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DWT exam 1 > Bacteriology > Flashcards

Bacteriology Flashcards

1
Q

what domain of life are bacteria?

A

prokaryotes

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2
Q

unique features of bacteria (differences from eukaryotes)

A
  • rigid cell walls containing a peptidoglycan layer,
  • nucleus is not bound by a nuclear membrane, is usually singular and circular
  • do not have an nucleolus, mitochondria, endoplasmic reticulum, or Golgi apparatus
  • multiply by binary fission
  • exhibit considerable morphologic diversity but
    are usually <5μm
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3
Q

cocci

A

circles

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4
Q

staphylococci

A

clumps/clusters of cocci

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5
Q

streptococci

A

chains of cocci

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6
Q

cell capsule

A
  • Amorphous, gelatinous materials lying outside the cell wall (= “goop”)
  • Most commonly carbohydrates, but some are polypeptides (= “sticky goop”)
  • Very variable (antigenically diverse)
  • Importance: anti-phagocytic, may help with adherence and prolong survival
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7
Q

cell wall

A
  • ~20% of total dry weight of bacteria
  • gives bacteria their shape and rigid structure!
  • differs in structure & chemical composition between different bacteria; which influences their pathogenicity and staining characteristics:
  • –Gram Positive
  • –Gram Negative
  • –Acid Fast
  • –“Others”
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8
Q

gram stain process

A
  1. fixation (heat)
  2. crystal violet
  3. iodine treatment (binds to crytal violet to form complex)
  4. decolorization (alcohol)
  5. counter stain safranin
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9
Q

is antimicrobial therapy most effective as narrow or broad spectrum?

A

narrow

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10
Q

gram positive bacteria

A
  • simpler structure cf gram negative
  • thicker more uniform cell wall
  • predominantly composed of peptidoglycan & teichoic acid
  • the peptidoglycan dessicates on decolourization (gram stain) making it less permeable to dye complex
  • thicker wall also more resistant to mechanical damage
  • peptidoglycan is a target for some antibiotics and also lysozyme
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11
Q

gram negative bacteria

A
  • more complex cf gram positive
    Outer membrane (OM) which has:
    * Lipopolysaccharide (LPS) MAJOR virulence factor
  • Porins
  • periplasmic space containing smaller amount ofpeptidoglycan
  • due to its structure, the OM excludes hydrophilic molecules and renders gram negative bacteria resistant to some detergents
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12
Q

acid fast bacteria

A
  • cell envelope contains additional molecules:
  • Mycolic Acid
  • Glycolipids and Fatty Acids
  • Polypeptides

makes them very hard to stain (so special stain – Acid
Fast)
also allows them to:
* Survive in the environment
* Survive inside cells!!!!
* target for other antibiotics

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13
Q

flagella

A

confer motility

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14
Q

fimbriae (pili)

A

important for adherence

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15
Q

spores

A

important for long term survival and physical resistance

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16
Q

biofilms

A
  • bacteria exist as planktonic (free) or sessile (attached)
  • biofims are sessile and created by some bacteria when
    a bacterial population becomes adherent to each other and/or a surface, and it then enclosed within a biopolymer matrix
  • Inside the biofilm the bacteria can act as an “organism”
    through “quorum sensing”
  • Biofilms help in the pathogenesis of bacterial infections by:
  • –aid colonization
  • –avoid phagocytosis
  • –avoid antibiotics
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17
Q

how do bacteria divide?

A

binary fission

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18
Q

how do bacteria divide?

A

binary fission

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19
Q

what influences bacterial growth/replication?

