Biology subjects

Wambaugh, M. A.

Publications and source records attributed to Wambaugh, M. A..

3 recordsLinked to original sources

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↗

bioRxiv2017

Context-dependent Requirements for FimH and Other Canonical Virulence Factors in Gut Colonization by Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) act as commensals within the mammalian gut, but can induce pathology upon dissemination to other host environments such as the urinary tract and bloodstream. It is thought that ExPEC genomes are shaped in large part by evolutionary forces encountered within the gut where the bacteria spend much of their time, provoking the question of how their extraintestinal virulence traits arose. The principle of coincidental evolution, in which a gene that evolved in one niche happens to be advantageous in another, has been used to argue that ExPEC virulence factors originated in response to selective pressures within the gut ecosystem. As a test of this hypothesis, the fitness of ExPEC mutants lacking canonical virulence factors was assessed within the intact murine gut in the absence of any antibiotic treatment. We found that most of the tested factors--including CNF1, Usp, colibactin, flagella, and the plasmid pUTI89--were dispensable for gut colonization. Deletion of genes encoding the adhesin PapG or the toxin HlyA caused transient defects, but did not affect longer-term persistence. In contrast, a mutant missing the type 1 pilus-associated adhesin FimH displayed reduced persistence within the gut. However, this phenotype was variable, being dependent on the presence of specific competing strains and partially attributable to aberrant flagellin expression by the fimH mutant. These data indicate that FimH and other key ExPEC-associated factors are not strictly required for gut colonization, suggesting that selective pressures within the gut do not drive the development of all extraintestinal virulence traits.

microbiology↗