Infectious Diseases Notes

7/28/2019 Infectious Diseases Notes

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1.Supportive therapy is the mainstay of treatment in Cryptosporidium diarrhoea2. Antiviral agents

Aciclovir

DNA polymerase

Ribavirin

RNA viruses

Interferons

release

Amantadine

of virus in cell

Anti-retroviral agent used in HIV

Nucleoside analogue reverse transcriptase inhibitors (NRTI)

Protease inhibitors (PI)

virus able to survive outside the cell

Non-nucleoside reverse transcriptase inhibitors (NNRTI)


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3.Chickenpox exposure in pregnancy - first step is to check antibodies

4.Chlamydia - treat with azithromycin or doxycycline

5.Legionella pneumophilia is best diagnosed by the urinary antigen test

6.URTI symptoms + amoxicillin --> rash ?glandular fever=IMN

7.A rash develops in around 99% of patients who take amoxicillin whilst they

have infectious mononucleosis

8.Hepatitis B serology

Interpreting hepatitis B serology is a dying art form which still occurs at regular

intervals in medical exams. It is

important to remember a few key facts:

o appear and causes the production

of anti-HBs

-6 months)

Infective)


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-HBs implies immunity (either exposure or immunisation). It is negative in

chronic disease

-HBc implies previous (or current) infection. IgM anti-HBc appears during

acute or recent hepatitis B

infection and is present for about 6 months. IgG anti-HBc persists

ore antigen from infected liver cells as is

therefore a marker of

infectivity

Example results

-HBs positive, all others negative

-HBc positive, HBsAg

negative

evious hepatitis B, now a carrier: anti-HBc positive, HBsAg positive

9.Lyme disease is caused by the spirochaete Borrelia burgdorferi and is spread by

ticks

Features

art block, myocarditis

Investigation


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Management

-Herxheimer reaction is sometimes seen after initiating therapy: fever,

rash, tachycardia after first

dose of antibiotic (more commonly seen in syphilis, another spirochaetal disease)

10. Meningitis: causes

0 - 3 months

us (most common cause in neonates)

3 months - 6 years

6 years - 60 years

> 60 years


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least until the patient is 16 years of age, although the majority of patients are

usually put on antibiotic

prophylaxis for life

*usually from dog bites

13.Mucocutaneous ulceration following travel? - Leishmania brasiliensis

14.HIV - multiple ring enhancing lesions = toxoplasmosis

15.HIV: neurocomplications

Generalised neurological disease

Encephalitis

oedematous brain

Cryptococcus


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meningitis is typical presentation but may occasionally cause a space occupying

lesion

Progressive multifocal leukoencephalopathy (PML)

onset : behavioural changes, speech, motor, visual

impairment

better - high-signal

demyelinating white matter lesions are seen

AIDS dementia complex

tself

Focal neurological lesions

Toxoplasmosis

rowsiness

Primary CNS lymphoma


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-Barr virus

ingle or multiple ring enhancing lesions

Differentiating between toxoplasmosis and lymphoma is a common clinical

scenario in HIV patients. It is clearly

important given the vastly different treatment strategies. The table below gives

some general differences. Please

see the Radiopaedia link for more details.

Toxoplasmosis Lymphoma

Multiple lesions

Rng or nodular enhancement

Thallium SPECT negative

Single lesion

Solid enhancement

Thallium SPECT positive

Tuberculosis

or primary CNS lymphoma

16.Osteomyelitis

Osteomyelitis describes an infection of the bone.

Staph. aureus is the most common cause except in patients with sickle-cell

anaemia whereSalmonella species predominate.


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17.Osteomyelitis

Osteomyelitis describes an infection of the bone.

Staph. aureus is the most common cause except in patients with sickle-cell

anaemia whereSalmonella species

predominate.

