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

Specimen Collection

The process of collecting samples from patients for microbiological analysis.

Best time to collect a specimen for culture

When the patient's condition is most active, often before antibiotic therapy begins.

Sterile containers

Containers used to collect specimens to prevent contamination.

Nonsterile containers

Containers that may introduce unwanted microorganisms during specimen collection.

Information needed when labeling a specimen

Patient's name, date and time of collection, type of specimen, and specific tests to be performed.

Common source of contamination in specimens

Typically arises from skin flora or unsterile techniques during collection.

Nonselective media

Media that supports the growth of a wide variety of organisms.

Selective media

Media that favors the growth of certain organisms while inhibiting others.

Differential media

Media that allows differentiation between closely related organisms based on biochemical properties.

Choosing media for plating specimens

Based on suspected pathogen, growth requirements, and clinical presentation characteristics.

BAP (Blood Agar Plate)

A nonselective media that supports the growth of various organisms.

MAC (MacConkey Agar)

A selective media for Gram-negative organisms and differential for lactose fermenters.

Positive biochemical test result

Exhibits a change in color or gas production.

Negative biochemical test result

Shows no change indicating no reaction.

Purpose of streaking for isolation

To isolate individual bacterial colonies from a mixed sample.

Kirby Bauer Test

A test that determines antibiotic susceptibility by measuring the zones of inhibition around antibiotic disks.

Choosing antibiotics based on Kirby Bauer results

Select antibiotics showing larger zones of inhibition against the identified organism.

Preventing antibiotic resistance

Finishing the entire course of antibiotics, not sharing antibiotics, and proper education on the topic.

E. coli

A bacterium commonly identified through growth on media and biochemical tests.

P. vulgaris (Proteus vulgaris)

A bacterium that can be identified by specific characteristics on culture media.

K. pneumoniae (Klebsiella pneumoniae)

A bacterium identifiable through its growth patterns and biochemical reactions.

Shigella sp.

A group of bacteria identifiable by their growth on selective media.

Streaking technique

A method used to dilute a sample of bacteria to isolate colonies.

Antibiotic susceptibility demonstration

Measured using the Kirby Bauer Test by observing zones of inhibition.

Inhibition zone

Area around antibiotic disks in the Kirby Bauer test where bacteria do not grow, indicating susceptibility.

Importance of completing antibiotics

To ensure the complete eradication of pathogens and prevent resistance.

Food preparation and antibiotic resistance

Proper food handling can prevent infection and reduce the need for antibiotics.

Labeling specimens

Critical for accurate identification and testing of collected samples.

Contamination prevention

Using sterile techniques during specimen collection to minimize microbiological errors.

Clinical presentation

Characteristics observed in the patient that guide the selection of media for testing.

Isolation of bacteria

Separation and identification of individual bacterial species from a mixed culture.

E. coli Characteristics

Lactose Fermentation: Positive (Acid), Motility: Motile, Indole: Positive, Methyl Red: Positive, Voges-Proskauer: Negative, Citrate: Negative.

P. vulgaris Characteristics

Lactose Fermentation: Negative, Motility: Swarming, Indole: Positive, Methyl Red: Positive, Voges-Proskauer: Negative, Citrate: Variable.

K. pneumoniae Characteristics

Lactose Fermentation: Positive (Mucoid), Motility: Non-motile, Indole: Negative, Methyl Red: Negative, Voges-Proskauer: Positive, Citrate: Positive.

Shigella sp. Characteristics

Lactose Fermentation: Negative, Motility: Non-motile, Indole: Variable, Methyl Red: Positive, Voges-Proskauer: Negative, Citrate: Negative.

K. pneumoniae

If colonies are extremely slimy and 'stringy', it is likely K. pneumoniae.

Shigella

If the bacteria are non-motile and mostly negative across tests, suspect Shigella.

E. coli

Only E. coli typically produces the metallic green sheen on EMB agar.

P. vulgaris

Characterized by swarming growth patterns on agar, with a distinctive wave-like appearance.