Rapid detection of Group B streptococcus directly from vaginal-rectal specimens using liquid swabs and the BD Max GBS assay. 2017

J A Ellem, and D Kovacevic, and T Olma, and S C-A Chen
Centre for Infectious Diseases and Microbiology Laboratory Services, NSW Health Pathology, Westmead Hospital, Westmead NSW, Australia. Electronic address: justin.ellem@health.nsw.gov.au.

OBJECTIVE We adapted the BD Max GBS assay, an automated platform for the detection of Group B streptococcus (GBS) DNA in vaginal-rectal swab specimens after LIM broth enrichment, to directly detect GBS in specimens collected using cellular foam swabs in Amies liquid medium. We compared the BD Max GBS assay performance to that of enriched culture and the BD GeneOhm StrepB assay. METHODS Seventy-two reference vaginal-rectal specimens were employed to determine the limit of GBS detection and the preferred test volume for direct detection of GBS. A total of 304 clinical specimens were then tested by the optimized BD Max GBS assay, both by direct testing and following broth enrichment. RESULTS The limit of GBS detection was 75 CFU/mL and the preferred test volume was 100 μL. Of 304 clinical specimens tested, GBS was detected in 62 specimens by enriched culture (20.4%); 61 of these yielded GBS by the BD Max GBS assay when performed directly from the liquid swab (sensitivity 98.4%). All 242 culture-negative specimens also yielded negative results by the BD Max GBS assay (specificity 100%). When this assay was performed following broth enrichment, GBS was detected in all 62 culture-positive specimens (100% sensitivity). The sensitivity and specificity of the BD GeneOhm StrepB assay was 90.3% and 99%, respectively. CONCLUSIONS The BD Max GBS assay is highly sensitive, requires minimal technical skill with <2 min required to set-up, and results are available in under 80 min (versus 24-48 h for culture). It is configured for 'on demand' testing and vaginal-rectal specimens can be rapidly screened for GBS without the need for enrichment. The results obtained in this study demonstrate that rapid GBS screening using the BD Max GBS assay at the time of delivery is a viable alternative to the current recommended screening at 35-37 weeks of gestation with pre-enrichment testing methods.

UI MeSH Term Description Entries
D011247 Pregnancy The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH. Gestation,Pregnancies
D011251 Pregnancy Complications, Infectious The co-occurrence of pregnancy and an INFECTION. The infection may precede or follow FERTILIZATION. Complications, Infectious Pregnancy,Infectious Pregnancy Complications,Maternal Sepsis,Pregnancy, Infectious Complications,Sepsis during Pregnancy,Sepsis in Pregnancy,Infectious Pregnancy Complication,Pregnancy Complication, Infectious,Sepsis in Pregnancies,Sepsis, Maternal
D012007 Rectum The distal segment of the LARGE INTESTINE, between the SIGMOID COLON and the ANAL CANAL. Rectums
D004269 DNA, Bacterial Deoxyribonucleic acid that makes up the genetic material of bacteria. Bacterial DNA
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001322 Autoanalysis Method of analyzing chemicals using automation. Autoanalyses
D013048 Specimen Handling Procedures for collecting, preserving, and transporting of specimens sufficiently stable to provide accurate and precise results suitable for clinical interpretation. Specimen Collection,Collection, Specimen,Collections, Specimen,Handling, Specimen,Handlings, Specimen,Specimen Collections,Specimen Handlings
D013290 Streptococcal Infections Infections with bacteria of the genus STREPTOCOCCUS. Group A Strep Infection,Group A Streptococcal Infection,Group A Streptococcal Infections,Group B Strep Infection,Group B Streptococcal Infection,Group B Streptococcal Infections,Infections, Streptococcal,Infection, Streptococcal,Streptococcal Infection
D013292 Streptococcus agalactiae A bacterium which causes mastitis in cattle and occasionally in man. Streptococcus Group B

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