Commensal Flora and Specimen Collection

Flashcards on Commensal Flora and Specimen Collection

Commensal Flora

Population of microorganisms that inhabit the skin and mucous membranes of healthy individuals; also referred to as symbionts or microbiome.

Transient Flora

Microorganisms that colonize for hours to weeks, but no longer.

Colonization Resistance

The ability of commensal flora to form a barrier against pathogens by competing for space and nutrients.

Bacteriocins

Substances produced by commensal flora that can inhibit other organisms.

Antisepsis

Process used on skin to minimize contamination before specimen collection (e.g., swabbing with 70% alcohol or povidone iodine).

Selective Media

Media used during specimen processing to inhibit commensals and encourage pathogen growth.

Sterile Body Sites

Blood, bone marrow, cerebrospinal fluid, serous fluids, tissues.

Non-Sterile Body Sites

Mouth, nose, upper respiratory tract, skin, gastrointestinal tract, female genital tract, urethra.

Septicemia

Infectious disease of the bloodstream; Blood is the typical specimen.

Meningitis

Infectious disease of the the brain and spinal cord; CSF is the typical specimen.

Gastroenteritis

Infectious disease of the GI tract; Faeces or a rectal swab is the typical specimen.

UTI

Infectious disease of the bladder/urinary tract; Urine is the typical specimen.

Empirical Therapy

Treatment started before a definitive diagnosis, which may negate the need for specimen collection if effective.

Transport Media

Media used to maintain microbial population in a specimen as close as possible to what it was at the time of collection.

Cary Blair Medium

Semi-solid transport medium good for enteric bacteria; lacks fermentable carbohydrates.

Stuart Transport Medium

Semi-solid transport medium good for fastidious organisms, such as gonococci and streptococci.

Amies Charcoal Medium

Transport medium where charcoal absorbs fatty acids toxic to N. gonorrhoeae.

Viral Transport Medium

Transport medium containing antibiotics and antifungals to prevent bacteria and fungi growth.

Dacron-tipped swabs

Recommended for detection of viruses, Bordetella, N. gonorrhoea, Mycoplasma; suitable for both PCR and culture.

Calcium alginate-tipped swabs

Swabs without fatty acids that may be toxic for lipid-enveloped viruses/inhibit PCR.

Blood Culture

Most sensitive method for detecting organisms in blood.

CSF Transport

Must be transported immediately to lab at room temperature.

AFB smear

Diagnostic procedure to detect Mycobacterium tuberculosis in CSF.

Cary-Blair transport medium

Transport media optimal for faecal specimens that cannot be processed within 2 hours.

Midstream Specimen of Urine (MSU)

Common method for urine collection to detect UTI or cystitis, preventing contamination with urethral colonizers.

Bacterial Vaginosis

Can be detected via Gram stained smear by looking for clue cells.

Clue Cells

Epithelial cells covered in bacteria, indicative of bacterial vaginosis.

Nasopharyngeal Secretions

Specimen type used to detect carriers of Bordetella spp., N. meningitidis, and respiratory viruses.

Otitis Externa

Outer ear infection which sample are likely contaminated with normal flora.

Pleural Fluid

Specimen collected from the lower respiratory tract with the chance of pneumonia.