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MLS Microbiology > Blood Cultures - Exam 9 > Flashcards

Blood Cultures - Exam 9 Flashcards

1
Q

Define bacteremia

A

The presence of bacteria in the blood.

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2
Q

Define fungemia

A

The presence of fungi in the blood.

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3
Q

Define septicemia

A

Bacteria is present in the blood, causing infection and reproducing within the bloodstream.

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4
Q

What are the three types of bacteremia?

A

Transient, intermittent and continuous

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5
Q

What type of bacteremia is described?

Organisms comprising of normal flora are introduced into the blood.

A

Transient bacteremia

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6
Q

What type of bacteremia is described?
Organisms are released into the blood at a fairly constant rate and are continuously present in the blood with or without symptoms.

A

Continuous bacteremia

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7
Q

What type of bacteremia is described?

Bacteria from an un-drained infected site are released into the blood spasmodically.

A

Intermittent bacteremia

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8
Q

When does septicemia occur?

A

When bacteria and their toxins multiply - often at rates that exceed removal by phagocytosis.

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9
Q

The following are symptoms of what?

Fever, chills, malaise, tachycardia, hyperventilation, and toxicity

A

Septicemia

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10
Q

What are the four major groups of microbes found circulating in blood during disease?

A

Bacteria, fungi, parasites, and viruses

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11
Q

What are the two types of fungus most often seen circulating in the blood during disease?

A

C. albicans (account for 8-10% of all nosocomial bloodstream infections.

Malassezia furfur (seen in patients receiving lipid supplements/ most often neonates)

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12
Q

What are the three viruses most often seen circulating in the blood during disease?

A 
Epstein Barr (invades lymphs), 
CMV (invades lymphs, monocytes, and PMNs), and HIV (invades certain T-lymphs)
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13
Q

What are the four most common parasites found circulating in the blood during disease?

A

Plasmodium, Trypanosoma, Babesia, and Microfilariae (Loa Loa, Brugia, and Wuchereria)

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14
Q

When is the ideal time to collect a blood culture?

A

30-45 min before a temperature spike

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15
Q

What is acute febrile illness?

A

Rapid onset fever along with symptoms, can be caused by a wide range of pathogens

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16
Q

What is empiric antibiotic therapy?

A

Antibiotic therapy given within the first 24 hours of admission

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17
Q

When might empiric antibiotic therapy be indicated?

A

When a patient has an acute febrile illness

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18
Q

What are two of the main diseases that may cause acute febrile illness?

A

Meningitis and bacterial pneumonia

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19
Q

What are two instances where emergency surgery may be necessary for a patient suffering from acute febrile illness?

A

If the patient has suppurative arthritis or osteomyelitis

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20
Q

Why do you need extra sets of blood culture bottles when treating a patient with fever of unknown origin?

A

To ensure that you are detecting the infectious agent and not a contaminant from equipment or natural body flora

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21
Q

In the case of a fever with an unknown origin, how many blood cultures should be drawn initially and what is the interval between sets?

A

2 blood cultures should be drawn initially with an interval of 45-60 minutes, 2 additional sets can be then drawn 24-48 hours later

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22
Q

What are interval draws used for?

A

To aid in determining if a continuous or intermittent seeding of the blood exists

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23
Q

In the case of infective endocarditis, how many blood cultures should be drawn initially and in what time frame?

A

3 blood cultures in the first 1-2 hours of evaluation (3 separate venipunctures - should be done before therapy begins)

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24
Q

In the case of infective bacterial endocarditis, how many blood cultures should be drawn and in what time frame? What do you do if those are negative?

A

3 blood cultures within the first 24 hours, with 30 minutes between each

Obtain 2 more sets on subsequent days

25
Q

What are the 5 groups of bacteria that may be a common cause infective endocarditis?

A
  • Viridans Strep (normal oral flora - gains entry through gingivitis, periodontitis and dental manipulation)
  • Nutritionally Variant Strep
  • HACEK group
  • Enterococcus
  • S. aureus (most common cause of infective endocarditis)
26
Q

Who is at a higher risk of having infective endocarditis from the Viridans Strep group?

A

IV drug users because of the use of spit to “clean” the injection site

27
Q

What are the 4 groups of bacteria commonly associated with IV catheter bacteremia?

A
  • S. epidermidis (produces biofilm made of complex sugars that adhere to catheter surface)
  • Other Coag Neg Staph
  • S. aureus
  • Enterobacteriaceae
28
Q

Bacteremia from extravascular sites of infection can come from…

A

Wounds, soft tissue, respiratory, CSF, and GU tract

29
Q

Which organisms are the common cause of bacteremia from a wound infection?

