Infectious diseases Flashcards

1
Q

What is the difference between gram positive and gram negative bacteria?

A

Gram-positive bacteria have a thick peptidoglycan cell wall that stains with crystal violet stain.
Gram-negative bacteria do not have a thick peptidoglycan cell wall or stain with crystal violet stain but will stain with other stains

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2
Q

What is the mechanism of Metronidazole

A

Inhibits nucleic acid synthesis

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3
Q

What types of antibiotic target the ribosomes?

A

macrolides (e.g. clarithromycin)
tetracyclines (e.g. doxycycline) , gentamicin

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4
Q

What is the mechanism of action of trimethoprim?

A

inhibits folic acid synthesis

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5
Q

State 3 types of gram-positive cocci

A

Staphylococcus
Streptococcus
Enterococcus

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6
Q

What antibiotics can be used to treat MRSA?

A

Doxycycline
Clindamycin
Vancomycin
Teicoplanin
Linezolid

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7
Q

What are the antibiotics of choice for Extended-spectrum beta-lactamase (ESBL) bacteria?

A

Nitrofurantoin
Fosfomycin
Carbapenems (e.g., meropenem or imipenem)

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8
Q

What types of antibiotics inhibit cell wall synthesis?

A

Antibiotics with a beta-lactam ring:

Penicillin
Carbapenems such as meropenem
Cephalosporins

Antibiotics without a beta-lactam ring:

Vancomycin
Teicoplanin

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9
Q

Describe the pathophysiology of sepsis

A

pathogen triggers release of cytokines, interleukins and tumour necrosis factor leading to systemic inflammation and release of Nitrous oxide (vasodilation). Endothelial lining more permeable -> oedema -> reduced tissue perfusion
Activation of coagulation system -> fibrin deposition -> thrombi -> thrombocytopenia (DIC)
Anaerobic respiration -> lactate rises -> metabolic acidosis

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10
Q

What is septic shock?

A

when the arterial blood pressure drops despite adequate fluid resuscitation, resulting in organ hypoperfusion. Anaerobic respiration begins, and the serum lactate level rises

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11
Q

How is septic shock diagnosed?

A

Low mean arterial pressure (below 65 mmHg) despite fluid resuscitation (requiring vasopressors)
Raised serum lactate (above 2 mmol/L)

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12
Q

What is the sepsis-related organ failure assessment?

A

(SOFA) criteria can be used to assess the severity of organ dysfunction. It takes into account signs of organ dysfunction:

Hypoxia
Increased oxygen requirements
Requiring mechanical ventilation
Low platelets (thrombocytopenia)
Reduce Glasgow Coma Scale (GCS)
Raised bilirubin
Reduce blood pressure
Raised creatinine

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13
Q

State 4 risk factors for sepsis

A

Very young or old patients (under 1 or over 75 years)
Chronic conditions, such as COPD and diabetes
Chemotherapy, immunosuppressants or steroids
Surgery, recent trauma or burns
Pregnancy and childbirth
Indwelling medical devices, such as catheters or central lines

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14
Q

Apart from the NEWS2 parameters what are some additional signs of sepsis?

A

Signs of potential sources, such as cellulitis, discharge from a wound, cough or dysuria
Reduced urine output
Mottled skin
Cyanosis
Arrhythmias, such as new-onset atrial fibrillation
A non-blanching rash can indicate meningococcal septicaemia

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15
Q

What blood tests should be done with suspected sepsis?

A

Full blood count for the white cell count and neutrophils
U&Es for kidney function and acute kidney injury
LFTs for liver function and as a possible source of infection
CRP to assess for inflammation
Blood glucose for hyperglycaemia and hypoglycaemia
Clotting to assess for disseminated intravascular coagulopathy (DIC)
Blood cultures to assess for bacteraemia
Blood gas for lactate, pH and glucose

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16
Q

What additional investigations can be done to help locate the source of infection in a septic patient?

A

Urine dipstick and urine culture
Chest x-ray
CT scan if an intra-abdominal infection or abscess is suspected
Lumbar puncture for meningitis or encephalitis

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17
Q

What is the sepsis six?

