Overview of antimicrobials

what are the components of the infectious disease triad?

bacteria, host, and drug

what are the two factors/concepts at play in the relationship between drugs and the host?

toxicodynamics and pharmacokinetics

what are the two factors/concepts at play in the relationship between drugs and the bacteria?

pharmacodynamics and resistance (efficacy)

what are the two factors/concepts at play in the relationship between bacteria and the host?

infection and host defenses (neutrophils, etc)

which bacteria is the main cause of bacterial meningitis?

streptococcus pneumoniae

which bacteria is the main cause of otitis media

streptococcus pneumoniae

which bacteria is the main cause of community-acquired pneumonia

streptococcus pneumoniae

which bacteria is the main cause of skin infections

staphylococcus aureus

which bacteria is the main cause of eye infections

staphylococcus aureus

which bacteria is the main cause of upper respiratory tract infections?

streptococcus pyogenes

which bacteria is the main cause of sinusitis

streptococcus pneumoniae

which bacteria is the main cause of gastritis

helicobacter pylori

which bacteria is the main cause of food poisoning

campylobacter jejuni

which bacteria is the main cause of UTIs

escherichia coli

which bacteria is the main cause of sexually transmitted diseases

chlamydia trachomatis.

T/F: we are able to develop antibiotics faster than bacteria can mutate

false

how long does it typically take for bacteria to develop new characteristics/mutations?

~20 minutes

T/F: every antibiotic develops resistance

true

what is the major cause of resistance?

dosing or poor antibiotic selection.

what are patient considerations in ID?

host, infection (site and severity), MICs to second antibiotic, and treatment regimens not disclosed such as 2-hour prolonged infusions for meropenem

what things indicate an infection in the host

spike in neutrophils/WBCs and a fever

what is the balancing act for antibiotic usage?

selecting a drug and dose that will maximize efficacy but minimize toxicity and resistance

what is the process and timing of antibiotic treatments

samples collected and viewed using gram staining (how does it look under the microscope?) within 12 hours, then identification of the organism (name) and organism susceptibilities (what antibiotic is this specific bacteria susceptible to?) determined over next 48-96 hours.

where to find information on what each bacteria look lie using gram staining

book/guideline

where to find information to identify organisms’ susceptibilities?

antibiogram or resistance patterns.

where to find information on which agent is best when provided the susceptibilities?

PK/PD information

what type of antibiotic is typically given originally while patient is awaiting test results?

broad spectrum, empiric therapy.

is ampicillin a narrow spectrum or broad spectrum

narrow

is imipenem a narrow spectrum or broad spectrum

broad

T/F: the higher the number is on antibiotic susceptibility profiles, the more likely it is to kill that bacteria

true

describe the concept of collateral damage

Unintended side effects caused by antibiotics, like the destruction of beneficial bacteria in the body (which can lead to issues like digestive problems, infections, or antibiotic resistance) - the selection of drug-resistant organisms and the unwanted development of colonization or infection with multidrug-resistant organisms

what is MIC

the lowest concentration of an antibiotic that completely inhibits the growth of a microorganism in vitro; expressed as a concentration (micrograms/mL)

what are breakpoints

discriminatory antimicrobial concentrations used in the interpretation of results of susceptibility testing to define isolates as susceptible, intermediate, or resistant

what is MBC

the lowest concentration of the antibiotic which results in a 99.9% reduction in colony forming units in a given time

what are the different MIC breakpoints

susceptible (S), intermediate (I), and resistant (R)

define susceptible for MIC breakpoints

clinical success can be expected if treated with usual doses

define intermediate MIC breakpoints

clinical success may be possible if: high doses of antibiotic ae used, antibiotic concentrates at the site of infection, and possible combination agents are used

define resistant MIC breakpoints

treatment failure is expected

how can MIC be determined?

using broth microdilution

how do broth microdilutions work?

bacteria in a liquid are exposed to increasing concentrations of drug

what is the MIC during broth microdilutions

lowest concentration of an antimicrobial that results in the inhibition of visible growth of a microorganism