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POI
1. Describe virulence factors that enable bacteria to cause UTI
Introduction
Virulence factors can be defined as molecules expressed andsecreted by pathogens (bacteria, viruses, fungi and protozoa) thatenable them to infect or cause disease in the host. Bacteria involvedin UTI include E coli, Klebsiella and strep. saprophyticus.
pili / fimbriae Pili be able to bind to specific receptorarchitectures.
Type P pili
P pili mediate the binding of uropathogenicE. coli to a digalactoside receptordeterminant present in the urinary tractepithelium.
Assist to bind to uroepithelial cells
Cause pyelonephritis.
Type 1 pili
Cause cystitis
Type 1 pili are heteropolymericmannosebinding fibers produced by allmembers of the Enterobacteriaceae family.The bulk of the fiber is composed of FimA.
Bind to periurethral and perianal area
polysaccharidecapsules
The capsule is found most commonly amonggram-negative bacteria:
Escherichia coli Klebsiella pneumoniae
Function
1. The capsule is slippery and fragile, preventphagocytosis
2. A capsule-specific antibody may be
http://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Fungihttp://en.wikipedia.org/wiki/Protozoahttp://en.wikipedia.org/wiki/Gram-negative_bacteriahttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Klebsiella_pneumoniaehttp://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Fungihttp://en.wikipedia.org/wiki/Protozoahttp://en.wikipedia.org/wiki/Gram-negative_bacteriahttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Klebsiella_pneumoniae8/4/2019 Compilation POI
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required for phagocytosis to occur.
3. Capsules also contain water whichprotects bacteria against desiccation.
common mnemonic used to remember someencapsulated pathogens is:
"Some Killers Have Pretty Nice Capsules"
Streptococcus pneumoniae, Klebsiellapneumoniae, Haemophilus influenzae,Pseudomonas aeruginosa, Neisseriameningitidis, and the yeast Cryptococcusneoformans.
haemolysins e.g. E coli
lyses erythrocytes-disrupt membrane > poreformation> cell burst
Detected as a zone of clearing around thebacterial colony on an agar plate.
Also cytotoxic to other human blood cells,such as polymorphonuclear leukocytes,monocytes, mast cells and basophils
hemolysins as a way to obtain nutrients fromhost cellsrelease iron into surroundings(normally atlow concentration), allowing bacteria to takeup the free iron
urease e.g. Proteus sp
Urease metabolizes urea into ammonia andcarbon dioxide:
Urea 2NH3 + CO2.
to alkalinize the urine, making it effective inproducing an environment in which it cansurvive.
leads to precipitation of organic andinorganic compounds, which leads to struvite
stone formation. Struvite stones arecomposed of a combination of magnesium
http://en.wikipedia.org/wiki/Phagocytosishttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Desiccationhttp://en.wikipedia.org/wiki/Streptococcus_pneumoniaehttp://en.wikipedia.org/wiki/Klebsiella_pneumoniaehttp://en.wikipedia.org/wiki/Klebsiella_pneumoniaehttp://en.wikipedia.org/wiki/Haemophilus_influenzaehttp://en.wikipedia.org/wiki/Pseudomonas_aeruginosahttp://en.wikipedia.org/wiki/Neisseria_meningitidishttp://en.wikipedia.org/wiki/Neisseria_meningitidishttp://en.wikipedia.org/wiki/Yeasthttp://emedicine.medscape.com/article/439127-overviewhttp://emedicine.medscape.com/article/439127-overviewhttp://en.wikipedia.org/wiki/Phagocytosishttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Desiccationhttp://en.wikipedia.org/wiki/Streptococcus_pneumoniaehttp://en.wikipedia.org/wiki/Klebsiella_pneumoniaehttp://en.wikipedia.org/wiki/Klebsiella_pneumoniaehttp://en.wikipedia.org/wiki/Haemophilus_influenzaehttp://en.wikipedia.org/wiki/Pseudomonas_aeruginosahttp://en.wikipedia.org/wiki/Neisseria_meningitidishttp://en.wikipedia.org/wiki/Neisseria_meningitidishttp://en.wikipedia.org/wiki/Yeasthttp://emedicine.medscape.com/article/439127-overviewhttp://emedicine.medscape.com/article/439127-overview8/4/2019 Compilation POI
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ammonium phosphate (struvite) and calciumcarbonate-apatite.
flagella e. coli
The bacterial flagellum is made up of theproteinflagellin which is arranged in a thickhollow tube.
The bacterial flagellum is driven by a rotaryengine made up ofprotein, located at theflagellum's anchor point on the inner cellmembrane.
The rotation results in movement of bacteria
from urethra to bladder to ureter
Examples of bacterial flagella arrangementschemes. A-Monotrichous; B-Lophotrichous;C-Amphitrichous; D-Peritrichous.
IgA proteases Proteases are enzymes that breakdownproteins. An IgA (immunoglobulin) proteasebreaks down host IgA so that the bacteriacan avoid the hosts immune system.
Prevent adherence of pathogenic bacteria on
the wall of the bladder, thus they can beeasily flushed away during urination.
http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Flagellinhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/File:Flagella.svghttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Flagellinhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cell_membrane8/4/2019 Compilation POI
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2. Common organisms, investigation and treatment of UTI.
Introduction:Urinary tract is the most common sites of infections
25% of women have recurrent UTI at some time of their lifeUTI in men less common but primarily occur after 50 years of age
Commonorganisms
In uncomlicated
80% e coli10-15 % strep saprophyticus
Uncomplicated UTI occur in healthy and nrmal UT
Complicated UTI
50% E coli15% Enterococci12.5% P aeruginosa
UTI in altered host(diabetes,immunocompromised)
Overall, causative bacteria in both complicated anduncomplicated UTI is dominated by E coli.
