The prevalence of this atypical lung infection agent is widely underestimated – people are often not even aware that they have it – and many antibiotics cannot effectively treat it; Mycoplasma pneumoniae outbreaks occur every few years. This winter, countries like China, Denmark, France and the Netherlands reported an increase in cases, especially in children.
Mycoplasma pneumoniae, also referred to as the agent of ‘walking pneumonia’, because infected people can often still walk around and go about their everyday activities, is a bacterium that can cause a range of symptoms, from mild cold-like symptoms to severe respiratory distress. The bacterium is a significant cause of respiratory tract infections in humans, mainly among school-aged children and young adults.
Although this bacterium does not have a cell wall which makes it hard to be treated by most antibiotics, it has a remarkable adaptability, and with the recent outbreak among children, it made itself a significant contributor to respiratory illnesses globally, with outbreaks occurring every few years.
According to expert Dr. Michael Beeton, Lecturer in Medical Microbiology at Cardiff Metropolitan University, “Immunity to M. pneumoniae within the population reduces over time, resulting in a population that is more susceptible to infection, and may provide a setting for the start of an epidemic.”
Dr. Beeton, in your opinion, what makes M. pneumoniae unique compared to other respiratory pathogens, and what are the key challenges that microbiologists face in studying and identifying this bacterium?
Michael Beeton: M. pneumoniae is a leading cause of community-acquired pneumonia among school-aged children and young adults. The pneumonia it causes is considered atypical due to the symptoms, how the infection may appear on a chest x-ray as well as not responding to antibiotics in the way a typical bacterium would.
Unlike other common respiratory pathogens where the incubation period can be as short as a few days, the incubation period for M. pneumoniae can be between one to four weeks.
A fascinating property of M. pneumoniae is its ability to cause surges in infection, also known as epidemics, every few years. The exact reason for this is not fully understood, but it is believed to relate to both host and pathogen factors. Immunity to M. pneumoniae within the population reduces over time resulting in a population that is more susceptible to infection and may provide a setting for the start of an epidemic.
Pathogen factors relate to the introduction of a new variant of M. pneumoniae into a population where cross-immunity may not exist and therefore further fuel these epidemics.
A unique property of M. pneumoniae, when compared with many other bacteria, is the absence of a cell wall. The bacterial cell wall is a major target for several antibiotics used to treat bacterial infections, but as this is not present in M. pneumoniae, these antibiotics are rendered useless.
This significantly limits the treatment options to three main classes of antibiotics: macrolides, tetracyclines, and fluoroquinolones. These options are further reduced among young children where tetracyclines and fluoroquinolones are contraindicated due to potential adverse effects, therefore only leaving macrolides. As discussed below, there is a concern relating to the presence of macrolide-resistant M. pneumoniae.
M. pneumoniae can be challenging for microbiologists to isolate and identify in the laboratory. Most human bacterial pathogens can be isolated in the laboratory within a few days using bacteriological media.
In your opinion, what research gaps exist in our current understanding of M. pneumoniae, and what areas should future studies focus on to address these challenges and mitigate associated risks effectively?
Michael Beeton: Future research should focus on several priorities.
Firstly, there needs to be greater connected international surveillance of M. pneumoniae. Currently, we are running the first international prospective surveillance study – The ESCMID Mycoplasma pneumoniae Surveillance (ESGMAC MAPS) study which collates data from laboratories across the globe to understand where M. pneumoniae infections are present and at what levels. We hope to enhance this surveillance by developing the tools for molecular surveillance to understand the types of M. pneumoniae circulating, and how these contribute to past and future epidemics, as well as introduce consistent monitoring of antibiotic resistance.
Secondly, we need to better understand how M. pneumoniae interacts with the host to cause disease: the immune response, which is generated, the duration of this immunity as well as how this immunity protects across M. pneumoniae types.
Finally, efforts should focus on developing a vaccine. Vaccines play a vital role in reducing the spread and severity of disease within a population. We currently do not have a vaccine to protect against M. pneumoniae infection, therefore taking this option off the table.
How does antibiotic resistance impact the treatment of M. pneumoniae, and what strategies can be implemented to address resistance patterns and optimise antibiotic therapy?
Michael Beeton: This depends on where you are in the world. In Europe, resistance to macrolide antibiotics is relatively low and ranges from 1 – 10%. This contrasts with some regions of Asia, where macrolide resistance is consistently reported to be greater than 80%.
With advances and increased use of whole-genome sequencing techniques, a greater breadth of information is available for M. pneumoniae and therefore opens the ability to take a holistic approach to looking for the presence of multiple antibiotic resistance markers.
Asymptomatic carriage of M. pneumoniae is common, especially during epidemic years, and most symptomatic infections are self-limiting and resolve without antibiotic intervention. It is therefore imperative that antibiotics are used sparingly and only when needed, as this aids in slowing the development of resistance.