chapter 19-24 Flashcards
(129 cards)
1
Q
Epidemiology
A
study of epidemics: distributions, causes of diseases in a population
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Q
communicable (contagious) diseases
A
transmitted from one host to another; transmission determined by interactions between environment, pathogen, and host, controlling any of these can break the cycle of infection. Examples: measles, colds, flu
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non communicable diseases (not contagious)
A
Do not spread from host to host. examples CVD, cancer, COPD
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Epidemiologists
A
are more concerned with rate rather than with absolute number of cases. (how fast the epidemic/disease is spreading)
5
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principles of epidemiology
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- attack rate-the percent of people who become ill after exposure to an infectious agent
- incidence: the number of new cases in a specific time period in a specific pop
- prevalence: total number of cases at any time or for a specific period in a given population.
- morbidity: incidence of disease rate in a defined population
- mortality: overall death rate in a population
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principles of epidemiology
last 5 of 11
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- case-fatality rate: percentage of population that dies from a specific disease.
- endemic diseases: constantly present in a population (eg. the common cold)
- sporadic: few cases from time to time
- epidemic: unusually large number of cases
- outbreak: group of cases at a brief period of time and affecting a specific population, may signal the onset of an epidemic
- pandemic: when epidemic spreads world-wide
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Q
Attack rate
A
the percentage of people who become ill in a population after exposure to an infectious agent
8
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incidence
A
the number of new cases in a specific time period in a specific population
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prevalence
A
total number of cases at any time or for a specific period in a given population
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morbidity
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incidence of disease rate in a defined population
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mortality
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overall death rate in a population
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case- fatality rate
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percentage of population that dies from a specific disease
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endemic disease
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constantly present in a population (eg common cold)
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sporadic
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few a cases from time to time
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epidemic
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unusually large number of cases
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outbreak
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group of cases at a brief period of time and affecting a specific population, may signal that onset of an epidemic
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pandemic
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when epidemic spreads world-wide
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chain of infection
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- reservoirs (hosts where pathogen live examples: animal, human, environment)
- disease transmission(how disease is spread)
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where pathogens live
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Animal, human or environment- identification is important in disease control( eg control of rats, mice and prairie dogs prevents plague epidemics in the us caused by Yersina pestis)
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human reservoirs (host)
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- symptomatic infections: obvious, relatively “ easier” to control
- asymptomatic carries: more problematic (eg up to 60% women are asymptomatic when infected with Neisseria gonorrhoeae)
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symptomatic infections
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obvious, relatively “ easier” to control
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asymptomatic carries
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more problematic (eg up to 60% women are asymptomatic when infected with Neisseria gonorrhoeae)
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non human reservoirs
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animal: poultry (salmonella and campylobacter) raccoons, skunks and bats (rabies virus)
environment reservoirs: difficult to control, eg soil (C. botulinum and C. tetani)
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portals of entry
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where microbes gain access into the host: mouth nose eyes ears reproductive tract urinary tract open wound
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portals of exit
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where microbes is shed from
mouth
nose
anus
semen
reproductive tract
urinary tract
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disease transmission
1. vertical transmission: from woman to fetus, or mother to infant during childbirth or breast feeding
2. horizontal transmission: all other types of transfer; person to person via air, physical contact, ingestion of food or water, vector, can be direct or indirect
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vertical transmission
from woman to fetus, or mother to infant during childbirth or breast feeding
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horizontal transmission
all other types of transfer; person to person via air, physical contact, ingestion of food or water, vector, can be direct or indirect
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direct transmission
1. direct contact: touching, ingestion (fecal-oral transmission)
2. droplet transmission: major concern in densely populated buildings, such as schools, day care facility or military barracks.
