Block 1 Flashcards
Veterinary diagnostics assist on determining (5) which improves knowledge on (3)
a. Assist on determining:
i. Etiologic agent
ii. Risk of pathogen transmission
iii. Appropriate treatments for infectious diseases
iv. Prognosis of clinical syndromes
v. Preventative and control measures of infectious diseases
b. Improves:
i. Knowledge on pathogens involved in clinical syndromes
ii. Knowledge of pathogens of public importance
iii. Economic losses due to infectious diseases in production animals
Pre-analytical phase of bacteriology and fungal diagnostics include what?
i. Clinical evaluation of the patient
ii. Sample collection, storage, transportation
analytical phase of bacteriology and fungal diagnostics include what?
i. Laboratory processing and analysis
ii. Biosafety levels (BSL)
Post-analytical phase of bacteriology and fungal diagnostics include what?
i. Data reporting and interpretation
ii. Diagnosis and treatment
Types of samples (pre analytic phase) collection of Transudates, exudates, pus, discharges is done by?
Syringe or sterile container
Anaerobic transport medium in anaerobic infection is suspected
Types of samples (pre analytic phase) collection of Lovage or washes is done by?
Syringe, material in saline and LRS
Types of samples (pre analytic phase) collection of Feces is done by?
- 2-3mg in leak proof container
- Repeated sampling for intermittent shedding/chronic
catheterization
Types of samples (pre analytic phase) collection of Urine is done by?
Cystocentesis preferred over catheterization
Or MID STREAM free catch
Types of samples (pre analytic phase) collection of Blood is done by?
- Culture → use appropriate tubes for testing
iv. Urine - Serology→ red top tubes, repeated sampling needed over time
- PCR → EDTA tubes
Types of samples (pre analytic phase) collection of Tissue from necropsy is done by?
- Collect samples for culture first during necropsy
- Collect a good amount of tissue in leak proof containers
- Refrigerate
Adequate transport conditions must be kept to maintain the viability of the microorganism (temp., pH, moisture, oxygen, etc.). Transportation can be in what? (3)
i. Swabs, syringes, sterile tubes
ii. Leak proof sterile containers
iii. Use transport media
b. Be aware of transportation safety and packaging regulations for public transport
Choosing a diagnostic method Depends on: (4)
- Infection type
- Test availability
- Sensitivity and specificity
- Time and costs
Detection of the agent. Direct detection of the bacteria/fungi Staining options include (6)
a. Giemsa/Diff quick → mycoplasma
b. DCF → campylobacter
c. Polychrome methylene blue → Bacillus anthracis
d. Modified Ziehl-Nielsen → Brucella abortus
e. Ziehl-Nielsen → Mycobacterium
KOH, Giemsa → Fungi
Culture media→ contain essential nutrients for growth of
non-fastidious bacteria (for bacteria that grows easily). Examples are (3)
nutrient broth, peptone broth, trypticase soy
agar
Selective media → for growth of only selected bacteria. Examples are? (3)
i. Phenylethyl alcohol agar (PEA) → for Gram +
ii. Mac Conkey agar → for Gram -
iii. Sabourad’s dextrose agar → for fungi
Differential media → distinguish 1 bacteria growing on the
same plate from another. Examples are? (2)
Blood agar → recognition of hemolysin production (differentiates staphylococcus)
ii. Mac Conkey agar → nutrient utilization (lactose fermentation vs. gram neg)
Plate inoculation technique for obtaining isolated pure cultures like Bacterial colony, which is what?
Bacterial colony: visible ma of bacteria all originating
from a single mother cell. Definitive identification of a potential pathogen involves
subculture of an isolated colony to obtain a pure growth
which can be subjected to biochemical or other tests
Results of detection of the agent could be determined by (4)
a. # of colonies isolated (light, moderate, heavy)
b. Accept results = what was expected, known cause,
consistent cytology
c. Don’t accept results = it will be specified why (ex:
contamination, normal microbiota, inflammation)
d. Further information or testing required
What does PCR aid in identifying?
