Another form of endocarditis is healthcare-associated endocarditis when the infecting organism is believed to be transmitted in a health care setting like hospital, dialysis unit or a residential nursing home. Nosocomial endocarditis is a form of healthcare associated endocarditis in which the infective organism is acquired during stay in a hospital and it is usually secondary to presence of intravenous catheters, total parenteral nutrition lines, pacemakers, etc.

Finally, the distinction between "native-valve endocarditis" and "prosthetic-valve endocarditis" is clinically important. Prosthetic valve endocarditis can be early ( 1 year following valvular surgery).

- Early prosthetic valve endocarditis is usually due to intraoperative contamination or a postoperative bacterial contamination which is usually nosocomial in nature.

- Late prosthetic valve endocarditis is usually due to community acquired microorganisms.

Prosthetic valve endocarditis is commonly caused by "Staphylococcus epidermidis" as it is capable of growing as a biofilm on plastic surfaces.

The mechanism of subacute bacterial endocarditis could be due to malformed stenotic valves which in the company of bacteremia, become infected, via adhesion and subsequent colonization of the surface area. This causes an inflammatory response, with recruitment of matrix metalloproteinases, and destruction of collagen.

Underlying structural valve disease is usually present in patients before developing subacute endocarditis, and is less likely to lead to septic emboli than is acute endocarditis, but subacute endocarditis has a relatively slow process of infection and, if left untreated, can worsen for up to one year before it is fatal. In cases of subacute bacterial endocarditis, the causative organism (streptococcus viridans) needs a previous heart valve disease to colonize. On the other hand, in cases of acute bacterial endocarditis, the organism can colonize on the healthy heart valve, causing the disease.

It is usually caused by a form of streptococci viridans bacteria that normally live in the mouth ("Streptococcus mutans, mitis, sanguis "or "milleri").

Other strains of streptococci can also cause subacute endocarditis, streptococcus intermedius:

acute and subacute infection ( can causes about 15% of cases pertaining to infective endocarditis). Additional enterococci (urinary tract infections) and coagulase negative staphylococci can also be causative agents.

Diagnosis is made with isolation of "Pasteurella multocida" in a normally sterile site (blood, pus, or cerebrospinal fluid).

Streptococcus species are the cause of opportunistic infections in poultry leading to acute and chronic conditions in affected birds. Disease varies according to the Streptococcal species but common presentations include septicaemia, peritonitis, salpingitis and endocarditis.

Common species affecting poultry include:

- "S. gallinaceus" in broiler chickens

- "S. gallolyticus" which is a pathogen of racing pigeons and turkey poults

- "S. dysgalactiae" in broiler chickens

- "S. mutans" in geese

- "S. pluranimalium" in broiler chickens

- "S. equi subsp. zooepidemicus" in chickens and turkeys

- "S. suis" in psittacine birds

As the infection is usually transmitted into humans through animal bites, antibiotics usually treat the infection, but medical attention should be sought if the wound is severely swelling. Pasteurellosis is usually treated with high-dose penicillin if severe. Either tetracycline or chloramphenicol provides an alternative in beta-lactam-intolerant patients. However, it is most important to treat the wound.

There are several risk factors that increase the likelihood of developing bacteremia from any type of bacteria. These include:

- HIV infection

- Diabetes Mellitus

- Chronic hemodialysis

- Solid organ transplant

- Stem cell transplant

- Treatment with glucocorticoids

- Liver failure

The mortality of the disease in 1909, as recorded in the British Army and Navy stationed in Malta, was 2%. The most frequent cause of death was endocarditis. Recent advances in antibiotics and surgery have been successful in preventing death due to endocarditis. Prevention of human brucellosis can be achieved by eradication of the disease in animals by vaccination and other veterinary control methods such as testing herds/flocks and slaughtering animals when infection is present. Currently, no effective vaccine is available for humans. Boiling milk before consumption, or before using it to produce other dairy products, is protective against transmission via ingestion. Changing traditional food habits of eating raw meat, liver, or bone marrow is necessary, but difficult to implement. Patients who have had brucellosis should probably be excluded indefinitely from donating blood or organs. Exposure of diagnostic laboratory personnel to "Brucella" organisms remains a problem in both endemic settings and when brucellosis is unknowingly imported by a patient. After appropriate risk assessment, staff with significant exposure should be offered postexposure prophylaxis and followed up serologically for six months. Recently published experience confirms that prolonged and frequent serological follow-up consumes significant resources without yielding much information, and is burdensome for the affected staff, who often fail to comply. The side effects of the usual recommended regimen of rifampicin and doxycycline for three weeks also reduce treatment adherence. As no evidence shows treatment with two drugs is superior to monotherapy, British guidelines now recommend doxycycline alone for three weeks and a less onerous follow-up protocol.

Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cells. Complications may include valvular insufficiency, heart failure, stroke, and kidney failure.

The cause is typically a bacterial infection and less commonly a fungal infection. Risk factors include valvular heart disease including rheumatic disease, congenital heart disease, artificial valves, hemodialysis, intravenous drug use, and electronic pacemakers. The bacterial most commonly involved are streptococci or staphylococci. Diagnosis is suspected based on symptoms and supported by blood cultures or ultrasound.

The usefulness of antibiotics following dental procedures for prevention is unclear. Some recommend them in those at high risk. Treatment is generally with intravenous antibiotics. The choice of antibiotics is based on the blood cultures. Occasionally heart surgery is required.

The number of people affected is about 5 per 100,000 per year. Rates, however, vary between regions of the world. Males are affected more often than females. The risk of death among those infected is about 25%. Without treatment it is almost universally fatal.

The pathogenic agent is found everywhere except New Zealand. The bacterium is extremely sustainable and virulent: a single organism is able to cause an infection. The common source of infection is inhalation of contaminated dust, contact with contaminated milk, meat, or wool, and particularly birthing products. Ticks can transfer the pathogenic agent to other animals. Transfer between humans seems extremely rare and has so far been described in very few cases.

Some studies have shown more men to be affected than women, which may be attributed to different employment rates in typical professions.

“At risk” occupations include:

- Veterinary personnel

- Stockyard workers

- Farmers

- Sheep shearers

- Animal transporters

- Laboratory workers handling potentially infected veterinary samples or visiting abattoirs

- People who cull and process kangaroos

- Hide (tannery) workers

Nonbacterial thrombotic endocarditis (NBTE) is most commonly found on previously undamaged valves. As opposed to infective endocarditis, the vegetations in NBTE are small, sterile, and tend to aggregate along the edges of the valve or the cusps. Also unlike infective endocarditis, NBTE does not cause an inflammation response from the body. NBTE usually occurs during a hypercoagulable state such as system-wide bacterial infection, or pregnancy, though it is also sometimes seen in patients with venous catheters. NBTE may also occur in patients with cancers, particularly mucinous adenocarcinoma where Trousseau syndrome can be encountered. Typically NBTE does not cause many problems on its own, but parts of the vegetations may break off and embolize to the heart or brain, or they may serve as a focus where bacteria can lodge, thus causing infective endocarditis.

Another form of sterile endocarditis is termed Libman–Sacks endocarditis; this form occurs more often in patients with lupus erythematosus and is thought to be due to the deposition of immune complexes. Like NBTE, Libman-Sacks endocarditis involves small vegetations, while infective endocarditis is composed of large vegetations. These immune complexes precipitate an inflammation reaction, which helps to differentiate it from NBTE. Also unlike NBTE, Libman-Sacks endocarditis does not seem to have a preferred location of deposition and may form on the undersurfaces of the valves or even on the endocardium.

Gram negative bacterial species are responsible for approximately 24% of all cases of healthcare-associated bacteremia and 45% of all cases of community-acquired bacteremia. In general, gram negative bacteria enter the bloodstream from infections in the respiratory tract, genitourinary tract, gastrointestinal tract, or hepatobiliary system. Gram-negative bacteremia occurs more frequently in elderly populations (65 years or older) and is associated with higher morbidity and mortality in this population.

"E.coli" is the most common cause of community-acquired bacteremia accounting for approximately 75% of cases. E.coli bacteremia is usually the result of a urinary tract infection. Other organisms that can cause community-acquired bacteremia include "pseudomonas aeruginosa", "klebsiella pneumoniae", and "proteus mirabilis". "Salmonella" infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.

