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Clinical Microbiology (Exam 3) > Anaerobes (Exam #) > Flashcards

Anaerobes (Exam #) Flashcards

1
Q

Are anaerobes gram + or - ?

A

a mixture of both

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2
Q

What does aerotolerant mean?

A

anaerobic bacteria not killed by small amounts of air (5%)

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3
Q

What two anaerobic species are known to be aerotolerant?

A

Clostridium spp. and Actinomyces spp.

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4
Q

How long does it take for obligate anaerobes to die when exposed to oxygen?

A

As little as 10 minutes

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5
Q

What enzymes do anaerobic bacteria lack?

A

superoxide dismutase and catalase, enzymes required to break down reactive oxygen during aerobic metabolism, which is harmful to bacteria

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6
Q

obligate aerobes

A

grow well in 21% o2 and 0.3% co2 aka ambient air

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7
Q

obligate anaerobes

A

grow only in or near 0% o2 levels, 5-10% hydrogen and co2, and 80%-90% nitrogen

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8
Q

microaerophiles

A

only grow under reduced 02 levels 5-10%, and co2 8-10%

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9
Q

facultative anaerobe

A

can grow under aerobic or anaerobic conditions, potential skin flora. Will respire aerobically until oxygen is depleted then ferment.

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10
Q

Capnophile

A

likes increased co2 5-10%, and 15% o2. Is accomplished in our lab via candle jar

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11
Q

What is the most abundant bacteria in the GI tract?

A

anaerobes, and the number of bacteria increase as you move distally.

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12
Q

what is the most abundant bacteria in the human colon and why is this important?

A

Bacteriodes spp., they break down food products into forms our bodies can use and also break down dietary carcinogens.

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13
Q

Are clostridia normal flora?

A

yes, of the GI and skin

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14
Q

What additional anaerobes are normal flora of the skin and/or upper respiratory tract?

A

propionibacterium, prevotella, and fusobacterium

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15
Q

What bacteria is normal flora of the female genital tract and in rare cases pathogenic?

A

Lactobacillus, microaerophillic, gram positive thin rods with spiral forms. Catalase negative. can be pinpoint on SBAP as well as aplha hemolytic like streptococci.

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16
Q

What are the disease transmission types of anaerobes?

A
  • endogenous infections- opportunistic infections, pathogens gain access to sterile sites (Trauma)
  • exogenous sources- rusty nails, skin puncture
  • ingestion of improperly canned foods (botulism)
  • human to human spread (C. Diff)
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17
Q

Are anaerobe infections common in urine?

A
  • Very rarely urine, only 1% of isolates isolated from urines are anaerobes.
  • Voided or catheterized urine not acceptable (normal flora contaminants).
  • Suprapubic bladder aspirate is acceptable.
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18
Q

What are preferred anaerobe specimens?

A
  • Specimens that limit the amount of normal flora contamination are preferred e.g. aspirates, tissue, blood.
  • Acceptable specimens include aspirated material or tissue biopsy.
  • Needle aspiration preferred over swabs
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19
Q

What are the disadvantages of swabs?

A
  • small amount
  • drying
  • toxic exposure to air
  • normal flora contamination
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20
Q

What should blood collection sites be sanitized with?

A

with iodine or clorhexidine gluconate in combo with 70% isopropyl alcohol

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21
Q

How should anaerobe specimens be transported?

A
  • Anaerobes causing infection often come from warm, moist (humid) areas in the body, thus need to create artificial conditions mimicking this to avoid shocking them.
  • Tissue needs to be placed in anaerobic transport tubes or vials containing Pre-reduced anaerobically sterilized (PRAS) media to keep tissue moist.
  • Specimens should be held at room temperature.
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22
Q

What are the common anaerobe containers?

A

*Anaerobe Jars or Pouches e.g. Gas-Pak by BD
Clear, heavy plastic jar with air tight seal (clamp-lid)
*Pouch systems also available commercially with all necessary agents.
*Holding Jars
*Anaerobe Chambers (Glove boxes)

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23
Q

How do you know you are creating an anaerobic environment using a gas-pak and jar?