A

Three tests:
Serum lactate
Blood cultures
Urine output

Three treatments:
Oxygen to maintain oxygen saturation 94-98% (or 88-92% in COPD)
Empirical broad-spectrum antibiotics
IV fluids

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18
Q

What is neutropenic sepsis?

A

refers to sepsis in someone with a neutrophil count below 1 x 109/L. It is a life-threatening medical emergency.
Any temperature above 38ºC is treated as neutropenic sepsis until proven otherwise in patients at risk

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19
Q

What medications may cause neutropenia?

A

Chemotherapy
Clozapine
Hydroxychloroquine
Methotrexate
Sulfasalazine
Carbimazole
Quinine
Infliximab
Rituximab

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20
Q

How would a lower UTI present?

A

Dysuria (pain, stinging or burning when passing urine)
Suprapubic pain or discomfort
Frequency
Urgency
Incontinence
Haematuria
Cloudy or foul-smelling urine
Confusion is commonly the only symptom in older and frail patients

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21
Q

What is the triad of symptoms seen in pyelonephritis?

A

Fever
Loin or back pain (bilateral or unilateral)
Nausea or vomiting

Patients with pyelonephritis may also have:
Systemic illness
Loss of appetite
Haematuria
Renal angle tenderness on examination

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22
Q

What indicates a UTI on urine dipstick?

A

Nitrites (best)
Leukocytes
Blood

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23
Q

When is a MSU sent for microscopy and culture important in a UTI?

A

Pregnant patients
Patients with recurrent UTIs
Atypical symptoms
When symptoms do not improve with antibiotics

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24
Q

What type of bacteria is E.coli ?

A

gram-negative, anaerobic, rod-shaped bacteria

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25
Q

State 4 common bacterial causes of a UTI

A

E.coli
Klebsiella pneumoniae
Enterococcus
Pseudomonas aeruginosa
Staphylococcus saprophyticus

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26
Q

What are the 2 first line treatment options for a lower UTI?

A

Nitrofurantoin (avoided in patients with an eGFR <45)
Trimethoprim (often associated with high rates of bacterial resistance)

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27
Q

What is the typical duration of antibiotics in a lower UTI?

A

3 days of antibiotics for simple lower urinary tract infections in women
5-10 days of antibiotics for immunosuppressed women, abnormal anatomy or impaired kidney function
7 days of antibiotics for men, pregnant women or catheter-related UTIs

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28
Q

What are the treatment options for pyelonephritis and for how long?

A

7-10 days
Cefalexin
Co-amoxiclav (if culture results are available)
Trimethoprim (if culture results are available)
Ciprofloxacin (keep tendon damage and lower seizure threshold in mind)

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29
Q

What does UTI in pregnancy increase the risk of?

A

pyelonephritis, premature rupture of membranes and pre-term labour

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30
Q

How do you manage a UTI in pregnancy?

A

7 days
Nitrofurantoin (avoided in the third trimester)
Amoxicillin (only after sensitivities are known)
Cefalexin (the typical choice)

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31
Q

Why should Nitrofurantoin be avoided in the third trimester?

A

risk of neonatal haemolysis

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32
Q

What are the skin changes seen in cellulitis?

A

Erythema (red discolouration)
Warm or hot to touch
Tense
Thickened
Oedematous
Bullae (fluid-filled blisters)
A golden-yellow crust indicates a Staphylococcus aureus infection

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33
Q

What are the 3 most common causes of cellulitis?

A

Staphylococcus aureus
Group A streptococcus (mainly streptococcus pyogenes)
Group C streptococcus (mainly streptococcus dysgalactiae)

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34
Q

What is the Eron classification used for?

A

The Eron classification assesses the severity of cellulitis:

Class 1 – no systemic toxicity or comorbidity
Class 2 – systemic toxicity or comorbidity
Class 3 – significant systemic toxicity or significant comorbidity
Class 4 – sepsis or life-threatening infection

Class 3 and 4 cellulitis requires admission for intravenous antibiotics

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35
Q

what is the 1st line antibiotic for cellulitis?

A

Flucloxacillin

Alternatives:
Clarithromycin
Clindamycin
Co-amoxiclav (the usual first choice for cellulitis near the eyes or nose)

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36
Q

What is bacterial tonsillitis most commonly caused by?

A

group A streptococcus mainly streptococcus pyogenes

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37
Q

What is the Centor criteria?