Among healthcare-associated cases of bacteremia, gram negative organisms are an important cause of bacteremia in the ICU. Catheters in the veins, arteries, or urinary tract can all create a way for gram negative bacteria to enter the bloodstream. Surgical procedures of the genitourinary tract, intestinal tract, or hepatobiliary tract can also lead to gram negative bacteremia. "Pseudomonas" and "enterobacter" species are the most important causes of gram negative bacteremia in the ICU.

Brucellosis in humans is usually associated with the consumption of unpasteurized milk and soft cheeses made from the milk of infected animals, primarily goats, infected with "Brucella melitensis" and with occupational exposure of laboratory workers, veterinarians, and slaughterhouse workers. Some vaccines used in livestock, most notably "B. abortus" strain 19, also cause disease in humans if accidentally injected. Brucellosis induces inconstant fevers, miscarriage, sweating, weakness, anaemia, headaches, depression, and muscular and bodily pain. The other strains, "B. suis" and "B. canis", cause infection in pigs and dogs, respectively.

The organism should be cultured and antibiotic sensitivity should be determined before treatment is started. Amoxycillin is usually effective in treating streptococcal infections.

Biosecurity protocols and good hygiene are important in preventing the disease.

Vaccination is available against "S. gallolyticus" and can also protect pigeons.

"Bartonella henselae" is a fastidious, intracellular, Gram-negative bacteria.

Carrión's disease, or Oroya fever, or Peruvian wart is a rare infectious disease found only in Peru, Ecuador, and Colombia. It is endemic in some areas of Peru, is caused by infection with the bacterium "Bartonella bacilliformis", and transmitted by sandflies of genus "Lutzomyia".

Cat scratch disease occurs worldwide. Cats are the main reservoir of "Bartonella henselae", and the bacterium is transmitted to cats by the cat flea "Ctenocephalides felis". Infection in cats is very common with a prevalence estimated between 40-60%, younger cats being more commonly infective. Cats usually become immune to the infection, while dogs may be very symptomatic. Humans may also acquire it through flea or tick bites from infected dogs, cats, coyotes, and foxes.

Trench fever, produced by "Bartonella quintana" infection, is transmitted by the human body louse "Pediculus humanus corporis". Humans are the only known reservoir. Thorough washing of clothing may help to interrupt the transmission of infection.

A possible role for ticks in transmission of "Bartonella" species remains to be elucidated; in November 2011, "Bartonella rochalimae", "B. quintana", and "B. elizabethae" DNA was first reported in "Rhipicephalus sanguineus" and "Dermacentor nitens" ticks in Peru.

Members of the genus "Bartonella" are facultative intracellular bacteria, alpha 2 subgroup Proteobacteria. The genus comprises:

Protection is offered by Q-Vax, a whole-cell, inactivated vaccine developed by an Australian vaccine manufacturing company, CSL Limited. The intradermal vaccination is composed of killed "C. burnetii" organisms. Skin and blood tests should be done before vaccination to identify pre-existing immunity, because vaccinating people who already have an immunity can result in a severe local reaction. After a single dose of vaccine, protective immunity lasts for many years. Revaccination is not generally required. Annual screening is typically recommended.

In 2001, Australia introduced a national Q fever vaccination program for people working in “at risk” occupations. Vaccinated or previously exposed people may have their status recorded on the Australian Q Fever Register, which may be a condition of employment in the meat processing industry. An earlier killed vaccine had been developed in the Soviet Union, but its side effects prevented its licensing abroad.

Preliminary results suggest vaccination of animals may be a method of control. Published trials proved that use of a registered phase vaccine (Coxevac) on infected farms is a tool of major interest to manage or prevent early or late abortion, repeat breeding, anoestrus, silent oestrus, metritis, and decreases in milk yield when "C. burnetii" is the major cause of these problems.

