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Clinical Years / Progress Test > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

how many sets of blood cultures should be taken in suspected bacteraemia

A

standard is to take 3 sets/6 bottles (separate times or separate sites)

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2
Q

how is antibiotic susceptibility classified

A

susceptible/intermediate/resistance based on minimum inhibitory concentration

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3
Q

what is B-D glucan

A

a fungal cell wall component which is released into the blood during invasive fungal infection
very sensitive but not specific

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4
Q

NAAT testing

A

nucleic acid amplification testing

used especially for respiratory viruses e.g. flu
very quick and highly specific

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5
Q

what are the serological things measured for hepatitis B

A

HBsAg

anti-HBs

anti-HBc

IgM-anti-HBc

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6
Q

which HBV marker shows active infection

A

HBsAg

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7
Q

what serology shows natural immunity to HBV

A

anti-HBs positive
anti-HBc positive

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8
Q

what serology shows artificial immunity (vaccination) to HBV

A

anti-HBs psoitive
rest negative

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9
Q

possible serology explanations if only anti-HBc positive

A
  1. resolved infection (most common)
  2. false positive test
  3. low level chronic infection
  4. resolving acute infection
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10
Q

acute vs chronic HBV infection serology results

A

both:
- HBsAg +ve
- anti-HBc +ve
- anti-HBs -ve

acute has IgM antiHBc whereas chronic doesn’t

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11
Q

steps of diagnosing infection

A
  1. could this be infection?
  2. what organ system?
  3. what type of microorganism could it be in this patient?
  4. what specimens need collecting?
  5. what tests do you want to request?
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12
Q

how is infection diagnosed?

A

detailed history including travel history, sexual history and occupation history

examination and observations

lab tests; micro, haem, biochemistry

radiology

histopathology

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13
Q

considerations for selecting an antibiotic

A
  • which are effective against the probable pathogen(s)
  • which reach the infected site?
  • any allergies?
  • any pt problems with excretion or metabolism?
  • pregnancy?
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14
Q

tetracyclines specific side effect

A

teeth discolouration especially in children - avoid in under 12s

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15
Q

aminoglycosides specific side effect

A

ototoxicity and nephrotoxicity

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16
Q

when is therapeutic drug monitoring required

A

antimicrobials with variable absorption and/or metabolism and/or excretion
e.g.
gentamicin
teicoplanin, vancomycin
‘azole’ antifungals eg. itraconazole

more may need TDM in a critically unwell patient

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17
Q

why is TDM needed

A

prevent toxicity and ensure therapeutic doses are given

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18
Q

examples of organisms commonly associated with hospital acquired infections

A

Norovirus
MRSA
Clostridium Difficile
Carbapenem resistant E Coli

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19
Q

how may bacteria be classified

A

gram staining
morphology; rods, cocci etc
growth requirements; an/aerobic

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20
Q

gram staining

A

gram negative bacteria stain pink/red

gram positive bacteria stay purple with iodine - thick peptidoglycan wall

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21
Q

what are obligate aerobes and obligate anaerobes

A

obligate aerobes are bacteria that can only grow in the presence of oxygen

obligate anaerobes can only grow in the absence

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22
Q

what are facultative aerobes/facultative anaerobes

A

grow well in the presence and absence of oxygen
most human pathogens fall into this criteria

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23
Q

what is Ziehl-Neelson staining

A

different type of staining used for mycobacterium
bacteria which hold the stain are called acid-fast bacilli

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24
Q

what is done when bacteria are difficult to stain

A

some bacteria that live inside human cells such as chlamydia and mycoplasma are better identified using PCR or antibodies against them

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25
Q

morphology of bacteria

A

how they appear under the microscope
cocci- spherical in chains, clusters or pairs
rods- elongated
coccobacilli - in between cocci and rods
spiral - e.g. treponema pallidium/syphilis and Borrelia burgdorferi/lyme disease

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26
Q

how do staphylococci appear compared to streptococci

A

staph more in clusters

strep in chains

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27
Q

gram negative rods

A

Escherichia coli, Klebsiella pneumoniae or Proteus mirabilis

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28
Q

what is usually the first choice Abx for anaerobic infections

A

metronidazole

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29
Q

diarrhoea organisms

A

salmonella spp.
shigella spp.
yersinia spp.
E coli
campylobacter spp.