- Aids in identification → tests for DNA
- Conventional (qualitative) → positive or negative
- Real time PCR (quantitative) → gives amount
Detection of microbial components Can be done by? (3)
- Antigen detection: ELISA, agglutination, fluorescent antibody staining, SNAP tests
- Chemical detention: MALDI-TOF → analysis of total protein
- Biological detection: Limulus amoebocyte assay test for LPS of
the bacteria
Detection of host immune response by Serology will detect what? Examples could be? (4)
detection of humoral immunity
1. Ex: agglutination, precipitation, ELISA, immunofluorescence
2. Quantitative → measurement of antibody titer
a. Tells you if the patient has an active infection or not
b. Paired serum titers → compare acute and convalescent
phase samples
i. 4 fold increase in serum titers = infection
c. IgM to IgG conversion for T cell dependent responses
Detection of cell-mediated immunity Example could be?
Tuberculin skin test
a. Tests for bovine tuberculosis
b. Caudal fold test and comparative cervical test
What are some limitations to testing ? (4)
i. Negative microscopy does not rule out infection
ii. Negative result on serology does not discard infection
iii. Positive PCR in a healthy animal does not mean active infection or need to treat
IV. A positive growth on a culture could just be host- associated microbiota
Pros and cons of direct mircoscopy
Pro
-Fast, cost effective (cheap)
-Provides immediate information on number, characteristics, and host response
Con
-Expertise (need to be trained) -Low sensitivity
-Usually cannot identify species
Pro and con of culturing
Pro: gold standard
Con: time consuming 2-10 days, supplies and expertise
Pro and con of PCR
Pro: fast, identifies isolates
Con: +PCR does not always mean active infection or need to treat
Pro and con of serology
Pro: Widely used, rapid test’s available, some useful for chronic and carrier state
Con -False negatives (recent exposure, immunosuppression)
-False positives (vax, cross-reactions, past infection)
Define antimicrobial?
any substance of natural, semisynthetic, or synthetic origin that kills or inhibits the growth of microorganisms/bacteria but causes little or no damage to the host
Define Therapeutic use
when diseased animals are treated to cure infection
Define prophylactic use
: when healthy animals are treated to prevent infection
Define metaphylactic use
when diseases herds are treated to cure infection in
some individuals and prevent infection in others
Growth promotion use
when healthy animals are treated with low (sub-therapeutic) concentrations in feed to improve growth rate and efficiency of feed utilization and improve reproductive performance
Therapeutic use:
Prophylactic use
Metaphylactic use
1. Not a good idea! Promotes resistance!
Define antibiotic. Produced by, function.
chemical substance that is produced by microorganisms and has
the capacity in dilute solution to selectively inhibit the growth or kill other microorganisms
i. Natural products
1. Produced by microorganisms (mainly soil dwelling)
- Function:
a. Communication between microorganisms
b. Killing/inhibition of potentially competitive microorganisms - Very old molecules
All antibiotics are antimicrobials, but not all antimicrobials are antibiotics
Chemical structure of B-lactams
Examples
All contain a beta-lactation ring
Penicillins, cephalosporins
Chemical structure of Aminoglycosides
Examples
All contain amino sugar substructures
Gentamycin, streptomycin
Chemical structure of tetracyclines
Examples
All contain 4 adjacent cyclic hydrocarbon rings
Tetracycline, doxycycline, oxytetracycline
Chemical structure of macrolides
Examples
All contain a 14, 15 or 15-membrane macrolide ring
Erythromycin, azithromycin
Chemical structure of sulfonamides
Examples
All contain the sulfonamide group
Sulfadiazine, prontosil
Chemical structure of (fluoro)Quinolones
Examples
All contain fused aromatic rings. With a carboxylic acid group
Ciprofloxacin, enrofloxacin
Define bactericidal?
Death and disruption of bacterial cell.
Reduce number of viable cells
Preferred for serious and/or life threatening infections or immunocompromised patients
Act on cell wall synthesis, cell membranes and DNA synthesis
Define Bacteriostatic
Inhibit growth and multiplication of bacteria.
Requires the immune system to further clear the infection
Inhibit protein synthesis and pathways
How can we reach the desired antimicrobial effect in the body, at the infection site?
ADME principle of drug delivery
(Absorption, distribution, metabolism, and excretion)
Host factors (age, genetics, pregnancy)
Combination therapy of drugs (increase efficacy, increase spectrum, synergic effect
How can we reach the desired antimicrobial effect inside the body of the host, at the infection side?
Pharmacokinetics/ pharmacodynamics (PK-PD) modeling
MIC - minimally inhibitory concentration.
Narrow-spectrum antimicrobials act against what?
A limited group of bacteria and are used against a particular subset of microorganisms
Broad-spectrum antimicrobials act against what?