A

Fever over 38ºC
Tonsillar exudates
Absence of cough
Tender anterior cervical lymph nodes (lymphadenopathy)

A score of 3 or more gives a 40 – 60 % probability of bacterial tonsillitis, and it is appropriate to offer antibiotics

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38
Q

What is the FeverPAIN score?

A

Fever during the previous 24 hours
P – Purulence (pus on tonsils)
A – Attended within 3 days of the onset of symptoms
I – Inflamed tonsils (severely inflamed)
N – No cough or coryza

A score of 2 – 3 gives a 34 – 40% probability, and 4 – 5 gives a 62 – 65% probability of bacterial tonsillitis

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39
Q

What is the first line antibiotic in bacterial tonsilitis?

A

Penicillin V (phenoxymethylpenicillin) for a 10-day course

Clarithromycin is the usual first-line choice in true penicillin allergy.

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40
Q

State 4 complications of tonsillitis

A

Peritonsillar abscess, also known as quinsy
Otitis media, if the infection spreads to the inner ear
Scarlet fever
Rheumatic fever
Post-streptococcal glomerulonephritis
Post-streptococcal reactive arthritis

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41
Q

What are the 1st and 2nd line antibiotics for otitis media?

A

Amoxicillin for 5-7 days first-line
Clarithromycin (if penicillin allergic)
Erythromycin (in pregnant women allergic to penicillin)

Co-amoxiclav is a second-line option if the infection is not responding to amoxicillin.

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42
Q

What is prescribed for patients with sinusitis who’s symptoms are not improving after 10 days?

A

High-dose steroid nasal spray for 14 days (e.g., mometasone 200 mcg twice daily)
A backup antibiotic prescription, used if worsening or not improving within 7 days (phenoxymethylpenicillin first-line)

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43
Q

What are some common bacterial causes of intra-abdominal infections?

A

Anaerobes (e.g., Bacteroides and Clostridium)
E. coli (gram-negative)
Klebsiella (gram-negative)
Enterococcus (gram-positive)
Streptococcus (gram-positive)

44
Q

What is the mortality rate in septic arthritis?

A

10%

45
Q

What are the presenting symptoms of septic arthritis?

A

A hot, red, swollen and painful joint
Stiffness and reduced range of motion
Systemic symptoms, such as fever, lethargy and sepsis

46
Q

What is the most common causative organism in septic arthritis?

A

Staphylococcus aureus

47
Q

State 4 differentials of septic arthritis

A

Gout
Pseudogout
Reactive arthritis
Haemarthrosis (bleeding into the joint, usually after trauma)

48
Q

What is the management of septic arthritis?

A

Joint aspiration ( sent for gram staining, crystal microscopy, culture and antibiotic sensitivities)
Empirical IV antibiotics (4-6w) often flucloxacillin

49
Q

What type of virus is influenza?

A

RNA virus

50
Q

Who is offered the flu vaccine?

A

Aged 65 and over
Young children
Pregnant women
Chronic health conditions, such as asthma, COPD, heart failure and diabetes
Healthcare workers and carers

51
Q

What are the two options for treatment in someone at risk of complications of influenza?

A

Oral oseltamivir (twice daily for 5 days)
Inhaled zanamivir (twice daily for 5 days)

Treatment needs to be started within 48 hours of the onset of symptoms to be effective.

52
Q

state 4 complications of influenza

A

Otitis media, sinusitis and bronchitis
Viral pneumonia
Secondary bacteria pneumonia
Worsening chronic health conditions, such as COPD and heart failure
Febrile convulsions (young children)
Encephalitis

53
Q

state 3 viruses that can cause gastroenteritis

A

Rotavirus
Norovirus
Adenovirus

54
Q

What are the symptoms of travellers’ diarrhoea caused by Campylobacter Jejuni

A

Incubation is usually 2 to 5 days. Symptoms resolve after 3 to 6 days. Symptoms are:

Abdominal cramps
Diarrhoea often with blood
Vomiting
Fever

55
Q

How is Campylobacter Jejuni spread?

A

Raw or improperly cooked poultry
Untreated water
Unpasteurised milk

56
Q

What is the first line antibiotic for Campylobacter Jejuni ?

