Introduction to Medical Microbiology – Flashcards

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)

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)

spores;

prions

mycobacteria

high numbers

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:0.2;m for HEPA filters)

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

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

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;

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

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)

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

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)

minimum bactericidal concentration

usually more concentrated than MIC

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;

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]

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

polyploidy: mixing bt/w same strains

heteropolyploidy: mixing bt/w different strains;

B-bunyaviridae

O-orthomyxoviridae (influenza)

A-arenaviridae

R-reoviridae (rotovirus)

;

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

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

;

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);

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

oftentimes is on a plasmid

1. DNA binds to bact cell surf

2. DNA uptake through cell mem

3. DNA integrated into chrom OR becomes autonomously replicating plasmid

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

;

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

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)

Many gram-

few gram+, esp. E. faecalis;

;

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

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)

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)

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

blood

lymph

CSF

synovial fluid

sub-epidermal tissues

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

;

Bottle-fed: gram- eg. Enterobacter

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

S. epidermidis culture => contamination

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)

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)

overgrowth of Clostridium difficile --> gastroenteritis 

AND million-fold decr in Salmonella infectious oral dose