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39 Cards in this Set

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What are the factors that inhibit anaerobic growth?
Low Oxidation-Reduction potential (Eh = 0 to -300)

Absence of Oxygen (PO2 = 0.5% to 3%)
Where are anaerobes best suited to grow within the body?


HINT: Think Eh levels.
Periodontal pocket (-50), Dental plaques (-200), Colon (-300).
Superoxide Dismutase, Catalase, and Peroxidase are related to anaerobic bacteria in what way?
They are typically missing from the bacteria.
How would you classify most anaerobic bacteria infections?

HINT: Think gram stain.
Most of the infections are polymicrobic, so you will see several different types of bacteria on something like a gram stain.
What are some of the clinical findings that might suggest to you, the physician, that the patient has an anaerobic infection?
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
Which areas have the highest incidence of anaerobic infections, and which have the least?
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%.
How must a collection of possible anaerobic bacteria be obtained?
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)
What types of media need to be used for anaerobes?
Kanamycin-vancomycin agar
Reduced anaerobic blood agar
Thioglycalate agar
What are two characteristics of anaerobic cultures?
Must be grown in anaerobic conditions (duh)
Most are very slow growing due to using fermentation for energy.
What are some characteristics of Bacteroides fragilis?
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
What are the virulence factors associated with Bacteroides fragilis?
Capsule ~75%
Extracellular enzymes: Collagenase, hyaluronidase, etc.
No Endotoxin
What are some common infections caused by Bacteroides fragilis?
Gastrointestinal abscess
Pelvic inflammatory disease
Cellulitis (mixed infections)
What are some general characteristics of Prevotella (Bacteroides) melaninogenicus?
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
What are some infections that are typically caused by Prevotella (Bacteroides) melaninogenicus?
Oral and Brain abscesses
Lung abscesses
Female genital tract abscesses
What are the recommended treatments for B. fragilis and V. melaninogenicus?
Debridement and drainage in cellulitis and severe abscesses.
DOC is metronidazole and clindamycin (they are resistant to tetracyclines and are beta lactamase producers)
What are some general characteristics of F. nucleatum?
PHYSICAL:
Gram-neg, long slender filaments and fusiform rods.
HABITAT:
Oral cavity
Stool
What are some infections caused by F. nucleatum?
Head, neck, and chest infections
Synergizes with oral spirochetes resulting in ulcerating, necrotizing gingivitis known as Vincent's Angina, or "trench mouth".
What are some general characteristics and infections caused by Peptostreptococcus and other anaerobic streptococci?
HABITAT:
Mouth or stool
INFECTIONS:
Synergistic infections with S. aureus and Bacteroides sp.
Brain and head abscesses/infections.
General characteristics of A. israelii?
Only pathogenic actinomycete that is anaerobic
Gram + branching rods
Produce sulphus granules in abscesses and culture
What are some general characteristics of Gram + Spore-formers?
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.)
General characteristics of C. perfringens?
HABITAT:
GI tract
Soil
INFECTIONS: Cellulitis, Myonecrosis (gas gangrene)
Food Poisoning
Virulence factors of C. perfringens?
Exotoxins (12): Alpha toxin (lecithinase, phospholipaseC) degrades mammalian cell membranes
Other toxins have hemolytic, cytotoxic, and necrotic effects.
What is the typical process of disease in myonecrosis (Gas Gangrene)?
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
How is gas gangrene diagnosed in the lab?
Gram stain: Gram +, boxcar like rods
On culture, there is a distinctive double zone of hemolysis
What is the preferred treatment of gas gangrene?
For cellulitis and myonecrosis, wound must be debrided.
Penicillin + Clindamycin

For food poisoning - Self-limited, no treatment necessary.
What are the general characteristics of C. tetani?
HABITAT:
GI tract
Soil
INFECTIONS:
Tetanus
What virulence factors are present in C. tetani?
Tetanospasmin, which suppresses the release of NT GABA causing constant muscle contraction.
What are the laboratory findings associated with C. tetani?
Gram positive motile rods with terminal spores
How is C. tetani treated?
Antitoxin
Debride tissue of wound
DOC: Penicillin
Support patient
Tracheotomy
quiet, dark, external environment

PREVENTION: DTaP vaccine, with a 10 year booster.
What are some CLINICAL characteristics of C. botulinum?
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)
What are some virulence factors of C. botulinum?
potent neurotoxin of which A,B,E cause human disease. Toxin causes flaccid paralysis by blocking the release of Ach from A-motor neuron.
What are the characteristics of C. difficile?
DISEASE:
pseudomembranous colitis
What are the virulence factors of C. difficile?
Toxin A (enterotoxin) causes fluid production and mucosal damage and toxin.
B(Cytotoxin) -> kills mucosal cells
How is C. difficile diagnosed in the laboratory, and how is it treated?
Clostridium difficile toxin assay
DOC Metronidazole (vancomycin if necessary)
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?
Debridement of abscess and metronidazole/clindamycin treatment.
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?
Lung
Female genital tract
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?
Metronidazole and clindamycin
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?
Resistant to tetracyclines and produces B-Lactamase.
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?
F. nucleatum.