Gram -ves

Question 1

how do gram -ves differ in structure of cell envelope?

Answer 1

contains an outer membrane composed by phospholipids and lipopolysaccharides which face the external environments
cell wall is thinner

Question 2

what is the driver of sepsis in gram -ves?

Answer 2

highly charges nature of lipopolysaccharides

Question 3

general rule for ciprofloxacin?

Answer 3

generally not used due to risk of C. Diff unless very specifically indicated
only common use is in legionella in combination with amoxicillin

Question 4

what classes of drugs are active against gram -ves?

Answer 4

beta lactams (and monobactam - used instead of gentamicin in a specific niche of people)
aminoglycosides (gentamicin)
macrolides
tetracyclines
chloramphenicol
co-trimoxazole
polymixins

Question 5

gentamicin is not active against what bacteria?

Answer 5

anaerobes

barely effective against gram +ves

Question 6

how does gram stain relate to shape?

Answer 6

gram +ve = generally cocci

gram -ve = generally bacilli

Question 7

pseudomonas?

Answer 7

CF

burns

Question 8

haemophilus?

Answer 8

lung

Question 9

E. Coli?

Answer 9

GI tract

urinary

Question 10

how long must the patient have been in hospital for a pneumonia to be classed as hospital acquired?

Answer 10

48 hrs

Question 11

classic risk factors for gram -ves?

Answer 11

immunosuppression
chronic lung disease
travel

Question 12

describe haemophilus?

Answer 12

gram -ve coccobacillus
generally aerobic but can grow as an anaerobe
grows on chocolate agar
sensitive to amoxicillin and doxycycline

Question 13

management of atypical pneumonia?

Answer 13

doxycycline
clarithromycin reserved for few cases
quinolones rarely used (except in legionella)

Question 14

risk factors for legionella?

Answer 14

lukewarm aerosolised water (showers, air conditioning)
male
smokers
COPD 
immunosuppressed
malignancy
diabetes
dialysis
hot tubs

Question 15

how does legionella grow in water and in the body?

Answer 15

water = multiplies within amoebae and ciliated protozoa
body = human immune cells called alveolar macrophages look similar to protozoa. legionella invades and grows within alveolar macrophages mistaking them for their natural host and causing disease

Question 16

which group of legionella causes most disease and how is it cultured?

Answer 16

serogroup 1
culture used in conjunction with serology
bronchoalveolar lavage may be required
selective media used (e.g buffered charcoal yeast extract)

Question 17

important causes of gram -ve sepsis?

Answer 17

E. Coli
pseudomonas
Neisseria meningitis
klebsiella
enterobacter

Question 18

what is the only treatment for pseudomonas?

Answer 18

ciprofloxacin

Question 19

what antigens in e. coli 0157?

Answer 19

O antigen

H antigen

Question 20

how does lactose fermenting gram -ve bacteria affect mconkey agar?

Answer 20

turns it pink

Question 21

what are coliforms? give examples

Answer 21

gram -ve rods
e. coli
klebsiella
proteus
enterobacter
serratia

Question 22

what does beta lactamase do?

Answer 22

opens up the beta lactam ring, inactivating the antibiotic

“key doesn’t fit the lock anymore”

Question 23

what antibiotics are extended spectrum Beta lactamases (ESBLs) resistant to?

Answer 23

penicillins
cephlasporins
aztreonam

Question 24

main risk with gentamicin?

Answer 24

nephrotoxicity

Question 25

what is Pontiac disease?

Answer 25

milder disease caused by legionella pneumophila