Infectious diseases Flashcards
define colonisation
presence of a microbe in the human body without an inflammatory response
define infection
inflammation due to a microbe
define bacteraemia
presence of viable bacteria in the blood
define sepsis
life threatening organ dysfunction caused by a dysregulated host response to infection
define septic shock
sepsis AND (despite adequate fluid resuscitation + vasopressors) persistent hypotension AND lactate >=2
what is SIRS
NON-specific clinical response including >=2 of the following: temp >38 <36 HR >90 RR >20 WBC >12000
causes of SIRS
infection burns trauma pancreatitis and other insults
What is the term for SIRS with a presumed/confirmed infectious process
sepsis
list the organ dysfunction that can occur due to sepsis
renal CNS haematological - DIC CVS hepatic respiratory metabolic acidosis
what is the qSOFA score
screening for outcome rather than diagnosis (see slide) RR >22 sBP <100 Altered GCS
NEWS of ?, think sepsis
NEWS of >=5 with a known infection, think sepsis
RF for sepsis
age: <1yr or >75yr frail people recent trauma / invasive procedure immunocompromised - DM, hyposplenism, Coeliac - steroids, chemo, DMARDs, biologics Indwelling lines - catheters, cannulas PWID breach in skin integrity - burns, ulcers, wounds, infections pregnancy/puerperium, PPROM
What is the sepsis 6 bundle
Cultures: blood, sputum, urine, stool, wound Lactate Urine output Oxygen IV fluids IV antibiotics WITHIN 1 HOUR!!!
principles in fluid resuscitation in sepsis
250-500ml 0.9% saline/Hartmanns over 15 min
aim for MAP >65mmHg
aim for 30ml/kg over first 3 hours
if BP is unresponsive after fluid resuscitation, what should you do
consider transfer to HDU for vasopressors via CVC e.g. noradrenaline, vasopressin
what is a high lactate a sign of
ischaemia and hypoperfusion
minimal target for urine output in sepsis
0.5ml/kg/hour
signs of infection in someone with a NEWS >5
new onset confusion cough UTI - dysuria abdo pain abnormal bloods
skin colonisers/commensals
staphylococcus aureus, epidermidis
corynebacterium - diphtheroids
what are potential contaminants of cultures
staph epi
diphtheroids
what is a pathogen
any bug that has the potential to cause disease
Gram positive bacteria have a thick/thin peptidoglycan wall
thick
Gram negative bacteria have a thick/thin peptidoglycan wall and an additional __ layer
thin wall
additional lipopolysaccharide layer
what do the following severity scoring systems assess:
CURB65
Dukes
CURB65 - CAP
Dukes - IE
oral cavity colonisers
strep viridans group
vagina colonisers
enterobactereriaceae
lactobacillus
candida
staph aureus
large bowel colonisers
enterobactereriaceae - E.coli, klebsiella, enterobacter, proteus
enterococci - E.faecalis / faecium
what is IVOST
IV to oral switch
List B lactam antibiotics
penicillin flucloxacillin amoxicillin co-amoxiclav cephalosporins pipercillin / tazobactam carbepenems
what is the allergy causing part in some antibiotics
B lactam ring
Penicillin G is IV/PO?
penicillin G = IV = benzylpenicillin
Penicillin V is IV/PO?
penicillin V = PO = phenoxymethylpenicillin
which is more effective PO penicillin or amoxicillin
PO amoxicillin > penicillin
describe the haemolysis in the following for strep:
alpha
beta
gamma
alpha - partial / green tinge
beta - complete / golden
gamma - none
what is the antibiotic of choice for Gm + bacteria
- amoxicillin
2. vancomycin
what is VRE
vancomycin resistant enterococcus
antibiotic of choice for staph. Aureus
FLUCLOXACILLIN
antibiotic of choice for MRSA or penicillin allergy
vancomycin
RF for C. diff infection
elderly 4 Cs antibiotics PPIs prolonged hospital stay surgical procedure immunocompromised
4 Cs for C.diff
cephalosporins ciprofloxacin (and all quinolones) clindamycin co-amoxiclav NOT clarithromycin
what is used to assess severity of C.diff infection
severity assessment
management of non-severe c.diff infection
PO metronidazole
management of severe c.diff infection
PO vancomycin +- IV metronidazole
C.diff requires isolation?
