Bloodstream infections | |
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Other names | Blood infection, toxemia, bacteremia, septicemia |
Specialty | Infectious diseases ![]() |
Bloodstream infections (BSIs) are infections of blood caused by blood-borne pathogens. [1] The detection of microbes in the blood (most commonly accomplished by blood cultures [2] ) is always abnormal. A bloodstream infection is different from sepsis, which is characterized by severe inflammatory or immune responses of the host organism to pathogens. [3]
Bacteria can enter the bloodstream as a severe complication of infections (like pneumonia or meningitis), during surgery (especially when involving mucous membranes such as the gastrointestinal tract), or due to catheters and other foreign bodies entering the arteries or veins (including during intravenous drug abuse). [4] Transient bacteremia can result after dental procedures or brushing of teeth. [5]
Bacteremia can have several important health consequences. Immune responses to the bacteria can cause sepsis and septic shock, which, particularly if severe sepsis and then septic shock occurs, have high mortality rates, especially if not treated quickly (though, if treated early, currently mild sepsis can usually be dealt with successfully). [6] Bacteria can also spread via the blood to other parts of the body (which is called hematogenous spread), causing infections away from the original site of infection, such as endocarditis or osteomyelitis.[ citation needed ] Treatment for bacteremia is with antibiotics, and prevention with antibiotic prophylaxis can be given in high risk situations. [7]
Bacteremia is typically transient and is quickly removed from the blood by the immune system. [5]
Bacteremia frequently evokes a response from the immune system called sepsis, which consists of symptoms such as fever, chills, and hypotension. [8] Severe immune responses to bacteremia may result in septic shock and multiple organ dysfunction syndrome , [8] which are potentially fatal.
Based on type of causative microbe, bloodstream infections are of many types:
Type of blood-borne infection | Causative microbe | Description | Examples |
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Bacteremias | Bacteria | Bacteremia, in the strictest sense, refers to presence of viable bacteria in the blood. Asymptomatic bacteremia can occur in normal daily activities such as conducting oral hygiene and after minor medical procedures. In a healthy person, these clinically benign infections are transient and cause no further sequelae. However, when immune response mechanisms fail or become overwhelmed, bacteremia becomes a bloodstream infection that can evolve into many clinical spectrums and is differentiated as septicemia. [9] |
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Viremias | Viruses | Viremia is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to bacteremia , a condition where bacteria enter the bloodstream. [10] The name comes from combining the word "virus" with the Greek word for "blood" (haima). It usually lasts for 4 to 5 days in the primary condition. | |
Fungemias | Fungi | Fungemia is the presence of fungi or yeasts in the blood. The most common type, also known as candidemia, candedemia, or systemic candidiasis , is caused by Candida species; candidemia is also among the most common bloodstream infections of any kind. [11] Infections by other fungi, including Saccharomyces , Aspergillus (as in aspergillemia, also called invasive aspergillosiis) and Cryptococcus , are also called fungemia. It is most commonly seen in immunosuppressed or immunocompromised patients with severe neutropenia, cancer patients, or in patients with intravenous catheters. | Candidemia, aspergillemia (invasive aspergillosis) |
Protozoemia (blood-borne protozoal infections) | Protozoa | Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. These organisms are now classified in the supergroups Excavata, Amoebozoa, Harosa (SAR supergroup), and Archaeplastida. They are usually contracted by either an insect vector or by contact with an infected substance or surface. [12] |
Bacteria can enter the bloodstream in a number of different ways. However, for each major classification of bacteria (gram negative, gram positive, or anaerobic) there are characteristic sources or routes of entry into the bloodstream that lead to bacteremia. Causes of bacteremia can additionally be divided into healthcare-associated (acquired during the process of receiving care in a healthcare facility) or community-acquired (acquired outside of a health facility, often prior to hospitalization).[ citation needed ]
Gram positive bacteria are an increasingly important cause of bacteremia. [13] Staphylococcus, streptococcus, and enterococcus species are the most important and most common species of gram-positive bacteria that can enter the bloodstream. These bacteria are normally found on the skin or in the gastrointestinal tract.[ citation needed ]
Staphylococcus aureus is the most common cause of healthcare-associated bacteremia in North and South America and is also an important cause of community-acquired bacteremia. [14] Skin ulceration or wounds, respiratory tract infections, and IV drug use are the most important causes of community-acquired staph aureus bacteremia. In healthcare settings, intravenous catheters, urinary tract catheters, and surgical procedures are the most common causes of staph aureus bacteremia. [15]
