Msk System - Anaerobes

Front 1

What are the factors that inhibit anaerobic growth?

Back 1

Low Oxidation-Reduction potential (Eh = 0 to -300)

Absence of Oxygen (PO2 = 0.5% to 3%)

Front 2

Where are anaerobes best suited to grow within the body?


HINT: Think Eh levels.

Back 2

Periodontal pocket (-50), Dental plaques (-200), Colon (-300).

Front 3

Superoxide Dismutase, Catalase, and Peroxidase are related to anaerobic bacteria in what way?

Back 3

They are typically missing from the bacteria.

Front 4

How would you classify most anaerobic bacteria infections?

HINT: Think gram stain.

Back 4

Most of the infections are polymicrobic, so you will see several different types of bacteria on something like a gram stain.

Front 5

What are some of the clinical findings that might suggest to you, the physician, that the patient has an anaerobic infection?

Back 5

Foul smelling discharge
Necrotic tissue with gas
Black discoloration of blood-containing exudate
Organisms on gram stain do not grow aerobically
location of infection proximal to the mucosal surface
vascular insufficiency
infections following human or animal bites
infection after severe trauma

Front 6

Which areas have the highest incidence of anaerobic infections, and which have the least?

Back 6

LEAST:
Bacteremia - 1-9% incidence
Thoracic Empyems 20-30%
Aspiration Pneumonia 20-50%

MOST:
Brain abscess 60-90%
Dental infection 50-100%
Chronic Sinusitis 50-100%
Intra-abdominal/pelvic abscess 60-100%.

Front 7

How must a collection of possible anaerobic bacteria be obtained?

Back 7

Aspirate pus with a needle/syringe
Swabs that are immediately placed in a reduced transport medium.

Any specimen that likely contains anaerobic normal flora is NOT acceptable (throat swabs, nasal swabs, bowel contents, vaginal swabs)

Front 8

What types of media need to be used for anaerobes?

Back 8

Kanamycin-vancomycin agar
Reduced anaerobic blood agar
Thioglycalate agar

Front 9

What are two characteristics of anaerobic cultures?

Back 9

Must be grown in anaerobic conditions (duh)
Most are very slow growing due to using fermentation for energy.

Front 10

What are some characteristics of Bacteroides fragilis?

Back 10

BACTERIOLOGY
Lightly staining, Gram-negative Rods (usually pleomorphic)
Grow rapidly and are stimulated by bile.
NORMAL HABITAT:
Human gut - 20-30% are Bacteroides
Female Genital tract

Front 11

What are the virulence factors associated with Bacteroides fragilis?

Back 11

Capsule ~75%
Extracellular enzymes: Collagenase, hyaluronidase, etc.
No Endotoxin

Front 12

What are some common infections caused by Bacteroides fragilis?

Back 12

Gastrointestinal abscess
Pelvic inflammatory disease
Cellulitis (mixed infections)

Front 13

What are some general characteristics of Prevotella (Bacteroides) melaninogenicus?

Back 13

Gram Negative coccobacilli to short rods
Brick-red florescence under Wood's Lamp
Distinctive black colonial appearance on agar.

NORMAL HABITAT:
Oral Flora
Low numbers in GI tract

Front 14

What are some infections that are typically caused by Prevotella (Bacteroides) melaninogenicus?

Back 14

Oral and Brain abscesses
Lung abscesses
Female genital tract abscesses

Front 15

What are the recommended treatments for B. fragilis and V. melaninogenicus?

Back 15

Debridement and drainage in cellulitis and severe abscesses.
DOC is metronidazole and clindamycin (they are resistant to tetracyclines and are beta lactamase producers)

Front 16

What are some general characteristics of F. nucleatum?

Back 16

PHYSICAL:
Gram-neg, long slender filaments and fusiform rods.
HABITAT:
Oral cavity
Stool

Front 17

What are some infections caused by F. nucleatum?

Back 17

Head, neck, and chest infections
Synergizes with oral spirochetes resulting in ulcerating, necrotizing gingivitis known as Vincent's Angina, or "trench mouth".

Front 18

What are some general characteristics and infections caused by Peptostreptococcus and other anaerobic streptococci?

Back 18

HABITAT:
Mouth or stool
INFECTIONS:
Synergistic infections with S. aureus and Bacteroides sp.
Brain and head abscesses/infections.

Front 19

General characteristics of A. israelii?

Back 19

Only pathogenic actinomycete that is anaerobic
Gram + branching rods
Produce sulphus granules in abscesses and culture

Front 20

What are some general characteristics of Gram + Spore-formers?

Back 20

Infection often exogenous
Most pathology due to toxins
Toxemia may arise form ingestion of preformed toxins, or from localized infections with release of toxins into the blood stream
Site requires low Eh potential (meaning, they won't normally infect healthy tissue, and will not produce their toxins at a high Eh.)

Front 21

General characteristics of C. perfringens?

Back 21

HABITAT:
GI tract
Soil
INFECTIONS: Cellulitis, Myonecrosis (gas gangrene)
Food Poisoning

Front 22

Virulence factors of C. perfringens?