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30
Q

samples in a pt with diarrhoea

A

stool culture/ova/parasites

blood culture, urine culture, HIV, FBC, CRP, U+E, LFT

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31
Q

shigella infection management

A

common cause of travellers diarrhoea

if stable can be managed at home with hydration - usually resolves after 5-7 days

Antibiotics would only be indicated if there was evidence of Shigella bacteraemia with positive blood cultures

needs follow up - post-infection arthritis can occur

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32
Q

post infectious complications travellers diarrhoea

A

reactive arthritis
uveitis
urethritis
IBS

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33
Q

what does Candida albicans in a sputum sample represent

A

colonisation of the respiratory tract or contamination from oral candida
does not cause pneumonia

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34
Q

candida in a blood culture

A

significant - a medical emergency
high mortality

needs IV antifungals for 2 weeks from when blood cultures start to be negative

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35
Q

most common source of candidaemia

A

gut flora - can get into blood stream if epithelium becomes damaged for example in sepsis

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36
Q

how can fungal infections be classified

A

superficial, subcutaneous or deep mycoses

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37
Q

superficial fungal infections
who gets them
examples

A

common, can happen in anyone but more at risk/severe in immunocompromised e.g. HIV or diabetes

examples
- oral and vaginal thrush
- tinea (ring worm)
- fungal nail infection
- pityriasis versicolour

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38
Q

subcutaneous fungal infections

A

not common in UK - more in tropical countries
affect the dermis, subcutaneous tissue and adjacent bones and there is often some degree of immunocompromise

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39
Q

deep fungal infections
who gets them
examples

A

occur in immunocompromised; e.g. from chemotherapy or advanced HIV

invasive candida
invasive aspergillus
PCP
Cryptococcal meningitis

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40
Q

how does candida appear on blood culture

A

appear as gram positive cocci but much larger

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41
Q

how is candidaemia treated

A

micafungin

if central line associated remove the line

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42
Q

what infection is chickenpox

important complication requiring admission

A

primary varicella zoster infection

can cause pneumonitis

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43
Q

risk factors for severe presentation of chicken pox

A

immuncompromise - diabetes, HIV, medications
systemic inflammatory conditions
smoking, pregnancy and chronic lung disease are also risk factors

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44
Q

chicken pox vaccine

A

live vaccine so cannot be used in those severely immunocompromised or pregnant women

vaccine is for non-immune healthcare workers and non-immune close contacts of immunocompromised patients

vaccine can be used at prevention and treatment

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45
Q

what is the treatment of varicella zoster in an immunocompromised pt

A

aciclovir

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46
Q

presentation of chicken pox

A

usually mild in children

prodrome of fever and lethargy followed by an itchy vesicular rash

spreads from face and trunk to limbs

47
Q

complications of chicken pox if presentation more severe

A

pneumonitis
bacterial infection of lesions
encephalitis
keratitis
hepatitis
myocarditis

48
Q

what type of virus are EBV, cytomegalovirus, karposis sarcoma and HSV1&2

A

herpes viruses

49
Q

who does CMV cause disease in

A

immunocompromised
e.g. can cause retinitis in HIV patients and transplant rejection

50
Q

how does shingles occur

A

VZV lies dormant in single nerves or dorsal root ganglion and on reactivation causes symptoms in a dermatome
pain usually precedes the rash

can transmit chicken pox from shingles to non-immune people

51
Q

action in pregnancy if no recorded hx of chicken pox

A

test for VZV IgG; if positive no action needed
if negative consider for post exposure prophylaxis with antivirals

52
Q

risk to mother and foetus of VZV infection

A

The risk of severe disease in the mother is highest during the second or early third trimester, when she is relatively immunocompromised and more likely to develop pneumonitis

The risk to the foetus is greatest in the first 20 weeks. VZV is one of the “TORCH” infections and can lead to foetal varicella syndrome.

