The standard treatment is with a minimum of four weeks of high-dose intravenous penicillin with an aminoglycoside such as gentamicin.

The use of high-dose antibiotics is largely based upon animal models.

Leo Loewe of Brooklyn Jewish Hospital was the first to successfully treat subacute bacterial endocarditis with penicillin. Loewe reported at the time seven cases of subacute bacterial endocarditis in 1944.

High-dose antibiotics are administered by the intravenous route to maximize diffusion of antibiotic molecules into vegetation(s) from the blood filling the chambers of the heart. This is necessary because neither the heart valves nor the vegetations adherent to them are supplied by blood vessels. Antibiotics are typically continued for two to six weeks depending on the characteristics of the infection and the causative microorganisms.

In acute endocarditis, due to the fulminant inflammation empirical antibiotic therapy is started immediately after the blood has been drawn for culture. This usually includes vancomycin and ceftriaxone IV infusions until the microbial identification and susceptibility report with the minimum inhibitory concentration becomes available allowing for modification of the antimicrobial therapy to target the specific microorganism. It should be noted that the routine use of gentamicin to treat endocarditis has fallen out of favor due to the lack of evidence to support its use (except in infections caused by "Enterococcus" and nutritionally variant "streptococci") and the high rate of complications.

In subacute endocarditis, where patient's hemodynamic status is usually stable, antibiotic treatment can be delayed till the causative microorganism can be identified.

The most common organism responsible for infective endocarditis is "Staphylococcus aureus", which is resistant to penicillin in most cases. High rates of resistance to oxacillin are also seen, in which cases treatment with vancomycin is required.

Viridans group "streptococci" and "Streptococcus bovis" are usually highly susceptible to penicillin and can be treated with penicillin or ceftriaxone.

Relatively resistant strains of viridans group "streptococci" and "Streptococcus bovis" are treated with penicillin or ceftriaxone along with a shorter 2 week course of an aminoglycoside during the initial phase of treatment.

Highly penicillin resistant strains of viridans group "streptococci", nutritionally variant "streptococci" like "Granulicatella sp.", "Gemella sp." and "Abiotrophia defectiva", and "Enterococci" are usually treated with a combination therapy consisting of penicillin and an aminoglycoside for the entire duration of 4–6 weeks.

Selected patients may be treated with a relatively shorter course of treatment (2 weeks) with benzyl penicillin IV if infection is caused by viridans group "streptococci" or "Streptococcus bovis" as long as the following conditions are met:

- Endocarditis of a native valve, not of a prosthetic valve

- An MIC ≤ 0.12 mg/l

- Complication such as heart failure, arrhythmia, and pulmonary embolism occur

- No evidence of extracardiac complication like septic thromboembolism

- No vegetations > 5mm in diameter conduction defects

- Rapid clinical response and clearance of blood stream infection

Additionally oxacillin susceptible "Staphylococcus aureus" native valve endocarditis of the right side can also be treated with a short 2 week course of a beta-lactam antibiotic like nafcillin with or without aminoglycosides.

Surgical debridement of infected material and replacement of the valve with a mechanical or bioprosthetic artificial heart valve is necessary in certain situations:

- Patients with significant valve stenosis or regurgitation causing heart failure

- Evidence of hemodynamic compromise in the form of elevated end-diastolic left ventricular or left atrial pressure or moderate to severe pulmonary hypertension

- Presence of intracardiac complications like paravalvular abscess, conduction defects or destructive penetrating lesions

- Recurrent septic emboli despite appropriate antibiotic treatment

- Large vegetations (> 10 mm)

- Persistently positive blood cultures despite appropriate antibiotic treatment

- Prosthetic valve dehiscence

- Relapsing infection in the presence of a prosthetic valve

- Abscess formation

- Early closure of mitral valve

- Infection caused by fungi or resistant Gram negative bacteria.

The guidelines were recently updated by both the American College of Cardiology and the European Society of Cardiology. There was a recent meta-analysis published that showed surgical intervention at 7 days or less is associated with lower mortality .

Infective endocarditis is associated with 18% in-hospital mortality.

The Infectious Disease Society of America (IDSA) recommends treating uncomplicated methicillin resistant staph aureus (MRSA) bacteremia with a 14-day course of intravenous vancomycin. Uncomplicated bacteremia is defined as having positive blood cultures for MRSA, but having no evidence of endocarditis, no implanted prostheses, negative blood cultures after 2–4 days of treatment, and signs of clinical improvement after 72 hrs.

The antibiotic treatment of choice for streptococcal and enteroccal infections differs by species. However, it is important to look at the antibiotic resistance pattern for each species from the blood culture to better treat infections caused by resistant organisms.

