Infectious diseases Flashcards
Difference between gram positive and gram negative bacteria? Give an example of each.
Gram positive: thick peptidoglycan cell wall, stains purple with crystal violet
Cocci - staphlycoccus, streptococcus, enterococcus, anaerobes
Gram negative: don’t stain with crystal violet but stains pink with safranin. Eg niesseria, haemophila, escherisca, klebsiella, moraxella
What is an atypical bacteria? Give 3 examples.
One that cannot be stained or cultured in the normal way. Legions – Legionella pneumophila of Psittaci – Chlamydia psittaci M – Mycoplasma pneumoniae C – Chlamydydophila pneumoniae Qs – Q fever (coxiella burneti)
Give 3 gram +ve bacilli.
Bacillus, Mycobacteria, Corneybacteria, Listeria, Nocardia
Give 3 gram positive anaerobes.
Clostridium, Lactobacillus, Antinomyces, Proprionibacterium
Give 3 gram negative bacteria.
Neisseria meningitis Neisseria gonorrhoea Haemophilia influenza E. coli Klebsiella Pseudomonas aeruginosa Moraxella catarrhalis
How is MRSA treated?
Trust guidelines.
Options: Doxycycline, clindamycin/vancomycin, teicoplanin, linezolid
Prevention in surgery with chlorhexidine body wash and antibacterial nasal creams
What are ESBLs and how are they treated?
Extended Spectrum Beta Lactamase bacteria. Resistant to beta-lactam abx. E coli/klebsiella common –> UTIs. Treat with carbapenems eg meropenem/imipenem
How do carbapenems work?
Inhibit cell wall synthesis.
Give 2 antibiotics which interfere with folic acid metabolism.
Sulfamethoxazole blocks the conversion of PABA to DHFA
Trimethoprim blocks the conversion of DHFA to THFA
Co-trimoxazole is a combination of sulfamethoxazole and trimethoprim
How does metronidazole work?
Reduced to active form in anaerobic cells only. Inhibits nucleic acid synthesis.
How do macrolides work? Give 3 examples
Inhibit protein synthesis by targeting the ribosome.
Erythromycin, clarithromycin, azithromycin.
Which antibiotics are contraindicated in penicillin allergy?
Penicillins - amox, fluclox, co-amox, tazocin;
1% of patients with pen allergy have reaction to cephalosporins (ceftriaxone) and carbapenems (meropenem).
What does amoxicillin cover?
Streptococcus (eg strep pneumoniae in pneumonia), listeria, enterococcus
What does co-amoxiclav cover?
Streptococcus (eg strep pneumoniae in pneumonia), listeria, enterococcus
+ staphylococcus, haemophilus, E. Coli.
What does tazocin cover?
Streptococcus (eg strep pneumoniae in pneumonia), listeria, enterococcus
+ staphylococcus, haemophilus, E. Coli.
+ pseudomonas
What does meropenem cover that tazocin doesn’t?
ESBLs and n. meningitides
What does teicoplanin cover that co-amoxiclav doesn’t?
MRSA
What does doxycycline cover which amoxicillin doesn’t?
Staph aureus, MRSA, h. influenzae, Atypicals, moraxella catarrhalis
What is sepsis? How is it defined?
Major immune response to infection that causes systemic inflammation and organ dysfunction. Hypoxia Oliguria Acute Kidney Injury Thrombocytopenia Coagulation dysfunction Hypotension Hyperlactaemia (> 2 mmol/L)
Why is lactate raised in sepsis?
Hypoperfusion of tissues –> anaerobic perfusion –> raised lactate
What is septic shock?
Arterial blood pressure drops and results in organ hypo-perfusion
Measured by BP <90 after fluid resuscitation or lactate >4
Give IV fluids, inotropes if that doesn’t work
What is the pathophysiology of sepsis?
- Macrophages, lymphocytes and mast cells release cytokines (IL, TNF).
- These trigger immune system to release nitrous oxide –> vasodilation, and increases endothelial permability, leading to oedema, reduces oxygen supply to tissues
- Activation of coagulation system leads to fibrin deposition compromising organ and tissue perfusion, and DIC as platelets/clotting factors are used up in clots so none left to stop bleeding.
- Hypoperfusion of tissues –> anaerobic perfusion –> raised lactate
Give 5 risk factors for sepsis.
Under 1 or over 75 years
Chronic conditions such as COPD and diabetes
Chemotherapy, immunosuppressants or steroids
Surgery or recent trauma or burns
Pregnancy or peripartum
Indwelling medical devices such as catheters or central lines
How does sepsis present? Give 5 signs
Raised EWS
Signs of potential sources such as cellulitis, discharge from a wound, cough or dysuria
Non-blanching rash can indicate meningococcal septicaemia
Reduced urine output
Mottled skin
Cyanosis
Arrhythmias such as new onset atrial fibrillation
High respiratory rate (tachypnoea) is often the first sign
Elderly patients often present with confusion or drowsiness or simply “off legs”
Neutropenic or immunosuppressed patients may have normal observations and temperature despite being life threatening unwell