A

Clarithromycin

57
Q

What are the general principles of management in food poisoning?

A

faeces sample for microscopy, culture and sensitivities
IV fluids, oral rehydration salts
avoid antidiarrheal drugs antiemetics
stay off school/work for 48hrs after symptoms resolve

58
Q

state 4 post-gastroenteritis complications

A

Lactose intolerance
Irritable bowel syndrome
Reactive arthritis
Guillain–Barré syndrome
Haemolytic uraemic syndrome

59
Q

What is C.diff infection associated with?

A

repeated use of antibiotics, proton-pump inhibitors (e.g., omeprazole) and healthcare settings

60
Q

State 4 antibiotics associated with C.diff

A

Clindamycin
Ciprofloxacin (and other fluoroquinolones)
Cephalosporins
Carbapenems (e.g., meropenem)

61
Q

What are the presenting features of C.diff?

A

Colonisation is usually asymptomatic.

Infection presents with diarrhoea, nausea and abdominal pain.

Severe infection with colitis can present with:

Dehydration
Systemic symptoms (e.g., fever, tachycardia and hypotension)

62
Q

How do you investigate for C.diff??

A

Diagnosis is based on stool samples. Stools can be tested for:

C. difficile antigen (specifically glutamate dehydrogenase)
A and B toxins (by PCR or enzyme immunoassay)

63
Q

How is C.diff managed?

A

Management is with supportive care and oral antibiotics. The options are:

Oral vancomycin (first-line)
Oral fidaxomicin (second-line)

64
Q

state 4 complications of C.diff

A

Pseudomembranous colitis
toxic megacolon
bowel perforation
sepsis

65
Q

State 4 causes of bacterial meningitis

A

Neisseria meningitidis
Streptococcus pneumoniae (pneumococcus)
Haemophilus influenzae
Group B streptococcus (GBS) (particularly in neonates as GBS may colonise the vagina)
Listeria monocytogenes (particularly in neonates)

66
Q

What type of bacteria is Neisseria meningitidis ?

A

gram negative diplococcus

67
Q

What is the difference between Meningococcal meningitis and meningococcal septicaemia?

A

Meningococcal meningitis is when the bacteria infects the meninges and the cerebrospinal fluid. Meningococcal septicaemia is when the meningococcus bacterial infection is in the bloodstream. Meningococcal septicaemia can cause the classic non-blanching rash

68
Q

State the 3 most common causes of viral meningitis

A

Enteroviruses (e.g., coxsackievirus)
Herpes simplex virus (HSV)
Varicella zoster virus (VZV

69
Q

What are the typical symptoms of meningitis?

A

Fever
Neck stiffness
Vomiting
Headache
Photophobia
Altered consciousness
Seizures

70
Q

What are the 2 special tests you can do to look for meningeal irritation?

A

Kernig’s test
Brudzinski’s test

71
Q

How do you do the Kernig’s test?

A

lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees. This creates a slight stretch in the meninges. Where there is meningitis, it will produce spinal pain or resistance to movement.

72
Q

How do you do the Brudzinski’s test?

A

lying the patient flat on their back and gently using your hands to lift their head and neck off the bed, flexing their chin to their chest. A positive test, indicating meningitis, is when this causes the patient to flex their hips and knees involuntarily

73
Q

What will CSF in bacterial meningitis show?

A

Appearance = cloudy
Protein = high
Glucose = low
WCC = high (neutrophils)

74
Q

What will the CSF show in viral meningitis?

A

Appearance = clear
Protein = mildly raised or normal
Glucose = normal
WCC = high (lymphocytes)

75
Q

What are the doses of IM benzylpenicillin with suspected meningitis with a non-blanching rash?

A

Under 1 year – 300mg
1-9 years – 600mg
Over 10 years – 1200mg

76
Q

What is the treatment of bacterial meningitis?

A

Under 3 months – cefotaxime plus amoxicillin (amoxicillin is to cover listeria)
Above 3 months – ceftriaxone

77
Q

what should be given to contacts of a person with meningococcal infection?

A

single dose of ciprofloxacin

78
Q

State 4 complications of meningitis

A

Hearing loss (a key complication)
Seizures and epilepsy
Cognitive impairment and learning disability
Memory loss
Focal neurological deficits, such as limb weakness or spasticity

79
Q

What causes Tuberculosis?

