microbio unit 3

what are the 4 pillars of public health?

assessment, policy development, assurance, and research (throughout)

assessment: monitor health and diagnose/investigate

policy development: inform, educate, and empower peoples; mobilize community partnerships; develop policies and plans in support of health

assurance: enforce laws, link peoples to services, and evaluate effectiveness

research: strive towards new insights and innovative solutions

what is the epidemiology triangle?

the interaction between the agent, host, and environment

what is healthmap?

a 24/7 monitoring platform that compiles news reports, sources, and discussions to create a map of current infectious disease outbreaks

dr william farr

a london physician during the industrial revolution; developed the concept of surveillance

dr john snow

doctor in london; studied cholera and determined that it came from water

responsible for the removal of the water from the broad street well

epidemiology

the study of the distribution and determinants of health-related states or events in populations; the study of disease outbreaks

what is the goal of the epidemiologist?

to break at least one of the sides of the epidemiology triangle; breaking the connection between the environment, host, and agent

what are the two strains of ebola that we focus on in this course?

O. zairense and O. bundibugyoense

what does ebola infection cause?

hemorrhagic fever; vomiting, diarrhea, muscle pain, and weakness (with very nonspecific symptoms aside from the severe fever)

how is ebola typically treated?

with fluids; attempt to maintain blood pressure and use antivirals if available

what were the sociocultural ramifications of the 2014 ebola outbreak?

a reduction in healthcare services, loss in GDP (due to unemployment/shutdown of jobs/services), upheaval of familial structures with loss, and loss of education

what is the general timeline of the 2014-2015 EVD outbreak?

first case in dec 2013 (guinea) → cases spread to liberia, sierra leone, nigeria, and senegal by september 2014 → EVD spreads to the US, spain, and mali → liberia, guinea, sierra leone, mali, and the UK are all declared EVD free by the end of 2015

what were the scientific outcomes of the 2014 EVD outbreak?

6 new rapid diagnostic tools were developed (as opposed to traditional testing methods, which took 3 days), the VSV-EBOV ebola vaccine was proven effective, and more medical professionals were trained/deployed

what was significant about the two 2018 EVD outbreaks?

the first outbreak was contained rapidly; the second outbreak was an entirely different strain and occurred across the country (northeast, near to uganda)

ring vaccination

a method of treatment where you vaccinate the contacts of an infected persons, then vaccinate the second level of contacts as well

utilized in the first 2018 EVD outbreak

what were the types of barriers to EVD response?

1. cultural → burial traditions that result in greater harm

2. distrust → avoidance of treatment centers

3. fear → widespread migration that increases disease zone

4. stability/violence → political turmoil inhibits activities and increases risk of intervention

5. governmental cooperation → limited access/resources and increase in response times

what were the significant outcomes of the second-largest ebola outbreak?

increase in ring vaccination, approval of rVSV-ZEBOV vaccination (FDA approval), two useful antibody treatments (REN-EB3 & mAb114)

what are the challenges of the 2026 EVD outbreak?

limited health infrastructure, ongoing conflict (leading to security issues), violence against healthcare workers, frequent migration, fundamental mistrust of government officials

what are the consequences of the 2026 EVD outbreak?

increased hunger and malnourishment (which creates a positive feedback loop for infection), potential development of vaccines for new strain (still in phase 1)

miasma

the idea that illnesses were conferred through “bad air” and toxic vapors

what are physical methods of control?

temperature changes, radiation, and filtration

what are the chemical methods of control?

germicides and antibiotics

decontamination

removes or reduces microbial populations to render an object safe for handling

sterilization

the process by which ALL microbes (and endospores) are removed/killed

disinfection

the process by which microbial numbers are reduced—commonly used for food, surfaces, and external medical equipment

refrigeration

used for preserving food and samples; slows the growth of microbes

freezing (0°C)

used for storing and preserving food/samples; slows the growth of microbes

for which control methods is heat used?