There are many different types of streptococcal species that can cause bacteremia. Group A streptococcus (GAS) typically causes bacteremia from skin and soft tissue infections. [16] Group B streptococcus is an important cause of bacteremia in neonates, often immediately following birth. [17] Viridans streptococci species are normal bacterial flora of the mouth. Viridans strep can cause temporary bacteremia after eating, toothbrushing, or flossing. [17] More severe bacteremia can occur following dental procedures or in patients receiving chemotherapy. [17] Finally, Streptococcus bovis is a common cause of bacteremia in patients with colon cancer. [18]
Enterococci are an important cause of healthcare-associated bacteremia. These bacteria commonly live in the gastrointestinal tract and female genital tract. Intravenous catheters, urinary tract infections and surgical wounds are all risk factors for developing bacteremia from enterococcal species. [19] Resistant enterococcal species can cause bacteremia in patients who have had long hospital stays or frequent antibiotic use in the past (see antibiotic misuse). [20]
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. [21] [22] 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. [23] E.coli is the most common cause of community-acquired bacteremia accounting for approximately 75% of cases. [24] 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. [25] It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages. [26]
Among healthcare-associated cases of bacteremia, gram negative organisms are an important cause of bacteremia in the ICU. [27] Catheters in the veins, arteries, or urinary tract can all create a way for gram negative bacteria to enter the bloodstream. [16] Surgical procedures of the genitourinary tract, intestinal tract, or hepatobiliary tract can also lead to gram negative bacteremia. [16] Pseudomonas and Enterobacter species are the most important causes of gram negative bacteremia in the ICU. [27]
There are several risk factors that increase the likelihood of developing bacteremia from any type of bacteria. [13] [28] These include:
Bacteremia can travel through the blood stream to distant sites in the body and cause infection (hematogenous spread). Hematogenous spread of bacteria is part of the pathophysiology of certain infections of the heart (endocarditis), structures around the brain (meningitis), and tuberculosis of the spine (Pott's disease). Hematogenous spread of bacteria is responsible for many bone infections (osteomyelitis). [30]
Prosthetic cardiac implants (for example artificial heart valves) are especially vulnerable to infection from bacteremia. [31] Prior to widespread use of vaccines, occult bacteremia was an important consideration in febrile children that appeared otherwise well. [32]
Bacteremia is most commonly diagnosed by blood culture, in which a sample of blood drawn from the vein by needle puncture is allowed to incubate with a medium that promotes bacterial growth. [33] If bacteria are present in the bloodstream at the time the sample is obtained, the bacteria will multiply and can thereby be detected.[ citation needed ]
Any bacteria that incidentally find their way to the culture medium will also multiply. For example, if the skin is not adequately cleaned before needle puncture, contamination of the blood sample with normal bacteria that live on the surface of the skin can occur. [34] For this reason, blood cultures must be drawn with great attention to sterile process. The presence of certain bacteria in the blood culture, such as Staphylococcus aureus, Streptococcus pneumoniae , and Escherichia coli almost never represent a contamination of the sample. On the other hand, contamination may be more highly suspected if organisms like Staphylococcus epidermidis or Cutibacterium acnes grow in the blood culture.[ citation needed ]
Two blood cultures drawn from separate sites of the body are often sufficient to diagnose bacteremia. [34] Two out of two cultures growing the same type of bacteria usually represents a real bacteremia, particularly if the organism that grows is not a common contaminant. [34] One out of two positive cultures will usually prompt a repeat set of blood cultures to be drawn to confirm whether a contaminant or a real bacteremia is present. [34] The patient's skin is typically cleaned with an alcohol-based product prior to drawing blood to prevent contamination. [34] Blood cultures may be repeated at intervals to determine if persistent—rather than transient—bacteremia is present. [34]
Prior to drawing blood cultures, a thorough patient history should be taken with particular regard to presence of both fevers and chills, other focal signs of infection such as in the skin or soft tissue, a state of immunosuppression, or any recent invasive procedures. [33]
Ultrasound of the heart is recommended in all those with bacteremia due to Staphylococcus aureus to rule out infectious endocarditis. [35]
