Clinically Relevant Microbiology Starts at the Source

Clinically Relevant Microbiology Starts at the Source
By: Mike Costello, PhD, MT(ASCP)
ACL Laboratories
Mary Dikeman, MT (ASCP)
Affinity Health System

Program Objectives
* Emphasize that obtaining sensitive and specific microbiology results begins with the patient and not at the door of the microbiology laboratory.
* Accentuate the importance of proper collection and transport of specimens in both local and referral environments
* Stress the importance of timely communication between the Microbiology laboratory and those collecting specimens
* Describe common pitfalls in specimen collection and transport
* Discuss What rules or principles must be followed in order to collect microbiology specimens which will accurately reflect the pathogenesis of the microbiological agent. (Church D. The Seven Principles of Accurate Microbiology Specimen Collection. . Calgary Laboratory Services Microbiology Newsletter. Volume 6, 2005)

Introduction
The practice of sensitive, specific and cost effective clinical microbiology is intimately tied to the submission and proper handling of optimal specimens for analysis. Unfortunately, these aspects of clinical microbiology are not as critically controlled as our laboratory assays. It is our responsibility to educate and notify our healthcare colleagues when specimens arrive at the laboratory that will yield inferior results.

Quality assurance of specimen collection and transport is a never ending battle and requires long term commitment of your time and resources, but the end results are better patient care and a more rewarding experience for those of us who work in the microbiology laboratory.

Principle #1: The specimen must be collected with a minimum of contamination as close to
site of infection as possible

Urine Culture Contamination Rates

* Urine Culture contamination rates (>2 bacteria at >100,000 CFU) should be <20%
o CAP Q-Probe study (Valenstein P Meier F. Urine culture contamination: a College of American Pathologists Q-Probes study of contaminated urine cultures in 906 institutions. Arch Pathol Lab Med. 1998;122:123-129)..
+ 630 participants collected information of 155,037 urine culture specimens; 20.1% were considered contaminated (>2 organisms at >105 CFU)
+ The top 10% of institutions reported a rate of 5.6%. Bottom 10% of institutions reported a contamination rate of 36.8%
+ Males have a lower contamination rate than females (11.2% Vs. 22.8%)
+ ER departments had a contamination rate of 17.8%, sites adjacent to lab had rates of 19.5%, and other sites had rates of 22.1%

Blood Culture
* Two sets of blood cultures should be drawn. Number of sets positive correlates with true sepsis (except for coagulase negative Staph?) (Clin Microbiol. Rev 19:788-802, 2006)
* Catheter drawn blood cultures
o Catheter drawn blood cultures are equally likely to be truly positive (associated with sepsis), but more likely to be colonized (J Clin Microbiol 38:3393, 2001.)
+ One drawn through catheter and other though vein PPV 0f 96%
+ Both drawn from catheter PPV 0f 50%
+ Both drawn through vein PPV of 98%
o Study of positive coagulase negative Staphylococcus cultures and sepsis (Clin Infect Dis. 39:333, 2004.)

Blood Culture Contamination Rate
By Service Drawing Culture
What is an “Acceptable” Blood Culture Contamination Rate for Your Lab??
Blood Culture Contamination in Pediatric Patients
Young Children and Young Doctors
Inexperienced physician-young child
Inexperienced physician-older child
Experienced physician-younger child
Experienced physician-older child
Predicative Value of a Positive Result
False Positive
True Positive
Variable
Ped Infect Dis. 2006, 25:611-614.

Inexperienced Physicians = Interns and residents in 1st half of training
Experience Physicians = Residents in 2nd half of training and senior physicians
What is an “Acceptable” Blood Culture Contamination Rate for Your Lab??

What is an “acceptable” blood culture contamination rate*?
Berkeris LG, JA Toworek, MK Walsh, PN Valenstein. Trends in Blood Culture Contamination.
Arch Pathol Lab Med 129:1222-1294, 2005

Respiratory Cultures
* Community Acquired Pneumonia – Sputum rejection rate and culture correlation with gram stain
o 54% of all samples were judged to be of good quality.
o Presence of a (predominant morphology) PM on Gram stain was predictive of whether the sputum culture could demonstrate a pathologic organism. In the presence of a positive PM, 86% of cultures yielded a pathologic organism, while a positive culture was obtained in 19.5% of Gram stains without a predominant organism. S. pneumoniae was the most common infection, growing in 55.7% of positive sputum cultures.
o The sensitivity and specificity of finding Gram-positive diplococci for a positive culture of S. pneumoniae were 60% and 97.6%, respectively (Arch Intern Med. 2004;164:1725-1727, 1807-1811)
* Ventilator associated pneumonia (VAP) – appropriate specimen
o Blood cultures highly specific but not sensitive (positive in <10% of VAP)
o Quantitative cultures of lower respiratory tract specimens show a closer clinical correlation than sputum subcultures (Clinical Microbiol. Rev. 19:637-657, 2006.)