Investigation Laboratory diagnosis of UTI include
Specimen collection
the usual urine specimen for microbiologicexamination is a MSU sample(mid stream urine)
MSU Prepare sterile specimen container, cotton
wool, water and soap Clean ano-genital area First 5-10mls voided urine is discarded Collection of urine in midstream into sterile
container Send specimen to laboratory immediately
CATHETER in situ specimen
Urine from drainage bag should not be used Withdraw urine sample with a syringe and
needle from sampling port in the draining tubeTransport
Examine within 2 hours of collection Hold at 4C for < 18 hours
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laboratory examination
Microscopic examination white cells
abnormal if > 10 cells/mm3(pyuria)
bacteria red blood cells white cell casts squamous epithelial cells poorly collected specimen(contamination
pyuria without culturable bacteria
Recent treatment of UTI
Organism not culturable on usual bacterialmedia
Chlamydia trachomatis Mycobacterium tuberculosis
Non-infectious causes tumours, stones
glomerulonephritis
dipstick analysis
Leukocyte esterase test indirect test for pyuria
Nitrite test bacteria produce nitrate reductase reduce nitrate in urine to nitrite test for bacteriuria
Quantitative /semiquantitative culture
bacterial count to estimate number of bacteriaper ml of urine
Loop methodcalibrated loop holds 0.001 ml of urine inoculate on media incubate for 18 hours at 37C
colonies counted and identified each colony represent one bacterium
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number of bacteria per ml. of urine =number of colonies
X 1,000(dilution factor)
> 100,000 (105) CFU per ml of urine Indicates infection
Lower counts (>103/ml urine) seen in males,gram-positive bacteria and yeasts infection
treatment Asymptomatic bacteriuriatreatment not recommended except
pregnant women planned surgery or instrumentation renal transplant recipients
Acute uncomplicated cystitis 3 day course is optimal therapy Trimethoprim (Trimethoprim/sulphamethoxazole) Fluoroquinolones
Beta-lactams
Nitrofurantoin
** 7 day course for pregnant women, diabetics andif symptomatic for longer than 7 days
Acute pyelonephritis
mild E.g Women with uncomplicated
pyelonephritis, mildly ill, no nausea orvomiting
oral fluoroquinolones for 10-14 days
severe Intravenous gentamicin + ampicillin or
fluoroquinolone or third generationcephalosporin followed by oraltherapy for a total of 14 days
Admit to hospital
3. mechanisms of antifungal and uses
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Introduction1. In last 30 years, steady increase in incidence. Opportunisticfungal infections rising due to: Widespread use of broad spectrum agents
Immunocompromised states (incl. AIDS) Immunosuppressive and anti-cancer drugs
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Act on cellwallEchinocandins-
-glucansynthaseinhibitorsinclude:Anidulafungin,Caspofungin,Micafungin
Inhibit fungal cell wall synthesis Irreversible inhibitors of 1 3 beta glucansynthase Fungicidal against wide range
Little direct human toxicity
Act on cellmembrane 1
Amphotericin B A polyenemacrolideantibiotic(large cyclicmolecule
Binds to ergosterol in cell membranes Forms a pore in the membrane
loss of intracellular K+ ions, macromolecules High affinity for fungal membranes (ergosterol
Poor oral absorption,i.v. admin, topical,
tissue bound Wide spectrumantifungal agent Systemic infections aspergillus, candida,cryptococcus Resistance reducedergosterol/alteredstructure in membrane
Act on cellmembrane 2
Ketoconazole substitutedimidazole
Inhibit fungal P450 3A enzymes, convertlanosterol ergosterol altered membrane fluidity disruptedmembrane-enzymes inhibition of replication
Synthetic fungistatic broad spectrum Inhibit thetransformation ofcandidal yeast cells intohyphae (invasiveand pathogenic)
Act on cellmembrane 3
Fluconazole
Synthetic fungistatic broad spectrum
Act on cell
membrane 4
Allylaminese.g.Terbinafine
Inhibits fungal squalene epoxidase
decreases ergosterol synthesis & increasessqualene, which isFungicidal
Act onnucleardivision
Griseofulvin
Interacts with microtubules to disrupt mitosis Narrow spectrum,fungistatic Prolonged treatmentfor skin + nail infections
Act on
Nuclear acidsynthesis
- 5-flucytosine
Flucytosine converted to 5-fluorouracil (fungal
cell) Requires cytosine permease to enter cell
Inhibits thymidylate synthetase Inhibiton of DNA synthesis
Synthetic antifungal
agent narrowspectrum Yeast andCryptococcal meningitis
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2. Antifungal is used to treat systemic or superficial infections. Canbe categorised according to the site of actions.
PRINCIPLE OF INFECTION1. Compare infections caused by Staphylococcus aureus to those
caused by Staphylococcus epidermidis. Discuss organism and
host factors that account for these differences.(07)
2. Describe infections caused by Staphylococcus aureus. (resit09)
3. Describe the infections caused by Staphylococcus epidermidis.
Discuss organism and host factors that predispose to these
infections.(09)
Introduction: What are gram positive cocci?
