Bacterial Culture
Testing
Schedule:
0700-2200, 7 days a week, including holidays.
Comments:
Deliver all specimens to the laboratory as soon as possible after
collection. Gram stains are automatically performed on fluids and
exudates other than blood and urine. Do not send sterile body fluids
in plastic red top tubes. These tubes contain a clot activator which
may affect testing. Therefore, tests may be unreliable.
Label transport tube with two patient identifiers, date and time of
collection.
Transport at room temperature unless otherwise specified.
A. Abscess - Tissue or aspirates are always superior to swab
specimens. Remove surface exudate by wiping with sterile saline or
70% alcohol. Aspirate with needle and syringe. Cleanse rubber
stopper of anaerobic transport vial (59546) with alcohol; allow to
dry 1 min before inoculating; push needle through septum and inject
all abscess material on top of agar. If a swab must be used, pass
the swab deep into the base of the lesion to firmly sample the fresh
border. Transport time ≤2 hours.
B. Anaerobic cultures - Tissue or aspirates are preferred rather
than swabs. Fluid collections should be aspirated through disinfected
tissue or skin. For superficial ulcers, collect material from below
the surface (after surface debridement or use a needle and syringe).
Submit specimens using anaerobic transport media:
a. Anaerobic vial (fluid specimen, 59546): Cleanse rubber stopper
with alcohol; allow to dry 1 min before inoculation; push needle
through septum and inject specimen on top of agar.
b. Anaerobic jar (tissue specimen, 59547)
c. A sterile container (37778) may be used for tissue if transported
to the microbiology lab immediately (add drops of sterile saline
to keep small pieces of tissue moist).
d. Anaerobic swab (907464) - swab specimens are suboptimal, aspirate
preferred.
e. Deliver all specimens to the laboratory immediately after
collection.
f. Anaerobic flora is prevalent on mucosal surfaces of the oral
cavity, upper respiratory, gastrointestinal, and genital tracts;
specimens collected from these sites should not ordinarily be
cultured for anaerobic bacteria. The following is a list of
specimens that are likely to be contaminated with anaerobic
normal flora and are NOT routinely accepted for anaerobic culture.
1) Throat or nasopharyngeal swabs
2) Gingival or other intraoral surface swabs
3) Expectorated sputum
4) Sputum obtained by nasotracheal or endotracheal suction
5) Bronchial washings
6) Voided or catheterized urine
7) Vaginal or cervical swabs
8) Gastric and small bowel contents (except for "blind loop" or
bacterial overgrowth syndrome)
9) Feces (except for specific etiologic agents such as
C. difficile and C. botulinum)
10) Rectal swabs-Surface swabs from ulcers and wounds(collect
material from below the surface)
11) Material adjacent to a mucous membrane that has not been
adequately decontaminated
C. Blood
a. Adult - Cleanse skin with ChloraPrepChloraPrep®
one-step 1.5 mL Frepp®
1) Holding the applicator sponge downward, pinch wings on
applicator to break ampule and release the antiseptic.
2) Use a side-to-side motion to scrub the site with the friction
pad for a full 30 sec; allow site to dry completely (at least
30 sec) before venipuncture. Do not touch site after prep.
3) Remove overcaps from bottles (1 aerobic 924171 and 1 anaerobic
924172) and cleanse each rubber septum with separate 70%
alcohol swabs. Allow septum to dry for 1 min before
inoculating.
4) Draw 20 mL of blood and inoculate each bottle with 10 mL of
blood. Do not vent or overfill bottles. Adding low (<8 mL)
or high (>10 mL) volumes may adversely affect the recovery of
organisms. Transport time <2 h.
5) For adults with a suspected bloodstream infection (BSI),
collect two initial sets of blood cultures sequentially from
separate phlebotomy procedures followed by a third and a
fourth set at 4-6 hour intervals (will detect >99% of BSIs).
Three sets of blood cultures collected within a 24 hour
period will detect 96.9 - 98.3% of BSIs. A single set of
blood cultures to detect BSIs in adults is inadequate (only
73% sensitivity); two sets of blood cultures will allow
detection of 87.7-89.7% of BSI episodes. (J Clin Microbiol
2007;45:3546).
6) If patient is allergic to chlorhexidine, prep site with a
povidone iodine swab stick (907172) applied in concentric
circles (start at center). Allow to dry at least 1 min before
venipuncture. If patient is allergic to iodine, cleanse site
with 70% alcohol for 60 sec.
b. Pediatric - Prepare skin and bottles as for adult.
Collect as much blood as possible up to 10 mL per bottle.
D. Bone marrow aspirate - Prepare puncture site as for surgical
incision. Inoculate blood culture bottle (924171) or Isolator
(lysis centrifugation) tube (922848). Transport time <2 hours.
Routine bacterial culture of bone marrow is rarely useful.
