Infection, Infectious Diseases and Epidemiology Flashcards
Define Indigenous microbiota and what is another word for it.
bacteria & other microbes that are consistently associated with an animal.
another word is normal microflora
microbial associations can be classified into 2, list them and their definitions
- symbiotic: organisms that live in close nutritional relationships. required by 1 or both
- nonsymbiotic: organisms are free-living, relationship not required for survival
list the types of symbiotic microbial relationships.
- Mutualism: obligatory or dependent, both members benefits
- commensalism: one member benefits and the other is not harmed
- parasitism: one (parasite) is dependent while the other is harmed
what is Amensalism
- A type of symbiotic microbial relationship
- one symbiont is harmed by a 2nd symbiont while 2nd symbiont is neither harmed nor helped by the 1st
What is Synergism?
- a nonsymbiotic microbial relationship
- members cooperate and share nutrients
what is Antagonism?
- a nonsymbiotic microbial relatonship
- some members are inhibited or destroyed by others
what is a microbiome?
microbes that colonize a body that don’t normally cause disease
Define Resident Flora
constant population, can not be removed completely
define transient flora
consists of non-pathogenic or potentially pathogenic microbes
derived from environment
inhabit skin or mucous membrane for hrs, days or weeks
Define Microbiome
Microbes that colonize the body without normally causing disease
list the normal flora of the upper respiratory tract
- Staphylococcus spp.
- Streptococcus spp
- Streptococcus pneumoniae
- Alpha-haemolytic streptococcus spp.
- Haemophilus spp.
- Anerobes
list the normal flora of the skin
- Coryneform bacteria or “Diphtheroids”
- Cutiform bacterium
- Staphylococcus spp.
list the normal flora of the GI tract
- Enterococcus spp.
- Enterobacteriacaea
- E. Coli
- Klebsiella spp.
- Anaerobes
- Streptococcus spp.
- Streptococcus anginosus
- Lactobacillus spp.
- Candida spp.
List the normal flora of the genital tract
- Lactobacillus
- Streptococcus spp.
- Streptococcus agalactiae
What are the benefits of the normal microflora
- they make a healthy human being less susceptible to pathogens
- help stimulate immune system against pathogens
- prevent invasion and colonization of pathogens in/on the human body
- provide protection against infections on the sites of the body they are located in
- prevent pathogens from colonizing certain parts in human body
- intestinal microflora produce important vitamins (B12 & K)
- intestinal microbial flora help produces organic acids and gases (flatus) in the gut of humans and animals
- inhibit growth of pathogens in the body by producing chemical substances that antagonize the activities of invading pathogenic microbe
- knowledge on microbiota found in/on different body parts helps microbiologist be acquainted with likely infection/disease that will develop in particular body and type of microorganism to expect from culture of specimens from such body location
what are opportunistic organisms and list an example.
potentially pathogenic microbes that normally do not cause disease
Ex: Pneumocystis carinii invades the lung and causes lethal pneumonia
what are the conditions that create opportunities for opportunistic organisms?
- introduction of a member of the normal microbiota into an unusual site in body
- immune suppression
- changes in the normal microflora
- stressful conditions
explain each step in the Chain of infection
- Infectious Agent: micro-organisms that are capable of causing disease or illness
- Reservoir: place in which infections agent lives, grows and replicates
- portals of exits: ways in which infectious agent leaves the reservoir
- modes of transmission: ways in which infectious agent spreads from reservoir to susceptible host
- Portals of entry: ways In which infectious agent enters susceptible host
- susceptible host: individuals may have traits that affect their susceptibility and severity of disease
what are the 3 types of reservoirs
- human carriers
- animal reservoirs
- nonliving reservoircs
what are the portal of entry/exit for the respiratory tract?
nose & throat
what are the portal of entry/exit for the skin
hair follicles, sweat gland ducts
list the different portals of entry/exit for pathogens
- Respiratory Tract
- Nose and throat
- Skin
- hair follicles or sweat gland ducts
- Mucous membrane
- Genitourinary Tract
- Gastrointestinal tract via mouth
- Parenteral route- Blood (insects, transfusion, needles)
what are the 2 types of transmission and their definition
- Horizontal transmission: through contact, ingestion or via living agent
- Vertical transmission: through pregnant women to fetus or mother to infant during childbirth
list the different types of horizontal transmission
- direct
- skin, sexual, person to person
- indirect
- fomites, waterborne, foodborne, airborne, transfusions or injections
- vectors
Define Zoonoses and provid examples
- transfer of pathogens from animal to human host
- Ex: rabies, plague, Brucellosis, Tularemia
what are the modes of transmission for virus?
- droplet nuclei through direct contact, indirect contact
- direct contact
- aerosolized viral particles
What are TORCH infections?
group of congenitally acquired infections that cause morbidity and mortality in neonates. they are acquired by mother and passed through placenta or during child birth
T (Toxoplasmosis)
O (Other Agents)
R (Rubella)
C (Cytomegalovirus)
H (Herpes Simplex Virus)
what are the portals of exit in humans (5)?
