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MD2 ID > Intro to ID > Flashcards

Intro to ID Flashcards

1
Q

What is the leading cause of death and morbidity worldwide?

A

Infectious disease (15 million deaths annually)

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2
Q

What % of presentations does infectious disease make up, in GP and ED respectively?

A

> 70% in GP

~20% in ED

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3
Q

What is the #2 most prescribed agent in Aus?

A

Antimicrobials (15-20% of all prescriptions)

About 20% of public hospital in-patients receive Abx

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4
Q

What is the major cause of inappropriate antibiotic use?

A

Poor clinical judgment about the presence of a bacterial infection where there is none

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5
Q

What % of antibiotic use is empirical?

A

~80%

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6
Q

What is the 3-tier approach to ID?

A

Tier 1: problem-solving of clinical syndromes, taking into account symptoms (e.g. fever, cough, diarrhoea, rash, sore throat, etc) and pt groups (e.g. overseas-born, returned traveller, immunosuppressed, post-op, etc)
Tier 2: management of infections of various organ systems (e.g. meningitis, endocarditis, pneumonia, osteomyelitis, gastroenteritis, UTIs)
Tier 3: specific infections and pathogens (e.g. S. aureus, N. meningitidis, Salmonella, Campylobacter, HIV/AIDS, influenza, hepatitis A/B/C, STIs, malaria, TB, etc)

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7
Q

Give 6 examples of immunological defects which may impact susceptibility to infection

A 
Post-chemotherapy neutropenia
Lymphocyte dysfunction (e.g. HIV)
Immunoglobulin deficit (e.g. myeloma)
Splenectomy
Pregnancy
Malnutrition (similar effect to HIV)
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8
Q

What kind of infections does post-chemotherapy neutropenia predispose to?

A

Bacterial sepsis

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9
Q

What kind of infections does lymphocyte dysfunction predispose to?

A

Intracellular or slow-growing pathogens

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10
Q

What kind of infections does immunoglobulin deficit predispose to?

A

Encapsulated bacteria

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11
Q

What kind of infections does splenectomy predispose to?

A

Pneumococcal infection

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12
Q

Describe the diurnal pattern of body temperature

A

Highest in the evening, lowest in the morning

Therefore fever in the morning is ALWAYS significant!

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13
Q

Give 2 examples of conditions notorious for falsely “masking” signs of infection severity

A

Diabetes

Corticosteroids

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14
Q

What temperature range suggests bacterial sepsis?

A

> 38.4C

<36C

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15
Q

What HR is suggestive of bacterial sepsis?

A

> 90/min, but beware of relative bradycardia in certain situations (for each 0.5-0.6C increase in temperature, HR should increase by ~10/min)
BEWARE B-BLOCKERS AND PATIENTS WITH HEART BLOCK

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16
Q

What RR is suggestive of bacterial sepsis?

A

> 20/min

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17
Q

List 4 more signs of bacterial sepsis

A

Altered mental state

Hypoxaemia (PaO2 20mmHg

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18
Q

What are 2 important factors to remember when considering BP in a pt with suspected bacterial sepsis?

A

Hypotension is often a late sign

A “normal” BP can be low if the pt is ordinarily hypertensive

19
Q

What is the usual timeline for MCS testing?

A

24-48h to growth
24hr to identification
24-48hr to Abx susceptibilities
Usually 3-5 days

20
Q

What do rigors indicate?

A

Serious illness until proven otherwise (admit!)

21
Q

How can signs vary according to the pt’s age?

A

Infants - prominent
Adolescents - confusing
Adults - affected by comorbidities
Elderly - blunted

22
Q

When should you take blood cultures?

A

If serious infection is suspected

23
Q

What is the common infectious disease presentation in general practice?

A

Respiratory tract infections

24
Q

45 year old male presents with 3/7 fever, sweats, cough, SOB and 2kg LOW
Previously well
CXR shows right upper lobe consolidation
Likely Dx? Likely pathogen?

A

Acute CAP, like S. pneumoniae

25
Q

45 year old male presents with fever, sweats, cough, SOB and 2kg LOW
Ex-smoker with insulin-dependent DM
2/12 Hx increasing blood-stained, purulent sputum after 1/12 trip to India
DDx?

A

TB

Lung Ca with secondary infection

26
Q

45 year old male presents with fever, sweats, non-productive cough, 1/7 rapidly increasing SOB and 2kg LOW
PHx: Hodgkin’s lymphoma (just completed 3rd cycle of “CHOP” chemotherapy 2/52 earlier), severely neutropenic
O/E: BP 75/50
DDx? Likely pathogen?

A

Febrile neutropenia with acute Gram-negative or staphylococcal pneumonia (likely to require early ICU admission)
Acute aspiration pneumonia following chemo-related vomiting

27
Q

What is the emphasis on when managing infections of various organ systems? (I.e. tier 2 of the 3-tier approach to ID)

A

Clinical Dx
Lab Ix
Choice of Rx
Monitoring Rx

28
Q

What factors are important to ascertain on Hx in a patient with suspected infection?