E. Burn - Clean and debride burn. Place tissue in sterile
container (37778). Transfer aspirates to a sterile container. These
are processed for aerobic culture only. Quantitative culture may or
may not be valuable. A 3 to 4 mm punch biopsy specimen is optimum
when quantitative cultures are ordered. Cultures of surface samples
can be misleading.
F. Catheter Tips - Only intravascular catheter tips from
pediatric patients and peritoneal dialysis catheters are routinely
accepted for culture. Send 5 cm of distal tip in sterile screw-cap
container (37778). Transport time is ≤15 min. Foley catheters
are not accepted for culture since growth represents distal urethral
flora.
G. Cerebrospinal Fluid (CSF) - Aseptically collect CSF from a
lumbar puncture into sterile tubes (907131). Send second tube
(≥3 mL) to the Microbiology Laboratory. Transport time
≤15 min. Cerebrospinal fluid for bacterial culture should
never be refrigerated.
H. Decubitus ulcer - A swab is not the specimen of choice.
Cleanse surface with sterile saline. Submit tissue or aspirate
inflammatory material from the base of the ulcer in a sterile tube
or anaerobic system. Transport time is ≤2 hours.
I. Ear
a. Inner ear - Tympanocentesis should be reserved for
complicated, recurrent, or chronic persistent otitis media. For
intact eardrum, clean ear canal with soap solution and collect
fluid via syringe aspiration. Submit in sterile container. For
ruptured eardrum, collect fluid on flexible shaft swab via an
auditory speculum. Transport time <2 hours.
b. Outer ear - Use moistened swab to remove any debris or
crust from ear canal. Obtain sample by firmly rotating swab in
outer canal. For otitis externa, vigorous swabbing is required -
surface swabbing may miss streptococcal cellulitis.
J. Eye
a. Conjunctiva - Sample each eye with separate swabs
(premoistened with sterile saline) by rolling over conjunctiva.
When only one eye is infected, sampling both can help distinguish
indigenous microflora from true pathogens.
b. Corneal scrapings - Collected by ophthalmologist. Using
sterile spatula, scrape ulcers and lesions; inoculate scraping
directly onto media (BHI with 10% sheep blood, chocolate, and
inhibitory mold agar). Prepare 2 smears by rubbing material onto
1-2 cm area of slide. Transport time ≤15 min.
c. Vitreous fluid - Prepare eye for needle aspiration of
fluid. Transfer fluid to sterile tube. Transport time
≤15 min.
K. Feces - see stool.
L. Fistula - see abscess.
M. Fluids - see sterile body fluids.
N. Genital - Cultures for Neisseria gonorrhoeae should
be collected with a sterile swab and inoculated directly to a Jembec
plate (obtain from laboratory; place white tablet in hole of Jembec
plate to provide CO2 enriched atmosphere, close top of
the plate tightly and place in Ziploc bag provided, keep at room
temperature, deliver to lab as soon as possible). If a Jembec plate
is unavailable, an aerobic culturette swab (922349) may be used if
transported to laboratory immediately.
a. Endocervical - Remove cervical mucus with swab and discard.
Insert a second swab into endocervical canal and rotate against
walls. Allow time for organisms to absorb onto the swab surface.
b. Urethral - Collect urethral specimens at least 1 h after
patient has urinated. Insert small swab 2-4 cm into urethral
lumen, rotate, leave for 2s to facilitate absorption.
O. Pilonidal cyst - see abscess.
P. Respiratory, lower - Transport time is ≤2 hours.
a. Bronchoalveolar lavage or brush, endotracheal aspirate -
Collect fluid in a sputum trap (907093); transfer to leak-proof
container (37778) for transport in pneumatic tube system); place
brush in sterile container with 1 mL saline.
b. Sputum, expectorated - Patient should rinse mouth and
gargle with water prior to collection; instruct patient to cough
deeply. Collect specimens in sterile transport containers
(37778).
c. Sputum, induced - Have patient brush gums and teeth, then
rinse mouth thoroughly with water. Using a nebulizer, have the
patient inhale 20-30 mL of 3 to 10% sterile saline. Collect
sputum in sterile container.
Q. Respiratory, upper - Transport time ≤2 hours.
a. Oral - remove oral secretions and debris from surface of
lesion with a swab. Use a second swab to vigorously sample
lesion, avoiding normal tissue. Superficial swab specimens
should not be submitted. Tissue or needle aspirates are
preferred.
b. Nasal swabs (R/O SAPCR) - Insert a sterile swab (use Copan
dual swab 26200) into the nose until resistance is met at the
level of the turbinates (approximately 1-2 cm into one nostril).
Rotate the swab against the nasal mucosa for 3 sec. Apply slight
pressure with a finger on the outside of the nose to ensure good
contact between swab and inside of nose. Using the same swab,
repeat for the other nostril.
c. Sinus aspirates - Aspirate with needle and syringe.
