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Year 3 > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

Diarrhoea

Gastro-enteritis

Dysentery

A

Subjective - Fluidity and frequency

Objective - >= 3 loose stools/day + features

Obvious - Large bowel inflammation, bloody stools

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2
Q

Bristol Stool Chart Types

A

1) Separate hard lumps (nuts) - Hard to pass
2) Sausage-shaped but lumpy
3) Sausage but cracks on the surface
4) Sausage/Snake - Smooth and Soft
5) Soft blobs with clear-cut edges
6) Fluffy pieces with ragged edges, mushy stool
7) Watery, no solid pieces

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3
Q

Epidemiology of gastro-enteritis

A

Contamination of food e.g. chicken + campylobacter (commonest bacterial + foodborne pathogen but viruses are the commonest cause - norovirus)
Isolated cases rather than outbreaks (C. jejuni/ C. coli)

Poor storage of produce
E.g. Bacterial proliferation at room temperature

Travel-related infections e.g. Salmonella (most hospital admissions)

Person-to-person spread e.g. Norovirus

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4
Q

Defences against enteric infections

A

Hygiene

Stomach acidity - antacids and infection

normal Gut Flora - Cl. difficile diarrhoea

Immunity - HIV - Salmonella

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5
Q

Diarrhoeal illness

Non-inflammatory / Secretory

A

e.g. Cholera - Secretory toxin-mediated - Vibrio.cholerae
Enterotoxigenic E. coli (travellers’ diarrhoea)

Increases cAMP levels and Cl secretion

Frequent watery stools with LITTLE Abdominal Pain

  • Fluid and electrolyte losses
    Hyponatraemia due to Na+ loss with fluid replacement by hypotonic solutions
    Hypokalaemia due to K loss in stool

Rehydration mainstay of therapy

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6
Q

Inflammatory

Mixed picture

A

e.g. Shigella (Bacterial) / Amoebic dysentery

Inflammatory toxin damage and mucosal destruction Pain and Fever

Rehydration + Antimicrobials may be appropriate

e.g. C. difficile

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7
Q

Assessing Diarrhoeal illness

A

Symptoms and their duration
>2/52 unlikely to be infective gastro-enteritis

Risk of food poisoning - Dietary, Contact, Travel history

Assess hydration - Postural BP, skin Turgor, Pulse

Features of inflammation (SIRS) - Fever, raised WCC

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8
Q

Assessing Diarrhoeal illness in Children

A

Sunken Eyes, No tears
Sunken Fontanelle
Sunken Abdomen

Skin Turgor decreased
Dry Mouth / Tongue

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9
Q

Diarrhoeal illness Investigations

A

Stool culture
Blood culture
Bacterial culture (selective and enrichment methods)

polymerase chain reaction (PCR)
antigen-detecting enzyme immunoassays (EIAs) immunofluorescence assays (IFAs)
microscopy, serology, and viral culture

Renal function
Blood count - Neutrophilia, Haemolysis

Abdominal X-Ray if abdomen distended, tender

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10
Q

Diarrhoeal illness

*Differential diagnosis

A

IBD, Carcinoma
Spurious diarrhoea - Secondary to constipation
SEPSIS outside gut - Diarrhoea + Fever
- Lack of Abdo pain/tenderness; against gastroenteritis
- No blood/mucus in stools

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11
Q

Gastroenteritis Treatment

A

Oral rehydration with salt (Na)/sugar (glucose) solution

IV saline

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12
Q

Campylobacter gastroenteritis

A

Up to *7 days incubation so dietary history unreliable
Stools negative within 6 weeks

Abdominal pain can be severe
<1% invasive

Post-infection sequelae - Guillain-Barre syndrome, Reactive arthritis

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13
Q

Salmonella gastroenteritis

Salmonella enterica

A

Symptom onset usually <48 hrs after exposure
Diarrhoea usually lasts <10 days
<5% positive blood cultures

20% patients still have positive stools at 20/52

Prolonged carriage may be associated with gallstones
Post-infectious irritable bowel is common

Screened out as lactose non-fermenters
Then antigen and biochemical tests

Salmonella enteritidis and Salmonella typhimurium
> 50% of these were imported from abroad in 2010

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14
Q

S. typhi and S. paratyphi

A

Cause enteric fever (typhoid and paratyphoid)

and NOT gastro-enteritis

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15
Q

E.Coli 0157

A

From contaminated meat or person-to-person spread

Frequent bloody stools
Produces (verocyto-)toxin

E. coli O157 stays in the gut but the toxin gets into the blood - can cause HUS

Treatment supportive – antibiotics NOT indicated

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16
Q

Hemolytic-uraemic syndrome (HUS)

A

Toxin binds to globotriaosylceramide
Platelet activation stimulated
Micro-angiopathy results
Attach to endothelial, glomerular, tubule, mesangial cells

Characterised by renal failure, haemolytic anaemia and thrombocytopenia.