53
Q

what are the common characteristics of herpes viruses

A

have a latent period where they reside in neurons; reactivation can be triggered by stress, menstruation, fever, sunlight, cell-mediated immune dysfunction, and HIV
migrate to skin/nerve endings and cause symptoms

opposed by cell mediated immune response

54
Q

what does
HSV1 cause
HSV2 cause

A

HSV1 oral ulcers

HSV2 genital ulcers

but both viruses can cause disease in either part of the body

lie dormant in nerves then reactivates in relapses

55
Q

HSV in pregnancy

A

Neonatal herpes is very rare but can have high morbidity and mortality - highest risk with maternal genital HSV in third trimester

genital herpes in pregnancy is treated with single dose aciclovir unless in third trimester in which case give acicolvir until delivery and plan caesarean

56
Q

measles presentation

A

prodrome of fever, malaise, conjunctivitis and cough. Blue-grey spots called Koplik spots appear inside the buccal mucosa but disappear early on

rash appears as a maculopapular rash that starts on the face and spreads down the body

57
Q

measles complications

A

include bacterial pneumonia, otitis media, and acute encephalitis

58
Q

primary HIV infection

A

also called seroconversion

flu like illness but can be entirely asymptomatic

when antibodies appear in the serum the pt is said to be seroconverted

59
Q

glandular fever

A

Glandular fever is a syndrome of fever, sore throat and lymphadenopathy. Most cases are caused by Epstein-Barr virus with a minority being caused by cytomegalovirus. Most people acquire these infections in infancy but there is a second peak in the teenage years

60
Q

monkey pox

A

transmission via contact with animal, human, or materials contaminated with the virus which enters through broken skin, resp tract or mucous membranes

The infection is usually self-limiting with fever, malaise, lymphadenopathy, and headache. The incubation period is usually 5-21 days. Treatment is mainly supportive

61
Q

how are viruses classified

A

as DNA or RNA viruses
and further on single or double strand

62
Q

tests to diagnose viral infection

A

PCR
antigen testing
antibody testing
histology - via end organ damage
viral culture (not routine)

63
Q

respiratory viruses

A

adenovirus

respiratory syncytial virus

influenza viruses

coronaviruses

rhinovirus

parainfluenza virus (viral croup)

human metapneumovirus

64
Q

causes of viral gastroenteritis

A

norovirus
rotavirus

65
Q

treatment of viral gastroenteritis

A

mainstay is hydration - oral rehydration solutions

in severe cases may need IV rehydration

66
Q

concerns of cellulitis in hands

A

nerve and blood vessel damage due to swelling and compression in small spaces

67
Q

first line antibiotic uncomplicated cellulitis

A

flucloxacillin - staph aureus most common organism

clarithromycin/clinda if allergic

68
Q

first line antibiotic mammal bites

A

co amoxiclav

69
Q

what antibiotics are effective against MRSA

A

vancomycin and doxycycline
teicoplanin and linezolid

70
Q

sign of deep soft tissue infection

A

pain in excess of erythema

71
Q

investigating tissue infection

A

FBC
blood cultures
ABG
CK

imaging; xray, USS

screen for blood borne viruses

72
Q

management necrositing fascitis

A

surgical debridement

+ ABx and fluids, and analgesia supportive

73
Q

what micro-organisms can cause skin and soft tissue infections commonly

A

staph aureus
group A strep (pyogenes)
pseudomonas aeriginosa

74
Q

what is gas gangrene

A

rapidly progressive and life-threatening.

