Antimicrobial Chemotherapy- commonly used agents and side effects Flashcards
Describe the trends in activity through the cephalosporins generations?
Gram negative activity- increases through generations
Gram positive activity- decreases through generations
Give characteristics of quinolones?
This group provides virtually the only possibility for
oral therapy in the treatment of pseudomonas infections.
wide spectrum of action
active against nearly all Gram negative organisms including pseudomonas
What is the most commonly used quinolone and what is it used for?
Levofloxacin
Activity against streptococci is generally poor, levofloxacin is active against pneumococci and the organisms causing atypical pneumonia.
What is metronidazole and give characteristics?
nucleic acid synthesis inhibitor
effective towards gram positive and gram negative bacteria
What is fusidic acid and give characteristics?
protein synthesis inhibitor
Used only as an anti-staphylococcal drug.
Stap. aureus can develop resistance very readily to this agent.
It should always be used in combination with other anti-staphylococcal drugs (i.e. flucloxacillin).
What are tetracyclines and give characteristics?
Broad spectrum agents which inhibit bacterial protein synthesis and have a few limited applications nowadays.
Useful for some genital tract (chlamydia) and
respiratory tract infection (e.g. psittacosis, Mycoplasma pneumoniae
What is Clindamycin and give characteristics?
The only lincosamide antibiotic in common use and has good activity against Gram-positive organisms such as staphylococci and streptococci.
It also has good activity against anaerobes
The advantages of clindamycin are that it has very good
tissue penetration – e.g. into bone – and can be taken orally.
The disadvantage is that it is a common cause of pseudo-membranous colitis.
What agents ARE ONLY used in the treatment of UTI (cystitis)?
nalidixic acid (Quinolone)- Urinary antiseptic with activity only against Gram-negative aerobes (coliform) organisms.
Completely excreted in urine, the only indication for its use is coliform urinary tract infections.
Nitrofurantoin (Quinolone)- It is effective against most Gram-negative organisms.
(with the exception of Proteus and Pseudomonas spp.)
Also effective against some Gram-positive organisms.
What agents cause allergic reactions?
allergic reactions from any antimicrobial: commonly associated with the β-lactam.
True penicillin hypersensitivity is rare.
Approx. 10% of truly penicillin allergic patients also allergic to cephalosporins.
What is anaphylactic shock and how does it develop?
Immediate hypersensitivity
(parenteral administration of the antibiotic).
IgE mediated occurs within minutes of administration.
Itching, urticaria, nausea, vomiting, wheezing and shock.
Laryngeal oedema may prove fatal unless the airway is cleared.
Describe delayed hypersensitivity?
Hours or days to develop:
immune complex or cell mediated mechanism.
Rashes, fever, serum sickness and erythema nodosum may also occur.
Rashes are usually maculopapular and restricted to the skin.
What is stevens-johnson syndrome?
severe and sometimes fatal
hypersensitivity linked to the sulphonamides (skin and mucous membranes are involved).
Common gastrointestinal effects?
nausea and vomiting
What is diarrhoea associated with?
Diarrhoea associated with toxin production by Clostridium difficile.
Describe C.diff?
C. difficile anaerobic Gram-positive bacillus asymptomatic in the GI tract, overgrow normal flora during antibiotic therapy and produces toxins.
Relapses are common, further courses of treatment may be required.
C. difficile is a spore forming organism,
hand hygiene is particularly important for all healthcare staff.
