were incomplete. Conclusions The findings from MHL suggest that there is a need to improve antimicrobial susceptibility testing capacity. They also suggest that the situation at RRHs and HCs around the country could be worse. So, there is a need to extend the political will, which already exists, into operational and implementation action.
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- 2022
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6. Antibiotic-resistance in medically important bacteria isolated from commercial herbal medicines in Africa from 2000 to 2021: a systematic review and meta-analysis
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Abdul Walusansa, Savina Asiimwe, Jesca. L. Nakavuma, Jamilu. E. Ssenku, Esther Katuura, Hussein. M. Kafeero, Dickson Aruhomukama, Alice Nabatanzi, Godwin Anywar, Arthur K. Tugume, and Esezah K. Kakudidi
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Africa ,Antimicrobial resistance ,Bacterial contamination ,Herbal medicine ,Meta-analysis ,Systematic review ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Antimicrobial resistance is swiftly increasing all over the world. In Africa, it manifests more in pathogenic bacteria in form of antibiotic resistance (ABR). On this continent, bacterial contamination of commonly used herbal medicine (HM) is on the increase, but information about antimicrobial resistance in these contaminants is limited due to fragmented studies. Here, we analyzed research that characterized ABR in pathogenic bacteria isolated from HM in Africa since 2000; to generate a comprehensive understanding of the drug-resistant bacterial contamination burden in this region. Methods The study was conducted according to standards of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). We searched for articles from 12 databases. These were: PubMed, Science Direct, Scifinder scholar, Google scholar, HerbMed, Medline, EMBASE, Cochrane Library, International Pharmaceutical Abstracts, Commonwealth Agricultural Bureau Abstracts, African Journal Online, and Biological Abstracts. Prevalence and ABR traits of bacterial isolates, Cochran’s Q test, and the I2 statistic for heterogeneity were evaluated using MedCalcs software. A random-effects model was used to determine the pooled prevalence of ABR traits. The potential sources of heterogeneity were examined through sensitivity analysis, subgroup analysis, and meta-regression at a 95% level of significance. Findings Eighteen studies met our inclusion criteria. The pooled prevalence of bacterial resistance to at least one conventional drug was 86.51% (95% CI = 61.247–99.357%). The studies were highly heterogeneous (I 2 = 99.17%; p
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- 2022
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7. Source-tracking ESBL-producing bacteria at the maternity ward of Mulago hospital, Uganda
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Richard Mayanja, Adrian Muwonge, Dickson Aruhomukama, Fred Ashaba Katabazi, Mudarshiru Bbuye, Edgar Kigozi, Annettee Nakimuli, Musa Sekikubo, Christine Florence Najjuka, and David Patrick Kateete
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Medicine ,Science - Abstract
Introduction Escherichia coli, Klebsiella pneumoniae and Enterobacter (EKE) are the leading cause of mortality and morbidity in neonates in Africa. The management of EKE infections remains challenging given the global emergence of carbapenem resistance in Gram-negative bacteria. This study aimed to investigate the source of EKE organisms for neonates in the maternity environment of a national referral hospital in Uganda, by examining the phenotypic and molecular characteristics of isolates from mothers, neonates, and maternity ward. Methods From August 2015 to August 2016, we conducted a cross-sectional study of pregnant women admitted for elective surgical delivery at Mulago hospital in Kampala, Uganda; we sampled (nose, armpit, groin) 137 pregnant women and their newborns (n = 137), as well as health workers (n = 67) and inanimate objects (n = 70 –beds, ventilator tubes, sinks, toilets, door-handles) in the maternity ward. Samples (swabs) were cultured for growth of EKE bacteria and isolates