Greek : staphyle = bunch of grapes
kokkos = grain or berry
microscopic appearance
Gram stain shows gram-positive cocci in grape-like clusters
Coagulase-positive : Staphylococcus aureus
Coagulase-negative : Staphylococcus epidermidis
Staphylococcus saprophyticus
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Staphylococcus aureus Staphylococcus epidermidis
Descriptio
n
colonise anterior nares
skin, nasopharynx, vagina
10% to 35% of adults are carriers
higher carriage rates among patients
with type 1 diabetes, IVDU, on
haemodialysis, various skin diseases
and health-care workers
carriers at increased risks for infections
by the colonising strain
coagulase-negative
Gram stain features similar to S.aureus
white colonies on blood agar
no complete haemolysis
most prevalent and persistentspecies on human
skin and mucous membrane(normal flora)
Cultural
characteris
tic
Culture media of choice is blood agar
Grows well aerobically, less well
anaerobically (facultative anaerobes)
Optimal temperature : 37C
Colonial morphology sharply defined, round, convex,
smooth, 1-4 mmdiameter
classically golden-yellow pigmentation variable: yellow to
white complete haemolysis- breakdownof cells around the colony
Selective media is mannitol salt agar
tolerate high salt concentration
ferment mannitol to produce
acid
yellow colonies
Virulence
factor
produces large number of virulence factors1. cell surface proteins
2. enzymes3. toxinscell surface proteins
Protein A
-binds Fc region of IgG and prevents IgG
acting as opsonins
-prevents phagocytosis Clumping factor (bound
coagulase)
-bind to fibrinogen
-clumping when mixed with plasma
Coagulase slide test-add undiluted plasma to saline suspension on
microscope sliderapid clumping
enzymes
Coagulase
-convert fibrinogen to fibrin
-wall of fibrin protects against phagocytosis
Coagulase tube test
-tube with diluted plasma
-incubate 3-6 hours at 37Cdistinct clot
Catalase : converts H2O2 to water and
oxygen
Hyaluronidase : hydrolyses
hyaluronic acid in a cellular matrix of
connective tissue
Staphylokinase : degrade fibrin
adherence to biomaterials by
polysaccharides
production of extracellular slime most important factor in pathogenesis
of polymer-associated infections is
formation ofbiofilm
-multilayer cell clusters embedded in
amorphous extracellular material
-protect against host defence mechanisms
and antibiotics
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other species
4. Describe the infections caused by Pseudomonas aeruginosa.
Discuss organism and host factors that predispose to these
infections.(08)
description Most important member of Pseudomonas species
Microbiological features Gram negative bacilli ( aerobic) Cannot ferment glucose Produces cytochrome oxidase : +ve oxidase test (blue) Produces pigments
Pyocyanin green blue colour
Pyoverdinyellow fluorescence
Virulence
factor
Structure
Endotoxin LPS Extra cellular polysaccharide
-Alginate Pili
Extracellular products Exotoxin A prevent protein sysnthesis Exoenzyme S interfere with DNA Elastase proteolytic activity, breakdown blood vessels Alkaline protease
Pathogenesis
Significant break in first line defences required AttachmentPili, mucoid exopolysaccharide
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Destruction of tissueextracellular products
Increased receptors in Cystic fibrosis patientsDifferent pathogenesisInfections Opportunistic pathogen
Respiratory infection Ventilated pateints
Cystic fibrosis Urinary tract infection Wound infection
ImmunocompromisedBurns
Epidemiology Enviromental pathogen
Water, soil and vegetation May also colonise human GIT
Higher rates in hospital patients
Antibioticsensitivity
Highly resistant to antibiotics
Specific anti-pseudomonal penicillins
-Carbenicillin, Ticarcillin, Pipercillin
-Increasing resitance to these
Specific anti-pseudomonal cephalosporins
-Cefatzidime
-May be used in combination with Aminoglycosides
Quinolones
Carbapenems
-Imipenem
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Measles Rubella
Description Family : paramyxoviridae
Genus : morbillivirus
RNA enveloped virus, helical
symmetry
Important surface proteins =
haemagglutinin (H) protein and
fusion (F) protein, matrix (M) protein
Other important structural proteins =
nucleoprotien (N), large (L) protein,
Phosphoprotein (P) only one serotype
Sensitive to detergents
Acid labile
Infective between pH 5-9
Rapidly inactivated by heat & light
Temperature
4*C 2 weeks
37*C half life 2 hrs
56* C inactivated @ 30 min
Family : Togaviridae - Togavirus
Genus :Rubivirus ssRNA enveloped virus of
icosahedral symmetry
Only one antigenic type
Rapidly inactivated by chemical
agents, low pH, uv light and heat
Clinicalmanifestatio
n
Incubation period : 10 14 daysProdromal stage (early stage) 2-4 days
- miserable, fever(39.2*C), cough,
coryza, conjunctivitis
- Kopliks spots
Exanthematous stage
- maculopapular rash (5-6 days):
Head/ Face and trunk
Infectious from prodromal stage to 3-
4 days after onset of rash
Incubation period : 14 days (range 12-23)Children : prodrome:-mild / subclinical
disease (up to 50%) URTI, transient
erythematous(maculopapular) rash
Adults : rash, lymphnode swelling, joint
pains, URTI, low grade fever
Infectious 7 days before to 4 days
after appearance of rash
Epidemiolog
y
spreads by aerosol droplets and
respiratory secretions
acquired through upper respiratory
tract or conjunctiva
highly contagious (1 case generates
17 to 20 new cases)
occurs world-wide
-Common & often fatal in developing
countries
occurs world-wide
Man - only host
Most common age 4 - 9 years
Endemic in countries with
unsuccessful vaccination programme
Complication Encephalitis-Acute measles post infectious
encephalitis(1/1000 1/5000, 15% fatal)
-Measles inclusion body encephalitis
(immunocomp. > 85% fatal)
-Subacute sclerosing panencephalitis (SSPE)
(rare 1 in 100000 cases)
Respiratory symptoms (mostly ass
secondary bacterial infection)
Giant cell pneumonia (rare, but often
fatal, ass with immunocomp.)
