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Flashcards in Infectious Disease 2 Deck (138):
1

What is the most common causative organism of malaria? What are the other 3? New one?

Plasmodium falciparum most common
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi is the new one

2

Typical incubation period of falciparum malaria? What about vivax/ovale?

1-2 weeks
Up to a month for falciparum, 6 months for vivax/ovale

3

Which two organisms might be implicated in a malaria 'relapse' ages after initial presentation?

Vivax and ovale

4

Malaria parasite associated with long incubation period and nephrotic syndrome?

Plasmodium malariae

5

When are the carriers of malaria parasites most active?

Dusk-dawn

6

Typical fever pattern for falciparum malaria?

Quotidian - daily
Can be irregular, tertian (every 3rd day) or subtertian (36 hour cycles)

7

Common symptoms of malaria?

Fever - swinging, recurrent
Chills and rigors
Cough
Headache
Nausea, vomiting, diarrhoea
Myalgia

8

Signs of malaria?

Hepatosplenomgealy
Jaundice
Abdominal tenderness

9

What sorts of things indicate severe malaria infection?

Respiratory distress
Reducing consciousness, fits
Bleeding or shock
Renal failure, nephrotic syndrome

10

Major differentials for fever in returning traveller?

Malaria
Dengue
Typhoid
Viral hepatitis

11

Diagnostic investigations for malaria?

Blood films - thick (presence) and thin (type)
Dipstick tests
Nucleic acid based testing

12

ABCD of malaria prophylaxis?

Awareness of risk - destination, travel advice, high risk categories
Bite avoidance - mosquito nets, keeping inside/covered dusk-dawn
Chemoprophylaxis - chloroquine, mefloquine, malarone, doxycycline
Diagnosis - and prompt treatment

13

What Chemoprophylaxis is used for low-risk malaria areas? Common side effects?

Chloroquine
GI upset

14

What chemoprophylaxis is used for high risk malaria areas e.g. Subsaharan Africa? Side effects?

Mefloquine
Psychosis, convulsions, coma

15

What should be suspected in a systemically unwell woman with no obvious source of infection but offensive vaginal discharge?

?retained tampon - staphylococcal toxic shock syndrome

16

How is typhoid spread?

Fecal-oral incl food (shellfish), water

17

RFs for typhoid fever?

Foreign travel to risk areas - Asia, Africa, S America
H2RBs, PPIs, antacids, GI pathology
Recent Abx
Immunosuppression, extremes of age
Haemaglobinopathies (SCD)

18

How long is the incubation period for typhoid?

Similar to malaria - 1-3 weeks, nearly always within 1 month

19

Over how long does untreated typhoid manifest?

4 weeks, where 3 is the worst and 4 is start of recovery

20

Classical key Sx of typhoid?

Gradually worsening persistent fever, evening exacerbation
Malaise, headaches
Epistaxis
GI - abdo pain (RIF), distension, hepatosplenomegaly
Rash (rose spots on abdomen, chest)

21

Investigations for typhoid?

Blood cultures, marrow cultures
Serology for H and O antigens (Widals test)

22

Is there a vaccine for typhoid?

Yes

23

What is the spectrum of illness with Dengue fever?

Dengue fever -> dengue haemorrhagic fever -> dengue shock syndrome

24

Virus and vector for dengue fever?

Flavivirus spread by Aedes mosquito

25

Incubation period of dengue?

2-7 days, typically around 3

26

Key Sx of dengue?

Abrupt onset high fever
Myalgias (breakbone)
Frontal/orbital headache
Generalised macular rash
GI upset
Haemolytic tendencies incl epistaxis

27

Features of dengue haemorrhagic fever?

Mucosal bleeding
Capillary permeability abnormalities - low protein, oedema, pleural effusions etc.
Hepatosplenomegaly

28

Diagnosis of dengue? What else should be done?

Serum IgM, IgG
Serum PCR
Should also do malaria films

29

Organism and spread of Lyme disease?

Deer tick bites spreading borrelia burgdorferi

30

Early symptoms of Lyme disease?

Erythema migrans - target lesion >5cm occurring at site of tick attachment, usually within 1m of bite
Plus or minus non-specific illness

31

Symptoms of disseminated Lyme disease?

Flu like illness
Facial nerve palsies, meningoencephalitis
Myocarditis
Lymphocytomas on earlobe/nipples (blue-red swellings)

32

Late manifestations of Lyme disease?

