PHAR 506: EXAM I Lecture Review

(1/17) Flowers Lecture: Microbiome in Infectious Disease: Allies and Adversaries Defining the Microbiome: A collection of microbes or microorganisms that inhabit an environment

- Inhabitants: Prokaryotes/Bacteria (largest component), Viruses, Eukaryotes - Diversity: There is significant microbial diversity in body sites and between individuals.

o By understanding the role of microbiota shifts, we may predict an individuals ‘health status’ - Human Microbiome: 1:1 Cellular ratio between mammal and microbial cells, 3 lbs of Bacteria in intestines!

Symbiotic Relationships – The Host and Microbes - Host-Microbial Mutualism: Analyzing the benefits conferred by microbes to humans

o Production of beneficial metabolites (SCFA, 20 Bile acids, NT, Choline) and Eliminate harmful (Choline) § Mammals are less capable of producing SCFA, such as acetate, propionate, and butyrate

• Butyrate is the ‘essentially’ the only energy source for colonocytes § 90% of Serotonin (5-HT) is made in the gut. Regulation of synthesis is by gut bacteria § Choline, a component of red meats, can be linked to the regression of cardiovascular disease. The

intestinal bacteria are capable of ‘fixing’ these potentially harmful metabolites o Vitamin Synthesis – gut bacteria produce some vitamins, like VitD and VitK o Resistance against invading pathogens o Maturation of mucosal immune system and immune cells: As proven by studies evaluating the

effectiveness of the immune system in gnotobiotic mice, its strength is derived by gut microbiome. - Host-Microbial Dysbiosis: Maladaptation of the gut microbial community, leading to constitutive inflammation

o Host Genetics: Mutations in genes involved in the inflammatory pathways o Lifestyle: Diet and Stress – the western diet (ÝFat, ßFiber) has been tied to underlying inflammation o Early Colonization: Though not necessarily lasting until adulthood, birthing procedures play a role o Medical Practices: Vaccination administration, antibiotic (abx) use, and hygiene, medications

§ Many prescription medications affect the microbiome. As predicted, drug classes like PPIs exhibit a strong influence on the microbiome due to their alteration of the digestive environment (pH), though there are others related to cardiac health that may be surprising (Statins, ACE-I, etc)

§ Main Rx Offenders: Broad spectrum abx (beta-lactams, fluoroquinolones, tigecycline, cleocin) § Favorable Perturbations: Rifaximin – Used to tx Traveler’s Diarrhea, this drug inhibits RNA

polymerase, specifically decreasing inflammation and promoting beneficial bacteria - The Role of Host-Microbe Relationships

o Recent studies have been showing the significant role the gut microbiome plays in: mood disorders, sleep, stress, chronic disease states, allergies, and much more.

Methods of Studying the Microbiome - Culture Techniques: Predominantly obligate anaerobes, most gut species are difficult to culture - Non-Culture Techniques: Use high-throughput, parallel, multiplex sequencing to define the microbial community - 16s rRNA Surveys: By sequencing bacterial hypervariable regions specific to prokaryotes, we can identify and

monitor phylogenetic relationships Clostridium difficile Infection (CDI)

- Infection: C. diff is a gram-positive, spore-forming bacteria that leads to 30,000 deaths annually. The infection is manageable with abx; though in severe cases, with abx-resistance, infection may lead to sepsis, UC, D, and death

o Non-Modifiable Risk Factors: Age, Hospitalization o Modifiable Risk Factors: Usage of PPIs, Broad spectrum abx (cleocin, cephalo-, aminopenicillins, fq) o Decreased microbial diversity is associated with severe and recurrent CDI

- Recurrent CDI: The high rate of recurrence of most likely due to persisting low-grade microbial diversity. Recurrence most frequently occurs within 1-2 weeks of finishing tx, and has the following risk factors:

o ÝAge, Abx in follow-up period, PPIs, Renal insufficiency - Nood et al – ‘Duodenal Infusion of Donor Feces for Recurrent C. diff’

o Open-label, RCT, treating CDI patients with Fecal Microbiota Transplantation vs Vancomycin. The fecal transplants are significantly more efficacious! à Role of the microbial community

- Drekonja et al – Follow-up systematic review of FMT for C. diff o Showed an overall cure rate of 85% for CDI

Fecal Microbiota Transplantation (FMT) - The introduction of a fecal suspension derived from a healthy donor into the GI tract of a diseased individual. The

rationale is that the re-introduction of a complete and stable community of gut microbiota will repair and replace disrupted native microbiota. –Exogenously replenishing the microbiome of patients

- Methods: Naso-duodenal tube, Colonoscopy, Rectal Enema - Mechanism: Combats the Resistome (the dramatically strengthened incidence of abx-resistance bacteria)

o Abx tx depletes the abx-susceptible bacteria, allowing for the overgrowth of abx-resistance bacteria. Following FMT tx, there is less resistance and a replenishment of eubacteria.

Probiotic vs Prebiotic - The seed and the fertilizer - - Probiotics: Live microorganisms that have health benefits when consumed

o Source: Yogurt (non-pasteurized), supplements o Main Contributors: Lactobascillus, Bifidobacterium, Saccromyces o Hempel et al: Large meta-analysis consisting of 63 RCT and >11k participants, found that:

§ Using probiotics as adjunct therapy to abx reduced the risk of Abx-Associated-Diarrhea by 58% - Prebiotics: Non-living, non-digestible carbohydrates that stimulate the healthy gut microbiota metabolism

o 3 Requirements: (1) Must resist mammalian metabolism/absorption in the upper GI, (2) must be fermented by intestinal bacteria, and (3) selectively stimulate the growth/activity of intestinal bacteria associated with health

o Main Contributors: Inulin, Resistant Starch, Gum (1/19) Rodvold Lecture: Principles for Using Anti-Infective Agents Exam content from this lecture is a complete toss-up. He stated (paraphrasing) – his exam questions will come from the handout. Nevertheless, from lecture, the seemingly significant themes were:

- Start with empiric therapy if needed, but the final goal is definitive therapy if needed - The 10 questions, and knowing that questions 4-10 rely on the Pharmacist for optimal therapy - The 5 Ds, which is another way of addressing the 10 questions. It is his personal contribution, which has been

accepted in the antimicrobial therapy community. - The Triangle: Infection, Pathogen, Antibiotic

o Given one of these, we should know how to answer the other two in all situations. o Ex: Knowing the infection, we should be able to produce what pathogen can cause it, and what antibiotic

we would treat it with. Personally, I think my notes on this lecture were crappy. This lecture attempted to teach high-tech common sense. How anti-infective agents differ from other drugs

- Anti-infective MoA: Directly affect pathogens, inhibiting their growth or by complete eradication - Lab Utility: Contrary to other drugs, the target of anti-infectives can be isolated, identified, and studied in the lab.

In vitro susceptibility tests can also be used, providing predictive knowledge of PK and PD properties of the anti-infective

o The concentration of the compound can be measured over time with biological assays o The antimicrobial effect can be determined throughout the course of therapy.

- Microflora and Risk: Anti-infective drugs may alter the normal microbial flora, potentially leading to vulnerabilities to additional infectious diseases and the development of superinfections

o Microorganisms may become resistant to anti-infective drugs through mutation, transduction, transfer of genetic material, or gene induction. This is due to a powerful selective pressure placed on the microorganisms by the anti-infective drug.

o Combating the Risk: Methods have been developed to reduce, delay, and overcome resistant mechanisms § Combination Therapy § Concurrent b-lactamase inhibitors + b-lactam antibiotics

- Transmission: Resistant microorganisms may be transmitted between patients.