Lecture 12: Medical Microbiology Flashcards by Zoe Phillips

_______: The collection of all the microorganisms living in association with the human
body (microflora, microbiota)

human microbiome

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T/F: microorganisms outnumber our human cells, and have wayyyy more genes

true!
outnumber us 10^14>10^13
20000<20000000

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T/F: Colonization begins immediately after birth

true!

colonized through vaginal canal and breastfeeding

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T/F: Every exposed area in/on the surfaces of the body are colonized with bacteria

true
skin and mucous membranes

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T/F: Internal tissues should be free of microbes

true

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what are some examples of internal tissues that should be free of microbes?

peritoneum, pericardium, pleura, blood, muscles, organs

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what is the beneficial product that E. coli produces for us?

vitamin K in our colon

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T/F: most bacteria in/on our body are harmless commensals (that can always turn bad) and many contribute to our health

true

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T/F: Different areas of the skin vary in chemical composition and moisture
content

true

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what are the three different microenvironments of the skin?

dry, moist, sebaceous

each have different microbial populations

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_______ (skin microbiota):
Forearms, hands
* High numbers of Betaproteobacteria
* Known from 16 rRNA genes
* Rarely cultured and their role isn’t known
* Second highest is corynebacteria
* Most are harmless commensals
* Some may cause skin infections
* Ex) Corynebacterium diphtheriae
* Can cause non-healing ulcers of the skin: cutaneous diphtheria

dry skin

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where do we have high numbers of Betaproteobacteria

also corynebacteria

dry skin

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______ (skin microbiota):
Armpits, nostrils
* High numbers of corynebacteria and staphylococci
* Most are harmless commensals
* Ex) Staphylococcus epidermidis
* Most frequently isolated from skin
* Some are important pathogens
* Ex) Staphylococcus aureus
* Cause of boils, abscesses, wound infections

moist skin

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where are there high numbers of corynebacteria and staphylococci

moist skin
armpits and nostrils

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_____ (skin microbiota):
Sebaceous skin
* Oily skin around the nose, on the upper chest and back
* High numbers of propionibacteria
* Anaerobic Actinobacteria that produce propionic acid as an end-product of
fermentation
* Ex) Propionibacterium acnes
* Lives in hair follicles, and eats oil secreted by skin (sebum)
* Overgrowth can trigger inflammation
* Inflammatory acne

sebaceous skin

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where do we have high numbers of propionibacteria (species: acne)

on our sebaceous skin (oily skin)

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_____ are anaerobic actinobacteria that produce propionic acid as an end-product of fermentation

propionibacteria

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_______ has antimicrobial enzymes:
* Lysozyme
* Lactoperoxidase
* Catalyzes production of superoxide radicals O2
-
* Oxidative damage to invading microbes

Saliva

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_______: Catalyzes production of superoxide radicals O2-
* Oxidative damage to invading microbes

lactoperoxidase

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The mouth is home to a complex microbial community including
_________

aerobes and anaerobes

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______ mucosa:
* Aerobic
* Lives on mucous membranes like the tongue

Neisseria mucosa

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_________:
* Aerotolerant anaerobe
* Produces a sticky dextran slime layer that lets it
stick to surfaces
* Forms biofilms in crevices around the teeth
* Produces lactic acid as an end-product of
fermentation
* Degrades tooth enamel
* Dental carries (cavities)
* Can lead to inflammation along the gum line:
* Gingivitis

Streptococcus mutans

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Low pH and proteolytic enzymes make the ______ inhospitable to most
microbes
* Some bacteria do colonize the _______

stomach

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_________: Cause of stomach ulcers
* Colonizes surface of the mucous membrane
* Membrane is protected from stomach acids by mucous
* Has a number of virulence factors:
* Urease neutralizes surrounding acidity
* Exotoxin: kills cells of the mucous membrane
* Endotoxin: triggers an inflammatory response
* Treated with antibiotics – tetracycline

helicobacter pylori

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helicobacter pylori produce both exo- and endo-toxin... what do they both do?

