Microbiology Review Flashcards
What are 5 normally sterile sites in the body?
- CNS
- CVS
- Lower respiratory tract
- Bone & Joint
- Genitourinary tract (except urethra and vagina)
What are common bacteria that cause otitis media?
Streptococcus pneumoniae
What are common bacteria that cause pneumonia?
Community - Streptococcus pneumoniae - Haemophilus influenzae - Staphylococcus aureus Atypicals - Legionella pneumophila - Mycoplasma pneumoniae - Chlamydia pneumoniae Tuberculosis - Mycobacterium tuberculosis
What are common bacteria that cause Skin infections?
- Staphylococcus aureus
- Streptococcus pyrogenes
- Pseudomonas aeruginosa
What are common bacteria that cause STDs?
- Chlamydia trachomatis
- Neisseria gonorrhoeae
- Treponema pallidium
- Ureaplasma urealyticum
- Haemophilus ducreyl
What are common bacteria that cause sinusitis?
- Streptococcus pneumoniae
- Haemophilus influenzae
What are common bacteria that cause Upper respiratory tract infections?
- Streptococcus pyrogenes
- Haemophilus influenzae
What are common bacteria that cause UTIs?
- Escherichia coli
- other enterobacteriacae
- Staphylococcus saprophyticus
- Pseudomonas aeruginosa
What are methods used in laboratory diagnostics?
- Microscopy
- Culture
- Biochemistry
- Serologic/immunologic diagnostics
- Molecular/nucleic acid diagnosis
- Mass Spectrometry
What are some characteristics of using MALDI-TOF for organism detection?
- Rapid
- uses patterns to recognize organisms
Time needed to wait for gram stain results?
around 24hours
When should we conduct antimicrobial susceptibility testing?
- Clinically significant isolates (properly collected)
- Possible resistance to primary therapeutic agents
- When standard performance method and interpretive criteria are established
Is there a need to conduct antimicrobial susceptibility testing for Group A streptococci?
No. They are almost always sensitive to the primary therapeutic agent (beta lactams)
How is Minimum Inhibitory Concentration (MIC) obtained using the agar/broth dilution method?
The lowest concentration of an antimicrobial that prevents visible growth of an organism
How is Minimum Inhibitory Concentration (MIC) obtained using the disk diffusion method?
Filter discs contain set concentration of antibiotics
- Diameter (zone of inhibition) corresponds to antimicrobial activity
How is Minimum Inhibitory Concentration (MIC) obtained using the E-test method?
Agar based testing method
- Graduated antibiotics concentrations layered on plastic strip
- MIC read where growth intersects the plastic strip (take higher value if in-between)
What does MIC/zone of inhibition determine?
They help predict therapeutic response
What can we expect from a susceptible organism?
Appropriate to treat with recommended dosage and agent (likely therapeutic success)
What can we expect from an intermediate organism?
Organism may be treated in body sites where the drugs are physically concentrated or at high doses (uncertain response)
What can we expect from a susceptible organism?
Organism not inhibited by usually achievable concentrations of drug with normal dosage schedules (likely therapeutic failure)
Does the antibiotic with the lowest MIC on an AST report indicate it as the best treatment option?
No. The AST is defined differently for every drug-bug pairing
Are MICs of different drugs against a particular organism directly comparable?
No.
What are some factors that affect the in-vivo activity of antibiotics (not seen in AST in-vitro tests)
Immune system
Protein binding of drug
Ability of drug to reach site of infection
Drainage/removal of infected foci
Drug interactions
Some bacteria may only express certain enzymes (that inhibit antibiotic) in-vivo
What is the usual timeline of AST reports?
Day 1: Gram stain
Day 2: Culture organism
Day 3-4: Identify organism + AST
