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Infection and Immunity Bacterial Infections



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Purification of Intracellular Bacterial Communities during Experimental Urinary Tract Infection Reveals an Abundant and Viable Bacterial Reservoir [Bacterial Infections]

2018-03-22T08:01:02-07:00

Urinary tract infections (UTIs) are a major infection of humans, particularly affecting women. Recurrent UTIs can cause significant discomfort and expose patients to high levels of antibiotic use, which in turn contributes to the development of higher antibiotic resistance rates. Most UTIs are caused by uropathogenic Escherichia coli, which is able to form intracellular collections (termed intracellular bacterial communities [IBCs]) within the epithelial cells lining the bladder lumen. IBCs are seen in both infected mice and humans and are a potential cause of recurrent UTI. Genetic and molecular studies of IBCs have been hampered both by the low number of bacteria in IBCs relative to the number extracellular bacteria and by population bottlenecks that occur during IBC formation. We now report the development of a simple and rapid technique for isolating pure IBCs from experimentally infected mice. We verified the specificity and purity of the isolated IBCs via microscopy, gene expression, and culture-based methods. Our results further demonstrated that our isolation technique practically enables specific molecular studies of IBCs. In the first such direct measurement, we determined that a single epithelial cell containing an early IBC typically contains 103 viable bacteria. Our isolation technique complements recent progress in low-input, single-cell genomics to enable future genomic studies of the formation of IBCs and their activation pathways during recurrent UTI, which may lead to novel strategies to eliminate them from the bladder.




Screening and Genomic Characterization of Filamentous Hemagglutinin-Deficient Bordetella pertussis [Bacterial Infections]

2018-03-22T08:01:02-07:00

Despite high vaccine coverage, pertussis cases in the United States have increased over the last decade. Growing evidence suggests that disease resurgence results, in part, from genetic divergence of circulating strain populations away from vaccine references. The United States employs acellular vaccines exclusively, and current Bordetella pertussis isolates are predominantly deficient in at least one immunogen, pertactin (Prn). First detected in the United States retrospectively in a 1994 isolate, the rapid spread of Prn deficiency is likely vaccine driven, raising concerns about whether other acellular vaccine immunogens experience similar pressures, as further antigenic changes could potentially threaten vaccine efficacy. We developed an electrochemiluminescent antibody capture assay to monitor the production of the acellular vaccine immunogen filamentous hemagglutinin (Fha). Screening 722 U.S. surveillance isolates collected from 2010 to 2016 identified two that were both Prn and Fha deficient. Three additional Fha-deficient laboratory strains were also identified from a historic collection of 65 isolates dating back to 1935. Whole-genome sequencing of deficient isolates revealed putative, underlying genetic changes. Only four isolates harbored mutations to known genes involved in Fha production, highlighting the complexity of its regulation. The chromosomes of two Fha-deficient isolates included unexpected structural variation that did not appear to influence Fha production. Furthermore, insertion sequence disruption of fhaB was also detected in a previously identified pertussis toxin-deficient isolate that still produced normal levels of Fha. These results demonstrate the genetic potential for additional vaccine immunogen deficiency and underscore the importance of continued surveillance of circulating B. pertussis evolution in response to vaccine pressure.