Microbiology I: Conventional lab Techniques

…: methods used in microbiology lab to determine susceptibility against several antibiotics of a microbial species isolated from a given patient, determines the antimicrobial agents active against the isolated species

Antimicrobial susceptibility testing

… (2) need to be included when making a decision about patient treatment

AST, basic principles of anti-infective therapy

Methods of AST: … (5)

disc diffusion, dilution, E-test, automated, genotypic

In disc diffusion testing the isolated bacterium is characterized as: … (3)

S (susceptible), I (intermediately susceptible, R (resistant)

2 ways to test sensitivity with the broth dilution methods: … (2)

Macrodilution (broth dilution), Microdilution (microplate wells)

…: the lowest concentration of the antibiotic tested that inhibits visual bacterial growth after overnight incubation

minimum inhibitory concentration

In MIC testing the antibiotic needs to be diluted by a …

factor of 2

In microdilution you need a … and a … for each agent tested

positive control (broth + inoculum and no antibiotic), negative control (broth)

…: plastic strips impregnated with a gradually decreasing concentration of a particular antibiotic

E-test

A … E-test strip is needed for each antibiotic, placed on agar and inoculated

separate

…: most use broth microdilution method and provide automated inoculation, reading, and interpretation

Automated susceptibility testing systems

…: the cut-offs in valves to determine susceptibility, intermediate susceptibility and resistance

Breakpoints

…: expression of the breakpoint if disc diffusion method is used

Zone diameter (mm)

…: expression of breakpoint if MIC and broth dilution method is used

concentration (mg/L)

MIC breakpoints are established following analysis of: … (3)

distribution of MICs, pharmacokinetics and pharmacodynamic properties of the antimicrobial, clinical data on patient outcomes

…: inhibited in vitro by a concentration of an antibiotic that is associated with high likelihood of therapeutic success

susceptible

…: inhibited in vitro by a concentration of an antibiotic that is associated with uncertain therapeutic effect 

intermediate

…: inhibited in vitro by a concentration of an antibiotic that is associated with high likelihood of therapeutic failure

resistant