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17
Q

Abx Treatment Indicated in gastroenteritis for?

A 
Immunocompromised
Severe sepsis or invasive infection
Valvular heart disease
Chronic illness
Diabetes
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18
Q

Clostridium difficile diarrhoea

A

Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics”

Severity ranges from mild diarrhoea to severe colitis

C. Diff produces enterotoxin (A) and
cytotoxin (B) (inflammatory)

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19
Q

Clostridium difficile Treatment

A

Metronidazole
oral Vancomycin
Fidaxomicin (new and expensive)

Stool transplants
Surgery may be required

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20
Q

Clostridium difficile prevention

A

Reduction in broad spectrum antibiotic prescribing
Avoid 4 Cs – Cephalosporins, Co-amoxiclav, Clindamycin, Clarithromycin

Antimicrobial Management Team (AMT) and local antibiotic policy

Isolate symptomatic patients
Wash hands between patients

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21
Q

Parasitology

A

Protozoa and helminths
Diagnosis generally by microscopy
Send stool with request “parasites, cysts and ova please” or P, C and O

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22
Q

Sepsis

Acute change in total SOFA score >2 which reflects an overall mortality risk of approximately 10% in hospital

Sequential (Sepsis-Related) Organ Failure Assessment Score

A

Systemic illness caused by microbial invasion of normally sterile parts of the body

Life-threatening organ dysfunction caused by dysregulated host response to infection

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23
Q

SIRS

Sepsis

Severe Sepsis

Septic Shock

A

> =2 of fever >38.0°C or hypothermia <36.0°C,
tachycardia >90 beats/minute,
tachypnoea >20 breaths/minute,
leucocytosis >12109/l or leucopoenia <4109/l

SIRS + Infection

Sepsis + End Organ Damage

+ Hypotension

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24
Q

qSOFA

A

Promptly identifies patients with suspected infection who are likely to have a prolonged ICU stay / die in hospital

Hypotension (Systolic BP<100mmHg)
Altered Mental Status
Tachypnoea RR >20/min

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25
Q

SEPSIS 6

A

The Sepsis Six is the name given to a bundle of medical therapies designed to reduce mortality in patients with sepsis.

High Flow Oxygen
Blood Cultures
IV Abx
Fluid challenge (rapid correction of hypovolaemia state)
Lactate Measurement 
Urine Output measurement
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26
Q

Phases in the pathogenesis of sepsis

A

Release of bacterial toxins
Release of mediators
Effects of specific excessive mediators

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27
Q

Commonly released toxins:
Gram negative

Gram positive

Superantigens

A

Lipopolysaccharide (LPS)

Microbial-associated molecular pattern (MAMP)

  • Lipoteichoic acid
  • Muramyl dipeptides

Staphylococcal toxic shock syndrome toxin (TSST)
Streptococcal exotoxins

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28
Q

Transmission rootes and bacteria

A

Direct contact
e.g. Staphylococcus aureus, coliforms

Respiratory/Droplet
e.g. Neisseria meningitidis, Mycobacteria tuberculosis

Faecal-Oral
e.g. Clostridium difficile, Salmonella sp.

Penetrating Injury
e.g. Group A streptococcus, Bloodborne viruses

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29
Q

ANTIVIRAL THERAPY

Use ASAP and within 48hours of symptom onset

A

Neuraminidase Inhibitors:

ZANAMIVIR (RELENZA) - Inhaled
Adverse Effects: Rare – occasional bronchospasm

OSELTAMIVIR (TAMIFLU) - Oral
Adverse Effects: Renal dosing needed
Common – Nausea, vomiting, Abd pain, diarrhoea
Less Common – Headache, hallucinations, insomnia

PERAMIVIR (Alpivab®)
Intravenous infusion, for uncomplicated influenza

Favipiravir (Avigan®)
Viral RNA polymerase inhibitor

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30
Q

Beta-d-glucan

A

Tool to diagnose *invasive fungal infections
eg. *Candidiasis

High NPV (negative predictive value) mean patient almost certaintlhy doesnt have disease

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31
Q

Aspergillus Causes and Pathophysiology

A

Aspergilloma

  • Fungal mass in lung
  • Bronchiectasis/ Sarcoidosis

Allergic (Asthma, CF), COPD

Airborne conidia - Inhaled
Neutropenia - low level of neutrophils eg. leukaemia
Hyphal growth and dissemination
Angio-Invasive, Thrombosis, Haemorrhage

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32
Q

Aspergillus Ix if Neutropenic patient

A

CT Chest in high resolution shows
‘‘halo sign + air crescent sign’’

Blood Molecular Markers, PCR
Galactomannon (component of the cell wall of Aspergillus and is released during growth), NPVHigh?

