Chapter 11 Flashcards
the sum total of all microbes found on and in a normal human that is critically important to the health and functioning of its host organism
human microbiome
rapidly lost microbes in the human microbiome
transients
any deviation from health, as when the effects of microbial infection damage or disrupt tissues and organs
disease
about how many protein-encoding genes do human cells contain?
-found from research in the Human Microbiome Project (HMP)
21,000
What are some more recently and newly discovered regions of the human body that harbor normal microbiota?
lungs (lower resp tract)
bladder and urine
breast and breast milk
amniotic fluid and fetus
What are some recently discovered sites in which DNA from microbiota has been detected?
brain
blood stream
relationship in which microorganisms compete for survival in a common environment by taking actions that inhibit or destroy another organism
ie. between normal microbiota and intruders
microbial antagonism
True or False
The uterus and its contents are sterile during embryonic and fetal development
False, and the placenta itself also harbors a small but significant array of bacteria
where do babies get a microbiome?
the womb, the vaginal canal or during c section, breast milk, caregivers, environment
the vaginas of healthy women of child bearing age contain a variety of bacteria, but are especially rich in __________ bacteria, which are capable of digesting milk.
Lactobacillus
sites previously known to harbor normal bacteria
skin and adjacent mucous membranes upper resp tract gastro tract including mouth outer portion of urethra external genitalia vagina eternal ear canal external eye (lids, conjunctiva)
*now know in lungs, bladder, breast/breastmilk, amniotic fluids/fetus, lungs
a microbe whose relationship with its host is parasitic and results in infection and disease
pathogen
true (primary) pathogens
capable of causing disease in healthy persons with a normal immune defenses; generally associated with a specific, recognizable disease, which may vary in severity from mold (colds) to severe (malaria) to fatal (rabies).
Opportunistic pathogens
cause disease when the host’s defenses are compromised or when the pathogens become established in a part of the body that is not natural to them.
; Pseudomonas species and Candida albicans
in infection, the relative capacity of a pathogen to invade and harm host cells
virulence
the term virulence and _________ are often used interchangeably
pathogenicity
__________ is the accurate term for describing the degree of pathogenicity
virulence
what two factors is virulence determined by
its ability to
- establish itself in the host
- cause damage
to cause damage, microbes produce ______ or induce a host response that is actually injurious to the host
toxins
what must microbes do to establish themselves in a host
enter the host
attach firmly to host tissues
negotiate the microbiome
survive host defenses
any characteristic or structure of the microbe that contributes to the preceding activities is called a __________
virulence factor
a set of rules for determining the cause of an unknown infectious condition
Koch’s Postulates
involving multiple distinct microorganisms
polymicrobial
what is the most common portal of entry?
respiratory tract
route of entry for an infectious agent; typically a cutaneous or membranous route
portal of entry
organisms coming from outside the body
exogenous
Portal of Entry: Skin
examples of organism/disease and how access is gained
organisms: Staphylococcus aureus, Streptococcus pyogenes, Clostridium tetani, Herpes simplex (type 1), Helminth worms, viruses, rickettsias, protozoa (.e malaria, West Nile virus), Haemophilus aegyptius, Chlamydia trachomatis, Neisseria gonorrhoeae
access: nicks, abrasions, areas of broken skin, mucous membranes of the lips, burrow through the skin, insect bites, conjunctiva of the eye
Portal of Entry: GI tract
organisms: Salmonella, Shigella, Vibrio, E. coli, poliovirus, Hep A., echovirus, rotavirus, enteric protozoans (Giardia lamblia, Entamoeba histolytica
access: drinking contaminated foods/fluids, fomites (inanimate objects contaminated with the infectious organism)
Portal of Entry: Resp tract
