Microbiology - treatment and prevention of infection Flashcards
Apply the terms inherent resistance and acquired resistance appropriately
Explain how human activities may lead to antimicrobial resistance
Describe cellular mechanisms of antibacterial resistance
Identify medically important drug resistant bacteria
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describe acquired resistance
spontaneous mutation
you give antibiotic - kill off the non resistant
leaves just the resistant
they clone and this leads to replacement of a sensitive population by a resistant one
describe acquired resistance
- Mutation and clonal expansion:
spontaneous mutation
you give antibiotic - kill off the non resistant
leaves just the resistant
they clone and this leads to replacement of a sensitive population by a resistant one
- Transferable resistancee.g: A plasmid carries a gene conferring resistance to a new host
- faster means than spontaneous mutation
Describe cellular mechanisms of antibacterial resistance
Altered target site for the antimicrobial
Enzymatic degradation of antimicrobial agents (for example by a beta-lactamase enzyme) - they can produce enzymes
Alteration of the uptake or output of antimicrobial agents - can reduce amount of antibiotic they take in and increase the amount of antibiotic they spew out
What’s a Beta-lactamase
An enzyme which hydrolyses, breaks apart, the beta-lactam ring
An enzyme made by a bacteria to protect itself against a beta-lactam antibiotic
One of the most important antibiotic resistance mechanisms
name some resistant bacteria
see antibiotic and resistance lecture slide 21
describe the mechanism of resistance seen in Methicillin Resistant Staphylococcus Aureus (MRSA)
Methicillin Resistant Staphylococcus Aureus (MRSA)- altered target site
Mec A gene mutation:
altered PBP in Staphylococcus:
Beta- lactams fail to bind:
MRSA phenotype
describe the mechanism of resistance seen in Gylcopeptide Resistant Enterococcus (GRE)
Gylcopeptide Resistant Enterococcus (GRE)- altered target site
- Glycopeptides (vancomycin and teicoplanin) bind to Peptidoglycan precursor molecules and prevent their incorporation into the cell wall
- Altered precursor molecules (usually a single amino acid alteration in a pentapeptide) prevent glycopeptide binding
- Can be endemic is healthcare environments (characteristically ICU, Surgery (urology), Oncology settings)
describe the mechanism of resistance seen in Carbapenemase Producing Enterobacteriaceae (CPE)
Carbapenemase Producing Enterobacteriaceae (CPE)- enzymatic degradation
Enterobacteriaceae e.g. E. Coli or Klebsiella
Carbapenems e.g. meropenem or ertapenem
Carbapenemase: an Enzyme made by an Enterobacteriaceae that destroys these antibiotics
describe the mechanism of resistance seen in Pseudomonas aeruginosa
Pseudomonas aeruginosa- multiple mechanisms
Intrinsic resistance, but also able to Acquire further resistance
Highly adaptable: can grow in distilled H2O
Multiple mechanisms mainly altered uptake/ output; but also enzymatic degradation etc.
describe the mechanism of resistance seen in Multi-Drug Resistant Tuberculosis (MDR- TB)
Multi-Drug Resistant Tuberculosis (MDR- TB)- Intrinsic and acquired through mutation
Intrinsic resistance due in part to its lipid cell wall
rapidly develops resistance on treatment∴ Standard treatment involves combination therapy with four drugs
Slow growing organism ∴ long course needed: 6 months - when we kill bacteria we usually do it when they’ve just replicate - since these are slow growing it takes longer to kill them
name some cases that increase the likelihood of a patient developing antibiotic resistance
Exposure to healthcare, particularly intensive acute care settings
- chronic conditions
Exposure to antibiotics
- chronic infective conditions eg CF, urinary tract abnormalities, DM
Bio-Prosthetic materials - eg catheters
describe how resistant bacteria may spread between patients
Respiratory infections spread by respiratory symptoms
Gastrointestinal bacteria are spread by GI symptoms
- particularly
- diarrhoea
particularly incontinence
Devices hold bacteria (devices get colonised)
- devices need to be manipulated and handled
- hands carry bacteria
what measures are available to prevent infection
Isolate the infected, routine hand hygiene, aseptic technique, PPE
define universal precautions
an approach to infection control to treat all human blood and certain human body fluids as if they were known to be infectious for HIV, HBV and other bloodborne pathogens (US department of labor)
do the same thing and the right thing every single Tim you see a patient
describe the different levels of isolation for patients with multi-drug resistant (MDR) organisms, infective diarrhoea illness, measles/chicken pox, open pulmonary TB (MDR), ebola/viral haemorrhage fevers
Ebola/ Viral haemorrhagic fevers:
High level isolation unit - only 2 in the whole uk - v High level
Open pulmonary TB (MDR) and Measles/ Chicken pox:
‘source isolation’- single room, with lobby, at negative pressure to the corridor
Infective diarrhoeal illness:
Single room with en-suite toilet
Multi-Drug Resistant (MDR) organisms:
- Single room (with/ without ensuite)
- May also be nursed in ‘open’ wards using universal precautions
describe what is meant buy negative pressure and positive pressure in terms of ventilated patient rooms
Airborne infections such as TB, Chicken Pox, Measles
Negative pressure:
- a pressure gradient which moves air away from the ward corridor towards the patient (ie the air pressure in the room is less than that of the corridor)
- We call this ‘Source’ isolation
- Prevent transmission of airborne infections FROM the patient
- the patient being isolated is the Source of the problem
Positive pressure:
- a pressure gradient which moves air away from the patient towards the ward corridor
- We call this ‘protective’ isolation
- prevent transmission of infection TO the patient
- the patient being isolated needs to be Protected from others
name the three chemical methods of disinfection
Alcohol- >70% isopropyl alcohol by volume
- skin and equipment
Chlorhexidine 2% (a cell membrane active biocide)
- skin
Chlorine releasing agents (bleach)
- Environment and equipment
- Another Halogen- Iodine is used with alcohol for skin decontamination
describe the use of automated washer-disinfectors
- Main method for thermally or pressure sensitive equipment (e.g. endoscopes)
- Before sterilisation for surgical instruments
- Controlled engineered and monitored process
- Cleaning with detergent (washing)
- Followed by Thermal Disinfection (e.g >900C for a minute)
define autoclave
Autoclave: a high vacuum, high temperature, porous load steam steriliser
