Helicobacter pylori, previously known as Campylobacter pylori, is a gram-negative, flagellated, helical bacterium. Mutants can have a rod or curved rod shape, and these are less effective. Its helical body is thought to have evolved in order to penetrate the mucous lining of the stomach, helped by its flagella, and thereby establish infection. The bacterium was first identified as the causal agent of gastric ulcers in 1983 by the Australian doctors Barry Marshall and Robin Warren, who obtained the Nobel prize in Medicine for this discovery.
Mycobacterium tuberculosis, also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid. This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear weakly Gram-positive. Acid-fast stains such as Ziehl–Neelsen, or fluorescent stains such as auramine are used instead to identify M. tuberculosis with a microscope. The physiology of M. tuberculosis is highly aerobic and requires high levels of oxygen. Primarily a pathogen of the mammalian respiratory system, it infects the lungs. The most frequently used diagnostic methods for tuberculosis are the tuberculin skin test, acid-fast stain, culture, and polymerase chain reaction.
Mycobacterium is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy in humans. The Greek prefix myco- means 'fungus', alluding to this genus' mold-like colony surfaces. Since this genus has cell walls with a waxy lipid-rich outer layer that contains high concentrations of mycolic acid, acid-fast staining is used to emphasize their resistance to acids, compared to other cell types.
Candida albicans is an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is usually a commensal organism, but it can become pathogenic in immunocompromised individuals under a variety of conditions. It is one of the few species of the genus Candida that cause the human infection candidiasis, which results from an overgrowth of the fungus. Candidiasis is, for example, often observed in HIV-infected patients. C. albicans is the most common fungal species isolated from biofilms either formed on (permanent) implanted medical devices or on human tissue. C. albicans, C. tropicalis, C. parapsilosis, and C. glabrata are together responsible for 50–90% of all cases of candidiasis in humans. A mortality rate of 40% has been reported for patients with systemic candidiasis due to C. albicans. By one estimate, invasive candidiasis contracted in a hospital causes 2,800 to 11,200 deaths yearly in the US. Nevertheless, these numbers may not truly reflect the true extent of damage this organism causes, given new studies indicating that C. albicans can cross the blood–brain barrier in mice.
Mycobacterium leprae is one of the two species of bacteria that cause Hansen's disease (leprosy), a chronic but curable infectious disease that damages the peripheral nerves and targets the skin, eyes, nose, and muscles.
Campylobacter jejuni is a species of pathogenic bacteria that is commonly associated with poultry, and is also often found in animal feces. This species of microbe is one of the most common causes of food poisoning in Europe and in the US, with the vast majority of cases occurring as isolated events rather than mass outbreaks. Active surveillance through the Foodborne Diseases Active Surveillance Network (FoodNet) indicates that about 20 cases are diagnosed each year for each 100,000 people in the US, while many more cases are undiagnosed or unreported; the CDC estimates a total of 1.5 million infections every year. The European Food Safety Authority reported 246,571 cases in 2018, and estimated approximately nine million cases of human campylobacteriosis per year in the European Union. Campylobacter jejuni infections are increasing at an alarming rate in Europe, North America, and Australia. In Africa, Asia, and the Middle East, data indicates that C. jejuni infections are endemic.
Mycobacterium avium subspecies paratuberculosis (MAP) is an obligate pathogenic bacterium in the genus Mycobacterium. It is often abbreviated M. paratuberculosis or M. avium ssp. paratuberculosis. It is the causative agent of Johne's disease, which affects ruminants such as cattle, and suspected causative agent in human Crohn's disease and rheumatoid arthritis. The type strain is ATCC 19698.
Mycobacterium smegmatis is an acid-fast bacterial species in the phylum Actinomycetota and the genus Mycobacterium. It is 3.0 to 5.0 μm long with a bacillus shape and can be stained by Ziehl–Neelsen method and the auramine-rhodamine fluorescent method. It was first reported in November 1884 by Lustgarten, who found a bacillus with the staining appearance of tubercle bacilli in syphilitic chancres. Subsequent to this, Alvarez and Tavel found organisms similar to that described by Lustgarten also in normal genital secretions (smegma). This organism was later named M. smegmatis.
Leptospira is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species. Leptospira was first observed in 1907 in kidney tissue slices of a leptospirosis victim who was described as having died of "yellow fever".
