MLS 2214 Exam 2

Anaerobes are found as normal flora in:

• Lower intestines

• Skin

• upper respiratory tract

• Vagina

The end products of respiration include:

ATP and water

A moderate anaerobe is unable to multiply in  ___ percent of oxygen:

2-8%

How many oxygen radicals are produced by a typical human cell each day?

1 trillion

Bacteroides can grow in the presence of:

Kanamycin

Bile

Colistin

Vancomycin

Prevotella can grow in the presence of:

Kanamycin
Colistin

Which of the following are true:

The toxin responsible for botulism is alpha toxin

The Gram stain reaction for C. tetani resembles tennis rackets

 Pseudo membrane colitis can result from C. difficile

 A reverse CAMP reaction can be seen with C. perfringens

 Gas gangrene is caused by C. botulinum

The Gram stain reaction for C. tetani resembles tennis rackets

 Pseudo membrane colitis can result from C. difficile

 A reverse CAMP reaction can be seen with C. perfringens

Sulfur granules may be seen in abscesses of patients infected with:

Actinomyces

Which organism is a predominant normal flora of the skin and is a common contaminant in blood cultures?

Propionibacterium acnes

Which of the following are often found in human bite wounds?

P. anaerobius

S. aureus

 E. corrodens

Mycobacterium tuberculosis complex includes:

M. bovis

M. tuberculosis

 M. africanum

Which stain for viewing Mycobacteria is heated:

 

Ziehl-Neelsen stain

The term used to identify mycobacteria that produce pigments only in the presence of light is:

photochromogens

Prior to plating mycobacterium specimens, 2% NaOH is used to:

kill non-mycobacterial organisms

The stage of TB where hypersensitivity causes tissue damage is known as:

secondary infection

The species of mycobacterium that can cause cervical lymph infections is:

Mycobacterium scrofulaceum

Which of the following can cause inclusion conjunctivitis?

C. trachomatis

Which of the following may cause pneumonia?

C. trachomatis

C. psittaci

S. pneumoniae

Which of the following causes Q fever?

C. burnetti

Which of the following are true regarding Mycoplasma:

smallest known bacteria

may be prevented with the BCG vaccine

 can cause walking pneumonia

 cell wall contains mycolic acid

smallest known bacteria

 can cause walking pneumonia

Where in the body are anaerobes normal flora?

• Intestinal tract

• Urethra

• Vagina

• Oral cavity and upper respiratory tract

• Skin and mucous membranes

What genus is the most abundant group of bacteria in the intestinal tract and oral cavity?

Bacteroides

name the organism that accounts for 43% of all clinical anaerobic isolates

Bacteroides fragilis

What 5 anaerobes make up 2/3rds of all infections?

• Bacteroides fragilis group

• Porphyromonas and Prevotella

• Fusobacterium nucleatum

• Clostridium perfringens

• ANA cocci

What is the ratio of anaerobes of aerobes in the intestinal tract?

1000 to 1

What percentage of bacteria found in the saliva, nasal washings, gum and teeth are anaerobes?

90%

What are an endogenous infection?

An infection caused by one’s own flora

What are exogenous infections?

An infection caused by outside flora

What conditions predisposes a patient to an anaerobic infection?

• Human/animal bites

• Aspiration of oral contents into the lungs after vomiting

• Oral surgery or injury

• Gi tract surgery or injury

• Genital tract surgery or injury

• Rubbing dirt into a wound

What are the indications for an anaerobic infection?

• Infection near a mucosal surface

• Infections persist despite aminoglycoside therapy

• Presence of a foul odor or large amounts of gas

• Black color or brick-red florescence

• Presence of macroscopic sulfur granules

What are the three metabolic pathways?

• Respiration

• Anaerobic respiration

• Fermentation

What is the final electron acceptor in respiration

An inorganic compound, usually oxygen

What is the final electron acceptor in anaerobic respiration

Uses the same pathway as respiration, but the final electron acceptor is nitrate, sulfate or carbon dioxide

What is the final electron acceptor in fermentation?

Organic compound either and acid or alcohol

What are the end products of fermentation?

Large amounts of acids and alcohols

Small amounts of ATP

What are the end products of aerobic and anaerobic respiration?

Small amounts of acid

large amounts of ATP and H2O

Define obligate aerobe

Grows only in the presence of O2

Define aerotolerant anaerobe

Grows only in the absence of O2, unable to multiply in more 2-8% O2

Define microaerophilic aerobe

Requires low concentration of O2 at 2-10%

Define obligate anaerobe

Only grows in the absence of O2

Define moderate anaerobe

Unable to multiple in more than 2-8% O2

Define strict anaerobe

Cannot multiply in more than 0.5% O2

Define facultative anaerobe

Can use O2 if present but also can grow anaerobically

Most human pathogens are this

Define capnophile

Grows in 5-15% CO2

What are the percentages of gases in an air incubator?

• 21% Oxygen

• 0.03 CO2

• 79% N2

What are the percentages of gases in an CO2 incubator?

• 15% O2

• 5-10% CO2

What are the percentages of gases in an anaerobic system incubator?

• 0-0.5% O2

• 5-10% H2

• 5-10% CO2

• 80-90% N2

What is a free radical?