Back 22

Exotoxins (12): Alpha toxin (lecithinase, phospholipaseC) degrades mammalian cell membranes
Other toxins have hemolytic, cytotoxic, and necrotic effects.

Front 23

What is the typical process of disease in myonecrosis (Gas Gangrene)?

Back 23

C. perfingens infects soft tissue following some sort of severe trauma
Organisms multiply and spread toxins and enzymes while utilizing glycogen
leads to gas, edema, and impaired circulation
vascular destruction and lactic acid build-up lowers redox potential
cellulitis
myonecrosis
shock and renal failure (death in 30% of cases)

NOTE: Lower Eh causes the release of more toxins

Front 24

How is gas gangrene diagnosed in the lab?

Back 24

Gram stain: Gram +, boxcar like rods
On culture, there is a distinctive double zone of hemolysis

Front 25

What is the preferred treatment of gas gangrene?

Back 25

For cellulitis and myonecrosis, wound must be debrided.
Penicillin + Clindamycin

For food poisoning - Self-limited, no treatment necessary.

Front 26

What are the general characteristics of C. tetani?

Back 26

HABITAT:
GI tract
Soil
INFECTIONS:
Tetanus

Front 27

What virulence factors are present in C. tetani?

Back 27

Tetanospasmin, which suppresses the release of NT GABA causing constant muscle contraction.

Front 28

What are the laboratory findings associated with C. tetani?

Back 28

Gram positive motile rods with terminal spores

Front 29

How is C. tetani treated?

Back 29

Antitoxin
Debride tissue of wound
DOC: Penicillin
Support patient
Tracheotomy
quiet, dark, external environment

PREVENTION: DTaP vaccine, with a 10 year booster.

Front 30

What are some CLINICAL characteristics of C. botulinum?

Back 30

ADULT:
vomiting, dizziness, cranial palsy, double vision, swallowing difficulties. Can also lead to respiratory paralysis and death.
CHILDREN: Exotoxin causes constipation and generalized weakness (floppy baby syndrome)

Front 31

What are some virulence factors of C. botulinum?

Back 31

potent neurotoxin of which A,B,E cause human disease. Toxin causes flaccid paralysis by blocking the release of Ach from A-motor neuron.

Front 32

What are the characteristics of C. difficile?

Back 32

DISEASE:
pseudomembranous colitis

Front 33

What are the virulence factors of C. difficile?

Back 33

Toxin A (enterotoxin) causes fluid production and mucosal damage and toxin.
B(Cytotoxin) -> kills mucosal cells

Front 34

How is C. difficile diagnosed in the laboratory, and how is it treated?

Back 34

Clostridium difficile toxin assay
DOC Metronidazole (vancomycin if necessary)

Front 35

A 49 year old white female presents with a gradual onset of a large, foul smelling abscess on her abdomen following surgery in that area. You notice that some of the tissue is starting to become necrotic, and that there are small bubbles of gas underneath the tissue. After taking a sample of the exudate and performing a gram stain, you note that there are several lightly colored, gram - rods. Using this information you determine that the best treatment for this patient is?

Back 35

Debridement of abscess and metronidazole/clindamycin treatment.

Front 36

You are on your morning rounds when you come to a patient who was admitted due to a large abscess in her mouth. As you are presenting the patient to your preceptor, you note that the lab results have come back, and indicate that upon gram staining, there were several gram - coccobacilli and short rods present in the sample. The lab also grew a culture of the offending bacteria, and found that it grew in distinctive black colonies, and had a brick-red flourescence under a wood's lamp. Being the amazing medical student you are, you know that this bacteria is of the anaerobic type, and would most likely form abscesses in what places other than the mouth?

Back 36

Lung
Female genital tract

Front 37

You are on your morning rounds when you come to a patient who was admitted due to a large abscess in her mouth. As you are presenting the patient to your preceptor, you note that the lab results have come back, and indicate that upon gram staining, there were several gram - coccobacilli and short rods present in the sample. The lab also grew a culture of the offending bacteria, and found that it grew in distinctive black colonies, and had a brick-red flourescence under a wood's lamp.

The preferred pharmocological treatment of this infections would be?

Back 37

Metronidazole and clindamycin

Front 38

You are on your morning rounds when you come to a patient who was admitted due to a large abscess in her mouth. As you are presenting the patient to your preceptor, you note that the lab results have come back, and indicate that upon gram staining, there were several gram - coccobacilli and short rods present in the sample. The lab also grew a culture of the offending bacteria, and found that it grew in distinctive black colonies, and had a brick-red flourescence under a wood's lamp.

Why would penicillin and tertacyclines be a poor choice for treatment of this infection?

Back 38

Resistant to tetracyclines and produces B-Lactamase.

Front 39

A 26 year old male presents with a severe infection of the lower gingiva. It is a large, ulcertain, necrotizing lesion that has formed on his lower gumline, and looks to be spreading to the upper gingiva as well. Gram staining shows gram - long, slender filaments and fusiform rods. What is the most likely culprit of this infection?

Back 39

F. nucleatum.