(P100) Neisseria gonorrhoeae multi antigen sequence type for strain typing and matched clinical nucleic acid amplification test results on samples transported in cobas PCR media

Tuesday, July 25, 2023

16:00 – 18:00 CST

Primary Presenter(s)

BL

Brigitte Lefebvre, PhD

Microbiologist
Laboratoire de santé publique du Québec
Sainte-Anne-de-Bellevue, Quebec, Canada

Co-author(s)

AL

Annie-Claude Labbé

Département de microbiologie, infectiologie et immunologie, Université de Montréal
Montréal, Quebec, Canada
CL

Christian Lavallée

Département de microbiologie, infectiologie et immunologie, Université de Montréal
Montréal, Quebec, Canada
IM

Irene Martin, n/a

Biologist
Public Health Agency of Canada
Winnipeg, Manitoba, Canada
JF

Judith Fafard

Laboratoire de santé publique du Québec et Département de microbiologie, infectiologie et immunologie, Université de Montréal, Quebec, Canada
CF

Claude Fortin

Département de microbiologie, infectiologie et immunologie, Université de Montréal, Quebec, Canada

Background: Interpretation of test of cure (TOC) for Neisseria gonorrhoeae infection is challenging when nucleic acid amplification tests (NAAT) are used. With the rise of antimicrobial resistance in N. gonorrhoeae, it is important to adequately differentiate true treatment failure from reinfection. N. gonorrhoeae multi antigen sequence type (NG-MAST) is used on strains isolated from cultures. However, due to increased availability of NAAT for gonorrhea screening and diagnosis, less culture is being performed. Typing by NG-MAST was demonstrated to be useful to investigate treatment failure in a context of TOC in situations where bacterial cultures of N. gonorrhoeae are no longer used. This study evaluates the use of NG-MAST typing directly on clinical samples transported in cobas PCR media.

Method: NG-MAST was performed on 104 pairs: clinical samples positive for N. gonorrhoeae by NAAT (cobas 4800, Roche) and matching N. gonorrhoeae cultures from the same site of infection (cervix [n=2], anus [n=6], throat [n=26], urine/urethral secretions [n=70]). NG-MAST is based on sequencing of the porB and tbpB genes.

Results: NG-MAST were successfully determined for 77 of 104 matched specimens (74%). The NG-MAST concordance was 100% (2/2) for cervix samples, 83% for anus samples (5/6), 96% for urine/urethral secretion (67/70) but only 12% for throat samples (3/26). For 81% of throat samples, the tbpB sequence was concordant between the clinical sample for NAAT and culture but porB was not identified on the NAAT sample. Excluding throat samples, NG-MAST were successfully determined for 74 of 78 matched specimens (95%; 95%CI 87-98%) Twenty different sequence types (ST) were identified; ST-14994 (32%) and ST-12302 (22%) were the most predominant. Six ST were not found in the NG-MAST database.

Conclusion: NG-MAST on NAAT specimens and matched isolates performed well on cervix, anus and urine/urethral secretions samples but not on throat samples, possibly due to commensal Neisseria found at that site. Although this tool can be an important addition to help interpret TOC results obtained by NAAT, it remains unsatisfactory on throat samples. As treatment failure are most often associated with throat samples, a more successful typing method should be used for that site of infection.