A

Heat will be produced and condensation will collect on walls of jar, indicates you are achieving proper conditions, takes ~ 30 minutes.

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24
Q

What media should anaerobes be plated to?

A

Typically always plate an anaerobic blood agar and one or all of the following PRAS media:

  • Anaerobic Phenylethyl alcohol agar (PEA)
  • Kanamycin-vancomycin laked blood (KVLB)
  • Kanamycin-vancomycin blood agar
  • Bacteroides bile-esculin agar (BBE)
  • Thioglycollate broth
25
Should suspected anaerobe infections be plated to aerobic media?
t ypically also plate AEROBIC SBAP, chocolate and MacConkey as most anaerobic infections are POLYMICROBIC and can include aerobic or facultative anaerobic bacteria
26
What should anaerobic media be supplemented with?
* hemin * blood * vitamin K * sodium bicarbonate
27
What is the name of the common media type used for anaerobes?
Pre-Reduced, Anaerobically Sterilized (PRAS) media
28
What's in an anaerobic BAP?
* yeast * hemin * cysteine * vitamin K
29
What's in Kanamycin-vancomycin laked blood/blood agar?
*Selective for gram negative obligate anaerobes (preferred media for these specific bacteria). Specifically Prevotella and Bacteroides spp. * Vancomycin inhibits growth of all gram positive organisms (both aerobic and anaerobic) * Kanamycin inhibits growth of gram negative, facultative anaerobic bacilli * laked blood helps pigment production by prevotella melaninogenica
30
What is the antibiotic in bacteriodes bile esculin agar?
gentamicin- inhibits facultative anaerobes and most gram negative anaerobes
31
Should you gram stain suspected anaerobic bacteria?
all species should be gram stained, may be polymicrobial or show things such as epithelial cells etc that can help with media selection or narrowing of possible organuisms.
32
What are the clues that anaerobic bacteria are present?
* Foul odor upon opening a anaerobic jar or bag e.g. metabolic end-products from C. difficile, Fusobacterium are fetid. * Colonies present on anaerobic media, but not on non-anaerobically incubated/prepared media.
33
How is bacteriodes fragilis group id'ed?
* gram negative rods * bile esculin positive * Resistant to vancomycin, penicillin, kanamycin, and typically colistin. * Growth on BBE agar (blackening)
34
porphyromonas
* gram negative rod * pigmented- bright red fluorescence under UV * asacchrolytic * normal flora of oral cavity * more commonly cause infections of head region
35
prevotella melaninogenica
* gram negative rods * normal flora of oral cavity, respiratory, GI, and genitourinary tracts * opportunistic pathogen * Pigmented and non pigmented strains- black pigment on laked blood agar after several days, brick-red fluorescence under UV * ferments carbs, distinguishes it from porphyromonas
36
fusobacterium spp.
* Gram negative rods * slightly curved appearance on gram stain * normal flora of oral cavity * infections above the thorax typically
37
Clostridium spp.
* gram positive bacilli * endospore forming * catalase negative * obligately anaerobic, some aerotolerant * many species normal flora of the gut, female GI tract, and oral mucosa.
38
why is clostridium good at causing disease?
* Ubiquitous in nature. * Spores allow them to survive harsh environmental conditions. * Can rapidly proliferate in nutrient rich, oxygen deprived environments. * Produce various toxins (enterotoxins, neurotoxins).
39
What do clostridium botulinum look like?
Spores are subterminal, bacteria resemble a tennis racket as seen in an endospore stain.
40
What are the botulism groups and which cause disease in humans?
Groups I and II cause human botulism, Group III animal botulism, Group IV not typically associated with disease.
41
What virulence factors do C.Botulinum have?
* Neurotoxin causing flaccid paralysis. | * 7 types of toxin exist A-G; A, B E and F types cause human disease
42
What are the 4 forms of botulism?
* foodborne -canned foods * infant- associated with honey consumption * wound– this is the only form that antibiotics are typically used as treatment. Antibiotics may hasten release of toxin thus contraindicated in non-wound botulism. * inhalation- seen in bioterrorism
