Bacteriology Specimen Handling, Collection, Transport, and Processing Review

Flashcards reviewing specimen collection, transport media, anticoagulants, storage temperatures, processing guidelines, and critical values in bacteriology.

During which phase of illness should bacterial specimens ideally be collected?

Acute or early phase of illness

Why should contamination from normal biota be minimized during specimen collection?

Because normal biota contamination can interfere with culture results

What labeling issue leads to immediate specimen rejection?

Unidentified or improperly labeled specimen

What is the rejection criterion when specimen documentation does not match the sample tube?

Label–requisition mismatch

What parameters regarding collection and transport conditions cause specimen rejection?

Improper temperature, medium, container, or insufficient quantity

Why is a specimen that leaks during transport unacceptable for processing?

It poses a contamination risk and potential exposure, making it unacceptable

Why are specimens submitted in formalin or other fixatives rejected for bacterial culture?

Fixatives kill bacteria, rendering the sample unsuitable for culture

When is an anaerobic culture specimen rejected based on its collection site?

When collected from a site containing normal anaerobes

Why is a dried swab unacceptable for laboratory processing?

Desiccation kills delicate bacteria, making the specimen non-viable

What are the rejection criteria for an expectorated sputum specimen?

Fewer than 25 WBCs, more than 10 epithelial cells/LPF, and mixed flora

How do swab specimens compare to tissue or needle aspirates?

Swab specimens are generally poorer quality compared to tissue or needle aspirates

What is the preferred specimen collection method and site for lesions, wounds, and abscesses?

Aspirate obtained from the advancing margin

What is the ideal transport time for most bacterial specimens?

Within 30 minutes

What is the general maximum target time for most specimens to reach the laboratory?

Within 2 hours

Within what time frame should anaerobic culture specimens be transported?

10 minutes or less

Within what time frame should Cerebrospinal Fluid (CSF) reach the laboratory?

Within 15 minutes

How long may blood and bone marrow specimens be kept at room temperature?

Up to 2 hours

How should gastric biopsy specimens be transported?

Immediately at $4^\text{o}\text{C}$

What are the transport time and storage temperature requirements for catheterized urine?

Transported within 2 hours and refrigerated when necessary at $4^\text{o}\text{C}$

Which specimens may be stored at $4^\text{o}\text{C}$ for up to 24 hours?

Rectal swabs, stool cultures, and clean-voided midstream urine

What is the temperature rule for viral isolation specimens?

Refrigerated immediately, but should never be frozen

Which chemical agent may be used as a urine preservative?

Boric acid

Which transport medium is used when stool processing is delayed for more than 2 hours?

Cary-Blair medium

What storage temperature is used for long-term preservation of tissue and specimens?

$$-70^\text{o}\text{C}$$

What storage temperature is used for serum intended for serology testing?

$$-20^\text{o}\text{C}$$

What storage temperature is recommended for CSF intended for Gram stain, culture, and sensitivity?

$$35^\text{o}\text{C}$$

What temperature range is recommended for holding anaerobic cultures, sterile body fluids, and genital swabs?

$$22-25^\text{o}\text{C}$$

What transport medium is specified for general swab specimens?

Stuart's medium

Which transport medium is commonly used for bacterial swabs?

Amies medium

Which transport medium is designed for delayed stool specimens?

Cary-Blair medium

Which transport system maintains organisms requiring a CO2-rich environment?

Transgrow

What transport system is specifically designed for gonococcal specimens?

JEMBEC (John E. Martin Biological Environmental Chamber)

What does the anticoagulant abbreviation SPS stand for?

Sodium Polyanethol Sulfonate

What does the abbreviation CSF stand for?

Cerebrospinal Fluid

What does the abbreviation AFB stand for?

Acid-Fast Bacilli

What does the abbreviation BAL stand for?

Bronchoalveolar Lavage

Which anticoagulant is routinely used in blood culture bottles?

Sodium Polyanethol Sulfonate (SPS)

How does SPS assist bacterial survival in blood cultures regarding host immunity?

Inhibits phagocytosis and complement activity

How does SPS counteract antimicrobial and plasma activities in blood culture?

Neutralizes aminoglycosides and the bactericidal effect of plasma

Which specific organisms can be inhibited by the anticoagulant SPS?

N. gonorrhoeae, N. meningitidis, Gardnerella vaginalis, Streptobacillus moniliformis, and Peptostreptococcus anaerobius

Which anticoagulant is used for viral cultures and isolation of Mycobacterium spp. from blood?

Heparin

Which two anticoagulants should NOT be used for routine microbiology specimens?

Citrate and EDTA

What does the abbreviation EDTA stand for?

Ethylenediaminetetraacetic Acid

When is the optimal time to draw blood cultures relative to patient symptoms?

Just before an anticipated temperature rise

What is the routine recommended number of blood culture sets to collect?

2–4 sets

How many separate blood cultures should be collected over 2 days for fever of unknown origin?

4 separate cultures

What two bottle atmosphere types must be included in a blood culture set?

Aerobic and anaerobic bottles

What temperature and duration are standard for routine blood culture incubation?

$35^\text{o}\text{C}$ for 7 days

How long may blood cultures be incubated if endocarditis, brucellosis, or fungemia is suspected?

2–4 weeks

What visual signs in blood culture bottles indicate bacterial growth?