Wounds become contaminated with Clostridium spores
Management is similar to necrotising fasciitis with surgical debridement and antibiotics to cover the most likely bacteria.

75
Q

management of severe septic diarrhoea presentation

A

IV fluids

oral rehydration salts

IV hydrocortisone to prevent addisonian crisis

intravenous piperacillin / tazobactam with metronidazole to cover for translocation of gut pathogens

76
Q

tests in severe diarrhoea presentation

A

FBC, U+E, LFT, CRP, lactate

Blood culture - if septic

Urine culture and analysis

Stool culture and microscopy

ABG if septic

HIV test, CMV if immunocompromised and refer to gastro

77
Q

what is dysentery

A

bloody diarrhoea

78
Q

CMV colitis

A

caused by reactivation and proliferation of cytomegalovirus

in an immunocompetent host infection does not cause significant clinical signs

Acute symptomatic infection or reactivation of a latent infection can occur in patients who are immunosuppressed, causing a variety of symptoms including pyrexia, dehydration, vomiting and bloody diarrhea

treatment is Ganciclovir

79
Q

CMV presentations

A

depend on site of infection

spread by infected secretions
- CMV mononucleosis
- CMV colitis

80
Q

when should malaria be considered

A

anyone with a fever/Hx of one returned from an endemic area within the last year

81
Q

hep C transmission

A

blood borne virus
IVDU are highest risk

there is no vaccine

82
Q

hep C natural course

A

incubation period 2 weeks - 6 months

2/3 asymptomatic in acute phase. if symptomatic usually mild right upper abdominal pain, fever, lethargy, jaundice, joint pain and confusion
ALT can be 10-20x upper limit

chronic infection is common

liver cirrhosis and hepatocellualr carcinoma high risk

83
Q

hep C diagnosis

A

anti-HCV antibody is the best initial test, followed by HCV RNA detection in the blood by PCR tests to identify chronic active infection

84
Q

hep C treatment

A

interferon and ribavirin have been mainstay

direct antivirals coming in

85
Q

amoebic liver abscess cause

A

caused by a parasite transmitted by the faecal oral route
incubation period can vary weeks up to years

86
Q

amoebic liver abscess diagnosis and treatment

A

Ultrasound of the liver will usually reveal a single, round hypoechoic lesion
raised ALP and WCC

treatment is metronidazole 7-10 days

87
Q

Pneumocystis Jirovecii Pneumonia

A

yeast like fungal pathogen that can cause a pneumonia in those who are immunocompromised

one of the most common opportunistic infection

presents with exertion dyspnoea, dry cough, and malaise
can be first presentation of HIV

test bloods, HIV test, Beta-d glucan, CXR

88
Q

PJP prophylaxis

A

can’t prevent exposure

Patients infected with HIV who have a CD4 count <200 cells/mm3 are advised to take PCP prophylaxis. The first line medication is low dose co-trimoxazole 960mg OD

89
Q

breastfeeding HIV +ve

vaginal birth?

A

advised against even if undetectable viral load - possible risk of transmission

vaginal birth is fine if viral load undetectable

90
Q

how many HIV drugs are typically given

A

3 different drugs in combination

typically two nucleoside reverse transcriptase inhibitors (NRTI) and either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI)

91
Q

PPIs and Rilpivirine

A

PPIs must never be used with this HIV drug as they reduce concentration so make it ineffective

many ARVs can react with other medications and also recreational drugs - always check

92
Q

Post-Exposure Prophylaxis (PEP)

A

when an individual has had a exposure at high risk of HIV e.g. sexual behaviour of high risk or a needle stick injury

must be started within 72 hours

93
Q

Pre Exposure Prophylaxis (PrEP)