exotoxin: kills cells of the mucous membrane Endotoxin: triggers an inflammatory response

because the helicobacter pylori produces endotoxin it must be...

a gram negative

helicobacter pylori produces ____, which neutralizes the surrounding pH to 7, which degrades the bicarbonate/mucous wall of the stomach that protects membrane from stomach acid.... causing stomach ulcers (considered a carcinogen!)

urease

______: Area of rapidly changing pH * As pH becomes slightly alkaline the quantity and variety of bacteria found in the gI tract substantially increases

small intestine

T/F: As pH becomes slightly alkaline the quantity and variety of bacteria found in the gI tract substantially increases

true! more types can survive in higher pH

_______: * Genus of Gram positive lactic acid bacteria * Opportunistic pathogen * Frequent cause of nosocomial infections * Example: blood borne infection * Develop antibiotic resistance readily * Vancomycin resistant ____ * Spread resistance genes on to other Gram positive bacteria * Horizontal gene transfer

Enterococcus

what does horizontal gene transfer mean?

genes transfer buddy-buddy, instead of passing down through daughter cells

_______: pH is neutral * Environment is anoxic * Enormous number of microbes ~ 10^11 cells/g of feces * Mostly anaerobes and facultative aerobes

large intestine

why are most of the bacteria in the large intestine anaerobes/facultative aerobes?

because oxygen is super lucrative! only a little bit even makes it through, so then its used super fast!!

______: Most cultured bacterium from feces * Indicator of fecal contamination * Most strains are non-pathogenic * May stimulate the immune system * Produce vitamin K

E. coli

T/F: 16S rRNA gene sequences reveal that E. coli probably makes up < 1% of bacteria in the large intestine

true

Largest group of bacteria in large intestine are strict anaerobes from the genera _______

Bacteroides and Clostridium

explain how high numbers of methanogens in the gut have led to obesity (mouse studies)

Studies compared normal mice with germ free mice: * Germ free mice had 40% less body fat Inoculated germ free mice with microbes from healthy mouse intestines * Inoculated mice quickly gained weight Compared the microbiomes of normal weight mice to genetically obese mice * Genetically obese mice had fewer Bacteroidetes, more Firmicutes and way more methanogens * Suggested that methanogens use up H2 which promotes bacterial fermentation * Bacterial fermentation makes nutrients available to the host

which bacteria are more present in lean mice? less?

more: bacteroidetes less: firmicutes, methanogens

which bacteria are more present in obese mice? less?

more: firmicutes, methanogens less: bacteroidetes

how does the presence of methanogens affect obesity?

they use up H2 which promotes bacterial fermentation... which makes more nutrients available for absorption... increases caloric intake

T/F: Changing the microbiota of the large intestine can affect human health

true! if antibiotics are taken and normal flora is wiped out, opportunistic pathogens can take over

what happens with Antibiotic associated colitis?

Clostridium difficile grows * Inflammation of the colon results Treatment: * Further antibiotics * Probiotics * “Transpoosition”

______: Home to a variety of bacteria including Staphylococci, Streptococci and Corynebacteria * Some people harbor pathogens among their normal microflora * Carriers * Ex. Staphylococcus aureus

upper respiratory tract

________ * No resident microflora * Mucous, lysozyme, ciliated cells, Secretory IgA, alveolar macrophages

Lower respiratory tract

what three types of bacteria do we have in our upper respiratory tract?

staphylococci streptococci corynebacteria

______: kidneys, bladder * Normally free of microorganisms (should be mostly sterile)

Upper urinary tract

Some members of the normal microbiota can act as opportunistic pathogens when transferred to urinary tract... like?