The presence of bacteria in the blood almost always requires treatment with antibiotics. This is because there are high mortality rates from progression to sepsis if antibiotics are delayed.

The treatment of bacteremia should begin with empiric antibiotic coverage. Any patient presenting with signs or symptoms of bacteremia or a positive blood culture should be started on intravenous antibiotics. The choice of antibiotic is determined by the most likely source of infection and by the characteristic organisms that typically cause that infection. Other important considerations include the patient's past history of antibiotic use, the severity of the presenting symptoms, and any allergies to antibiotics. Empiric antibiotics should be narrowed, preferably to a single antibiotic, once the blood culture returns with a particular bacteria that has been isolated.

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.

Not all people with heart disease require antibiotics to prevent infective endocarditis. Heart diseases have been classified into high, medium and low risk of developing IE. Those falling into high risk category require IE prophylaxis before endoscopies and urinary tract procedures.

Diseases listed under high risk include:

1. Prior endocarditis

2. Unrepaired cyanotic congenital heart diseases

3. Completely repaired congenital heart disease in their first 6 months

4. Prosthetic heart valves

5. Incompletely repaired congenital heart diseases

6. Cardiac transplant valvulopathy

Following are the antibiotic regimens recommended by the American Heart Association for antibiotic prophylaxis:

In the UK, NICE clinical guidelines no longer advise prophylaxis because there is no clinical evidence that it reduces the incidence of IE and there are negative effects (e.g. allergy and increased bacterial resistance) of taking antibiotics that may outweigh the benefits.

Antibiotics were historically commonly recommended to prevent IE in those with heart problems undergoing dental procedures (known as dental antibiotic prophylaxis). They are less commonly recommended for this procedure.

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.

Common situations in which antibiotics are overused include the following:

- Apparent viral respiratory illness in children should not be treated with antibiotics. If there is a diagnosis of bacterial infection, then antibiotics may be used.

- When children with ear tubes get ear infections, they should have antibiotic eardrops put into their ears to go to the infection rather than having oral antibiotics which are more likely to have unwanted side effects.

- Swimmer's ear should be treated with antibiotic eardrops, not oral antibiotics.

- Sinusitis should not be treated with antibiotics because it is usually caused by a virus, and even when it is caused by a bacteria, antibiotics are not indicated except in atypical circumstances as it usually resolves without treatment.

- Viral conjunctivitis should not be treated with antibiotics. Antibiotics should only be used with confirmation that a patient has bacterial conjunctivitis.

- Older persons often have bacteria in their urine which is detected in routine urine tests, but unless the person has the symptoms of a urinary tract infection, antibiotics should not be used in response.

- Eczema should not be treated with oral antibiotics. Dry skin can be treated with lotions or other symptom treatments.

- The use of topical antibiotics to treat surgical wounds does not reduce infection rates in comparison with non-antibiotic ointment or no ointment at all.

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.

Antibiotic treatment only has a marginal effect on the duration of symptoms, and its use is not recommended except in high-risk patients with clinical complications.

Erythromycin can be used in children, and tetracycline in adults. Some studies show, however, that erythromycin rapidly eliminates "Campylobacter" from the stool without affecting the duration of illness. Nevertheless, children with dysentery due to "C. jejuni" benefit from early treatment with erythromycin. Treatment with antibiotics, therefore, depends on the severity of symptoms. Quinolones are effective if the organism is sensitive, but high rates of quinolone use in livestock means that quinolones are now largely ineffective.

Antimotility agents, such as loperamide, can lead to prolonged illness or intestinal perforation in any invasive diarrhea, and should be avoided. Trimethoprim/sulfamethoxazole and ampicillin are ineffective against "Campylobacter".

The infection is treated with antibiotics. Tetracyclines and chloramphenicol are the drugs of choice for treating patients with psittacosis. Most persons respond to oral therapy doxycycline, tetracycline hydrochloride, or chloramphenicol palmitate. For initial treatment of severely ill patients, doxycycline hyclate may be administered intravenously. Remission of symptoms usually is evident within 48–72 hours. However, relapse can occur, and treatment must continue for at least 10–14 days after fever abates.

The infection is usually self-limiting, and in most cases, symptomatic treatment by liquid and electrolyte replacement is enough in human infections.

Treatment is usually with intravenous antibiotics, analgesia and washout and/or aspiration of the joint. Draining the pus from the joint is important and can be done either by needle (arthrocentesis) or opening the joint surgically (arthrotomy).