Arthralgias - typically recurrent, of large joints like knee
Acrodermatitis chronica atrophicans (blue red discolouration of extensor surfaces) alongside swelling and peripheral neuropathies
Neuro stuff

33

4 differentials for erythema migrans?

Bug bite reaction
Hives/urticaria
Ringworm
Cellulitis

34

Pathophysiology of infective endocarditis?

Background of Nonbacterial thrombotic endocarditis (platelet-fibrin vegetation) which gets infected

35

RFs for IE?

IVDU
Replacement heart valves, catheters, prostheses, haemodialysis
Structural heart abnormalities e.g. VSD, PDA
Recent dental work
Pre-existing valvular disease e.g. Hx of rheumatic fever
Autoimmune background
Hx of IE

36

Why do bacterial vegetations not get destroyed in IE/ why is there no substantial neutrophilia?

Valves are poorly vascularised - only platelets do first line attacking
Microemboli trigger RES (humoral arm) in spleen so AgAb complexes start getting formed, causing Sx

37

3 most common pathogens behind IE?

Strep viridans (a haemolytic)
Staph aureus
Coagulase negative staph

38

What pathogen is most implicated in IVDU or healthcare associated IE?(acute presentation)

Staph aureus

39

What bacteria is most implicated in native valve endocarditis/late prosthetic endocarditis? (Subacute)

Strep viridans (a haemolytic)

40

What bacteria have the biggest role in new prosthetic valve endocarditis?

Coagulase negative staph

41

Rarer bacterial causes of IE?

Enterococci and gram negatives
Pseudomonas
Fungi

42

Symptoms of acute/fulminant IE?

Fever, rigors
Acute heart failure
Arrhythmias
Septic shock

43

Common Sx of subacute IE?

Fever, night sweats (PUO)
Weight loss
TATT
Arthralgias

44

What does spiking PUO and conduction abnormalities with a heart murmur suggest?

Aortic root abscess secondary to IE

45

4 areas of signs of IE?

Systemic
Embolic
Cardiac
Immune vasculitis

46

Systemic signs of IE?

Petechial haemorrhages in conjunctiva, palate, buccal
Roth spots
Oslers nodes, janeway lesions
Clubbing
Splinter haemorrhages

47

Cardiac signs of IE?

New or changing murmur
Conduction abnormalities
Heart failure

48

Embolic signs of IE?

Stroke, PE, peripheral infarcts, MI, DVT etc.

49

Immune vasculitis consequences of IE?

Immune complex nephritis -> haematuria, microalbuminuria
Splenomegaly
Petechial rash
Arthralgias

50

What does neutrophilia in the context of IE suggest?

Abscess formation

51

What is diagnostic of IE?

At least 3 sets of blood cultures, taken during temp spikes

52

Imaging for IE?

Echo - Transoesophageal if poss

53

What are the general principles behind IE treatment?

High dose, long term (4-6 week) Abx treatment based on culture sensitivities particularly if subacute
Combo synergistic therapy
E.g. Vanc and gent (covers S aureus) or Amox and gent for viridans

54

When might surgical involvement be required for IE?

Abscess formation
If in prosthetic valves (biofilm covered)
Large or persistent vegetations

55

SIGHT management of suspected C Diff?

Suspected case of infectious diarrhoea, Abx history, no better cause
Isolate and investigate
Gloves and aprons (PPE)
Hand washing with soap and water
Test stools

56

What is C Diff?

Gram negative bacillus in many people which typically only causes trouble when normal gut flora wiped out e.g. By Abx treatment.
Can cause a pseudomembranous colitis (acute, exudative) via toxins A and B

57

How is c diff transmitted and how does it remain in the environment?

Transmitted fecal-orally, can form spores in the environment and stay there for ages

58

Drugs associated with c diff? (1 non-Abx)

PPIs
Clindamycin
Macrolides
Vancomycin
B lactams
Cephalosporins

59

Generally what sorts of antibiotics are associated with c diff infection?

IV, broad spectrum Abx

60

Symptoms of c diff colitis?

Diarrhoea starting 5-10 days after commencing Abx (varying severity)
Fever, rigors, malaise
Colicky abdo pain

61

Outline testing process for c diff?

Do stool testing - Glutamate dehydrogenase (GDH) positive = presence of C diff but not necessarily infection, toxins A/B positive = causing infection

62

What should you do if a patient is positive for GDH but negative for toxins and still has diarrhoea?

