advanced infections Flashcards
what is the key principle when developing antimicrobial agent
selective toxicity: need to kill/inhibit growth of pathogenic cells but have no effect on host cells (human)
give examples of commonly prescribe antibiotics that require monitoring
-Gentamicin
-Vancomycin
-Teicoplanin
-Amikacin
-Tobramycin
-Chloramphenicol (I/v use)
what bacteria does gentamicin mainly target
-gram negative which is usually responsible for urosepsis (sepsis caused by UTIs)
what are the side effects of gentamicin associated with ears
- cochlear and vestibular apparatus damage = loss balance, tinnitus (ringing in ears), hearing loss
-concurrent use with ototoxic diuretics e.g. furosemide = increased risk of ototoxicity
what are the side effects of gentamicin associated with kidneys
-renal damage as nephrotoxicity risk increased with prolonged treatment
-not to use with other nephrotoxic drugs
-use with ototoxic diuretics = nephrotoxicity risk increased
can gentamicin cause allergic reaction and what is associated with this
yes and nausea, vomiting and rashes
what is gentamicin contraindicated in?
severe renal impairment and pregnancy
how to prevent ototoxicity and nephrotoxicity with gentamicin
dose according to ideal body weight (if they are obese) and monitor plasma conc to avoid accumulation
what are the 2 ways to administer and monitor gentamicin therapy
- multiple dosing regimen = monitoring peak levels approx 30 mins after admin & trough level (prior to admin). ( mainly used in heart infections e.g. endocarditis)
- Hartford nomogram = consistent dose of 7mg/kg calc from lower value of ideal weight or actual weight…. plasma con mesaured 6-14hrs post 1st dose = dosage interval …. this used to determine if dosing should be every 24 or 36 or 48 hrs
what bacteria causes TB
mycobacterium tuberculosis & occasionally M. bovis or M. africanum
what is mycobacterium
slow growing aerobic rod shaped bacteria which increases with poor social conditions, inadequate nutrition, and overcrowding
-has lipid rich cell wall = retains dyes & resists decolourisation with acid (acid fast bacilli)
how is TB spread
inhalation of droplets, meaning lungs first infected, but has to be prolonged close contact
what is the host initial response to TB
-cell mediated immune system response .
-disease may reactivate if immunity falls at later stage = 10% estimated lifetime risk
what happens if TB spreads from primary focus to the rest of the body
resolve spontaneously or develop into localised infection (limited to specific area / organ) e.g. meningitis
name some risk factors associated with TB
- Social deprivation – overcrowding e.g. prisons, poverty, homelessness
- HIV
- Diabetes
- Malignancy
- TNF antagonist therapy
- Immigration e.g. cities, from high incidence area
- Close contacts of TB cases
- Living in high incidence area
what symptoms are associated with TB
-mimics inflammatory & malignant diseases
- early stages symptomless
-presents with : chronic cough, haemoptysis(coughing up blood), shortness of breath,
fever & weight loss
presenting symptoms of TB meningitis (when its spreading)
fever, headache, neck stiffness and slowly deteriorating level of consciousness
what is miliary TB
-minute tubercles form in different organs due to spread of bacilli through body in blood
-more common in infants/ young children
what is common in advanced TB and what does this affect
-extra-pulmonary TB
which affects liver, spleen, pancreas,
bone marrow
how is TB diagnosed
clinical signs and symptoms, radiographic appearances and
laboratory investigations
what investigation required in TB
- 3 sputum samples for microscopy and culture = test for presences of acid fast bacilli
- chest x ray
what treatment regimen is used for TB and why
-Combination treatment = prevent drug resistance
- Prolonged treatment as bacteria grows slow…. 6 months treatment recommended
what are the 2 phases for TB treatment
- Initial phase for 2 months – rifampicin, isoniazid, pyrazinamide & ethambutol
= eradicate actively growing & semi-dormant bacilli. - Continuation phase for 4 months – rifampicin & isoniazid= eliminate residual bacilli & reduce the risk of treatment failure or relapse
how does treatment in CNS TB differ
- for 12 months and a glucocorticoid added in beginning of treatement e.g. prednisolone, dexamethasone
at what point is pulmonary tb usually not infectious
after 2 weeks with appropriate treatment
what are the risk factors for MDR- TB in uk
-prior tb treatment + failure
-male gender
-HIV positive
what is offered for patients who cannot comply to treatment for TB
directly observed therapy offered
-mainly offered to homeless or drug or alcohol misusers
name side effects of TB treatment
-GI symptoms
- Non-gouty polyarthritis - pyrazinamide
- Rash – rifampicin
- Urine and bodily fluid discolouration - rifampicin
- Drug fever – temperature > 39°C & patient well
- Hepatotoxicity
- Peripheral neuropathy - isoniazid
- Flu-like symptoms - rifampicin
- Optic neuritis – ethambutol
when is pyridoxine prophylactically given in TB and what does this do
- patients with diabetes, alcohol
dependence, chronic kidney disease, pregnancy, malnutrition, and HIV infection. - reduces the risk of peripheral neuropathy with isoniazid
how is adherence to TB medication promoted
-Urine drug assays
- Examination of urine colour
- Tablet counts
- Controlled dosage systems
- Tablet diaries
- Signed care contracts
- Incentive schemes
- Reminder letters
- Education & Information
- Liquid formulation as appropriate
- DOT (directly observed therapy)
what vaccine is available for TB
BCG
