Bacteria can enter the<unk>  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<unk>  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). Gram positive bacteremia Gram positive bacteria are an increasingly important cause of bacteremia. Staphylococcus, streptococcus, and enterococcus species are the most important and most common species of gram-positive bacteria that can enter the<unk> . These bacteria are normally found on the skin or in the gastrointestinal tract. 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. Skin ulceration or wounds, respiratory tract<unk> , 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. There are many different types of streptococcal species that can cause bacteremia. Group A streptococcus (GAS) typically causes bacteremia from skin and soft tissue<unk> . Group B streptococcus is an important cause of bacteremia in neonates, often immediately following birth. Viridans streptococci species are normal bacterial flora of the mouth. Viridans strep can cause temporary bacteremia after eating, toothbrushing, or flossing. More severe bacteremia can occur following dental procedures or in patients receiving chemotherapy. Finally, streptococcus bovis is a common cause of bacteremia in patients with colon cancer. 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<unk>  and surgical wounds are all risk factors for developing bacteremia from enterococcal species. Resistant enterococcal species can cause bacteremia in patients who have had long hospital stays or frequent antibiotic use in the past (see antibiotic misuse). Gram negative bacteremia 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<unk>  from<unk>  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<unk>  Other organisms that can cause community-acquired bacteremia include Pseudomonas aeruginosa, Klebsiella pneumoniae, and Proteus mirabilis. Salmonella<unk>  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<unk> . 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. Bacteremia risk factors There are several risk factors that increase the likelihood of developing bacteremia from any type of bacteria. These include: * HIV<unk> * Diabetes Mellitus * Chronic hemodialysis * Solid organ transplant * Stem cell transplant * Treatment with glucocorticoids * Liver failure * Asplenia
Bloodstream infections
Mouth infection
Lower gastrointestinal bleeding
Gastrointestinal bleeding
Skin infection
Internal bleeding
Gastrointestinal pathology
Haemobilia