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62 Cards in this Set
- Front
- Back
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Lab Diagnosis
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1. specimen collection
2. identification of bacteria |
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Which is the most advanced technique of bacteria ID?
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Genomic characteristics
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What is Direct Identification and why do you use it?
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some pathogens cannot be cultured
thus you must use: morphological characteristics serological characteristics genomic characteristics ex. dark field microscopy to ID presence of teponema pallidum |
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Morphological Characteristics
Staining RXNs |
Simple Stains
Differential stains Special Stains |
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Simple Stains
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Methylene Blue
Malachite Green Basic Fuchsin |
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Differential Stains
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Gram-Stain
Acid-Fast Stain |
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Special Stains-specialized structures
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Capsule Stain
Flagella Stain Endospore Stain |
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Growth Characteristics
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-pH
-Temperature -GasPak Jar-no O2 -Candle Jar-limited O2-microaerophiles -antibiotic sensitivity-disk diffusion |
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Biochemical characteristics: hemolysis
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-hemolysis test: plate isolated bacteria on blood agar plate
Results: B-hemolytic: complete lysis of rbc resulting in clear halo around colony Gamma-hemolytic: non-hemolytic Alpha-hemolytic: incomplete lysis of RBC, resulting in a greenish halo around colony |
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Biochemical characteristics: :
Fermentation assay |
-Phenol red carbohydrate broth
-fermentation produces acids from the breakdown of carbohydrate -PR is red at pH> 7, yellow at <7=acid=fermentation -PR indicator of fermentation |
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Biochemical characteristics: coagulase test
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Positive = coagulase = fibrin clot
Mix bacteria culture with kimbrin |
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Biochemical characteristics:
Catalase Test: |
Free radical oxygen detoxifying
Positive = bubbles |
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Serological characteristics
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-Antigen and antibody reaction
-Direct Evidence for a pathogen: using antibodies to detect antigens -Indirect: using antigens to detect specific antibodies in serum EX. Enzyme-linked immunosorbent assay, Western blot, Radioimmunoassay |
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Most advanced and accurate way of determining DNA sequence
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16S ribosomal RNA gene sequencing
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16S ribosomal RNA
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30s small subunit of ribosome is composed of one rRNA molecule (16S) and 21 different proteins(S1-S21)
gene = 1550 bp in length in prokaryotes conserved DNA sequence among bacterial species |
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Labratory diagnosis of pathogens
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-Direct microscope
-Detection of antibodies - ELISA - Detection of nucleic acids -In-vitro nucleic acid amp-->automated dna sequencing + previous -Pure Culture: Morph. Growth Biochemical Serological Genomic |
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Bacteria of Medical Importance
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1. Gram + cocci
2. Gram + bacilli 3. Gram - cocci 4. Gram - bacilli 5. Gram-exceptions -acid fast -intracellular parasite -spiral |
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Taxonomy-Classification
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Species-Genus-Family-Order-Class-Phylum-Kingdom
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Gram Positive Cocci
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-Staphylococci
-Streptococci -Enterococci |
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Gram Positive Cocci Catalase Test, what is positive, what is negative?
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+ Staphylococci clusters
- streptococci(pairs&chains), enterococci(diplococci) |
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Staphylococci
Characteristics? Grows on? kind of pathogen? 3 important species? |
1. Catalase positive, non-motile, faculative(grow both aerobically and anaerobically)
2. Grows on human skin/mucous surfaces 3. opportunistic 4. S. Aureus, S. epidermis, S. Saprophyticus |
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Staphylococci- coagulase test
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+ S. aureus
- S. epidermis, S. saprophyticus |
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Staphylococcus aureus
known for? how is the infection aquired? how to prevent it? |
-Most virulent and best known staphylococcus species->most commonly isolated noscomial pathogen
-healthcare/hopsital aqcuired -wash ahnds |
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virulence Factors of S. Aureus-general
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1. Enzymes
2. Toxins 3. Structural componentts |
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Enzymes of S. aureus
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Careful Cats Hate fucking likeable newborn pandas
1. Coagulase 2. Catalse 3. Hyluronidase 4. Fibrinolysin 5. Lipase 6. Nuclease 7. Penicilinase |
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toxis of S. aureus
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CEET
Cytotoxins Exfoliate toxins Enterotoxin Toxic Shock syndrom toxin-1 |
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Structural components
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Think gram positive GPPT
1. Glycocalyx 2. Peptidoglycan 3. techoic acid 4. Prtoein A |
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Disease associated exofoliative toxins
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SSSS
staphylococcal, scalded, Skin Syndrome |
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Enterotoxin:
type? heat? resistance? disease? Acts as? systemically can lead to? |
