Fall 23 Final Exam Study Guide: Microbiology for Health Professionals • Specimen Collection o When is the best time to collect a specimen for culture? o Sterile containers vs nonsterile containers o What information is needed when labeling a specimen? o Most common source of contamination and how contamination usually come about in these samples in a hospital setting. • Media and Biochemical Tests: BAP, MAC, indole, TSI, coagulase o Know the difference between nonselective, selective, and differential media. o Explain how the appropriate media is chosen when plating specimens. o Whether plates are nonselective, selective, and differential as well as what they are selective/differential for o Know how to determine between a positive and negative result when preforming a biochemical test. o How each bacterium we used in class responds/looks on different plates and biochemical tests • Streaking for isolation o Explain the purpose of streaking for isolation. • Antibiotic Susceptibility Testing o What the Kirby Bauer Test is and how it demonstrated antibiotic Susceptibility, o How you would choose an antibiotic to treat an infection when considering the Kirby Bauer test results o Ways to prevent antibiotics resistance: finishing the entire prescription of antibiotics, not sharing antibiotics with others, only prescribing during an infection (seek professionals/don’t self-medicate and share), proper food prep, learning about antibiotic resistance and advocacy/teaching others • Case Study o Be able to identify the following organism when given the growth on media and biochemical test results: ▪ E. coli ▪ P. vulgaris ▪ K. pneumoniae ▪ Shigella sp

Fall 23 Final Exam Study Guide: Microbiology for Health Professionals

• Specimen Collection

o When is the best time to collect a specimen for culture?

o Sterile containers vs nonsterile containers

o What information is needed when labeling a specimen?

o Most common source of contamination and how contamination usually come about in these samples in a hospital setting.

• Media and Biochemical Tests: BAP, MAC, indole, TSI, coagulase

o Know the difference between nonselective, selective, and differential media.

o Explain how the appropriate media is chosen when plating specimens.

o Whether plates are nonselective, selective, and differential as well as what they are selective/differential for

o Know how to determine between a positive and negative result when preforming a biochemical test.

o How each bacterium we used in class responds/lookson different plates and biochemical tests

• Streaking for isolation

o Explain the purpose of streaking for isolation.

• Antibiotic Susceptibility Testing

o What the Kirby Bauer Test is and how it demonstrated antibiotic Susceptibility,

o How you would choose an antibiotic to treat an infection when considering the Kirby Bauer test results

o Ways to prevent antibiotics resistance: finishing the entire prescription of antibiotics, not sharing antibiotics with others, only prescribing during an infection (seek professionals/don’t self-medicate and share), proper food prep, learning about antibiotic resistance and advocacy/teaching others

• Case Study

o Be able to identify the following organism when given the growth on media and biochemical test results:

▪ E. coli

▪ P. vulgaris

▪ K. pneumoniae

▪ Shigella sp.

• Specimen Collection
o When is the best time to collect a specimen for culture?
- Ideally, specimens should be collected when the patient's condition is most active, often before antibiotic therapy begins, to ensure the most accurate identification of pathogens.
o Sterile containers vs nonsterile containers
- Sterile containers should be used to prevent contamination, while nonsterile containers may introduce unwanted microorganisms.
o What information is needed when labeling a specimen?
- Proper labeling requires the patient's name, the date and time of collection, the type of specimen, and any specific tests to be performed.
o Most common source of contamination and how contamination usually comes about in these samples in a hospital setting.
- Contamination typically arises from skin flora or unsterile techniques during collection, which can lead to incorrect results.

• Media and Biochemical Tests: BAP, MAC, indole, TSI, coagulase
o Know the difference between nonselective, selective, and differential media.
- Nonselective media support the growth of a wide variety of organisms, selective media favor the growth of certain organisms while inhibiting others, and differential media allow differentiation between closely related organisms based on their biochemical properties.
o Explain how the appropriate media is chosen when plating specimens.
- Media is chosen based on the suspected pathogen and its growth requirements, as well as the characteristics observed in the clinical presentation.
o Whether plates are nonselective, selective, and differential as well as what they are selective/differential for
- E.g., BAP is nonselective, while MAC is selective for Gram-negative organisms and differential for lactose fermenters.
o Know how to determine between a positive and negative result when performing a biochemical test.
- Positive tests show a change in color or production of gas while negative tests do not exhibit such changes.
o How each bacterium we used in class responds/looks on different plates and biochemical tests
- Familiarize with results like the color and growth patterns of specific bacteria on different media.

• Streaking for isolation
o Explain the purpose of streaking for isolation.
- Streaking helps to isolate individual bacterial colonies from a mixed sample, allowing for the identification of specific organisms based on their colony characteristics.

• Antibiotic Susceptibility Testing
o What the Kirby Bauer Test is and how it demonstrates antibiotic susceptibility.
- The Kirby Bauer Test involves spreading a bacterial culture on agar and placing antibiotic-impregnated disks on the surface; the zones of inhibition indicate susceptibility or resistance.
o How you would choose an antibiotic to treat an infection when considering the Kirby Bauer test results
- Select antibiotics that show larger zones of inhibition against the identified organism, suggesting efficacy.
o Ways to prevent antibiotics resistance:
- Finish the entire prescribed course, do not share antibiotics, only take antibiotics for confirmed bacterial infections, ensure proper food preparation, and educate on antibiotic resistance.

• Case Study
o Be able to identify the following organisms when given the growth on media and biochemical test results:
▪ E. coli
▪ P. vulgaris
▪ K. pneumoniae
▪ Shigella sp.

Comparison of E. coli, P. vulgaris, K. pneumoniae, and Shigella sp.

This table highlights the primary biochemical markers used to differentiate these four Gram-negative bacilli.

Key Diagnostic Tips:

• The "Mucoids": If the colonies are extremely slimy and "stringy," it is likely K. pneumoniae.

• The "Inert" ones: If the bacteria are non-motile and mostly negative across tests, suspect Shigella.

• The "Sheen": Only E. coli typically produces the metallic green sheen on EMB agar.

• ulThe "Swarmers": If the agar is covered in waves of growth, it is likely P. vs.

• The "Swarmers": If the agar is covered in waves of growth, it is likely P. vulgaris.