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33
Q

Aspergillus Ix if non-Neutropenic patient

A

Sputum Culture
Bronchoalveolar lavage +/- biopsy

Aspergillus Specific IgE and IgG if chronic/allergic

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34
Q

Cryptococcus + Cryptococcosis Symptoms

Meningitis - HIV associated

A 
Headache
Confusion
Increased ICP - coma
Altered Behaviour
Visual Disturbance
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35
Q

Cryptococcus Investigations

A

CSF -Indian ink preparation

*CSF Culture - High Protein, Low Glucose

Cryptococcus Ag

36
Q

Antifungals

A

Amphotericin B - Ergosterol Lysis

Azoles - Inhibit Ergosterol synthesis

Echinocandins - Inhibit Glucan Synthesis

Flucytosine - Inhibit Fungal DNA Synthesis

37
Q

Candidiasis - Thrush

RF

A

Mucocutaneous:
Moist Areas
Inhaled Steroids
Neonates < 3 months

Invasive: 40% MORTALITY
Premature Neonates 
Gut Commensal 
Abd Surgery, TPN
Intravascular cathetirisation
38
Q

ZOONOSES

A

Infections that can pass between living animals and humans - The source of the disease is from the animal

Malaria, Schistosomiasis - Are not zoonoses since they
depend on the human host for part of their life-cycle

Bacteria - Salmonella
Virus - Rabies
Parasites - Toxoplasmosis
Fungi - Dermatophytoses
Prions - CJDv
39
Q

Anthroponosis

A

Humans are infecting animals

eg. Influenza, Leishmaniasis

40
Q

Rash

A

Typhoid,
Typhus
Dengue

41
Q

Lymph Nodes

A

leishmania,

Trypanosomiasis

42
Q

Liver

A

Malaria,
Typhoid,
Amoebic abscess

43
Q

Spleen

A

Visceral Leishmaniasis

Typhoid, Malaria

44
Q

Jaundice

A

Hepatitis,
Malaria,
Yellow fever

45
Q

Infectious Diseases Investigations

A 
FBC
Malaria films
Liver function tests
Stool microscopy &amp; culture
Urine analysis &amp; culture
Blood culture(s)
CXR

+ *Specific Tests

46
Q

Water-related infections

A

Schistosomiasis

Leptospirosis

47
Q

Arthropod-borne infections

A 
Malaria (mosquitos)
Dengue fever (mosquitos)
Rickettsial infections (ticks: typhus)
Leishmaniasis (sand flies: Kala-azar)
Trypanosomiasis (tsetse fly: sleeping sickness)
48
Q

Emerging Infectious Diseases

A

Zika: Latin America, Caribbean

Ebola virus disease: West Africa

MERS-CoV: Middle East
- Middle East respiratory syndrome (MERS); camel flu, is viral infection caused by the MERS-coronavirus

Avian ‘flu (H5N1 and H7N9): China

Swine ‘flu (H1N1): worldwide

49
Q

Malaria - Clinical features

A 
SYMPTOMS
fever, rigors, headache
*aching bones
abdo pain
*dysuria, frequency
*sore throat, cough
SIGNS
none
splenomegaly
hepatomegaly
mild jaundice
50
Q

Complications of Malaria

A 
Cerebral malaria (encephalopathy)
- hypoglycaemia, convulsions, hypoxia

Blackwater fever
- severe intravascular haemolysis, high parasitaemia, profound anaemia, haemoglobinuria, acute renal failure

Pulmonary oedema
Jaundice
Severe anaemia

Algid malaria - Gram-negative septicaemia

51
Q

Malaria - Investigation Dx

A

Thick & thin blood films
- Giemsa, Field’s stain

Quantitative buffy coat (QBC)
- Centrifugation, UV microscopy

Rapid antigen tests
- OptiMal, ParaSight-F

52
Q

Complicated malaria = one or more of

A 
Impaired consciousness or seizures 
Hypoglycaemia
Parasite count >2%
Haemoglobin <= 8mg/dL
Spontaneous bleeding
Haemoglobinuria 
Renal impairment or pH <7.3
Pulmonary oedema or ARDS
53
Q

