bacterial disease testing

Question 1

What can alter bacterial testing results?

Answer 1

improper technique, transport, transient bacteremia, abx

Question 2

What are the general culture interpretation guidelines?

Answer 2

infection considered if >10^5. Organisms found
< 10^1 usually contaminant. Pure isolate more likely causative agent than mixed flora. organism isolated known to cause disease at this site

Question 3

What is the normal flora found on the skin?

Answer 3

Staph epidermidis, *S. aureus, Micrococcus, few gram neg bacilli moist skin, Corynebacterium, Propionibacterium acnes

Question 4

What are pathogenic organisms found on the skin?

Answer 4

Streptococcus pyogenes. Pseudomonas. Proteus

Question 5

What are pathogenic organisms found in the mouth?

Answer 5

Strep pneumoniae, Strep pyogenes, Neisseria meningitidis, Haemophilus influenza, Neisseria gonorrheae

Question 6

What are pathogens found in the oropharynx?

Answer 6

Mycoplasma, Bordatella pertussis, Staph aureus,

Pseudomonas

Question 7

What is the normal flora of the conjunctiva?

Answer 7

Cornyebacterium, Neisseria, Moraxellae, Staph and Strep, Haemophilus and Parainfluenza

Question 8

What are pathogenic organisms found in the conjunctiva?

Answer 8

Pneumococcus, Pseudomonas, Strep

Question 9

What are pathogenic organisms of the GI tract?

Answer 9

Clostridium difficile, Salmonella, toxic strains E. coli, Helicobacter pylori

Question 10

What are pathogenic organisms of the urethra?

Answer 10

Chlamydia, Gonorrhea, Syphilis

Question 11

What are pathogenic organisms of the vagina?

Answer 11

Candida, trichomonas

Question 12

Describe the proper handling of a specimen?

Answer 12

Obtain specimen before antibiotics. aseptic technique. Minimize contamination by skin and mucous membranes. Collect an adequate volume and send tissue or fluid rather then a swab when possible. Label appropriately.Fill out requisition slips completely

Question 13

How should specimens be transported?

Answer 13

Notify the lab if special tests are requested for unusual pathogens. Specimens should be in sterile leak proof containers in sealed plastic bags, and should arrive within 1-2 hours of collection…if delay is unavoidable most specimens (except blood, CSF, joint fluid and cervical secretions for gonorrhea) should be refrigerated

Question 14

How long does it take to get cultures back?

Answer 14

Blood cultures: 48-96 hours. Most routine cultures (urine, throat, sputum) 24-48 hrs. Anaerobes: 48-72 hours

Question 15

Describe how to obtain a wound culture

Answer 15

Round up some pus on an applicator. Culture of specimens from the skin edge is less accurate than the suppurative material

Question 16

How should you culture an abscess/boil/furuncle?

Answer 16

Incised fluid or material swabbed with culture swab. Important to get pus/exudate from deep in the wound to avoid surface contamination

Question 17

How should you culture conjunctiva?

Answer 17

Gently swab to collect drainage. Place in appropriate container and send to lab at 25 C

Question 18

How should you culture a throat?

Answer 18

Inform lab if trying to identify N. gonorrheae (requires special medium—Thayer-Martin agar). Swab posterior pharynx and tonsils. Avoid touching any other part of the mouth‏. Send to the lab at 25 C

Question 19

When is a sputum culture not necessary?

Answer 19

most outpatient community acquired pneumonias. Management of bronchitis. management of acute exacerbations of COPD

Question 20

How do you obtain a sputum collection?

Answer 20

Obtain prior to antibiotic treatment. Have the patient rinse their mouth prior to expectoration. No food 1-2 hours prior to expectoration. Inoculation of the culture media immediately after the specimen if obtained

Question 21

What is different about atypical pneumonias sputum cultures?

Answer 21

with mycoplasma and legionella the sputum will have abundant PMNs, and few or no organism will be seen on gram stain

Question 22

What are indications for a blood culture?

