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.

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

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.

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.

The newborn`s exposure to the maternal vaginal bacterial flora which contains aerobic and anaerobic bacterial flora can lead to the development of anaerobic bacterial infection. These infections include cellulitis of the site of fetal monitoring (caused by "Bacterodes" spp.), bacteremia, aspiration pneumonia (caused by "Bacterodes" spp.), conjunctivitis (caused by clostridia,) omphalitis (caused by mixed flora), and infant botulism. Clostridial species may play a role in necrotizing enterocolitis. Management of these infection necessitates treating of the underlying condition(s) when present, and administration of proper antimicrobial therapy

Condition predisposing to anaerobic infections include: exposure of a sterile body location to a high inoculum of indigenous bacteria of mucous membrane flora origin, inadequate blood supply and tissue necrosis which lower the oxidation and reduction potential which support the growth of anaerobes. Conditions which can lower the blood supply and can predispose to anaerobic infection are: trauma, foreign body, malignancy, surgery, edema, shock, colitis and vascular disease. Other predisposing conditions include splenectomy, neutropenia, immunosuppression, hypogammaglobinemia, leukemia, collagen vascular disease and cytotoxic drugs and diabetes mellitus. A preexisting infection caused by aerobic or facultative organisms can alter the local tissue conditions and make them more favorable for the growth of anaerobes. Impairment in defense mechanisms due to anaerobic conditions can also favor anaerobic infection. These include production of leukotoxins (by "Fusobacterium" spp.), phagocytosis intracellular killing impairments (often caused by encapsulated anaerobes and by succinic acid ( produced by "Bacteroides" spp.), chemotaxis inhibition (by "Fusobacterium, Prevotella" and "Porphyromonas" spp.), and proteases degradation of serum proteins (by Bacteroides spp.) and production of leukotoxins (by "Fusobacterium" spp.).

The hallmarks of anaerobic infection include suppuration, establishment of an abscess, thrombophlebitis and gangrenous destruction of tissue with gas generation. Anaerobic bacteria are very commonly recovered in chronic infections, and are often found following the failure of therapy with antimicrobials that are ineffective against them, such as trimethoprim–sulfamethoxazole (co-trimoxazole), aminoglycosides, and the earlier quinolones.

Some infections are more likely to be caused by anaerobic bacteria, and they should be suspected in most instances. These infections include brain abscess, oral or dental infections, human or animal bites, aspiration pneumonia and lung abscesses, amnionitis, endometritis, septic abortions, tubo-ovarian abscess, peritonitis and abdominal abscesses following viscus perforation, abscesses in and around the oral and rectal areas, pus-forming necrotizing infections of soft tissue or muscle and postsurgical infections that emerge following procedures on the oral or gastrointestinal tract or female pelvic area. Some solid malignant tumors, ( colonic, uterine and bronchogenic, and head and neck necrotic tumors, are more likely to become secondarily infected with anaerobes. The lack of oxygen within the tumor that are proximal to the endogenous adjacent mucosal flora can predispose such infections.

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.

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.

Marantic vegetations are often associated with previous rheumatic fever.

Other risk factors include:

- hypercoagulable states

- malignant cancers, especially mucin-producing adenocarcinomas (most commonly associated with pancreatic adenocarcinomas)

- systemic lupus erythematosus: Referred to as Libman-Sacks endocarditis

- trauma (e.g., catheters)

About 33 million people are affected by rheumatic heart disease with an additional 47 million having asymptomatic damage to their heart valves. As of 2010 globally it resulted in 345,000 deaths, down from 463,000 in 1990.

In Western countries, rheumatic fever has become fairly rare since the 1960s, probably due to the widespread use of antibiotics to treat streptococcus infections. While it has been far less common in the United States since the beginning of the 20th century, there have been a few outbreaks since the 1980s. Although the disease seldom occurs, it is serious and has a case-fatality rate of 2–5%.

Rheumatic fever primarily affects children between ages 5 and 17 years and occurs approximately 20 days after strep throat. In up to a third of cases, the underlying strep infection may not have caused any symptoms.

The rate of development of rheumatic fever in individuals with untreated strep infection is estimated to be 3%. The incidence of recurrence with a subsequent untreated infection is substantially greater (about 50%). The rate of development is far lower in individuals who have received antibiotic treatment. Persons who have suffered a case of rheumatic fever have a tendency to develop flare-ups with repeated strep infections.

