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Flashcards in M4: Bacteria II Deck (48)
1

Doubling times are faster for (prokaryotes/eukaryotes) than for (prokaryotes/eukaryotes)

prokaryotes
eukaryotes

2

Bacterial growth is often studied in vitro:
Cultivation methods (2)

solid media
broth media

3

Bacterial growth is often studied in vitro:
Cultivation methods:

Solid media: useful for obtaining _ cultures by _

Broth media: can be used to propagate a _ culture using "_ technique"

"pure"
streak-plating

pure
aseptic

4

Bacterial growth is often studied in vitro:
To measure bacterial growth, you can evaluate either:

_ bacteria in a culture (measure _ with a _)

_ bacteria in a culture (count _ on plates, after sample _)

Total
turbidity
spectrophotometer

Viable
colonies
dilution

5

A typical bacterial growth curve:
Stages (4)

Lag
Exponential
Stationary
Total / Viable

6

A typical bacterial growth curve:

Lag

Exponential

Stationary

Total / Viable

preparing to grow

growth, doubling time

almost all bacteria are alive & viable

# viable is less than total #

7

Important factors for bacterial growth: (5)

temperature
pH
oxygen (redox) concentrations
nutrients (e.g. iron)
osmolarity

8

Bacterial growth in vivo vs. in vitro

In vitro studies provide an inexact model for understanding bacterial growth in vivo

9

Bacterial Physiology and Pathogenesis:

Some host defenses are targeted at bacterial physiology

For example, the body uses _ proteins (_ and _) to restrict the availability of iron for
pathogens

However, pathogens can fight back:

a. By producing their own _ molecules (e.g. _)

b. Some bacteria (e.g. the pathogenic _) can bind human _ and _ to their surface and then use that bound iron.

iron-binding
lactoferrin and transferrin

iron-binding
siderophores

Neisseria spp.
lactoferrin and transferrin

10

Bacterial Physiology and Pathogenesis:

_ is key for growth of bacterial pathogens.

These organisms obtain it by:

_: uses an _ substance (e.g. O2) as the terminal electron acceptor

_: uses an _ substance as the terminal electron acceptor

_, e.g., _ and _

There is, usually, a relationship between _ and bacterial _

Energy

Respiration
inorganic

Fermentation
organic

Intracellular energy theft
Chlamydiae and Rickettsiae

energy production
growth rates

11

Aerobes
e.g.

grow only in the presence of O2

e.g. Pseudomonas aeruginosa

12

Microaerophiles
e.g.

a special group of aerobes requiring O2, but at lower concentrations than found in normal air

e.g. Campylobacter spp.

13

Facultative anaerobes

grow by _, but shift their metabolism to _

More ATP is produced during (fermentation/respiration) than (fermentation/respiration), so growth is faster here

e.g.

grow in either the presence or absence of O2

fermentations in the absence of O2
respiration in the presence of O2

respiration
fermentation

e.g. E. coli

14

Aerotolerants
e.g.

grow in presence or absence of O2, but metabolism always uses fermentation

most Streptococcus spp.

15

Strict anaerobes
e.g.

grow only in the absence of O2

e.g. Clostridium spp

16

Why some bacteria are anaerobic:

Anaerobes often lack _ (which breaks down _ formed after cells are exposed to _).

Anaerobes often lack _ (which detoxifies free radical forms of _ that form after cells are exposed to _).

Anaerobes may have very sensitive _ that require a _ environment.

Bottom line: anaerobes must be in a _ environment and O2 (raises/lowers) the _.

catalase
toxic H2O2
air

superoxide dismutase
O2
air

enzymes
reduced

low redox (reduced)
raises
redox potential

17

The redox potential of healthy tissue is too (high/low) for anaerobes to grow.

However, a number of medical conditions can (raise/lower) tissue redox potential: (3)

high

lower

a. Circulatory problems (from heart disease, etc).

b. Tight orthopedic casts.

c. The co-presence of facultative anaerobes (which can consume oxygen) during an infection.

18

Anaerobes are often present as _ in many locations in the healthy human body:

a. _: e.g. _

b. _: e.g. _

c. _: e.g. _; _

d. _: e.g. _

normal flora

a. Skin: e.g. Propionibacterium spp.

b. Mouth: e.g. Porphyromonas gingivalis

c. Vagina: e.g. Lactobacillus spp.; Prevotella bivia

d. Colon: e.g. Bacteroides fragilis

19

Gram-positive anaerobes of medical importance:

Sporeforming rods: _

Non-sporeforming rods: _

Cocci: _, _

Clostridium spp.

Actinomyces spp.

Peptococcus, Peptostreptococcus spp.

20

Gram-negative anaerobes of medical importance:

Non-sporeforming rods: _-like group _

Cocci: _

Bacteroides-like group
Fusobacterium spp.

Veillonella spp.