Predisposing conditions

ckle cell anaemia

avenous drug user

Investigations

-100%

Management

if penicillin-allergic

18.Bacterial vaginosis - overgrowth of predominately Gardnerella vaginalis


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19.Start anti-retrovirals in HIV when CD4 < 350 * 10 .HIV: anti-retrovirals

Highly active anti-retroviral therapy (HAART) involves a combination of at least

three drugs, typically two

nucleoside reverse transcriptase inhibitors (NRTI) and either a protease inhibitor

(PI) or a non-nucleoside reverse

transcriptase inhibitor (NNRTI). This combination both decreases viral replication

but also reduces the risk of viral

resistance emerging

Nucleoside analogue reverse transcriptase inhibitors (NRTI)

-effects: peripheral neuropathy

ls

ine: pancreatitis

Non-nucleoside reverse transcriptase inhibitors (NNRTI)

-effects: P450 enzyme interaction (nevirapine induces), rashes

Protease inhibitors (PI)

inavir

-effects: diabetes, hyperlipidaemia, buffalo hump, central obesity, P450

enzyme inhibition


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P450 system

21.Optic neuritis is common in patients taking ethambutol

22.Congenital rubella

23.Intramuscular human tetanus immunoglobulin should be given to patients

with high-risk wounds (e.g. Compound

fractures, delayed surgical intervention, significant degree of devitalised tissue)irrespective of whether 5 doses

of tetanus vaccine have previously been given

24.Which one of the following is true regarding linezolid?

A. Active against both MRSA and VRE (Vancomycin-Resistant Enterococcus)


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25.Linezolid

Linezolid is a type of oxazolidonone antibiotic which has been introduced in

recent years. It inhibits bacterial

protein synthesis by stopping formation of the 70s initiation complex and is

bacteriostatic nature

Spectrum, highly active against Gram positive organisms including:

-resistant Staphylococcus aureus)

-resistant enterococcus)

Adverse effects

g)

26.Cellulitis: management

The BNF recommends flucloxacillin as first-line treatment for mild/moderate

cellulitis. Clarithromycin or

clindamycin is recommend in patients allergic to penicillin.

Many local protocols now suggest the use of oral clindamycin in patients who

have failed to respond to

flucloxacillin.

Severe cellulitis should be treated with intravenous benzylpenicillin + flucloxacillin


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27.Clostridium difficile

Clostridium difficile is a Gram positive rod often encountered in hospital practice.

It produces an exotoxin which

causes intestinal damage leading to a syndrome called pseudomembranous

colitis. Clostridium difficile develops

when the normal gut flora are suppressed by broad-spectrum antibiotics.

Clindamycin is historically associated

with causingClostridium difficile but the aetiology has evolved significantly over

the past 10 years. Second and

third generation cephalosporins are now the leading cause of Clostridium difficile.

Features

Diagnosis is made by detecting Clostridium difficile toxin (CDT) in the stool

Management

-line therapy is oral metronidazole for 10-14 days

used

-threatening infections a combination of oral vancomycin and

intravenous metronidazole should be

Used


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28.Cardiac involvement is the leading cause of death in patients with Chagas'

disease

29.Scabies

Scabies is caused by the mite Sarcoptes scabiei and is spread by prolonged skin

contact. It typically affects

children and young adults.

The scabies mite burrows into the skin, laying its eggs in the stratum corneum.

The intense pruritus associated

with scabies is due to a delayed type IV hypersensitivity reaction to mites/eggs

which occurs about 30 days after

the initial infection.

Features

wrist

Management

-line

-line


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-6 weeks post eradication

Patient guidance on treatment (from Clinical Knowledge Summaries)

ical contact with others until treatment is complete

even if asymptomatic

treatment to kill off mites.

