Upon their activation, macrophages produce superoxide (O2−) and hydrogen peroxide (H2O2). Thus N. meningitidis is likely to encounter oxidative stress during its life cycle. Consequently, an important benefit of genetic transformation to N. meningitidis may be the maintenance of the recombination and repair machinery of the cell that removes oxidative DNA damages such as those caused by reactive oxygen. This is consistent with the more general idea that transformation benefits bacterial pathogens by facilitating repair of DNA damages produced by the oxidative defenses of the host during infection.Meningococci population is extensively diverse genetically, this is due to horizontal gene transfers while in the nasophanrynx. Gene transfer can occur within and between genomes of Neisseria species, and it is the main mechanism of acquiring new traits. This is facilitated by the natural competence of the meningococci to take up foreign DNA. The commensal species of Neisseria can act as a reservoir of genes that can be acquired, for example, this is how capsule switching can occur as a means of hiding from the immune system. An invasive N. meningitidis strain of serogroup C broke out in Nigeria in 2013 - the strain was a new sequence type, ST-10217 determined by multilocus sequence typing. It was determined that a commensal strain of N. meningitidis acquired an 8-kb prophage, the meningococcal disease-associated island (MDAΦ), previously associated with hyper-invasiveness; and the full serogroup C capsule operon, thus becoming a hypervirulent strain.
This illustrates how hypervirulent strains can arise from non-pathgenic strains due to the high propensity of gene transfers and DNA uptake by N. meningitidis. Diagnosis
A small amount of cerebrospinal fluid (CSF) is sent to the laboratory as soon as possible for analysis. The diagnosis is suspected, when Gram-negative diplococci are seen on Gram stain of a centrifuged sample of CSF; sometimes they are located inside white blood cells. The microscopic identification takes around 1–2 hours after specimen arrival in the laboratory.The gold standard of diagnosis is microbiological isolation of N. meningitidis by growth from a sterile body fluid, which could be CSF or blood. Diagnosis is confirmed when the organism has grown, most often on a chocolate agar plate, but also on Thayer-Martin agar. To differentiate any bacterial growth from other species a small amount of a bacterial colony is tested for oxidase, catalase for which all clinically relevant Neisseria show a positive reaction, and the carbohydrates maltose, sucrose, and glucose, in which N. meningitidis will ferment that is, utilize the glucose and maltose. Finally, serology determines the subgroup of the N. meningitidis, which is important for epidemiological surveillance purposes; this may often only be done in specialized laboratories. The above tests take a minimum of 48–72 hours turnaround time for growing the organism, and up to a week more for serotyping.