sterilization or decontamination

autoclaving

the process by which an autoclave machine uses heat, steam, and pressure to sterilize media and equipmemt

kills endospores!

pasteurization

the heating of liquids (below boiling temp) to reduce microbial populations

boiling

the process by which a liquid is heated to its boiling point to eliminate most pathogenic microbes

does not kill endospores

radiation

the emission or transmission of energy in the form of waves or particles through space

ionizing radiation

high-energy radiation with the ability to knock electrons from atoms; gamma and x-ray radiation

non-ionizing radiation

lower-energy radiation that lacks the ability to “knock” electrons; ultraviolet rays

has the capacity to mutate DNA (due to the formation of thymine dimers)

how does non-ionizing radiation differ from ionizing radiation?

it cannot pass through packaging

it is often used in wastewater treatment

it cannot kill microbes

filtration

a physical control methods where microbes pass through microbe-capturing filters (ex: HEPA filter & Lifestraws)

microbiocidal

something that causes microbe death

microbiostatic

something that inhibits microbial growth

germicides

chemical compounds used for chemical control of microbes

disinfectants

germicides used to treat inanimate objects

antiseptics

germicides used to treat living tissue

what are the different types of disinfectants?

detergents

alcohols

aldehydes

phenols

halogens

peroxygens

ethylene oxide

what are the different types of antiseptics?

detergents

alcohols

diluted phenols

diluted halogens

diluted peroxygens

why are endospores difficult to kill?

they are dormant structures that can revert to vegetative state once favorable growth conditions are restored

what is an alternate way to eliminate endospores (other than autoclaving)?

sporicides or hydrogen peroxides

how are protozoans controlled?

through a variety of methods that change according to their life cycle

how are viruses controlled?

by using gluteraldehyde-based detergents for enveloped viruses & chlorine-based agents for naked viruses

which kind of microbes do antibiotics not work on?

parasites, fungi, and viruses

antivirals

drugs that treat infection but doesn’t necessarily cure it; commonly target replication steps in the viral cycle (microbiostatic)

antifungals

agents that typically target the fungal cell wall, plasma membranes, and nucleic acid synthesis

ergosterol

a common target of antifungal drugs; a steroid found in the fungal cell wall

why are antiprotozoan and antihelminthic drugs hard to develop?

because protozoans and eukaryotes and they both have complex life cycles

antimalarial drugs

quinine, chloroquine, and primaquine

antihelminthic drugs

praziquantel

antiprotozoan drugs

metronizadole

antibiotics that target cell wall synthesis

beta-lactams and glycopeptides; usually bactericidal

beta-lactam antimicrobials

penicillins, cephalosporins, and carbapenems; contains a four-sided beta-lactam ring that prevents PG cross-linking

glycopeptide drugs

vancomycin

vancomycin

no beta-lactam ring, disrupts PG synthesis, can be used against MRSA; most gram-negatives aren’t affected

can produce an extreme reaction known as “red man syndrome”

antibiotics that target cell membranes

lipopeptides and polypeptides antibiotics

daptomycin

targets the cytoplasmic membrane; causes the loss of ions and lysis

cannot penetrate gram-negative bacteria

polymyxin and colistin

targets the outer membrane; interacts with the LPS

only effective against gram-negative bacteria

antibiotics that target nucleic acids

quinolones; usually bactericidal

quinolones

ciprofloxacin and levofloxacin

both target DNA replication enzymes

antibiotics that target metabolic pathways

sulfa drugs (sulfonamides) and trimethoprim

sulfonamides

competitve inhibitors of folic acid production because they resemble PABA (a natural building block for folic acid)

trimethoprim

an antibiotic that targets folic acid synthesis; used synergistically with sulfonamides

antibiotics that target ribosomes

macrolides, aminoglycosides, and tetracyclines (all generally bacteriostatic)

transpeptidase

an enzyme that catalyzes the transfer of amino acid residues or peptide bonds, especially during bacterial cell wall synthesis

what are the 3 mechanisms by which AMR occurs?