A large group of bacteria and are active against both gram-positive and gram-negative organisms
Rational antimicrobial use means what?
It comprises any actions that prevent or minimize development of resistantance in the strain causing infection as well as in the patient’s commensalism microbiota without impacting efficacy
Antimicrobial stewardship means what?
Coordinated interventions/program designed to improve and measure the appropriate use of antimicrobials by promoting the selection of the optimal antimicrobial drug regimen, dose, duration of therapy, and route of administration
Prokaryote:
describe?
how is it like bacteria?
what does it contain?
are there exceptions? what are they?
are they big/small? what is the surface to volume ration? why?
***Prokaryote: smaller, unicellular, lacks nucleus (DNA floats around),
single haploid circular chromosome
* Think bacteria: wide range of morphology
* Contain: ribosomes, cytoplasm, nucleoid (DNA), cell wall
* Exceptions: Leptospira (2 circular chromosomes), Borrellia burgdorferi (linear
chromosome), Mycoplasma (no cell wall)
* Small in size with a large surface to volume ratio so nutrients quickly reach all
parts of the cell
Eukaryote:
describe
what do they contain?
how are the chromosomes arranged?
how do they replicate?
Eukaryote: larger, organelles (mitochondria, Golgi, lysosomes, ribosomes),
linear chromosomes (DNA inside), replicate by mitosis
* Think fungi
Bacteria structures and cell wall
what is the capsul?
what is it associated with?
what does it help with?
Capsule: usually polysaccharide, associated with virulence, helps with survival and attachment
Bacteria structures and cell wall
Cell wall describe?
used for what?
what does it determine?
Cell wall: PEPTIDOGLYCAN, for shape and structure, used to determine if gram pos. or gram neg.
Bacteria structures and cell wall
Cell wall, Gram pos:
describe
does it have an outer membane?
more resistent to what?
what color gram stain?
Gram pos: thick peptidoglycan layer, no outer membrane, lipoteichoic and teichoic acids, strong antigenic properties
* More resistant to drying and disruption
* GRAM STAIN: purple=positive
Bacteria structures and cell wall
Cell wall, Gram neg:
describe:
does it have an outer membrane?
More prone to what?
what color gram stain?
Gram neg: thin peptidoglycan layer, has outer membrane, lipopolysaccharides (aka LPS)
* More prone to drying and disruption (because more lipids)
* Polysaccharide chain: antigenic portion
* Lipid A: endotoxin that will cause toxic effects (harm) and activate immune system
* GRAM STAIN: pink=negative
Bacteria structures and cell wall
All bacteria have this except ?
They have a what?
All bacteria have this except **mycobacterium **(mycolic acid virulence factor) = acid fast stain
* **ACID FAST STAIN: **pink=positive, blue=negative
Bacteria structures and cell wall
Cytoplasmic membrane
what is it?
Cytoplasmic membrane: phospholipid bilayer (very selective membrane)
Bacteria structures and cell wall
Flagella
what is it?
Flagella: motility
Bacteria structures and cell wall
Pilus/pili/fimbriae
explain
what are the 2 kinds called and what do they do?
Pilus/pili/fimbriae: attachment pili (attach to host and invade), conjugation pili (exchange DNA/plasmid)
Bacteria structures and cell wall
Endospore
what are the 2
describe
Endospore (Clostridium spp. and Bacillus spp.): extremely durable dormant state
Bacteria structures and cell wall
In a gram positive photo, name the 3 structures from outside to inside.
are any thick/thin?
Capsule-thick
cell wall-thick
cytoplasmic membrane-thin
Bacteria structures and cell wall
In a gram negative photo, name the 6 structures from outside to inside.
are any thick/thin?
capsule
outer membrane
periplasmic space
cell wall
periplasmic space
cytoplasmic membrane
all thin
Bacteria structures and cell wall
on the slides….
Which one looks like a dark hotdog with a tail?
which one looks like a skinny worm with a tail on both ends?
which one looks like a short white hotdog with all kids of curly tails on one end?
which one looks like a short work with curly tails all over it?
Monotrichous
amphitrichous
lophotrichous
Peritrichous
Bacterial growth
How does it replicate, what is another word for this?
Replication by binary fission (asexual replication)
Bacterial growth
4 phases of growth
what are they?
Lag phase
Exponential/Logarithmic phase
Maximal stationary phase
Decline/death phase
Bacterial growth
4 phases of growth
what happens during lag phase?
Lag phase: increase in cell size but no division