Due to delay in growth and identification in these cases, patients may be erroneously classified as "culture-negative" endocarditis. Heart side
Endocarditis can also be classified by the side of the heart affected:

People who intravenously inject opioids such as heroin or methamphetamine may introduce infection which can travel to the right side of the heart, classically affecting the tricuspid valve, and most often caused by S. aureus. Regardless of cause, left-sided endocarditis is more common in people who inject IV drugs and people who do not use substances than right-sided endocarditis. Infection setting
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 a stay in a hospital and it is usually secondary to presence of intravenous catheters, total parenteral nutrition lines, pacemakers, etc. Valve type
Finally, the distinction between native-valve endocarditis and prosthetic-valve endocarditis is clinically important. Prosthetic valve endocarditis can be early (< 60 days of valvular surgery), intermediate (60 days to 1 year) or late (> 1 year following valvular surgery). Early prosthetic valve endocarditis is usually due to intraoperative contamination or 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.
Acute infective endocarditis refers to the presence of signs and symptoms of infective endocarditis that are present for days up to six weeks. If these signs and symptoms persist for more than six weeks but less than three months, this is subacute infective endocarditis. Chronic infective endocarditis refers to the presence of such signs and symptoms when they persist for more than three months. Subacute bacterial endocarditis (SBE) is often due to streptococci of low virulence (mainly viridans streptococci) and mild to moderate illness which progresses slowly over weeks and months (>2 weeks) and has low propensity to hematogenously seed extracardiac sites. Acute bacterial endocarditis (ABE) is a fulminant illness over days to weeks (<2 weeks), and is more likely due to Staphylococcus aureus, which has much greater virulence or disease-producing capacity and frequently causes metastatic infection.This classification is now discouraged, because the ascribed associations (in terms of organism and prognosis) were not strong enough to be relied upon clinically. The terms short incubation (meaning less than about six weeks) and long incubation (greater than about six weeks) are preferred. Culture results
Infective endocarditis may also be classified as culture-positive or culture-negative. By far the most common cause of "culture-negative" endocarditis is prior administration of antibiotics.Sometimes microorganisms can take a longer period of time to grow in the culture media, for example Cutibacterium spp. and the HACEK bacteria group. Some organisms are said to be fastidious because they have demanding growth requirements. Some examples include pathogens like Aspergillus species, Brucella species, Coxiella burnetii, Chlamydia species.