Advanced Microbiology - Tests and Treatments Flashcards
Specific symptoms for infection
Resp, CNS, skin and soft tissue, urogenital
Resp = cough CNS = neck stiffness SST = redness and swelling URO = dysuria
Non specific infections symptoms (6)
Temp >38 night sweats and chills Fever Rigor/ shaking confusion dehydration
Infection signs in a Full blood count (FBC) (2)
Chronic?
Acute? - Bacterial = ? and Viral = ?
Hb - haemoglobin drop due to aneamia in chronic disease
WCC - white cell count = elevated in infection BUT drop in sepsis
Neutrophils = bacterial
Lymphocytes = viral
Inflammatory markers in serum samples + levels (2)
C reactive protein <5 mg/l
Procalcitonin <0.5 um/l
Chest Xray - use?
Respiratory infections
Blood lactate and gasses use?
used to monitor severe sepsis
How do HCP identify the pathogen (4)
Use history = most common cause
Culture - ID, typing and sensitivity to antiBs
Direct detection - whole organisms or part of (antigens or DNA) by microscopy + staining
Immunological tests - Body’s immune response so indirect (antibodies)
Culturing process (3)
Obtain (aseptic), incubate - growth detection
Gram staining and Morphology (cocci, bacilli, chains or groups) under light microscope
Agar plate incubation for sensitivity testing (don’t grow around AntiB it is sensitive to) = which AntiB + dose.
MALDI-TOF MS
Rapid technique to ID pathogen
Direct detection Vs Culturing
DD is: Quicker + less labour intensive All organism (culture and non culturable)
Culturing - sensitivity testing allows targeted therapy to be applied
Direct Detection examples - for what organisms, type of samples? CSF, sputum and blood
PCR
Viral = Influenza
Bacterial = Strept pneumoniae
Fungal = Candida spp and aspergillus spp
CSF, sputum and blood
Seroconversion (Part of immunological test)
Change from negative to positive antibodies
ONLY possible if two samples are taken from same patient: acute (during infection) and convalescent (after)
Retesting for infection?
Only if symptoms change
Local vs general infection testing
Local = sample/ swab from the affect area General = bloods and blood cultures for sepsis
Meningitis tests
Lumbar puncture an cultures CSF
Bloods - cultures
In immunosupressed = PCR for TB
Lumbar puncture results - variation in opening pressure normal = 5-20 cm of H2O (viral, bacterial and fungal or V, B, F)
viral - normal
Bacterial - Increase
Fungal - Variable
Lumbar puncture results - Appearance (normally clear) VBF?
Viral = clear Bacterial = turbid Fungal = variable
Lumbar puncture results - WBC count (normally <3 x10^6/l)
Viral = <1000 bacterial = >500 Fungal = variable
Lumbar puncture results - Protein (normally 0.2 - 0.5 g/l)
Viral = <1 Bacterial = >1 Fungal = <0.5
Lumbar puncture results - Glucose ratio CSF: Blood (normally 0.6)
Viral = more in CSF >0.6 Bacterial = less in CSF <0.4 Fungal = less in CSF <0.4
Encephalitis tests
CSF + viral PCR
ENT infection tests - for specific conditions
Otitis Media = swab pus if perforated eardrum
Otitis Externa = swab ear canal
NOTE: mixed with normal skin flora
Pharyngitits = throat swab
Respiratory tract infection tests:
Nose and throat swabs - influenza for those vulnerable, or at risk of transmission
CURP test for pneumonia
high = sputum and blood culture
TB vaccination screening tests
Mantoux skin test
IGRA - iterferon G releasing assay (blood)
TB + pulmonary symptoms tests
Sputum culture or PCR
Skin and soft tissue infection test
Wound swabs - impertigo, cellulitis, erysipelas and diabetic foot IF skin is broken and signs of infection
Clean margin sample - post surgery/ amputation in Necrotising fascitis and diabetic foot
Urine sample - infection markers
WBC, RBC, epithelial cells - cultures and specificity
Kass criteria for significant bacteruria
Infectious diarrhea tests?
Stool sample - give history so lab can ID viral, bacterial or parasitic cause
Parasite suspected = 3 samples
H.Pylori tests = 4 - stop PPIs before testing
Antibody testing -
Antigen stool testing - inexpensive
Urea breath test = gold standard
Biopsy of colon + urease test
Test of Cholangitis (5)
Bloods, blood cultures, CT, aspiration cultures
Endocarditis
bloods - special condition
Other? (2)
3 blood samples at different times of the day
Electrocardiogram
Seology for rare and fastidious bacteria
PCR for valve replacements
Hepatitis and syphilis tests
PCR and serology
Antibodies signify (serology)
Infected currently (igM) or ever previously infected (IgG)
Antigens signify (serology)
current infections (but negative result can mean infection is still present)
PCR detects
RNA and DNA of living or dead parts of pathogen - signifies current infection
Hep A serology
Feacal
Antigen - HAV
IG - anti-HAV
Hep C Serology
Antibody remains life long in chronic disease and carriers
Negative = cleared infection
Hep B serology
Antigen = chronic or acute infection Ig = long term chronic
What can help you determine what organism most likely caused the infection? (4)
body site
Immunological status
microbiology history
risk factors
Aspects of pharmokinetics to consider when prescribing anti-microbials
distribution
interactions
adverse effects
Gram negative means
Bacterial have two cell walls
Eukaryotes DNA is?
separate from the cytoplasm eg. in a nucleus
Antibiotics VS antimicrobial agents
AntiB = chemicals produced by microbes (usually fungi) to kill other microbes
Antimicrobial agents = AntiBs, antifungals, Anti-virals - synthetic
different aspects of antimicrobial agents (4)
Activity
Spectrum
toxicity
Pharmcological properties
Static (Eg. bacteriostatic)
Prevent protein synthesis/ growth of pathogen –> allows immune system to kill it
cidal (eg. bacteriocidal)
Kills the cells (eg. cell wall lysis)
Minimum inhibitory concentation (MIC)
min conc of antimicrobial where visible growth is inhibited
Minimum bacteriocidal concentration (MBC)
min conc of antimicrobial where most of the organism are killed (in human depends on about available at site)
Low MIC
<01.mg/L = Sensitive organism
Synergism for antimicrobials
Activity of two together is greater then the effect of one
antagonism for antimicrobials
one agent diminishes the effect of another
Indifference for antimicrobials
neither agents have an affect on the other
Antimicrobial spectrum -what?
Broad = what kind of treatment Narrow = what kind of treatment
range of pathogen sensitive to an antimicrobial agent (AMA)
Broad = kills most - empirical therapy
Narrow = kills a specific few - targeted therapy
Peptidoglycan
Compontent of cells walls that are a target for antibiotics
Synthesis Inhibitory agents
B-lactams and glycopeptides
Types of B-lactams
Penicillin
Cephalorsporins
Carbapenems
Monobactams
Effect of B-lactams
interfere with transpeptidases that crosslink peptidolycan = cell wall lysis