Intestinal calcium and bile salts facilitate germination of Clostridium difficile spores.

Clostridium difficile (C. difficile) is an anaerobic gram-positive pathogen that is the leading cause of nosocomial bacterial infection globally. C. difficile infection (CDI) typically occurs after ingestion of infectious spores by a patient that has been treated with broad-spectrum antibiotics. While CDI is a toxin-mediated disease, transmission and pathogenesis are dependent on the ability to produce viable spores. These spores must become metabolically active (germinate) in order to cause disease. C. difficile spore germination occurs when spores encounter bile salts and other co-germinants within the small intestine, however, the germination signaling cascade is unclear. Here we describe a signaling role for Ca2+ during C. difficile spore germination and provide direct evidence that intestinal Ca2+ coordinates with bile salts to stimulate germination. Endogenous Ca2+ (released from within the spore) and a putative AAA+ ATPase, encoded by Cd630_32980, are both essential for taurocholate-glycine induced germination in the absence of exogenous Ca2+. However, environmental Ca2+ replaces glycine as a co-germinant and circumvents the need for endogenous Ca2+ fluxes. Cd630_32980 is dispensable for colonization in a murine model of C. difficile infection and ex vivo germination in mouse ileal contents. Calcium-depletion of the ileal contents prevented mutant spore germination and reduced WT spore germination by 90%, indicating that Ca2+ present within the gastrointestinal tract plays a critical role in C. difficile germination, colonization, and pathogenesis. These data provide a biological mechanism that may explain why individuals with inefficient intestinal calcium absorption (e.g., vitamin D deficiency, proton pump inhibitor use) are more prone to CDI and suggest that modulating free intestinal calcium is a potential strategy to curb the incidence of CDI.

Factors associated with incomplete childhood immunization in Arbegona district, southern Ethiopia: a case--control study.

BACKGROUND: The prevention of child mortality through immunization is one of the most cost-effective and widely applied public health interventions. In Ethiopia, the Expanded Program on Immunization (EPI) schedule is rarely completed as planned and the full immunization rate is only 24%. The objective of this study was to identify determinant factors of incomplete childhood immunization in Arbegona district, Sidama zone, southern Ethiopia. METHODS: A community based unmatched case-control study was undertaken among randomly selected children aged 12 to 23 months and with a total sample size of 548 (183 cases and 365 controls). A multi-stage sampling technique was used to get representative cases and controls. Data was collected using a structured questionnaire and analyzed using SPSS version 16 statistical software. Bivariate and multiple logistic regression analyses were done to identify independent factors for incomplete immunization status of children. Qualitative data were also generated and analyzed using thematic framework. RESULTS: The incomplete immunization status of children was significantly associated with young mothers (AOR = 9.54; 95% CI = 5.03, 18.09), being born second to fourth (AOR = 3.64; 95% CI = 1.63, 8.14) and being born fifth or later in the family (AOR = 5.27; 95% CI = 2.20, 12.64) as compared to being born first, a mother's lack of knowledge about immunization benefits (AOR = 5.51; 95% CI = 1.52, 19.94) and a mother's negative perception of vaccine side effects (AOR = 1.92; 95% CI = 1.01, 3.70). The qualitative finding revealed that the migration of mothers and unavailability of vaccines on appointed immunization dates were the major reasons for partial immunization of children. CONCLUSION: To reduce the number of children with incomplete immunization status, the Arbegona district needs to consider specific planning for mothers with these risk profiles. A focus on strengthening health communication activities to raise immunization awareness and address concerns of vaccine side effects at community level is also needed. This could be achieved through integrating the immunization service to other elements of primary health care.

Suggestions for Improving Invited Speaker Diversity To Reflect Trainee Diversity.

Within the field of biomedical research in the United States, the proportion of underrepresented minorities at the Full Professor level has remained consistently low, even though trainee demographics are becoming more diverse. Underrepresented groups face a complex set of barriers to achieving faculty status, including imposter syndrome, increased performance expectations, and patterns of exclusion. Institutionalized racism and sexism have contributed to these barriers and perpetuated policy that excludes underrepresented minorities. These barriers can contribute to decreased feelings of belonging, which may result in decreased retention of underrepresented minorities. Though some universities have altered their hiring practices to increase the number of underrepresented minorities in the applicant pool, these changes have not been sufficient. Here we argue that departmental invited seminar series can be used to provide trainees with scientific role models and increase their sense of belonging while institutions work towards more inclusive policy. In this study, we investigated the demographics (gender and race) of invited seminar speakers over 5 years to the Department of Microbiology and Immunology at the University of Michigan. We also investigated current trainee demographics and compared them to invited speaker demographics to gauge if our trainees were being provided with representation of themselves. We found that invited speaker demographics were skewed towards Caucasian men, and our trainee demographics were not being represented. From these findings, we proposed policy change within the department to address how speakers are being invited with the goal of increasing speaker diversity to better reflect trainee diversity. To facilitate this process, we developed a set of suggestions and a web-based resource that allows scientists, committees, and moderators to identify members of underserved groups. These resources can be easily adapted by other fields or subfields to promote inclusion and diversity at seminar series, conferences, and colloquia.