Viral Respiratory Cultures – Collect Sample From Site of Infection
How do you know that an adequate
Specimen was submitted for rapid
EIA assays???
Throat swabs are even worse!
Samples for Diagnosis of Viral Respiratory Infections
Lung biopsy
Bronchial alveolar
lavage/wash/brush
Nasopharygeal secretion
Nasopharygeal wash
Induced sputum
Nasopharygeal swab
Nasal wash


Throat swab (adenovirus only)
Saliva
Blood?
Sputum
DFA/EIA
OIA
Culture
LRTC*present
LRTC cells absent
Reagent Cost

Skin and Soft Tissue (Wound) Cultures
* Collect with steel (needle aspirate or scalpel)
* Discourage the use of swabs
* If infection NOT suspected, DON’T culture
* Get infected tissue or body fluid [ discourage swabs! ]
* -use something sharp ( syringe, scalpel, etc )
* -close doesn’t count
* *Don’t culture the surface / get deep infected sample*
* Remove needles / send capped syringe with aspirate
* Share specimen: Microbiology-Surgical Path-Cytology
* ** Label specimen and site accurately
* ** Give appropriate history
(Matkoski C. Sharp SE, Kiska DL. Evaluation of the Q Score and Q234 Systems for cost-effective and clinically relevant interpretation of wound cultures. J Clin Microbiol 2006;44:1869-1872)

Principle #2: A specimen must be collected at the optimal time(s) in order to recover the pathogen(s) of interest
Principle #3: A sufficient quantity of the specimen must be obtained to perform the requested tests
Blood Cultures
* Volume of blood drawn is the single most important factor influencing sensitivity. A single set for an adult blood culture consists of one aerobic and one anaerobic bottle. Optimally 10 mL of blood should be inoculated into each bottle. Volume of blood for a pediatric culture can be related to the infants weight
* Solitary blood cultures should be less than 5% (Arch Pathol Lab Med. 2001 125:1290-1294)
* If only enough blood can be drawn for one bottle, inoculate the aerobic bottle.
o 644 positive blood cultures, 59.8% from both bottles, 29.8% from aerobic bottle only and 10.4% from anaerobic bottle only (J Infect Chemother 9:227, 2003).
Pediatric Blood Cultures - Volume
Surgical Specimens (Other Shared Specimens)
TISSUE
FLUID
Specimen size of pea or larger
Divide
Anaerobic transport tube
Hold
upright,
uncap,
insert specimen and recap
Anaerobic
Culture
and stain

COLLECTION AND HANDLING OF OPERATING ROOM SPECIMENS FOR MICROBIOLOGY
Acceptable Specimens For Anaerobic Culture

Principle #4: Appropriate collection devices and specimen containers must be used to ensure recovery of all organisms
Recovery of Anaerobic Bacteria Placed in in Aerobic/Anaerobic Transport Media
CVP = Copan Vi-Pak Amies Agar Gel collection and transport swabs
SSS = Starplex StarSwab II,
PAC = BBL Port-A-Cult

How Does Transport Time Affect Yields?
J Clin Microbiol. 2001:39 377-380

Suggested Transport Media – General Comments

Principle #5: Collect all microbiology test samples prior to the institution of antibiotics
Principle #6: The specimen container must be properly labeled and sealed prior to transport
Principle #7: Minimize transport time or maximize transport media. There is always some loss of viability during transport
Minimize transport time and maximize use of transport media as much as possible
Environmentally Fragile Organisms
QA monitor??
Principle #8: Special handling/Collection instruction must be followed
* First, communicate with those that are doing collections.
* Collection instructions are written and available.
* Get involved with nursing orientation/education days and ask to have the instructions given out; poster board learning; quiz or competencies.
* Talk to providers when there are problems with specimen collection; they sometimes do not know they could do it better.


Principle #9: Improper specimen Collected for Ordered Test

Criteria For Rejection of Microbiological Specimens
* Criteria for rejection must be readily available and laboratory specific
* Unlabeled or improperly labeled specimen
* Prolonged storage or transport
* Improper or damaged container
* Specimen received in fixative
* Oropharyngeal contaminated sputum
* Duplicate specimens stools, sputum) within a 24 hour period. Exceptions cleared by the laboratory
* Specimens unsuitable for culture request (anaerobic culture from not acceptable source, urine from Foley catheter)
* Dry Swab
* 24-hr collection of urine or sputum for AFB or fungal culture
* Other criteria specific to your laboratory

Cultures That Should Include a Gram Stain
* CSF or sterile body fluid (cytospin)
* Eye
* Purulent discharge
* Sputum or transtracheal aspirate
* All surgical specimens
* Tissue
* Urethral exudates (male only, intracellular gonococcus))
* Vaginal specimens
* Wounds

Summary
* Publish specific rules for specimen collection
o There will be exceptions!
+ Make physician or healthcare provider aware of implications of culturing suboptimal specimens
* Communicate, communicate, communicate!
o Real time feedback
o Contact the health care worker who collected the suboptimal specimen

References

* Clinical Microbiology Procedures Handbook. 2nd Edition. . HD Isenberg ed. ASM. Cumitechs. ASM Press. Wash. DC.
* Manual of Clinical Microbiology, 9th Edition. ASM Press. Wash. DC. 2007.Miller MJ.
* A Guide To Specimen Management in Clinical Microbiology. ASM Press. Wash. DC. 1999.

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