phenotypically/molecularly investigated for antibiotic sensitivity, as well as β-lactamase and carbapenemase activity. To infer relationships among the EKE isolates, spatial cluster analysis of phenotypic and genotypic susceptibility characteristics was done using the Ridom server. Results Gram-negative bacteria were isolated from 21 mothers (15%), 15 neonates (11%), 2 health workers (3%), and 13 inanimate objects (19%); a total of 131 Gram-negative isolates were identified of which 104 were EKE bacteria i.e., 23 (22%) E. coli, 50 (48%) K. pneumoniae, and 31 (30%) Enterobacter. Carbapenems were the most effective antibiotics as 89% (93/104) of the isolates were susceptible to meropenem; however, multidrug resistance was prevalent i.e., 61% (63/104). Furthermore, carbapenemase production and carbapenemase gene prevalence were low; 10% (10/104) and 6% (6/104), respectively. Extended spectrum β-lactamase (ESBL) production occurred in 37 (36%) isolates though 61 (59%) carried ESBL-encoding genes, mainly blaCTX-M (93%, 57/61) implying that blaCTX-M is the ideal gene for tracking ESBL-mediated resistance at Mulago. Additionally, spatial cluster analysis revealed isolates from mothers, new-borns, health workers, and environment with similar phenotypic/genotypic characteristics, suggesting transmission of multidrug-resistant EKE to new-borns. Conclusion Our study shows evidence of transmission of drug resistant EKE bacteria in the maternity ward of Mulago hospital, and the dynamics in the ward are more likely to be responsible for transmission but not individual mother characteristics. The high prevalence of drug resistance genes highlights the need for more effective infection prevention/control measures and antimicrobial stewardship programs to reduce spread of drug-resistant bacteria in the hospital, and improve patient outcomes.
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- 2023
8. Isoniazid preventive therapy completion and factors associated with non-completion among patients on antiretroviral therapy at Kisenyi Health Centre IV, Kampala, Uganda.
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Ian Amanya, Michael Muhoozi, Dickson Aruhomukama, Anthony Ssebagereka, and Richard Mugambe
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Medicine ,Science - Abstract
BackgroundIsoniazid preventive therapy (IPT) is given to HIV patients to reduce the risk of active tuberculosis (TB). However, treatment completion remains suboptimal among those that are initiated. This study aimed to determine the completion level of IPT and the factors associated with non-completion among patients on antiretroviral therapy (ART) at Kisenyi Health Center IV in Kampala, Uganda.MethodsA mixed-methods facility-based retrospective cohort study utilizing routinely collected data from 341 randomly selected HIV patients initiated on IPT was conducted. Data extracted from the registers was used to determine IPT completion. Robust Poisson regression was conducted to determine the associated factors of IPT non-completion, while in-depth interviews were conducted to explore barriers to IPT completion from the patient's perspective.ResultsA total of 341 patients who started on isoniazid (INH) were retrospectively followed up, with 69% (236/341) being female. Overall IPT completion was 83%. Multivariate analysis revealed the prevalence of IPT non-completion among males was 2.24 times the prevalence among females (aPR 2.24, 95% CI: 1.40-3.58, p = 0.001). The prevalence of IPT non-completion among patients with a non-suppressed HIV viral load was 3.00 times the prevalence among those with a suppressed HIV viral load (aPR 3.00, 95% CI: 1.44-6.65, p = 0.007). The prevalence of IPT non-completion among patients who were married, or cohabiting was 0.31 times the prevalence among those who were single (aPR 0.31, 95% CI: 0.17-0.55, pConclusionIPT completion was found to be 83% among the cohort studied. However, lower completion levels persist among males and HIV-virally non-suppressed patients. Lack of IPT-related health education, pill burden, distance to the health facility, and patient relocation were reported as barriers to IPT completion. Interventions that target these groups of people need to be intensified.
