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Bacteriology Exam 1
Terms in this set (46)
What are 7 bacterial cellular morphologies?
-Spore forming rod
Give an example of a straight rod.
Give an example of a club shaped rod.
Give an example of a branching rod.
Give an example of a comma form.
Give an example of a spore forming rod.
Give an example of a spiral form.
Give an example of a coccus.
What are 5 types of bacterial cell arrangements?
Coccus (1 round):
-Tetrad (division in 2 planes)
-Cluster (division in 3 planes)
What are the basic constituents of gram stains?
-Decolorizing solution (ethanol:acetone)
How do gram positive cell walls stain?
Retain the staining complex after treatment with alcohol and appear PURPLE
How do gram negative cell walls stain?
Organisms decolorize following such treatment and appear PINK
What is the morphology and staining of staphylococcus?
-Irregular grape like clusters
What is the colony morphology of staphylococcus?
-Golden (S. aureus) -- carotenoid pigments
What are the biochemical characteristics of staphylococcus?
-Carbohydrate -- oxidation, fermentation
-Catalase positive -
differentiates Staph from streptococcus
What resistance does staphylococcus have?
-Withstand drying for weeks (exudates)
-Heating -- 60 C for 30 min
-pH 4 - 9.5
-Salt -- up to 7.5% (used in selective media)
What 2 beta-lactam antimicrobials does staphylococcus use?
-Plasmid exchange among streps + bacilli
What is staphylococcus sensitive to?
Disinfectants (ex: chlorhexidine)
How does innate immunity deal with staphylococcal infections?
-TLR2 (neutrophil) --> direct recognition of staphylococcal lipoteichoic acid (LTA)
-Epithelial/endothelial cells and monocytes --> LTA --> stimulates release of IL-8 --> chemotaxic for neutrophils
How does complement activation + opsonization + phagocytosis occur in response to staphylococcal infections?
-Mannose binding lectin (MBL) + ficolins recognize peptidoglycan + LTA
-Peptidoglycan = direct activator of alternative pathway (C3)
Where is staphylococcus seen on the clinical spectrum?
-Suppuration -- neutrophils
-Enterotoxin-induced disease -- rare (animals)
-Toxic shock syndrome (not seen in animals)
What kind of suppuration is seen with staphylococcus?
-Botryomycosis (uncommon) -- chronic granulomatous infection; neutrophils + macrophages
What kind of CMI is seen with staphylococcus?
-Atopy, hypersensitivity reactions
What staphylococcus virulence factor is involved with attachment?
Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs):
-Fibronectin, fibrinogen, collagen, laminin -- gives affinity to different host tissues (e.g. kidney, bone)
-Polysaccharide intracellular adhesin (PIA) -- S.epidermis, biofilm formation
What staphylococcus virulence factor is involved with colonization?
-Survival in low iron environment
Describe the anatomy of a biofilm.
-Extracellular polysaccharides for capsule formation
What is biofilm resistant to?
-Antibiotics -- sublethal concentrations may actually enhance biofilm formation
-Host immune clearance
How can biofilms cause inflammation?
-Can cause chronic inflammation (e.g. osteomyelitis, otitis media)
-Accumulation of neutrophils -- scaffold for further biofilm formation
What is the Two Stage System of biofilms?
Adhesion --> Maturation Stage:
-Different adhesins for different surfaces
What is quorum sensing?
Bacterial cell-to cell talk -- communicating cell density and population gene regulation
How can staphylococcus use water/fluid as a medium that is clinically relevant?
-IV catheters -- long term catheterization
-Water pipes -- do NOT use tap water for immunocompromised patients
What is an example of a beneficial biofilm?
Aquarium biofilters -- nitrogen-fixing bacteria
How can harmful biofilms be removed?
-Physical disruption -- ultrasonic cleaners + scrubbing
-Chemical or enzymatic disruption
How can harmful biofilms be prevented?
Locking solutions in catheters:
-Hypertonic solutions (e.g. glycerol)
What is coagulase?
-Staphylococcus virulence factor
-Converts fibrinogen to fibrin -- clots plasma in vitro w/minimal role in vivo
-Not a universal virulence factor -- Coag+ tend to be more virulent
What factors allow staphylococcus to have a resistance to phagocytosis as a virulence factor?
How does the polysaccharide capsule contribute to phagocytosis resistance?
-11 serologically distinct capsules
-Anti-opsonic -- reduces uptake by neutrophils
How does the cell wall provide phagocytosis resistance?
-Peptidoglycan + teichoic acid
-Resistant to lysozyme digestion
What surface proteins contribute to phagocytosis resistance?
-Binds IgG Fc region
-Failure of neutrophil recognition
Clumping Factor A (ClfA):
-Binds fibrinogen --> coating
-Blocks access to opsonins
How do extracellular proteins contribute to phagocytosis resistance?
Extracellular firbinogen binding protein (Efb) -- binds C3 -- blocks C3 surface deposition
What are 2 staphylococcus virulence factors that contribute to toxin formation?
How does staphylococcus utilize cytotoxic toxin formation as a virulence factor?
-Binds to cell membrane -- pore formation -- necrosis
-Lyses cells via enzymatic degradation of membrane phospholipids
How does staphylococcus utilize exfoliative toxins as a virulence factor?
-sETA, sETB -- S. aureus
-shETA-C -- S. hyicus
-Serine proteases target intracellular adhesion (desmosomes) in epidermis -- "greasy pig"
What are some examples of staphylococcus scavenging O2 radicals (phagolysosomes) as a virulence factor?
-Superoxide Dismutase (SOD)
-Carotenoid pigment (S. aureus)
-Multiple peptide resistance factor (MPRF)
What are 2 superantigens that are utilized by staphylococcus as a virulence factor?
-Ingestion, preformed heat-stable toxins
Toxic shock syndrome toxin -1 (humans only)
-Resists heat and digestive enzymes
Is staphylococcus aureus gram positive or negative?
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