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direct contact
touching, ingestion (fecal-oral transmission) -- (form of direct transmission)
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droplet transmission
major concern in densely populated buildings, such as schools, day care facility or military barracks---( from of direct transmission)
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indirect transmission
1. airborne
2. vehicle-borne- via fomites (inanimate objects), food (cross-contamination), and water
3. vector-borne: flies carry E.coli 0157:H7 or Shigella species, arthropods (misquitos, ticks) carry pathogens that cause lyme disease, plague, and malaria
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vector-borne diseases
flies carry E.coli 0157:H7 or Shigella species, arthropods (misquitos, ticks) carry pathogens that cause lyme disease, plague, and malaria
(form of indirect transmission)
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vehicle-borne diseases
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via fomites (inanimate objects), food (cross-contamination), and water
(form of indirect transmission)
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factors that influence the epidemiology of disease
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1. characteristics of the pathogen:
virulence
dose
incubation time
2. characteristics of the host
immunity to the pathogen
general health of the population
age
gender
behavioral practices
genetic backgrounds
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the Virulence of a pathogen influences the epidemiology of disease:
those that have more virulence (extreme severe or harmful) factors spread more extensively
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dose of a pathogen influences the epidemiology of disease
dose: minimum number of pathogens required (requiring needing Higher numbers of pathogens are harder to spread. or lower number needing fewer numbers of pathogens are easier to spread)
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incubation period of a pathogen influences the epidemiology of a disease
incubation period: those with long incubation period will allow extensive spreading (takes longer for symptoms and signs to appear, takes longer to Dx for treatment)
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Immunity of a host influences the epidemiology of a disease
the importance of vaccination and herd immunity (the more people that are vacinized the more people are immune to the specific pathogen) examples MMR, polio, any vaccine that has been around for a long time, if people don't get vaccinated disease can spread causing for an epidemic or outbreak that could lead to death in people with a compromised immune system or unvaccinated person)
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general health of host population can influence the epidemiology of a disease
malnutrition, overcrowding, and fatigue increases probability of spreading.
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age of the host can influence the epidemiology of a disease
the elderly and the very young are more susceptible to infections
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gender of the host can influence the epidemiology of a disease
women are more likely to develop UTI due to having shorter urethra
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behavioral practices of the host can influence the epidemiology of a disease
infants that are breastfed vs infants who are not breastfed, consumption of raw fish in certain cultures increases the probability of contracting fish tapeworms
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genetic background of the host can influence the epidemiology of a disease
natural immunities vary, and specific receptors may differ (many African descents are not as susceptible to malaria, some populations of northern European are less susceptible to HIV infection)
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infectious disease surveillance
1. national surveillance network: CDC center of disease control and prevention Atlanta GA:
morbidity and mortality weekly report (MMWR) summarizes the status of a number of diseases
notifiable disease: high in incidence of pose potential danger to the public health
2. national surveillance network: public health departments: public health departments in each state have authority, to mandate diseases that must be reported. other components of public health network: absentee rates in public schools, hospital laboratories, news media.
3. Worldwide surveillance: WHO (world health organization) provides education and technical assistance: world wide guidance in the health field, set global standards for health, strengthen national health programs, develop and transferred appropriate technology. periodical and publications eg weekly epidemiological record
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national surveillance network: CDC center of disease control and prevention Atlanta GA
morbidity and mortality weekly report (MMWR) summarizes the status of a number of diseases
notifiable disease: high in incidence of pose potential danger to the public health
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national surveillance network: public health departments:
public health departments in each state have authority, to mandate diseases that must be reported. other components of public health network: absentee rates in public schools, hospital laboratories, news media
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Worldwide surveillance: WHO (world health organization)
provides education and technical assistance: world wide guidance in the health field, set global standards for health, strengthen national health programs, develop and transferred appropriate technology. periodical and publications eg weekly epidemiological record
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contributing factors to emergence of infectious disease
1. microbial evolution: vibro cholera 0139 gained antibiotic resistance and ability to produce capsule
2. complacency and public health efforts: successes can divert attention and public funding to eradicate the disease
3. changes in human society: day care centers allow easy transfer of pathogens
4. Advances in technology : the use of contact lenses
5. population expansion: people move to areas close to reservoirs.
6. development: increasing number of dams extends the range of schistosomiasis
7. mass production and widespread distribution of food
8. war and civil unrest: refugee camps poor sanitation, disrupts disease eradication efforts.
