Ch. 7 Flashcards
What do microbes require?
certain environmental and nutritional elements to grow and live
Why is it important to understand where and how microbes thrive?
understanding them allows us to remove them and prevent infection
remove pathogens by:
pasteurization, disinfection, sterilization
What are we trying to prevent in HAIs?
CLABSI (central line associated blood stream infection), CAUTI (catheter associated urinary tract infection), MRSA, C Diff (clostridium difficile), surgical site infections. *u need to follow proper protocol for insertion, maintenance, care, etc
lab setting microbes
grown as pure, single-species culture
nature microbes
bacteria intermingle with archaea and eukaryotes
bacteria divide by binary fission but can use…
budding or spore formation
budding
asexual, original cell elongates and then develops a small outgrowth on one side -> chromosome is duplicated and placed in the bud -> separation from mother cell
spore formation
performed by some fungi and bacteria; can b sexual or asexual in fungi; asexual in bact; NOT the same as endospores
generation time
exponential growth of bacteria. depends on species and environment for how fast generations occur
bacterial growth phases
1) lag phase: cells adjust to their environment
2) log phase: exponential cell growth
3) stationary phase: number of cells dividing = number of cells dying
4) death phase: cells die as waste accumulates and nutrients are depleted
microbes have niches which are
particular environment where they have optimal growth
low temperature for microbes
slow down enzymatic activity. less growth
increased temperature for microbes
speed up enzymatic activity. increased growth rate
high temperatures for microbes
denature proteins -> cell dies
thermophiles
40-75 degrees C. associated with compost piles or hotsprings
extreme thermophiles
65-120 degrees C. associated w hydrothermal vents at bottom of ocean
Mesophiles
10-50 degrees C (most of our human microbes)
psychrotrophs
0-30 degrees C. associated with lots of food born illnesses
psychrophiles
-20-10 degrees C. found in below freezing envs
barophiles
can withstand high pressure env of deep sea; hydrothermal vents at ocean bottom
acidophiles
grow at pH 1 (or less) to pH 5; live in volcanic vents and sulfur hot springs
neutrophiles
grow best in pH 5-8; majority of microorganisms
alkaliphiles
grow in pH 9-11; soda lakes
halophiles
thrive in high salt envs; dead sea, great salt lake of utah
facultative halophiles
tolerate high salt but may not grow well. Ex: S. aureus (MRSA infections)
extremophiles
exposed to combo of stressors (pH, temp, and/or salt)
obligate aerobe
absolute dependence on O2 used in metabolism
obligate anaerobe
grow in the presence of no oxygen
microaerophile
small amounts of O2 used in metabolism
aerotolerant anaerobe
O2 not used in metabolism but can tolerate it
facultative anaerobe
prefer using O2 but can survive w/o it
Most human pathogens are not…
obligate aerobes
essential nutrients
macronutrients: need large amounts to survive Ex: C, N, H
micronutrients: need in small amounts to survive Ex: iron, other metals, minerals
heterotrophs
get organic C from OUTSIDE source; CANNOT make it themselves. Ex: humans
autotrophs
don’t need an external C source; they can fix inorganic C and convert into organic C; “self-feeding” Ex: plants
growth factors
substances that are necessary for growth that organisms can’t make
fastidious
organisms need MULTIPLE growth factors to survive; “picky”
phototrophs
use light energy
chemotrophs
get energy from breaking down chemicals
P aeruginosa
can survive on limited nutrients in many envs, opportunistic, biofilms, facultative anaerobe, chemoheterotroph. common in burn pts and CF and immunocompromised; increasingly drug resistant; HAI
liquid media
ideal for growing large batches of microbes; *broth media
solid media
useful for isolating colonies and observing specific culture characteristics like morphology
semisolid media
useful for motility testing
complex media
we don’t know every component and amt of the components; good for growing fastidious organisms
defined media
we know exact components and amts of components
differential media
used to visually distinguish organisms from one another; *ex: blood agar
selective media
allows for growth of some organisms while suppressing others; *ex: mannitol salt agar and eosin methylene blue agar
aseptic techniques
protects us and the samples! *PPE, disinfecting, sealing contents after collection, sterilization, wash hands, new equipment, heat treatment, sanitation
why are cell counts important?
We wanna know growth rates in patient samples to determine antibiotics susceptibility
cell counts have:
direct counts and indirect counts
What are commonly used tools to identify microbes?
physical analysis: microscopy, staining, looking at morphological features
biochemical analysis: metabolic activity
genetic methods: PCR, electrophoresis, sequencing
decontamination
act of trying to reduce/get rid of microbes in environment
reduce decontamination
disinfecting -> reduces microbial #s ; used when preparing food, cosmetics, external medical equipment
remove decontamination
sterilizing -> eliminates ALL bact, viruses, endospores; required for drugs, medical procedure objects, media glassware
what does temperature control?
microbial growth. *think of food spoilage, autoclaving, storing samples, preserving
radiation
used to disinfect or sterilize
filtration
may wanna use if sample is sensitive to heat or if can’t use radiation
germicides
chemicals that control microbial growth. two types of germicides: Microbiocidal: germicides that KILL microbesMicrobiostatic: germicides that only INHIBIT microbial growth
disinfectants
treat inanimate objects
antiseptics
applied to living tissue
germicides three tiers:
low-level agents: destroy all bacteria except M. tub; can destroy fungi and some viruses, but NOT endospores
intermediate-level agents: destroy all bacteria including M. tub, fungi, virus, but NO endospores
High-level agents: kills everything including endospores
critical equipment
comes into contact w sterile body sites or vascular sys; MUST be sterilized; *ex: surgical tools, implants, catheters
semi-critical equipment
comes in contact w mucous membranes or non intact skin; should be free of bact, fungi, viruses; *ex: respiratory equipment, endoscopes
noncritical equipment
contact pts’ intact skin; require less stringent disinfection; *ex: stethoscopes, BP cuffs, pulse ox
what should be considered when selecting an appropriate germicide?
item use, germicide reactivity, germicide concentration and treatment times, types of infectious agents being controlled, germicide toxicity, antiseptic use or disinfectant use
mycobacterium control
Mycobacterium causes TB and leprosy so control by reducing airborne particles; *isolation rooms and HEPA filters and high level disinfectants
endospores
survive drying, radiation, boiling, chemicals, and heat treatments. get rid of by autoclaving
viral control
viruses can be resistant to some measures.
lipids in the viral envelope are sensitive to heat, drying, and detergents
prion control
surgical devices are reused after autoclaving or chemical sterilization.
withstand autoclaving and chemical sterilization (increase pressure when autoclaving)
