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Infectious Disease > Bacterial Disease Testing > Flashcards

Bacterial Disease Testing Flashcards

1
Q

Cultures are performed for a variety of reasons.

7

A
  1. Confirm a diagnosis
  2. Exclude a diagnosis
  3. Screening
  4. Monitor the course of a disease
  5. Monitor response to therapy
  6. Stage the severity of the disease
  7. Provide a prognosis
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2
Q

As a general rule infection considered if how many organisms are found?

Anything less than what is contaminated?

What are you counting?

A

> 10^5 Organisms found

> 10^1

organisms found

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3
Q

Whats a more common causitive agent, pure isolate or mixed flora?

A

pure isolate

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4
Q

What question do we want to ask when we treat?

2

A
  1. Is the organism isolated known to cause disease at this site?
  2. Special considerations for immunocompromised
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5
Q

How long does it take to gro the organism and identify it?

A preliminary report for most cultures is usually issued when?

A
  1. 1 full day to grow the organism and then
  2. part or all of 1 day to identify it.

It may take an additional day to isolate it before identification if there is a mixture of organisms.

A preliminary report for most cultures may be issued in 24 hours

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6
Q

Normal flora of the skin?

6

A
  1. Staph epidermidis,
  2. S. aureus,
  3. Micrococcus,
  4. few gram neg bacilli moist skin, 5. Corynebacterium,
  5. Propionibacterium acnes
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7
Q

Pathogenic bacteria of the skin?

3

A

Streptococcus pyogenes
Pseudomonas
Proteus

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8
Q

Pathogenic bacteria of the mouth?

5

A
  1. Strep pneumoniae,
  2. Strep pyogenes,
  3. Neisseria meningitidis,
  4. Haemophilus influenza,
  5. Neisseria gonorrheae
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9
Q

Potential pathogens of the oropharynx?
2

Definite pathogens of the oropharynx?
2

A

Potential pathogens
1. Mycoplasma,
2. Bordatella pertussis,
many others

Pathogens:

  1. Staph aureus
  2. Pseudomonas
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10
Q

NOrmal flora of the conjunctiva? 4

Pathogenic bacteria of the conjunctiva?3

A
  1. Cornyebacterium,
  2. Neisseria,
  3. Moraxellae,
  4. Staph and Strep,

occasional Haemophilus and Parainfluenza

Pathogens:
Pneumococcus
Pseudomonas
Strep

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11
Q

Pathogenic bacteria of the GI tract?

4

A
  1. Clostridium difficile,
  2. Salmonella,
  3. toxic strains E. coli,
  4. Helicobacter pylori (in duodenum)
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12
Q

Pathogenic bacteria of the Anterior Urethra

3

A

Pathogens

Chlamydia, Gonorrhea, Syphilis

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13
Q

Pathogenic bacteria of the Vagina?

2

A

Pathogens:
Candida, trichomonas

Losing normal flora and allowing these to grow

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14
Q

Should we obtain a specimen/culture before or after antibiotics are administered?

A

before!

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15
Q

When should pathogens arrive at the lab after collection?

A

1-2 hours after collection

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16
Q

What lab samples should not be refrigerated?

4

A

except

  1. blood,
  2. CSF,
  3. joint fluid and
  4. cervical secretions for gonorrhea
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17
Q

Culture Turnaround Times:

Blood cultures?
Most routine cultures (urine, throat, sputum)?
Anaerobes?

A
  1. Blood cultures: 48-96 hours
  2. Most routine cultures (urine, throat, sputum) 24-48 hrs; unless looking for unusual bacteria
  3. Anaerobes: can take 48-72 hours
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18
Q

What test are we getting almost everytime we are culturing a bacteria?

A

Gram stain

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19
Q

What is our routine culture media?

A

blood agar

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20
Q

What kind of culture medium do gram negatives like GC and Haemophilus sp. grow on?

What should we remember about anaerobic blood agar?

What does fungi grow on?

A

Chocolate agar

Needs to be fresh

Sabourad agar

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21
Q

What is a gram positive selective media - allows isolation of strep ; staph ; inhibits most gram neg. rods?

A

GPS

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22
Q

Anaerobic gram negative rods grow on what kind of agar? 2

What is a liquid media, enrichment broth used as a supplement to plated media?

A

MacConkey or eosin methylene blue agars

Thioglycollate media

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23
Q

What is usually present in a Wound Culture?

A

pus

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24
Q

What area should we culture for a wound? (whats most accurate?)

A

Culture of specimens from the skin edge is less accurate than culturing the suppurative material

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25
Q

When we are culturing an Abscess/boil/furuncle what is the process and where do we need to culture it?
2

A
  1. Incised and any fluid or material swabbed with culture swab and sent to lab
  2. Important to get pus/exudate from deep in the wound to avoid surface contamination

Must incise and get deep into the wound

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26
Q

Describe the process of collecting a culture from the eye-conjuctiva?

(at what temperature should we send the eye culture to the lab?)

