Lab Matters Fall 2024 | Page 75

APHL 2024 POSTER ABSTRACTS sub-study of stored specimens from the Pre-exposure Prophylaxis Initiative ( iPrEx ) study participants , which enrolled HIV-seronegative men and transgender women who have sex with men from six countries to evaluate the performance of three rapid syphilis diagnostic tests in this high syphilis prevalence population .

Methods : The CDC ’ s STD Laboratory Reference and Research Branch received frozen sera from iPrEx participants ’ visits . Sera were thawed and tested in the same freeze-thaw cycle using the Rapid Plasma Reagin ( RPR , Arlington Scientific ), T . pallidum particle agglutination ( TP-PA , Fujirebio ) and rapid syphilis tests : Syphilis Health Check ( SHC , Diagnostics Direct ), DPP HIV-Syphilis ( Chembio Diagnostics ) and DPP Syphilis Screen & Confirm ( Chembio Diagnostics , Research Use only ) following respective manufacturer ’ s instructions . Treponemal test results for all three rapid syphilis tests were compared to TP-PA results . For the nontreponemal test of DPP Syphilis Screen & Confirm , the results were compared to RPR .

Results : Of 808 sera tested , 89 ( 11.0 %) had reactive RPR tests and 149 ( 18.4 %) had positive TP-PA results . A comparison of treponemal test results from SHC , DPP HIV-Syphilis and DPP Screen & Confirm to TP-PA showed sensitivity ranging from 87 % to 98 %. The specificity for all three rapid syphilis tests ranged from 92 % to 98 %. Non-treponemal test results from DPP Syphilis Screen & Confirm showed a sensitivity of 75 % and a specificity of 95 % in comparison to RPR . The DPP Screen & Confirm test had a sensitivity of 37 % for RPR reactive sera with titer 1:1 , 84.2 % for 1:2 , 87.5 % for 1:4 and of 100 % recorded for > 1:8 titer .

Conclusions : DPP HIV-Syphilis demonstrated a higher sensitivity but a lower specificity for treponemal antibody detection compared to SHC and DPP Screen & Confirm tests in our evaluation . For the nontreponemal test of DPP Syphilis Screen & Confirm , there was a higher specificity , but overall lower sensitivity recorded , mostly with low RPR titer sera . Additional evaluation using sera collected from various disease stages and populations may shed more light on the performance of rapid syphilis tests .

Presenter : Mayur Shukla , iun9 @ cdc . gov

Laboratory process Improvement Through Implementation of a Hybrid Salmonella Serotyping Workflow

S . Abromaitis , F . Xu , L . Li , A . Tieku , A . Angermeyer , Z . Berrada , California Department of Public Health

The California Department of Public Health Microbial Diseases Laboratory ( MDL ) transitioned to a hybrid Salmonella serotype testing workflow that uses both traditional agglutination-based serotyping and genome-based serotyping in October 2023 . Workflow and reporting changes were necessitated by the limited number staff at MDL with the expertise and certification to perform traditional Salmonella serotyping for clinical reporting , significant testing backlogs , limited quantities of specialized in-house generated antisera and loss of capacity to produce new antisera to replenish stocks , with no commercial alternatives available .

To address these challenges , MDL validated the whole genomebased Salmonella serotype determination using BioNumerics that was already being performed as part of MDL ’ s routine Salmonella sequencing for PulseNet surveillance . In the new hybrid workflow , MDL reports the genome-based Salmonella serotype directly to the local health department through the California Reportable Disease Information Exchange ( CalREDIE ) for epidemiological purposes .

To facilitate and automate reporting , MDL developed a new data workflow within the STARLIMS laboratory information management software . CDPH bioinformaticians developed python scripts that automated reformatting of exported BioNumerics serotype data for import to STARLIMS . This automation removes the potential for analyst entry errors and allows for bulk re-accessioning , rapid results importing and results transmission to CalREDIE . MDL will continue to perform and report traditional agglutination-based serotyping for clinically significant Salmonella submissions . These include isolates from sterile sources and presumptive or confirmed S . typhi or S . paratyphi . This change is anticipated to reduce the traditional agglutination-based serotyping workload by approximately 75 %, which will allow for a more rapid turnaround time for clinically significant agglutination-based serotyping results . The newly implemented hybrid Salmonella serotype testing workflow has resulted in a decrease in testing duplication , improved turnaround time and significant cost savings .

Presenter : Stephanie Abromaitis , stephanie . abromaitis @ cdph . ca . gov

Molecular Characterization of New Delhi Metallobeta-lactamase Producing Carbapenem-resistant Enterobacterales in 2017 – 18 Versus 2022 Collections from the Antimicrobial Resistance Laboratory Network

T . Darby , K . Bantle , S . Sabour , N . Vlachos , A . Van Zyl , S . McKay , A . Brown , Centers for Disease Control and Prevention

Infections caused by multidrug-resistant Gram-negative bacteria are a major global health challenge . Carbapenem-resistant Enterobacterales ( CRE ) are concerning due to their potential for spread and ability to cause infections that have limited treatment options . A common mechanism for carbapenem resistance in Enterobacterales is the production of carbapenemases . Since their initial identification , carbapenemase-producing CRE ( CP-CRE ) have spread rapidly and globally . One plasmid-mediated carbapenemase is New Delhi metallo-lactamase ( NDM ), a metallo-beta-lactamase that confers resistance to clinically important antimicrobials . Since 2017 , when testing in CDC ’ s Antimicrobial Resistance Laboratory Network ( AR Lab Network ) began , there has been a rise in the frequency and proportion of NDM-producing CRE ( NDM-CRE ) detected by the Network ’ s participating public health laboratories ( PHLs ). We compared the frequencies and genetic characteristics of AR Lab Network NDM-CRE isolates collected during 2017 – 2018 to those from 2022 .

Each of the 56 PHL engages with a network of clinical laboratories across the AR Lab Network to submit bacterial isolates for phenotypic and molecular testing . The size and coverage of each PHL ’ s network vary based on their jurisdiction ’ s reporting laws and submission criteria for CRE . Testing included organism identification and PCR-based detection of a blaNDM gene . CDC conducted whole genome sequencing ( WGS ) on its first collection of AR Lab Network isolates , submitted during 2017 – 2018 . Upon establishing their own WGS capacities , AR Lab Network PHLs conducted WGS and shared all testing data with CDC for isolates submitted during 2022 . WGS data were analyzed using CDC ’ s in-house bioinformatics pipeline to assess data quality , confirm organism and identify NDM variants .

During 2017-2018 , 7,461 CP-CRE isolates were detected , 567 ( 7.2 %) of which were identified as NDM-CRE . These NDM-CRE isolates were Klebsiella spp . ( n = 261 , 46.0 %), E . coli ( n = 229 ,