Survival of Neisseria meningitidis outside of the host: environmental effects and differences among strains

Abstract

Neisseria meningitidis is a gram-negative bacterium that lives as a commensal in the human nasopharynx. Meningococci are generally non-invasive, but can invade the nasopharyngeal epithelia and enter the bloodstream causing life-threatening illnesses. It is generally thought that meningococci do not survive for long outside the host, and that transmission requires relatively close contact between hosts. There are some reports, however, that meningococci can survive drying on surfaces, including glass, plastic and cloth. Our examination of N. meningitidis strains dried on glass showed differences in survival of isolates belonging to serogroups B, C and W135, including persistence of Cuban, New Zealand, and Norwegian epidemic strains up to 8 days, depending on temperature and humidity. Survival of a New Zealand epidemic strain isolate NZ98/254 under ambient conditions in the laboratory was greatest in winter suggesting that environmental factors impacted survival. For most isolates, including NZ98/254, survival under controlled conditions at 30 °C was greater at 22% than 30% relative humidity. There were also some differences in survival between carriage and invasive strains. The results suggest that N. meningitidis could be transmitted through contact with surfaces outside the host, potentially including contact through shared drinking vessels.

Keywords: Neisseria meningitidis; Meningococcus; environmental survival.; fomite.

Fig. 1.

Survival of isolate NZ98/254 on glass under ambient conditions of temperature and humidity in the laboratory. Data points are means of 22 experiments carried out over a 12-month period. Mean survival at zero time immediately after drying was 23·6 ± 8·6% of initial inoculations, followed by approximately 70% further loss at 4 h, 94% loss at 24 h and further loss until viable organisms were not recovered at 100 h. Error bars represent standard deviations, which are large due to seasonal variation in survival (Fig. 2).

Fig. 2.

Seasonal variation in the survival of strain NZ98/254. Results are means for the 22 experiments: spring n = 5, summer n = 4, autumn n = 7, winter n = 6. The y-axis indicates the death rate ( There were significant differences in survival between winter and summer (P = 0·010) and winter and spring (P = 0·031). In both cases, survival was higher in the winter. Differences were not significant between spring and autumn (P = 1·000) or between spring and summer (P = 0·190).