Prevalence of ctrA and crgA genes in non-meningococcal neisserial species colonising the upper respiratory tract among university students in Örebro

Sammanfattning: Introduction: A Neisseria meningitidis carrier study has been conducted among students at Örebro university in Sweden in 2018 and 2019. Pharyngeal samples were collected from 3489 students. PCR for the genes ctrA and crgA was run on all samples. The positive samples were then cultured on agar plates to find the N. meningitidis. In 349 of the PCR positive samples, no N. meningitidis could be isolated, which raised the question if other bacteria could have these genes. The most likely bacteria to have these genes were assumed to be other species within the genus Neisseria. Aim: To identify whether other neisserial species have the ctrA and crgA genes. Methods: The 349 samples were cultured on agar plates for two days. The species were then identified by MALDI-TOF MS. The isolated Neisserial species and some other species as controls were saved. PCR for ctrA and crgA genes were then run on these bacteria to determine whether they possessed these genes. Results: Five N. meningitidis that had been missed by the first round of culture were identified. Seventy-five other colonies of neisserial species were isolated. N. subflava (n=40) were the most common. Nine (12 %) were crgA positive but none were ctrA positive. At least one crgA positive colony was found in four of the five different non-meningococcal neisserial species isolated in this study. Conclusion: The crgA gene seems quite common among non-meningococcal neisserial species while ctrA seems to be specific for N. meningitidis