yes
in a case of intra-abdominal sepsis, which antibiotics cover the following:
enterococci
anaerobes
gram negative coliforms
enterococci - amoxicillin
anaerobes - metronidazole
gram negative coliforms - gentamicin
side effects of quinolone antibiotics
tendon rupture lower seizure threshold c.diff infection psychosis aortic rupture
the pathogenicity of gram negative bacteria is associated with what
LPS layer of the outer membrane
antibiotics that may be active against Gm-
B lactams monobactam - aztreonam aminoglycosides - gentamicin macrolides tetracyclines chloramphenicol co-trimoxazole
aztreonam is only effective against Gm + or -
Gm -ves
RF for Gm - infection
HAP vs CAP ventilated vs not time of year immunosuppressed chronic lung disease travel epidemiological exposures
what is HiB
gram negative coccobacillus
examples of microbes causing atypical pneumonia and what is the management
legionella mycoplasma coxiella C. psittaci macrolides, tetracyclines, quinolones
RF for legionella
lukewarm aerosolised water smokers males COPD immunocompromised malignancy DM dialysis hot tubs
test for legionella (serotype 1)
urinary antigen
antibiotics for legionella
levofloxacin
what are coliforms
Gm - rods
which microbes cause Gm - sepsis
E.coli Klebsiella Pseudomonas Enterobacter N. meningitides
what are ESBLs
extended spectrum B lactamases
bacteria that are resistant to B lactam antibiotics i.e. resistant Gm -ves
side effects of gentamicin
otoxicity
nephrotoxicity
max duration of gentamicin therapy
72 hours
CVS dysfunction in sepsis
hypotension due to vasodilatation
distributive shock
pulmonary dysfunction in sepsis
ARDS
resp failure
renal dysfunction in sepsis
AKI
hepatic dysfunction in sepsis
transaminitis due to hypoperfusion
jaundice
CNS dysfunction in sepsis
delirium / acute confusional state
drowsy
altered GCS
what is lactic acidosis
diffuse tissue hypoxia and hypoperfusion leads to anaerobic metabolism and therefore lactic acid production –> met acidosis
haemtological dysfunction in sepsis
DIC = imbalance between clotting and bleeding from endothelial dysfunction
thrombocytopaenia, prolonged PTT/APTT, low fibrinogen, raised d dimers
allergy to 1 B lactam = allergy to all?
yes
examples of quinolones
ciprofloxacin
levofloxacin
oflaxacin
moxifloxacin
B lactams are bactericidal/bacteriostatic
bactericidal
side effects of tetracyclines
photosensitivity
teeth staining in kids
which antibiotic does NOT cover strep pneumoniae
ciprofloxacin
what does clindamycin cover
Gm + and anaerobes
what infections can listeria cause
meningitis in immunosuppressed
gastroenteritis
vancomycin works against Gm -, true or false
FALSE
only Gm +
which antibiotic should never be prescribed on its own
rifampicin
side effects of antibiotics in general
N+V
diarrhoea
rashes
candida
side effects of penicillins
hypersensitivity
skin reactions
what antibiotics can cause cholestatic jaundice
flucloxacillin
co-amoxiclav
side effects of macrolides
N+V
GI upset
hepatotoxicity
long QT
side effects of quinolones
long QT
lower seizure threshold
tendonitis and rupture
AAA
side effects of aminoglycosides
nephrotoxicity
ototoxicity
side effect of vancomycin
red man syndrome
side effects of tetracyclines
photosensitivity
hepatotoxicity
teeth staining
dysphagia
side effects of nitrofurantoin
peripheral neuropathy
pulmonary fibrosis
side effects of sulphonamides
SJS
haematological
side effect of trimethoprim
blood dyscrasias
side effects of chloramphenicol
aplastic anaemia
grey baby syndrome
aztreonam does not cause a penicillin associated allergy
true
how many blood cultures should you take for suspected IE
3
Criteria for IVOST
HOME Haemodynamically stable Oral route available Markers of inflammation improving Exclude deep seated infection
what is a SAB
Staph Aureus Bacteraemia
which antibiotics cover Gm+ bacteria?
