wk 5- antimicrobial therapy Flashcards
primary pathogens
cause disease in individuals despite immune status
opportunistic pathogens
cause disease in individuals whose natural defences are compromised
infectivity
ability for pathogen to establish in a host
virulence
how harmful pathogens are once established in a host
incubation period
time between the invasion by the pathogen and appearance of clinical features of infection (signs and symptoms)
period of infectivity
time the patient is infectious to others
bodys normal flora and defence system
normal flora: bodys microorganisms living in particular areas of the body
defence: different processes and barriers in the body that prevent infection eg (cilia, skin, mucus, tears, macropahges)
different types of pathogens and how they cause disease
virus
bacteria
fungi
protozoa
helminths
signs and symptoms of local and systemic infections
local: (involves skin or single organ)
-red
-hot
-pain
-loss of function
-exudate
-delayed wound healing
systemic: (involves whole body)
-fever >37.5C normal tempt is 36-37C
-chills/sweats
-diaarhoea, vomiting, nauesea
-headache
-fatigue
-etc
stages of infection
- incubation stage: pathogen is replicating. no symptoms
- prodromal stage: host begins to feel unwell with nonspecific signs/symptoms, fever, muscle aches, headache, fatigue
- acute stage: microbes are destroying specific host cells and systems. more specific symptoms occur
- convalescent stage: bodys defence mechanism has confined microbes and healing of damaged tissue has begun. health returns to normal.
ways to diagnose an infection
- no single definitive test
combination of clinical signs and laboratory tests (WBC count, ESR, CRP, blood, urine, wound culture)
blood tests- WBC what 2 major classes does it include and what are the types of infection you can conclude from the test
2 major classes
1. granulocytes: engluf and digest.
-neutorphils, monocytes, basphils, eosinophils
- lymphocytes: recognition of microbes
types of infections from WBC count
1. leukocytosis: increase of WBC- most common acute bacterial infection
2. leukopenia: decrease of WBC- long infection
3. increase in eosinophil count- allergic reaction
ESR what does it do when theres an infection, with other populations and when is it used
Large increases during infection, inflammation and plasma cell dyscrasias
also increases with age, pregnancy and anaemia
useful for monitoring resposne over time to antibiotics, example lower ESR means theres a response to antibiotics
CRP
increase when theres inflammation/ infection
good for determining severity as it reflects disease activity and response to treatment as it rises and falls quickly as response
clinical questioning SITDOWNSIR
s- site
i- intensity
t- type
d- duration
o- onset
w- with other symptoms?
n- aggrevated by?
s- spread?
i- incidence
r- relieved by
what tests to use if you want to monitor treatment (antibiotics)
CPR
ESR
what tests to use if you want to assess if theres an infection and if its longstanding or acute
WBC count
what tests to use for systemically ill patients
culture blood, urine, mucus etc before administration of antibiotic
gram positive and negative
positive: retains only purple stain
neg: retains only red stain
tells us the difference in structure of cell wall
response to antibiotics varies with the type of bacteria
how long do wound cultures take
24-48hours
bacteria components
single celled organisms
unique cell wall
some have flagella (move)
some have fimbria (attachement to host tissue)
DNA
dont have membrane bound organelles
dont have nucleus
principles of antimicrobial treatment
- accurate diagnosis
- empirical treatment initially
- switch to narrow spectrum after culture/sensitivity testing
- cost effective
- shortest duration possible
- host characteristics
- adverse effects
- when to refer
goals of AMT
destroy/suppress growth of pathogen with selective toxicity so the normal host defences can control the ifnection
pharmocokinetic properties of antimicrobials
PK- concerned with the time course of antimicrobial concentration
T>MIC: time that the plasma concentration remains above the Minimum inhibitory concentration
pharmacodynamic properties of antimicrobials
PD- concerned with antimicrobial concentration and the antimicrobial effect
MIC: minimum inhibitory concentration of the antimicrobial
types of killing patterns of antimicrobial drugs
- concentration dependent (higher the peak blood level, the better the effect, suboptimal dosing can lead to resistance)
-ciprofloxacin - time dependent (T>MIC for atleast 60% of time to produce a good effect)
-penicillin, erythromycin
bactericidal and example
cause cell death and lysis
-penicllin
bacteriostatic
inhibit growth allowing hist defence system time to remove
targets of antimicrobial action
- cell wall synthesis inhibitors (bactericidal)
- disruption of membrane permeability (bactericidal/static)
- protein synthesis inhibitors (bctericidal)
- essential metabolite
synthesis inhibitiors (bacteriostatic)
unwanted effects of antimicrobial drugs
- superinfection: imbalance of pathogen/non pathogen gut flora which can cause a secondary infection by allowing oathogenic organisms to proliferate area
-antibiotic related colitis: inflammtion of wall of colon, dont use anti diarrhoeal medicines
-hypersensitivity reactions: preformed antibodies or immune cells with antigens
-drug resistance: not enough dosing to kill pathogen but for it to adapt
antimicrobial resistance
when pathogens no longer respond to medicine making the infection harder to treat
intrinsic v acquired resistance
intrinsic: organisms make up that specifies the resistance (eg cell wall)
acquired: organism mutates or acquires new DNA creating a resistance organism
mechanisms of antimicrobial resistance
- barrier to entry- change in cell wall/outer membrane composition
- efflux pump- antibiotic from inside bacteria to external environment
- formation of biofilm- protective membrane that prevents penetration
- enzyme inactiviation
- alteration of target sites
- increased synthesis of target
- target adapation
microbes commonly involved in antimicrobial resistance
preventing antimicrobial resistance
- correct selection, dose and time for use (misuse, mis prescribing) - AMR stewardship
- monitoring
- hand hygiene/PPE
- disinfecting/cleaning
- vaccination