A

Gently swab to collect drainage

Place in appropriate container and send to lab at 25 degrees C

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27
Q

Throat cultures are generally obtained to rule out what?

A

strep pharyngitis (GABS).

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28
Q

For throat cultures you need to tell the lab if you are look for a different kind of bacteria like N. Gonnorhea. What does that need to grow on?

A

Thayer-Martin agar

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29
Q

What area of the throat do we swab?

What temp do we send it to the lab at?

A

Swab posterior pharynx and tonsils (if present)
Avoid touching any other part of the mouth

25 degree C

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30
Q

Sputum culture indications

2

A
  1. Hospital-acquired pneumonia (HAP)
  2. Hospitalized patients with pneumonia (CAP) and any of the following criteria:
    - ICU admission
    - Failure of outpatient antibiotic therapy
    - Cavitary lesion
    - Active alcohol use
    - Severe obstructive of structural lung disease
    - Positive urine antigen test for Pneumococcus
    - Positive urine antigen test for Legionella
    - Pleural effusion
31
Q

Sputum cultures are NOT indicated in the following?

3

A
  1. For most outpatient community acquired pneumonias
  2. Management of bronchitis
  3. Initial management of acute exacerbations of COPD
32
Q

Describe the process for sputum collection for optimal yield?
4

A
  1. Obtain prior to antibiotic treatment
  2. Have the patient rinse their mouth prior to expectoration
  3. No food 1-2 hours prior to expectoration
  4. Inoculation of the culture media immediately after the specimen if obtained or immediately after prompt transport to the microbiology lab
33
Q

What is a sampling of the lower airway is another potential diagnostic method in patients w/ suspected pneumonia?

A

Bronchoscopy-

34
Q

What would make a sputum culture inaccurate?

A

mouth flora

35
Q

What would make us suspect a pathogen in a sputum culture?

2

A

Suspect a pathogen if

  1. WBC’s are present along with
  2. an overabundance of one type of organism
36
Q

Sputum of what time of day will represent ‘deeper’ pulmonary secretions?

A

First morning sputum

37
Q

How can we induce a cough to get a sputum culture?

4

A
  1. Induce cough with nebulizers,
  2. pulmonary PT,
  3. aspiration,
  4. bronchoscopy
38
Q

What do we always need to get with a sputum sample?

A

Always get a gram stain with the sputum sample

Helpful for directing empiric therapy

39
Q

IN what kind of disease/bacteria will the sputum contain abundant polymorphonuclear cells and few or no organism will be seen on gram stain?
3

A

Atypical pneumonias (mycoplasma and legionella)

40
Q

Blood culture indications

5

A
  1. Bacteremia
  2. Septicemia
  3. Unexplained post operative shock
  4. Unexplained fever of several days duration
  5. Pneumonia
41
Q

Blood culture indications with a pt with chills and fever?

4

A
  1. Infected burns or UTIs
  2. Rapidly progressing tissue infections
  3. Postoperative wound sepsis
  4. Indwelling venous or arterial catheters
42
Q

Blood culture indications in debilitated patients receiving what?
4

A

antibiotics
corticosteroids
Immunosuppressives
parenteral hyperalimentation

43
Q

Blood cultures used to detect bacteremia and septicemia should mainly be considered in pts with a temp of what?

A

over 101

44
Q

Standard of care for inpatients with pneumonia prior to starting antibiotics is what?

When and Why would we repeat the culture?

A

blood culture

Can repeat in 1 hour or if fever
Transient bacteremia

45
Q

Two specimens obtained from two separate sites 15 minutes apart in blood cultures. Why do we do this?

How much blood should we draw?

A
  1. # Of organisms per site is low
  2. Helps identify contaminants

Total 30-40 ml blood

46
Q

Blood culture technique?
4

What can we not draw cultures through?

A
  1. Clean site first with 70% alcohol
  2. Follow with Betadine x 2 minutes (follow facility protocol)
  3. Wipe bottle tops with alcohol
  4. Go to lab immediately

Do not draw blood cultures through central lines or IV’s (contamination)

47
Q

Which ways can we obtain Urine Cultures?
3

How much should we collect?

At the very minimum?

What temp should we transport it at?

Is this different for a straight cath?

Is this different for an indwelling cath?

A

Clean catch, mid void specimen
Catheterization
Suprapubic tap

Collect 5-50ml of urine

1 mL

4 degress C

yes

no

48
Q

Whats the technique for an indwelling catheter?
3

(how much and at what temp)

A
  1. Disinfect port w/ alcohol
  2. Remove 5-10 ml of urine w/ needle and syringe—transfer to sterile container;
  3. 4 C
49
Q

What is the best time to get a uriine sample?

A

first urination of the day

50
Q

What do we always send the specimen to the lab as?

2

A

ALWAYS Send as UA and urine C and S

51
Q

Urine dipstick testing
can test what things?
9

A 
pH
Specific gravity
Bilirubin
Protein  
Glucose
Ketones
Blood
Nitrite
Leukocyte esterase
52
Q

Indicators of possible pyuria

2

A

Leukocyte esterase

Nitrite

53
Q

Leukocyte esterase will indicate pyuria if what?