Penicillins: flucloxacillin, amoxicillin, co-amoxiclav Vancomycin Cephalosporins Rifamipicin Fusidic acid Co-trimoxazole Clindamycin Carbepenems
which antibiotics cover anaerobic bacteria?
Metronidazole Clindamycin Vancomycin Co-trimoxazole Carbepenems
which antibiotics cover Gm- bacteria?
Gentamicin Co-trimoxazole Amoxicillin Carbepenems Quinolones
why is nitrofurantoin never used for pyelonephritis
only penetrates the bladder
not effective in the kidneys - poor tissue penetration
antibiotics for pyelonephritis
amoxicillin and gentamicin
how do you make a diagnosis of pneumonia
consolidation on a CXR
in someone with a UTI/pyelonephritis what else should you ask in the history
PV discharge / symptoms
recent STI
another differential you should consider in pyelonephritis
renal calculi
what are possible infectious causes of diffuse generalised abdominal pain in e.g. elderly patients
UTI
what strain of Staph A can cause multiple boils in the skin
PVL producing Staph
what toxin does E.coli 0157 release that causes HUS
shiga toxin
types of infections that PWID are at increased risk of
cellulitis - repetitive breach into the skin Infective endocarditis phlebitis / DVT abscess bacteraemia pseudoaneurysm from arterial puncture
what side of the heart are PWID more likely to get IE
right sided because of venous access
but technically can get vegetations at any part
what is required to have IE
bacteraemia
what bug specifically causes IE in prosthetic valves
staph epi
what is the most common bug cause of IE
staph aureus
causes of acute IE
staph A
strep viridans
MRSA
causes of subacute IE
enterococci
strep viridans
where are you most likely to get MRSA IE
repeated hospital admissions
what is the logic behind prescribing gentamicin for IE
it has a synergistic effect when given with amoxicillin / vancomycin, against strep
normally 7mg/kg but in IE, 1mg/kg
differential diagnoses of fevers, weight loss
subacute IE TB malignancy abscess osteomyelitis deep seated infection
investigations for TB swab
PCR - faster and more sensitive
acid fast bacilli - needs a large number of bacteria
treatment for TB
2 RIPE 4 RI rifampicin isoniazid pyrazinamide ethambutol
side effect of TB drugs
rifampicin - orange urine, hepatitis
isoniazid - peripheral neuropathy, hepatitis, P450 inhibitor
pyrazinamide - gout
ethambutol - loss of colour vision
N. meningitides is a commensal of ??
the throat in some people
causes of meningitis in adults
N. meningitides - younger HiB strep pneumoniae - older (NHS) enteroviruses HSV2
which virus commonly causes encephalitis
HSV1
imaging for encephalitis
CT - to rule out mass lesions…
MRI - better to look at brain parenchyma
why do you do a CT for some people with meningitis
what are the indications
to exclude risk of brain herniation in those with signs to carry out LP safely
- focal neurology
- low GCS <12
- seizures
- papilloedema
ICP will be raised in all causes of neuro infection?
true
when doing a LP, where will you send the sample?
microbiology - gram stain and culture, viral PCR
microscopy - white cells
biochemistry - glucose, protein
causes of liver abscesses
portal venous system - carrying blood from other areas in the abdomen which may have disease e.g. diverticular abscess, CRC
hepatobiliary - cholecystitis, cholangitis
haematogenous seeding
external - surgery, biopsy
in severe C.diff infection, why would you add IV met to PO vanc
IV metronidzaole in those with ileus to help vancomycin reach the gut better
indications for IVOST
exclude deep seated infection
safe oral route available with good choice of antibiotic
resolution of inflammation and improvement seen
in those with febrile neutropaenia, what is the most common bug
gram negatives e.g. pseudomonas
treat with pip/taz
rapid diagnostic test for C.diff
stool toxin