Bacteremia is the presence of bacteria in the bloodstream that are alive and capable of reproducing. It is a type of bloodstream infection. [36] Bacteremia is defined as either a primary or secondary process. In primary bacteremia, bacteria have been directly introduced into the bloodstream. [37] Injection drug use may lead to primary bacteremia. In the hospital setting, use of blood vessel catheters contaminated with bacteria may also lead to primary bacteremia. [37] Secondary bacteremia occurs when bacteria have entered the body at another site, such as the cuts in the skin, or the mucous membranes of the lungs (respiratory tract), mouth or intestines (gastrointestinal tract), bladder (urinary tract), or genitals. [38] Bacteria that have infected the body at these sites may then spread into the lymphatic system and gain access to the bloodstream, where further spread can occur. [39]
Bacteremia may also be defined by the timing of bacteria presence in the bloodstream: transient, intermittent, or persistent. In transient bacteremia, bacteria are present in the bloodstream for minutes to a few hours before being cleared from the body, and the result is typically harmless in healthy people. [40] This can occur after manipulation of parts of the body normally colonized by bacteria, such as the mucosal surfaces of the mouth during tooth brushing, flossing, or dental procedures, [41] or instrumentation of the bladder or colon. [36] Intermittent bacteremia is characterized by periodic seeding of the same bacteria into the bloodstream by an existing infection elsewhere in the body, such as an abscess, pneumonia, or bone infection, followed by clearing of that bacteria from the bloodstream. This cycle will often repeat until the existing infection is successfully treated. [36] Persistent bacteremia is characterized by the continuous presence of bacteria in the bloodstream. [36] It is usually the result of an infected heart valve, a central line-associated bloodstream infection (CLABSI), an infected blood clot (suppurative thrombophlebitis), or an infected blood vessel graft. [36] Persistent bacteremia can also occur as part of the infection process of typhoid fever, brucellosis, and bacterial meningitis. Left untreated, conditions causing persistent bacteremia can be potentially fatal. [17]
Bacteremia is clinically distinct from sepsis, which is a condition where the blood stream infection is associated with an inflammatory response from the body, often causing abnormalities in body temperature, heart rate, breathing rate, blood pressure, and white blood cell count. [42]
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. This is especially the case if the sepsis gets worse, and even more if it becomes severe sepsis (where organ damage begins), septic shock (the organ damage continues, which lowers the blood pressure to the point where special drugs are needed to help keep it high enough), or multiple organ dysfunction syndrome (where organ damage can quickly become fatal, even with supportive devices). [27]
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. [23] 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 history of antibiotic use, the severity of the presenting symptoms, and any allergies to antibiotics. [43] Empiric antibiotics should be narrowed, preferably to a single antibiotic, once the blood culture returns with a particular bacteria that has been isolated. [43]
The Infectious Disease Society of America (IDSA) recommends treating uncomplicated methicillin resistant staph aureus (MRSA) bacteremia with a 14-day course of intravenous vancomycin. [44] 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. [44]
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. [13]
The treatment of gram negative bacteremia is also highly dependent on the causative organism. Empiric antibiotic therapy should be guided by the most likely source of infection and the patient's past exposure to healthcare facilities. [45] In particular, a recent history of exposure to a healthcare setting may necessitate the need for antibiotics with pseudomonas aeruginosa coverage or broader coverage for resistant organisms. [45] Extended generation cephalosporins such as ceftriaxone or beta lactam/beta lactamase inhibitor antibiotics such as piperacillin-tazobactam are frequently used for the treatment of gram negative bacteremia. [45]
For healthcare-associated bacteremia due to intravenous catheters, the IDSA has published guidelines for catheter removal. Short term catheters (in place <14 days) should be removed if bacteremia is caused by any gram negative bacteria, staph aureus, enterococci or mycobacteria. [46] Long term catheters (>14 days) should be removed if the patient is developing signs or symptoms of sepsis or endocarditis, or if blood cultures remain positive for more than 72 hours. [46]
Methicillin-resistant Staphylococcus aureus (MRSA) is a group of gram-positive bacteria that are genetically distinct from other strains of Staphylococcus aureus. MRSA is responsible for several difficult-to-treat infections in humans. It caused more than 100,000 deaths worldwide attributable to antimicrobial resistance in 2019.
Septic shock is a potentially fatal medical condition that occurs when sepsis, which is organ injury or damage in response to infection, leads to dangerously low blood pressure and abnormalities in cellular metabolism. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) defines septic shock as a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone. Patients with septic shock can be clinically identified by requiring a vasopressor to maintain a mean arterial pressure of 65 mm Hg or greater and having serum lactate level greater than 2 mmol/L (>18 mg/dL) in the absence of hypovolemia. This combination is associated with hospital mortality rates greater than 40%.
