Compilation POI

8/4/2019 Compilation POI

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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_pneumoniae


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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-overview


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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_membrane


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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


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)


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
http://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Cellulitis#cite_note-0http://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Cellulitis#cite_note-0


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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.html


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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 ;)

cahayadian

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