Branching Out: Branched-chain Amino Acids as Key Metabolites in Staphylococcus aureus Physiology and Virulence

What’s so special about the branched-chain amino acids (BCAAs)? We already know that they’re the most abundant amino acids found in proteins, and they drive protein folding. Many bacteria have the genes that direct BCAA synthesis, but intriguingly, some species like S. aureus restrict endogenous BCAA synthesis in order to use environmental amino acid availability to regulate virulence gene expression. In this lecture, I will describe our efforts to understand the role of BCAAs in gene regulation. As diffusible molecules that are consumed by staphylococci in infected tissues, they potentially spatially regulate gene expression on the single-cell level. This heterogeneity is clinically important and may affect how we approach the development of new therapeutics.  
 

Need a Pep Talk? Role of Oligoendopeptidase F Proteins in Controlling Staphylococcal Virulence

Oligoendopeptidase F (PepF) proteins belong to the M3 family of zinc-dependent peptidases found in all domains of life. In animals, this class of enzymes is important for processing peptides that have roles in neuronal signaling and antimicrobial defense. M3 family members are also found in nearly all low G+C gram-positive bacterial genera, spirochetes and proteobacteria. However, the bacterial subclass peptidases are enigmatic. Most PepFs are functionally uncharacterized putative cytoplasmic enzymes, with the exception of Lactococcus lactis PepF proteins that have been suggested to be involved in signal peptide degradation or protein turnover, and a PepF homolog in Bacillus subtilis that affects asymmetric cell division. During a transposon mutagenesis screen, we discovered that 2 Staphylococcus aureus PepF proteins are essential for full activity of the SaeR/S two-component system. SaeR/S was discovered nearly 30 years ago and controls the synthesis of over 20 virulence factors, and disrupting pepF paralogs is correlated with attenuated virulence in a mouse infection model. In this lecture, I’ll discuss our progress to define and characterize a novel system modulating one of the most important regulators of virulence factor production in S. aureus. 
 

Chewing the Fat: Lipids as Second Messengers in Staphylococcus aureus Signal Transduction

Two-component systems (TCSs) are the predominant signal transduction systems in bacteria for monitoring their external environment. Typical TCSs contain a membrane histidine kinase with a large extracellular domain that binds a ligand. The resulting autophosphorylation and phosphoryl transfer to a response regulator DNA binding protein adjusts gene expression. We discovered a subclass of TCS histidine kinases that is responsive to the lipid composition of the bacterial phospholipid bilayer. In this lecture, I will discuss our efforts to combine classical genetic and biochemical techniques with native mass spectrometry and spatial lipidomics to understand the mechanism by which branched-chain fatty acids and cardiolipin alter the activity of these histidine kinases. Parallels with eukaryotic lipids as second messengers will be discussed. 
 

Lean on Me (for Lipids): Metabolic Synergy Between Staphylococcus aureus and Enterococcus faecalis During Polymicrobial Infection

While some bacterial infections are caused by a single species, we now know that most infections are polymicrobial in origin. We know that the activities of these species are often synergistic, as interactions between species enhance virulence, persistence and tolerance to antibiotics. The end result is patient outcomes that are typically worse in co-infection compared to mono-infection. Staphylococcus aureus is the leading cause of skin and soft tissue infections. The bacterium is also the most common organism isolated from chronic wounds and is frequently found with the opportunistic pathogen Enterococcus faecalis. Despite these frequent observations, our knowledge of the molecular mechanisms governing these interactions in chronic wounds is incomplete. S. aureus is highly dependent on branched-chain fatty acids derived from isoleucine to construct its cell wall. We recently discovered a second biosynthetic pathway to generate fatty acid precursors in this organism that appears to function alongside the well-studied branched-chain alpha-keto acid dehydrogenase complex. In this lecture, I will discuss our recent results suggesting that E. faecalis supplies metabolic intermediates for S. aureus membrane biogenesis via this new pathway, promoting its growth and persistence. This pathway may allow S. aureus to adapt its metabolism and enhance its survival in the nutrient-limited and competitive settings of polymicrobial infections. Detailed understanding of this metabolic synergy is the important first step toward developing novel therapeutics to combat these complex infections. 

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in doing the following:

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Give separate lecture for students.
• Participate in informal gatherings/discussions—at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.  

Dissemination of Listeria monocytogenes Following Foodborne Infection 

The facultative intracellular bacterial pathogen Listeria monocytogenes faces several different bottlenecks in the gastrointestinal tract to cause life-threatening systemic infections. This lecture will describe the foodborne model of murine infection developed by the D’Orazio lab and highlight what we know about the mechanisms used by the bacteria to invade the intestinal mucosa, avoid clearance by phagocytes in the underlying lamina propria, transit to the draining lymph nodes and then use cell-to-cell spread to exit into the bloodstream.
 