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- 2023
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9. Adherence to malaria treatment guidelines among health care workers in private health facilities in Kampala’s informal settlements, Uganda
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Douglas Bulafu, Bridget Nagawa Tamale, Lesley Rose Ninsiima, James Natweta Baguma, Lydia Nabawanuka Namakula, Filimin Niyongabo, Grace Biyinzika Lubega, Dickson Aruhomukama, Rawlance Ndejjo, and David Musoke
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Public aspects of medicine ,RA1-1270 - Abstract
Poor adherence to malaria treatment guidelines among healthcare workers (HCWs) is a major contribution to diagnostic challenges, treatment failure, and non-rational use of antimalarial medicines. However, there is limited information about adherence to malaria treatment guidelines among HCWs in private health facilities in informal settlements in Uganda. This study therefore assessed the level of adherence to malaria treatment guidelines and associated factors among HCWs in private health facilities in Kampala’s informal settlements. A cross-sectional study was conducted among 339 HCWs from private health facilities in slums of 4 selected divisions in Kampala, Uganda. Quantitative data was collected using a semi-structured questionnaire, cleaned in MS Excel 2016 and analyzed using STATA 15.0 statistical software. Bivariate and multivariate analysis were conducted using a generalized linear model of modified Poisson regression to obtain factors associated with adherence to malaria treatment guidelines. The study revealed that majority of respondents 71.1%(241/339) were aged 30 years and below, and 50.1%(170/339) of the were female. Almost all of the respondents 98.8%(335/339) reported that they had malaria diagnostic equipment (microscopy or rapid diagnostic tests) at their facilities, 47.5%(161/339) had non-recommended anti-malarial drugs present in stock and 36.0% reported that they did not refer severely ill patients to higher health facilities in the previous 3 months. Although 92.6%(314/339) of the respondents had heard about the national malaria treatment guidelines, 63.1%(214/339) of them adhered to these guidelines. Having a bachelors degree (APR 1.54, (CI: 1.13–2.10)P 0.006), and having high levels of knowledge (APR 1.44, (CI: 1.13–1.60)P 0.001) were positively associated with high adherence to malaria treatment guidelines. In conclusion, adherence to malaria treatment guidelines was suboptimal and less than the national target of 90%. Enforcement, supervision, trainings, and continuous medical education should be enhanced in private healthcare facilities to improve adherence to malaria treatment guidelines in informal settlements.
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- 2023
10. bla VIM- and bla OXA-mediated carbapenem resistance among Acinetobacter baumannii and Pseudomonas aeruginosa isolates from the Mulago hospital intensive care unit in Kampala, Uganda
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Dickson Aruhomukama, Christine F. Najjuka, Henry Kajumbula, Moses Okee, Gerald Mboowa, Ivan Sserwadda, Richard Mayanja, Moses L. Joloba, and David P. Kateete
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Carbapenem resistant Acinetobacter ,Carbapenem resistant Pseudomonas aeruginosa ,Carbapenemase genes ,Class 1 integrons ,Conjugation ,Intensive care unit ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Between January 2015 and July 2017, we investigated the frequency of carbapenem resistant Acinetobacter baumannii (CRAB) and carbapenem resistant Pseudomonas aeruginosa (CRPA) at the Mulago Hospital intensive care unit (ICU) in Kampala, Uganda. Carbapenemase production and carbapenemase gene carriage among CRAB and CRPA were determined; mobility potential of carbapenemase genes via horizontal gene transfer processes was also studied. Methods Clinical specimens from 9269 patients were processed for isolation of CRAB and CRPA. Drug susceptibility testing was performed with the disk diffusion method. Carriage of carbapenemase genes and class 1 integrons was determined by PCR. Conjugation experiments that involved bla VIM positive CRAB/CRPA (donors) and sodium azide resistant Escherichia coli J53 (recipient) were performed. Results The 9269 specimens processed yielded 1077 and 488 isolates of Acinetobacter baumannii and Pseudomonas aeruginosa, respectively. Of these, 2.7% (29/1077) and 7.4% (36/488) were confirmed to be CRAB and CRPA respectively, but 46 were available for analysis (21 CRAB and 25 CRPA). Majority of specimens yielding CRAB and CRPA were from the ICU (78%) while 20 and 2% were from the ENT (Ear Nose & Throat) Department and the Burns Unit, respectively. Carbapenemase assays performed with the MHT assay showed that 40 and 33% of CRPA and CRAB isolates respectively, were carbapenemase producers. Also, 72 and 48% of CRPA and CRAB isolates respectively, were metallo-beta-lactamase producers. All the carbapenemase producing isolates were multidrug resistant but susceptible to colistin. bla VIM was the most prevalent carbapenemase gene, and it was detected in all CRAB and CRPA isolates while bla OXA-23 and bla OXA-24 were detected in 29 and 24% of CRAB isolates, respectively. Co-carriage of bla OXA-23 and bla OXA-24 occurred in 14% of CRAB isolates. Moreover, 63% of the study isolates carried class 1 integrons; of these 31% successfully transferred bla VIM to E. coli J53. Conclusions CRAB and CRPA prevalence at the Mulago Hospital ICU is relatively low but carbapenemase genes especially bla VIM and bla OXA-23 are prevalent among them. This requires strengthening of infection control practices to curb selection and transmission of these strains in the hospital.
