Biology subjects

Brown, J. C. S.

Publications and source records attributed to Brown, J. C. S..

7 recordsLinked to original sources

bioRxiv2026

Synergistic Interaction Between Nitrofurantoin and Dequalinium Provides a Promising Approach to Treating UTIs caused by Antibiotic-Resistant Klebsiella pneumoniae

Nitrofurantoin is commonly prescribed as a first-line treatment for urinary tract infections (UTIs) and is effective against most uropathogens; however, resistance among Klebsiella spp. remains high. In this study, we investigated synergistic drug combinations--defined as pairs of drugs whose combined effect exceeds that of each agent alone--to enhance treatment efficacy against drug-resistant Klebsiella pneumoniae. A high-throughput drug screen identified six and two small molecules that exhibited >50% synergistic activity in tested strains in combination with nitrofurantoin and ciprofloxacin, respectively. We further validated the top three candidates using nitrofurantoin-susceptible and resistant clinical isolates. Notably, the combination of nitrofurantoin and dequalinium demonstrated strong synergistic activity, observed in 68% of susceptible Escherichia coli strains and 94% of resistant Klebsiella pneumoniae strains tested. Combined inhibition of the citric acid cycle by nitrofurantoin and F1-ATPase by dequalinium resulted in a significant reduction in ATP levels compared to either treatment alone. Importantly, decreased ATP levels did not increase persister cell formation, and dequalinium alone reduced persister cell populations more effectively than nitrofurantoin. However, nitrofurantoin is processed into a poorly understood reactive intermediate whose specific metabolic targets have not been fully elucidated. Using metabolomic analyses, we identified aconitase and isocitrate dehydrogenase--key enzymes in the citric acid cycle--as altered in response to nitrofurantoin. Together, these findings demonstrate that dual targeting of bacterial metabolism by nitrofurantoin and dequalinium represents a promising therapeutic strategy for treating drug-resistant Klebsiella spp. in UTIs.

microbiology↗

bioRxiv2026

Anti-psychotic drugs act synergistically in combination with antifungal drugs to inhibit drug-resistant Cryptococcus and Candida species

Systemic antifungal infections cause an estimated 3.8 million deaths annually, approximately 10% of which are caused by drug-resistant infections. With only five classes of antifungal drugs, treatment options are limited. Here we explore synergistic drug combinations - when the efficacy of two drugs combined is greater than expected based on the sum of each individual drugs efficacy - to improve treatment of drug-resistant Cryptococcus neoformans and Candida species. Chlorpromazine acts synergistically with both amphotericin B and fluconazole against multiple fungal species, including azole-resistant C. neoformans and C. auris. We then performed a genome-wide knockout mutant screen and found that ESCRT pathway mutants are resistant to chlorpromazine and knockout mutants of genes involved in fatty acid biosynthesis are sensitive. Based on these data, we investigated sterols and fatty acids in chlorpromazine-treated cells and found only minor increases in sterol precursors but a substantial increase in lipid droplet size and decrease lipid droplet number. We conclude that chlorpromazine acts by potentially sequesters lipids, preventing lipolysis and lipid mobilization in response to stress. Together, these data suggest that chlorpromazine and its analogs are potentially promising treatments for systemic fungal infections that act via lipid homeostasis and stress response.

microbiology↗

bioRxiv2022

Distinct pathways of adaptive evolution in Cryptococcus neoformans reveal a point mutation in adenylate cyclase with drastic tradeoffs for pathogenicity

