Improvement of Neisseria gonorrhoeae culture media to enable growth without atmospheric CO2.

Abstract

Bacterial culture is the crucial step in diagnosing Neisseria gonorrhoeae infections and is the gold standard for determining their antimicrobial resistance profile. However, culture of Neisseria spp. can be challenging in resource poor areas, relying on specialist incubators supplying 5% CO2 for growth of the bacteria. Even when such incubators are available, the CO2 to run them may be scarce; there were CO2 shortages during the COVID-19 pandemic, for example. Although culture jars with gas packs or candles can be used, these are inefficient in terms of use of incubator space and researcher time. To achieve simplicity in culturing of N. gonorrhoeae, the standard Oxoid GC base medium, made with the Kelloggs glucose and iron supplements was improved with the addition of 0.75 g/L sodium bicarbonate (NaHCO3), which is inexpensive and really available. This improved media was able to sustain gonococcal growth as well as standard GC media in 5% CO2. Chocolate agar and Thayer-Martin agar with sodium bicarbonate was also developed, with all showing good growth of N. gonorrhoeae without the need for atmospheric CO2.