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Introduction to Medical Microbiology
Block 2 overview
40
Microbiology
Graduate
04/15/2011

Additional Microbiology Flashcards

 


 

Cards

Term
Differentiate prions, viruses, degenerate bacteria & bacteria (prokaryotes) from each other and from eukaryotes (fungi, parasites) on the basis of size, nuclear material & organization, reproduction & cellular organization; emerging infections
Definition

PRION: smallest; disruptive proteins (ie. mad cow disease)

VIRUS: 18-300nm; RNA or DNA; protein +/- outer mem; obligate parasite; targeted to cell surf markers; lysis or transforming (ie. poliovirus)

DEGENERATE BACT: viral size; obligate intracellular parasites or w/o cell wall (ie. chylamydia, rickettsia, mycoplasma)

BACTERIA: prokaryotes; 1x1-20μm; cell wall; no cytoplasmic organelles excpt ribo; no nuc mem

FUNGI: eukaryotic (nuc mem, many chrom, ER, mito, golgi), uni-(yeast)/multicellular(mold); a-/sexual repro (ie. ringworm, Candida albicans)

PARASITES: complex; uni-(protozoa)/multicellular(helminths); eukaryotic; 1-2μm(cryptosporidium)-10m(tapeworm); includes some arthropodes/ectoparasites (mites/fleas/lice)

EMERGING INFECTIONS: not new organisms, just genetic variations OR new environ conditions => emergence/re-emergence (ie. MRSA/SARS)

Term
name and give examples of parasite evasion strategies (6)
Definition

1. ELICIT MINIMAL RESPONSE (Herpes simplex virus-survives in host cells; latent infection)

2. EVADE EFFECTS OF RESPONSE (mycobacteria-live unharmed in granulomatous response designed to localize/destroy infection)

3. DEPRESS HOST'S DEFENSE (HIV-destroy T cells; malaria-depress immune response)

4. ANTIGENIC CHANGE (spirochetes/viruses-chg surf antigens)

5. RAPID REPLICATION (bact/virus/protozoa prod acute infection before recovery/immunity)

6. SURVIVAL IN WEAKLY RESPONSIVE INDIV: children/immunocompromised (cytomegalovirus)

Term
organisms resistant to sterilization
Definition

spores 

prions

mycobacteria

high numbers

Term
define sterilization
Definition
total destruction of ALL microorganisms
Term
common agents of sterilization (5)
Definition

1. MOIST HEAT boiling (kills vegetative cells); autoclave (steam under pressure kills spores) 121-132*C for >15min; boil prions in 1N NaOH 10 min -> extensive autoclaving

2. DRY HEAT oven 2-3hrs @ 170*C (kills spores, may leave pyrogens)

3. FILTRATION remove microorg (std pore size:0.2μm for HEPA filters)

4. RADIATION germicidal UV & ionizing (DNA dmg; blocks replication) 

5. ETHYLENE OXIDE GAS toxic alkylating agent; sterilize heat-sensitive materials

Term
define disinfection
Definition

destruction of most organisms

CANNOT be called "sterilized"

 

HIGH LEVEL: boiling h20, h202 (heat sensitive)

INTERMEDIATE LEVEL: alcohols; phenolics

LOW LEVEL: quaternary ammonium cpds; pasteurization 

Term
define antisepsis
Definition
most organisms on skin or in tissue are killed (spores NOT killed)
Term
list antisepsis agents (5)
Definition

1. ALCOHOLS: kills most org includes mycobact but NOT spores; more effective w/ h20

2. IODOPHORS: iodine carriers; reactive agent that precipitates/oxidizes proteins

3. CHLORHEXIDINE: slower; residual action

4. PHENOLIC CPDS: attack lipid mem; effective vs mycobact; improved w/ halogens

5. QUATERNARY AMMONIUM CPDS: 4 organic grps linked to N; attacks mem; not effective vs mycobact, pseudomonas, viruses, or spores