Nitrite will indicate pyuria if what?

If thses are negative but you have positive symptoms what should you do?

A
  • If positive on dipstick likely indicates pyuria
  • Indicates the presence of enerobacteriaceae that converts nitrate to nitrite

If negative but + symptoms of UTI still want urine culture
(GET A UA)

54
Q

What is a Microscopic analysis of urine looking at?
(how do we know if they specimen is contaminated?)

What are the normal values for a microscopic analysis of urine?
RBC:
WBC:
Bacteria:
Casts:
Crystals:
A

Presence of squamous epithelial cells = contamination from genital region

Evaluation of urine sediment from a spun sample

Normals
RBC: 0-5 HPF
WBC: 0-5 HPF
Bacteria: absent
Casts: 0-4 hyaline LPF
Crystals
55
Q

Lumbar puncture indications

2

A
  1. Look for blood (possible subarachnoid hemorrhage)

2. Find the organism causing the meningitis or brain abscess

56
Q

What can we do in the mean time while awaiting lumbar puncture results and why do we do this?

A

Can do gram stain early on while awaiting culture reports

Cell & chemistry counts will aid in making the diagnosis

57
Q

When do we want to test Cerebrospinal Fluid (CSF)‏?
2

How much should we collect in a lumbar puncture?

At what temp should we transport it at?

What should we do with the lumbar puncture?
2

A
  1. Suspected meningitis,
  2. high fever in infant

Lumbar puncture collect 1-5ml of CSF

Transport at 25 degrees C

Gram stain and Bacterial culture

58
Q

There is four tubes to fill in a lumbar puncture for CSF. What is in each one?

A

4 tubes

(1) Cell count,
(2) glucose & protein,
(3) gram stain & culture,
(4) cell count to compare to tube 1

59
Q

Thoracentesis can be done for two reasons. What are they?

A
  1. Diagnostic and/or therapeutic
    - Therapeutic-relieves dyspnea
  2. Diagnostic
    - Test the fluid
60
Q

What are we looking at in the fluid acquired from a thoracentesis?
7

A 
TB,
fungus, 
CEA level (tumor marker), cytology, 
culture, 
gram stain, 
pH
61
Q

When is a Synovial Fluid evaluation done?4

What should not be administered at the same time this is done?

A
  1. Swollen joint
  2. Infection,
  3. inflammation or
  4. crystals (gouty arthritis)

Medications should not be administered therapeutically at the same time!

62
Q

What body fluids might we want to culture?
4

What would we usually expect to see if we wanted to culture these fluids?

Whats the minimum amount we want to send and at what temp?

A

Peritoneal, pericardial, pleural, synovial

usually patient has fever or elevated WBCs

Minimum of 1-10cc, send as much fluid as possible
Send at 4 degrees C

63
Q

What do we swab the cervix for? (if we want to test for what diseases)
3

Swabs of the urethra or urine testing for what?

A

Swabs of the cervix for

  1. gonorrhea,
  2. chlamydia as well as other organisms in suspected
  3. Pelvic Inflammatory Disease

chlamydia

64
Q

What should not be done for 24 hours prior to a vaginal/cervical collection?

A

No douching or tub bathing for 24 hrs prior to collection

65
Q

What kind of test is good for evaluating vaginitis?

What kind of bacteria are we expecting to be here?

A

Wet mount

anaerobic (Flagyl)

66
Q

Saline wet mount of vaginal of discharge can show what?

What diseases is this helpful is diagnosing? 2

What do we put on the wet mount?

What organisms can it reveal?

A

epithelial cells covered with bacteria suggestive of bacterial vaginosis

Trichomonads
Can reveal multiple PMN’s

KOH (potassium hydroxide) wet mount can reveal candida organisms

67
Q

What do we test with in men for gonorrhea and chlamydia and other less common infectious agents ?

A

Special smaller swabs for urethral sampling

68
Q

Why do we use urine samples now instead for diagnosis of GC and chlamydia in men?

A

Urine samples for GC and chlamydia for nucleic acid amplification
Nucleic acid amplification more sensitive then culture

69
Q

Urethral Culture in men what medium would we use?

A

Thayer martin/new York media

70
Q

What pts is a stool sample a routine culture for?

How much should we get at what degree should transport it at?

A

(for those with prolonged diarrhea or haven’t been on antibiotics or hospitalized)‏

> 2 grams; 4 degrees C

71
Q

Test of choice for those who develop diarrhea on antibiotics or in hospital > 3 days?

How much should we get and at what degree should we transport it at?

A

C. difficile toxin

> 5 ml; 4 degrees C

72
Q

What bacteria are we usually looking for with stool culture?

What do we also need to look for/rule out?

A

Usually look for Staph.,Salmonella, shigella

Also check for ova & parasites

73
Q

Whats a big no no with stool cultures??

A

Dont mix with urine or TP!

Infectious Disease (29 decks)

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