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Infectious diseases Flashcards

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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
State 4 common bacterial causes of a UTI
E.coli Klebsiella pneumoniae Enterococcus Pseudomonas aeruginosa Staphylococcus saprophyticus
26
What are the 2 first line treatment options for a lower UTI?
Nitrofurantoin (avoided in patients with an eGFR <45) Trimethoprim (often associated with high rates of bacterial resistance)
27
What is the typical duration of antibiotics in a lower UTI?
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
28
What are the treatment options for pyelonephritis and for how long?
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)
29
What does UTI in pregnancy increase the risk of?
pyelonephritis, premature rupture of membranes and pre-term labour
30
How do you manage a UTI in pregnancy?
7 days Nitrofurantoin (avoided in the third trimester) Amoxicillin (only after sensitivities are known) Cefalexin (the typical choice)
31
Why should Nitrofurantoin be avoided in the third trimester?
risk of neonatal haemolysis
32
What are the skin changes seen in cellulitis?
Erythema (red discolouration) Warm or hot to touch Tense Thickened Oedematous Bullae (fluid-filled blisters) A golden-yellow crust indicates a Staphylococcus aureus infection
33
What are the 3 most common causes of cellulitis?
Staphylococcus aureus Group A streptococcus (mainly streptococcus pyogenes) Group C streptococcus (mainly streptococcus dysgalactiae)
34
What is the Eron classification used for?
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
35
what is the 1st line antibiotic for cellulitis?
Flucloxacillin Alternatives: Clarithromycin Clindamycin Co-amoxiclav (the usual first choice for cellulitis near the eyes or nose)
36
What is bacterial tonsillitis most commonly caused by?
group A streptococcus mainly streptococcus pyogenes
37
What is the Centor criteria?
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
38
What is the FeverPAIN score?
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
39
What is the first line antibiotic in bacterial tonsilitis?
Penicillin V (phenoxymethylpenicillin) for a 10-day course Clarithromycin is the usual first-line choice in true penicillin allergy.
40
State 4 complications of tonsillitis
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
41
What are the 1st and 2nd line antibiotics for otitis media?
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.
42
What is prescribed for patients with sinusitis who's symptoms are not improving after 10 days?
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)
43
What are some common bacterial causes of intra-abdominal infections?
Anaerobes (e.g., Bacteroides and Clostridium) E. coli (gram-negative) Klebsiella (gram-negative) Enterococcus (gram-positive) Streptococcus (gram-positive)
44
What is the mortality rate in septic arthritis?
10%
45
What are the presenting symptoms of septic arthritis?
A hot, red, swollen and painful joint Stiffness and reduced range of motion Systemic symptoms, such as fever, lethargy and sepsis
46
What is the most common causative organism in septic arthritis?
Staphylococcus aureus
47
State 4 differentials of septic arthritis
Gout Pseudogout Reactive arthritis Haemarthrosis (bleeding into the joint, usually after trauma)
48
What is the management of septic arthritis?
Joint aspiration ( sent for gram staining, crystal microscopy, culture and antibiotic sensitivities) Empirical IV antibiotics (4-6w) often flucloxacillin
49
What type of virus is influenza?
RNA virus
50
Who is offered the flu vaccine?
Aged 65 and over Young children Pregnant women Chronic health conditions, such as asthma, COPD, heart failure and diabetes Healthcare workers and carers
51
What are the two options for treatment in someone at risk of complications of influenza?
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
state 4 complications of influenza
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
state 3 viruses that can cause gastroenteritis
Rotavirus Norovirus Adenovirus
54
What are the symptoms of travellers' diarrhoea caused by Campylobacter Jejuni
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
How is Campylobacter Jejuni spread?
Raw or improperly cooked poultry Untreated water Unpasteurised milk
56
What is the first line antibiotic for Campylobacter Jejuni ?
Clarithromycin
57
What are the general principles of management in food poisoning?
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
state 4 post-gastroenteritis complications
Lactose intolerance Irritable bowel syndrome Reactive arthritis Guillain–Barré syndrome Haemolytic uraemic syndrome
59
What is C.diff infection associated with?
repeated use of antibiotics, proton-pump inhibitors (e.g., omeprazole) and healthcare settings
60
State 4 antibiotics associated with C.diff
Clindamycin Ciprofloxacin (and other fluoroquinolones) Cephalosporins Carbapenems (e.g., meropenem)
61
What are the presenting features of C.diff?
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
How do you investigate for C.diff??
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
How is C.diff managed?