Term
How could one sterilize a heat-labile solution to be injected into a patient?
Definition
filtration w/ 0.2μm pore size
Term
Why is 70% ethanol better than 95% for antiseptic usage?
Definition
higher h20 content penetrates membranes more efficiently
Term
What does a phenol coefficient of 5 mean?
Definition
this particular antibacterial agent is 5 times more effective as phenol
Term
What is the difference bt/w genetic drift and genetic shift?
Definition

GENETIC DRIFT: small changes; point mutations; base substitutions

GENETIC SHIFT: major changes; partial chromosome deletion/replacement (ie. flu pandemic-major change in genetic component of influenzae virus)

Term
What is the diffusion test?
Definition

eg. Mueller-Hinton

used to identify antibiotic resistant bact

procedure: A&P disk saturated w/ antibiotic is placed on agar w/ colonies; no inhibition of growth => antibiotic resistance

Term

1. What is the MIC used for?

2. How can it be determined?

Definition

1. minimum inhibitory concentration

method to quantify effectiveness of an antibiotic

2. dilution tests: series of dilutions of antibiotics to find the minimum amount that inhibits bacterial growth (MIC=some growth but no visible turbidity)

Term
What does MBC stand for?
Definition

minimum bactericidal concentration

usually more concentrated than MIC

Term
Define prokaryotic reassortment & give some examples
Definition

mixing of chromosomal elements from different strains (mechanism of genetic shift)

requires segmented genomes

ex: RNA viruses such as orthomyxoviridae (influenza rapidly acquires new hemagglutinin & neuraminidase antigens; has been the initiating factor in some epidemics), reoviridae (rotovirus), bunyaviridae, & arenaviridae 

Term
Describe plasmid transformation (plasmid-mediated transfer)
Definition

additional plasmid-borne genetic info (often important in virulence)

episome is a plasmid able to integrate into the chromosome

gram- bacteria do this only bt/w strains of same or closely-related species (gram+ can do this too)

mechanisms: seg chrom facilitating reassortment uptake; "self-transfer"; conjugative [involves pilus & sex factors]

Term
what do these terms mean: polyploidy & heteropolyploidy 
Definition

they both describe the genetic (dis)similarity of different strains

polyploidy: mixing bt/w same strains

heteropolyploidy: mixing bt/w different strains 

Term
What does BOAR stand for and why are these items important in virology?
Definition

B-bunyaviridae

O-orthomyxoviridae (influenza)

A-arenaviridae

R-reoviridae (rotovirus)

 

These are the RNA viruses w/ segmented chromosomes that can undergo reassortment

Term
Which organisms do genetic recombination?
Definition

all non-virus organisms (except retroviridae (HIV-RNA) & chordoviridae (polio RNA virus) DO exhibit recombination)

 

Term
What is genetic recombination?
Definition
transfer of genetic material bt/w two HOMOLOGOUS chromosomes (involves a Holliday structure)
Term
Describe the process of plasmid transformation:
Definition

1. treat antibiotic-sensitive bact w/ CaCl2=>incr cell wall permeability

2. added plasmid DNA (genes for antibiot resistance) enters bact

3. plasmid DNA integrates into host chromosome

4. host cultured on antibiotic medium to test for antibiotic resistance (selection for bact that have undergone transformation) 

Term
What are jumping genes/transposons?
Definition

pieces of DNA that can "hop" bt/w organisms

oftentimes is on a plasmid

Term
Steps of transformation (3)
Definition

1. DNA binds to bact cell surf

2. DNA uptake through cell mem

3. DNA integrated into chrom OR becomes autonomously replicating plasmid

Term
Name the gram+ and gram- organisms exhibiting transformation:
Definition

1. GRAM +: Streptococcus pneumoniae, Staphylococcus aureus, Bacillus subtilis

 

2. GRAM -: Neisseria meningitidis & gonorrhoeae, Haemophilus influenzae, Escherichia coli

Term
Explain transduction, does this occur in both gram- & +?
Definition

BOTH gram- & gram+

GENERALIZED: DNA frag carried from donor to recipient in bacteriophage (virus) -> chop up host DNA -> repackage into new viruses

RARELY: host DNA can be formed into virus (transducing virus, not harmful)