Viral cardiomyopathy occurs when viral infections cause myocarditis with a resulting thickening of the myocardium and dilation of the ventricles. These viruses include Coxsackie B and adenovirus, echoviruses, influenza H1N1, Epstein-Barr virus, rubella (German measles virus), varicella (chickenpox virus), mumps, measles, parvoviruses, yellow fever, dengue fever, polio, rabies and the viruses that cause hepatitis A and C.

Cat-scratch disease has a worldwide distribution, however it is a nonreportable disease in humans and therefore public health data on this disease is inadequate. Geographical location, present season and variables associated with cats (such as exposure and degree of flea infestation) all play a factor in the prevalence of Cat-scratch disease within a population. In warmer climates, the incidence of Cat-scratch disease is more prevalent during the fall and winter months. The higher rate of Cat-scratch disease during those months may be attributed to the breeding season for adult cats, which allows for the birth of kittens". B henselae," the bacterium responsible for causing Cat-scratch disease, is more prevalent in younger cats [less than one year old] than it is in adult cats.

To determine recent incidence of Cat-scratch disease in the United States, the Truven Health MarketScan Commercial Claims and Encounters database was analyzed in a case control study from 2005-2013. The database consisted of healthcare insurance claims for employees, their spouses, and their dependents. All participants were under 65 years of age, from all 50 states. The length of the study period was 9 years and was based off 280,522,578 person-years; factors such as year, length of insurance coverage, region, age, and sex were used to calculate the person-years incidence rate to eliminate confounding variables among the entire study population. 13,273 subjects were diagnosed with Cat-scratch disease, both in and outpatient cases were analyzed. The study revealed an incidence rate of 4.5/100,000 outpatient cases of Cat-scratch disease. For inpatient cases, the incidence rate was much lower at 0.19/100,000 population. Incidence of Cat-scratch disease was highest in 2005 among outpatient cases and then slowly declined. The Southern states saw the most significant decrease of incidence overtime. Mountain regions have the lowest incidence of this disease because fleas are not a common vector found in these areas.

Distribution of Cat-scratch disease among children aged 5-9 were of the highest incidence in the analyzed database, followed by woman aged 60-64. Incidence among female patients was higher than that among male patients in all age groups. According to data on social trends, women are more likely to own a cat over men; which supports higher incidence rates of this disease in women. Risk of contracting Cat-scratch disease increases as the number of cats residing in the home increases. The number of pet cats in the United States is estimated to be at 57 million. Due to the large population of cats residing in the United States, the ability of this disease to continue to infect humans is vast. Laboratory diagnosis of Cat-scratch disease has improved in recent years, which may support an increase in incidence of Cat-scratch disease in future populations.

The infections are acquired through rat bites or scratches. It can occur as nosocomial infections (i.e., acquired from hospitals), or due to exposure or close associations with animals preying on rats, mice, squirrels, etc. Sodoku is mostly seen in Asia. The incubation period is 4 to 28 days.

Haverhill fever (or epidemic arthritic erythema) is a form of "rat-bite fever" caused by the bacterium "Streptobacillus moniliformis", an organism common in rats and mice. Symptoms begin to appear two to ten days after a rat bite injury. The illness resembles a severe influenza, with a moderate fever (38-40 °C, or 101-104 °F), chills, joint pain, and a diffuse red rash, located mostly on the hands and feet. The causative organism can be isolated by blood culture, and penicillin is the most common treatment. Treatment is usually quite successful, although the body can clear the infection by itself in most cases. Complications are rare, but can include endocarditis and meningitis.

Despite its name, it can present without being bitten by a rat.

The disease was recognized from an outbreak which occurred in Haverhill, Massachusetts in January, 1926. The organism "S. moniliformis" was isolated from the patients. Epidemiology implicated infection via consumption of milk from one particular dairy.

Coxsackie B virus is spread by contact and epidemics usually occur during warm weather in temperate regions and at any time in the tropics.

The prognosis of eosinophilic myocarditis is anywhere from rapidly fatal to extremely chronic or non-fatal. Progression at a moderate rate over many months to years is the most common prognosis. In addition to the speed of inflammation-based heart muscle injury, the prognosis of eosinophilc myocarditis may be dominated by that of its underlying cause. For example, an underlying malignant cause for the eosinophilia may be survival-limiting.