EXPO 40 years BCCM: Pathogens

While many microorganisms have ‘light forces’ and are used in numerous applications of daily life, to the larger public microbes are most commonly associated with infections and diseases.

This relatively small group of disease-causing microorganisms are collectively called “pathogens”. They can pose a threat to humans and animals, as well as plants, leading to destruction of crops!

Discover the "dark forces" of the pathogenic microorganisms!

Bacteria Fungi Mycobacteria




Bacterial infections are a pervasive and significant aspect of human, animal and plant health and the broader field of microbiology. These infections are caused by various types of bacteria and can affect virtually every organ and system in the human body or plant. Understanding bacterial infections is essential for several reasons. 

Firstly, bacterial infections are a leading cause of illness and mortality worldwide, posing substantial challenges to public health. They can range from minor skin infections to life-threatening conditions such as sepsis and pneumonia. 

Secondly, the emergence of antibiotic-resistant bacteria, often referred to as "superbugs," has become a pressing global concern, making the effective treatment of bacterial infections increasingly difficult.

A deeper understanding of bacterial infections is crucial for healthcare professionals, researchers, policymakers, and the general public alike as we strive to combat these microbial threats and safeguard our health.


Ralstonia solanacearum (LMG 2299T) - Tomatoes

Ralstonia solanacearum is a species of bacteria that causes a plant disease known as bacterial wilt. This pathogenic bacterium mainly affects plants in the Solanaceae family, including major crops such as potatoes, tomatoes, peppers and eggplants. The bacteria colonize the xylem, which is responsible for water transport within the plant, leading to water shortage and plant decline. Infected plants show symptoms such as wilting, yellowing leaves and eventually death.


Xanthomonas fragariae (LMG 708) - Strawberries

Xanthomonas fragariae is a species of bacteria that causes a plant disease known as leaf spot disease. The bacteria affects strawberry plants and can cause significant damage to crops and is highly contagious.
Infected plants show angular, water-soaked lesions on the leaves, which later turn brown or black. In severe cases, the leaves may dry up and fall off. The bacteria can also infect other parts of the plant such as the petioles, flower stems and fruit.


Clavibacter sepedonicus (LMG 2889T) - Potatoes

Clavibacter sepedonicusis is a species of bacteria that causes the plant disease known as potato ring rot. Potatoes are particularly affected, leading to significant economic losses in the potato industry. The main symptom of potato ring rot is the presence of dark brown to black rings or arcs on the tuber surface, hence the name "ring rot". These rings can be superficial or penetrate deep into the potato and cause rot and spoilage.


Pseudomonas syringae (LMG 28803T)

Just like Marvel’s Iceman, the bacterium Pseudomonas syringae can freeze water by touching it, even at temperatures above the natural freezing point. P. syringae bacteria live mostly in farm crops, as well as in many other types of plants. To feed themselves, they freeze the tissue of plants in order to easily access their nutrients, which, in turn, can cause great damage to agriculture. In addition, P. syringae have also been found in snowy environments from Europe to Antarctica.



Vibrio cholerae (LMG 21698)

Vibrio cholerae is a comma-shaped species of bacteria that causes the disease cholera in humans. The bacterium was discovered by Italian anatomist Filippo Pacini in 1854, but was not widely known until Robert Koch thirty years later, independently of Pacini, found a way to combat it. After adhesion to the intestinal mucosa, the bacterium causes infection and fluid loss via a toxin. The fluid loss occurs very rapidly and is accompanied by moderate diarrhoea. Untreated, cholera can quickly lead to death; treated, however, there is a good prognosis. Spread of the bacteria is through faeces. These end up in water or seafood, eventually reaching humans.


Vibrio vulnificus (LMG 13545)

Vibrio vulnificus is a species of bacteria commonly found in warm coastal waters. Although it is a natural inhabitant of marine environments, it can also cause infections in humans. Vibrio vulnificus infections in humans usually occur through consumption of raw or inadequately heated seafood, specifically crustaceans. The bacteria can also enter the body through open wounds or cuts when in contact with contaminated water, such as while swimming or handling seafood. Wound infections from Vibrio vulnificus can cause a local infection characterised by redness, swelling, pain and the formation of ulcers. These infections are more common in individuals with pre-existing wounds or a compromised immune system. Vibrio vulnificus infections are relatively rare, but they can be severe for individuals with specific risk factors.


Bordetella pertussis (LMG 14455T)

Bordetella pertussis is a bacterium that causes whooping cough. This respiratory infection affects the upper respiratory tract and does not travel to the bloodstream or pulmonary alveoli. It has an incubation period of 7 to 10 days, after which the first stage is a normal cold. During this phase, the affected person is highly contagious. One to two weeks after this phase, the next phase follows with the characteristic long coughing fits and wheezing. The bacterium is transmitted through saliva droplets and is highly contagious.