SPECIALIZED: specific viral DNA packaged into new viruses (lambda)

Term
Which species undergo conjugation? What does this term refer to?
Definition

Many gram-

few gram+, esp. E. faecalis 

 

fertility plasmid-facilitated tranfer of host chromosome to recipient cell (sex pili via mating bridge)

Term
What is the difference between reassortment and mutation?
Definition

MUTATION: mechanism of genetic DRIFT; frequent occurrence in viruses (<=poor fidelity of viral polymerases/no proofreading & rapid replication rates); subtle changes

REASSORTMENT: mechanism of genetic SHIFT; segmented genomic strains exchanging nucleic acid segments; *only in certain RNA-containing viruses (BOAR)

Term

How is donor DNA transferred to the recipient cell during:

conjugation

transposition

transformation

transduction

Definition

CONJUGATION: sex factors & pili (many gram-)

TRANSPOSITION: jumping genes (on plasmids)

TRANSFORMATION: plasmid (more frequent in gram-, but does occur in S. lactis, E. faecalis, & B. subtilis gram+s) & chromosomal DNA

TRANSDUCTION: viral mediated transfer (generalized & specialized)

Term
Describe the normal flora concept and name some examples:
Definition

Since birth humans are colonized by microorganisms (most commonly bacteria); variable bt/w individuals; perhaps perform symbiotic functions

Ex: 1. breast-fed infants (gram+: Bifidobacterium & Lactobacillus(rods) AND Streptococcus lactis)

2. bottle-fed infants (gram-: Enterobacter)

3. later in life: Bacteroides (predom in gut)

4. UGT: Lactobacillus acidophilus

Term
Which sites of the human body are sterile?
Definition

blood

lymph

CSF

synovial fluid

sub-epidermal tissues

Term
How does the normal flora of an infant reflect its feeding habits?
Definition

Breast-fed: gram+ eg. Bifidobacterium, Lactobacillus, & Streptococcus lactis

 

Bottle-fed: gram- eg. Enterobacter

Term
Which is more common in the colon, Escherichia or Bacteroides; which is easier to culture?
Definition
Bacteroides is more common but more difficult to culture?
Term
Which organism is useful for trying to re-establish a pt's normal flora?
Definition
Lactobacillus
Term
What is the significance of getting positive cultures from blood, CSF, or synovial fluid; what if the organism cultured is Staphylococcus epidermidis?
Definition

positive culture from blood/CSF/synovial fluid => infection

S. epidermidis culture => contamination

Term
Name the 4 types of host-parasite relationships (these are NOT mutually exclusive) and give some examples:
Definition

1. MUTUALISTS (E. coli/Bacteroides/Lactobacillus)

2. COMMENSALS (Micrococcus/Bifidobacterium/Enterobacter)

3. OPPORTUNISTIC PARASITES (S. aureus/ S.pneumoniae/N. meningitidis/Pneumocystis carinii/Mycobacterium avium)

4. PARASITES-not normal flora (Treponema pallidum/Rabies virus)

Term
In what ways do microbes benefit us by their presence in our body (4) & give examples?
Definition

1. OCCUPY COMMON ADHERENCE SITES (gram+s attach to fibronectin)

2. OCCUPY SPACE (loss of normal gut flora incr susceptibility to C. difficile & Salmonella infect)

3. INDUCE CROSS-REACTIVE IMMUNOGLOBULIN (N. meningitidis)

4. CONTRIBUTE TO NUTRITION (Bacteroides & E. coli synthesize Vit K)

Term
Where do most of the agents that infect us come from?
Definition
most are endogenous in origin
Term
Why are hospital patients at greater risk of gram- pneumonia?
Definition
loss of fibronectin in debilitated pts correlates w/ incr gram- pneumonia (more gram- able to reach fimbrial receptors and colonize on oral/pharyngeal epithelial cell surfaces)
Term
What are the concerns for pts on gut-sterilizing antibiotic therapy?
Definition

overgrowth of Clostridium difficile --> gastroenteritis 

AND million-fold decr in Salmonella infectious oral dose

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