Collection of urine for
microbiological analysis
compiled by
Raymond B. Otero, Ph.D.
Consultant
Consulting Services
220 Delmar Dr.
Richmond, KY 40475
859-623-3973
Email: belinotero@aol.com
Urinary Specimens for Bacterial Culture
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Test name or method |
Specimen and special requirements |
Clinical comments and remarks |
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Urine culture - routine midvoid |
Females: cleanse meatus with soap or povidone-iodine-soaked gauze pads by spreading the labia and washing from front to back. Four pads should be used, one stroke per pad. Rinse the outer genitalia and area around the meatus with sterile water-soaked gauze pads while still spreading the labia. Males: cleanse the urethral meatus with soap and water. Patient should begin to urinate into commode and then catch the middle part of the voiding in a sterile wide mouth urine container. Transport to the laboratory immediately (<1 hour). If more than one hour is needed for transportation, then a urine transport kit should be used (i.e., BD-urine tube) |
Significant bacteriuria is usually indicated as >100,000 CFU/ml from a clean catch midvoid specimen. 1000 to 10,000 CFU/ml of one species represents probable or possible bacteriuria. <1000 CFU/ml from a midvoid specimen usually represents contamination and is considered non-significant. However, some symptomatic females with acute dysuric syndrome may have significant bacteriuria associated with as few as 100 - 200 CFU/ml.
Reliability of a single midvoid urine specimen is about 80% in females and about 100% in males if circumcised or if the male has carefully retracted the foreskin and cleansed the glans. With asymptomatic females, there is a rise of reliability to 90% with two specimens and 100% with three specimens when the same organism(s) is (are) isolate in significant numbers.
Aerobic organisms will be screened. It is absolutely necessary to transport the urine to the laboratory as quickly as possible since urine is a good culture medium. Prolong standing at room temperature will increase colony counts remarkably. Always use a urine transport kit (i.e., BD-tube) if delay is greater than one hour. |
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Catheterized specimen |
Collection: 1. Clamp drainage tubing for 10 - 15 minutes below level of urine sample port. 2. Cleanse the urine sample port with an alcohol pledget. 3. Insert needle into urine sample port. 4. Withdraw 4 ml of urine and discard urine and syringe. 5. Withdraw another 4 - 5 ml with another syringe. 6. Place specimen in a sterile urine cup. Using a BD-urine vacutainer, draw up approximately 4 ml. Mix gently. 7. Unclamp drainage tube. Fill out the requisition form completely (i.e., method of collection). 8. Transport to laboratory. |
Significant bacteriuria is usually defined as greater than or equal to 100,000 CFU/ml. Lower counts may be considered significant and may require reculturing for confirmation. Because of normal urethral colonization, it may be difficult to determine whether such organisms isolated from a catheterized specimen are of urinary origin (see accompanying table).
Aerobic bacteria in quantities of greater than or equal to 10,000 CFU/ml are identified by this type of specimen (cath). Bacteria present less than 1000 CFU/ml may not be detected by routine methods.
Urine specimens should not be collected from the drainage bag since bacterial replication may occur within the bag and also may be present on the port thus contributing to erroneous numbers.
Culturing for anaerobes and culturing catheter tips are inappropriate procedures. |
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Suprapubic |
Procedure: puncture bladder through lower abdominal (decontaminate skin with iodine) wall using a sterile needle and syringe. Place in BD-urine tube and transport to the laboratory immediately. |
Suprapubic aspirates are indicated for patients with equivocal colony counts and clinical evidence of urinary tract infections and for neonates and young children. The presence of any organism ruling out skin contamination along with clinical symptoms indicate infections. Bacterial counts are not performed on this type of specimen. This is the only acceptable specimen for anaerobic culture. |
Reference: Mosby's Diagnostic and Laboratory Test Reference, 5th Edition, 2001, K. D. Pagana and T. J. Pagana, Mosby, St. Louis, MO
Table 1 - Indigenous (normal) microbial flora of humans
Microorganisms normally residing on body surfaces or in various cavities of the body without invasion or harm to the host are referred to as indigenous (normal) flora. The type and numbers vary according to the environments of the surfaces and cavities. These organisms help prevent colonization, invasion and infection by pathogenic microorganisms. Some of the flora in the alimentary tract synthesize vitamin K, aid in nutrient absorption and help convert bile pigments and acids in the intestine. Although harmless in their usual sites, indigenous flora may produce disease (Escherichia coli causing urinary tract infections) if introduced into other areas (especially those cavities that are normally sterile) as opportunists.
The following list is a compilation of microorganisms that constitute indigenous flora encountered in various body sites in humans.
Mouth and oropharynx
1. viridans streptococci
2. coagulase-negative staphylococci
3. Veillonella sp.
4. Fusobacterium sp.
5. Treponema sp.
6. Bacteriodes sp.
7. Neisseria sp.
8. Moraxella catarrhalis
9. Streptococcus pneumoniae
10. beta-hemolytic streptococci (not group A)
11. Candida sp.
12. Haemophilus sp.
13. diphtheroids
14. Actinomyces sp.
15. Eikenella corrodens
16. Staphylococcus aureus
Nose
1. coagulase-negative staphylococci
2. viridans streptococci
3. Staphylococcus aureus
4. Neisseria sp.
5. Haemophilus sp.
6. Streptococcus pneumoniae
Outer ear
1. coagulase-negative staphylococci
2. diphtheroids
3. Enterobacteriaceae (occasionally)
4. Bacillus sp.
5. Micrococcus sp.
6. Moraxella catarrhalis
7. Pseudomonas sp.
Conjunctivae
1. coagulase-negative staphylococci
2. Haemophilus sp.
3. Streptococcus sp. (various sp.)
Skin
1. coagulase-negative staphylococci
2. diphtheroids (including Propionibacterium acnes)
3. Staphylococcus aureus (certain sites such as axilla, perineum)
4. Streptococcus sp. (various sp)
5. Bacillus sp.
6. Malassezia furfur
7. Candida sp.
8. Mycobacterium sp. (occasionally)
Urethra
1. coagulase-negative staphylococci
2. diphtheriods
3. Streptococcus sp. (various sp.)
4. Enterococcus sp.
5. Bacteriodes sp.
6. Fusobacterium sp.
7. Peptostreptococcus sp.
8. Mycobacterium sp.
Vagina
1. Lactobacillus sp.
2. Peptostreptococcus sp.
3. diphtheriods
4. Streptococcus sp. (various sp.)
5. Enterococcus sp.
6. Clostridium sp.
7. Bacteriodes sp.
8. Candida sp.
9. Gardnerella vaginalis
Gastrointestinal tract
-Small intestine
1. Lactobacillus sp.
2. Bacteriodes sp.
3. Clostridium sp.
4. Mycobacterium sp.
5. Enterococcus sp.
6. Enterobacteriaceae (all members represented except Salmonella, Shigella, and Yersinia)
-Large intestine
1. Bacteriodes sp.
2. Fusobacterium sp.
3. Clostridium sp.
4. Peptostreptococcus sp.
5. Enterobacteriaceae (all members represented except Salmonella, Shigella, and Yersinia)
6. Lactobacillus sp.
7. Streptococcus sp. (various sp.)
8. Enterococcus sp.
9. Pseudomonas sp. (about 10% of the time)
10. coagulase-negative staphylococci
11. Acinetobacter sp.
12. Staphylococcus aureus
12. Mycobacterium sp.
13. Actinomyces sp.
Reference: Manual of Clinical Microbiology, 8th Edition, American Society for Microbiology. Washington, DC, 2003
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Otero, Ph.D., All Rights Reserved. |