Medical Microbiology: Bacteriology I

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Macroscopic (classification)

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Macroscopic (classification)

colony morphology, color, smell

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Microscopic (classification)

shapes, Gram +, Gram -, Endospores, capsule, flagellum, staining

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Phenotypic (classification)

aerobic vs anaerobic, biochemical characteristics, selective growth conditions (temperate, growth media)

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Antigenic (classification)

Direct detection, indirect detection, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), Wester Blot

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Molecular (classification)

polymerase chain reaction (PCR)

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Gram +

thick layer of peptidoglycan

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Gram -

thin layer of peptidoglycan, outermembrane

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Endospores

only gram +, vegetative state, needs signaling to get out

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flagellum

movement

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direct detection

use conjugated anti-target antibody

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indirect detection

use conjugated secondary antibody

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immunoflorescence

microscopic detection of antigens

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enzyme-linked immunosorbent assay (ELISA)

detect pathogen--> active infection Capture --> detect presence of particular antigen antibody detection --> start with antigen to detect antibody quick test

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Western Blot

each band represents a different viral protein often used to confirm ELISA results if you have known antibodies --> use to detect virus look at immune responses

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Polymerase chain reaction (PCR)

amplify particular sequence of DNA mimicking primer and DNA replication can use for detection, sequencing (mutations), and RFLP analysis

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If sequence is present in PCR...

amplification

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If sequence is NOT present...

no amplification

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Restriction fragment length polymorphisms (RFLP)

enzymes come from bacteria and recognize and cut DNA sequences to get particular patterns DNA only (can be PCR product DNA) DNA digestion with restriction enzymes producing DNA patterns

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Transformations (mechanism)

[Acquisition of foreign DNA] donor cells --> cell lysis --> DNA enters the recipient cell and integrates into DNA

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Transductions (mechanism)

[Acquisition of foreign DNA] transducing phage containing donor genomic DNA --> cell lysis --> phage infects recipient cell; donor integrates into recipient DNA

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Transpositions (mechanism)

[Acquisition of foreign DNA] moving and relocating in genome uses transposon with inverted repeats

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Conjugation (mechanism)

[Acquisition of foreign DNA] free plasmid moves from donor to recipient cell via sex (F) pilus integrated plasmid (episome) promotes transfer of genomic DNA, which integrates into recipient DNA

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Capsule

produced outside cell; slippery so things can't bind or penetrate no opsonization, no MAC, no phagocytosis

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Biofilm

grow into giant, multicellular structure that surrounds pathogen

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Spores

inert object is protected from the immune system and antibiotics until signaled almost impossible to get rid of

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proteases

destroy host proteins

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variable surface proteins

antigenic variation

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Adhesion

bind to receptors (proteins, sugars) on the surface of target cell

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Endotoxin

part of the pathogen structure Ex: LPS on Gram -

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Exotoxin

product produced and released by the pathogen Ex: A-B

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Superantigens

trigger over release of cytokines by CD4+ T cells

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Intoxication

large quantity of toxin taken in; immediate effects

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Infection

accumulation of toxin in infected individual; slower effects

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Bacteriostatic agent

prevent growth (put in stasis) Ex: fridge/freezer

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Bactericidal agents

destroy bacteria Ex: cleaning wipes, bleach, detergents

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Step 1 of Koch's Postulate

Bacteria must be present in every case of the disease

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Step 2 of Koch's Postulate

Bacteria must be isolated from host with disease and grown in pure culture

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Step 3 of Koch's Postulate

specific disease must be reproduced when a pure culture of the bacteria is inoculated into a health susceptible host

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Step 4 of Koch's Postulate

bacteria must be recoverable from the experimentally infected host

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Antibiotics

disruption of cell wall; inhibition of protein synthesis; inhibition of nucleic acid synthesis; antimetabolite

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CD8+ T cells

Capsules cannot protect bacteria from which of the following?

-CD8+ T cells -Opsonization via antibodies -Opsonization via complement proteins -Destruction via the membrane attack complex

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Detergents

Which of the following would not be an example of a bacterial static process?

-Freezing -Refrigeration -Detergents -Using antibiotics that prevent the synthesis of new cell walls

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All of the other answers can be used to protect a bacterial pathogen from

Which of the following are mechanisms by which bacteria can protect themselves from immune responses?