Isolate anyway and retest for c diff

63

2 patients, 1 with C diff 1 with MRSA. Which do you isolate first and why?

C diff, because it can form environmental spores which can be really hard to get rid of

64

Besides SIGHT, management of c diff?

Stop offending Abx, consider changing to vanc or metronidazole
Conservative - fluids etc.

65

Major complications of C diff infection?

Recurrence
Fulminant colitis, toxic megacolon, peroration
Splenic abscess
Dehydration, shock, AKI etc.

66

Common Sx of HA-MRSA?

Can appear as boil/pustule, abscess particularly around wound sites
Fever, rigors, generally unwell

67

Potential Sx of CA-MRSA infection?

Can cause severe cellulitis

68

What type of bacteria is mycobacterium tuberculosis?

Acid fast bacillus

69

What is the primary TB infection?

Spread by droplets, M TB gets engulfed in the lungs by macrophages and transported to hilar LNs -> granulomas around the body

70

What may happen at the point of a primary TB infection?

May become symptomatic initially -> overt/active TB, miliary
May eliminate all the bacteria
May lay dormant in granulomas -> secondary infection of LTBI

71

RFs for TB?

Being born in endemic area, big cities etc.
Social deprivation factors - homeless, alcohol, IVDU
HIV and other Immunocompromise
Elderly and children

72

Constitutional and pulmonary symptoms of reactivated LTBI?

Fever, weight loss, night sweats TATT, anaemia
Cough, productive +/- bloodstained
Lobar collapse, bronchiectasis, pleural effusion etc.

73

Second most common TB presentation (extra-pulmonary)?

Sterile pyuria - kidney lesions, abscesses, salpingitis, infertility, epididymitis

74

MSK presentations of TB?

Potts vertebrae (collapse)
Arthritides
Osteomyelitis

75

CNS presentations of TB?

Meningitis
Tuberculomas

76

What CXR picture does primary TB infection give?

Central apical portion, left lower lobe infiltrate
+/- pleural effusion

77

What CXR picture does reactivated TB show?

Apical lesions (granulomas) - cavitating lesions
No pleural effusions

78

What CXR does miliary TB show?

All over the shop (millet seed)

79

How is TB investigated microbiologically?

Early morning sputum samples - bronchoscopy, lavage and gastric washing if necessary
Cultures take 4-8 weeks for confirmation and a further 3-4 for sensitivities (apart from Rifampicin)

80

What histological investigation should be done for extra-pulmonary TB?

Biopsy of LNs and CXR

81

Screening tests for TB?

Tuberculin: Heaf test, Mantoux test (may be positive if had BCG)
IgG testing (IGRA)

82

Basic management of TB infection?

Inform CDC
6 month 4 drug regime, dependant on sensitivities but generally Rifampicin isoniazid ethambutol pyrazinamide for 2m then Rifampicin and isoniazid for another 4

83

Alternatives to first line TB drugs?

Streptomycin
Other macrolides, quinolones

84

What must be monitored during TB drug therapy?

LFTs as most can derange, renal impairment
Visual impairment (ethambutol)
Peripheral neuropathy (isoniazid)
Arthralgias (pyrazinamide)

85

In whom is disseminated MAC disease most common?

HIV with low cd4 count - AIDS

86

What does MAC infection cause in kids?

Cervical lymphadenitis - blue-purple discharging LN

87

What is lady Windermere syndrome?

Pneumonitis in elderly women traditionally who have suppressed their cough reflex, caused by MAC infection

88

What is hot tub lung?

MAC infection causing granulomatous pneumonitis related to inhaling aerosolised MAC in water, e.g. Poorly maintained hot tubs

89

What is an important factor, but not pre-requisite in MAC infection?

Immunocompromise e.g. HIV, elderly, CF

90

What is a Ghon complex?

Initial granuloma + infected lymph node in TB - may be on skin, in lungs

91

What is leprosy/hansens disease?

Infection with mycobacterium leprae causing nothing initially, then years later skin lesions (discolouration) alongside neuropathy, eye changes and respiratory Sx

92

Transmission of leprosy?

Droplet, normally close contact with infected
Animal (armadillo)

93

What is impetigo?

Honeycomb golden crusting due to epidermal infection often caused by s aureus

94

What is a furuncle?

Infection of whole hair follicle down to root causing micronecrosis
Caused by s aureus

95

What is folliculitis?