An electron with one too many or few electrons, they will steal electrons from other molecules around them

What effect do free radiales have on proteins, DNA, ad lipids

They can cause oxidative damage, leading to mutations, dysfunction, or cell death.

What can free radicals do to other molecule they come into contact with?

Steal an electron

How many free radicals are produced each day in the human body?

1 trillion

What is the name of accumulated damage due to oxygen free racicals?

Oxidative stress

What happens to the body’s natural ability to fight free radicals as we age?

It decreases, and we make more free radicals as we get older so more damage accumulates

What is the body’s natural defense mechanism against free radicals

Antioxidants, which donate an electron to the molecule that’s missing one

What are three examples of antioxidants that are found outside of the body?

Vitamin A, C, and E

What two things does oxygen produce in the body?

• Free radicals

  • Have either too many or few electrons

• Toxic oxygen derivates

  • Hydroxide radical

What effect do free radicals have on proteins, DNA, and lipids?

• Proteins: denatures

• DNA: Mutates

• Lipids: Damage the phospholipid bilayer

What are the two enzymes that eliminate toxic radicals and toxic oxygen derivates

• Superoxidase dismutase

• Catalase

Why is O2 so toxic to anaerobes?

They don’t have the mechanism to deal with free radicals

What is the chemical equation for superoxide dismutase?

4 O2•− + 4 H+ —Superoxide dismutase→ 2H2O2 + O2

What is the chemical reaction for catalase

2 H2O2 —Catalase→ 2 H2O + O2

What is used to eliminate hydrogen peroxide?

Catalase

What bacteria has neither catalase nor superoxidase dismutase?

Strict anaerobes

What bacteria has small amounts of catalase and superoxidase dismutase?

• Microaerophile

• Aerotolerant anaerobes

What type of bacteria has both catalase and superoxidase dismutase?

• Strict aerobes

• facultative anaerobes

Why is an aspirate preferred to a swab for anaerobic specimen collection?

A swab will be exposed to oxygen while a needle aspirate won’t be

What are PRAS

• Pre-reduced anaerobically sterilized transport and culture media

• Oxygen has been removed or reduced

What are the conditions in a jar when using a Gas-Pak

• 0.2% O2

• H2 5-10%

• CO2 5-10%

What is used for QC for the gas pak

Methylene blue indicators

What does is mean if a methylene blue strip has turned blue in a gas pak?

Indicates that there is oxygen in the jar

What is an aerotolerance test?

Where duplicate plates are incubated both aerobically and anaerobically

What are the different special potency antimicrobial discs used to identify anaerobes?

• Vancomycin

• Colistin

• Kanamycin

• Sodium polyethene sulfonate (SPS)

• Nitrate

• Bile

What are the three things that an egg yolk agar are looking for?

1. Lecithinase production

2. Proteolysis

3. Lipase activity

What does a positive lecithinase reaction look like on an egg yolk agar?

White opaque colonies

What does a positive lipase reaction look like on an egg yolk agar?

Mother of pearl or oil slick look

What does a positive proteolysis reaction look like on an egg yolk agar?

Clear zone around the colony

What is a biochemical ID system?

A system used to identify microorganisms based on their biochemical reactions to specific substrates, enabling classification and differentiation of species.

What is GLC?

Gas-liquid chromatography

What is a chemical fingerprint

A unique profile of biochemical reactions or molecular characteristics that can be used to identify and differentiate between various substances or organisms.

What species are lecithinase negative?

• C. botulinum

• Bacteroides fragilis

• Cutibacterium acnes

What species are lecithinase positive?

• C. perfringens

What species are lipase negative?

• C. perfringens

• Bacteroides fragilis

What species are lipase positive?

• Clostridium botulinum

• Fusobacterium nucleatum

• Cutibacterium acnes

What genera are anaerobic GNRs

• Bacteroides

• Fusobacterium

• Porphyromonas

• Prevotella

What genera are spore forming GPRs

Clostridium

What genera are non spore forming GPRs

• Actinomyces

• Cutibacterium

• Bifidobacterium

• Eubacterium’

• Lactobacillus

• Mobiluncus

What genera are anaerobic GPC

• Peptostreptococcus

What genera are anaerobic GNC

• Veillonella

What types of infections would you expect to see in a Bacteroides fragilis infection?

Soft tissue infection

What is Bacteroides fragilis resistant to?

• Kanamycin

• Vanc

• Colosin

• Bile tolerant

What is a BBE?

• Bacteroides bile plate

• 20% Biles salts

• 1% Esculin

• Ferric ammonium

What does Bacteroides look like on a KVLB?

Medium translucent colonies

What does Bacteroides look like on an egg yolk agar?

Since its lecithinase and lipase negative it looks kind of normal

What is this?

Bacteroides fragilis

What does Bacteroides fragilis look like on a gram stain?

small, pleomorphic GNR

Where is Fusobacterium normal flora?

• Upper respiratory tract

• Gastrointestinal tract

• Urethra

Where does Fusobacterium normally cause infections?

• Head

• Neck

• Lower respiratory tract

What does Fusobacterium nucleatum look like on a gram stain?

Long thin tapered GNRs

What does Fusobacterium mortiferum look like on a gram stain?

Pleomorphic rods with globular swelling

What genus is resistant to vanc, but susceptible to colistin and kanamycin?

Fusobacterium