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article imageEssential Science: Bacterium mutates into dangerous pathogen

By Tim Sandle     May 1, 2017 in Science
A microbe has moved from a common resident of the throat and nose to become a potentially worrisome sexually transmitted pathogen. The organism is called Neisseria meningitides and it can cause something a bit like gonorrhea.
This week’s Essential Science column turns to medical microbiology and healthcare to take a look at, what might well become, the next ‘bad bug’ or even ‘super bug’. This is a bacterium capable of triggering a sexually transmitted disease. The organism is called Neisseria meningitidis.
Neisseria meningitides
Neisseria meningitides is commonly described as meningococcus. The organism is already of medical concern because it can cause meningitis together with other meningococcal diseases, like meningococcemia (a type of sepsis). Meningitis is a serious infection of the thin lining that surrounds the brain and spinal cord. The most common symptoms are a stiff neck, high fever, sensitivity to light, confusion, headaches and vomiting.
Microscopically, when stained, the bacterium looks like a small, pink coccus. It is round and arranged in pairs (technically a diplococcus). The bacterium is carried by about 10 percent of the adult population and it is normally only isolated from humans. The risk of infection is normally with children and young people, with most cases in Africa and Asia. Infection can be spread via coughing, sneezing, kissing, and so on.
To protect young people from meningitis several vaccines are available to control the disease. As described by the World Health Organization these are: a meningococcal A conjugate vaccine, C conjugate vaccines, tetravalent A, C, Y and W conjugate vaccines and meningococcal polysaccharide vaccines.
A new sexually transmitted disease
The apparent evolution of the organism into a new type of sexually transmitted disease first came to light in 2015. According to Laboratory Roots, a health clinic located in Columbus, Ohio, saw an increase in the number of heterosexual men seeking treatment for urethritis. This is an inflammation of the urethra that causes painful urination.
Early diagnosis suggested this was due to an infection with Neisseria gonorrhoeae, the ‘classic’ disease of gonorrhea. However, laboratory testes eventually showed that the disease was caused by N. meningitidis. This was unexpected and unusual.
Following the first cases the number of incidences in Columbus reached 100 people. This was followed by reported incidences in Indiana, Georgia, and Michigan.
Mutating organism
The signal that the respiratory organism had mutated to become one passed on through sexual contact came through advanced molecular biology testing, made at the Emory University School of Medicine.
CDC scientist working with whole genome sequencing.
CDC scientist working with whole genome sequencing.
U.S. Department of Health & Human Services
The medical researchers concluded that the N. meningitidis isolated in patients had structurally adapted to the urogenital environment. This led to it becoming a new type of sexually transmitted disease (or STD). The structural adaptation takes the form of a loss of a capsule, in that the respiratory form of the disease is encapsulated and the one found in the genital region does not possess a capsule. This is an evolutionary adaptive change, allowing the organism to adhere to the surfaces of mucus. Thus the detection of the organisms in the U.S, is part of what is called a clade. A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor
Common ancestor
What concerns microbiologists is the apparent rapid adaptation of the bacterium, in terms of moving its residence from the respiratory to the reproductive system (the urogenital area), and with introducing a new level of virulence. It is possible that each of the U.S. infections has originated from a common point, perhaps emanating from Columbus, Ohio.
The new strain of N. meningitidis may have acquired genes from N. gonorrhoeae. This led to a genetic modification that has allowed the organism to adapt to a low oxygen environment. For this to happen there needed to have been a locale in the human body within which both types of organism resided.
Although the occurrence of adapted N. meningitides strain is troubling, it can be killed with standard antibiotics. However, this is may not be for the long term given the way N. gonorrhoeae has proved to be resistant to antibiotics. Here researcher Professor Yih-Ling Tzeng, who works at Emory University School of Medicine states: “this clade can readily take up DNA from gonococci and it is not unthinkable that gonococcal antibiotic resistance genes could jump into this clade by gene transfer, if it is to its advantage.”
Iqbal Osman
The new information about the bacterium has been published in the journal Proceedings of the National Academy of Sciences. The research paper is titled “Emergence of a new Neisseria meningitidis clonal complex 11 lineage 11.2 clade as an effective urogenital pathogen.”
Essential Science
Chlamydomonas reinhardtii (green algae)
Chlamydomonas reinhardtii (green algae)
University of Cambridge
This article is part of Digital Journal's regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we delved into biofuels and how a new generation of biofuels was being developed from the harvesting of algae. The week before we considered neuroscience and considered how scientists are using the light and sound methods to study the brain.
More about Bacteria, Infection, Mutation, Sexually transmitted diseases
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