A

can be taken regularly by individuals at high risk of HIV

94
Q

travel history important questions

A
  1. countries visited or transited through
  2. dates of travel and illness onset
  3. pre-travel vaccines/malaria proph
  4. type of travel
  5. activities whilst abroad
  6. Viral Haemorrhagic Fever risk assessment
  7. immune status
95
Q

hep B transmission and course

A

blood borne, sex, vertical, close household contact

acute viral hepatitis
can progress to chronic

complications HCC and cirrhosis

vaccine available

96
Q

hep D

A

sub viral particle
requires HBV co-infection

HBV vaccine is protective

97
Q

hep E

A

faecal oral route

usually mild but can be severe especially risk in pregnant women

chronic infection only in immunocompromised

98
Q

hep A

A

faecal oral, blood, sex

acute viral hepatitis with fever, jaundice and hepatomegaly

vaccine available

99
Q

dengue fever

A

viral infection transmitted by a mosquito that can progress to viral haemorrhagic fever (severe dengue) where disseminated intravascular coagulation is seen

treatment is entirely symptomatic

100
Q

typhoid/paratyphoid

A

caused by salmonella viruses transmitted by faecal oral route

101
Q

what diseases can E.Coli cause

A

diarrhoeal illnesses
UTIs
neonatal meningitis

102
Q

syphilis cause and treatment

A

syphilis, caused by Treponema pallidum

IM benzathine benzylpenicillin given as a single dose

can cause a Jarisch-Herxheimer reaction within 24 hrs of starting treatment - give antipyretics

103
Q

gonorrhoea treatment

A

IM ceftriaxone

104
Q

Disseminated gonococcal infection

A

triad = tenosynovitis, migratory polyarthritis, dermatitis

105
Q

what is malaria

symptoms of malaria

A

protazoan parasitic infection transmitted by mosquitos

symptoms are of general malaise (fever, headache, N&V, muscle pain) + splenomegaly

106
Q

Lyme disease
- causative organism
- features of disease

A

tick-born spirochaetial infection caused by Borrelia burgdorferi

stage 1 - early disease with non-specific systemic symptoms such as fever, arthralgia and malaise, often associated with the typical rash.

stage 2- occurs several weeks later, with possible aseptic meningitis, facial palsy, arthritis and a carditis.

stage 3 - may occur months to years later, with neuropsychiatric manifestations and chronic fatigue (this is rare in children).

The rash is pathognomic of Lyme Disease, and treatment can be given without serological confirmation

107
Q

treatment Lyme disease

A

Cefuroxime and amoxicillin

Blood tests are indicated if symptoms persist and there is uncertainty about the diagnosis.

108
Q

infections to consider with an animal bite

A

tetanus - make sure vaccinations are up to date

rabies if abroad

109
Q

gas gangrene

A

some soft tissue infections can lead to gas gangrene as bacteria produce gas - this is an emergency; surgical debridement and Abx

110
Q

The commonest two bacteria implicated in skin and soft tissue infections

A

staph aureus and strep pyogenes(group A strep)

111
Q

how to determine if a hepatitis C infection is active

A

HCV antibody just confirms previous exposure to HCV

to work out if active need to send blood for Hepatitis C RNA PCR
any detectable level indicates active infection

112
Q

what defines a late HIV diagnosis

A

defined as a CD4 count <350 cells/mm3 within 3 months of diagnosis; likely to have had it for >3 years and high risk of transmission

113
Q

HIV test counselling

A

need to explain whether screen due to the patient living in a high prevalence area but without any particular suspicion of HIV or if HIV is suspected due to an indicator disease or high-risk life style

Lengthy pre-test HIV counselling is not a requirement in either case, unless a patient requests or needs this. The essential elements that the pre-test discussion should cover are:
- The benefits of testing to the individual
- Details of how the result will be given

another way in areas on high prevalence is information about routine HIV testing at the department is provided using posters and leaflets and this is emphasised by stating the same verbally
Notional consent is used in opt-out HIV testing in which tests are routinely offered to all patients, with the offer to decline

Clinical Years / Progress Test (24 decks)

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