Axonal Migration of Neurotropic Strains of Listeria monocytogenes 

The most common form of listeriosis in ruminants is a brainstem infection called rhombencephalitis. These infections also happen in humans and can occur in young, otherwise healthy individuals, suggesting that the pathogenesis is a function of the bacterial virulence rather than any deficiency in the immune status of the host. This lecture will highlight our work to understand how certain neurotropic strains of L. monocytogenes have the ability to invade cranial nerves in the gut and then used actin-based motility to spread within an axon all the way to the brainstem.
 

Listeria monocytogenes: A Model Intracellular Pathogen That Has Taught Us So Much About Innate and Adaptive Immunity 

Systemic listeriosis has been a favored infection model used by immunologists for decades because it induces a robust cytotoxic T cell response that results in sterilizing immunity with long-lasting protective memory. The intravenous model of infection is highly reproducible and the bacteria can be manipulated genetically making it a very useful model system. This lecture will highlight how L. monocytogenes has been used to better understand all facets of a protective immune response, including vaccine development.  

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in the following: 

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Give separate lecture for students.
• Participate in informal gatherings/discussions—at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.
• This speaker is a first generation college student and would especially enjoy talking to first-gen students in any capacity.  

Bacteriophage-Host Interactions That Shape Fitness and Evolution 

This lecture covers topics focused on the evolution of phage resistance and its impact on bacterial fitness, ranging from host colonization to antibiotic resistance.
 

Insertion Sequence Driven Evolution of the Microbiota

We have developed bioinformatic tools to study a diverse class of mobile elements known as insertion sequences. This lecture highlights the utility of these tools to study microbial communities and discusses recent discoveries that are reshaping the way we think about the function of the microbiota.
 

Charting Anitphage Defenses Using Conserved Mobile Genetic Element Genes 

This lecture presents our work using bioinformatics and bacterial genetics showing that broadly conserved serine recombinase genes are proximal to a variety of antiphage defense systems. Many of these are uncharacterized phage defense systems. 
 

Enterococcal Colonization of the Intestine

This lecture explores the molecular biology of the enterococcal cell surface and how it supports intestinal colonization and interactions with host mucosal immunity.  

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in doing the following:

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Participate in informal gatherings/discussions—at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.  

A Plague on Both Your Houses: Using Yersinia pestis to Better Understand Leukocyte Biology

Macrophages and neutrophils are our innate immune system’s first responders to infection. These leukocytes have both antimicrobial and inflammatory responses that are essential in controlling infection. Successful bacterial pathogens have evolved a multitude of mechanisms to evade and even subvert the actions of these cells. As such, bacteria have proven to be valuable tools in defining the molecular mechanisms involved in leukocyte responses. In this lecture, I will discuss how researchers have used Yersinia pestis to better understand macrophage and neutrophil responses to infection and the discovery of virulence strategies used by this pathogen to establish the lethal infection known as the plague.
 

Got Zinc? Bacterial Mechanisms to Overcome Nutritional Immunity 

Metals like iron, zinc, and manganese are co-factors for many proteins and are essential nutrients for all organisms on our planet, including bacteria. However, high concentrations of metals can also prove toxic to bacteria. Because of the double-edged nature of these metals, we have evolved strategies of both metal limitation and intoxication to inhibit bacterial infections, a concept generally referred to as nutritional immunity. However, all successful pathogens have, in turn, evolved mechanisms to specifically overcome nutritional immunity. In this lecture, I will introduce the concept of nutritional immunity and provide examples of virulence factors that allow bacteria to overcome this key innate barrier to infection. We will also discuss how these mechanisms can be targeted as potential novel antimicrobial strategies. 
 

Safety First! What it Takes to Work in a BSL-3 Laboratory 

Many emerging and re-emerging pathogens require special facilities and procedures to allow scientists to safely carry out studies needed to develop new vaccines and therapeutics. Biosafety level 3 (BSL-3) laboratories incorporate elevated biosafety and biosecurity practices to safely conduct research with pathogens at a risk for aerosol transmission and protect laboratorians, the environment and our communities. In this lecture, I will discuss how researchers and biosafety experts use BSL-3 practices to mitigate risk to safely and securely conduct research essential for public health.  

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in doing the following:

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Give separate lecture for students.
• Participate in informal gatherings/discussions—at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.  

Why Do Pathogens Continue to Emerge and Reemerge? An Update

The National Institute of Allergy and Infectious Diseases defines “emerging infectious diseases/pathogens” as those “that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range.” The 21st century has seen a concerning number of old foes and novel microbial agents emerge [or reemerge] globally. SARS-CoV-2, mpox, Ebola, Nipah, Marburg, Candida auris, ringworm, antimicrobial resistant pathogens, arboviruses and many other dangerous microbes are in the headlines daily. This presentation will discuss several pathogens, examining pathology, epidemiology, treatment, prevention and other microbiological and infectious disease aspects to consider going forward.
 

