Bacteriology

The Bacteriology section provides conventional bacteriology diagnostic services, both for acute patient care and in support of public health. The section has high testing volumes and the focus is on rapid clinically relevant laboratory results. For information on specimen collection and transport for different conditions see the Provincial Microbiology Users Manual.

Blood Cultures

The lab uses the Bactec FX blood culture system.

The following are recommended collections:

  • Never take a single blood culture - Two or three blood cultures are far more useful in increasing sensitivity and aiding in the interpretation of possibly contaminated blood cultures.
  • Collect aerobic blood cultures only, unless for endocarditis or you specifically suspect that anaerobic infection is likely.
    • Intraabdominal infections
    •  Gynecologic infections
    • Necrotising soft tissue infection

Fungal blood cultures are no longer performed since yeasts grow well in conventional aerobic vials and most molds are not recovered from blood.

The Myco F Lytic vials are available from our Microbiology Processing Area when Mycobacterium avium- intracellulare infection in an immunosuppresed host is suspected.

Reporting Policies for blood cultures

  • Positive blood cultures are telephoned and the results expedited to the nursing station or ordering physician.
  • Final negative reports are issued after a five day incubation period.

Respiratory Cultures

  • Lower respiratory tract cultures are first screened by Gram stain and are scored according to their quality. Poor quality specimens contain excess saliva and cannot be reliably interpreted therefore these are rejected and repeat specimens requested. The extent of work-up depends on the quality of the specimen.
  • Culture for Legionella spp. should be specifically requested when clinically indicated.

Throat Cultures

Throat swabs are first screened for Streptococcus pyogenes antigens when the test is specifically requested and when:

  • The patient is ≤ 16 years of age.
  • Results can be made available on the day the specimen was collected and received in the Microbiology lab before 1800 hours.
  • The ordering clinic must be open to receive the result.

All positive antigens screen results are reported immediately.

All negative antigens tests and throat swabs on patients’ ≥ 17 years of age are cultured and positive culture results are expedited immediately.

Urine Cultures

  • Specimens must be submitted in a sterile container.
  • If urine specimens cannot be delivered to us on the same day, we recommend the use of sodium borate tubes available through our Stores department. (902-466-8070)
  • The lab limits the extent of microbial identification on urines with unusual or multiple organisms unless they are repeatedly present. It is important to indicate on a requisition when a urine specimen has been repeated at the lab's request.

Screens for resistant pathogens (MRSA and VRE)

Infection control protocol is in place for screening for both MRSA and VRE.

 MRSA

  • Nares and groin should be submitted on a single swab (as well as specimens from clinically suspect sites).

VRE

  • Rectal swabs are used (as well as specimens from clinically suspect open wound sites).

Stool Cultures for Enteric Pathogens

  • Stool specimens should be submitted in Enteric transport media.
  • Typically media for the detection of Salmonella, Shigella, Yersinia, Campylobacter, E. coli 0157 are routinely used and media for Vibrio sp. only when travel history is compatible with possible exposure.
  • Specimens submitted as part of an outbreak should be indicated as such, if possible include the Public Health Services outbreak number.
  • All enteric pathogens are typed either locally or at the National Microbiology Laboratory. It is important to do molecular fingerprinting to try to identify outbreaks and the source of those outbreaks. Our division participates in Pulsenet North (a system by which molecular profiles of important pathogens are shared between provincial public health laboratories).
  • All Salmonella, enterohemorrhagic E.coli and Shigella strains are required to be sent to the PPHLN anchor laboratory for full characterization.

Referred In Identification

  • Please complete the Sample Referral Form to guide our work-up.
  • The lab receives organisms from around the province for definitive identification. Using the Vitek MS, conventional biochemicals and molecular typing the lab is able to identify most referred in isolates.
  • Isolates that our lab is unable to speciate are referred to the National Microbiology Laboratory in Winnipeg.