organisms: bacteria causing meningitis, influenza, measles, mumps, rubella, chicken pox, common cold, Streptococcus pneumoniae, Klebsiella, Mycoplasma, Cryptococcus, Pneumocystis, Mycobacterium tuberculosis, Histoplasma
access: via inhaling of offending organism
Portal of Entry: Urogenital Tract
organism: HIV, Trichomonas, Hep B., syphilis, Treponema pallidum, Neisseria gonorrhea, Chlamydia trachomatis, herpes, genital warts
access: skin/mucosa of penis, external genitalia, vagina/cervix, urethra; may enter through an unbroken surface of through a cut or abrasion
Infectious dose
the minimum number of microbes required to cause an infection
Infectious dose for typhoid fever
10,000 bacteria
Infectious dose for Cholera
1,000,000,000 bacteria
infectious dose for Coxiella burnetii (Q fever)
a single cell
process by which microbes gain a more stable foothold on host tissues at the portal of entry; dependent on binding between specific molecules on both the host and pathogen (limits the types of cells pathogens can bind to)
Adhesion (step two)
Adhesion:
attach most often by mechanisms such as fimbriae (pili), surface proteins, and adhesive slimes or capsules
Bacterial, fungal, and protozoal pathogens
adhesion:
attach by means of specialized receptors
viruses
adhesion:
mechanically fastened to the portal of entry by suckers, barbs, and hooks.
Parasitic worms
Microbial Infections: Step 3
surviving host infections
;microbes that are not established in a normal biota are likely to encounter resistance from host defenses ESPECIALLY from phagocytes (a WBC)
used by some pathogens to avoid phagocytes during step 3 of infection
Antiphagocytic factors
species of both Streptococcus and Staphylococcus produce __________, substances that are toxic to white blood cells.
leukocidins
some micros secrete an extracellular surface layer (slime or capsule) which does what?
this makes it difficult for phagocytes to engulf them
what is step four of infection?
Causing Disease
structures or capabilities that allow a pathogen to cause infection in a host
virulence factors
what are the three major ways that microorganisms damage their host?
- directly through the action of enzymes or toxins (both endo and exotoxins)
- indirectly by inducing the host’s defenses to respond excessively or inappropriately
- epigenetic changes made to host cells by microbes
an extracellular enzyme chiefly for hydrolysis of nutrient macromolecules that are otherwise impervious to the cell membrane.
; functions in saprobic decomposition of organic debris and can be a factor in invasiveness of pathogens
-> break down and inflict damage on tissues
exoenzyme
enzyme that digests the protective coating on mucous membranes and is a factor in amoebic dysentery
mucinase
enzyme which digests hyaluronic acid, the substance that cements animal cells together (important virulence factor in staphylococci, clostridia, streptococci, and pneumococci)
hyaluronidase
enzyme produced by pathogenic staphylococci, causing clotting of blood or plasma
Coagulase
dissolves fibrin clots and assists in the invasion of damaged tissues
bacterial kinases
specific chemical product of microbes that is poisonous to other organisms
toxin
lyse red blood cells
hemotoxins
when red blood cells burst and release hemoglobin pigment
hemolyze
proteins with strong specificity for a target cell and extremely powerful, sometimes deadly, effects
; is a bacterial toxin, and generally affect cells by damaging cell membranes and causing lysis or by disrupting intracellular function
exotoxins
class of bacterial exotoxin that disrupts the cell membrane of red blood cells ; causes red blood cells to hemolyze (burst and release hemoglobin pigment)
hemolysins
what hemolysins (bacterial exotoxin) increase pathogenicity?
streptolysins (or Streptococcus pyogenes) and the alpha and beta toxins of Staphylococcus aureus.
a chemical called lipopolysaccharide (LPS) which is a part of the outer membrane of gram negative cell walls
;gram negative bacteria shed LPS molecules into tissues or into the circulation
endotoxins
lipopolysaccharide is an endotoxin present in what bacterial outer cell membrane?
gram negative bacteria
how does endotoxin differ from exotoxins?
endotoxin has a variety of systemic effects on tissues and organs, and can cause things like fever, inflammation, hemorrhage, and diarrhea.