Helicobacter pylori (LMG 19449)

Helicobacter pylori is a spiral-shaped bacterium that can be found in the stomach of humans and therefore can survive in a highly acidic environment. In western European countries, the bacterium is found in a small percentage (10-20%), but in less developed countries in much higher percentages (60-90%). For most of the people, the bacterium does not cause symptoms or signs of illness, but in a small percentage it does, especially stomach pain, stomach ulcers and inflammation of the stomach lining and duodenum. The bacterium is also associated with some forms of stomach cancer.


Campylobacter coli (LMG 6440)

Campylobacter coli is a species of bacteria that can cause gastrointestinal diseases in humans. It is one of the leading causes of bacterial foodborne infections worldwide. Campylobacteriosis is the term used to describe disease caused by Campylobacter species, including Campylobacter coli. Campylobacteriosis is usually contracted by consuming contaminated food or water, such as raw or inadequately heated meat and unpasteurised milk. It can also be transmitted through contact with infected animals, for example faeces.
The symptoms of a Campylobacter coli infection usually appear within 2 to 5 days after exposure and may persist for about a week. Common symptoms include diarrhoea, fever, vomiting and severe abdominal cramps.




Fungal infections in humans cover a wide range of conditions, from superficial skin lesions to fatal invasive mycosis. Several dozen fungal species are responsible for most cases, but rare pathogens also occur and about 500 species have been described as infectious agents. Some are globally distributed because they are part of the human flora (such as Candida albicans) or because they are cosmopolitan fungi (such as Aspergillus fumigatus). Others are known only in certain geographical areas and are considered endemic. These include in particular the causative agents of blastomycosis, histoplasmosis or coccidioidomycosis. Finally, some fungal pathogens, such as the multi-resistant yeast Candida auris, are emerging. C. auris was first discovered in Japan in 2009 and quickly conquered other continents. It is currently an alarming problem, especially in the United States where it is responsible for thousands of hospital-acquired infections.


Trichophyton rubrum (IHEM 22170)

Dermatophytes such as Trichophyton rubrum are the causative agents of ringworm (tinea). They are a group of microscopic fungi that are able to grow on the skin of humans and/or mammals, resulting in cutaneous lesions. They are contagious, spreading from human to human or from animal to human. There are several species of dermatophytes. Among them, Trichophyton erinacei is primarily found on hedgehogs. So, the next time you see a hedgehog trapped in your garden, use gloves to free the little animal, not only for its spines but also to avoid contamination by unpleasant fungi.

Superficial mycoses in Belgium: Burden, costs and antifungal drugs consumption.Becker et al., Mycoses (2020)


Aspergillus fumigatus (IHEM 3007)

A huge variety of microorganisms ensures the decomposition of the organic matter, including the mould Aspergillus fumigatus. This fungus is able to grow at elevated temperatures and can be present in high concentrations in composting units. The latter are thus considered as hotspots for the presence of this species. A. fumigatus, however, has a dark side: it is an opportunistic pathogen in patients with a weakened immunity. It is indeed ubiquitous in the environment and can easily grow at 37°C due to its thermotolerance. A. fumigatus infections can be fatal and emerging resistance towards antifungal drugs is alarming. WHO thus considers A. fumigatus as a critical priority pathogen.



Sneezing, nasal congestion, runny nose, itchy throat and eyes are among the symptoms of allergy to fungal spores.
Alternaria and Cladosporium spores are particularly problematic. They are of concern during the summer, when they reach high concentrations in the outdoor air.


Also fungal plant pathogens are extremely dangerous and may cause the loss of crop harvests or, in the most serious cases, the death of the plants. Fungi can also cause an accumulation of toxins within the plants. The toxins produced by some fungi are dangerous for humans and animals.




Wake up, world! There's a silent killer on the loose, and it goes by the name of Mycobacterium tuberculosis complex. These tiny troublemakers are the ultimate foes, responsible for tuberculosis, the world's number one killing infectious disease, only exceeded by COVID-19 in 2020. Researchers and healthcare warriors are joining forces for decades, armed with cutting-edge technology and life-saving treatments. 


Welcome to the world of non-tuberculous mycobacteria (NTM), where things aren't always what they seem! While most mycobacteria mind their own business, some, like the troublemakers Mycobacterium avium, M. abscessus, and M. ulcerans, have a mischievous side. These cunning characters have the incredible ability to seize opportunities and become opportunistic pathogens to both humans and animals. They strike when our defenses are down, causing infections that can range from skin ulcers to chronic lung diseases. These NTM villains may not be as famous as their tuberculosis-causing cousin, but they're definitely ones to watch out for! So, buckle up and dive into the fascinating world of NTM that can unleash big troubles if we're not careful. Stay informed, stay protected, and halt these opportunistic troublemakers!

The Genus Mycobacterium. Rigouts & Cogneau, The Practical handbook of Microbiology (2021)