Pustule formation around hair follicle caused by s aureus

96

What is a carbuncle?

Infection of multiple hair follicles causing draining abscess formation

97

What is flucloxacillin effective against?

S pyogenes
S pneunoniae
MSSA

98

What is ludwigs angina?

Nec fasc of submandibular space

99

What is Fournier's gangrene?

Nec fasc of scrotum/vulva

100

Signs indicative of nec fasc rather than cellulitis?

Pain disproportionate to visible signs and systemic illness
Bullae or ecchymosis
Tender beyond poorly demarcated borders

101

What is osteomyelitis?

Infection of the bone marrow, which can spread to cortex and periosteum
Typically caused by s aureus incl MRSA

102

What is a sequestrum?

Area of dead bone detached from healthy bone seen in osteomyelitis, acting as focus for chronic infection

103

What is an involcrum?

Periosteum separated from underlying bone in osteomyelitis, acting as source for new bone growth

104

What is the likely origin of osteomyelitis in kids or those with in dwelling catheters?

Haematogenous spread

105

Rx for osteomyelitis?

Flucloxacillin and Rifampicin for 4-6 weeks
But wait for culture results!

106

Gold standard diagnosis for osteomyelitis?

Bone cultures

107

What enzyme distinguishes s aureus from other staph species?

Coagulate

108

What is STSS?

Streptococcal toxic shock syndrome - shock caused by s pyogenes toxin exotoxin release

109

What is TSS?

Toxic shock syndrome typically caused by staph aureus

110

What differentiates STSS from TSS?

TSS often arise as shock with fever in otherwise healthy individual, has characteristic sunburn rash which causes desquamation in couple of weeks
STSS however comes from site of pre-existing skin infection, looks a bit like nec fasc but doesn't include the sunburn rash

111

What is SSSS?

Staphylococcal Scalded Skin Syndrome; widespread fluid filled blisters, possibly widespread desquamation
Ritter's Disease of the newborn

112

3 structural pathogenicity factors of s aureus?

Protein A
Peptidoglycan
Clumping factor

113

What exotoxin in s aureus (MRSA) is associated with high virulence, necrotising pneumonia and potentially neutropenia?

Panton-Valentine Leukocidin

114

What criteria is used to define haemolytic streptococci?

Lancefield criteria

115

What is GAS?

B haemolytic streptococci - strep pyogenes

116

What do B haemolytic streptococci do to blood?

Completely haemolyse it

117

What is acute rheumatic fever?

A complication of GAS infection; autoimmune attack on endocardium/synovial tissue (migrating polyarthropathy)

118

What disease does GAS in new mothers?

Puerperal sepsis

119

What causes puerperal fever?

GAS

120

What are 2 examples of alpha haemolytic streptococci? What do they do to blood?

Strep pneumoniae and strep viridans
Weakly oxidising so turn it green

121

What is the classic GBS?

Strep agalactiae

122

Important disease caused by GBS?

Neonatal meningitis and pneumonia, also elderly meningitis

123

What can GBS bacteruria cause in a pregnant woman?

Stillbirth, prematurity, miscarriage

124

Are enterococci gram positive or negative? 2 most common species?

Positive
Enterococcus faecalis and faecium

125

Alternative name for enterococci?

Lactobacilli

126

Are enterococci aerobic or anaerobic?

Facultative anaerobes

127

What do enterococci intrinsically resist?

Cephalosporins

128

3 examples of coliform bacteria?

Enterobacter
Klebsiella
Faecal coliforms e.g. E. coli

129

3 examples of aminoglycosides?

Gentamicin
Streptomycin
Rifampicin

130

3 examples of macrolides?

Clarithromycin
Erythromycin
Azithromycin

131

How do macrolides work?

Protein synthesis inhibitors

132

What type of bacteria are macrolides effective against?

Gram negatives e.g. Gonorrhoea

133

What are the general side effects of aminoglycosides?

Ototoxicity
Nephrotoxicity

134

How do vancomycin and teicoplanin work?

Inhibit cell wall synthesis via peptidoglycan formation

135

General trend working through the generations of cephalosporins?

Better action vs gram negatives

136

What are tetracyclines commonly used for?

Second line vs pneumonia (if penicillin allergy)

137

What is metronidazole effective against?

Gram negatives, fungi and protozoa

138

What is ciprofloxacin? Special relevance?

Fluoroquinolone
Good vs pseudomonas and used prophylactically vs bacterial meningitis