1. alteration of drug target

   1. bacterial target mutates and drug is no longer effective (ex, PBP → PBP2a)

2. drug inactivation

   1. acquisition of new genes that inactivate drug (ex. B-lactamases)

3. reduction in drug concentrations inside cell

   1. development of efflux pumps or mutation of porins (to prevent drug entry)

what is HGT?

horizontal gene transfer

what are the 3 ways that HGT occurs in bacteria?

1. transformation

   1. taking up new DNA from environment

2. transduction

   1. genes transported by bacteriophages

3. conjugation

   1. sharing DNA through physical connection

which human behaviours have contributed to a rise in AMR?

1. unregulated antibiotic use in developing countries

2. noncompliance with dosing and prescriptions

3. development of healthcare settings (which are perfect places for microbes to thrive)

4. antimicrobials in animal feed

5. ingestion of meat contaminated with resistant microbes

6. introduction of manure-contamianted water and manure-based fertilizers into food chain

how can humans respond to AMR?

1. personal methods

   1. infection prevention and prescription compliance

2. healthcare methods

   1. monitoring resistant infections

   2. appropriate antibiotic use

3. agricultural methods

   1. responsible antibiotic use

   2. responsible waste management

4. science/research

   1. support of basic research

   2. support of drug development and drug trials

what are the 6 urgent drug-resistant bacterial threats to health?

1. hospital-onset CRE

2. hospital-onset Carbapenem-resistant Actinobacter

3. clinical cases of C. auris

4. hospital-onset MRSA

5. hospital-onset VRE

6. hospital-onset ESBL-producing Enterobacterales

7. hospital-onset MDR Pseudomonas aeruginosa

how does AMR spread?

through random genetic mutation OR the acquisition of new genes (HGT)

neglected tropical diseases

dengue (vector and microbe)

chagas disease (vector and microbe)

leishmaniases (vector and microbe)

lymphatic filariasis (vector and microbe)

what is the global impact of dengue?

why has dengue spread so much?

because of climate change

why do NTDs persist?

lack of access to clean water, inadequate sanitation, close proximity to vectors, limited healthcare

is it possible to eliminate chagas disease? why?

no, because there are greater than 100 species of triatomine bug that carry T. cruzi

what cell type is attacked in leishmaniases?

visceral macrophages

what are the 3 forms of leishmaniases?

visceral, cutaneous, and mucocutaneous

how does lymphatic filariasis cause disfigurement?

since the adult worms invade the lymphatic system, their reproduction leads to impairment of the drainage system and the accumulation of fluid

what did END7 hope to accomplish?

it sought to raise awareness and funds to eliminate 7 NTDs by 2020

what are the diseases in END7?

LF, trachoma, onchocerciasis, soil-transmitted helminthiases, schistosomiasis

who are at the highest risk for NTDs?

women and children

what is significant about dengue infection?

if you are infected by one serotype, you’ll have lifelong immunity. if you are then infected with a different serotype, then the resulting disease will be more severe

how does Aedes albopictus compare to Aedes aegypti?

albopictus are common in asia and can survive in colder temperatures; their eggs are often resistant to environmental conditions

what does dengue cause?

dengue hemorrhagic fever

what is significant about the dengue vaccine?

the tetravalent vaccine was effective about all 4 serotypes, but increased the risk of DHF in sero-negative people (which incr’d anti-vacc sentiment)

what are the two stages of chagas disease?

acute stage (fever, malaise, facial edema, may resolve spontaneously) and chronic stage (asymptomatic—transmittable—and symptomatic stage)

visceral leishmaniasis

most severe form; infects internal organs (often causing enlarged spleen/liver)

cutaneous leishmaniasis

most common form; infects macrophages that reside in the skin, causing skin lesions

mucocutaneous leishmaniasis

occurs when cutaneous leishmaniasis goes untreated; infected macrophages migrate to mucous membranes and cause disfigurement

what are the risk factors for leishmaniasis?

malnutrition, poor living conditions, climate change