Bacterial Infection Flashcards
When selecting an antibacterial, the causative organism should be considered in addition to
patient factors such as allergy, renal/hepatic impairment, immune function, availability of oral route, severity, age, taking contraceptive pills, pregnancy or breastfeeding.
• Viral infections should not be treated with antibacterials unless
there is a secondary bacterial infection.
- Clostridium difficile can be treated with
Metronidazole 1st line or Vancomycin
- Endocarditis is treated blind with
Amoxicillin then Gentamicin until the causative organism is identified.
- Acute exacerbations of Chronic Bronchitis are treated with
Amoxicillin or a Tetracycline
- Community Acquired Pneumonia is treated with
Amoxicillin and Clarithromycin
- Hospital Acquired Pneumonia is treated with
Co-Amoxiclav or Cefuroxime
- UTIs are treated with
Trimethoprim or Nitrofurantoin
- Chlamydia and Gonorrhoea are treated with
Azithromycin
- Septicaemia is treated with
Tazocycin or Cefuroxime
- Gingivitis is treated with
Metronidazole
- Otitis externa is treated with…
Flucloxacillin
- Cellulitis is treated with
Flucloxacillin
- Patients with Asplenia or Sickle-cell disease are prophylactically treated for Pneumococcal infection with
Phenoxymethylpenicillin.
- Prophylaxis of Meningococcal Meningitis:
Ciprofloxacin or Rifampicin
Otitis media is treated with
Amoxicillin
Gentamicin should not be given at the same time as
Furosemide due to the risk of ototoxicity and nephrotoxicity!
Aminoglycosides - Examples include
Gentamicin + Neomycin. All are bactericidal and active against some Gram-Positive and many Gram-Negative organisms.
Aminoglycosides absorption
- They are not absorbed from the gut and therefore must be given by Injection for systemic infections.
Aminoglycoside of choice in the UK
- Gentamicin is the aminoglycoside of choice in the UK and is used widely for the treatment of serious infections. It has a broad-spectrum but is inactive against anaerobes and has poor activity against haemolytic streptococci and pneumococci.
- Aminoglycoside Loading and maintenance doses are calculated based on
the patient’s ideal bodyweight and renal function. Dose adjustments are then made based on serum levels; blood levels should be taken 1 hour after a dose and just before the next dose to establish the PEAK and trough concentrations.
Aminoglycoside treatment should not exceed
7 days and it should be avoided in pregnancy
Aminoglycoside dosing regimen
- ONCE daily administration of aminoglycosides is more convenient + provides adequate serum concentrations.
- But a ONCE daily, high dose regimen should be avoided in patients with endocarditis due to Gram-positive bacteria, HACEK endocarditis, burns of >20% of body surface area or CrCl less than 20mL/minute.
Carbapenems
The Carbapenems are beta-lactam antibacterials with a BROAD-SPECTRUM of activity which includes many Gram-Positive and Gram-Negative bacteria and anaerobes.
Carbapenems examples
- Examples include Imipenum and Meropenum which have good activity against Pseudomonas Aeruginosa.
Carbapenems are used for
the treatment of severe hospital-acquired infections + polymicrobial infections including septicaemia, hospital-acquired pneumonia, intra-abdominal infections, skin + soft tissue infections + complicated UTIs.
Ertapenem is licensed for
treating abdominal + gynaecological infections and for CAP. It is also licensed for treating foot infections of the skin and soft tissue in patients with diabetes. However, it is not active against Pseudomonas.
Imipenum is partially inactivated in
the kidney by enzymatic activity and is therefore administered with Cilastatin (an enzyme inhibitor) which blocks renal metabolism. Meropenum and Ertapenem are stable to the renal enzyme and therefore can be given without Cilastatin.
Cephalosporins
The cephalosporins are broad-spectrum antibiotics which are used to treat many infections.
Cephalosporins examples
Cefotaxime, Cefuroxime and Cefalexin
- They penetrate the cerebrospinal fluid poorly unless the meninges are inflamed.
Suitable drugs for infections of the CNS (e.g. meningitis).
Cefotaxime and Ceftriaxone
- ‘first generation’ cephalosporins (cefalexin) and the ‘second generation’ cephalosporin, cefaclor, are
useful for UTIs which do not respond to other drugs or which occur in pregnancy.
- Cefuroxime axetil is
poorly absorbed and needs to be given with food to maximise absorption
Ceftriaxone has a
longer half-life and only needs to be given ONCE daily.
Cephalosporins - Treatment by mouth usually involves
cefalexin; it can be given in pregnancy and breast-feeding and is taken four times a day
Cephalosporins interactions
Cephalosporins possibly increase the anticoagulant effect of Warfarin.
Macrolides are
broad-spectrum antibiotics like Penicillin’s but are unrelated. Hence, they can be given as an alternative in penicillin-allergic patients.
Macrolides examples
Azithromycin, Clarithromycin and Erythromycin.
Erythromycin causes
- Erythromycin causes nausea, vomiting + diarrhoea in some patients. In mild-moderate infections this can be avoided by giving a lower dose, but if a more SERIOUS infection is suspected… HIGHER doses are needed.
With Azithromycin…
- With Azithromycin plasma concentrations are very low, but tissue concentrations are much HIGHER. It has a long tissue half-life and ONCE daily dosage is recommended. Do not take indigestion remedies 2 hours before/after taking this medication.
Clarithromycin is
an erythromycin derivative with slightly greater activity. Tissue concentrations are HIGHER than with Erythromycin and it is given TWICE daily.
Clarithromycin should be avoided in
- pregnancy and breast-feeding