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- 2019
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11. Investigating colistin drug resistance: The role of high-throughput sequencing and bioinformatics [version 2; peer review: 2 approved]
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Dickson Aruhomukama, Ivan Sserwadda, and Gerald Mboowa
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Medicine ,Science - Abstract
Bacterial infections involving antibiotic-resistant gram-negative bacteria continue to increase and represent a major global public health concern. Resistance to antibiotics in these bacteria is mediated by chromosomal and/or acquired resistance mechanisms, these give rise to multi-drug resistant (MDR), extensive-drug resistant (XDR) or pan-drug resistant (PDR) bacterial strains. Most recently, plasmid-mediated resistance to colistin, an antibiotic that had been set apart as the last resort antibiotic in the treatment of infections involving MDR, XDR and PDR gram-negative bacteria has been reported. Plasmid-mediated colistin resistant gram-negative bacteria have been described to be PDR, implying a state devoid of alternative antibiotic therapeutic options. This review concisely describes the evolution of antibiotic resistance to plasmid-mediated colistin resistance and discusses the potential role of high-throughput sequencing technologies, genomics, and bioinformatics towards improving antibiotic resistance surveillance, the search for novel drug targets and precision antibiotic therapy focused at combating colistin resistance, and antibiotic resistance as a whole.
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- 2019
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12. Increasing Antimicrobial Resistance in Surgical Wards at Mulago National Referral Hospital, Uganda, from 2014 to 2018—Cause for Concern?
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Gerald Mboowa, Dickson Aruhomukama, Ivan Sserwadda, Freddy Eric Kitutu, Hayk Davtyan, Philip Owiti, Edward Mberu Kamau, Wendemagegn Enbiale, Anthony Reid, Douglas Bulafu, Jeffrey Kisukye, Margaret Lubwama, and Henry Kajumbula
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antimicrobial resistance (AMR) ,trends ,Structured Operational Research and Training IniTiative (SORT IT) ,surgical wards ,Mulago National Referral Hospital (MNRH) ,Uganda ,Medicine - Abstract
Antimicrobial Resistance (AMR) and Healthcare Associated Infections (HAIs) are major global public health challenges in our time. This study provides a broader and updated overview of AMR trends in surgical wards of Mulago National Referral Hospital (MNRH) between 2014 and 2018. Laboratory data on the antimicrobial susceptibility profiles of bacterial isolates from 428 patient samples were available. The most common samples were as follows: tracheal aspirates (36.5%), pus swabs (28.0%), and blood (20.6%). Klebsiella (21.7%), Acinetobacter (17.5%), and Staphylococcus species (12.4%) were the most common isolates. The resistance patterns for different antimicrobials were: penicillins (40–100%), cephalosporins (30–100%), β-lactamase inhibitor combinations (70–100%), carbapenems (10–100%), polymyxin E (0–7%), aminoglycosides (50–100%), sulphonamides (80–100%), fluoroquinolones (40–70%), macrolides (40–100%), lincosamides (10–45%), phenicols (40–70%), nitrofurans (0–25%), and glycopeptide (0–20%). This study demonstrated a sustained increase in resistance among the most commonly used antibiotics in Uganda over the five-year study period. It implies ongoing hospital-based monitoring and surveillance of AMR patterns are needed to inform antibiotic prescribing, and to contribute to national and global AMR profiles. It also suggests continued emphasis on infection prevention and control practices (IPC), including antibiotic stewardship. Ultimately, laboratory capacity for timely bacteriological culture and sensitivity testing will provide a rational choice of antibiotics for HAI.