Treatment of Malaria

A

Quinine, Artemisinins

Uncomplicated P. falciparum
Riamet / Eurartesim / Malarone for 3days

Uncomplicated + Complicated P. falciparum
- Quinine 7 days + oral doxycycline
Quinine S/E nausea, tinnitus, deafness, rash, hypoglycaemia

54
Q

Treatment of P. vivax, P. ovale, P. malariae, P. knowlesi Malaria Species

A

Riamet / Chloroquine for 3 days

add Primaquine* (14 days) in vivax and ovale, to eradicate liver hypnozoites

55
Q

Malaria Control Programmes

A

Mosquito breeding sites - Drainage of standing water
Larvacides - Biological
Mosquito killing sprays - DDT
Human behaviour - Bed nets, Mesh windows

56
Q

Typhoid Fever: Clinical features

A

Incubation period: 7 days - 4 week

1st week: fever, headache, abdo. discomfort, constipation, dry cough, *relative bradycardia, neutrophilia, *confusion

2nd week: fever peaks at 7-10 days,
*Rose spots,
*diarrhoea begins,
tachycardia, *neutropenia

3rd week (Complications): *intestinal bleeding, perforation, peritonism, metastatic infections

week 4 (Recovery): 10 - 15% relapse

57
Q

Typhoid Fever: Treatment

A

Oral Azithromycin (for Asian-acquired / uncomplicated)

IV Ceftriaxone (3rd gener. cephalosporin)
(if complicated - week 3,
or concerned regarding absorption)

58
Q

Classical Dengue Fever Presentation

A

Sudden fever
Severe headache, *Retro-orbital pain

Severe myalgia and arthralgia

Macular/ maculopapular rash

Haemorrhagic signs: 3Ps
Petechiae, Purpura,
Positive tourniquet test

59
Q

Dengue Ix

A

Thrombocytopenia – low platelet count
Leucopenia – low leukocyte
Elevated transaminases
Positive tourniquet test

Laboratory: PCR, serology

60
Q

Dengue Complications and Treatment

A

Dengue haemorrhagic fever (DHF)
Dengue shock syndrome (DSS)

Rx: IV fluids, fresh frozen plasma, platelets

61
Q

Schistosomiasis - Clinical features

A

Swimmers Itch (1st few hrs) clears

Invasive stage (after 24hrs)
cough, abdo discomfort, splenomegaly, eosinophilia
Katayama Fever (after 15-20 days)
prostrate, fever, urticaria, lymphadenopathy, splenomegaly, diarrhoea, eosinophilia

Acute disease (6-8 weeks)
- eggs deposited in bowel (dysentery) or
bladder (haematuria)

Chronic disease

62
Q

Schistosomiasis - Diagnosis + Treatment

A

Clinical diagnosis
Antibody tests
Ova in stools and urine
Rectal snip

PRAZIQUANTEL 20mg/kg, two doses 6hrs apart
Prednisolone if severe

63
Q

Tick typhus - Rickettsiosis Signs, Clinical features

Management, Diagnosis

A

Tick-bite eschar
rash (macular, petechial) eg. Maculopapular rash

*abrupt onset swinging fever, headache, confusion, *endovasculitis, bleeding

Serology

Tetracycline

64
Q

Viral Haemorrhagic Fevers

A

Ebola
Congo-Crimea haemorrhagic fever

Maximum incubation period 3 weeks

Isolation: High Security Infection Unit

65
Q

Zika

Aedes Mosquitos, Flavivirus, Sex, Blood

A

Clinical: no or mild symptoms
- headache, rash, fever, malaise, conjunctivitis,
joint pains (like dengue)

In pregnancy, can cause microcephaly and other neurological problems

Can cause Guillain-Barre syndrome

66
Q

Live attenuated vaccines

A 
Measles, mumps, rubella (MMR)
Varicella-zoster virus
Yellow fever
Smallpox
Typhoid (oral)
Polio (oral)
Rotavirus (oral)
67
Q

Inactivated (killed) vaccines

require Doses

A 
Polio 
Hepatitis A
Cholera (oral)
Rabies
Tick-borne encephalitis
Influenza
68
Q