Otitis media (7%) Diarrhea (8%)
Seizures (0.6%-0.7%)
Atypical measles
Arthralgia or arthritis-Adult female up to 70%
-Childrenrare
Thrombocytopenia purpura1/3,000
cases
Encephalitis1/6,000 cases
Neuritis rare
Orchitis rare
CONGENITAL RUBELLA SYNDROME
-The earlier in pregnancy infection occurs,
the greater the risk of extensive permanent
involvement
-Infection may affect all organs
-May lead to fetal death or premature
delivery
-Serverity of damage to fetus depends on
gestational age
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5. Write short notes on the following: (08)
a. Giardia lamblia
b. Measles
c. Rubella
d. Candida albicans
e. Blood cultures
f. Cryptosporidium
g. Aspergillus
Candida albicans Aspergillus
Type of
fungi
Yeast
Unicellular
Round or oval in shape
Reproduction
majority asexual
process of budding
Moulds aka filamentous fungi
Hyphae - branching filaments
Grow by apical extension
Form an interwoven mass
mycelium
Hyphae may be septate or non-septate
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Reproduce by spore production
Description Normal flora in skin, GIT,
female genital tract (20%
population)
Candida albicans
Non-albicans candida(e.g. C. glabrata, C. tropicalis)
Decaying vegetation
Construction
Exogenous infection
Opportunistic infection
A.fumigatusA.flavus
Infections Cutaneous
Warm, moist areas
axilla, groin, perineum
Itchy, red, macular rash
Nail infection - occupational
Skin scrapings, nail, swabs
Treatment
Skin topical azole
Nail oral azole
Mucosal
Discrete white patches on
mucosal surface
Oral
Vaginal
Oesophageal (esp. HIV)
Swab for microscopy and
culture
Treatment fluconazole (oralor topical)
Invasive
Focal or disseminated
Bloodstream infection
(often line-related)
Endocarditis
Endophthalmitis
Hepato-splenic
Intra-abdominal
collectionsTreatment
C. albicans fluconazole
Non-albicans candida
amphotericin B,
caspofungin
Allergic bronchopulmonary
aspergillosis (APBA)
Hypersensitivity reaction
of airways
Hypersensitivity reaction
Asthma, cystic fibrosis
Wheeze, cough, SOB,
fever
Diagnosis aspergillus
antibody detection
Treat with steroids +
itraconazole
Aspergilloma
Fungal ball in pre-existing
lung cavity
Invasive aspergillosis
Immunocompromisedpatients Primary site is lung
Widespread destructive
growth in lung tissue
Invasion of blood vessels
(angioinvasive)
Dissemination to other
sites
(liver, spleen, kidney,
CNS)
Treatment Amphotericin B
Poor prognosis
Lab
diagnosis
Microscopy
Gram stain large
purple round or oval
organisms May see budding
Histopathology branching septatehyphae
Culture CT thorax
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Culture
Grow on most media
Chromogenic media to
identify strain
Germ tube test
positive ifC.albicans
Aspergillus antigen
detection
Blood cultures
Indication routine blood cultures should be performed on any patient
in whom there is a suspicion
of septicaemia or candidaemia
surveillance for infection before the clinical suspicion of infection exists is NOT an indication
Timing obtain as soon as possible after temperature spike or chills
bacteria rapidly cleared from blood
fever spikes follow bacteraemia by 30 to 90 mins
obtain prior to starting antibiotics
if empiric treatment is an emergency, blood
cultures should still be drawn
as soon as possible after institution of antibiotics
Number of
sets
a blood culture set is one aerobic bottle and one
anaerobic bottle
the optimal yield is obtained with two or three sets
> 95% with 2 or 3 blood culture 80% recovery rate with only one blood culture
99% recovery rate with three blood cultures
no more than three blood cultures should be
obtained in any given 24 hour period single sets should not be used
Volume of
blood
cultured
volume of blood cultured is the most important variable in
optimising recovery in adults
number of microorganisms in blood in adults is
small, typically 100 CFU/ml and often >1000
CFU/ml ) each additional ml increases recovery by 3%
recommended volume of blood is critical to
detecting sepsis
8 to 10 ml per bottle
How to take Label blood culture bottles with patient ID
Put tourniquet on above antecubital fossa
Wash hands
Put on gloves
Cleanse antecubital fossa
Remove tops of bottles and cleanse tops with ethyl alcohol Collect 20 mls. of venous blood (less in children)
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Put 10 mls of blood into each bottle
Send to microbiology laboratory
In laboratory One bottle incubated aerobically, one anaerobically
Automatically monitored
If bacteria growing Sample removed from bottle with syringe
Gram stained
cultured
Clinician phoned with result
Investigations and treatment of acute haematogenous osteomyelitis
(AHO) Def: AHO is infection of the marrow of long bone normally occur in
children.occurs days to weeks.
Investigation
o Diagnosis
o X ray changes slow to develop,
o Other diagnostic tools (CTscans,MRI)
o Laboratory diagnosis
o WBC may be normal, ESR increased
o Blood cultures
o Always take in patient with unexplained fever
o Not always positive
o May require needle aspiration
o Especially adults
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Treatment
o Antimicrobial treatment
Flucloxacilin 2g I.V 6 hourly
I.V 2-3weeks
Orally 3-4 weeks
Benzylpenicillin 2.4g I.V, 6 hourly
o If MRSA or penicillin allergy, teicoplanin 12mg
o If Gram negatives or H.influenzae also suspected add
o Cefuroxime - H.influenzae (Child)
o Ciprofloxacin - Other gram negatives
Why inpatients susceptible to HAI? Describe one infectionBecause
Immunocompromised
Pre existing underlying illness
Exposure to pathogens in hospital
Effect of antibiotic treatment
Many organisms gain entry to the body through breaches or evasion
of first line body defences
breaches in epithelial integrity
eg surgical wounds, intravascular cannulas
loss of washing action of body fluids
eg urinary catheter
interference with respiratory defences
eg endotracheal tube
risk of becoming colonised esp
o skin antibacterial R and yeast at hospital
o GIT and oropharynx - multiply antibiotic-resistant gram
negative bacilli unique to hospital
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Eg of one infection
UTI
o Most common: accounts 40% of HAI
o
80% associated with urinary catheter
o 5 to 10% associated with genitourinary manipulations eg.
