Gram Negatives Flashcards
describe the structure of a Gm -ve cell wall
Inner and outer membrane
thin layer of peptidoglycan between
Lipopolysaccharides facing external environment
Which of the classes in the 4C antibiotics is used to treat legionella pneumonia?
Quinolones ( Ciprofloxacin in the 4Cs )
Tx:
Levofloxacin and Co-amoxiclav
What monobactam is used in NHS Tayside?
Aztreonam
Aztreonam only treats Gm -ves. TRUE/FALSE?
TRUE
does not offer any Gm +ve or anaerobe cover
Aztreonam is an alternative to Gentamicin in what group of patients?
Renal impairment
Why should Gentamicin not be given to patients with Myasthenia Gravis?
- Impairs neuromuscular transmission
- Causes muscle weakness and therefore resp. depression in these patients
What groups of antibiotics may offer Gm -ve cover?
- Beta lactams ( and monobactam )
- Aminoglycosides
- Macrolides
- Tetracyclines
- Chloramphenicol
- Co-trimoxazole
- polymixins
Are most Gm -ve infections cocci or bacilli shaped?
Bacilli
only true coccus is Neisseria Veillonella
What factors should be considered when pneumonia is suspected?
Hospital or community acquired? Ventilated not ventilated? Time of year/ season Immunosuppressed? Pre-existing chronic lung disease Epidemiological exposures (e.g. PWID, vaccine status) Travel ( e.g. for resistant gram negs)
Describe the Gram stain and shape of haemophilus influenzae
Gm -ve coccobacillus
What agar is required for growth of haemophilus influenzae?
Chocolate agar media
What antibiotics are active against haemophilus influenzae in the UK?
Amoxicillin
Doxycycline also active
What is meant by “atypical” pneumonia?
Any infection causing pneumonia which is NOT strep. pneumoniae
e.g. Mycoplasma /Coxiella burnetii / Legionella pneumophila
What treatment is commonly used for “atypical pneumonia”?
- Doxycycline (not very effective against Legionella though)
- Clarithromycin
- Levofloxacin in penicillin allergic severe pneumonia and for Legionella NOTE Cdiff risk
Where is Legionella commononly found in the environment?
Lukewarm aerosolised water ( showers, air conditioning, taps, hot tubs )
Who is more at risk of legionella infection?
- smokers
- males
- COPD
- Immunosuppressed
- Malignancy
- Diabetes
- dialysis
What serogroup of Legionella is responsible for most disease?
Serogroup 1
What bacteria are most important with regards to Gm -ve sepsis?
E-coli
Pseudomonas
Neisseria meningitidis
these 3 = most important
Other causes: Klebsiella Serratia Acinetobacter Enterobacter Citrobacter
What colour change is observed on MacConkey Agar with sorbitol for Ecoli0157?
changes to bright pink
Coliforms covers what types of bacteria?
E-coli Klebsiella sp Proteus sp. Enterobacter sp. Serratia sp.
Give examples of antibiotics which contain another ingredient to breakdown beta-lactamase and attempt to prevent antibiotic resistance
Co amoxiclav (clavulanic acid)
Tazocin (Tazobactam agent)
Extended spectrum beta lactamase organisms rule out what antibiotics?
Penicillins, cephalosporins and aztreonam
What should be remembered when prescribing for obese and pregnant patients?
They may require extra antibiotic coverage for distribution
Some guidelines are based on a 70kg man (which is not the case in todays society)
Why is trimethoprim NOT used in sepsis?
It is bacteriostatic