The BNF advises to apply the insecticide to all areas, including the face and scalp,

contrary to the manufacturer's

recommendation. Patients should be given the following instructions:

n

creases of the skin such

as at the wrist and elbow

-12 hours for permethrin, or for 24 hours

for malathion, before

washing off

hands, change nappy, etc


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workers, close family contacts of an individual with hepatitis B, individuals

receiving blood transfusions

regularly, chronic kidney disease patients who may soon require renal

replacement therapy, prisoners,

chronic liver disease patients

-15% of adults fail to respond or respond poorly to 3 doses of the

vaccine. Risk factors include

age over 40 years, obesity, smoking, alcohol excess and immunosuppression

-HBs is only recommended for those at risk of occupational

exposure (i.e. Healthcare

workers) and patients with chronic kidney disease. In these patients anti-HBs

levels should be checked

1-4 months after primary immunisation

-HBs levels:

Anti-HBs level

(mIU/ml)

Response

> 100 Indicates adequate response, no further testing required. Should still

receive booster at 5 years

10 - 100 Suboptimal response - one additional vaccine dose should be given. If

immunocompetent no further testing is required

< 10 Non-responder. Test for current or past infection. Give further vaccine

course (i.e. 3 doses again) with testing following. If

still fails to respond then HBIG would be required for protection if exposed to

the virus


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Complications of hepatitis B infection

-10%)

Management of hepatitis B

-alpha used to be the only treatment available. It reduces

viral replication in up to

30% of chronic carriers. A better response is predicted by being female, < 50 years

old, low HBV DNA

levels, non-Asian, HIV negative, high degree of inflammation on liver biopsy

-effects of pegylated interferon it is now used less

commonly in clinical practice.

Oral antiviral medication is increasingly used with an aim to suppress viral

replication (not in dissimilar

way to treating HIV patients)

33.Co-existent infection with Chlamydia is extremely common in patients with

gonorrhoea.


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34.Lyme disease is associated with erythema chronicum migrans not erythema

marginatum

35.Which of the following anti-retroviral drugs is most characteristically

associated with nephrolithiasis?=Indinavir

36.Cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disorder causing increased viscosity

of secretions (e.g. lungs and

pancreas). It is due to a defect in the cystic fibrosis transmembrane conductance

regulator gene (CFTR), which

codes a cAMP-regulated chloride channel

In the UK 80% of CF cases are due to delta F508 on the long arm of chromosome

7. Cystic fibrosis affects 1 per

2500 births, and the carrier rate is c. 1 in 25

Organisms which may colonise CF patients

Burkholderia cepacia*


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*previously known as Pseudomonas cepacia

28.Lymphadenopathy

There are many causes of generalised lymphadenopathy

Infective

y infection

Neoplastic

Others


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lesser extent allopurinol, isoniazid

29.Cephalosporins are now the treatment of choice for

Gonorrhoea(ceftixime400mg or ceftrixone250mg).

30.Chickenpox exposure when pregnant - if not immune give VZIG

31.Cephalosporins, not just clindamycin, are strongly linked to Clostridium

difficile=pseudomembranous colitis

32.This is a difficult question as both co-amoxiclav and ciprofloxacin are known to

causeClostridium difficile. Studies

looking at the relative risk (RR) of developing Clostridium difficilefollowing

antibiotic therapy give the following

results (please see the link):


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Cefalexin is a first generation cephalosporin and less associated with Clostridium

difficilethan newer agents such

as ceftriaxone

33.Serological tests are the most appropriate first line investigation for

diagnosing Lyme disease. ELISA tests are

preferred to Western blots as they are more sensitive.

34.What is the mechanism of action of macrolides?=Inhibits protein synthesis

35.Antibiotics: mechanisms of action

The lists below summarise the site of action of the commonly used antibiotics

Inhibit cell wall formation

Inhibit protein synthesis

ycosides (cause misreading of mRNA)


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Inhibit DNA synthesis

Inhibit RNA synthesis

rifampicin

36.Tuberculin skin tests are an example of type IV (delayed) hypersensitivity

reactions. These are largely mediated

by interferon- secreted by T

h1 cells which in turn stimulates macrophage activity.

37.Mantoux test

purified protein derivative (PPD) injected intradermally

-3 days later

Diameter of


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induration

Positivity Interpretation

< 6mm Negative - no significant hypersensitivity to tuberculin

protein

Previously unvaccinated individuals may be given the BCG

6 - 15mm Positive - hypersensitive to tuberculin protein Should not be given

BCG. May be due to previous TB

infection or BCG

> 15mm Strongly positive - strongly hypersensitive to tuberculin

protein

Suggests tuberculosis infection.