Antimicrobial Resistance [AMR] as it Relates to Biofilm: Mechanics, Surfaces and Problems that Need Solving

One of the biggest challenges in environmental infection prevention is the re-contamination/re-growth of pathogens on surfaces. Maintaining an environment of care with minimal bioburden is critical to prevent transmission of infectious agents to susceptible patients. Implementation of proper surface cleaning and disinfection processes is one of the most important strategies to prevent health care-associated infections [HAIs] which can hinge upon using the right chemicals. Recent advances with disinfection chemistries include continuously active disinfectants (CADs) that continuously kill microbes, providing additional protection against re-transmission of pathogens.
 

Breaking Down the Science of AMR for Patients and the Public 

AMR is an umbrella term, which explains how bacteria, viruses and other microbes [fungi] can develop resistance to medications like antibiotics, making infections harder to treat, due to their ability to evade the drugs designed to kill them. This presentation will describe this serious global health threat, primarily driven by overuse and misuse of medications, and discuss the importance of understanding how resistance occurs to inform responsible antibiotic use, prevent further complications and safeguard the effectiveness of future treatments. Examples of AMR pathogens will be given.
 

Rabies: A New Look at an Old Foe! 

This presentation will provide information on rabies virus and public health education. As an inaugural member of the Texas Oral Rabies Vaccination Program in Texas, which has eliminated canine rabies in Texas, I used my training as a Visiting Scientist with CDC Rabies Virus Laboratory to help create the Texas Department of State Health Services Regional Reference Rabies Virus Variant Typing Laboratory. This lecture will discuss rabies virus diagnosis, epidemiology and specimen types.
 

TED Talks & Science Communication: Telling Your Story!

This presentation will discuss my personal experience with the TED Talk process, how to leverage one’s research and subject matter expertise at the international level, how to identify effective strategies to synergize one’s expertise in social media channels, media interviews, authoring explainer articles and working globally in a One Health framework.
 

The Resurgence of Vaccine-Preventable Infections: A U.S. Update

When enough individuals neglect or choose to not receive their immunizations, the entire community immunization rates drop, and disease often occurs. Why do vaccine-preventable diseases occur in the United States? There are many factors to consider, such as low immunization rates, vaccine hesitancy, globalization and microbial adaptation. Immunization by vaccination prevents diseases, disabilities and deaths from vaccine-preventable diseases (VPDs), such as cervical cancer, poliomyelitis, measles, rubella, diphtheria, tetanus, pertussis, hepatitis A and B, bacterial pneumonias, rotavirus diarrheal diseases and bacterial meningitis. A review and update will be provided on the current resurgence of VPDs in the U.S.
 

Professional Identity and the Intersection of Medical Laboratory and Public Health Practice 

This presentation will explore the intersection between public health and the medical laboratory professional identity. It is intended for laboratory leaders and other personnel in the public health and medical laboratory environment.

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in doing the following:

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Give separate lecture for students.
• Participate in informal gatherings/discussions – at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.
• Meet online with students, early professionals, and other colleagues to discuss my career journey and provide a sounding board for questions and concerns.  

Consequences of Viral-Bacterial Synergy 

Interkingdom interactions between bacteria and viruses play critical roles at the host–pathogen interface with both synergistic and antagonistic relationships being operative. These studies encompass the virulence strategies that are specifically operative during viral-bacterial co-infection that impact several cellular processes to drive the heightened pathogenic cascade observed both clinically and experimentally.
 

Evolutionary Constraints of Antibiotic Resistance 

Instrumental in the development of resistance is a bacterium’s inherent ability to survive transient exposure to antibiotics giving the population the opportunity to accumulate genomic changes, gradually leading to full clinical resistance. A critical aspect in the development of resistance is the contribution of transient cell-states of tolerant bacterial populations, whose prominent role in subsequent development of resistance and in antibiotic treatment failure is becoming increasingly recognized. We have undertaken a multi-faceted approach to interrogate the mechanisms of antibiotic tolerance and the restrictions on the emergence of antibiotic resistance using a combination of experimental evolution and high-throughput genetics.
 

Pneumococcal Pathogenesis

The pneumococcus is a remarkedly adaptable pathogen, being able to not only colonize the human host asymptomatically, but also cause serious disease in a diverse array of host niches. Using high-throughput genetic screens, we have identified several key virulence determinants that are operative at specific host niches, such as colonization, pneumonia and bloodstream infections. This seminar focuses on the strategies the pneumococcus utilizes to infect such disparate host niches and means by which these virulence mechanisms can be disarmed to treat infections more effectively.  

In addition to providing lectures for Branch meetings, ASMDL Lecturers are available to participate in career development and mentoring activities for trainees at Branch meetings. This ASMDL Lecturer has indicated interest in doing the following:

• Attend poster sessions and oral presentations.
• Judge posters and/or oral presentations.
• Give separate lecture for students.
• Participate in informal gatherings/discussions—at dinner, reception, etc.
• Attend an ASM Student Chapter meeting. 
• Participate in a career forum.
• Hold a “Meet the Speaker” session.