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Genomic analysis of a Neisseria meningitidis patient isolate causing a false-positive result in the Abbott Alinity m
Björn Herrmann1,2, Andreas Sälléber3, Rene Kaden1,2,4
1Section of Clinical Microbioloby, Department Medical Sciences, Uppsala University, Uppsala, Sweden.
Background:
Diagnostics of sexually transmitted infections, such as Neisseria gonorrhoeae (NG), are often performed using high-volume test systems, often in combination with other targets. This report examines the occurrence of two false-positive NG results from pharyngeal samples in the Abbott Alinity m STI assay, cleared by the Food and Drug Administration.
Case Summary:
Analysis of pharyngeal samples from two men who have sex with men was positive for NG in the Abbott Alinity m STI assay, but negative upon confirmation testing with the Cepheid Xpert CT/NG assay. A pharyngeal culture isolate was obtained from one of the two men. The isolate tested negative for being NG in four different commercial nucleic acid amplification tests. A laboratory-developed PCR based on two targets gave inconclusive results, with positive detection for the opa gene but no detection for the porA gene. The isolate was identified as Neisseria meningitidis (NM) in MALDI-TOF analysis. Whole-genome sequencing revealed 322 diverse virulence genes, of which 314 were typical for NM and 8 for NG. Phylogenetic analysis showed a taxonomic delineation for NM.
Conclusion:
Confirmatory tests with alternative targets are essential for accurate analysis of NG, especially in low-prevalence settings. Evaluation of diagnostic tools to ensure accurate detection of NG is also needed.