Cleanse rubber stopper of anaerobic transport vial (59546) with
alcohol; push needle through septum and inject specimen on top of
agar.
d. Throat - Routine throat cultures will be processed only
for growth of β-hemolytic Streptococcus species.
Contact Microbiology Lab (356-2591) to arrange for provision of
special media if culture for other organisms (Corynebacterium
diphtheria, Neisseria gonorrhoeae) is desired. Do
not obtain throat samples if epiglottis is inflamed, as sampling
may cause serious respiratory obstruction. Sample the posterior
pharynx, tonsils, and inflamed areas with a sterile swab.
R. Sterile body fluids (other than CSF) -
a. Transport fluid to laboratory in sterile, leak-proof container
(BD Vacutainer, no additive, yellow top, 924044) or anaerobic
transport vial (Vial, 59546).
b. Cleanse rubber septum of container with 70% alcohol. Allow septum
to dry for 1 min before inoculating.
c. Disinfect overlying skin with iodine or chlorhexidine
preparation. Obtain specimen with needle and syringe. Push
needle through septum of transport container and inject fluid.
d. Amniotic and culdocentesis fluids should always be transported in
an anaerobic system (59546). Agar in anaerobic vial should be
clear before inoculation; inject fluid on top of agar.
e. Submit as much fluid as possible. NEVER submit a swab dipped in
fluid. NEVER inject fluid into swab container.
f. One aerobic blood culture bottle (924171) inoculated at bedside
(up to 10 mL) is highly recommended provided adequate sample is
available. If blood culture bottle is inoculated, submit separate
aliquot in anaerobic vial (59546) or sterile container (924044)
for preparation of cytocentrifuged Gram stain and inoculation of
solid media (allows quantitation, aids in culture interpretation).
g. Transport time <≤15 min, room temperature.
S. Stool - Submit 10-20 g in sterile container. Transport time is
≤1 hour. Refrigerate if transport is delayed. Stools
are cultured to isolate bacterial causative agents of diarrheal
illness; Salmonella, Shigella, Campylobacter, and Shiga
toxin producing E. coli. Routine stool culture includes EIA
for Shiga toxin from E. coli. Cultures for Yersinia are
performed by special request. Stools for C. difficile toxin
detection must be transported to the laboratory immediately or
refrigerated if transport is delayed. Surveillance cultures may be
ordered on Bone Marrow transplant and other immunocompromised
patients to detect overgrowth of normal flora by Staph
aureus, yeast or a gram negative bacillus.
T. Tissue - Submit in anaerobic collection jar (59547) or
sterile screw-cap container (37778); add drops of sterile saline to
keep small pieces of tissue moist. Transport time ≤15 min.
U. Urine - Collect 1-10 mL of urine in a sterile specimen
container (907069). Transport urine specimens to the microbiology
laboratory or refrigerate within 30 minutes.
Refrigerated specimens should be delivered to the lab as soon as
possible, and may be rejected if not received within 24 hours of
collection.
a. Midstream clean catch method: Patients should be
instructed to wash hands prior to collection and offered exam
gloves.
1. Female patients should be instructed to sit
on toilet with legs apart and spread labia with one hand.
First void in toilet and then, continuing to void, hold
specimen container in "midstream" to collect sample.
2. Male patients should be instructed to retract
foreskin if uncircumcised. First void in toilet and then,
continuing to void, hold specimen container in "midstream" to
collect sample.
b. Straight catheter: Thoroughly cleanse the urethral opening
with soap and water. Rinse area with wet gauze pads. Aseptically
insert catheter into the bladder. After discarding initial 15 to
30 mL of urine, collect urine for submission in a sterile
container.
c. Indwelling catheter: Clamp catheter below port and allow
urine to collect in tubing. Disinfect the catheter collection
port with 70% alcohol. Use needle and syringe to aseptically
collect 5-10 mL freshly voided urine though catheter port.
Transfer to sterile container. Do not collect urine from
collection bag.
d. Ileal conduit: Remove the external device and discard urine
within device. Gently cleanse the stoma with 70% alcohol
followed by povidone-iodine swab stick (907172). Using sterile
technique, insert a double catheter into the cleansed stoma, to
a depth beyond the fascial level, and collect the urine into a
sterile container. Use of a double catheter helps to minimize
contamination of the specimen with skin flora.
V. Wound - See abscess.
Instructions:
Contact University of Iowa Diagnostic Laboratories
1-866-844-2522 (toll free)
319-384-7213 (Fax)
1-866-844-2522 (toll free)
319-384-7213 (Fax)
See Additional Information:
Microbiology Specimen Collection and Transport
Normal (Indigenous) Flora of Human Body
Microbiology Specimen Collection and Transport
Normal (Indigenous) Flora of Human Body