A

The illness: onset and duration (“when were you last well”), the order, severity and progression of various symptoms, response to therapy received during illness
The setting: previous state of health (co-morbidities), ?immunosuppression (e.g. pregnancy, malnutrition), predisposing events, epidemiology, contact with similar illness or known infectious disease, vaccination Hx

29
Q

What might the nature of onset of the illness tell you about possible underlying causes?

A

Bacterial sepsis usually abrupt onset

Viral infections often (but not always) evolve more gradually

30
Q

What are the 2 types of symptoms to be considered in an infectious disease Hx? Give examples of each

A

Systemic (e.g. fever, chills, sweats, myalgia, LOW, lethargy, fatigue; prominence reflects severity)
Localising (e.g. cough diarrhoea, pain; these can be misleading)

31
Q

Give examples of contexts in which an apparent “localising” symptom may be misleading

A

Diarrhoea can be a symptom of bacteraemic illness and not a GI infection
Dry cough can be associated with typhoid

32
Q

List 3 settings which may predispose to illness

A

Recent operations
Accidents/injuries
New medications (e.g. adverse events, Abx may affect bug’s resistance pattern)

33
Q

What aspects of epidemiology are important to ascertain in an infectious disease Hx?

A

Country of birth
Sexual Hx
Occupation/exposure to animals and other vectors (e.g. mosquitos, ticks, fleas)
Food Hx (e.g. unpasteurized milk products, uncooked meat, fast-food)
Travel Hx (where, how long, urban vs rural, pre-travel vaccination, anti-malarial prophylaxis)
Travel to rural areas (zoonotic contact)

34
Q

List specific signs to look for on physical examination in the infectious disease patient

A

Eyes: conjunctival haemorrhages (e.g. staph endocarditis), scleral jaundice
Skin: rashes (esp petechial), cellulitis (esp on legs), evidence of IVDU
Muscles: marked tenderness (sepsis)
LNs: esp posterior cervical nodes, tenderness of jugulo-digastric nodes (early bacterial tonsilitis), axillary and inguinal nodes (CMV, HIV)
Throat: signs may precede symptoms in streptococcal tonsilitis, oedema of the uvula (useful sign of bacterial infection)
Neck: neck stiffness (meningitis)
Heart: murmurs (endocarditis), pericardial rub
Lungs: subtle crackles (pneumonia), pleural rub
Abdomen: tenderness, enlargement without pain
NB don’t forget about covered areas!

35
Q

7 signs of bacterial sepsis

A 
Fever
Tachycardia
Tachypnoea
Altered mental state
Hypoxaemia
Oliguria
Hypotension (late sign)
36
Q

8 key Abx??

A

??

37
Q

What public health issues are important to consider in the assessment of the infectious diseases patient?

A

Importance of incubation times and periods of infectivity/transmissibility
Notifiable diseases
Outbreak management
Contact tracing

38
Q

55 year old female presents with 4/52 of fever, sweats and LOW
PHx: RHD with “leaky valve”
2/52 before illness onset she had a tooth abscess drained by dentist
O/E: temp 38.2C, AR murmur, red “peticheal” rash on fingertips and under toenails, no retinal haemorrhages
Likely Dx? Likely pathogen?
Mx?

A

Dx: RHD with subsequent aortic valve endocarditis
Pathogen: Likely viridans streptococci
Mx: depends on pathogen and degree of valve damage, options include prolonged IV Abx (2-4/52) and surgical valve resection with prosthetic valve replacement

39
Q

20 year old female medical student, previously well, attended Aus Day BBQ and consumed “undercooked egg rolls”, hamburgers and potato salad, as well as 5 beers
Next day developed severe watery diarrhoea, low grade fevers, severe lethargy and lost 4kg over 24hrs (moderate dehydration)
DDx and likely source of pathogen?
Mx?

A

DDx: salmonella (from eggs), campylobacter (from ground beef in hamburgers)
Mx: fluid replacement/resusc, generally self-limiting, no Abx needed (unless at)

40
Q

35 year old diabetic male with painless, purulent foot ulcer
3/52 of increasingly unstable diabetic control
Occasional low-grade fevers
Offensive odour from ulcer
O/E: grossly deformed foot, marked sensory neuropathy, ulcer that probes to bone
Dx?
Mx?

A

Dx: diabetic foot ulcer with underlying ostemyelitis
Mx: surgical debridement +/- long-term Abx

41
Q

Does the absence of fever rule out infection?

A

NO

42
Q

What does staph aureus bacteraemia indicate?

A

Endocarditis or osteomyelitis until proven otherwise (staph aureus bacteraemia is always significant!)

43
Q

What are some possible reasons a patient may not improve on Abx, other than failure of the Abx?

A

Too short a period to observe an improvement
Undrained focus of infection
Infection is not bacterial
I.e. a second course of Abx is rarely needed!

MD2 ID (8 decks)

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