1. Exotoxin
2. Heat stable = 100 C 3. Resistant to gastrointestinal enzymes 4. Food poisoning 5. Superantigen 6. toxic shock |
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TSST1
Heat? Resistant to? Systemic effect caused by? acts as? causes? |
1. stable
2. proteases 3. penetrating mucosal barrier 4. superantigne 5. toxic shock |
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SA enzymes: Coagulase
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-converts fibrinogen - fibrin -->prevent phagocytosis
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SA enzymes: Catalase
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-catalyzes removal of hydrogen peroxide
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Hyaluronidase
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-hydrolyzes haluronic acids in CT-->promotes spread
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Staphylokinase(fibrinolysin)
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-Dissolve fibrin clots
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Lipase
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-hydrolyzes lipids-->invade cutaneous/subcutaneous tissues
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Nuclease
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-hydrolyzes DNA; fxn unclear but used to ID SA
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Penincillinase
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-hydrolyzes penicillins; responsible for B-Lactam antibiotic resistance
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Which enzymes are specific for invation
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-hyaluronidase
-staphylokinase -lipase |
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SA - virulence factors
Glycocalyx |
-inhibits phagocytosis, promote bacterial adherence
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SA - virulence factors
Peptidoglycan |
-endotoxin-like activity
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SA - virulence factors-structural
Techoic Acids |
promote bacteria adherence
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SA - virulence factors-structural
Protein A |
only in SA
inhibits antibody-med. immune clearnce via binding to the Fc receptor of IgGs antiphagocytic activity(inhibiting opsonization) |
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S. Aureus Epidemiology
located? special survival conditons? spread? how do infections begin? |
-normal flora on human/mucosal surfaces
-dry surfaces -person-person via direct contact/contaminanted fomites -traumatic inoculation of organisms, cannot get through skin/mucous membrane |
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S. Aureus-diseases
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1. cutaneous infection(most common)
2. toxin-mediated syndromes 3. systemic disease |
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Names of cutaneous infection
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1. impetigo
2. folliculitis-infection of hair follicles -stye at base of eyelid -furuncle boil - extensive 3. carbuncles: multiple furuncles-->spread to other tissues via bacteremia 4. wound infection |
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toxin mediated diseases
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Think toxins + sytemic
1. Food poisoning 2. SSSS 3 Systemic 4Toxic Shock Syndromes |
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TMD: food poisoning
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1. Food poisoning-heat stable enterotoxins
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TMD: SSSS
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SSSS- exofoliatve toxins: disseminated desquamation of epithelium in infants adults
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TMD: TSS
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Toxic Shock Syndrome: TSST-1
-->excessive cytokine production-->fever,rash, shock systemc-->involve multiple organs |
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TMD: Systemic
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-bactermia(spread into blood)-->infection of ANY organ, especially endocaditis and osteomyeltis
-pneuomonia |
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S. Epidermis:
most commonly found on what? virulence factor? Clinical diseases? Common infection? |
-invasive medical devices
-glycoclyx -endocarditis in valve replacement surgery -prosethetic joint |
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S. Saprophyticus
UTI common? usually in? Symptoms? Treatment? |
-young sexually active
-dysuria(pain urination), pyuria(pus in urine) and numerous organisms in urine -respond rapidly to antibiotics and reinfection is uncommon |
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Staphylococci-lab diagnosis
useful for? but not for? |
-direct microscope obervation: useful for pyogenic infections but not blood infections or toxin-mediated infections
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Blood Agar of Staph
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SA: B-yellow
SE: Gamma-hemolytic(non)-white SS: Gamma hemolytic(non)-white |
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Staph Novobiocin sensitivity
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SA-sensitive
SE-sensitive SS-resistant |
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Staph Mannitol fermentation
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SA-yes
SE-no SS-no |
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Mannitol Salt Agar
use: contains: |
distinguish SA from others
high salt-no growth of other micrococcus species Mannitol: fermentation substance Phenol Red: Fermentation pH indicator yellow=acidic red= basic |
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S.a.
colony color? hemolytic? fermentation? Novobiocin sensitive? |
yellow colonies
Hemolytic ferment mannitol Novobiocin sensitive |
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S.e. Lab
colonies? hemolytic? Novobiocin? |
white colonies
nonhemolytic Novobiocin sensitive |
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S.s Lab
colony color? hemolytic? novobiocin resistance? |
white colonies
nonhemolytic novobiocin resistant |
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What are Serological Characteristics,
how are they used? what are examples of their tests? |
antigen-antibody reaction
Direct: antibody detect antigen Indriect: antigen detect antibody in blood EX. WER Western blot, ELISA, Radioimmunoassay |
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All Gram positive cocci use oxygen _____
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faculative
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