Overview
MDL Test Name
Lower Respiratory Culture with Gram Stain
MDL Test Code
LR_CULT
Ask at Order Questions
N/A
Specimen Source
Lower Respiratory Sources:
Sputum
Tracheal Aspirate
Bronchial Wash
Bronchial Alveolar Lavage (BAL)
Biopsy
NOTE: indicate site with bronchial specimens i.e.: RUL, etc.
Specimen Requirements
Container/Tube
Sterile Container – Washing/Lavage/Sputum/Aspirate
Sterile Saline Tube – Brushing/Biopsy
Specimen Volume (minimum)
0.5 mL or ~ 5 mm diameter (if solid/semisolid)
Sample Stability Time
48 hours
Transport/Storage Conditions
Refrigerated (2 – 8°C)
Patient Preparation / Collection Instructions
Bronchial (BAL, washings, brushings): Collect via bronchoscopy and place in sterile container. Cover brushes with 1.0mL of sterile saline.
Sputum: Early morning specimens preferred. Instruct patient to produce lung material, not saliva. Collect in sterile container. Specimens can be collected by respiratory therapy (induced).
Tracheal Aspirate: Collect through mouth or nose using sterile tubing. Collect in sterile container.
Performance
Days Performed
Daily; Monday – Sunday
Report Available (TAT) – (Once received at MDL)
3 – 5 days
Specimen Retention Time
7 days
Method Description
Conventional aerobic bacterial culture technique with selective and non-selective media.
Identification methods (when appropriate) may include any of the following: conventional biochemical testing, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, and commercial identification panels.
Susceptibility testing (when appropriate) may include minimal inhibitory concentration (MIC) (broth microdilution or gradient strip diffusion) or disk diffusion.
Reference Values
No pathogens isolated.
Normal Respiratory Flora isolated.
Normal Respiratory Flora includes:
Viridans Streptococci
Non-pathogenic Neisseria
Diphtheroids
Coagulase-negative Staphylococcus
Rothia
Group F Streptococcus
Anaerobes
Haemophilus species (not influenzae)
Eikenella
Actinobacillus
Capnocytophaga
Moraxella
Enterococci
Yeasts (not cryptococcus)
Insignificant numbers of S. aureus, gram-negative rods, and N. meningitidis
Cautions
Lower respiratory samples are not routinely tested for anaerobic isolates.
Poor quality of sputum specimens is documented in gram stain by the presence of >10 squamous epithelial cells per low power field.
A negative bacterial culture does not rule out lower respiratory infection. The primary pathogen is frequently not recovered from patients with pneumoniae due to antimicrobial therapy or because the infection is caused by another type of organism (i.e.: virus, parasite, fungus, mycoplasma, or mycobacterium) that will not be recovered by routine bacterial culture.