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- 2021
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13. Membrane biophysics define neuron and astrocyte progenitors in the neural lineage.
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Nourse JL, Prieto JL, Dickson AR, Lu J, Pathak MM, Tombola F, Demetriou M, Lee AP, and Flanagan LA
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- Animals, Cell Separation, Cell Size, Electrophysiological Phenomena, Glycosylation, Membrane Potentials, Mice, Microfluidics, Astrocytes cytology, Biophysical Phenomena, Cell Lineage, Cell Membrane physiology, Neural Stem Cells cytology, Neurons cytology
- Abstract
Neural stem and progenitor cells (NSPCs) are heterogeneous populations of self-renewing stem cells and more committed progenitors that differentiate into neurons, astrocytes, and oligodendrocytes. Accurately identifying and characterizing the different progenitor cells in this lineage has continued to be a challenge for the field. We found previously that populations of NSPCs with more neurogenic progenitors (NPs) can be distinguished from those with more astrogenic progenitors (APs) by their inherent biophysical properties, specifically the electrophysiological property of whole cell membrane capacitance, which we characterized with dielectrophoresis (DEP). Here, we hypothesize that inherent electrophysiological properties are sufficient to define NPs and APs and test this by determining whether isolation of cells solely by these properties specifically separates NPs and APs. We found NPs and APs are enriched in distinct fractions after separation by electrophysiological properties using DEP. A single round of DEP isolation provided greater NP enrichment than sorting with PSA-NCAM, which is considered an NP marker. Additionally, cell surface N-linked glycosylation was found to significantly affect cell fate-specific electrophysiological properties, providing a molecular basis for the cell membrane characteristics. Inherent plasma membrane biophysical properties are thus sufficient to define progenitor cells of differing fate potential in the neural lineage, can be used to specifically isolate these cells, and are linked to patterns of glycosylation on the cell surface., (© AlphaMed Press.)
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- 2014
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14. Advancing practical usage of microtechnology: a study of the functional consequences of dielectrophoresis on neural stem cells.
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Lu J, Barrios CA, Dickson AR, Nourse JL, Lee AP, and Flanagan LA
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- Animals, Astrocytes cytology, Cell Line, Cell Lineage, Cell Proliferation, Cell Survival, Cells, Cultured, Cerebral Cortex cytology, DNA metabolism, Electrophysiology methods, Equipment Design, Gestational Age, Humans, Kinetics, Membrane Potentials, Mice, Microtechnology, Models, Statistical, Stem Cells cytology, Time Factors, Electrophoresis methods, Neural Stem Cells cytology
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The integration of microscale engineering, microfluidics, and AC electrokinetics such as dielectrophoresis has generated novel microsystems that enable quantitative analysis of cellular phenotype, function, and physiology. These systems are increasingly being used to assess diverse cell types, such as stem cells, so it becomes critical to thoroughly evaluate whether the systems themselves impact cell function. For example, engineered microsystems have been utilized to investigate neural stem/progenitor cells (NSPCs), which are of interest due to their potential to treat CNS disease and injury. Analysis by dielectrophoresis (DEP) microsystems determined that unlabeled NSPCs with distinct fate potential have previously unrecognized distinguishing electrophysiological characteristics, suggesting that NSPCs could be isolated by DEP microsystems without the use of cell type specific labels. To gauge the potential impact of DEP sorting on NSPCs, we investigated whether electric field exposure of varying times affected survival, proliferation, or fate potential of NSPCs in suspension. We found short-term DEP exposure (1 min or less) had no effect on NSPC survival, proliferation, or fate potential revealed by differentiation. Moreover, NSPC proliferation (measured by DNA synthesis and cell cycle kinetics) and fate potential were not altered by any length of DEP exposure (up to 30 min). However, lengthy exposure (>5 min) to frequencies near the crossover frequency (50-100 kHz) led to decreased survival of NSPCs (maximum ∼30% cell loss after 30 min). Based on experimental observations and mathematical simulations of cells in suspension, we find that frequencies near the crossover frequency generate an induced transmembrane potential that results in cell swelling and rupture. This is in contrast to the case for adherent cells since negative DEP frequencies lower than the crossover frequency generate the highest induced transmembrane potential and damage for these cells. We clarify contrasting effects of DEP on adherent and suspended cells, which are related to the cell position within the electric field and the strength of the electric field at specific distances from the electrodes. Modeling of electrode configurations predicts optimal designs to induce cell movement by DEP while limiting the induced transmembrane potential. We find DEP electric fields are not harmful to stem cells in suspension at short exposure times, thus providing a basis for developing DEP-based applications for stem cells.