Acute septic arthritis, infectious arthritis, suppurative arthritis, pyogenic arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typically include redness, heat and pain in a single joint associated with a decreased ability to move the joint. Onset is usually rapid. Other symptoms may include fever, weakness and headache. Occasionally, more than one joint may be involved, especially in neonates, younger children and immunocompromised individuals. In neonates, infants during the first year of life, and toddlers, the signs and symptoms of septic arthritis can be deceptive and mimic other infectious and non-infectious disorders.
Infective endocarditis is an infection of the inner surface of the heart (endocardium), usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications may include backward blood flow in the heart, heart failure – the heart struggling to pump a sufficient amount of blood to meet the body's needs, abnormal electrical conduction in the heart, stroke, and kidney failure.
Cefazolin, also known as cefazoline and cephazolin, is a first-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. Specifically it is used to treat cellulitis, urinary tract infections, pneumonia, endocarditis, joint infection, and biliary tract infections. It is also used to prevent group B streptococcal disease around the time of delivery and before surgery. It is typically given by injection into a muscle or vein.
A hospital-acquired infection, also known as a nosocomial infection, is an infection that is acquired in a hospital or other healthcare facility. To emphasize both hospital and nonhospital settings, it is sometimes instead called a healthcare-associated infection. Such an infection can be acquired in a hospital, nursing home, rehabilitation facility, outpatient clinic, diagnostic laboratory or other clinical settings. A number of dynamic processes can bring contamination into operating rooms and other areas within nosocomial settings. Infection is spread to the susceptible patient in the clinical setting by various means. Healthcare staff also spread infection, in addition to contaminated equipment, bed linens, or air droplets. The infection can originate from the outside environment, another infected patient, staff that may be infected, or in some cases, the source of the infection cannot be determined. In some cases the microorganism originates from the patient's own skin microbiota, becoming opportunistic after surgery or other procedures that compromise the protective skin barrier. Though the patient may have contracted the infection from their own skin, the infection is still considered nosocomial since it develops in the health care setting. The term nosocomial infection is used when there is a lack of evidence that the infection was present when the patient entered the healthcare setting, thus meaning it was acquired or became problematic post-admission.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
A boil, also called a furuncle, is a deep folliculitis, which is an infection of the hair follicle. It is most commonly caused by infection by the bacterium Staphylococcus aureus, resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue. Boils are therefore basically pus-filled nodules. Individual boils clustered together are called carbuncles. Most human infections are caused by coagulase-positive S. aureus strains, notable for the bacteria's ability to produce coagulase, an enzyme that can clot blood. Almost any organ system can be infected by S. aureus.
Vancomycin-resistant Staphylococcus aureus (VRSA) are strains of Staphylococcus aureus that have acquired resistance to the glycopeptide antibiotic vancomycin. Bacteria can acquire resistance genes either by random mutation or through the transfer of DNA from one bacterium to another. Resistance genes interfere with the normal antibiotic function and allow bacteria to grow in the presence of the antibiotic. Resistance in VRSA is conferred by the plasmid-mediated vanA gene and operon. Although VRSA infections are uncommon, VRSA is often resistant to other types of antibiotics and a potential threat to public health because treatment options are limited. VRSA is resistant to many of the standard drugs used to treat S. aureus infections. Furthermore, resistance can be transferred from one bacterium to another.
A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis. By culturing the blood, microbes can be identified and tested for resistance to antimicrobial drugs, which allows clinicians to provide an effective treatment.
Peptostreptococcus is a genus of anaerobic, Gram-positive, non-spore forming bacteria. The cells are small, spherical, and can occur in short chains, in pairs or individually. They typically move using cilia. Peptostreptococcus are slow-growing bacteria with increasing resistance to antimicrobial drugs. Peptostreptococcus is a normal inhabitant of the healthy lower reproductive tract of women.
Capnocytophaga canimorsus is a fastidious, slow-growing, Gram-negative rod of the genus Capnocytophaga. It is a commensal bacterium in the normal gingival microbiota of canine and feline species, but can cause illness in humans. Transmission may occur through bites, licks, or even close proximity with animals. C. canimorsus generally has low virulence in healthy individuals, but has been observed to cause severe, even grave, illness in persons with pre-existing conditions. The pathogenesis of C. canimorsus is still largely unknown, but increased clinical diagnoses have fostered an interest in the bacillus. Treatment with antibiotics is effective in most cases, but the most important yet basic diagnostic tool available to clinicians remains the knowledge of recent exposure to canines or felines.
