Lecture 12: Antimicrobial Susceptibility Testing

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Questions and Answers

What type of microorganism can be found as normal flora in the nasopharynx of healthy individuals?

Streptococcus pneumoniae

Moraxella catarrhalis

All of the above (correct)

Haemophilus influenza

Which of the following bacteria cannot grow in the absence of oxygen?

Pseudomonas (correct)

Fusobacterium

E. coli

Bacteroides

What type of organism requires oxygen for survival and is present in aerated moist soil containing organic carbon sources?

Aerotolerant

Obligate anaerobe

Aerobic bacteria (correct)

Facultative anaerobe

Which of the following bacteria are classified as facultative anaerobes?

E. coli Signup and view all the answers

What term pertains to an organism that does not require oxygen for growth but can tolerate its presence?

Aerotolerant Signup and view all the answers

Which of the following bacteria are obligate aerobes?

Pseudomonas Signup and view all the answers

What type of anaerobe cannot grow in the presence of oxygen?

Obligate anaerobe Signup and view all the answers

Which of the following is an example of a beneficial aerotolerant organism?

Lactobacillus Signup and view all the answers

What is unique about facultative bacteria?

They can behave both aerobically and anaerobically Signup and view all the answers

What is the primary function of an anaerobic indicator?

To detect the presence of oxygen Signup and view all the answers

Why are microaerophilic bacteria not considered anaerobic?

They require some oxygen, but in very low concentrations Signup and view all the answers

What is the purpose of the GasPak envelope in an anaerobic jar?

To create anaerobic conditions Signup and view all the answers

What is the outcome of the candle burning in a candle jar?

Oxygen deprivation, creating an anaerobic atmosphere Signup and view all the answers

What is the primary purpose of an anaerobic jar?

To cultivate anaerobic bacteria Signup and view all the answers

What is the function of the glove-like sleeves in an anaerobic box?

To handle cultures inside the box Signup and view all the answers

What are the three main methods of cultivating anaerobic bacteria?

Atmosphere free of oxygen, anaerobic indicator, and anaerobic jar Signup and view all the answers

What is the result of adding water to the GasPak envelope in an anaerobic jar?

Consumption of oxygen and production of carbon dioxide Signup and view all the answers

What is the primary function of the Epsilometer test?

To quantify the antimicrobial susceptibility of microorganisms Signup and view all the answers

What is the characteristic of anaerobic bacteria?

They grow best in the absence of oxygen Signup and view all the answers

What is the term for the lowest concentration of an antimicrobial that inhibits the visible growth of a microorganism?

Minimum Inhibitory Concentration (MIC) Signup and view all the answers

What is the purpose of the rectangular plastic strips in the Epsilometer test?

To provide a continuous and exponential gradient of antibiotic concentration Signup and view all the answers

What is the characteristic of aerobic bacteria?

They require high levels of oxygen to grow Signup and view all the answers

What is the definition of 'cultivate' in the context of bacteria?

To nurture and help grow bacteria Signup and view all the answers

What is the term for the biological activity wherein microorganisms multiply themselves in a predetermined culture media?

Bacteria culture Signup and view all the answers

Which of the following species is an example of bacteria that can grow in aerobic conditions?

Staph.epidermidis Signup and view all the answers

Study Notes

Antimicrobial Susceptibility Testing

Epsilometer test (E-test) is a quantitative method that provides direct quantification of antimicrobial susceptibility of microorganisms.
It combines disk diffusion pattern with the determination of Minimum Inhibitory Concentration (MIC).
MIC is the lowest concentration of an antimicrobial that inhibits the visible growth of a microorganism.
E-test uses rectangular plastic strips with a predefined, continuous, and exponential gradient of antibiotic concentration.

Bacteria Culture and Cultivation

Cultivation of bacteria is a biological activity where microorganisms multiply themselves in a predetermined culture media under laboratory conditions.
Most bacteria can grow to some extent in the presence of oxygen, known as aerobic culture.
Species that are naturally found in low oxygen environments, such as in deep wounds or abscesses, will typically grow best in the absence of oxygen – anaerobic culture.
Examples of bacteria that can grow in aerobic culture include Staph. epidermidis, Staph. aureus, Streptococcus pneumoniae, Haemophilus influenza, and Moraxella catarrhalis.

Oxygen Requirements for Bacterial Growth

Microorganisms can be found as normal flora in the nasopharynx of healthy individuals.
Some bacteria cannot grow in the presence of oxygen at all, e.g. Fusobacterium and Bacteroides.
Some bacteria cannot grow in the absence of oxygen, e.g. Pseudomonas and Mycobacterium tuberculosis.
Some bacteria can grow in either aerobic or anaerobic conditions, switching from aerobic respiration to fermentation or anaerobic respiration if oxygen is absent, e.g. E. coli, Salmonella, Listeria, and Staphylococci.

Aerotolerant Organisms

Aerotolerant organisms are those that do not require oxygen for growth but can tolerate its presence.
An aerotolerant organism is classified as an anaerobe.
Examples of aerotolerant organisms include Strept. pyogenes (harmful) and Lactobacillus (beneficial).

Cultivation of Aerobic and Anaerobic Bacteria

Aerobic bacteria require oxygen for survival and are present in aerated moist soil containing organic carbon sources.
There are two main types of aerobic bacteria: obligate aerobes and facultative and microaerophile aerobes.
Obligate aerobes compulsorily require oxygen for energy, growth, and cellular respiration.
Facultative bacteria can behave both aerobically and anaerobically, depending on the prevailing conditions.
Microaerophilic bacteria require oxygen but in very low concentrations.
Anaerobic bacteria can be cultivated using an atmosphere free of oxygen, an anaerobic indicator, and an anaerobic jar with a catalyst.

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Description

This quiz covers the principle of Epsilometer test (E test) for antimicrobial susceptibility of microorganisms, including the method's application and Minimum Inhibitory Concentration (MIC) determination.