A diagnostic challenge in clinical laboratory: Misidentification of Neisseria subflava as Neisseria meningitidis by MALDI-TOF MS.

MALDI-TOF MS provides fast, easy to perform and cost-effective diagnosis in clinical microbiology laboratories, however in some cases results of MALDI-TOF MS should be confirmed with additional tests. This confirmation is especially important for causes of life-threatening infections like Neisseria meningitidis. In our laboratory, three isolates were identified as N. meningitidis by Bruker MALDI Biotyper (BD, USA) between April 2018 and March 2019 from clinical specimens of blood, sputum, and urine. 16S rRNA sequencing was performed for further investigation. Two of the isolates were identified as Neisseria subflava and only one was confirmed as N. meningitidis by sequencing. These results show that MALDI-TOF MS is not always reliable in the diagnosis of N. meningitidis and clinical microbiologists should confirm these results with additional tests. Also, clinical correlations should be determined. Accurate identification of this microorganism is very important because of the necessity of prophylactic antimicrobial usage and biosafety precautions. Enlarged databases of Neisseria species are needed to overcome this problem.