Pathogenic fungi populate a wide range of environments and infect a diversity of host species. Despite this substantial biological flexibility, the impact of interactions between fungi and their hosts on the evolution of pathogenicity remains unclear. We studied how repeated interactions between the fungus Cryptococcus neoformans and relevant environmental and mammalian host cells--amoeba and mouse macrophages--shape the evolution of this model fungal pathogen. First, using a collection of clinical and environmental isolates of C. neoformans, we characterized a range of survival phenotypes for these strains when exposed to host cells of different species. We then performed serial passages of an environmentally isolated C. neoformans strain through either amoeba or macrophages for ~75 generations to observe how these interactions select for improved replication within hosts. In an adapted population, we identified a single point mutation in the adenylate cyclase gene, CAC1, that swept to fixation and confers a strong competitive advantage for growth inside of macrophages. Strikingly, this growth advantage in macrophages is inversely correlated with disease severity during mouse infections, suggesting that adaptations to specific host niches can markedly reduce the pathogenicity of these fungi. These results raise intriguing questions about the influence of cAMP signaling on pathogenicity and highlight the role of seemingly small adaptive changes in promoting fundamental shifts in the intracellular behavior and virulence of these important human pathogens.

microbiology↗

bioRxiv2020

Phosphate Induces a Morphological Shift that Enhances Vascular Dissemination of Cryptococcus neoformans

Environmental pathogens, which move from ecological niches to mammalian hosts, must adapt to dramatically different environments. Microbes that disseminate farther, including the fungal meningitis pathogen Cryptococcus neoformans, require additional adaptation to diverse tissues. When C. neoformans enters the lungs, infecting cells (<10 m diameter) enlarge (>30 m diameter), then form a heterogeneous population. The brain contains uniformly small cells ([~]7 m). We demonstrate that formation of a small C. neoformans morphotype - called "seed" cells due to their disseminating ability - is critical for extrapulmonary organ entry. Seed cell formation is triggered by environmental factors, including C. neoformans environmental niche, pigeon guano. The underlying trigger, phosphate, can be released by tissue damage, potentially establishing a feed-forward loop of seed cell formation and dissemination. We demonstrate that C. neoformans size variation is not just a continuum but inducible subpopulations that change host interactions to facilitate microbe survival and spread.

microbiology↗

bioRxiv2019

synergistic and antagonistic drug interactions in the treatment of systemic fungal infections

Invasive fungal infections cause 1.6 million deaths annually, primarily in immunocompromised individuals. Mortality rates are as high as 90% due to limited number of efficacious drugs and poor drug availability. The azole class antifungal, fluconazole, is widely available and has multi-species activity but only inhibits fungal cell growth instead of killing fungal cells, necessitating long treatments. To improve fluconazole treatments, we used our novel high-throughput method, the overlap2 method (O2M), to identify drugs that interact with fluconazole, either increasing or decreasing efficacy. Although serendipitous identification of these interactions is rare, O2M allows us to screen molecules five times faster than testing combinations individually and greatly enriches for interactors. We identified 40 molecules that act synergistically (amplify activity) and 19 molecules that act antagonistically (decrease efficacy) when combined with fluconazole. We found that critical frontline beta-lactam antibiotics antagonize fluconazole activity. A promising fluconazole-synergizing anticholinergic drug, dicyclomine, increases fungal cell permeability and inhibits nutrient intake when combined with fluconazole. In vivo, this combination doubled the time-to-endpoint of mice with disseminated Cryptococcus neoformans infections. Thus, our ability to rapidly identify synergistic and antagonistic drug interactions can potentially alter the patient outcomes.

microbiology↗

bioRxiv2018

A Novel in vivo Model of Anaerobic Infection: The Investigation of Clostridium perfringens in Galleria mellonella Larvae.