A
  • Genetics (type of bacteria)
  • Nutritional factors (nutrient media)
  • Chemical, physical and environmental factors
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20
Q

bacterial growth on an agar plate

A

on an agar plate a single colony is a clonal expansion of a single bacterium
Small colonies = slow growing
Big colonies = fast growing
the number of colonies is directly related to the number of bacteria you put on there!!!
optimal pH is neutral to alkaline
optimal tonicity is isotonic to hypotonic

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21
Q

temperature effect on bacterial growth

A
  • Optimal temperature for growth = 98.6°F (body temp)
  • But most can grow 68-113°F
  • Some pathogenic bacteria grow outside this range
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22
Q

strict/obligate aerobes

A

require O2 for growth

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23
Q

strict/obligate anaerobes

A

killed by O2

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24
Q

Facultative anaerobes

A

can grow in O2 or without

25
Q

microaerophiles

A

Require reduced O2 (< than the 20% in air); some also like ↑ CO2)

26
Q

Where do strict anaerobic bacteria live in the body?

A
  • GI tract (lumen)
  • mouth (between teeth and gums)
  • urogenital tract (vagina)
27
Q

bacterial genome

A

haploid circular chromosome (double stranded)
plasmids
* small circular DNA which can autonomously replicate

28
Q

bacteriophages

A

viruses that infect bacteria
integrate into bacterial genome

29
Q

recombination of DNA

A

transduction: phage mediated transfer
conjugation: plasmid transfer
transformation: uptake of naked DNA

30
Q

host

A

any organism that supports the survival and growth of microorganisms (parasites, bacteria, viruses, etc.)

31
Q

saprophyte

A
  • organisms that live on dead or decaying organic matter (environment)
  • usually not parasites of animals but can occasionally live in/on animals & cause disease
32
Q

parasite

A
  • a general term that denotes an organism that lives on or within another living organism and derives sustenance
  • the parasite does not necessarily harm the host, but has the ability to given the right circumstances

it should also be noted that the distinction between saprophyte and parasite is not complete; some microorganisms can live as either a saprophyte or a parasite e.g., Clostridia may live in the soil as well as the intestine

33
Q

commensal parasite

A
  • an organism that lives in/on the host without causing disease
  • most of the bacteria that normally live in the intestine, on the skin, and on mucous membranes are commensals
34
Q

pathogen

A
  • Parasitic and saprophytic bacteria which have the potential to cause disease
  • Pathogens don’t always cause disease, but become pathogenic under conditions where host animals, or their tissues, allow invasion and disease production
  • can either live on the host as part of the normal flora i.e., be present on MOST of the animals in a population
  • Or they can live in only a proportion of animals in a population (= carrier state)
35
Q

carriers/carrier state

A
  • Animals with a specific bacterial pathogens present in “fewer” animals within a population are called “carriers”
  • These pathogens may be causing subclinical disease, or no clinical disease at all, but still shed the pathogen
36
Q

streptococcus zooepidemicus

A

most common pathogen of horses
normal flora
opportunistic

37
Q

Where is the normal flora on the skin?

A

all over skin
more in folds, crevaces
mostly gr +

38
Q

where is normal flora on the ear?

A

ear flap
vertical canal (fewer than ear flap)
horzontal canal (fewer than vertical canal)
sterile after tympanic membrane

39
Q

Where is normal flora bacteria on the udder?

A

in the streak canal
cistern is sterile

40
Q

where is normal flora on the eye?

A

conjunctiva (few due to tears)
very few on cornea
inside eye is sterile

41
Q

where is normal flora in the respiratory tract?

A

normal flora is rostral to the larynx
caudal to larynx is sterile
mix of gr - and gr +

42
Q

where is normal flora in the urinary tract?

A

distal urethra
bladder is sterile
gr- and gr+

43
Q

where is normal flora in the genital tract?