- Alimentary
- Genitourinary tract
- Respiratory
- Skin
- Transplacental
portal of exit usually corresponds to site where pathogen is localized
list the 7 stages of infection
- transmission from external source into portal of entry
- evasion of primary host defenses (skin or stomach acid)
- Adherence to mucous membrane
- colonization by growth of bacteria at site of adherence
- disease symptoms cause by toxin productions or invasion accompanied with inflammation
- host responses, both nonspecific and specific (during steps 3-5)
- progression or resolution of disease
Define Pathogenicity
the ability to cause disease
define virulence
measurement of pathogenicity
Define Pathogenesis
the process of causing disease
what are determinants of virulence
the biochemical, genetic or structural features that enable it to produce disease in a host
Pathogenesis is a multi-factorial process that depends on (3);
- immune status of the host
- nature of species or strain (virulence)
- number of organisms in initial exposure
Define Commensal
a microorganism living in humans and deriving their sustenance from surface cells of the body w/o doing harm
ID50
Infectious Dose required to cause disease in 50% of inoculated test animals
LD50
Letha Dose of microbes toxin that will kill 50% of experimentally inoculated test animals
list the virulence factors
- Adhesion
- invasion
- competition for iron and nutrients
- resistance of host immunity
- secretion of toxins
what are the steps involved in pathogenesis of bacteria
- transmission
- colonization
- adhesion
- invasion
- survival in the host
- tissue injury
define colonization
occurs when any one or more species populates an area
define Invasion
ability for microorganisms to enter host tissue, multiply there, and spread to other tissues
Hyaluronidase, and what bacteria produce it
bacterial invasion
- breaks down hyaluronic acid which is an interstitial cement for connective tissue
- produced by streptococci, staphylococci & clostridia
Collagenase, and what bacteria produce it
bacterial invasin
- breaks down collagen which is frame work of muscle. facilitates gas gangrene
- produced by clostridium histolyticum and clostridium perfringens
Neuraminidase, and what bacteria produce it
bacteria invasin
- breaks down neuraminic acid which is a intercellular cement of epithelial cells in intestinal mucous
- produced by vibrio cholerae and shigella
streptokinase and staphylokinase, what bacteria produce it
- bacterial invasin
- kinase enzyme breaks down inactive plasminogen→plasmin which digests fibrin and prevents blood from clotting
- produced by streptococci and staphylococci
Beta-lactamases, and what bacteria produce
- bacterial invasin
- produced by gram+ and gram- bacteria
- group of enzymes that degrade or hydrolyze antibiotics (esp. those with beta-lactum ring as penicillin)
explain the purpose of siderophores and how they function
- they have high affinity for ferric iron
- in cases where there is limited iron conditions siderophores are released by microbe the siderophores bind ferric iron in the cytosol to form iron-siderophore complex. the ferric iron is then reduced to ferrous iron and becomes accessible to microorganisms
what are the physical structures that contribute to virulence?
- capsules
- flagella
- pili
- spores
- toxin
- siderophores
define toxigenicity
organisms ability to produce toxins
name the 2 types of toxins bacteria can produce
- endotoxins
- exotoxins
define LAL and its purpose, and where is it obtained
- Limulus Amebocyte Lysate
- an endotoxin test that is used in vitro to detect presence/concentration of gram- bacteria endotoxins in drugs and biological products
- obtained from horseshoe crab
what are Pathogenicity Islands?
- mobile gene elements that can be transmitted from one bacteria to another
- contain gene clusters that mediate virulence in pathogenic bacteria. they are obtained from other pathogenic bacteria through horizontal gene transfer
define Inoculum size
of invading pathogenic microorganisms that is sufficient enough to initiate an infectious disease process in a susceptible host
what is the period of incubation
the time between the time of contact &/or entry of agent and onset of illness
list the 5 stages for the periods of disease (remember the stages that follow exposure and infection)
- incubation
- prodromal
- illness
- decline
- convalescence periods
explain the difference between signs and symptoms
- Signs are indicative of what the doctor sees
- symptoms are conditions and characters which the person feels
- signs are objective, visible, quantifiable and can be verified
- symptoms are subjective, not visible, and what the person feels
Define Syndrome and provide an example
group of symptoms and signs that collectively characterize a particular disease or conditions
- Ex: AIDS, characterized by malaise, loss of certain WBC, blood loss, diarhea, pneumonia, toxoplasmosis, TB
define bacteremia
bacteria found in the blood
define pyemia
bacteremia involving pyogen (pus forming bacteria)
define viremia
virus found in the blood
define toxemia
toxins found in blood
define septicemia
bacteria that are both present and multiply in the blood
pts with septicemia described as septic and can lead to septic shock (life-threatening decrease in blood pressure)
infection can be described as (3) (think of location)
- local infection: confined to small area, typically near the portal of entry
- focal infection: localized pathogen or the toxins it produces can spread to secondary location
- systemic infection: infection that is disseminated throughout entire body
Exogenous
encountered in environment
endogenous
encounter in or on body
organisms present in the skin can cause disease if they go into deeper tissues
define iatrogenic and when can they be acquired
a disease that is contracted as a result of medical procedure
- wound treatment, catheterization, surgery if wound or surgical site becomes contaminated
define nosocomial
disease that is acquired in a hospital setting