Detoxified exotoxin vaccines

A

Diphtheria,
Tetanus

TOXIN - treat with formalin - TOXOID

69
Q

Subunit vaccines

A 
Pertussis (acellular)
Haemophilus influenzae type b
Meningococcus (group C) 
Pneumococcus 
Typhoid 
Hepatitis B
70
Q

Recombinant vaccines e.g. Hepatitis B

A

DNA segment coding for HBsAg

removed, purified, mixed with plasmids
inserted into yeasts, fermented

HBsAg produced

71
Q

Secondary response

Immunological Memory

A

Higher Total Antibodies

Higher IgG (same IgM)

72
Q

“6 in 1” vaccine: Infanrix hexa

A 
D	=	purified diphtheria toxoid
T	=	purified tetanus toxoid
aP	=	purified Bordetella pertussis 
IPV  =	inactivated polio virus
Hib  = purified component of Haemophilus Influenzae b
HBV=	hepatitis B rDNA
73
Q

UK Childhood Immunisation Schedule below 1Year Old

A

2 months: 6-in-1 vaccine + pneumococcal conjugate
+ rotavirus + Men B

3 months: 6-in-1 vaccine + rotavirus

4 months: 6-in-1 vaccine + pneumococcal conjugate
+ Men B

74
Q

UK Childhood Immunisation Schedule > 1 Year Old

A

1 year: Hib/Men C+ MMR + pneumococcal conjugate + men B

2 -8 years: influenza nasal

3 - 5 years: 4-in-1 booster (DTaP/IPV) + MMR

Girls, 12-13 yrs: Human papilloma virus

14 years: 3-in-1 booster (dT/IPV) + Men ACWY

75
Q

Herd Immunity

A

Resistance to the spread of a contagious disease within a population

that results if a sufficiently high proportion of individuals are immune to the disease,

especially through vaccination.

76
Q

Bacille Calmette-Guerin (BCG) vaccine

A

TB Associated

77
Q

herpes-zoster (shingles) vaccine

A

All elderly patients (70-80 years)

Zostavax
Live attenuated virus

78
Q

Common Immunisations for Travelers

Special Circumstances

A 
Tetanus
Polio
Typhoid 
Hepatitis A
Yellow fever
Cholera
Meningococcus 
Rabies
Diphtheria
Japanese B encephalitis 
Tick borne encephalitis
79
Q

Antimicrobial Prophylaxis

A

Chemoprophylaxis against Malaria

Post-exposure prophylaxis
e.g. ciprofloxacin for meningococcal disease

HIV post-exposure prophylaxis
“needle stick” (PEP), sexual intercourse (PEPSI)

Surgical antibiotic prophylaxis - perioperative

80
Q

Chemoprophylaxis against Malaria

A

Malarone ® (proquanil & atovaquone) daily
Doxycycline daily
Mefloquine weekly
Avoid if history of psychosis, epilepsy

81
Q

Reasons to prescribe Abx

A

Therapy
empiric - without microbiology results
directed - based on microbiology results

Prophylaxis
- Primary - pre-operative surgical
anti-malarial; immunosupressed patients
post-exposure e.g. HIV, meningitis
- Secondary - To prevent a second episode e.g. PJP
82
Q

Bactericidal vs. Bacteriostatic

A

Cidal e.g. beta-lactams
act on cell wall
kill organisms
indications: neutropenia, meningitis and endocarditis

Static e.g. macrolides 
inhibit protein synthesis
prevent colony growth
require host immune system to “mop up” infection
useful in toxin-mediated illness
83
Q

Oral route:

IV route:

A

If not vomiting, normal GI function,
no shock, no organ dysfunction

For severe or deep-seated infection, and
when oral route is not reliable

84
Q

Principles of Prescribing

A
  1. Indications for antimicrobials (Therapy/prophylaxis)
  2. Making a clinical diagnosis
  3. Patient characteristics
    - age, renal, liver function
    - immunocompromised, pregnancy, known allergies
  4. Antimicrobial selection
    - Guideline or “individualised” therapy
    - empirical therapy or result-based therapy
    - bactericidal vs. bacteriostatic drug
    - single agent or combination
    - potential adverse effects
  5. Regimen selection
    - Route of administration
    - Dose, Duration
    - Adverse effects (side effects/toxicity)
    - Intravenous to oral
  6. Liaison with laboratory
  7. Antimicrobial Stewardship
85
Q

Penicillin and Cephalosporins common to cause adverse effects such as…

A

Immediate hypersensitivity
- anaphylactic shock

Delayed hypersensitivity
- rash, drug fever, serum sickness, erythema nodosum, Stevens-Johnson syndrome

Year 3 (7 decks)

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