21

Medical conditions that could lead to anaerobic infection include:

(High/Low) tissue redox conditions from _ problems

_ therapy: can lead to _ infection

_ wounds

Aspiration of _ into the _

Spillage of _ into the _ due to perforation of the _

Low
circulatory

Antibiotic
Clostridium difficile

Bite

mouth flora into the lungs

intestinal contents
peritoneal cavity
GI tract

22

Types of anaerobic infections: (2)

clostridial (exotoxin-mediated) - produce a lot of toxins

nonclostridial (usually non-exotoxin-mediated) - don't produce toxins

23

Characteristics of Nonclostridial Anaerobic Infections:

_ formation (can be anywhere in the body).

Often _.

Often involve highly _-resistant bacteria (anaerobes have intrinsic resistance to some _ but these bacteria also carry many resistance _).

Can involve a mix of _ anaerobes and _ anaerobes (_ can consume O2, (raising/lowering) local redox conditions)

Abscess

polymicrobic - many species involved

antibiotic-resistant
antibiotics
plasmids

facultative
true

facultatives
lowering

24

Characteristics of Nonclostridial Anaerobic Infections:

Nonclostridial anaerobic infections are often very _ because an abscess has no _ for antibiotic delivery.

For abscesses: _ the abscess and (often) give multiple _

Nonclostridial anaerobes often have relatively (high/low) virulence (it takes (many/few) to start an infection), but can be _.

Nonclostridial anaerobes are often _, _, and produce _ (odors are a clue to an anaerobic infection)

difficult to treat
blood supply

surgically drain
antibiotics

low
many
fatal

slow-growing
fastidious - nutritionally demanding
fermentation gases

25

Case Study:

39.9°C

white blood cell count was slightly elevated

retroperitoneal abscess, which was surgically drained

patient was placed on antibiotics

cultures made from the drained material grew anaerobic gram-negative bacteria

What type of bacteria?

Bacteriodes-like (the most important nonclostridial anaerobes)

26

Biology and Pathogenesis of the Bacteroides-like Bacteria:
Characteristics:

Gram-(+/-), (aerobic/anaerobic) rods found as normal flora in the _, _, & _

At one time, these bacteria were all classified in the genus _, but the pigmented, bile-sensitive species are now assigned to the _ and _.

negative
anaerobic
colon, vagina and mouth

Bacteroides
Porphyromonas and Prevotella

27

Biology and Pathogenesis of the Bacteroides-like Bacteria:
Virulence factors:

The LPS of Bacteroides spp. (is / is not) endotoxic, although LPS from Porphyromonas and Prevotella (does / does not) have endotoxic properties.

B. fragilis and P. melaninogenica make a _, which is probably _.

Some B. fragilis strains make an (enterotoxin / exotoxin), but generally these bacteria don't make (enterotoxin / exotoxin).

All these species make _ and other enzymes that might help them spread through tissue.

Not all gram-negative anaerobes are equally pathogenic: B. fragilis is only 0.5% of the _ flora yet is the most frequently isolated anaerobe from _ and _ infections.

is not
does

capsule
antiphagocytic

enterotoxin - exotoxin in the gut
exotoxins - secreted by bacteria

proteases

colonic
intra-abdominal and bloodstream

28

Biology and Pathogenesis of the Bacteroides-like Bacteria:
Entry:

These bacteria are part of the normal flora, so they cause (exogenous / endogenous) infections, breeching the _ via surgery, wounds, ruptures, etc.

Entry is important, but must also be accompanied by _ for growth. These infections (are / are not) contagious.

endogenous
epithelium

low tissue redox
are not

29

Biology and Pathogenesis of the Bacteroides-like Bacteria:

Usually cause disease near their _:

Bacteroides fragilis: normally found in the _, often causes _ infections that involve two stages: _ and then (if untreated) _ formation.

Prevotella bivia: found in _, can cause _ inflammatory disease and _.

Prevotella melaninogenica and Porphyromonas gingivalis: found in _, can cause _ infections (e.g., _).

normal flora colonization body site

colon
abdominal
peritonitis
abscess

female genital tract
pelvic
infertility

mouth
respiratory tract
dental, chronic sinusitis, pulmonary infections

30

Biology and Pathogenesis of the Bacteroides-like Bacteria:
Diseases:

Often involve _ and _ formation.

However, these bacteria can enter the _ and cause _. Can be rapidly fatal.

Not all gram-negative anaerobes are equally likely to cause disease.

Treatment for abscesses: _ and use of _effective against anaerobes (e.g., _).

inflammation
abscess

bloodstream
bacteremia

surgical drainage
antibiotics
metronidazole

31

Case Study:

fever

bullous purple lesion

gram+ rods

occult blood

injury or degeneration of skeletal muscle

on incision of the muscle, gas issued forth

What type of bacteria?

histotoxic clostridia

32

Histotoxic Clostridia:
Biology: includes several clostridial species:

Most common and important is _: involved in ~90% of infections caused by these organisms.

_: associated with infections in patients with cancer of the GI tract.

All are Gram-(+/-), (aerobic / anaerobic), _

Some are present as normal _ flora, some in the _ and some in both.