surgery, cystoscopy
o Pathogens
80% due to gram negative bacilli
Organisms usually from patients own colonic flora
Also bacteria acquired after exposure to hospital
environment and become part of colonic flora
antibiotic resistant
favoured by length of stay and antibiotic use
pathophysiology
o Direct inoculation during catheter insertion
o Migration of periurethral microorganisms to bladder in space
between the walls of catheter and urethra
o Migration along inner lumen of indwelling catheters
o Biofilm formation staph saprophyticus
o bacteria protected from antibiotics and host defence
mechanisms
o bacteria grow at a slow rate and are less susceptible to
antibiotics
catheterisation
o provide site for bacterial growth esp residual urine
o consequences septicaemia and acute pylonephritis
infection is acute pyelonephritis
acute inflammation of renal parenchyma and pelvis
ascending route of infection
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risk factors includes
recognised risk factors for uncomplicated cystitis
anatomical and functional abnormalities of urinary tract,
instrumentation of urinary tract, diabetes,immunosuppression,
complications
Septicaemia
Septic shock
Renal abscesses
Emphysematous pyelonephritis
Emphysematous pyelitis
Papillary necrosis
lab diagnosis
1. urine microscopy (white cell casts), culture and antibiotic
sensitivities
2. blood culture
treatment
mild
oral fluoroquinolones for 10-14 days
severe
Intravenous gentamicin + ampicillin or fluoroquinolone
or third generation cephalosporin followed by oral
therapy for a total of 14 days
Management
Traditionally patients hospitalised and given intravenous antibiotics
Women with uncomplicated pyelonephritis
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mildly ill
no nausea or vomiting
can be treated with oral fluoroquinolones
for 10-14 days
Severely ill patients
Admit to hospital
Intravenous therapy until patient is better and then oral therapy
list types of skin infection that needs to be hospitalised. Describe clinical
presentation, lab diagnosis and treatment of ONE.Types of skin infection
myonecrosis
cellulitis
necrotising fasciitis
cellulitis deep skin infection. It is a diffuseinflammation[1] (indistinct margin)of
connective tissue with severe inflammation of dermal and subcutaneous layers of the
skin. Effects lower 2/3rd of dermis including subcutaneous layer.
Clinical presentation Hot painful area of skin
Usually lower extremities
Indistinct margin
Predisposing conditions
Diabtes mellitus
Venous or lymphatic insufficiency
Microrganisms
Strep pyogenes
Progresses quickly
Staph aureus
Haemophilus influenzae in children
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Lab diagnosis
Blood culture.
Management
o Antimicrobials
Penicillin and anaerobic coverage (clindamycin or
metronidazole)
Mild flucloxacilin to cover staph infection
Severe i.v benzylpenicilin or amoxacilin
o Surgical debridement
o Hyperbaric oxygen may be necessary
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POI (anis)1) Describe ways by which antimicrobial resistance may be
controlled.
Why does antimicrobial resistance arise?
One major factor
-misuse/overuse of antibiotics in hospitals and community
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Resistance to anti-cancer
Decreased accumulation of the drug ( P-glycoprotein)
Decreased uptake of the drug
Insufficient activation
Increased inactivation
Increased concentration of target enzyme
Decreased requirement for substrate
Increased utilisation of alternative pathways
Rapid repair of drug-induced lesions
Altered activity of target (eg. modified enzymes)
Mutations inp53 and over-expression ofBcl-2 genes
Resistance to antiviral drug
Mutations of the gene, DNA polymerase, causes resistance.
Also mutations of the gene Thymidine kinase which activates the
drug Acyclovir, leads to resistance.
Resistance to anti-retro viral drugs has developed due to:
Mutations of the enzyme
Decreased activation of the drugs
Increased viral load due to reduction in immune mechanisms
Resistance to several anti-malarial drugs has developed.
The mechanisms are the following:
Decreased uptake
Increased expression of an efflux transporter (P-glycoprotein
:pumps the drug out of the parasite)
Alternative resistance pathway (mutation of cytochrome b)
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Anti- helminthic drug resistance:
Helminths (worms) drug resistance becoming a problem
Offspring of resistant worms also become resistant
Very little known about the molecular mechanisms
-However resistance to Benzimidazole has developed
due to loss of high affinity binding to b-tubulin
-Resistance to Levamisole and Pyrantel is due to
changes in the structure of the target receptor
a) Control use of antimicrobials
Control of antimicrobials in humans
Prudent prescribing community and hospital
Guidelines
Interventions to change practice
Education public and doctors
Surveillance
Vaccination
Control of antimicrobials in animals
2006 - EU ban on antibiotic use for growth promotion
DAFF
Prescribing guidelines for vets
Animals treated with antibiotics withheld from food chain
for specified period
Record keeping
Residue monitoring of animals and fresh meat
b) Control spread of resistant organisms
Good infection control practice is the responsibility of all
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Hand washing
Isolation (source) or cohort wards
Personal protective equipment (PPE)
Cleaning of clinical equipment
Environmental cleaning
What can we do?
o Wash your hands
o Comply with prescribing guidelines
o Dont prescribe antibiotics for coughs, colds, flu
o Take the advice of your microbiologist or ID
physician
2) Discuss factors that have contributed to the development of
antimicrobial resistance.
Boleh jugak amik notes from above: why does antimicrobial
resistance arise?
