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What is the microbiome
"The microbiome refers to bacteria on us, in us, and around us, maintaining a balanced microbial community that can shift to a disease state (dysbiosis) if disrupted."
What are virulence factors
"Virulence factors are properties that allow microorganisms to become pathogenic and cause harm to the host."
How can microorganisms be used to treat diseases
"Microorganisms, such as probiotics, can treat diseases by maintaining the gut microbiota, helping restore balance and prevent dysbiosis."
What is mutualism in symbiotic associations
"Mutualism is a symbiotic relationship where both organisms rely on and are dependent on each other for their metabolic needs."
What is commensalism in symbiotic associations
"Commensalism is a symbiotic relationship where the host provides food or shelter, benefiting another organism, which may return the favor without dependency."
What is parasitism in symbiotic associations
"Parasitism is a symbiotic relationship where one organism harms the host through its presence and activity; these relationships can dynamically switch to other types."
What is the progression from asymptomatic carriage to disease
"The progression is: Asymptomatic Carriage (organisms present without symptoms) → Colonisation (organisms establish on host) → Infection (organisms invade) → Disease (harmful symptoms manifest)."
Why is the skin an inhospitable microbiome for organisms
Skin makes it challenging for microbial growth:
Dry
Sheds hair
Has an acidic pH
Lacks food (only keratinized regions provide nutrients)
How can Staphylococcus epidermidis shift from commensal to parasite
"Staphylococcus epidermidis shifts from commensal to parasitic when it enters a surgical wound, changing its anatomical positioning and causing disease."
What is the microbiome of the upper respiratory tract
"The upper respiratory tract (nose, oropharynx) has microflora; Neisseria meningitidis can colonize, saliva with lysozymes removes organisms, and virulence factors enable attachment to gingivitis gaps and biofilm formation."
How do phagocytes protect the lungs in the respiratory microbiome
"Phagocytes eat organisms entering the lungs, while mucus clears them, preventing infection in the lower respiratory tract."
How does pH affect the microbiome of the GI tract
"The acidic pH of the stomach kills most bacteria; as pH rises along the GI tract, more bacteria grow, with the highest numbers in the large intestine and colon, where microbes can migrate to the appendix causing appendicitis."
What is the role of bacteria in the GU tract microbiome
"In the GU tract (urethra, rectum, vagina), Lactobacilli in the vagina feed on glycogen, producing lactic acid to lower pH, creating a safe environment for childbirth and preventing uterine infections that could lead to premature birth or miscarriage."
What are Koch's postulates
"1. The organism must be found in all hosts with the disease. 2. It must be isolated in pure culture. 3. It must produce the same disease when reintroduced into a healthy host. 4. It must be re-isolated in pure culture."
What are the problems with Koch's postulates
"Problems include: organisms may only grow in lab conditions (unrealistic), genetic diversity, shifts from virulent to avirulent, and ethical issues with deliberately causing disease in humans."
What is the molecular version of Koch's postulates
"1. Genes (or products) have pathogenic potential. 2. Genes are in pathogenic strains, not avirulent ones. 3. Disrupting the gene reduces virulence. 4. Cloning the gene transforms avirulent strains to virulent. 5. The gene is expressed during infection. 6. The gene product elicits an immune response."
What are the methods of pathogen transmissibility
"Direct airborne contact (e.g., coughing), indirect airborne contact (e.g., wind), direct contact (e.g., touching), contact via inanimate objects (e.g., handrails, contaminated food), and vectors (e.g., mosquitoes causing malaria)."
How do pathogens adhere to and colonize the host
"Pathogens use pili for transient adhesion to membranes, easily breaking off to evade immune response, and produce mucous slime to attach and grow on surfaces."
What occurs during colonization of mucosal surfaces
"Enzymes break down epithelial tissues, aiding pathogen colonization on mucosal surfaces."
How do pathogens invade the host
"Pathogens invade by hiding from immune detection, rearranging the host cell cytoskeleton, and forcing uptake into the cell."
How do pathogens grow and multiply in the host
"Pathogens use siderophores (catechols/hydroxamates) to chelate free iron ( scarce in natural environments) and exotoxins (secreted proteins from vegetative cells) to release bound iron by breaking down tissues."
How do pathogens evade the complement pathway
"Pathogens evade the complement pathway, part of the immune response, using anti-phagocytic strategies to avoid destruction."
What is opsonization in immune evasion
"Opsonization tags pathogens for phagocytosis, but pathogens employ anti-phagocytic strategies to resist being engulfed and destroyed."
What are nosocomial infections
"Nosocomial infections are hospital-acquired diseases caused by pathogens present in healthcare settings."
