Rational manipulation of mRNA folding free energy allows rheostat control of pneumolysin production by Streptococcus pneumoniae.

The contribution of specific factors to bacterial virulence is generally investigated through creation of genetic "knockouts" that are then compared to wild-type strains or complemented mutants. This paradigm is useful to understand the effect of presence vs. absence of a specific gene product but cannot account for concentration-dependent effects, such as may occur with some bacterial toxins.

α-Intercalated cells defend the urinary system from bacterial infection.

α-Intercalated cells (A-ICs) within the collecting duct of the kidney are critical for acid-base homeostasis. Here, we have shown that A-ICs also serve as both sentinels and effectors in the defense against urinary infections. In a murine urinary tract infection model, A-ICs bound uropathogenic E.

Vaginolysin drives epithelial ultrastructural responses to Gardnerella vaginalis.

Gardnerella vaginalis, the bacterial species most frequently isolated from women with bacterial vaginosis (BV), produces a cholesterol-dependent cytolysin (CDC), vaginolysin (VLY). At sublytic concentrations, CDCs may initiate complex signaling cascades crucial to target cell survival. Using live-cell imaging, we observed the rapid formation of large membrane blebs in human vaginal and cervical epithelial cells (VK2 and HeLa cells) exposed to recombinant VLY toxin and to cell-free supernatants from growing liquid cultures of G.

β-Hemolysin/cytolysin of Group B Streptococcus enhances host inflammation but is dispensable for establishment of urinary tract infection.

Group B Streptococcus (GBS; Streptococcus agalactiae) is a major human pathogen that disproportionately affects neonates and women in the peripartum period and is an emerging cause of infection in older adults. The primary toxin of GBS, β-hemolysin/cytolysin (βH/C), has a well-defined role in the pathogenesis of invasive disease, but its role in urinary tract infection (UTI) is unknown. Using both in vitro and in vivo models, we analyzed the importance of βH/C in GBS uropathogenesis.

Cigarette smoke increases Staphylococcus aureus biofilm formation via oxidative stress.

The strong epidemiological association between cigarette smoke (CS) exposure and respiratory tract infections is conventionally attributed to immunosuppressive and irritant effects of CS on human cells. Since pathogenic bacteria such as Staphylococcus aureus are members of the normal microbiota and reside in close proximity to human nasopharyngeal cells, we hypothesized that bioactive components of CS might affect these organisms and potentiate their virulence. Using Staphylococcus aureus as a model organism, we observed that the presence of CS increased both biofilm formation and host cell adherence.

Virulence attenuation of Candida albicans genetic variants isolated from a patient with a recurrent bloodstream infection.

The incidence of Candida albicans infections and the relapse episodes after antifungal treatment have increased in recent decades. Recurrences are mainly due to the persistence of the original infecting strain that may present genetic and genomic rearrangements during interaction with the host, reflecting strain adaptation. In this study, four isolates recovered from a patient during recurrent candidemia episodes were genotyped by microsatellite length polymorphism (MLP) and by multilocus sequence typing (MLST) and found to be genetic variants of the same strain.