Empiric antibiotics for suspected bacteria should be started. This should be based on gram stain of the synovial fluid as well as other clinical findings. General guidelines are as follows:

- Gram positive cocci - vancomycin

- Gram negative cocci - Ceftriaxone

- Gram negative bacilli - Ceftrioxone, cefotaxime, or ceftazidime

- Gram stain negative and immunocompetent - vancomycin

- Gram stain negative and immunocompromised - vancomycin + third generation cephalosphorin

- IV drug use (possible pseudomonas aeruginosa) - ceftazidime +/- an aminoglycoside

Once cultures are available, antibiotics can be changed to target the specific organism.

After a good response to intravenous antibiotics, patients can be switched to oral antibiotics. The duration of oral antibiotics varies, but is generally for 1-4 weeks depending on the offending organism.

In infection of a prosthetic joint, a biofilm is often created on the surface of the prosthesis which is resistant to antibiotics. Surgical debridement is usually indicated in these cases. A replacement prosthesis is usually not inserted at the time of removal to allow antibiotics to clear infection of the region. Patients that cannot have surgery may try long-term antibiotic therapy in order to suppress the infection.

Close follow up with physical exam & labs must be done to make sure patient is no longer feverish, pain has resolved, has improved range of motion, and lab values are normalized.

Due to its rarity, no comprehensive treatment studies on eosinophilic myocarditis have been conducted. Small studies and case reports have directed efforts towards: a) supporting cardiac function by relieving heart failure and suppressing life-threatening abnormal heart rhythms; b) suppressing eosinophil-based cardiac inflammation; and c) treating the underlying disorder. In all cases of symptomatic eosinophilic myocarditis that lack specific treatment regimens for the underlying disorder, available studies recommend treating the inflammatory component of this disorder with non-specific immunosuppressive drugs, principally high-dosage followed by slowly-tapering to a low-dosage maintenance corticosteroid regimens. It is recommended that afflicted individuals who fail this regimen or present with cardiogenic shock be treated with other non-specific immunosuppressive drugs viz., azathioprine or cyclophosphamide, as adjuncts to, or replacements for, corticosteroids. However, individuals with an underlying therapeutically accessible disease should be treated for this disease; in seriously symptomatic cases, such individuals may be treated concurrently with a corticosteroid regimen. Examples of diseases underlying eosinophilic myocarditis that are recommended for treatments directed at the underlying disease include:

- Infectious agents: specific drug treatment of helminth and protozoan infections typically takes precedence over non-specific immunosuppressive therapy, which, if used without specific treatment, could worsen the infection. In moderate-to-severe cases, non-specific immunosuppression is used in combination with specific drug treatment.

- Toxic reactions to ingested agents: discontinuance of the ingested agent plus corticosteroids or other non-specific immunosuppressive regimens.

- Clonal eosinophilia caused by mutations in genes that are highly susceptible to tyrosine kinase inhibitors such as "PDGFRA", "PDGFRB", or possibly "FGFR1": first generation tyrosine kinase inhibitors (e.g. imatinib) are recommended for the former two mutations; a later generation tyrosine kinase inhibitors, ponatinib, alone or combined with bone marrow transplantation, may be useful for treating the FGFR1 mutations.

- Clonal hypereosinophilia due to mutations in other genes or primary malignancies: specific treatment regimens used for these pre-malignant or malignant diseases may be more useful and necessary than non-specific immunosuppression.

- Allergic and autoimmune diseases: non-specific treatment regimens used for these diseases may be useful in place of a simple corticosteroid regimen. For example, eosinophilic granulomatosis with polyangiitis can be successfully treated with mepolizumab.

- Idiopathic hypereosinphilic syndrome and lymphocyte-variant hypereosinophilia: corticosteroids; for individuals with these hypereosinophilias that are refractory to or break through corticosteroid therapy and individuals requiring corticosteroid-sparing therapy, recommended alternative drug therapies include hydroxyurea, Pegylated interferon-α, and either one of two tyrosine kinase inhibitors viz., imatinib and mepolizumab).

Nocardiosis requires at least 6 months of treatment, preferably with trimethoprim/sulfamethoxazole or high doses of sulfonamides. In patients who do not respond to sulfonamide treatment, other drugs, such as ampicillin, erythromycin, or minocycline, may be added.

Treatment also includes surgical drainage of abscesses and excision of necrotic tissue. The acute phase requires complete bed rest; as the patient improves, activity can increase.

A new combination drug therapy (sulfonamide, ceftriaxone, and amikacin) has also shown promise.