*Blood infections by gram-negative bacteria such as Salmonella, Shigella, Neisseria meningitidis, and E. coli and particularly dangerous and can lead to fatal endotoxic shock.
exotoxins are given off by ________, endotoxins are given off by gram-neg ___ ____.
- cells
2. cell walls
exotoxins have highly ______ targets, endotoxins have more ________ effects.
- specific
2. generalized
it is probably the case that more microbial diseases are the result of _____ damage, or the host’s excessive or inappropriate response to a microorganism.
indirect
pathogenicity is not always a trait inherent in microorganisms, but is really a consequence of what?
of the interplay between microbe and host
Epigenetic changes in host cells
microbes have been shown to shut down or activate regions of DNA in the host cell, via epigenetic processes
what are some examples of epigenetic processes?
binding to host cell histones, binding to small RNAs used for the silencing of genes, binding to chromatin itself, etc.
-> these can harm the host cell or change its function in some way that favors persistence of the microbes in or on it.
when there is a decrease in a host’s ability to mount an immune defense
immunocompromised
opportunistic pathogens
microbes that take advantage of immunocompromised hosts
infection that is in a location different than the initial infection (goes from local to other tissues)
ie. periodontal infections leading to cardiovascular consequences
focal infection
infections that are only in one location
ie. boils, warts, fungal skin infections
localized infection
infection that spreads to several sites and tissue fluids via bloodstream, nerves, cerebrospinal fluid
ie. mumps, rubella, AIDS, anthrax, chickenpox, typhoid, syphilis
systemic infection
several agents establish themselves simultaneously at the infection site
ie. human bite infections, wound infections, gas gangrene
mixed/polymicrobial infection
the initial infection
ie. can be any infection
primary infection
a second infection caused by a different microbe, which complicates a primary infection; often a result of lowered host immune defenses
ie. influenza complicated by pneumonia or common cold complicated by bacterial otitis media
secondary infection
infection comes on rapidly, with severe but short-lived effects
ie. influenza
acute infection
infection that progresses and persists over a long period of time
ie. HIV
chronic infection
any objective evidence of disease as noted by an observer
sign
subjective evidence of a disease as sensed by a patient
symptom
in general, ____ are more precise than _______, though both can have the same underlying cause.
Options: signs, symptoms
- Signs
2. Symptoms
when a disease can be identified or defined by a certain complex of signs and symptoms, it is termed what?
syndrome
the earliest symptoms of disease usually come from the activation of the body defense called __________.
inflammation
what are some signs and symptoms of inflammation?
signs:
- edema
- granulomas (solid mass or nodule of inflammatory tissue containing modified macrophages and lymphocytes) and abscesses (inflamed, fibrous lesion enclosing a core of pus)
- walled off collections of inflammatory cells and microbes in the tissues
- lymphadenitis (swollen lymph nodes)
symptoms:
- fever
- pain
- soreness
- swelling
changes in the number of circulating ___________, as determined by special counts, are considered to be signs of possible infection.
white blood cells
term for an increase in the level of white blood cells
leukocytosis
term for decrease in the number of white blood cells
leukopenia
clinical term for blood infection, which refers to a general state in which microorganisms are multiplying in the blood and are present in large number.
septicemia
refers to when small numbers of bacteria are found in the blood, but not necessarily multiplying
Bacteremia
refers to when small numbers of viruses are found in the blood, but not necessarily multiplying
viremia
what is step five of infection?
Vacating the Host- Portals of Exit
What are the five steps of infection?