A

Anaerobes, P. aeruginosa, and Group A Strep

30
Q

Which organisms are the common cause of bacteremia from a soft tissue infection?

A

Anaerobes, Coag Negative Staph, P. aeruginosa, Group A Strep, and S. aureus

31
Q

Which organisms are the common cause of bacteremia from a respiratory infection?

A

H. flu and S. pneumoniae

32
Q

Which organisms are the common cause of bacteremia from a CSF infection?

A

H. flu, Listeria, N. meningitidis, S. pneumoniae, and S. aureus

33
Q

Which organisms are the common cause of bacteremia from a GU tract infection?

A

Enterobacteriaceae, and C. albicans

34
Q

What is the hospital standard for contamination rates?

A

3%

35
Q

How do you sterilize a venipuncture site for blood culture collection?

A

Cleanse with Chloroprep in a concentric fashion for 30 seconds and do not touch the skin after (even with gloves )

36
Q

What is the recommended volume for an adult blood culture bottle?

A

8-10 mL per bottle (percentage yield of positive culture drops if less than 10 mL per bottle is obtained)

37
Q

What is the recommended volume for each blood culture bottle for child?

A

1-5 mL proves to be satisfactory

38
Q

Which bottle should be drawn first if there is a difficult person to draw?

A

The aerobic bottle

39
Q

What is the ratio for ideal recovery?

A

1:10

40
Q

What does Trypticase soy broth/Brain heart infusion broth contain? What type of bacteria is this media good for?

A

Soybean and casein digests - good for aerobic bacteria

41
Q

What kind of organisms is Thioglycolate broth most ideal for?

A

Anaerobic bacteria

42
Q

What is Sodium Polyanetholsulfonate (SPS) media good for?

A

Preventing coagulation without harming the bacteria, inactivating neutrophils and certain antibiotics, and inhibiting the growth of certain bacteria.

43
Q

What types of bacteria does SPS inhibit?

A

P. aeruginosa, GC, N. meningitidis, and G. vaginalis

44
Q

What organism is Castaneda double medium good for recovering?

A

Brucella

45
Q

What is the biphasic technique, what are the conditions for incubation?

A

When the blood culture bottle contains both solid and liquid media.

Needs to be incubated in 5-10% CO2 @ 35-37C for 30 days and tipped every 48 hours to inoculate agar surface, also needs to be subcultured at least twice a week.

46
Q

What is Fletchers medium and what organisms is it good for recovering?

A

Semi-solid media with rabbit serum and SPS.

It is good for recovering Leptospira.

47
Q

What are the incubation conditions for Fletchers medium, how and when is it examined?

A

Incubated in the dark @30C for 28 days. Examined weekly by darkfield microscopy

48
Q

What are the incubation conditions for blood culture bottles?

A

Incubated @35C and held for 5 days

49
Q

What should be done immediately if a blood culture bottle is suspected to be positive?

A

A Gram stain and a follow up with the provider if the Gram stain is positive

50
Q

What are the three ways blood culture bottles are examined?

A

Macroscopically, radiometrically, and fluorometrically

51
Q

What are the three blood culture systems we should be familiar with?

A

BACTEC FX, ISOLATOR, and SEPTI-CHEK

52
Q

What are the common macroscopic observations of Gram Negative Bacilli in blood culture bottles (usually Enterics)?

A

Medium above red cell layer becomes turbid and gas bubbles are present

53
Q

What are the common macroscopic observations of Pneumococcus and Meningococcus in blood culture bottles?

A

Turbidity and a greenish tint to the medium

54
Q

What are the common macroscopic observations of Streptococcus in thioglycolate media?

A

Strep appears as cotton ball colonies on top of the sedimented red cells

55
Q

What are the common macroscopic observations of Staphylococcus in blood culture?

A

Staph frequently produces a large jelly-like coagulum and appears turbid

56
Q

What are the common macroscopic observations of Bacillus in blood culture?

A

Lysed RBCs and a thick film on the surface

57
Q

What are the common macroscopic observations of Clostridium in blood culture?

A

Produces a large head of has and lysed RBCs

58
Q

What are the common macroscopic observations of Bacteroides in blood culture?

A

Less gas than Clostridium and a foul odor

59
Q

What are the common macroscopic observations of H. flu in blood culture?

A

Little or no change in the media

MLS Microbiology (15 decks)

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