E. coli most common pathogen that causes UTIs

the ______ in the reproductive/urinary tract is home to some Gram neg. bacteria

urethra

why are men less likely to get UTI's compared to women?

their anatomy! much harder for bacteria to survive when urine is constantly flushing them out plus urinary tract is so much further from rectum

______ in the vagina produces lactic acid from glycogen * Lowers pH and prevents growth of other microbes (kills bacteria and STIs)

Lactobacillus acidophilus

T/F: If normal microbiota is disturbed secondary to a course of antibiotic therapy * Yeasts can overgrow and cause yeast infections

true! because yeasts are eukaryotic they aren't targeted by antibiotics, opportunistic growth!

______: growth of microbes that are not normally present in the host (regardless of whether or not the host is harmed)

Infection

______: damage or injury that impairs regular host functions

Disease

______: a microbe that is able to cause disease

Pathogen

________: a microbe that causes disease only in the absence of normal host resistance

Opportunistic pathogen

Streptococcus pneumoniae and E. coli are both ______

Opportunistic pathogens

________: the ability to cause disease

Pathogenicity

_______: the severity of the disease that is caused

Virulence

whats the LD50 value?

Number of pathogenic cells or dose of a toxin that will cause death in 50% of inoculated animals

if the LD50 value is lower is it more or less virulent?

more virulent... less cells needed to cause 50% deaths

_______: the process by which a disease develops

Pathogenesis steps that lead to an infection and tissue damage

_______: genetically encoded traits that contribute to a pathogen’s ability to cause disease

Virulence factors

______: The ability of a pathogen to stick to a surface and begin colonization

adherence

what are two non-covalent adherence factors?

capsules and slime layers

_______ uses slime layer to stick to teeth and form a biofilm

Streptococcus mutans

______ uses capsule to stick to cells in the lungs

Streptococcus pneumoniae

how do capsules protect cells from phagocytes?

phagocyte can't recognize bacteria in capsule, can't destroy it

what is the other adherence factor?

adhesins

_____: specific surface molecules that allow selective adherence to particular cell types

Adhesins

Strains of enterotoxigenic E.coli produce _____ allowing specific adherence to enterocytes in the intestine (adhesin)

fimbriae

Neisseria gonorrhoeae produces _____ that allow it to attach to mucosal epithelial cells (adhesin)

fimbriae

how does neisseria gonorrhoeae bring itself closer to enterocyte membrane?

retracts its fimbriae, then opas proteins can specifically attach to certain receptors on the host cell

T/F: Some pathogens can colonize and grow on the surface of tissues, others need to invade tissue

true

______: the ability of a pathogen to enter into host cells or spread through tissues

Invasiveness

what are some virulence factors that promote invasiveness?

siderophores exoenzymes invasins

what are siderophores?

iron binding molecules * Host proteins transferrin and lactoferrin sequester iron, making it unavailable for microorganisms * Limit the growth of invaders * Siderophores rip iron out of tissues to be used by bacteria (competes with us for growth!)

why is bacteria that are invasive so bad?

they're no longer localized!! can't target them as efficiently

what are exoenzymes?

proteins that are excreted by bacteria to degrade host tissues

what are the five types of exoenzymes?

hyaluronidase collagenase proteases, nucleases, lipases fibrinolysin coagulase

_______: hydrolyzes hyaluronic acid (a connective tissue component that holds animal cells together) * Allows pathogen to spread between cells

Hyaluronidase

_______: degrades collagen (extremely abundant connective tissue in animals) * Allows pathogen to spread through tissues

Collagenase

_______: * Degrade host macromolecules

Proteases, nucleases and lipases

______: dissolves fibrin clots

Fibrinolysin

______: induces fibrin clots

Coagulase

why does Streptococcus pyogenes makes streptokinase (a fibrinolysin)?

to escape clots that try to trap them

Staphylococcus aureus produces coagulase to protect it from phagocytes, why?

if it can induce clots to surround it, it can hide from immune system!