- Becoming Established-Portals of Entry
- Becoming Established-Attaching to the Host and Interacting with the Microbiome
- Becoming Established-Surviving Host Defenses
- Causing Disease
- Vacating the Host-Portal of Exit
route through which a pathogen departs from the host organism
portal of exit
what are the ways in which a pathogen is shed or released from the body?
excretion, secretion, discharge, or sloughed
in many cases the portal of exit is the _____ as the portal of entry, but some pathogens use a different route.
same
the state of being inactive; the infectious agent retreats into a dormant state called _____.
ex: a _______ virus or _______ infection
Latency
Latent
what can a microbe do throughout a latent state?
the microbe can periodically become active and produce a recurrent disease
ie. The viral agents of Hep B., Herpes zoster, AIDS, herpes simplex, and Epstein-Barr can persist in the host for long periods
term for a morbid complication that follows a disease; such as permanent damage to tissues or organs
ie. Strep throat can lead to rheumatic heart disease
sequela
the period from the initial contact with an infectious agent to the appearance of the first symptoms
; during this period the agent is multiplying at the portal of entry but has not yet caused enough damage to elicit sx
incubation period
the majority of infections have incubation periods ranging between
2 and 30 days
a short period of mild sx occurring at the end of the period of incubation -> indicates the onset of a disease; about 1-2 days
ie. headache, muscle aches, fatigue, upset stomach, general malaise
prodromal stage
third phase of infection where the infectious agent multiplies at high levels, exhibits the greatest virulence, and becomes well established in its target tissue
; often marked by fever and other prominent and more specific signs and symptoms like cough, rashes, diarrhea, severe pain, jaundice, loss of muscle control, but depends on the infection
-> extremely variable length of this period
Acute Phase
fourth phase of infection where the patient begins to respond to the infection and symptoms decline (sometimes dramatically or slowly); the patient’s health begins to gradually return
Convalescence (recovery)
fifth phase of infection that only some infections have, in which the organism lingers for months, years, or indefinitely after the patient is completely well or the organism is gone by sx continue
ie. typhoid fever or chronic Lyme Disease
Continuation phase
many microbes are released primarily in the _____ phase, but others can be transmitted during all of these phases
acute
A patient has been diagnosed with E. coli septicemia. Which of the following characteristics are associated with endotoxins? Select all that apply.
a. toxicity in minimal concentration
b. gram-negative bacteria
c. presence of fever
d. protein composition
e. released by cells during lysis
b, c, e
11.2 Outcome:
differentiate between a microbe’s pathogenicity and its virulence
pathogenicity is the ability of a pathogen to cause disease
virulence is the ability of a pathogen or microbe to infect or damage a host
11.2 Outcome
List the steps a microbe has to take to get to the point where it can cause disease
- Becoming Established - Portal of Entry
- Attaching to Host (adhesion) and Interacting with Microbiome
- Surviving Host Defenses
- Causing Disease
- Vacating Host - Portal of Exit
Microbial hyaluronidase, coagulase, and streptokinase are examples of __________
exoenzymes
11.2 Outcome
List several portals or entry and exit
entry: mucous membranes, nicks on the skin, gastrointestinal tract, respiratory tract, urogenital tract,
exit: blood, feces, urine, saliva, skin cells, respiratory tract
11.2 Outcome
Explain the significance of polymicrobial infections
they are infections consisting of multiple microbes, which changes the need for antibiotics, and presents the risk of using an antibiotic that does not adequately eliminate all microbes causing infection (resistance)
11.2 Outcome
Define infectious dose and explain its role in establishing infection
it is the minimum number of microbes requires for an inoculating dose to cause an infection
11.2 Outcome
Describe three ways microbes cause tissue damage
- directly through the action of enzymes
- directly through the action of toxins (endo or exo)
- indirectly through inducing the host’s immune system to respond excessively or inappropriately
- EPIGENETIC CHANGES
11.2 Outcome
compare and contrast major characteristics of endotoxins and exotoxins
exotoxins:
- produced by live bacteria that are gram pos and neg
- specific target
- protein composition
- often has enzymatic activity
endotoxins:
- predominantly a part of the cell wall of gram neg bacteria
- systemic effects
- lipopolysaccharide composition
11.2 outcome
provide a definition of virulence factors
structures or capabilities that allow a pathogen to cause infection in a host