A

distal vagina
past cervix is sterile
gr+ and gr-

44
Q

pathogenicity vs virulence

A
  • the capacity of a bacteria to produce disease in a host is pathogenicity (e.g., S. aureus is a pathogenic bacteria)
  • variation in this capacity is referred to in terms of virulence (i.e., highly versus weakly virulent)
  • virulence may vary between bacteria genera, species, or strains and also depend on site of infection (e.g., some strains of E. coli are only virulent in the intestine)
45
Q

Obligate (true) pathogens

A

bacteria that must cause disease in order to be transmitted from one host to another AND must also infect a host in order to survive; they can’t survive outside the host

46
Q

opportunistic pathogens

A

more common than obligate/true pathogens
bacteria that are normal flora or saprophytes, but can cause disease when something changes in the host animal that allows them to invade and cause disease

47
Q

predisposing factors to opportunistic pathogens

A
  • tissue damage causing impairment of hosts defense mechanisms
  • damage to innate defense mechanisms
  • introduction of microorganisms to body sites where they are not normally found
  • distrubance of normal flora
48
Q

infectivity

A
  • capacity of the organism to become established in the tissues of the host
  • involves the ability to penetrate the tissues, survive the host’s defences, and multiply/disseminate within the host
49
Q

innate predisposing factors

A
  • breed/species
  • age
  • sex
50
Q

external predisposing factors

A
  • diet/nutrition
  • temperature
  • overcrowding
  • transportation
  • change in food
  • weaning
51
Q

internal host stressors/predisposing factors

A
  • anything causing tissue damage (direct trauma, circulatory distrubance)
  • anything that changes host response (endocrine changes, immunosuppressive organisms/drugs)
52
Q

what type of bacteria found on the skin?

A

gr +
staphylococci
(staph pseuodintermedius in dogs)

53
Q

what bacteria usually causes skin/ear infections in dogs?

A

staph pseuodintermedius
gr + cocci

54
Q

sources of bacteria that cause infection

A
  • Normal Flora (opportunistic infections)
  • Animals Incubating Disease
  • Animals with Overt Disease
  • Carrier Animals (subclinical infections or recovered)
  • Fomites (inanimate objects in environment that are contaminated with pathogens)
  • environment (saprophytes)
55
Q

transmission routes of bacteria

A
  • Inhalation
  • Ingestion
  • Inoculation (e.g., wounds, bites, etc)
  • Transplacental
  • Via genital tract
  • Via umbilicus
56
Q

key things a bacteria needs to do to cause disease

A
  • attach and colonize
  • gain access to body
  • evade innate defense
  • cause damage
57
Q

virulence factors for adhesion

A

Fimbriae(Pili) and Adhesions Factors (Attach)
* present on some bacteria (particularly gram negative)
* assist adhesion to a cell surface through a specific interaction with cell surface receptors
* weaker adhesion by physico-chemical attractions
* allow bacteria to attach and colonize body sites

58
Q

virulence factors for invasion

A
  • Bacteria can actively or passively enter a host
  • Passive entry through damaged or compromised tissues (e.g. S. aureus)
  • Active entry via intact epithelium using specific molecules including exotoxins (e.g., Leptospira)
59
Q

virulence factors for survival inside tissue

A

Anti-phagocytic Molecules (evasion)
* Capsule, slime layer, biofilms, M protein etc
* Protect the bacteria from ingestion and killing by phagocytic cells (one of the main innate/primary defense mechanisms)
* body gets around this by using antibodies but this takes ~2 weeks

Iron Sequestration
* bacteria must have iron to survive inside a host
* most** iron in hosts are bound to lactoferrin/transferrin**
* but many pathogenic bacteria have siderophores that remove iron from these molecules
* others lyse RBCs and get iron from hemoglobin

Survival in Protected Sites
* as a general rule, extracellular bacteria are cleared with development of antibody
* but some may survive longer in protected sites e.g., Leptospira in renal tubules

Intracellular Survival
* SOME (not all) bacteria can survive inside cells
* Facultative Intracellular Parasites
* Can live outside or inside cells
* Some of the major pathogens (e.g., S. aureus, Salmonella, Brucella etc.)
* Obligate Intracellular Parasites
* Must live inside cells whilst in animal host
* Less common and often “other” bacteria (Rickettsia, Chlamydophila)

DWT exam 1 (13 decks)

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