Biochemical Mechanisms of Resistance
1. Enzymatic inactivation of the drug
B-lactamases : inactivate penicillins + cephalosporins
Acetyltransferases
Inactivates chloramphenicol (CAT)
Encoded by plasmids
Inducible (only in presence of chloramphenicol, Gram+ve ) or
constitutive (always expressed, Gramve)
phosphorylation / adenylation / acetylation :
Inactivates aminoglycosides
Resistance genes carried on plasmids and on transposons
Found in both Gram-ve and Gram+ve bacteria
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2. Altered drug binding site
Depends on mutation
30S binding site for aminoglycosides (chromosome)
50S binding site for erythromycin (plasmid)
Point mutation of DNA gyrase A for quinolones
Altered RNA polymerase for rifampicin (chromosome)
Mutated B-lactam binding site (PBP) for penicillins (chromosome)
3. Decreased drug accumulation
Inducible membrane protein which promotes energy dependent
efflux of drug from cell- Resistance to tetracyclines in Gram+ve and
Gram -ve (plasmid)
Erythromycin and Fluoroquinolones also effluxed
Recent evidence for inhibition of porin synthesis (plasmid)
Altered permeability due to chromosomal mutations in
polysaccharides - ampicillin
Mutations of envelope components - chloramphenicol, tetracycline
and others
4. Development of alternative resistance pathways
Resistance to Trimethoprim (plasmid directed synthesis of a form
ofdihydrofolate reductase with negligible affinity for antibiotic)
Transferred by transduction
May be spread by transposons
Sulphonamide resistance is plasmid mediated - due to production
of a form ofdihydropteroate synthetase with a low affinity for
sulphonamides but no change in affinity for PABA
o Bacteria causing serious infections can carry plasmids with
resistance to both sulphonamides and trimethoprim
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a) Antimicrobial use in humans
80% community, 20% hospitals
Up to 50% of antimicrobial prescriptions are inappropriate
Development of resistance associated with excessive and
inappropriate use of antimicrobials
b) Antimicrobial use in animals
Half of all antimicrobials produced worldwide are used in
animals predominantly food animals
Treat infection
Prevent infection
Growth promoters
c) Human to human transmission
Hands of healthcare worker
Contaminated clinical equipment
Contaminated environment
3) Briefly view the mechanism of action of anti viral agents.
Antiviral drugs are those medications available or developed to either cure or control viral
infections. They are different from anti-bacterial drugs or antibodies. They act in different ways
depending on the type of infection or virus.
General features of anti-viral drugs Viruses share many of the metabolic processes of the host cell in order to survive and replicate Difficult to find selective agents that target the pathogen solely Generally not killed by anti-microbial agents However, there are some virus-specific enzymes and processes A drug must be more toxic to the virus than the host (ie. favorable chemotherapeutic index) Most anti-viral agents are only effective while the virus is replicating.
Administer ASAP after infection for maximal effect
An antiviral drug will try to inhibit the virus at various stages of the life
cycle of the infection of virus.
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Inhibition of attachment to or penetration of host cells (amantadine,
immunoglobulin)
The before cell entry stage is when the anti-viral will strategize to interfere
with the ability of the virus to enter a target cell by binding with the
receptor molecule that is present in the surface of the host cell. Or it can
bind itself to the proteins of the virus and thus try to destroy it. This is
somewhat a slow process.
Inhibition of Viral Uncoating
The anti-viral sometimes also stops the virus from releasing its proteins and
avoid uncoating.Amantadine, rimantadine (inhibit uncoating). MOA:blocks
viral H+ ion-channel (M2 transmembrane protein), prevents
acidification of virus containing vesicles,prevents uncoating. Resistance:mutation in M2 transmembrane protein
Inhibition of viral genome replication (DNA/RNA)(DNA polymerase, reversetranscriptase)
MOA: blocks synthesis of dGTP, inhibits viral RNA polymerase i.e.
interferes with viral mRNA synthesis. The next stage of the life-cycle that
the antiviral drugs can attack is the viral synthesis. In such a stage, the
antiviral drug will try to avoid the replication of the virus and inhibit it or
interfere in the replication process, thereby controlling the spread of the
virus and the infection. It would inhibit the processes of reverse
transcription, integrate, transcription, translation / antisense, translation /
ribozymes, protease inhibitors.
Inhibitors of Viral Release- Oseltamivir (Tamiflu) (inhibit release)
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MOA: neuraminidase inhibitors - prevent release of budded virus from the
cell. Targets viral neuraminidase active site (highly conserved region). Inhibit
the release phase where the new virus comes out of the cell.
Immunomodulators(interferon)
The last way an antiviral drug can attack the infection can be by
strengthening the immune system of the body by stimulating the
production of antibodies that form the defense mechanism of the body
against the virus.
(http://www.scumdoctor.com/disease-prevention/incurable-diseases/swine-
flu/antiviral-drugs/Mode-Of-Action-Of-Antiviral-Drugs.html)
4) Write short notes on :
All these are anti-bacterial agents.
a) Aminoglycosides
Group with complex chemical structure (3 hexagonal
rings)
Resemble each other in anti-microbial activity,
pharmacokinetics + toxicity
e.g. Gentamicin, streptomycin, amikacin,tobramycin, neomycin + netilmicin
Clinically useful against gram bacteria
MOA
Bactericidal
Binds to the 30S subunitof the bacterial ribosome
alteration in codon : anticodon recognition
misreading mRNA abnormal bacterial proteins.
Penetration through cell membrane depends on
oxygen-dependent active transport minimal action
against anaerobes( X Chloramphenicol).
Enhanced by inhibitors of cell wall synthesis.
P/K
Absorption : Not absorbed in the GIT
Administration : i.v. , i.m. (rare)
placenta, joint, pleura
http://www.scumdoctor.com/disease-prevention/incurable-diseases/swine-flu/antiviral-drugs/Mode-Of-Action-Of-Antiviral-Drugs.htmlhttp://www.scumdoctor.com/disease-prevention/incurable-diseases/swine-flu/antiviral-drugs/Mode-Of-Action-Of-Antiviral-Drugs.htmlhttp://www.scumdoctor.com/disease-prevention/incurable-diseases/swine-flu/antiviral-drugs/Mode-Of-Action-Of-Antiviral-Drugs.htmlhttp://www.scumdoctor.com/disease-prevention/incurable-diseases/swine-flu/antiviral-drugs/Mode-Of-Action-Of-Antiviral-Drugs.html8/4/2019 Compilation POI
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X BBB, cells, eye, secretions, fluids
Excretion : renal accumulates rapidly in renal
failure to toxic levels
S/E Nephrotoxicity
Ototoxicity
Paralysis
b) Fluoroquinolones
Inhibition of DNA gyrase- unwinds double strand
These drugs are selective for the bacterial enzyme
because it is structurally different from the mammalian
enzyme
Rapidly bactericidal
Resistance due to reduced uptake and enzyme affinity
MOA
inhibit topoisomerase 11 (DNA gyrase)
X negative supercoil in DNA
X transcription / replication
Spectrum
Broad spectrum Gram negative orgs: esp. the
enterobacteriaceae (Gram bacilli, E.coli)
Cinoxin and nalidixic acid - Narrow spectrum - UTI
infections
P/K
Administration : p.o., i.v. (Al + Mg antacids interfere
with absorption)
Distribution : wide esp. kidney, prostate + lung.