A boil may clear up on its own without bursting, but more often it will need to be opened and drained. This will usually happen spontaneously within two weeks. Regular application of a warm moist compress, both before and after a boil opens, can help speed healing. The area must be kept clean, hands washed after touching it, and any dressings disposed of carefully, in order to avoid spreading the bacteria. A doctor may cut open or "lance" a boil to allow it to drain, but squeezing or cutting should not be attempted at home, as this may further spread the infection. Antibiotic therapy may be recommended for large or recurrent boils or those that occur in sensitive areas (such as the groin, breasts, armpits, around or in the nostrils, or in the ear). Antibiotics should not be used for longer than one month, with at least two months (preferably longer) between uses, otherwise it will lose its effectiveness. If the patient has chronic (more than two years) boils, removal by plastic surgery may be indicated.

Furuncles at risk of leading to serious complications should be incised and drained if antibiotics or steroid injections are not effective. These include furuncles that are unusually large, last longer than two weeks, or occur in the middle of the face or near the spine. Fever and chills are signs of sepsis and indicate immediate treatment is needed.

Staphylococcus aureus has the ability to acquire antimicrobial resistance easily, making treatment difficult. Knowledge of the antimicrobial resistance of "S. aureus" is important in the selection of antimicrobials for treatment.

Most healthy people clear the infection without treatment, but in 5 to 14 percent of individuals, the organisms disseminate and infect the liver, spleen, eye, or central nervous system. Although some experts recommend not treating typical CSD in immunocompetent patients with mild to moderate illness, treatment of all patients with antimicrobial agents (Grade 2B) is suggested due to the probability of disseminated disease. The preferred antibiotic for treatment is azithromycin since this agent is the only one studied in a randomized controlled study.

Azithromycin is preferentially used in pregnancy to avoid the teratogenic side effects of doxycycline. However, doxycycline is preferred to treat "B. henselae" infections with optic neuritis due to its ability to adequately penetrate the tissues of the eye and central nervous system.

Subacute bacterial endocarditis (also called endocarditis lenta) is a type of endocarditis (more specifically, infective endocarditis). Subacute bacterial endocarditis can be considered a form of type III hypersensitivity.

When proper treatment is provided for patients with rat-bite fever, the prognosis is positive. Without treatment, the infection usually resolves on its own, although it may take up to a year to do so. A particular strain of rat-bite fever in the United States can progress and cause serious complications that can be potentially fatal. Before antibiotics were used, many cases resulted in death. If left untreated, streptobacillary rat-bite fever can result in infection in the lining of the heart, covering over the spinal cord and brain, or in the lungs. Any tissue or organ throughout the body may develop an abscess.

Treatment of acute Q fever with antibiotics is very effective and should be given in consultation with an infectious diseases specialist. Commonly used antibiotics include doxycycline, tetracycline, chloramphenicol, ciprofloxacin, ofloxacin, and hydroxychloroquine. Chronic Q fever is more difficult to treat and can require up to four years of treatment with doxycycline and quinolones or doxycycline with hydroxychloroquine.

Q fever in pregnancy is especially difficult to treat because doxycycline and ciprofloxacin are contraindicated in pregnancy. The preferred treatment is five weeks of co-trimoxazole.

Cat-scratch disease can be primarily prevented by taking flea control measures and washing hands after handling a cat or cat feces; since cats are mostly exposed to fleas when they are outside, keeping cats inside can prevent infestation.

Intensive cardiac care and immunosuppressives including corticosteroids are helpful in the acute stage of the disease. Chronic phase has, mainly debility control and supportive care options.

Antifungals are used for treatment with the specific type and dose depending on the patient's age, immune status, and specifics of the infection. For most adults, the initial treatment is an echinocandin class antifungal (caspofungin, micafungin, or anidulafungin) given intravenously. Fluconazole, amphotericin B, and other antifungals may also be used. Treatment normally continues for two weeks after resolution of signs and symptoms and "Candida" yeasts can no longer can be cultured from blood samples. Some forms of invasive candidiasis, such as infections in the bones, joints, heart, or central nervous system, usually need to be treated for a longer period. Retrospective observational studies suggest that prompt presumptive antifungal therapy (based on symptoms or biomarkers) is effective and can reduce mortality.

Treatment is with penicillin, ampicillin, tetracycline, or co-trimoxazole for one to two years. Any treatment lasting less than a year has an approximate relapse rate of 40%. Recent expert opinion is that Whipple's disease should be treated with doxycycline with hydroxychloroquine for 12 to 18 months. Sulfonamides (sulfadiazine or sulfamethoxazole) may be added for treatment of neurological symptoms.

The treatment of choice is a single dose of benzathine benzylpenicillin given by intramuscular injection, or a five-day to one-week course of either oral penicillin or intramuscular procaine benzylpenicillin. Erythromycin or doxycycline may be given instead to people who are allergic to penicillin. "E. rhusiopathiae" is intrinsically resistant to vancomycin.