-Biofilm formation -Spore formation -Encapsulation -All of the other answers can be used to protect a bacterial pathogen from immune responses.

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Operons

Which of the following is not a mechanisms that allows bacteria to take in foreign DNA?

-Transduction -Conjugation -Operons -Transformation

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All of the other answers can be used to help identify a bacterial pathogen.

Which of the following observations can be used to help identify a bacterial pathogen?

-Antigenic -Phenotypic -Molecular -Microscopic -All of the other answers can be used to help identify a bacterial pathogen.

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ELISA

Antibodies can be used to help identify a bacterial pathogen in which methods?

-PCR -ELISA -RFLP analysis -All of the other answers use antibodies to help identify a bacterial pathogen.

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The use of DNA as the genetic material**??

Which of the following is not different between human and bacterial cells?

-The composition of the ribosomes -The average size of a cell -The use of a cell wall -The use of DNA as the genetic material

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All of the other answers can be used to help identify a bacterial pathogen.

Which of the following can be used to help identify a bacterial pathogen?

-All of the other answers can be used to help identify a bacterial pathogen. -Selective growth -Enzymatic activity -Aerobic vs anaerobic growth

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normal flora and environment

Where is Staphylococcus found?

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Staphylococcus: Transmission

person to person; fomite

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Often observed with Staphylococcus

disruption of normal flora (makes spaces for new things to grow) insertion of foreign bodies half-life: days to weeks

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Staphylococcus: Immune Avoidance

capsule, biofilm, slime layer, Protein A

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Staphylococcus: Virulence Factor

adhesions (slime layer)

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Staphylococcus: Toxins

cytotoxins endotoxins superantigens

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Staphylococcus: Treatment

Antibiotics --> resistance

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Methicillin-resistant Staphylococcus aureus (MRSA)

What is an example of an antibiotic-resistant form of Staphylococcus?

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Staphylococcus: Control

ubiquitous clean/sterilize medical equipment minimize exposure

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Streptococcus A (S. pyogenes)

strep throat, cellulitis, scarlet fever, necrotizing fasciitis

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Strep A: Transmission

person to person, fomite

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Strep A: immune avoidance

capsule M proteins: Block C3b binding C5a peptidase (S. pyogenes): block inflammation

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Strep A: M&F proteins

adhesion cell invasion (disruption of tight junctions)

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Strep A: exotoxins

enterotoxins (A-B toxins) Superantigens [Ex: streptolysin (lyse RBS) --> hemolytic]

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Strep A: Treatment

antibiotics

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Streptococcus B (S. agalactiae)

neonatal infections, normal flora getting in the wrong place

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Strep B: Transmission

normal flora of vaginal tract (birth) location is the issue

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Strep B: Pathogenesis

In newborns: bacteremia (bacteria in blood) pneumonia meningitis (in brain)

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Strep B: Treatment

antibiotics test women for it

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Strep B: Control

minimize exposure and treatment

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S. pneumonia (pneumonia)

causes infection in the lungs diplococci Control: vaccine against capsule

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normal flora of GI tract

Where is Enterococcus found?

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Enterococcus: Transmission

person to person, fomite

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disruption of normal flora

Enterococcus is often observed...

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Enterococcus: Virulence factors

wide range of growth: aerobic and anaerobic, high salt, broad pH biofilm antibiotic resistance

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Enterococcus: Treatment

antibiotics --> resistance

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Bacillus: Epidemiology

spore forming stable in environment aerosol transmission (anthracis)

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Anthracis (anthrax): Transmission

ingestion (livestock) cutaneous- most common (skin) inhalation

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Anthracis (anthrax): immune avoidance

capsule

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Anthracis (anthrax): toxins

Exotoxin: plasmid encoding 3 genes

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edema toxin

PA + LF = ?

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lethal toxin

LF + EF = ?

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Anthracis (anthrax): Treatment

antibiotics --> resistance vaccination --> toxoid (animals)

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Cereus

bigger problem --> seen in humans a lot

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Cereus: Transmission

ingestion (food born pathogen)

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Cereus: Virulence Factors

exotoxin

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