Women Are Underrepresented and Receive Differential Outcomes at ASM Journals: a Six-Year Retrospective Analysis.

Despite 50% of biology Ph.D. graduates being women, the number of women that advance in academia decreases at each level (e.g., from graduate to postdoctorate to tenure track). Recently, scientific societies and publishers have begun examining internal submissions data to evaluate representation and evaluation of women in their peer review processes; however, representation and attitudes differ by scientific field, and to date, no studies have investigated academic publishing in the field of microbiology. Using manuscripts submitted between January 2012 and August 2018 to the 15 journals published by the American Society for Microbiology (ASM), we describe the representation of women at ASM journals and the outcomes of their manuscripts. Senior women authors at ASM journals were underrepresented compared to global and society estimates of microbiology researchers. Additionally, manuscripts submitted by corresponding authors that were women received more negative outcomes than those submitted by men. These negative outcomes were somewhat mediated by whether or not the corresponding author was based in the United States and by the type of institution for United States-based authors. Nonetheless, the pattern for women corresponding authors to receive more negative outcomes on their submitted manuscripts held. We conclude with suggestions to improve the representation of women and decrease structural penalties against women.IMPORTANCE Barriers in science and academia have prevented women from becoming researchers and experts that are viewed as equivalent to their colleagues who are men. We evaluated the participation and success of women researchers at ASM journals to better understand their success in the field of microbiology. We found that women are underrepresented as expert scientists at ASM journals. This is, in part, due to a combination of both low submissions from senior women authors and more negative outcomes on submitted manuscripts for women compared to men.

Petrobactin Protects against Oxidative Stress and Enhances Sporulation Efficiency in Bacillus anthracis Sterne.

Bacillus anthracis is a Gram-positive bacillus that under conditions of environmental stress, such as low nutrients, can convert from a vegetative bacillus to a highly durable spore that enables long-term survival. The sporulation process is regulated by a sequential cascade of dedicated transcription factors but requires key nutrients to complete, one of which is iron. Iron acquisition by the iron-scavenging siderophore petrobactin is required for vegetative growth of B. anthracis under iron-depleted conditions and in the host. However, the extent to which petrobactin is involved in spore formation is unknown. This work shows that efficient in vitro sporulation of B. anthracis requires petrobactin, that the petrobactin biosynthesis operon (asbA to -F) is induced prior to sporulation, and that the siderophore itself associates with spores. Petrobactin is also required for oxidative stress protection during late-stage growth and for wild-type levels of sporulation in sporulation medium. Sporulation in bovine blood was found to be petrobactin dependent. Collectively, the in vitro contributions of petrobactin to sporulation as well as growth imply that petrobactin may be required for B. anthracis transmission via the spore during natural infections, in addition to its key known functions during active anthrax infections.IMPORTANCEBacillus anthracis causes the disease anthrax, which is transmitted via its dormant, spore phase. However, conversion from bacillus to spore is a complex, energetically costly process that requires many nutrients, including iron. B. anthracis requires the siderophore petrobactin to scavenge iron from host environments. We show that, in the Sterne strain, petrobactin is required for efficient sporulation, even when ample iron is available. The petrobactin biosynthesis operon is expressed during sporulation, and petrobactin is biosynthesized during growth in high-iron sporulation medium, but instead of being exported, the petrobactin remains intracellular to protect against oxidative stress and improve sporulation. It is also required for full growth and sporulation in blood (bovine), an essential step for anthrax transmission between mammalian hosts.

Global gene expression by Bacillus anthracis during growth in mammalian blood.

During the late stages of systemic anthrax, Bacillus anthracis grows rapidly in the host bloodstream. To identify potential genes necessary for this observed rapid growth, we defined the transcriptional profile of B. anthracis during in vitro growth in bovine blood. Genome-wide transcriptome analysis indicated that B. anthracis undergoes significant changes in its transcriptome profile during growth in blood, including the differential regulation of genes associated both with metabolism and known virulence factors. Collectively, these data provide a framework for future studies identifying specific B. anthracis factors required for growth in the mammalian bloodstream.