Ofloxacin BBB (CSF-90% of serum conc)
Pefloxacin BBB (CSF-40% of serum conc)
Metabolism : Hepatic (can inhibit cytochrome P450
enzymes)
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Excretion : liver and renal
S/E
Rare, mild
GIT disturbance
Skin rashes
Arthropathy
CNS headache, dizziness (CNS pathology)
Rare renal impairment, hypersensitivity rxns,
photosensitivity
Important interaction between ciprofloxacin +
theophylline (P450) theophylline toxicity
c) Sulphonamides
MOA
Structural analogue of p-ABA
Sulphonamides compete withp-ABA for the enzyme
dihydropteroate synthetase.
Thus some local anaesthetics (pABA esters) can
antagonise the antibacterial effect of sulphonamides.
Mechanism is to inhibit growth, not kill
bacterostatic
Action negated by presence of pus/tissue breakdown
which contains thymidine and purines which bacteria
use to bypass their need for folic acid.
Resistance (common) due to synthesis of an enzymewhich is insensitive to the drug (plasmid mediated)
P/K
Administration : p.o., i.v. , i.m.
not usually topical due to allergic reactions
(except for silver sulfadiazine-infected burns)
Absorption : good oral absorption with the exceptionof sulfasalazine (used for U.C.)
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Distribution : wide, crosses placenta + BBB
Metabolism : liver
Excretion : kidney
S/E
GIT - nausea, vomiting and diarrhoea
Headache and mental depression
Cyanosis due to methaemoglobinaemia
Hepatitis
Hypersensitivity reactions - rash, anaphylaxis, fever
Photosensitivity reactions
Bone marrow suppression, anaemia, agranulocytosis,
thrombocytosis
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Introducti
on
1. What is endocarditis?Type of infection affecting the innermost layer of the heart muscle which is closest tothe blood inthe heart
2. What is IE?Infection of the endocardium, more specifically on and around the valves due tovarious reasons:Bacterial and Fungal infections.
3. Patho:
Formation~ small non-onfected thrombus on abnormal endo surface
2ndary infection of thrombus with bacteria present in the bloodstream
Bacteria proliferates- vegetation formed on endo surface4. Predisposing factors:
Injecting drug users
Prosthetic valve
5. Causative Agents
Staph Aureus (most common- 40%)
Viridans Streptoc (Strep SMM- Sanguis, Mitis, Mitans)
Streptoc bovis (Normal Colonic Flora)
Enterococci
Coag ve staph >>> prosthetic valve
Gram ves>>> nosocomial~ more common at healthcare assoc venues
HACEK( 5%)
reatment 1. Only given after blood cultures, adjusted with the culture results
Blood culture procedure: Most important lab test.
3 samples of blood collected within 24 hours before anti microbial therapy isadministered
Isolation of the causative organism essential so that antibiotic susceptibility
tests can be performed & optimum therapy is prescribed
2. Undergo appropriate antimicrobial therapy3. If not, undergo valve repair/ valve replacement
ntimocrob
l
rophylaxis
1. Prolonged course, minimum 4-6 weeks, all intravenous2. Antibiotic treatment regimen IE- depends upon susceptibility of the infecting
organism3. Patients ( good history of penicillin allergy): ceftriaxone/ vancomycin4. Enterococci/ Organisms more resistant to penicillin: Combination of penicillin
(ampicillin) +5. an aminoglycoside (however vancomycin dont respond well)6. Staph Endocarditis (particularly prosthetic valve Endoc) : B lactamase stable
penicillin s/a nafcillin7. + an aminoglycoside8. Methicillin resistant staphylococci/ Penicillin allergic patients : glycopeptides
a/biotics: vancomycin
9. Drugs according to presentation-
Acute - Flucloxacillin + Gentamicin
Indolent - Benzylpenicillin + Gentamicin
Intracardiac Prosthesis/ Penicillin Allergy/ Suspected MRSA Vancomycin, Rifampicin
+ Gentamicin(Gentamicin given divided daily dose, eg: 1mg/kg 8-hourly)
onclusion 1. Various treatments available in treating IE2. However the mortality of IE is 20-50% despite the treatment with antibiotics3. But the most important thing- to do thorough investigation in identifying the
underlying4. causes of IE so treatment is feasible,
inshaAllah hehehe
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Crystallisation in the renal tract CRYSTALLURIA
precipitation of acetylated metabolites in the urine
Stevens-Johnson Syndrome - erythemia multiforme,
skin + mucus membrane lesions +/- systemic illness.
STOP medication or Fatal
Kernicterus risk esp in premature infants. Displaces
bilirubin from albumin binding site encephalitis
Increased activity by methotrexate/warfarin (displaced
from albumin)
Principles of infection. Due : Tuesday 20th1. Discuss treatment and antimicrobial prophylaxis ofinfective
endocarditis.(07)
2. Describe how you would investigate a patient with suspected
infective endocarditis. Comment on diagnostic tests and criteria.
(08)
3. Discuss the investigation and treatment ofinfective endocarditis.
(resit09)
4. Discuss the investigation and treatment ofvalve endocarditis.(09)
5. Discuss the indications for using molecular techniques in the
diagnosis of infection. Describe ONE of these molecular techniques.