ABSTRACTImportant research progress into the mechanisms of Clostridium perfringens associated diseases (CPAD) has been slowed by the lack of a reliable infection model. Wax moth larvae (Galleria mellonella) have emerged as a viable alternative to traditional mammalian organisms since they are economic, survive at 37{degrees}C and require no specialist equipment. This study aims to establish whether G. mellonella larvae can be developed as a viable model for the study of CPAD and their suitability for studying novel treatment strategies. In addition, the study demonstrates a novel time-lapse approach to data collection. Mortality and morbidity rates of larvae challenged with 105 CFU of C. perfringens isolates from various sources were observed over 72h and dose response data obtained using inoculum sizes of 10 - 105 CFU. Phenoloxidase enzyme activity was investigated as a marker for immune response and tissue burden by histopathological techniques. Results show that C. perfringens is pathogenic towards G. mellonella although potency varies between isolates. Infection activates the melanisation pathway resulting in melanin deposition but no increase in enzyme activity was observed. Efficacy of antibiotic therapy (penicillin G, bacitracin, neomycin and tetracycline) administered parenterally loosely correlates with that of in vitro analysis. The findings suggest G. mellonella can be a useful in vivo model of infection when investigating CPAD. Although they are unlikely to replace traditional mammals they may be useful as a pre-screening assay for virulence of C.perfringens strains or as a simple, cheap and rapid in vivo assay in the development and pre-clinical development of novel therapeutics.\n\nHighlightsO_LINovel in vivo model for the study of Clostridium perfringens infection.\nC_LIO_LINovel time-lapse approach to data collection.\nC_LIO_LIFirst report of the use of G. mellonella model for characterizing virulence in C. perfringens strains.\nC_LIO_LIAntibiotic therapy in the model that loosely correlates with in vitro testing.\nC_LI

microbiology↗

bioRxiv2017

Regulated release of cryptococcal polysaccharide drives virulence and suppresses immune cell infiltration into the central nervous system

Cryptococcus neoformans is a common environmental yeast and opportunistic pathogen responsible for 15% of AIDS-related deaths worldwide. Mortality primarily results from meningoencephalitis, which occurs when fungal cells disseminate from the initial pulmonary infection site and spread to the brain. A key C. neoformans virulence trait is the polysaccharide capsule. Capsule shields C. neoformans from immune-mediated recognition and destruction. The main capsule component, glucuronoxylomannan (GXM), is found both attached to the cell surface and free in the extracellular space (as exo-GXM). Exo-GXM accumulates in patient serum and cerebrospinal fluid at g/mL concentrations, has well-documented immunosuppressive properties, and correlates with poor patient outcomes. However, it is poorly understood whether exo-GXM release is regulated or the result of shedding during normal capsule turnover. We demonstrate that exo-GXM release is regulated by environmental cues and inversely correlates with surface capsule levels. We identified genes specifically involved in exo-GXM release that do not alter surface capsule thickness. The first mutant, liv7{triangleup}, released less GXM than wild-type cells when capsule is not induced. The second mutant, cnag_00658{triangleup}, released more exo-GXM under capsule-inducing conditions. Exo-GXM release observed in vitro correlated with polystyrene adherence, virulence, and fungal burden during murine infection. Additionally, we find that exo-GXM reduces cell size and capsule thickness in capsule-inducing conditions, potentially influencing dissemination. Finally, we demonstrated that exo-GXM prevents immune cell infiltration into the brain during disseminated infection and highly inflammatory intracranial infection. Our data suggest that exo-GXM performs a different role from capsule GXM during infection, altering cell size and suppressing inflammation.\n\nImportanceCryptococcus neoformans is a leading cause of life-threatening meningoencephalitis in humans. C. neoformans cells produce an immunosuppressive polysaccharide, glucuronoxylomannan (GXM), that is the main component of a protective surface capsule. GXM is also released free into extracellular space as exo-GXM, although the distinction between cell-attached GXM and exo-GXM has been unclear. Exo-GXM influences the outcome of infection, is the basis for current diagnostic tools, and has potential therapeutic applications. This study increases our basic understanding of the fungal biology that regulates polysaccharide release, suggesting that the release of cell-attached GXM and exo-GXM are distinctly regulated. We also introduce a new concept that exo-GXM may alter cell body and capsule size, thereby influencing dissemination in the host. Finally, we provide experimental evidence to confirm clinical observations that exo-GXM influences inflammation during brain infection.

microbiology↗