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Flashcards in 31. Bacterial Structure and Function Deck (31):
1

steps of prokaryotic cell division?

1. replication of the bacterial chromosome is initiated at the CYTOPLASMIC MEMBRANE - this triggers cell division
2. each daughter chromosome is anchored to a different portion of the membrane
3. as the membrane grows, the daughter chromosomes are pulled apart
4. SEPTUM GROWS FROM OPPOSITE SIDES TOWARD THE CENTER OF THE CELL AND DIVIDES THE DAUGHTER BACTERIA INTO TWO CELLS
- PCN binding protein cleaves this
- incomplete cleavage causes bacteria to remain linked, forming chains (streptococci) or clusters (staphylococci)
- cell division requires transpeptidases (PBPs) and other enzymes

2

obligate anaerobes ___ O2

will be killed by O2 - obtain energy from fermentation

3

obligate aerobes ____ O2

require

4

facultative anaerobes ____O2

prefer O2 but can grow in absence of O2 via respiration or fermentation

5

microaerophiles ____ O2

can withstand low levels of O2

6

why is oxygen toxic to anaerobes?

don't have syperoxide dismitase (so can't converte superoxide to O2 and hydrogen peroxide)

and don't have catalase of peroxidase to decompose hydrogen peroxide into water

7

thermophilic vs mesophilic vs psychrophilic

thermophilic: optimum temp 55-75C and minum of 35-40C

mesophilic: grow well in us - optimum 30-45C, minimum 10-15C, most pathogenic bacteria

psychrophilic: facultative - similar to mesophils but can grow slowly near 0C; obligate - optimum temp is 15-18C and killed above 20C

8

pour plate method?

orig sample

dilute with water to make a 10^-1 dilution
dilute that with water to make a 10^-2 dilution
etc etc

mix dilution with warm agar and pour

Count CFUs and multiply by dilution factor to get viable count/mL of bacteria

9

____ is the state of being free of microorgs

aspesis

10

____ is the inactivation or elim of ALL viable organisms and their spores

sterilization (you can't be a little pregnant, or a little sterile)

11

____ is the process of removing or killing MOST microorgs on or in a material

disinfection

12

______ is a cleaning process which REDUCES pathogen levels to produce a healthy clean env't

sanitization

13

a _____ kills vegetative bacteria and SOME SPORES

germicide (attains disinfection)

14

a _____ is used on non-living objects to render them infectious; kills vegetative bacteria, fungi, viruses but NO SPORES

disinfectant

15

a _______ is used to prevent multiplication of microorgs when applied to living systems.

antiseptic (it is BACTERIOSTATIC and not bactericidal)

16

arrange most resistant to least resistant:

spores, hydrophilic viruses (non-liquid, non-enveloped), vegetative bacteria, mycobacteria, lipophilic viruses (lipid containing, enveloped)

most: spores

mycobacteria

hydrophilic viruses

vegetative bacteria

least: lipophilic viruses

17

autoclave

15lbs/sq inch pressure for 15-20 min at 121C

- sterilizes with moisture, microorgs are destroyed at a lower temperature than in dry heat
- method of choice when product can withstand such treatment since it is fast, least toxic, cheap, and can be performed on a large spectrum of instruments

18

hot air sterilization

160C for 1-4 hours

- sterilizes and used on materials that would be damaged by moist heat (gauzes, dressings, powders)

19

filtration disinfection

via

20

radiation disinfection

used on materials that would be destroyed by heat (petri dishes, gloves, syringes)

- UV = thymine dimers but poor penetration and so not sterilizing

- Ionizing (beta rays, GAMMA RAYS, x-rays) = breaks in DNA backbone and can STERILIZE

21

ethylene oxide (C2H4O)

sterilizes via its action as a powerful alkylating agent

- low temperature sterilization: use for heat-labile materials na delicate instruments

(but carcinogenic and explosive)

22

alcohols

disrupts cellular membranes, solubilization of lipids, and denaturation of proteins by acting on S-H functional groups

evaporate quickly - extended contact times hard to achieve
- inefective vs spore-forming bacteria

23

halogens

chlorine = 1:10 good as disinfectant

must be made fresh daily and iodine is just as good as a disinfectant and antiseptiv

method of action: oxidizes microbial proteins

24

disinfecting the skin?

alcohol scrub is better than soap and water, but need soap for C.diff to wash it off of your hands

use of chlorhexidine alcohol for skin antisepsis, NOT providone-iodine for surgical = significant reductions in hospital acquired infections

25

what is a biofilm?

a microbially derived sessile community ,typified by cells that are attached to a substratum, interface, or to each other, are embedded in a matrix of extracellular polymeric substance, and exhibit an altered phenotype with regard to growth, gene expression, and protein production

microbes that are
- attached to a hydrated surface
- embedded in a polysaccharide slime
- behave as a community
- demonstrate antibiotic resistance and resistance to clearance by the host immune system

26

biofilm disease examples?

CF
endocarditis
osteomyelitis
chronic UTI
prostatitis
otitis media
dental infections
endophthalmitis
serious skin infections
indwelling medical device infection

27

biofilm infection resolution?

cut it out

28

what % of all infections are biofilm related?

65-80

29

why are biofilms resistant to antibiotics?

biofilms reduce antibiotic penetration

cells withina biofilm are super slow growing (so not susceptible to things like rifampcin that inhibit RNA pol)

cells within a biofilm express many stress response genes that resist antibiotic action

30

why are there inaccurate MIC/MBC predictoin of bacterial populatoins in situ?

biofilms are in situ and MBC/MIC are calculated invitro

31

why are there inaccurate CFU determinants from clinical samples like a UTI?

one clump can have a million bacteria, but only count the one clump on the plate if not homogenized first

sometimes bacteria are viable but not culturable

missing the nidus of infection