43
What is the pathogenesis of botulism?
enters the body through GI tract or mucous membranes, makes its way to bloodstream and/or lymphatics until it reaches neuromuscular junctions blocking neurotransmitter release. Can lead to paralysis and death via respiratory failure.
44
foodborne botulism
* symptoms can begin in 6 hours but typically 18-36 hours after ingestion of pre-formed toxin. * treat with ventilation and antitoxin * recovery can take months to years, nerve endings have to regrow * 3-5% mortality rate * Toxin can be inactivated by boiling
45
how is foodborne botulism identified?
* Not included on the Vitek 2 ANC card. * Specimens can include: serum, gastric contents, feces, food * ELISA * Molecular Techniques * Mouse Bioassay for ID of botulinum toxin
46
infant botulism
* neurotoxin production in vivo * bacteria colonize GI mucosa * treatment is high support care- nutrition and respiratory functions
47
C. Tetani
* spore are oval with terminal or subterminal locations * looks like a drumstick or tennis racket on gram stain * narrow zone of beta hemolysis on anaerobic blood agar plates and may swarm * DTaP vaccine * difficult to identify without good H and P
48
C. perfringens
* found in soil and water, some are normal flora, can also be found on kitchen counters * produce 12 different toxins * double zone of hemolysis on anaerobic blood agar * Strains producing C. perfringens enterotoxin (CPE), third most common cause of bacterial food poisoning in U.S. * alpha hemolysis due to alpha toxin and lecithinase activity
49
What types of infections do C. Perfringens cause?
Soft tissue infections * Cellulitis * Myonecrosis (Gas gangrene), high mortality rate) * Food poisoning (meat products) * Enteritis necroticans
50
How is C. Perfringens identified?
* feces needs to be sent to public health lab for confirmation of ID at 4 degrees C * round, subterminal spores * reverse CAMP positive * VITEK 2 ANC card * molecular studies
51
What are the two toxins C.Diff produces?
* Enterotoxin, causes inflammation of intestinal mucosa | * Cytotoxin- causes cellular death
52
How should C.Diff cultures be?
* Stool cultures should be watery, not formed, to distinguish infection from colonization. * Emit a horse stable odor on blood agar * cycloserine-cefoxitin-fructose agar (CCFA)- Egg yolk based selective for C. diff creates yellow ground glass colonies. Others may grow but do not produce a yellow color change.
53
How is C.Diff identified?
* Culture then automation (Vitek 2 ANC card) * Agglutination tests for Ag detection * Enzyme immunoassays for toxin A, B or both * Molecular
54
Actinomyces israelii
*normal flora of the mouth, gums, teeth, entry via injured oral mucosa *gram positive rods, non-spore forming *fungus-like bacteria *produce hyphal strands *molar tooth appearance on agar *
55
what disease does actinomyces cause?
* Chronic infection with local abscesses with formation of oozing sinus tracts containing sulfur granules * Gain entry to deeper tissues via injury, more common in males
56
peptostreptococcus anaerobius
*gram positive coccobaccilus, often in chains *normal flora *Can cause endocarditis, infection of GU and GI tracts. Also implicated in periodontal disease, gingivitis.
57
peptococcus niger
* gram positive cocci in pairs, tetrads * normal flora, not usually disease causing * Produce tiny black, convex, smooth colonies on anaerobic BAP which turn light gray if exposed to air.
58
Veilonella Paruvula
* Gram negative, diplococci in pairs, clusters and/or short chains. * Normal flora of human mouth, GI tracts. * Can cause infection in sinuses, lung, heart, bone and CNS. * Produce a red fluorescence under UV light. * Has been found to create a biofilm along with Streptococcus mutans (normal flora of the mouth) that in combination imparts greater resistance to S. mutans to various antimicrobials.

Clinical Microbiology (Exam 3) (4 decks)

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