Answer 22

mainly be considered in patients with temp >101 suspected of having endocarditis or other systemic pathogens, inpatients with pneumonia prior to starting abx.

Question 23

How should you obtain a blood culture?

Answer 23

Two specimens obtained from two separate sites 15 minutes apart (Total 30-40 ml blood). Clean site w/ETOH than with Betadine. Wipe bottle tops with alcohol. Go to lab immediately. Do not draw blood cultures through central lines or IV’s.

Question 24

How should you obtain a urine sample?

Answer 24

Midstream clean catch urine by patient: Need at least 1 ml. Transport at 4 C. Indwelling catheter: Disinfect port w/ alcohol and remove 5-10 ml of urine w/ needle and syringe—transfer to sterile container; 4 C. Suprapubic aspirate: at least 1 ml, at 4 C. ALWAYS Send as UA and urine C & S

Question 25

What are indicators of possible pyuria?

Answer 25

Leukocyte esterase-If positive on dipstick likely indicates pyuria. Nitrite- Indicates the presence of enerobacteriaceae. If negative but + symptoms of UTI still want urine culture

Question 26

Describe the microscopic analysis of urine?

Answer 26

Evaluation of urine sediment from a spun sample
Presence of squamous epithelial cells = contamination from genital region
Normals- RBC/WBC: 0-5 HPF, Bacteria: absent, Casts: 0-4, hyaline LPF, Crystals

Question 27

What are indications for a lumbar puncture?

Answer 27

suspected subarachnoid hemorrhage, isolating organism causing meningitis or brain abscess

Question 28

How should you collect CSF from a lumbar puncture?

Answer 28

collect 1-5ml of CSF. Transport at 25 degrees C. Gram stain and Bacterial culture. 4 tubes:
(1) Cell count, (2) gram stain and culture, (3) glucose & protein, (4) cell count to compare to tube 1

Question 29

Describe purposes of thoracentesis and what it can be used to test?

Answer 29

Therapeutic-relieves dyspnea. Diagnostic-Test the fluid for TB, fungus, CEA level (tumor marker), cytology, culture, gram stain, pH

Question 30

In general how do you obtain peritoneal, pericardial, pleural, or synovial body fluids?

Answer 30

Aspirate using sterile technique into sterile syringe.

Remove needle and cap syringe to send to lab. Minimum of 1-10cc at 4 degrees C

Question 31

When should you swab genital tract in women?

Answer 31

the cervix for gonorrhea, chlamydia as well as other organisms in suspected PID. Swabs of the urethra or urine testing for chlamydia

Question 32

What are instructions for a vaginal/cervical culture?

Answer 32

No douching or tub bathing for 24 hrs prior to collection

Question 33

When would you use a wet mount?

Answer 33

Helpful in evaluating vaginitis: Saline wet mount of vaginal discharge can show epithelial cells covered with bacteria suggestive of bacterial vaginosis, Trichomonas. Can reveal multiple PMN’s. KOH (potassium hydroxide) wet mount can reveal candida organisms

Question 34

How would you evaluate the urethra of men?

Answer 34

Special smaller swabs for urethral sampling for gonorrhea and chlamydia. Urine samples for GC and chlamydia for nucleic acid amplification. Nucleic acid amplification more sensitive then culture

Question 35

Describe an urethral culture?

Answer 35

Usually on men. Rapid enzyme test available. Thayer martin/new York media. Anaerobic transport

Question 36

What are indications for a stool culture?

Answer 36

for those with prolonged diarrhea who haven’t been on antibiotics or hospitalized: >2 grams; 4 C. Test of choice for those who develop diarrhea on antibiotics or in hospital > 3 days: need > 5 ml; 4 degrees C

Question 37

What are you checking for with stool cultures?

Answer 37

ova & parasites. Usually look for Staph.,Salmonella, shigella, c.difficile.