38.Malaria: prophylaxis=page1800 in pass med read it

39.Differentiating between toxoplasmosis and lymphoma is an important aspect

of managing neurocomplications

relating to HIV. Given the more limited availablity of SPECT compared to CT

many patients are treated

empirically on the basis of scoring systems, for example there is a 90% likelihood

of toxoplasmosis if all of the

following criteria are met:


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ylaxis for toxoplasmosis

(. What is the most effective method to help differentiate between lymphoma

and

toxoplasmosis?in HIV =Thallium SPECT)

40.The low platelet count and raised transaminase level is typical of dengue fever

41.Osteomyelitis: MRI is the imaging modality of choice

42.amantadine-=Inhibits uncoating of virus in the cell


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43.Antibiotics: bactericidal vs. bacteriostatic

Bactericidal antibiotics

aminoglycosides

Bacteriostatic antibiotics

44.Post-exposure prophylaxis for HIV: oral antiretroviral therapy for 4 weeks

45.HIV: biliary and pancreatic disease


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The most common cause of biliary disease in patients with HIV is sclerosing

cholangitis due to infections such as

CMV, Cryptosporidium and Microsporidia

Pancreatitis in the context of HIV infection may be secondary to anti-retroviral

treatment (especially didanosine)

or by opportunistic infections e.g. CMV

46.Hepatitis B and pregnancy

Basics

babies born to mothers who are chronically infected with hepatitis B or to

mothers who've had acute

hepatitis B during pregnancy should receive a complete course of vaccination +

hepatitis B

immunoglobulin

Lamivudine) in the latter part of

pregnancy

transmission rates

a breastfeeding (in contrast to HIV)


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47.Genital wart treatment

-keratinised warts: topical podophyllum

48.Kaposi's sarcoma - caused by HHV-8 (human herpes virus 8)

49.Atypical lymphocytes - ?glandular fever=IMN

50.Pelvic inflammatory disease

Pelvic inflammatory disease (PID) is a term used to describe infection and

inflammation of the female pelvic

organs including the uterus, fallopian tubes, ovaries and the surrounding

peritoneum. It is usually the result of

ascending infection from the endocervix

Causative organisms

- the most common cause


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Features

deep dyspareunia

Investigation

Management

tential

complications of untreated PID,

consensus guidelines recommend having a low threshold for treatment

doxycycline + oral metronidazole

cases of PID intrauterine contraceptive

devices may be left in

Complications

- the risk may be as high as 10-20% after a single episode


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51.Leptospirosis - give penicillin or doxycycline

52.Rabies - following possible exposure give immunglobulin + vaccination

53.Splenectomy

Following a splenectomy patients are particularly at risk from pneumococcus,

Haemophilus, meningococcus and

Capnocytophaga canimorsus* infections

Vaccination

elective, should be done 2 weeks prior to operation

Antibiotic prophylaxis

prophylaxis should be

continued. It is generally accepted though that penicillin should be continued for

at least 2 years and at


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least until the patient is 16 years of age, although the majority of patients are

usually put on antibiotic

prophylaxis for life

*usually from dog bites

54.Cat scratch disease - caused by Bartonella henselae

55.Most common organism found in central line infections - Staphylococcus

epidermidis

56.Mumps meningitis is associated with a low CSF glucose

57.Man returns from trip abroad with maculopapular rash and flu-like illness -

think HIV seroconversion

58.Pyogenic liver abscess

Management


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penicillin allergic: ciprofloxacin + clindamycin

59.Septic arthritis: IV flucloxacillin

60.Septic arthritis

Overview

be

considered

Management

-positive cocci are indicated. The BNF

currently recommends

flucloxacillin or clindamycin if penicillin allergic

tic treatment is normally be given for several weeks (BNF states 6-12

weeks)

(look

in rhematology).


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61.Bacterial vaginosis: oral metronidazole

62.Genital warts - 90% are caused by HPV 6 & 11

63.Congenital toxoplasmosis

Thats all folks

Wait 4 on exam notes

Yours/faisal gamal hemeda

Thank you !!


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