Test Catalog

Test ID: BTWGS    
Bacterial Typing by Whole Genome Sequencing, Varies

Useful For Suggests clinical disorders or settings where the test may be helpful

Aiding in the investigation of a potential outbreak by a single bacterial species


May assist in identification of recurrent infection in an individual patient

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Organism identification is required. All bacteria submitted will be tested. Organism identifications that are incorrect or incomplete may result in no results at final analysis. Laboratory may perform matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) or other testing as listed in Reflex Tests to confirm identification, report this finding, and charge accordingly.


When reanalysis of previously submitted isolates for comparison to new isolates is requested, bioinformatics reanalysis will be added by Mayo Clinic Laboratories. Original patient submission information (names and order numbers) must be provided.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Bacterial strain typing may be useful for determining strain relatedness in the setting of possible nosocomial transmission or community outbreaks. Serial isolates obtained from the same patient may be typed to assess similarity. Typing may allow discrimination of 2 or more isolates of the same species, which can inform recognition of an outbreak, nosocomial transmission, or identify a potential source of infection in an individual patient.


Pulse-field gel electrophoresis (PFGE) has traditionally been used for strain typing, but does not always discriminate between different bacterial strains (eg, 2 genetically dissimilar strains may have indistinguishable PFGE patterns). Whole genome sequencing offers a higher level of resolution of genetic relatedness of strains than PFGE does.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Reported as isolates are "related", "possibly related", or "unrelated" by whole genome sequencing.

Interpretation Provides information to assist in interpretation of the test results

The genomic sequence of individual isolates will be determined and compared to the genomic sequences of the other cosubmitted isolates. The report will indicate the degree of relatedness between the isolates. A link to the interpretive report will be sent to the registered email address provided by the client.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Genomic relatedness does not prove that tested bacterial isolates are epidemiologically related. Establishment of an epidemiologic relationship requires correlation with clinical and epidemiological information. An epidemiological link may be ascribed if a common contact can be established between patients with bacterial strains demonstrating a high degree of genetic relatedness. Similar to other types of stain typing (eg, pulse-field gel electrophoresis: PFGE), sequence-based strain typing is most powerful in demonstrating genetic dissimilarity, decreasing the likelihood that the strains share a similar source.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Cunningham SA, Chia N, Jeraldo PR, et al: Comparison of whole-genome sequencing methods for analysis of three methicillin-resistant Staphylococcus aureus outbreaks. J Clin Microbiol 2017;55:1946-1953 doi.org/10.1128/JCM.00029-17

2. Park KH, Greenwood-Quaintance KE, Uhl JR, et al: Molecular epidemiology of Staphylococcus aureus bacteremia in a single large Minnesota medical center in 2015 as assessed using MLST, core genome MLST and spa typing, PLoS ONE 2017 June 2;12(6):e0179003 doi.org/10.1371/journal.pone.0179003

3. Madigan T, Cunningham SA, Patel R, et al:  Whole-genome sequencing for methicillin-resistant Staphylococcus aureus (MRSA) outbreak investigation in a neonatal intensive care unit. Infect Control Hosp Epidemiol 2018 Dec; 39(12):1412-1418 doi.org/10.1017/ice.2018.239

4. Trees E, Fei Fan Ng T, MacCannell D, et al: Molecular epidemiology. In Manual of Clinical Microbiology, 12th edition. Edited by K Carroll, M Pfaller, ASM Press, Washington, DC, 2019, pp 167-196

Special Instructions Library of PDFs including pertinent information and forms related to the test