Scope of Microbiology

• Types of Microbiology Labs:
  • Hospital labs
  • Private labs
  • Public Health Laboratories (PHLs)
  • National Microbiology Lab in Winnipeg (large reference lab)
• Typical Tests Performed:
  • Cultivation, identification, and antimicrobial susceptibility testing of microorganisms
  • Direct detection by microscopy
  • Chemical, immunologic, or molecular methods (e.g., PCR)
  • Serology/antibody testing

General Concepts for Specimen Collection and Handling

• Microbiology labs primarily function as 'referral' labs
• Smaller labs transfer samples to larger centers, increasing processing time
• Storage & Transportation Requirements:
  • Critical to maintain specimen integrity
  • Sterile collection techniques are essential, especially for:
  • CSFs
  • Blood cultures
  • Urines or sputum

Specimen Collection Techniques

• Collection can be patient-dependent (e.g., urines, stools, sputum)
• Preferred Techniques:
  • Midstream urine
  • Specific containers for stools
  • Sputum from deep coughs; saliva should be avoided
  • Provider-dependent specimens (e.g., swabs, sterile body fluids) should be collected using sterile techniques
• Labs may track contamination rates, leading to retraining if needed

Specimen Transport

• Ideal: specimens should reach lab within 2 hours; otherwise, refrigerate at 4°C
• Use biohazard bags for transport; certain specimens need unique containers

Specimen Requisitions

• Essential information includes patient demographics, collection details, and current antibiotic therapy
• Accurate sample description is necessary (e.g., specify "lower right leg wound swab")

Specimen Preservation

• Additives for Urine & Wounds:
  • Boric acid for colony counts in urine
  • Stuart's/Amie's medium for wound swabs
  • E-Swabs concentrate samples into liquid

Importance of Proper Handling

• Each specimen type requires appropriate collection and processing to ensure valid culture results
• Factors include the type of infective agents and standard culture requirements

Specimen Collection Requirements for Culture

• Optimal specimen collection timing is essential before antibiotic therapy begins
• Contamination must be minimized; examples include draining lesions or sputum collection techniques
• Epithelial cells and white blood cell counts are essential differentiators between acceptable sputum and saliva

Specimen Containers & Transport Change

• Sterile containers must be used to avoid contamination
• Choice of swab materials affects growth:
  • Avoid wooden shafts for Chlamydia cultures
  • Use appropriate materials to ensure viability for molecular assays

Blood Cultures

• Timing and technique for collection are crucial to avoid contamination from skin flora
• Follows a protocol for collection and should ideally occur before antibiotic administration
• Across multiple sets of cultures, 10 mL is the standard for adults, reduced for pediatrics

Urine Collections

• Clean catch midstream urine is preferred; catheterization is used when patients cannot void
• Quantitative methods help differentiate infections from contamination; >100 CFU/mL likely indicates UTI
• Proper cleaning of the collection site is crucial for accuracy

Body Fluids Collection

• Specific techniques apply to amniotic, joint, pleural, and CSF collections, emphasizing sterile methods
• Meningitis-causing bacteria like Neisseria meningitidis require immediate processing

Sputum Specimens

• Collection methods must ensure minimal contamination with saliva
• Additionally, throat swabs and special procedures are used for pneumonia detection

Learning Check Questions

• Understand proper protocol for processing urine specimens based on collection time
• Importance of blood volume and proper cleansing for blood culture integrity

Summary

• Microbiology specimens must be handled appropriately; understanding protocols, specimen integrity, and contamination prevention are vital to accurate diagnostics.