9. climate change: warm temp and arthropods, heavy flooding from el nino
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Microbial evolution is a contributing factor to emergence of infectious disease
vibro cholera 0139 gained antibiotic resistance and ability to produce capsule
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complacency and public health efforts is a contributing factor to emergence of infectious disease
successes can divert attention and public funding to eradicate the disease
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changes in human society is a contributing factor to emergence of infectious disease
day care centers allow easy transfer of pathogens
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advances in technology is a contributing factor to emergence of infectious disease
the use of contact lenses
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population expansion is a contributing factor to emergence of infectious disease
is a contributing factor to emergence of infectious disease
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development is a contributing factor to emergence of infectious disease
increasing number of dams extends the range of schistosomiasis
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mass production and widespread distribution of food is a contributing factor to emergence of infectious disease
becuase of different food pathogens from other countries as well as unsanitary conditions for stock animals
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war and civil unrest is a contributing factor to emergence of infectious disease
refugee camps poor sanitation, disrupts disease eradication efforts.
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climate change is a contributing factor to emergence of infectious disease
warm temp and arthropods, heavy flooding from el nino
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healthcare associated infections or HAIs
| defintion
infections that acquired while receiving treatment in healthcare setting, nosocomial infections or hospital acquired infections
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healthcare associated infections or HAIs
| reservoirs of infectious agent:
1. other pt
2. healthcare environment (pseudomonas aeruginosa)
3. healthcare workers sick with asymptomatic carriers (staphylococcus aureus and streptococcus pyogenes on the skin)
4. pt microbiota: any invasive procedures where staphylococcus epidermidis gains acess to bloodstream via IV fluids)
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healthcare associated infections or HAIs
| transmission of infectious agents
1. direct transmission; healthcare worker touch multiple pt
2. indirect transmission: via medical device that breach the first line barriers (uti from contaminated cath, mechanical respirator)
3. airborne transmission: reduced by arrangement of air flow careful mopping and HEPA filter (high effeiency particulate are)
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Gerhard Domagk 1932
red dye protonsil to treat streptococcal infections
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first documented case
salvarsan (paul erlich 1910)
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penicillin (alexander fleming)
staphlyococcus
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(WWII) penicillin G
antibiotic (antimicrobials naturally produced by microorganisms)
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most antibiotics come from
Streptomyces and bacillus (bacteria) and penicillum and cephalospporium (fungi)
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therapeutic index
lowest dose toxic to patient divided by dose used for therapy
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bacteriostatic
inhibits bacterial growth, relies on pt immune system to eliminate bacteria
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bactericidal
kills bacteria, sometimes only inhibitory
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antimicrobial selective toxicity
must cause greater harm to microbes than to pt
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broad spectrum
affect a wide range, life threatening illness
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narrow spectrum
affect limited range, requires identification of pathogen and sensitivity testing
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effects of combinations:
antagonistic- interfere with each other
synergistic- one enhances the other
additive- neither antagonistic nor synergistic
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only some antimicrobials (antibiotics) can cross the blood brain barrier important in treating:
meningitis
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some antimicrobials (antibiotics) are unstable at low pH:
must be injected not ingested
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rate of half life or elimination dictates
frequency
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intrinsic (innate) immunity
example mycoplasma species lack cell wall makes them resistant tp penicillin and other drugs that attack cell wall
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mycoplasma species are resistant to:
penicillin and other drugs that attack a cell wall
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acquired resistance
spontaneous mutation and horizontal gene transfer
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adverse effects
allergic reactions and toxic effects-examples aminoglycosides, chloramphenicol
suppression of normal microbiota may allow predispose patients to infections example yeast infection from antibiotic
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Antibacterial medications target specific bacterial processes and structures
Cell wall synthesis
Protein synthesis
Nucleic acid synthesis Metabolic pathways
Cell membranes
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B-lactam antibiotics
glycopeptide antibiotics
bacictracin all target
the cell wall (peptidoglycan) synthesis
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fluoroquinolones
| ritamycins target
nucleic acid synthesis
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polymyxins target:
cell membrane integrity
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sulfonamides
| trimethoprim target:
metaboloc pathways (folate biosynthesis)
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```
aminoglycosides
tetracyclines and glycylyclines
marcrolides
chloramphenicol
lincosamides
oxazolidinones
pleuromutlins
streptogramins target:
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protein synthesis
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Streptomyces is:
bacteria that produce antibiotics
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bacillus is:
bacteria that produce antibiotics
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cephalosporium is:
fungi that produce antibiotics
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penicillum is:
fungi that produce antibiotics
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Peptidoglycan:
in bacterial cell wall: unique, great target, often have high therapeutic index
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B-lactum antibiotics:
have B-lactam rings, interfere PG synthesis by preventing crosslinks between glycan chains, Only effective against growing bacteria
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B-lactamase:
enzymes that break down B-lactum rings (gram negative bacteria produce a much wider variety than gram positive)
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penicillins:
side chains have been chemically modified to create derivatives, each has unique characteristics
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cephalosporins:
more resistant to destruction by B-lactamases, the later generations are generally more effective against gram negative and less susceptible to destruction by B-lactamase
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glycopeptide antibiotics
interfere w/ PG synthesis, weakens cell wall, causes lysis, Gram positive bacteria; do not cross the outer membrane of gram negative, low therapeutic index. example vancomycin
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vancomycin:
last resort for treating serious infections caused by gram positive resistant B-lactam drugs, poorly absorbed by intestinal tract administered through IV only.
