Week_31_Bacterial_Infections
Page 1: Bacterial Infections and the Compromised Host
Focus on medical microbiology and immunology as it relates to bacterial infections and immune system responses.
Page 2: Schedule
Topics Covered:
Introduction to infection
General bacteriology recap
Antibiotic resistance
TED Talk: How can we solve the antibiotic resistance crisis?
Mycobacterium tuberculosis
TED Talk: What makes TB the world’s most infectious killer?
Immunocompromised patients with bacterial infections
Page 3: Introduction to Infection
Microbiology: Study of microscopic organisms or 'microbes'.
Clinical Microbiology: Focuses on organisms responsible for significant infectious diseases in humans.
Microbes Include:
Bacteria, viruses, fungi, and parasites
Fields of Study:
Bacteriology: Study of bacteria
Virology: Study of viruses
Mycology: Study of fungi
Parasitology: Study of parasites
Historical Notes:
First 'microbe' linked to disease: Trichinella spiralis (1835) causing trichinellosis.
Page 4: Dynamic Relationships
Infectious organisms are analyzed as individual agents of disease.
Emphasis on the relationship between organism and host over mere pathogen presence.
Illustrates that outcomes depend on host responses, not just the presence of microbes.
Page 5: Importance of Studying Infectious Agents
Increased prevalence of opportunistic infections among immunocompromised individuals.
Malaria is caused mainly by sporozoa plasmodium falcipurum kills 1,200 African children
Newly emerging pathogens and the re-emergence of controlled diseases are ongoing concerns.
Tropical infections are great importance and usually woefully under reported
P.falcipurim is quite temperature sensitive
Gametocytes require 10-18 days at a temp of >21 degrees to mate and mature into infectious sportozoites inside the vector
Parasites per
Notable Distribution of Pathogen Species:
Viruses and prions: 14-15%
Bacteria: 38-41%
Fungi: 22-23%
Protozoa: 4-5%
Helminths: 20%
Page 6: Past, Present, and Future
Impact of Antimicrobial Agents: Revolutionized treatments leading to disease expectations like eradication (Example: Smallpox in the 1970s).
WHO reports show significant mortality rates associated with diseases like Tuberculosis (TB) and HIV in resource-poor regions.
Emerging pathogens and antibiotic resistance are significant health threats.
Emerging pathogens- SARS-CoV-2
Resistance is emerging to many last resort antimicrobials
climate change.
Page 7: Antimicrobial Resistance
Major bacterial advantage: Ability to resist antibiotics.
Resistance mechanisms include mutation and acquisition of external genetic material, facilitating survival.
Page 8: Pathogens
Anopheles spp are reservoir for the parasite:abundant and distributed all over the globe
Efficiency of malaria transmission depends on the vector species
Pathogenic processes include establishment and reproduction of infectious agents at the host's expense.
Key factors influencing these processes:
Microbial anatomy and size
Intracellular vs. extracellular characteristics.
Page 9: Microbial Anatomy
All non-viral organisms are cellular, consisting of cells with genetic material (DNA) and cytoplasm.
Viruses, lacking cellular structures, rely on host cells for reproduction.
Although viruses have genetic material (DNA or RNA) they are not cellular, lacking cell membranes, cytoplasm and the machinery for synthesizing macromolecules, depending instead upon host cells for this process
Page 10: Micro and Macro Parasites
Microparasites (Viruses, bacteria):
Multiply to produce a very large number of progeny
Replicate within the host, can cause overwhelming infections.
Macroparasites (Worms, arthropods):
Growth; one infectious stage matures into a single reproductive stage, impacting infection levels based on parasite entry numbers.
Page 11: Living Inside or Outside Host
Pathogen interactions with the host include nutrient acquisition and adaptive life strategies.
Host exploitation distinguishes intracellular from extracellular organisms.
Page 12: Immune Response in Intracellular Pathogens
Intracellular pathogens evade host defenses; control depends on cytotoxic mechanisms.
Examples include viruses and certain bacteria residing in macrophages.
Page 13: Immune Response in Extracellular Pathogens
Extracellular pathogens freely reproduce and are subject to host defences, resulting in one of many tissue damages.
Unique challenges exist for defense against large macroparasite’s since they cannot be phagocytosed easily.
Mounting effective defence for large microparasites are concerned ,because their size often renders them insusceptible to defence mechanisms that can be used against smaller organisms
Page 14: Identification & Nomenclature
Correct identification is key for diagnosis/treatment; accomplished through various methods including genome sequencing.
Pathogens are classified into species and genus, supporting the binomial system of classification.
Protozoa, fungi, worms and arthropods, are the basic unit of classification is the species ,essentially defined as a group of organisms capable of reproducing sexually with one another
Page 15: Identifying Bacteria
Accurate treatment hinges on species identification through immunological properties, biochemical characteristics, and genetic approaches (e.g., PCR).
Identification involves examining cell wall, flagellar, and capsule antigens.
Page 16: Bacteria
Bacteria defined as single-celled prokaryotes with unique DNA organization and structures (e.g., nucleoid, plasmids).
Characteristics include ribosome presence and high metabolic diversity.
Page 17: Growth and Division
Bacterial growth rates are influenced by environmental nutrient availability with distinct growth phases: lag, log, stationary, decline.
Page 18: Tuberculosis
Overview of tuberculosis provided in Mims Medical Microbiology and Immunology.
Page 19: Introduction to Tuberculosis
Brief discussion of TB's significance as a major global health challenge.
Page 20: Mycobacterium tuberculosis
TB is a leading cause of death in resource-poor regions with a high burden of infection and mortality primarily affecting vulnerable populations.
Page 21: Mycobacterium spp.
TB spreads via inhalation of aerosols; airborne transmission facilitated by mycobacteria's resilience.
Page 22: Pathogenesis of TB - Primary
Detailed description of primary TB infection process follows inhalation exposure, macrophage engagement, and lymph node responses.
Page 23: Pathogenesis of TB - Secondary
Secondary TB can emerge from reactivation of dormant bacteria due to impaired immune systems.
Page 24: Mantoux Test
The tuberculin skin test detects T-cell responses 4-6 weeks after TB exposure, interpreted through local induration.
Page 25: Acid-Fast Test
Diagnostic support for TB includes chest radiography and Ziehl–Neelsen stain identifying acid-fast bacilli.
Page 26: Drug Treatments
TB treatment requires specific antituberculosis drugs with prolonged therapy essential; resistance issues highlighted with growing incidences of MDR-TB.
Page 27: Prevention
TB prevention strategies focus on improving social conditions, vaccinations (BCG), and chemoprophylaxis.
Page 28: Immunocompromised Host
Detailed mechanisms and effects of compromised immune systems leading to vulnerabilities against infections.
Page 29: Ways of Compromising the Host
The classification of immunodeficiencies into primary (inherited or environmental) and secondary (due to disease or treatment).
Page 30: Compromised Host Infections
Infections prevalent in immunocompromised individuals include opportunistic pathogens, highlighting risks associated with conditions like AIDS.
Page 31: Bacteria Infecting Burns Patients
Burn injuries create susceptible environments for bacterial colonization, often leading to severe infections from various pathogens.
Page 32: Summary
Instructions to review video materials in preparation for upcoming lectures on parasitic infections.
Page 33: Summary Discussion
Conclusion of the session with reflections on learned topics.