WEEK 3: HOST-MICRO CONTROL Flashcards
Biological relationship between two or more organisms where both benefit from one another.
Symbiosis (Mutualism)
Organism benefits but there is no beneficial or harmful effects to the host
Commensalism
The microbe benefit at the expense of the
other (host).
Parasitism
Commonly found in body sites of healthy persons.
Microbial Flora
Microorganisms that colonize an area for months or years.
Resident microbial flora
➢ Present at a site temporarily, eliminated by host immune defense / competition with
resident flora.
➢ Carrier state may be acute (S. aureus) or
chronic (S. typhi)
Transient microbial flora
E.g: Diptheroids in moist areas
Nutritional and Environmental factors
E.g: P. acnes in hair follicles
Resistance to bile, lysozymes or fatty acids
E.g: Lactobacillusin Female genital tract
pH
E.g: Obligate anaerobes in the colon
Oxidation-reduction potential
Mouth, nasopharynx, oropharynx
and larynx
Upper Respiratory Tract
Viridans Strep. and Gram (-) anaerobes
Mouth
Diplococci and Diphtheroids * Oropharynx → Gram (-) anaerobes and Diphtheroids
Nose and Nasopharynx
Anaerobes makes up 90% of the microbial
flora
➢ Esophagus, stomach, small
intestine, and colon
Respiratory Tract
➢ G(+) staph and Enterococcus
➢ Anaerobic G(+) cocci and spore forming bacilli
➢ Enterobacteriaceae
Respiratory Tract
Example:
➢ Lactobacillus acidophilus
➢ Anaerobic Sporeformers
➢ G(+) cocci / Diphtheroids
Gastrointestinal Tract
Gastrointestinal Tract
➢ Sites – urethra and vagina
➢ Sterile – Kidneys, bladder and fallopian
tubes
➢ Activates or primes the immune system (e.g. cell mediated immunity)
➢ Blocks the colonization of extraneous pathogens.
Microbial Flora a in the Host Defense Against Infectious Disease
➢ Cause disease when their habitat is damaged, disturbed or changed by trauma or;
➢ When the host’s immune system is weakened or compromised
Microbial Flora in the Pathogenesis Infectious Disease
Is the ability of a microbe to produce disease in a susceptible individual.
Pathogenicity
➢ Organisms recognize to cause disease in healthy immune-competent individuals.
➢ B. anthracis and Y. pestis
True Pathogen
➢ Organisms that cause opportunistic or iatrogenic infections (medical treatment or procedures)
➢ H. influenzae and S. epidermidis
Opportunistic Pathogen
Is the relative ability of a microorganism to cause disease or the degree of pathogenicity
Virulence
➢ Allows pathogens to evade or overcome host defenses and cause disease
➢ E.g. Fimbriae, Capsules and Toxins
Microbial Virulence Factors