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vancomycin treats
1. blood infection caused by staphylococcus bacteria, sepsis caused by bacteria, severe infection caused by staphylococcal bacteria, bacterial infection of the heart valve due to streptococcus as well as enterococcus, diptheroids,bacterial pneumonia caused by staph, skin infection caused by staph aureus bacteria, group b strep, bacterial meningitis, anthrax bacteria
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bacitracin works by
interferes with transport of PG precursors across membrane, toxic, used only as topical ointment OTC first aid skin care
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bacitracin treats
Bacitracin works by stopping the growth of certain This antibiotic only prevents bacterial infections. It will not work for virus or fungus infections bacteria. used to prevent minor skin infections caused by small cuts, scrapes, or burns
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aminoglycosides bind to 30S ribosomal unit
blocks initiation
of translation, causes misreading of mRNA
Ineffective against anaerobes, enterococci
and streptococci: enter cells via active transport
Used together with β-lactam drugs: allows aminoglycoside enters the cells after cell wall is compromised Often toxic, used when no other alternatives examples:Streptomycin, gentamycin, and tobramycin
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streptomycin treats
is an antibiotic used to treat a number of bacterial infections. This includes tuberculosis, Mycobacterium avium complex, endocarditis, brucellosis, Burkholderia infection, plague, tularemia, and rat bite fever.[2] For active tuberculosis it is often given together with isoniazid, rifampicin, and pyrazinamide.[3] It is given by injection into a vein or muscle.[2]
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streptomycin is
Streptomycin is in the aminoglycoside class of medication. It works by blocking the ability of 30S ribosomal subunits to make proteins which results in bacterial death.[2]
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gentamycin treats
is an antibiotic used to treat several types of bacterial infections.[1] This may include bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not effective for gonorrhea or chlamydia infections. It can be given intravenously, by injection into a muscle, or topically.[1] Topical formulations may be used in burns or for infections of the outside of the eye.[2
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gentamycin is
Gentamicin is a type of aminoglycoside. It works by stopping the bacteria from making protein, which typically kills the bacteria.[1]
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tobramycin treats
Tobramycin has a narrow spectrum of activity and is active against Gram-negative bacteria. Clinically, tobramycin is frequently used to eliminate Pseudomonas aeruginosa, UTI, staph infec
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Tetracyclines and Glycylcyclines inhibit protein synthesis :
bind to 30S subunit ribosomes, blocks tRNA
attachment, prevent translation Effective against certain Gram positives and Gram negatives
Glycylcyclines have wider activity, effective against bacteria that are resistance to tetracylines (It works by blocking the bacteria's ability to make protein)
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tetracycline treats
gram positive bacteria infections, syphilis, acne, lym disease, chlamydia, gonorrhea, acute bronchitis, ricketsiosis
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glycylcycline treats
derived from tetracycline designed to over come tetracycline resistance
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macrolides Bind to 50S subunit, prevent continuation of translation
Alternative for patients allergic to penicillins Kills most Gram positives but not effective against Enterobacteriaceae family
examples : Erythromycin, clarithromycin, and azithromycin
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erythromycin treats
is an antibiotic useful for the treatment of a number of bacterial infections.[2] This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, and syphilis. It may also be used during pregnancy to prevent Group B streptococcal infection in the newborn.[it is a macrolide.