The recurrence of rheumatic fever is relatively common in the absence of maintenance of low dose antibiotics, especially during the first three to five years after the first episode. Recurrent bouts of rheumatic fever can lead to valvular heart disease. Heart complications may be long-term and severe, particularly if valves are involved. In countries in Southeast-Asia, sub-saharan Africa, and Oceania, the percentage of people with rheumatic heart disease detected by listening to the heart was 2.9 per 1000 children and by echocardiography it was 12.9 per 1000 children.

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

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

Having more than one risk factor greatly increases risk of septic arthritis.

Most cases of septic arthritis involve only one organism; however, polymicrobial infections can occur, especially after large open injuries to the joint.

- Staphyloccoci

- Staphylococcus aureus - the most common cause in most age groups. Can be caused by skin infection, previously damaged joint, prosthetic joint, or intravenous drug use.

- coagulase-negative staphylococci - usually due to prosthetic joint

- Streptococci - the second most common cause

- Streptococcus pyogenes - a common cause in children under 5

- Streptococcus pneumoniae

- Group B streptococci - a common cause in infants

- Haemophilus influenzae

- Neisseria gonorrhoeae - the most common cause of septic arthritis in young, sexually active adults. Multiple macules or vesicles seen over the trunk are a pathognomonic feature.

- Neisseria meningitidis

- Escherichia coli - in the elderly, IV drug users and the seriously ill

- Pseudomonas aeruginosa - IV drug users or penetrating trauma through the shoe

- M. tuberculosis, Salmonella spp. and Brucella spp. - cause septic spinal arthritis

- Eikenella corrodens - human bites

- Pasteurella multocida, bartonella henselae - animal bites or scratches

- Fungal species - immunocompromised state

- Borrelia burgodorferi - ticks, causes lyme disease

Viruses that may cause adenoiditis include adenovirus, rhinovirus and paramyxovirus. Bacterial causes include Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis and various species of Staphylococcus including Staphylococcus aureus.

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.

Chronic bacterial prostatitis is a bacterial infection of the prostate gland. It should be distinguished from other forms of prostatitis such as acute bacterial prostatitis and chronic pelvic pain syndrome (CPPS).

It is currently believed that bacterial biofilms play an integral role in the harboring of chronic infection by tonsil and adenoid tissue so contributing to recurrent sinusitis and recurrent or persistent ear disease. Also, enlarged adenoids and tonsils may lead to the obstruction of the breathing patterns in children, causing apnea during sleep.

The most common bacteria isolated are Haemophilus influenzae, group A beta-hemolytic Streptococcus, Staphylococcus aureus, Moraxella catarrhalis, and Streptococcus pneumoniea. Heamophilus influenza, Moraxella catarrhalis and Streptococcus pneumonia are the three most resistant pathogens of otitis and rhinosinisitis in children suffering from these diseases.

Skin abscesses are common and have become more common in recent years. Risk factors include intravenous drug use with rates reported as high as 65% in this population. In 2005 in the United States 3.2 million people went to the emergency department for an abscess. In Australia around 13,000 people were hospitalized in 2008 for the disease.

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.

Even without treatment they rarely result in death as they will naturally break through the skin.

Antibiotics can cause severe reactions and add significantly to the cost of care. In the United States, antibiotics and anti-infectives are the leading cause of adverse effect from drugs. In a study of 32 States in 2011, antibiotics and anti-infectives accounted for nearly 24 percent of ADEs that were present on admission, and 28 percent of those that occurred during a hospital stay.

Prescribing by an infectious disease specialist compared with prescribing by a non-infectious disease specialist decreases antibiotic consumption and reduces costs.

Chronic bacterial prostatitis is a relatively rare condition that usually presents with an intermittent UTI-type picture. It is defined as recurrent urinary tract infections in men originating from a chronic infection in the prostate. Symptoms may be completely absent until there is also bladder infection, and the most troublesome problem is usually recurrent cystitis.

Chronic bacterial prostatitis occurs in less than 5% of patients with prostate-related non-BPH lower urinary tract symptoms (LUTS).

Dr. Weidner, Professor of Medicine, Department of Urology, University of Gießen, has stated: "In studies of 656 men, we seldom found chronic bacterial prostatitis. It is truly a rare disease. Most of those were E-coli."