Management is with supportive care and oral antibiotics. The options are: Oral vancomycin (first-line) Oral fidaxomicin (second-line)
64
state 4 complications of C.diff
Pseudomembranous colitis toxic megacolon bowel perforation sepsis
65
State 4 causes of bacterial meningitis
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
What type of bacteria is Neisseria meningitidis ?
gram negative diplococcus
67
What is the difference between Meningococcal meningitis and meningococcal septicaemia?
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
State the 3 most common causes of viral meningitis
Enteroviruses (e.g., coxsackievirus) Herpes simplex virus (HSV) Varicella zoster virus (VZV
69
What are the typical symptoms of meningitis?
Fever Neck stiffness Vomiting Headache Photophobia Altered consciousness Seizures
70
What are the 2 special tests you can do to look for meningeal irritation?
Kernig’s test Brudzinski’s test
71
How do you do the Kernig's test?
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
How do you do the Brudzinski's test?
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
What will CSF in bacterial meningitis show?
Appearance = cloudy Protein = high Glucose = low WCC = high (neutrophils)
74
What will the CSF show in viral meningitis?
Appearance = clear Protein = mildly raised or normal Glucose = normal WCC = high (lymphocytes)
75
What are the doses of IM benzylpenicillin with suspected meningitis with a non-blanching rash?
Under 1 year – 300mg 1-9 years – 600mg Over 10 years – 1200mg
76
What is the treatment of bacterial meningitis?
Under 3 months – cefotaxime plus amoxicillin (amoxicillin is to cover listeria) Above 3 months – ceftriaxone
77
what should be given to contacts of a person with meningococcal infection?
single dose of ciprofloxacin
78
State 4 complications of meningitis
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
What causes Tuberculosis?
Mycobacterium tuberculosis
80
what stain is used to identify mycobacterium tuberculosis?
Zeihl-Neelsen stain
81
State 3 risk factors for TB
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
What vaccine is given to prevent TB?
BCG
83
How may TB present?
Cough Haemoptysis Lethargy Fever or night sweats Weight loss Lymphadenopathy Erythema nodosum Spinal pain in spinal tuberculosis
84
What are the 2 tests for an immune response to TB?
Mantoux test Interferon‑gamma release assay (IGRA)
85
What would TB show in CXR?
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
What is the treatment of latent tuberculosis?
Isoniazid and rifampicin for 3 months Isoniazid for 6 months
87
What is the treatment of active tuberculosis?
R – Rifampicin for 6 months I – Isoniazid for 6 months P – Pyrazinamide for 2 months E – Ethambutol for 2 months
88
What are the side effects of Rifampicin?
red/orange urine/tears cytochrome P450 inducer
89
What is the main side effect of Isoniazid?
peripheral neuropathy co-prescribe B6 to reduce risk
90
What are the key side effects of Ethambutol?
Colour blindness reduced visual acuity
91
what does HIV use as a host cell?
CD4 T-helper cells
92
how is HIV transmitted?
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
State 4 AIDS-defining illnesses
Kaposi’s sarcoma Pneumocystis jirovecii pneumonia (PCP) Cytomegalovirus infection Candidiasis (oesophageal or bronchial) Lymphomas Tuberculosis
94
at what CD4 count is a patient at high risk of opportunistic infections?
Under 200 cells/mm3
95
What is an undetectable viral load?
HIV RNA is below recordable range if 20 copies/ml
96
What is the management of HIV?
ART regime
97
What is given to HIV patients with a low CD4 count to prevent pneumocystis jirovecii pneumonia?
prophylactic co-trimoxazole
98
What is the most severe type of malaria?
plasmodium falciparum
99
How is malaria spread?
female Anopheles mosquitoes
100
What are the symptoms of malaria?
Fever (up to 41ºC) with sweats and rigors Fatigue Myalgia (muscle aches and pain) Headache Nausea Vomiting
101
What signs may be seen in a patient with malaria?
Pallor due to the anaemia Hepatosplenomegaly Jaundice
102
How is malaria diagnosed?
malaria blood film (3 -ve samples over 3 consecutive days required to exclude)
103
What is the usual first line treatment of malaria?
Artemether with lumefantrine (Riamet)
104
state 3 complications of malaria
Cerebral malaria Seizures Reduced consciousness Acute kidney injury Pulmonary oedema Disseminated intravascular coagulopathy (DIC) Severe haemolytic anaemia Multi-organ failure and death
105
What are the options for preventing malaria
advice - nets, spray antimalarials e.g. malarone, doxycyline

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