free-living ameba (microscopic unicellular eukaryotic, organisms) most common in soil and water, that can cause rare, but severe infections of the eye, skin, and central nervous system. It can enter the eyes through contact lens use, cuts, or skin wounds or by being inhaled into the lungs. The three diseases caused by Acanthamoeba are:
Acanthamoeba keratitis – An infection of the eye that typically occurs in healthy persons and can result in permanent visual impairment or blindness.
Granulomatous Amebic Encephalitis (GAE) – A serious infection of the brain and spinal cord that typically occurs in persons with a compromised immune system.
Disseminated infection – An infection where the germ enters the body through a single entry point (a cut, wound, or through the nostrils) and then disperses throughout the body. This widespread infection that can affect the skin, sinuses, lungs, and other organs independently or in combination.  It is also more common in persons with a compromised immune system.

bacteria causing anthrax - common disease of livestock and, occasionally, of humans - and the only obligate pathogen (can't survive for long outside of the human body) within the genus Bacillus. it belongs to B.cereus family,  present in many types of soil, sediment and plants.
There are 89 known strains of B. anthracis.

Bacillus species are almost ubiquitous in nature, e.g. in soil, but also occur in extreme environments such as high pH (B. alcalophilus), high temperature (B. thermophilus), or high salt (B. halodurans). B. thuringiensis produces a toxin that can kill insects and thus has been used as insecticide.

Infectious bacteria, intracellular parasite of eukaryotic cells, almost always transmitted by sexual contact with an infected individual. C. trachomatis is the leading cause of sexually transmitted disease worldwide. It is also the leading cause of preventable blindness (caused by a chlamydia infection called trachoma) in the world. C. trachomatis is also one of the major causes of pelvic inflammatory disease (PID) and infertility in women.
Men usually have no symptoms, but infection can cause discharge from the penis, pain and burning during urination, infection or inflammation in the ducts of testicles, and tenderness or pain in the testicles. dysuria, frequency, and mucoid to purulent discharge. Clinical syndromes associated with C. trachomatis include epididymitis, proctitis, conjunctivitis, and Reiter’s syndrome. In women, C. trachomatis may produce no specific symptoms too, at least until the next menstrual period. The most common symptoms are mucopurulent discharge and fragility.  Some women develop salpingitis, endometritis, pelvic inflammatory disease (PID), acute urethral syndrome, bartholinitis, cervicitis, cervical dysplasia, conjunctivitis, perihepatitis, and arthritis. ectopic pregnancy and tubal factor infertility. It is associated with an increased risk for the transmission or acquisition of HIV and is also attributed to be a risk factor for the development of cervical carcinoma.

Bacteria commonly found in the environment - soil, water, sewages - and is responsible for reducing nitrate to nitrite. As an opportunistic pathogen, C. freundii is also responsible for a number of significant infections of the respiratory tract, urinary tract, blood and several other normally sterile sites. It might be also causing systemic body odor in humans. C. freundii represents approximately 29% of all opportunistic infections. It is one of the most common hydrogen sulfide-producing species of bacteria along with Hafnia alvei, Pseudomonas, Citrobacter, Aeromonas, Salmonella, and Escherichia coli 

Firmicute, Citrobacter Bacteria that normally lives in human digestive and urinary  tracts but may also cause infections in some cases. 

C. koseri rarely causes infection in healthy, immunocompetent patients and, thus far, has been considered an opportunistic pathogen. There were reports on infective aortic endocarditis due to C. koseri. It can also occasionally causes meningitis, sepsis, ventriculitis, and cerebritis with 80% frequent multiple brain abscesses in low-birth-weight, immunocompromised neonates.

The pathogenic mechanism is poorly understood. C. koseri may have a unique ability to penetrate, survive, and replicate into vascular endothelial cells and macrophages. Furthermore, it survives in phagolysozomal fusion and replicates within macrophages, which may contribute to the establishment of chronic abscesses

Raised serum concentrations of IgA and IgM to lipopolysaccharide (LPS) of gram-negative enterobacteria, such asPseudomonas aeruginosa, Morganella morganii, Proteus mirabilis, Pseduomonas putida, Citrobacter koseri, and Klebsiella pneumoniae have been reported in CFS patients

Psychological stress alters the gut microbiota towards decreased numbers of Bifidobacteria and Lactobacilli

People with CFS were shown to have higher concentrations of intestinal C. koseri bacteria than normal, which probably leads to higher levels of H2S. Professor Kenny De Meirleir of the Brussels Free University and his team say high levels of H2S caused by an intestinal overgrowth of Gram positive D/L lactate-producing bacteria play a major role in CFS and lead to a series of reactions in your body that leave cells devoid of oxygen and energy.

Epstein-Barr virus (EBV), also known as human herpesvirus 4, is a member of the herpes virus family. It is one of the most common human viruses. Most people get infected with EBV at some point in their lives. 80 - 90% of the adult population have been infected by the virus. EBV spreads most commonly through bodily fluids, primarily saliva. EBV can cause infectious mononucleosis (mono), and other illnesses. 
Like all herpesviruses, the Epstein-Barr virus is relatively large and complex. The virus's structure consists of an envelope, spikes, a core, a capsid and a tegument. All these structures aid in making the virus successful in the infection process and as a means of avoiding detection from our body's immune system.
Most common symptoms of infection are extreme fatigue, fever, rash, sore throat, and swollen lymph nodes.

The invasion and multiplication of microorganisms such as bacteria, viruses, fungi and parasites that leads to subsequent tissue injury and illness through a variety of cellular or toxic mechanisms. ​

Group of genetically-diverse single-stranded RNA viruses comprising the Norwalk virus, which can cause inflammation of the stomach and large intestine lining (gastroenteritis). Also known as Norwalk-like virus, "small, round-structured virus" (SRSV), Spencer flu, "Snow Mountain virus", "winter vomiting bug", and "stomach flu", but the latter refers to a range of viruses and bacteria.
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Norovirus is a very contagious virus that can infect anyone, mainly by person-to-person contact or by contaminated food and water. Norvovirus (NoVs) is classified into at least five types (genogroup I [GI] to genogroup V [GV]) and 34 genotypes. Human NoVs are in GI, GII, and GIV. In addition, NoVs have been detected in pigs (GII), cows (GIII), mice (GV), large carnivores (GIV.2) and dogs (GIV.2) and can spread easily across a group of animals.
The virus causes your stomach or intestines or both to get inflamed. This leads you to have stomach pain, nausea, and diarrhea and to throw up. These symptoms can be serious for some people, especially young children and older adults.