Infectious Disease Intro Pt.2 Flashcards
What are the three ways of diagnosing an infection?
- History
- Physical Examination
- Laboratory Testing
In diagnosing an infection, patient history includes…
What does each tell us in regards to the infection?
a) Signs and symptoms - severity and potentially location
b) source of infection - trauma, contact with another person, etc.
c) try and determine which organism is most likely the cause (if not severely ill, tests not done and go with best guess0
In diagnosing an infection, physical examination includes…
Examples and presentation
- Will be different for each infection, but the GOAL is to localize the infection
a) Measles - characteristic rash
b) Meningitis - neck stiffness
c) pneumonia - cough and sputum production; chest sounds
In diagnosing an infection, laboratory testing may include…. (examples)
- WBC and Differential (differential means with percentages)
- ESR and CRP
- Renal and Hepatic Function –> Need to know to choose an antibiotic. Some antibiotics may cause renal damage and/or decreased hepatic function
- Others - such as electrolytes
- Microbiology
What is the goal of laboratory microbiology testing? What are some examples?
- Goal is to determine invading pathogen(s), so that the proper antibiotic can be used
a) Gram stain
b) Culture
c) Sensitivity testing
What is a gram stain? Purpose?
Quick and easy way to gain an idea of the organism
is it gram + or - ?
cocci vs bacillus
presence of WBC –> they do stain. If no WBC, need to start wondering if just colonization rather than infection
is it even a bacteria?
Not all organisms stain well – Ex. TB
Positive Cocci Clusters
Staphylococci
Coagulase Positive
Coagulase Negative
Coagulase Positive Example
Staphylococcus Aureus
Coagulase Negative Examples
Staphylococcus epidermidis
Staphylococcus saprophyticus
Staphylococcus hominis
Staphylococcus hemolyticus
Staphylococcus warneri
Positive Cocci Pairs (Diplococci)
- Pneumoncocci
e.g. streptococcus pneumoniae
Positive Cocci Chains
Streptococci
a) Beta-hemolytic
- Streptococcus pyogenes
- Streptococcus agalactiae
- Groups C, F, G
b) Alpha-hemolytic
- Viridians streptococci
- Streptococcus pneumoniae
Positive Bacilli Small
- Listeria
- Cutibacterium
- Corynebacterium
- Gardnerella
Positive Bacilli Large
a) Spore forming
- Clostridium
- Bacillus
b) Nonspore-forming
- Lactobacillus
Positive Bacilli Branching or Non-filamentous
- Nocardia
- Actinomyces
- Erysipelothrix
Negative Cocci
- Neisseria Meningitis
- Neisseria Gonnorhea
- Veillonella
Negative Bacilli Lactose-Fermenter
a) Oxidase Positive
- Aeromonas
- Pasturella
- Vibrio
b) Oxidase-negative
- Escheria coli
-Klebsiella spp.
- Enterobacteur spp.
- Citrobacter spp.
Negative Bacilli Non-lactose Fermenter
a) Oxidase-Positive
- Pseudomonas spp.
- Flavobacterium spp.
- Alcaligenes spp.
- Achromobacteur spp.
- Moraxella spp.
b) Oxidase negative
- Proteus spp.
- Proficendia spp.
- Seratia spp.
- Morganella spp.
- Salmonella spp.
- Shigella spp.
- Stenotrophomonas
- Acinebacteur spp. (coccobacilli)
Gram-negative coccobacilli
- Haemophilus influenzae
- Moraxella catarrhalis
Negative Bacilli are commonly found in…
- The G.I. Tract
What is the best method for revealing an organism?
What is determined?
Are all organisms shown?
Laboratory - Culture
- Biochemical profile determined
–> Coagulase + or -
–> Oxidase + or - - Not all organisms grow well
MALDI- TOF MS
Matrix-assisted laser desorption/ionization time of flight mass spectrometry
Vaporizes bacterial samples with laser. This ionizes proteins and other macromolecules. The ‘cloud’ of ionized analyte is separated by mass and charge. This influences the time of flight to a detector which creates a ‘fingerprint’”. The fingerprint is compared to a data base to identify the microorganism
What type of testing determines what type of antibiotics an organism is susceptible to?
- Sensitivity Testing
Define Sensitivity Testing. What is based on?
- Determines which antibiotics the organism is susceptible to
- Based on the minimal inhibitory conc. (MIC)
- The lowest antimicrobial concentration that prevents growth after 24 hours of incubation
What other information should be considered along with sensitivity testing?
Site of Infection and subsequently the penetration of the antibiotic
When a sensitivity analysis is conducted what do the letters S, R, and I mean?
S = Sensitive
R = Resistant
I = Intermediate
In regards to the degree of susceptibility from a sensitivity test, what is actually susceptible?
- Shows the susceptibility of an organism, not the person, to an antibiotic
T/F: Choosing an antibiotic with an S is sufficient for a microbial condition
No
- Need to take into account the site of infection and the penetration of the antibiotic
How is the MIC calculated?
-Minimum Inhibitory Concentration
- Test tube of antibiotics
- Introduce a standard amount of organism and allow for a standard amount of time
- if clear (no turbidity) than antibiotic is working
- If not clear (turbidity) than organism growing
- Disk with an antibiotic on an agar plate
- Antibiotic diffuses out, antibiotic is inhibiting that organism growth
- Sample of organism must come from patient
- Measure the zone of inhibition and that is correlated
The best antibiotic choice is not always the one with the largest zone of inhibition as may need a large dose to reach that amount in the blood stream
What is an E-test?
- The test has a single antibiotic with a gradient of antibiotic dosage
Cloudy Parts = Antibiotic Growing
Clear = Organism not growing
- Not absolute. Can see some growth in the clear.
Immunologic testing is useful when….
When the organism cannot be cultured or treatment has already begun
What is antibody testing? Does it provide a diagnosis?
- Detects the presence of antibodies directed against the pathogen
- Can not tell you when the infection happened, but can help solidify a diagnosis
What does antigen testing detect? What can it detect?
- Detects presence of an antigen in the serum, urine, CSF, etc.
- Bacterial, Fungal or Viral
- Various methods used
- Would tell you if the infection is current
What does PCR detect?
- Polymerase Chain Reaction
- Detects very low amounts of specific DNA in clinical specimens
What can be used to see viruses?
Electron Microscopy
What is the difference between empiric and direct antibiotic therapy?
As pharmacists we want to move from….. to……
Direct –> Antibiotic chosen due to knowing the exact causative organism and susceptibility
Empiric –> An educated guess antibiotic –> DO not know the causative organism
As pharmacists we want to move from empiric to direct when we have information we need.