Pseudomonas oryzihabitans is a nonfermenting yellow-pigmented, gram-negative, rod-shaped bacterium that can cause sepsis, peritonitis, endophthalmitis, and bacteremia. It is an opportunistic pathogen of humans and warm-blooded animals that is commonly found in several environmental sources, from soil to rice paddies. They can be distinguished from other nonfermenters by their negative oxidase reaction and aerobic character. This organism can infect individuals that have major illnesses, including those undergoing surgery or with catheters in their body. Based on the 16S RNA analysis, these bacteria have been placed in the Pseudomonas putida group.
Ceftobiprole, sold under the brand name Zevtera among others, is a fifth-generation cephalosporin antibacterial used for the treatment of hospital-acquired pneumonia and community-acquired pneumonia. It is marketed by Basilea Pharmaceutica under the brand names Zevtera and Mabelio. Like other cephalosporins, ceftobiprole exerts its antibacterial activity by binding to important penicillin-binding proteins and inhibiting their transpeptidase activity which is essential for the synthesis of bacterial cell walls. Ceftobiprole has high affinity for penicillin-binding protein 2a of methicillin-resistant Staphylococcus aureus strains and retains its activity against strains that express divergent mecA gene homologues. Ceftobiprole also binds to penicillin-binding protein 2b in Streptococcus pneumoniae (penicillin-intermediate), to penicillin-binding protein 2x in Streptococcus pneumoniae (penicillin-resistant), and to penicillin-binding protein 5 in Enterococcus faecalis.
Ecthyma gangrenosum is a type of skin lesion characterized by vesicles or blisters which rapidly evolve into pustules and necrotic ulcers with undermined tender erythematous border. "Ecthyma" means a pus forming infection of the skin with an ulcer, "gangrenosum" refers to the accompanying gangrene or necrosis. It is classically associated with Pseudomonas aeruginosa bacteremia, but it is not pathognomonic. Pseudomonas aeruginosa is a gram negative, aerobic bacillus.
A staphylococcal infection or staph infection is an infection caused by members of the Staphylococcus genus of bacteria.
Arbekacin (INN) is a semisynthetic aminoglycoside antibiotic which was derived from kanamycin. It is primarily used for the treatment of infections caused by multi-resistant bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Arbekacin was originally synthesized from dibekacin in 1973 by Hamao Umezawa and collaborators. It has been registered and marketed in Japan since 1990 under the trade name Habekacin. Arbekacin is no longer covered by patent and generic versions of the drug are also available under such trade names as Decontasin and Blubatosine.
Staphylococcus capitis is a coagulase-negative species (CoNS) of Staphylococcus. It is part of the normal flora of the skin of the human scalp, face, neck, scrotum, and ears and has been associated with prosthetic valve endocarditis, but is rarely associated with native valve infection.
Staphylococcus is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical (cocci), and form in grape-like clusters. Staphylococcus species are facultative anaerobic organisms.
ESKAPE is an acronym comprising the scientific names of six highly virulent and antibiotic resistant bacterial pathogens including: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. The acronym is sometimes extended to ESKAPEE to include Escherichia coli. This group of Gram-positive and Gram-negative bacteria can evade or 'escape' commonly used antibiotics due to their increasing multi-drug resistance (MDR). As a result, throughout the world, they are the major cause of life-threatening nosocomial or hospital-acquired infections in immunocompromised and critically ill patients who are most at risk. P. aeruginosa and S. aureus are some of the most ubiquitous pathogens in biofilms found in healthcare. P. aeruginosa is a Gram-negative, rod-shaped bacterium, commonly found in the gut flora, soil, and water that can be spread directly or indirectly to patients in healthcare settings. The pathogen can also be spread in other locations through contamination, including surfaces, equipment, and hands. The opportunistic pathogen can cause hospitalized patients to have infections in the lungs, blood, urinary tract, and in other body regions after surgery. S. aureus is a Gram-positive, cocci-shaped bacterium, residing in the environment and on the skin and nose of many healthy individuals. The bacterium can cause skin and bone infections, pneumonia, and other types of potentially serious infections if it enters the body. S. aureus has also gained resistance to many antibiotic treatments, making healing difficult. Because of natural and unnatural selective pressures and factors, antibiotic resistance in bacteria usually emerges through genetic mutation or acquires antibiotic-resistant genes (ARGs) through horizontal gene transfer - a genetic exchange process by which antibiotic resistance can spread.
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