A

Mycobacterium tuberculosis

80
Q

what stain is used to identify mycobacterium tuberculosis?

A

Zeihl-Neelsen stain

81
Q

State 3 risk factors for TB

A

Close contact with active tuberculosis (e.g., a household member)
Immigrants from areas with high tuberculosis prevalence
People with relatives or close contacts from countries with a high rate of TB
Immunocompromised (e.g., HIV or immunosuppressant medications)
Malnutrition, homelessness, drug users, smokers and alcoholics

82
Q

What vaccine is given to prevent TB?

A

BCG

83
Q

How may TB present?

A

Cough
Haemoptysis
Lethargy
Fever or night sweats
Weight loss
Lymphadenopathy
Erythema nodosum
Spinal pain in spinal tuberculosis

84
Q

What are the 2 tests for an immune response to TB?

A

Mantoux test
Interferon‑gamma release assay (IGRA)

85
Q

What would TB show in CXR?

A

Primary tuberculosis may show patchy consolidation, pleural effusions and hilar lymphadenopathy.

Reactivated tuberculosis may show patchy or nodular consolidation with cavitation (gas-filled spaces), typically in the upper zones.

Disseminated miliary tuberculosis gives an appearance of millet seeds uniformly distributed across the lung fields

86
Q

What is the treatment of latent tuberculosis?

A

Isoniazid and rifampicin for 3 months
Isoniazid for 6 months

87
Q

What is the treatment of active tuberculosis?

A

R – Rifampicin for 6 months
I – Isoniazid for 6 months
P – Pyrazinamide for 2 months
E – Ethambutol for 2 months

88
Q

What are the side effects of Rifampicin?

A

red/orange urine/tears
cytochrome P450 inducer

89
Q

What is the main side effect of Isoniazid?

A

peripheral neuropathy
co-prescribe B6 to reduce risk

90
Q

What are the key side effects of Ethambutol?

A

Colour blindness
reduced visual acuity

91
Q

what does HIV use as a host cell?

A

CD4 T-helper cells

92
Q

how is HIV transmitted?

A

Unprotected anal, vaginal or oral sexual activity
Mother to child at any stage of pregnancy, birth or breastfeeding (called vertical transmission)
Mucous membrane, blood or open wound exposure to infected blood or bodily fluids (e.g., sharing needles, needle-stick injuries or blood splashed in an eye)

93
Q

State 4 AIDS-defining illnesses

A

Kaposi’s sarcoma
Pneumocystis jirovecii pneumonia (PCP)
Cytomegalovirus infection
Candidiasis (oesophageal or bronchial)
Lymphomas
Tuberculosis

94
Q

at what CD4 count is a patient at high risk of opportunistic infections?

A

Under 200 cells/mm3

95
Q

What is an undetectable viral load?

A

HIV RNA is below recordable range if 20 copies/ml

96
Q

What is the management of HIV?

A

ART regime

97
Q

What is given to HIV patients with a low CD4 count to prevent pneumocystis jirovecii pneumonia?

A

prophylactic co-trimoxazole

98
Q

What is the most severe type of malaria?

A

plasmodium falciparum

99
Q

How is malaria spread?

A

female Anopheles mosquitoes

100
Q

What are the symptoms of malaria?

A

Fever (up to 41ºC) with sweats and rigors
Fatigue
Myalgia (muscle aches and pain)
Headache
Nausea
Vomiting

101
Q

What signs may be seen in a patient with malaria?

A

Pallor due to the anaemia
Hepatosplenomegaly
Jaundice

102
Q

How is malaria diagnosed?

A

malaria blood film (3 -ve samples over 3 consecutive days required to exclude)

103
Q

What is the usual first line treatment of malaria?

A

Artemether with lumefantrine (Riamet)

104
Q

state 3 complications of malaria

A

Cerebral malaria
Seizures
Reduced consciousness
Acute kidney injury
Pulmonary oedema
Disseminated intravascular coagulopathy (DIC)
Severe haemolytic anaemia
Multi-organ failure and death

105
Q

What are the options for preventing malaria

A

advice - nets, spray
antimalarials e.g. malarone, doxycyline