HAI Flashcards
what is a reservoir?
reservoir of an infectious agent is the habitat in which the agent normally grows, and multiplies. e.g. humans, animals and the environment
give some examples of diseases without intermediaries
STDs, measles, mumps and streptococcal infection
why was smallpox eradicated after the last human case was identified and isolated?
humans were the only reservoir for the smallpox virus
what is meant by a carrier when referring to a human?
someone who is with inapparent infection but is capable of transmitting the pathogen to others
what is the difference between a carrier and a vector?
a carrier is infected even if they are asymptomatic, whereas a vector is not infected with the disease even if they have it on them
what are the three different types of carriers?
incubatory: those who can transmit the agent during the incubation period and before clinical illness begins
convalescent: those who recovered from illness but remain capable of transmitting to others
chronic: those who continue to harbour causative agent for weeks and months after initial infection
what is meant by zoonosis?
infectious disease that is transmissible under natural conditions from vertebrae animals to humans
give five ways in which a pathogen can leave a host
respiratory tract
urine
feces
crossing placenta from mother to foetus
cuts or needles in skin
describe the three modes of indirect transmission
airborne transmission: occurs when infectious agents are carried by dust or droplet nuclei suspended in air
vehicles: food, water, blood and fomites (inanimate objects)
vectors: mosquitoes, fleas and ticks may carry infectious agents through purely mechanical means
give 3 examples of non-specific factors that defend against infection
skin, mucous membrane, gastric acidity
how could vehicleborne transmissions be reduced?
elimination or decontamination of vehicle
how could airborne transmissions be reduced?
mofifying ventilation, or air pressure
filtering or treating the air
how could vectorborne transmission be reduced?
controlling vector population, such as spraying to reduce mosquito population
give 2 examples of interventions that aim to increase a host’s defence
vaccinations promote development of specific antibodies that protect against infection
prophylactic use of antimalarial drugs, prevents infection from taking root
what kind of intervention might prevent a pathogen from encountering a susceptible host?
herd immunity: suggests that if high enough proportion of individuals in a population are resistant to an agent, then those few who are susceptible will be protected by resistant majority, since pathogens will be unlikely to find the few susceptible individuals.
what is the definition of a hospital acquired infection?
an infection that patients get while receiving tratment for medical or surgical conditions
where might HAIs become more of a problem in outpatient settings??
often have limited capacity for infection control as compared to acute care setting?
what are the 4 main risk factors of HAI?
medical procedures and antibiotic uses
organisational factors
patient characteristics
behaviour of healthcare staff
list some ways in which HAIs can be prevented
increased compliance with and adoption of best practices of healthcare workers
careful insertion, maintenance and prompt removal or catheters
advance development of effective prevention tools
explore new prevention approaches
what is a bacterial cell wall made of?
lipid bilayer membrane
peptidoglycan (murein) matrix
what are the differences in cell walls between gram negative and gram positive bacteria?
gram positive: build thick peptidoglycan sheath around a single membrane
gram negative: build thin layer of peptidoglycan between two lipopolysaccharide membranes
what colour is gram negative/positive bacteria?
-ve: red/pink
+ve: purple
if someone has an infection, what are their WBC count, CRP level and respiratory rate?
high WBC count
high CRP level
high respiratory rate
what are the components of a single molecule of peptidoglycan?
2 sugars
short chain of amino acids
peptide bridge
how is the peptidoglycan matrix formed?
peptidoglycan production prevented by penicillin so cell bursts due to osmotic pressure
what is D-alanyl-D-alanine carboxypeptidase transpeptidase also known as and what is its function?
penicillin binding protein
assists with peptidoglycan matrix assembling by creating crosslinks between chains
describe the mechanism by which penicillin prevents peptidoglycan production
penicillin’s beta-lactam ring binds to key serine on the penicillin-binding protein’s active site. this inactivates enzyme and prevents formation of peptidoglycan matrix
how does altered target site antibiotic resistance work?
acquisition of alternative gene or a gene that encodes a target-modifying enzyme
alters structural conformation of protein that antibiotic targets
how does MRSA (strain of S. aureus) evade beta-lactam containing antibiotics?
expresses penicillin-binding protein 2a with an altered active site that does not bind to the beta-lactam ring in these antibiotics
explain how antibiotics can be inactivated?
enzyme degradation or alteration rendering antibiotic ineffective
inactivation can also be enzyme independent
how else can bacteria evade beta-lactam-containing antibiotics?
they can express a beta-lactamase enzyme which breaks beta-lactam of antibiotic, rendering the antibiotic useless
what is the name of a gene that is crucial in producing beta-lactamase enzyme and what does the enzyme do?
NSM-1: production of New-Delhi metallo-beta-lactamase enzyme
This enzyme type can break down almost all known beta-lactamase drugs
what is a beta-lactamase inhibitor?
medication used to inhibit the activity of beta-lactam antibiotics (with beta-lactamase) inhibitor
giving an example, how can antibiotics overcome bacteria that produce beta-lactamase?
ampicillin and clavulanic acid: have beta-lactamase inhibitors, allowing antibiotic to inhibit penicillin-binding protein freely
what is co-amoxiclav?
antibiotic consisting of both amoxicillin and clavulanic acid
what is meant by horizontal gene transfer?
process in which organism transfers genetic material (plasmids) to another organism that isn’t offspring
what is meant by vertical gene transfer?
transfer of genetic information including any genetic mutations from a parent to its offspring
how can antibiotic resistance within one population of bacteria spread to another population?
horizontal gene transfer from species with resistance to species without resistance
this involves transfer of plasmids
vertical gene transfer of plasmids from one generation in species that previously did not have resistance, to the next generation
when does antibiotic resistance occur?
when germs like fungi and bacteria develop the ability to defeat the drugs designed to kill them. germs aren’t killed and continue to grow
what are antimicrobials?
drugs used to treat infections and disease caused by microbes
what are the 2 types of microbes?
bacteria (treated with antibiotics) and fungal (treated with antifungals)
where do you typically find antibiotic resistant DNA in bacteria?
Plasmids (small pieces of DNA that carry genetic instructions from one germ to another)
what gram of bacteria have an outer layer that protects from their antibiotic drugs?
gram negative
how do germs get rid of antibiotics?
use pumps in their cell walls to remove antibiotic drugs that enter the cell
e.g. some psudomonas aeruginose bacteria can produce pumps to get rid of several different important antibiotic drugs, including fluoroquinolones, beta-lactams, chloramphenicol, and trimethoprim
what other resistance mechanisms can bacteria use?
change or destroy antibiotics using an enzyme
bypass the effects of the antibiotic- develop new cell processes that avoid using the antibiotic’s target
change the targets for the antibiotic- germs change the antibiotic’s target so the drug can no longer fit and do it’s job
what is sepsis?
body’s extreme response to an infection which can rapidly lead to tissue damage, organ failure and death
what is meant by a shock?
imbalance in supply and demand
what is the sequence of septic shock?
hypertension (high BP) > tachycardia (high heart rate) > tachypnoea (high respiratory rate)
how are antibodies administered during sepsis?
intravenously because they have a faster delivery than oral antibiotics
what form of penicillin is suitable for oral use?
penicillin V
how can an altered metabolism profile lead to antibiotic evasion?
increased production of enzyme substrate can out compete antibiotic inhibitor or the bacteria can just switch to another metabolic pathway
what 2 HAIs did the HAI objectives for Healthy People 2020 address?
CLABSI (Central Line Associated BloodStream Infections): when germs enter the bloodstream through the central line
MRSA: causes life threatening bloodstream infections, pneumonia and surgical site infections