Hemolysis, gas bubbles, turbidity, or colony formation

Which blood processing method utilizes cell lysis and centrifugation to concentrate organisms?

Lysis-centrifugation / Isolator

Which automated blood culture system detects bacterial growth using electrical impedance?

BACTOMETER

Which automated blood culture system detects microbial growth via CO2 metabolism?

BACTEC

From what anatomical site and procedure is CSF collected?

Lumbar subarachnoid space by lumbar puncture

Which sequentially numbered CSF tube is designated for microbiology?

Tube 2

What testing is performed on CSF Tube 1?

Chemical and serologic testing

What testing is performed on CSF Tube 3?

Cell count

Which fraction of centrifuged CSF is used to prepare smears and inoculate culture media?

Sediment

What serologic methods are listed for rapid antigen detection in CSF?

Counter-current immune electrophoresis, coagglutination (PHADEBACT), and latex agglutination

Which enrichment broths are used for CSF culture?

TSB or THIO

Which agar plate is used to isolate Gram-positive cocci from CSF?

BAP (Blood Agar Plate)

Which agar plate is used to isolate Gram-negative cocci from CSF?

CAP (Chocolate Agar Plate)

Which culture media are used to isolate Gram-negative bacilli from CSF?

EMB (Eosin Methylene Blue agar) / MAC (MacConkey agar)

From which anatomical areas should a throat swab for Streptococcus pyogenes be collected?

Posterior pharynx, tonsils, and areas of purulence/inflammation/ulceration

What sheep blood-enriched agar is specified for isolating S. pyogenes from throat swabs?

Soybean-Casein Digest Agar with 5% sheep blood

Which antibiotic disk is used in the identification workup of S. pyogenes?

Bacitracin disk

What are the incubation conditions for S. pyogenes throat cultures?

$35^\text{o}\text{C}$ for 18–24 hours

What is the main clinical diagnostic utility of a nasopharyngeal swab?

Detecting nasopharyngeal carriers and viral/bacterial pathogens

Which organism causes whooping cough?

Bordetella pertussis

Which selective media are used to isolate Bordetella pertussis?

Charcoal Cephalexin Medium or Bordet-Gengou

Which culture media are used for Corynebacterium diphtheriae isolation?

Loeffler agar slant with cystine-tellurite

Which selective media are used for N. gonorrhoeae and N. meningitidis isolation?

Modified Thayer-Martin or Martin-Lewis

Why is a first-morning sputum specimen preferred over random samples?

Because respiratory secretions accumulate overnight

How many consecutive early-morning sputum samples should be collected for optimal diagnostic yield?

2–3 specimens

Which standard stains are used for direct microscopic examination of sputum?

Gram stain and AFB stain

Which routine agar media are used for respiratory sputum culture?

MAC, BAP, and CAP

How should specimens for anaerobic respiratory culture ideally be obtained?

Percutaneous aspiration or protected brush

What is the recommended sample size for a stool culture specimen?

Walnut-sized specimen

Within what time frame should an unpreserved stool specimen be delivered to the lab?

Within 1 hour

What infection is suspected when clumps of Gram-positive cocci are observed in direct stool examination?

Staphylococcal infection

Which organisms are suggested by thin, comma-shaped Gram-negative bacilli in stool?

Campylobacter or Vibrio

Which organism is suggested by finding large numbers of large/thin Gram-positive bacilli in stool?

Clostridioides difficile (C. difficile)

Which direct stain is used on stool specimens to detect Cryptosporidium and Mycobacteria?

AFB stain

Which agar media are used for routine isolation of Salmonella and Shigella from stool?

HEA, XLD, or SSA

Which specific media are listed for isolated culture of Salmonella?

Brilliant Green or Bismuth Sulfite

Which selective medium is used for Campylobacter isolation?

Campy-Blood agar

Which selective medium is used for Vibrio cholerae?

TCBS (Thiosulfate-Citrate-Bile Salts-Sucrose agar)

Which selective medium is used for Yersinia enterocolitica?

CIN (Cefsulodin-Irgasan-Novobiocin agar)

Which selective medium is used for Clostridioides difficile isolation?

CCFA (Cycloserine-Cefoxitin-Fructose Agar)

Which enrichment broths are used for isolating enteric pathogens from stool?

Selenite F, Hajna GN, and Tetrathionate

What is the preferred gastric specimen type for pediatric patients and AFB studies?

Gastric aspirate

Within what time frame must a gastric aspirate be neutralized?

Within 1 hour

What is the preferred specimen for diagnosing Helicobacter pylori infection?

Gastric biopsy

How far past the anal sphincter should a rectal swab be inserted?

Approximately 2.5 cm

Which non-invasive urine specimen is standard for routine bacterial culture?

Clean-catch midstream urine

What invasive collection methods exist for urine culture?

Suprapubic aspiration, straight catheterization, and Foley catheter

Within what time frame should unpreserved urine be processed for culture?

Within 2 hours

If processing is delayed, at what temperature and duration may urine be refrigerated?

$4^\text{o}\text{C}$ for up to 24 hours

What is the simplest and fastest method to screen uncentrifuged urine for significant bacteriuria?

Gram stain

Finding 1 organism per oil-immersion field in uncentrifuged urine correlates to what colony count?

More than $10^5\text{ CFU/mL}$