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azithromycin treats
is an antibiotic useful for the treatment of a number of bacterial infections.[2] This includes middle ear infections, strep throat, pneumonia, traveler's diarrhea, and certain other intestinal infections. It may also be used for a number of sexually transmitted infections including chlamydia and gonorrhea (macrolide)
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clarithromycin treats
is an antibiotic used to treat various bacterial infections.[1] This includes strep throat, pneumonia, skin infections, H. pylori infection, and Lyme disease, among others. Clarithromycin is primarily used to treat a number of bacterial infections including: pneumonia, Helicobacter pylori and as an alternative to penicillin in strep throat.
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Staphylococcus aureus is
a gram-positive, round-shaped bacterium that is a member of the Firmicutes, and is frequently found in the nose, respiratory tract, and on the skin.
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Chloramphenicol is
Binds to 50S ribosomal subunit, prevents peptide bond formation Wide spectrum, used as last resort: aplastic anemia (inability to form WBC and RBC)
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Chloramphenicol treats
Because of its excellent blood-brain barrier penetration (far superior to any of the cephalosporins), chloramphenicol remains the first-choice treatment for staphylococcal brain abscesses,Chloramphenicol is active against the three main bacterial causes of meningitis: Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae
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interfere with cell membrane integrity (causes cell leak and cell death)
daptomycin- treats gram pos only that are resistant
| polymyxin B- binds to gram neg also eukaryotic cells common in first aid ointment topical use
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mycobacterium tuberculosis: waxy cell wall prevents entry, slow growth
First line drugs: preferable, most effective, least toxic, 4 drugs for 8wks, 2 drugs for another 18 wks. Second line drugs: for strains that
are resistant to first line drugs, less effective, more toxic. isoniazid, ethambutol, pyrazinamide
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isoniazid treats
mycobacterium tuberculosis inhibits mycolic acid synthesis
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ethambutol treats
mycobacterium tuberculosis inhibits enzyme required for synthesis of other cell wall components
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pyrazinamide treats
mycobacterium tuberculosis blocks restart of stalled ribosomes
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Antimicrobial Susceptibility Testing:
| Kirby-Bauer Disc Diffusion Test
Routinely used, Bacteria uniformly spread on agar
plate, add antibiotic discs
Drugs diffuse outward, establish gradient,
Formation of “zone of inhibition”:where no visible growth, Diameter of clear zone reflects susceptibility to antimicrobial
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Resistance to Antimicrobial Medications
acquisition of resistance:
1. spontaneous mutation
2. gene transfer
ex. of emerging resistant antibiotics: vancomycin-resistant enterococci (VRE)
multidrug resist tuberculosis (MDR-TB) and extensive drug res TB (XDR-TB). mrthicillin resistant Staph Aurea (MRSA)
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Mechanisms of Action of Antiviral Medication
Difficult to target selectively: lack cell
walls, ribosomes, and other structures, Potential targets: polymerase, Current medication are generally
effective against one specific virus, cant eliminate latent viral infections
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antiviral medications:
Amantadine and rimantadine: prevent viral
uncoating, block influenza virus, Acyclovir and ganciclovir: nucleoside
analog, interfere with nucleic acid synthesis
Entry inhibitors and protease inhibitors:
used to treat HIV and Hep C infection
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Mechanisms of Action of Antifungal Medications
Fungi: eukaryotic pathogen, difficult to target, closer resemblance to human cells,
Most antifungal chemicals target ergosterol: interfere with plasma membrane
synthesis and function
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antifungal medications:
Polyenes: produced by Streptomyces, quite toxic to humans, systemic use for life-threatening infections, eg. amphotericin B and nystatin, Azoles: imidazoles (eg. ketoconazoles,
miconazoles and clotrimazoles) and triazoles (eg. fluconazoles and
voriconazoles) Allylamines, eg. naftifine and terbinafine
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Mechanisms of Action of Antiprotozoan and
| Antihelmintic Medication
Interferes with biosynthetic pathways of protozoans or
| neuromuscular function of worms, Relatively little research and development
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Antiprotozoan and
| Antihelmintic Medications:
Against intestinal protozoa: iodoquinol, nitazoxanide, metronidazole, Against Plasmodium and Toxoplasma: folate antagonists (pyrimethamine,
sulfonamide), malarone, quinolones, Against Trypanosoma: eflornithine, melarsoprol , Against intestinal and tissue helminths: avermectins