_____: proteins that allow bacteria to invade and enter directly into host cells

Invasins

_______: non-lactic acid, non-spore forming psychrotolerant member of the Firmicutes * Can be found in unpasteurized dairy products, improperly packaged processed meats * Produces invasins that promote phagocytosis by macrophages * Hijacks the cytoskeleton to escape the phagolysosome * Spreads from cell to cell avoiding the humoral immune response

Listeria monocytogenes

_____: bacteria in the blood

Bacteremia can be carried to different organs and tissues

______: bacteria multiplying in the blood

Septicemia Can lead to Sepsis * Widespread systemic inflammation * Septic shock * Can be caused by Gram negative bacteria (Ex: Gram negative sepsis) * Also by Gram positives: Staphylococci and Enterococci

why do we never want bacteria in our blood?

blood has perfect conditions for growth... and can take the bacteria EVERYWHERE in our body!

why can septic shock be caused by any gram negative bacteria?

because they produce the endotoxin

which gram positives cause septic shock?

staphylococci and enterococci

______: Proteins released by growing bacteria * Inhibit host cell function or kill host cells * Usually heat labile * Can be extremely toxic

exotoxins

Bacillus anthracis releases...

exotoxin has several virulence factors: * Capsule, exoenzymes and the anthrax toxin * Interferes with the immune response and kills macrophages

what are the three categories of exotoxins?

Cytoxins, AB toxins, Superantigens

______, a type of exotoxin, Disrupt cytoplasmic membrane integrity * Cell lysis and death

cytotoxins

what are the three types of cytotoxins?

hemolysins Lecithinase or phospholipase Leukocidins

_______: * Lyse many cells (not just red blood cells) * Ex. Streptococcus pyogenes * Produces streptolysin: attacks sterols in the cell membrane

Hemolysins

__________: * Dissolves membrane lipids * Ex. Clostridium perfringens * α-toxin (gas gangrene)

Lecithinase or phospholipase

_____: destroy white blood cells * Ex) Staphylococcus aureus: staphylococcal α-toxin * Toxin subunits insert into the membrane and oligomerizes to form a heptamer * A membrane spanning pore * Cell contents leak out and the cell dies

Leukocidins

what are the two subunits of AB toxins?

Two subunits: Active subunit and Binding subunit

__________ (Corynebacterium diphtheriae) * Subunit B: specifically binds to a protein on animal cells * Subunit A: moves across the membrane * Interferes with protein synthesis * Gene for diphtheria toxin is not encoded on the chromosome, but instead on a virus

Diphtheria toxin

T/F: Gene for diphtheria toxin is not encoded on the chromosome, but instead on a virus

true! gene is delivered to bacteria, but cannot be passed down to daughter cells

what are three other examples of AB toxins?

tetanus, botulism and cholera toxins

_______: Activate T cells to elicit an extreme immune response

superantigens

_______: Bind to MHC molecules and TCRs outside the antigen binding sites * Bridge the gap and mimics proper antigen presentation * Huge number of T cells can be activated * T cells produce cytokines * Extreme immune response * Extreme fever, systemic inflammation, shock, death

superantigens

Staphylococcus aureus cause _____, when super antigen exotoxin builds up over time

toxic shock syndrome toxin (TSST)

______: Lipopolysaccharide from the Gram negative outer membrane * The toxic part is: Lipid A * Only released when cells die * Generally considered less toxic than exotoxins * A lot is needed to cause symptoms

endotoxin

which kind of bacteria has endotoxin?

gram negative

______- colonizes the intestine and multiplies producing a huge number of bacteria * As these bacteria die they release endotoxin * Causes fever, diarrhea, generalized inflammation

Salmonella

when is Lipid A released from gram negative bacteria?

when they die- and lipopolysaccharides breakdown

Gram negative sepsis is an example of _____ release

endotoxin Gram negative bacteria multiply in the blood * Killed by immune system, releasing endotoxin * Massive inflammation leads to septic shock and death

Lecture 12: Medical Microbiology Flashcards

(113 cards)