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- 2012
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15. Salmon fibrin treatment of spinal cord injury promotes functional recovery and density of serotonergic innervation.
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Sharp KG, Dickson AR, Marchenko SA, Yee KM, Emery PN, Laidmåe I, Uibo R, Sawyer ES, Steward O, and Flanagan LA
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- Animals, Axons drug effects, Axons physiology, Female, Fibrin administration & dosage, Motor Activity drug effects, Motor Activity physiology, Nerve Regeneration drug effects, Nerve Regeneration physiology, Rats, Rats, Sprague-Dawley, Recovery of Function physiology, Serotonergic Neurons physiology, Spinal Cord physiopathology, Spinal Cord Injuries physiopathology, Tissue Scaffolds, Fibrin therapeutic use, Recovery of Function drug effects, Serotonergic Neurons drug effects, Spinal Cord drug effects, Spinal Cord Injuries drug therapy
- Abstract
The neural degeneration caused by spinal cord injury leaves a cavity at the injury site that greatly inhibits repair. One approach to promoting repair is to fill the cavity with a scaffold to limit further damage and encourage regrowth. Injectable materials are advantageous scaffolds because they can be placed as a liquid in the lesion site then form a solid in vivo that precisely matches the contours of the lesion. Fibrin is one type of injectable scaffold, but risk of infection from blood borne pathogens has limited its use. We investigated the potential utility of salmon fibrin as an injectable scaffold to treat spinal cord injury since it lacks mammalian infectious agents and encourages greater neuronal extension in vitro than mammalian fibrin or Matrigel®, another injectable material. Female rats received a T9 dorsal hemisection injury and were treated with either salmon or human fibrin at the time of injury while a third group served as untreated controls. Locomotor function was assessed using the BBB scale, bladder function was analyzed by measuring residual urine, and sensory responses were tested by mechanical stimulation (von Frey hairs). Histological analyses quantified the glial scar, lesion volume, and serotonergic fiber density. Rats that received salmon fibrin exhibited significantly improved recovery of both locomotor and bladder function and a greater density of serotonergic innervation caudal to the lesion site without exacerbation of pain. Rats treated with salmon fibrin also exhibited less autophagia than those treated with human fibrin, potentially pointing to amelioration of sensory dysfunction. Glial scar formation and lesion size did not differ significantly among groups. The pattern and timing of salmon fibrin's effects suggest that it acts on neuronal populations but not by stimulating long tract regeneration. Salmon fibrin clearly has properties distinct from those of mammalian fibrin and is a beneficial injectable scaffold for treatment of spinal cord injury., (Copyright © 2012 Elsevier Inc. All rights reserved.)
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- 2012
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16. THE INTERNAL RING IN OBLIQUE INGUINAL HERNIA.
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Dickson AR
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- 1931
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