(07+resit09)
Discuss treatment and antimicrobial prophylaxis ofinfective
endocarditis.(07)
Patient Group Major etiologic agents of IE
Native Valve 1. Oral strep & Enteroc2. Staph Aureus3. Coag ve staph (epid)4. Gram ve rods5. Fungi (mainly Candida)
IV Drug Misuser 1. Staph Aureus2. Oral Strep & Enteroc3. Gram ve rods4. Fungi5. Coag ve staph
Prosthetic valve (early) 1. Coag ve staph2. Staph Aureus3. Gram ve rods4. Oral Strep & Entero
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5. Fungi (mainly Candida)
Prosthetic valve (late) 1. Oral Strep & Entero2. Coag ve staph3. Staph Aureus4. Gram ve rods
5. Fungi (Candida)
Describe how you would investigate a patient with suspected infective endocarditis.
Comment on diagnostic tests and criteria.(08)
Introduction The Intro to IE as above But you can change it into:
The epidemiology of IE ~
Anually, 3.6/100000 cases
Male> Female
Disease of the Elderly (like Farah
:P) ~ 50% of the cases in thoseaged >60 years
It can be acquired in communityor healthcare associated
Mortality rate is quite high- 11-26%
How to Diagnose IE Based on these sequences:
1.History taking
2. Examination of the: cardiac, skin,
neurological function, fundi, digits
3. Blood cultures are taken before a.biotics!
- 3 set over 24 hoursIf unwell, over 1 hour
Lab tests
Echocardiogram: 2 forms TOE/ TTE
TOE- Transoesophageal Echocardiogram
Probe over chest: rapid/ noninvasive
Colour DopplerEchocardiography
Excellent Specificity:
Vegetations 98% Overall Sensitivity for
vegetations
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Evaluation- complications
Planned surgical intervention
Dx- Duke Criteria Definite:
Pathological
Culture of microbes Histological examination
(embolus/ vegetation)
Clinical
2 major criteria
1 major 3 minor
5 minor
Possible:
1 Major 1 minor
3 minor
Major Criteria (yeap its spongebob )
Blood culture +ve for acharacteristic org/ persistent +vefor unknown org
Echocardiographic identificationvalve related/ implant relatedmass/ abscess
New valvular regurgitation
Minor Criteria Predisposing heart lesion/IV Druguse
Fever
Vascular lesions inc Janewaylesions, haemorrhage, emboli,septic infarcts
Immunological phenomena incGnX/Osler nodes, Roth Spots,Rheumatoid Factor
Microbiologic Evidence (1 timeunknown org)
1. Discuss the investigation and treatment ofvalve endocarditis.(09)
Introduction 1. What is Valve Endocarditis?2. The inflammation of
endocardium particularly atthe valve.
3. Valve endocarditis can bedivided into native andprosthetic, and prosthetic canbe divided into early and late
4. Causes for each of thiscategory, please refer above
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Investigation and treatment Same as above
1. Discuss the indications for using molecular techniques in the
diagnosis of infection. Describe ONE of these molecular
techniques.(07+resit09)
Introduction 1. The importance of moleculartechniques in detecting viralinfections and monitoringdisease status inpatients onceinfection is established
2. Use of Molecular Techniques
Confirmatory test- When serological methods are
positive
Diagnostic tool if other techniquesare not available- Frontline for new viruses
Quantification method formonitoring disease progression- How much virus have infected?
How many are they in blood?
Drug resistance profiling- Eg. HIV
Genotype identification- Crucial- to find the most
appropriate treatment
Molecular techniques do notindicate viability
One type of molecular techniques Polymerase Chain Reaction
Intro on PCR- Amplification of
DNA genetic information The ingredients needed are:1. Primers- Forward and Reverse
20-25 nucleotides (A C G T)2. Target DNA/ RNA (by
commercial kits)3. Deoxynucleoside Triphosphate
dATP, dTTP, dCTP, dGTP4. Taq Polymerase: Thermo stable
The Temperature Cycling PCR:1. Denaturation : Heating
separates the two strands @
95 deg2. Cooling (50-65 deg) allows
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primers to anneal3. Primer Elongation (72 deg) by
TAQ which manufacturescomplementary strands of DNA
Penerangan skema ;) The short oligonucleotide
primers hybridizes with thenucleotide sequences oncomplementary strands at eachend of the DNA fragment to beexpanded
These, together with with aheat-stable polymerase,produce rapidly increasingnumbers of fragmentsconsisting of the sequence to be
amplified , after several cycles,millions of copies can beobtained
Types of PCR1. Nested PCR: (Example, for the
detection of herpes simplexvirus HSV)
Modification of the normal PCRby which DNA of interest isamplified first with two primers
which recognizes sequencessome distances apart and thenin a second reaction, with afurther pair of primers whichrecognizes sequences withinthe length of DNA amplified inthe first pair.~ Consists of outer and innersets of primers~ Increase sensitivity &specificity
~Low copy number of target~ BUT increase risk ofcontamination
2. Real Time /PCR-used forQuantification~Using RNA template---Hepatitis C, HIV~ Use reverse transcriptaseenzyme- converts RNA to DNA~ The DNA then used for PCR
~ RNA extracted fromspecimen
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~ Incubate with RT/ OligodTprimer
3. PCR (Endpoint Detection)
Pros: +ve/-ve result
Easy to design
Rxn components are cheap
No requirements for specializedequipment
Cons:
No quantification due to plateaueffect
Inactiv of TAQ Polymerase
Efficiency of denaturationreduced
Reduction of primer efficiency
Conclusion Can include the procedures which we can
use to minimise contamination:
Highly trained staff &meticulous lab procedures
Physical separation pre & postamplifications
-ve & internal controls
Aerosol barrier pipette tips
Sekian itu sahaja dari saya ;)
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