C. perfringens

C. septicum

positive
anaerobic
spore-forming rods

GI
soil

33

Histotoxic Clostridia:
Virulence Factors:

(Endotoxins / Exotoxins): protein toxins made and secreted (inside / outside) the cell.

Most important single toxin for C. perfringens is _, which is a lecithinase (phospholipase C) that disrupts _

Exotoxins
outside

α toxin
mammalian plasma membranes

34

Histotoxic Clostridia:
Entry:

Histotoxic clostridia can cause (endogenous / exogenous / both endogenous and exogenous) infections.

Usually result from entry of _ or _ into wounds, ruptures, tumors, etc.

Need (high/low) tissue redox for growth.

both endogenous and exogenous

vegetative cells
spores

low

35

Diseases caused by the histotoxic clostridia:

A full spectrum of wound infections ranging from:

_ (_): bacteria are present in _ (low redox condition); toxins kill cells to form _ tissue (low redox), allowing progressive spread of infection. Toxins also enter _ and damage distant organs. Rapidly fatal w/o treatment (if possible).

_: somewhat less serious, involves only _ and _ tissue.

_: least serious, only involves _ tissue.

Gas gangrene (clostridial myonecrosis)
muscle
necrotic
circulation

Anaerobic cellulitis
cutaneous and subcutaneous

Simple wound infections
cutaneous

36

Diseases caused by the histotoxic clostridia:

_ infections: e.g., _ infections (in past were particularly associated with illegal abortions but can occur with any poorly-performed abortion)

_ / _

_: 3rd most common food poisoning; not usually life-threatening, an (enterotoxin / exotoxin) causes diarrhea and abdominal cramps.

Organ
uterine

Septicemia/bacteremias

C. perfringens type A food poisoning
enterotoxin

37

Diseases caused by the histotoxic clostridia:
Treatment/Control:

Very difficult for _, but involves:

_ of affected tissue by surgery (must be performed early in infection), often involves _. _ are in a supportive role.

_ (?)

_ better option: keep wounds clean.

gas gangrene

Removal
amputation
Antibiotics

Hyperbaric O2

Prevention

38

Bacterial Endospores: The Most Resistant Life Forms:

Among the pathogens, endospores are only formed by _ (aerobic or facultative anaerobic) and _ (anaerobic).

_ is a survival response to a _ environment.

This (is / is not) a reproductive strategy (1 cell gives rise to (#) spore(s)).

Bacillus
Clostridium

Sporulation
poor

is not
only 1

39

Bacterial Endospores: The Most Resistant Life Forms:

Bacterial endospores are highly resistant to: (4)

Therefore, spores are very (easy / hard) to kill.

_ is aimed at killing bacterial endospores; if successful, all other life forms will also be killed.

Heat
Radiation
Chemicals (including some disinfectants)
Drying

hard

Sterilization

40

Bacterial Endospores: The Most Resistant Life Forms:

Microscopic appearance of bacterial endospores

cell with endospore --> [lysis] --> debris + free spore

41

Why spores are so resistant

They have low internal water and are rich in DNA
stabilizing proteins

42

Why spores can last a long time

Name for this phenomenon

Spores lack any internal H20, so they lack metabolism

"suspended animation"

43

Several diseases can result from implantation or inhalation of spores: (4)

Anthrax: Bacillus anthracis

Tetanus: Clostridium tetani

Infections caused by the histotoxic clostridia

Clostridium difficile

44

Endospores and Disease: Tetanus:
Biology:

Caused by _, a Gram-(+/-), _-forming, (aerobic / anaerobic) rod

Spores of this bacteria are found in _ throughout the world.

C. tetani
positive
spore
anaerobic

soils

45

Endospores and Disease: Tetanus:
Virulence Factors:

Toxin

Factor

Extremely _

Tetanus neurotoxin (tetanospasmin)

Inhibits release of inhibitory neurotransmitters (e.g., glycine), resulting in uncontrolled muscle contractions

lethal

46

Endospores and Disease: Tetanus:
Entry:

Usually involves implantation of _ at a wound or during _ (_), via contaminated umbilical stump

If the tissue redox potential is sufficiently low, the spore _ and makes _

Can have a long _ while an implanted spore waits for proper conditions to grow and germinate.

spores
childbirth (neonatal tetanus)

germinates into a new cell
tetanus toxin

incubation time

47

Endospores and Disease: Tetanus:
Disease:

Toxin produced in wound and then migrates along _ into _

Toxin _; muscles are _.

Convulsive muscle contractions of voluntary muscles of the _, _, and _.

Death results from _.

nerves
CNS

blocks inhibitory neurotransmitter release
constantly stimulated

jaw (trismus, lockjaw), back, and extremities

respiratory failure

48

Endospores and Disease: Tetanus:
Treatment/Prevention:

Treatment: very (easy / difficult), give _, _, and assisted _.

Prevention: The disease itself does not confer _ but immunization can be induced using _, part of the _ vaccine.

difficult
tetanus antitoxin
muscle relaxants
ventilation

immunity
tetanus toxoid
DPT