A mycobacteriophage is a member of a group of bacteriophages known to have mycobacteria as host bacterial species. While originally isolated from the bacterial species Mycobacterium smegmatis and Mycobacterium tuberculosis, the causative agent of tuberculosis, more than 4,200 mycobacteriophage have since been isolated from various environmental and clinical sources. 2,042 have been completely sequenced. Mycobacteriophages have served as examples of viral lysogeny and of the divergent morphology and genetic arrangement characteristic of many phage types.
Host tropism is the infection specificity of certain pathogens to particular hosts and host tissues. This explains why most pathogens are only capable of infecting a limited range of host organisms.
Mycobacteroides abscessus is a species of rapidly growing, multidrug-resistant, nontuberculous mycobacteria (NTM) that is a common soil and water contaminant. Although M. abscessus most commonly causes chronic lung infection and skin and soft tissue infection (SSTI), it can also cause infection in almost all human organs, mostly in patients with suppressed immune systems. Amongst NTM species responsible for disease, infection caused by M. abscessus complex are more difficult to treat due to antimicrobial drug resistance.
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract.
Leptospira interrogans is a species of obligate aerobic spirochaete bacteria shaped like a corkscrew with hooked and spiral ends. L. interrogans is mainly found in warmer tropical regions. The bacteria can live for weeks to months in the ground or water. Leptospira is one of the genera of the spirochaete phylum that causes severe mammalian infections. This species is pathogenic to some wild and domestic animals, including pet dogs. It can also spread to humans through abrasions on the skin, where infection can cause flu-like symptoms with kidney and liver damage. Human infections are commonly spread by contact with contaminated water or soil, often through the urine of both wild and domestic animals. Some individuals are more susceptible to serious infection, including farmers and veterinarians who work with animals.
Pathogenomics is a field which uses high-throughput screening technology and bioinformatics to study encoded microbe resistance, as well as virulence factors (VFs), which enable a microorganism to infect a host and possibly cause disease. This includes studying genomes of pathogens which cannot be cultured outside of a host. In the past, researchers and medical professionals found it difficult to study and understand pathogenic traits of infectious organisms. With newer technology, pathogen genomes can be identified and sequenced in a much shorter time and at a lower cost, thus improving the ability to diagnose, treat, and even predict and prevent pathogenic infections and disease. It has also allowed researchers to better understand genome evolution events - gene loss, gain, duplication, rearrangement - and how those events impact pathogen resistance and ability to cause disease. This influx of information has created a need for bioinformatics tools and databases to analyze and make the vast amounts of data accessible to researchers, and it has raised ethical questions about the wisdom of reconstructing previously extinct and deadly pathogens in order to better understand virulence.
Functional Molecular Infection Epidemiology (FMIE) is an emerging area of medicine that entails the study of pathogen genes and genomes in the context of their functional association with the host niches and the complex interactions they trigger within the host immune system to culminate in varied outcomes of the infection. This can also be defined as the correlation of genetic variations in a pathogen or its respective host with a unique function that is important for disease severity, disease progression, or host susceptibility to a particular pathogen. Functional epidemiology implies not only descriptive host-pathogen genomic associations, but rather the interplay between pathogen and host genomic variations to functionally demonstrate the role of the genetic variations during infection.
Shah Mohammad Faruque is a professor and the dean of the School of Environment and Life Sciences at Independent University Bangladesh (IUB). He is widely recognized for his research in Vibrio cholerae, the bacterium which causes the epidemic diarrhoeal disease Cholera. Among other positions, previously he was a professor at BRAC University; director of the Genomics Centre at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), and formerly director of the Centre for Food and Water Borne Diseases in ICDDR,B. His areas of research interest include microbial genomics, bacteriophages, environmental microbiology, ecology, and evolution of bacterial pathogens, particularly those associated with waterborne and foodborne diseases. Faruque is primarily known for his work in genomics, epidemiology and ecology of the cholera pathogen, and its bacteriophages.
Leptospira broomii is a species of Leptospira isolated from humans with leptospirosis. The type strain is 5399T.
Citrobacter rodentium is a Gram-negative species of bacteria first described in 1996. It infects the intestinal tract of rodents.
Mark J. Pallen is a research leader at the Quadram Institute and Professor of Microbial Genomics at the University of East Anglia. In recent years, he has been at the forefront of efforts to apply next-generation sequencing to problems in microbiology and ancient DNA research.
