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Sepsis > Gram negatives > Flashcards

Gram negatives Flashcards

1
Q

gram negative cell

A

lipopolysaccharide

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2
Q

what is the primary driver for sepsis in gram negatives

A

lipopolysaccharide layer

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3
Q

features of a gram negative cells?

A

The Gram negative cell envelope contains an additional outer membrane composed by phospholipids and lipopolysaccharides which face the external environment.
• The highly charged nature of lipopolysaccharides confer an overall negative charge to the Gram negative cell wall.
• The chemical structure of the outer membrane lipopolysaccharides is often unique to specific bacterial strains (i.e. sub-species)
• It is responsible for many of the antigenic properties of these strains. Many species of Gram-negative bacteria are pathogenic.
• This pathogenicity is often associated with the lipopolysaccharide (LPS) layer of the Gram-negative cell envelope

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4
Q

diagnosing infection?

A

History (with differential diagnoses)
• Examination (review differential diagnoses)
• Investigations (radiology, biochemistry, immunology etc) review differential diagnoses even further
•Microbiology: Blood, stool, urine, wound, tissue cultures
•Microscopy: stool, urine, CSF, sputum •Serology
•Antigen detection
•PCR/ molecular studies

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5
Q

antibiotics that may be active against gram negatives

A
  • Beta lactams ( and monobactam )
  • Aminoglycosides
  • Macrolides
  • Tetracyclines
  • Chloramphenicol
  • Co-trimoxazole
  • polymixins
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6
Q

ciproflaxacins

A 
have been associated with seizures
ruptures of aortic aneurysm 
epilepsy 
achilles tendon rupture 
tendonitis
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7
Q

HAP vs CAP?

A

hospitalized > 48hrs

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8
Q

context in pneumonia?

A

Time of year/ season
• Type of immunosuppression (CD4 in HIV, chemotherapy, steroid dose changes, immunotherapy, chemotherapy)
• Chronic lung disease (bronchiectasis, Cystic fibrosis (CF), COPD etc)
• Epidemiological exposures (mycoplasma 4 yearly peaks, Coxiella,
psittacosis , PWID, vaccine status)
• Travel (resistant gram negs, MERS Co-V, MDR –TB, XDR- TB, Legionella)

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9
Q

aztreonams

A

purely active against gram negative

instead of gentamicin in a niche set of people

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10
Q

aminoglycosides

A

IV therapy
don’t have Myasthenia graves
narrow therapeutic window
workforce for gram negatives in tayside

not against anaerobes
- gentamicin

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11
Q

most gram negatives

A

gram negative bacili

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12
Q

H. influenza

A

gram negative coccobacillus

aerobic but can be facultative anaerobe

In vitro growth requires accessory growth factors, including “X” factor (hemin) and “V” factor (nicotinamide adenine dinucleotide [NAD]).

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13
Q

how does H. influenza react to chocolate agar media?

A

Chocolate agar media. (will generally not grow on blood agar, which lacks NAD /V factor/ nicotinamide adenine dinucleotide

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14
Q

antibiotic of choice for H. influenza?

A

amoxicillin - in the UK and also covers strep. pneumonia

doxycycline also active

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15
Q

atypical pneumonia is not

A

strep pneumonia

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16
Q

atypical pneumonia causes?

A

Mycoplasma pneumoniae , acute Coxiella burnetii , Chlamydophila psittaci, Legionella pneumophila

17
Q

treating atypical pneumonia?

A

Most respond to doxycycline (a tetracycline) – NOT so much Legionella
• Clarithromycin (a macrolide) also works
• Quinolones (levofloxacin) in penicillin allergic severe pneumonia. NOTE Cdiff risk)

18
Q

mortality of atypical pneumonia?

A

varies with pathogen, but generally lower than classical bacterial pneumonia

Legionella has a higher mortality. Look out for risk factors

19
Q

where do you get legionella?

A

Lukewarm aerosolised water ( showers, air conditioning , taps)
• More common in smokers, males, COPD, immunosuppressed, malignancy, diabetes, dialysis, hot tubs
• There is a milder disease caused by Legionella pneumophila called Pontiac disease
• In water,
• multiplies within amoebae and ciliated protozoa, which are small one-celled organisms.
• These provide nutrients and shelter from adverse environmental conditions, such as extreme temperatures and chemicals like chlorine.
• Human immune cells called alveolar macrophages look very similar to protozoa. Legionella invades and grows within alveolar macrophages, mistaking them for their natural host and causing disease

20
Q

what is the most common form of legionella?

A

serogroup 1 but not all

21
Q

important causes of gram negative sepsis?

A

Escherichia coli, Klebsiella, Pseudomonas, Serratia, Acinetobacter, Enterobacter (not to be confused with the gram positive Enterococcus), Citrobacter, and Neisseria meningitidis
• Neisseria meningitidis will be covered in the CNS
• Gram negs are also covered in GI infections and in Renal

22
Q

what treats pseudomonas

A

ciproflaxacin - the only oral drug which will treat pseudomonas

23
Q

what are coliforms?

A 
E. coli and similar organisms
• Gram negative rods
• Biochemical tests to differentiate
• Klebsiella sp., Proteus sp., Enterobacter sp.,
Serratia sp. etc.
24
Q

antibiotic resistance?

A

antibiotics are only able to kill certain strains of bacteria

bacteria with certain traits survive
these bacteria are now able to multiply and colonise

25
Q

mckonkey agar

A

when put on mckonkey agar turns pink with gram negative bacilli

26
Q

what antibiotics are used to treat extended spectrum beta lactamases?

A

penicillins, cephalosporins and aztreonam activity is lost

27
Q

perforated peritonitis

A

amoxicillin + gentamicin + metronidazole

28
Q

carbapenems

A

more broad spectrum than penicillin

29
Q

ESBL which countries have a high rate

A

Portugal, Italy and spain - have high rates of ESBL

30
Q

ESBL

A

Endemnicity varies ( geographically, patient population, increasing over time, pathogen)
• Often accompanied by resistance to other antibiotics
• Spread often plasmid mediated
• Confirmation of the presence of ESBLs takes time and effort and money

31
Q

toxicities in prescribing?

A 
Allergic reactions 
• Weight
• Renal function
• Hepatic function 
• Age
• Drug- drug interactions 
• Ascites/ burns
• Pregnancy
• Co-morbidities
• Drug profile
32
Q

gentamicin protocol

A 
concerns re-nephrotoxicity 
limit duration:
• 72 hours then ID/Micro approval required
• 24 hours if concern re renal function
• Monitor renal function daily
• Correct dosing for overweight patients
• Maximum dose of 600mg
• Clear exclusion criteria
• Use nomogram or dose when <1mg/L
• Prescribe in ‘once only’ section
• Let ward pharmacist know if starting gent • Levels done twice daily at NW
• Use the app
33
Q

major problem associated with gentamicin?

A

nephrotoxicity

Sepsis (8 decks)

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