Performance Comparison of Two In-House PCR Methods for Detecting Neisseria meningitidis in Asymptomatic Carriers and Antimicrobial Resistance Profiling.

Background/

Objective

Bacteriological culture has been a widely used method for the detection of meningococcus, but it has low sensitivity and a long turnaround time. Molecular detection targeting capsule transport A (ctrA) gene has been used, but over 16% of meningococcal carriage isolates lack ctrA, resulting in false-negative reports. The Cu-Zn superoxide dismutase gene (sodC) is specific to N. meningitidis, and is not found in other Neisseria species, making it a useful target for improved detection of non-groupable meningococci without intact ctrA. The primary objective of this study was to evaluate the performance compassion of two in-house PCR methods, sodC gene- and ctrA gene-based PCR assays, for detecting N. meningitidis in asymptomatic carriers. The secondary objective was to assess antimicrobial resistance profiling of N. meningitidis isolates.

Methods

The performance of sodC gene-based PCR assay compared to ctrA gene-based PCR for detection of N. meningitidis was evaluated using clinical samples (pharyngeal swabs; n = 137) collected from suspected asymptomatic carriers and culture-confirmed meningococci isolates (n = 49). Additionally, the antimicrobial sensitivity of the 49 isolates against antimicrobial drugs was determined using a disk diffusion test. Result: Of 49 DNA samples from culture-positive N. meningitidis isolates, the sodC gene-based PCR accurately identified all 49, whereas the ctrA gene-based PCR identified only 33 out of 49. Of 137 pharyngeal swabs, the sodC gene-based assay detected N. meningitidis DNA in 105 (76.6%), while the ctrA-based assay detected N. meningitidis DNA in 64 (46.7%). Out of the 49 N. meningitidis isolates, 43 (87.8%) were resistant to amoxicillin, 42 (83.7%) to ampicillin, 32 (65.3%) to trimethoprim-sulfamethoxazole, 22 (44.9%) to ceftazidime, 18 (36.7%) to ceftriaxone, and 7 (15.2%) to meropenem. Additionally, the majority of the isolates, 36 (73.5%), were sensitive to cefepime, 31 (63.3%) to ceftriaxone and meropenem, and 26 (53.1%) to ceftazidime.

Conclusions

The findings of this study highlight the necessity of adopting non-capsular sodC-based PCR to replace ctrA in resource-constrained laboratories to improve N. meningitidis detection, and underscore the importance of periodic antimicrobial resistance surveillance to inform and adapt treatment strategies.