What Are Some Causes of Infections?

There are two types of infections. Medical infections refer to local tissues and systemic inflammatory reactions caused by pathogens such as bacteria, viruses, fungi, and parasites invading the human body. A psychological infection is somehow causing the same emotions and actions of others. It is essentially the transmission and communication of emotions and has a great role in interaction.

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Brief introduction to the concept of infection

Hematological symptoms of infection include leukocytosis, anemia, diffuse intravascular coagulation (DIC), and thrombocytopenia.

Infectious diseases usually cause leukocytosis, mainly increased numbers of neutrophils and immature circulating neutrophils. Although the number of early white blood cells did not exceed normal and there were not many mature granulocytes from the bone marrow bank, the release of neutrophils was caused by the direct action of interleukin-1 and interleukin-6 on the neutrophil bank. In chronic infections, the continuous increase in the number of neutrophils appears to be mediated by clone-stimulating factors produced by macrophages, lymphocytes, and other tissues. The worsening of these phenomena can lead to a leukemia-like response, releasing immature white blood cells into the blood circulation. Leukemia-like reactions are characterized by a number of non-malignant leukocytes> 25 ~ 30X109 / L; a response of cytokines produced by healthy bone marrow to trauma and inflammation.

In contrast, certain infections (such as typhoid fever and brucellosis) often produce neutrophil deficiency. In extremely severe infections, the bone marrow may not be able to maintain the number of neutrophils in peripheral blood, resulting in obvious neutrophil loss. Symbol of poor prognosis. Morphological changes (such as Dhle bodies, toxic particles, and vesicle formation) have been observed in neutrophils in patients with sepsis. Eosinophilia is not associated with bacterial infections and is often caused by allergic reactions and parasitic infections.

Anemia, despite sufficient iron ions, can still occur. It may be acute, caused by hemorrhage and red blood cell destruction (such as the condensation set associated with Mycoplasma pneumoniae); it may also be chronic, the iron ion pool in the reticular endothelial system is normal or increased, and the combination of cytosolic iron and whole iron Force reduced.

Gram-negative bacteremia is more common than Gram-positive bacteremia. Serious infections often cause DIC. Tumor necrosis factor may play an important role in promoting the formation of DIC by inducing endothelial cells to express tissue factor prothrombin activity. . DIC is characterized by thrombocytopenia, prolonged clotting time, increased cellulose degradation products, and decreased cellulose levels. Complications include hemorrhage and / or thrombocytosis, in which case bleeding persists despite hypercoagulation and the treatment of the cause is important to reverse DIC.

Pure thrombocytopenia can also be caused by sepsis, and observing the patient's response to treatment can help establish a diagnosis.

Myocardial symptoms caused by infection can increase from tachycardia and cardiac output to heart failure. Although the pulse rate increases in most infectious diseases, the pulse rate does not increase proportionally with the increase in fever, fever, fever-free disease, brucellosis, and dengue fever, and hypotension may occur. However, it is not accompanied by septic shock or enters into a state of shock only. Septic shock is characterized by an increase in cardiac output in the early stage and a decrease in systemic vascular resistance; in the later stage, a decrease in cardiac output and an increase in systemic vascular resistance.

Respiratory symptoms include hyperventilation, often accompanied by significant respiratory alkalosis, followed by a decline in lung function, which can eventually develop into adult dyspnea syndrome and respiratory muscle failure.

Symptoms of the kidney can range from trace proteinuria to acute renal failure. Nitroemia, oliguria, and significant urinary sediment can occur, but are not associated with shock. Shock, azotemia and oliguria are often caused by acute tubular necrosis. In some patients with sepsis, such as subacute bacterial endocarditis, renal insufficiency may be caused by glomerulonephritis; Streptococcus pneumoniae or Legionella pneumophila infection may be caused by tubulointerstitial disease.

Many infectious diseases, even if the infectious factors are not localized in the liver, can cause liver dysfunction. Clinical manifestations are often jaundice (diagnostic value is not great). RBC rupture and liver dysfunction can lead to hyperbilirubinemia. At the cellular level, albumin synthesis is reduced, hepatin, complement, and certain protease inhibitors are increased, and other acute-phase reactants (amyloid A and C-reactive protein) can increase hundreds of times.

During sepsis, upper gastrointestinal bleeding can occur due to an ulcer response, and usually only a small amount of bleeding occurs, and a small number of patients can experience major bleeding.

Although infectious agents do not invade the central nervous system, mental disorders can occur in some serious infections. This phenomenon is more common and serious in the elderly. Symptoms include anxiety, confusion, delirium, stiffness, convulsions, and coma, with clinical images of encephalopathy. The reversal of encephalopathy depends on better control of the primary disease.

Endocrine disorders caused by the infection include increased production of thyroid stimulating hormone, angiotensin, insulin, and glycogen; secondary catabolism of skeletal muscle muscle proteins is enhanced, leading to amino acid oxidation. Long-term infection can lead to muscle wasting and bone decalcification. Although too much corticosteroids can inhibit the inflammatory response and cellular immunity, an increase in adrenocortical hormone secretion is beneficial to the host's ability to resist disease.

It is relatively uncommon in sepsis and hypoglycemia, and its pathogenic mechanism is unclear, which may be related to the loss of liver glycogen reserve and inhibition of new glycogen production. Hypoglycemia may be the earliest sign of infection in people with diabetes, and blood sugar levels are difficult to control.

Causes of infection

The cause can be infectious or non-infectious (such as inflammation, tumors, immune disorders). The heat type can be intermittent, that is, it rises to a normal level after each day, or it is latent fever, that is, it does not Back to normal levels. The elderly's response to heat often declines. In some patients, such as alcoholics, the elderly or children, the fever response can become low in severe infections.

Pyrogen is a substance that causes fever, and has two types: exogenous and endogenous. Exogenous pyrogens are obtained from outside the host, mainly microorganisms and their products and toxins. The more in-depth studies are lipopolysaccharides (often called endotoxins) of gram-negative bacteria and isolation from patients with toxic shock syndrome To Staphylococcus aureus.

Exogenous pyrogens often cause fever by inducing the release of endogenous pyrogens (or endogenous febrile cytokines). Endogenous pyrogens are caused by a variety of cells in the host, especially mononuclear-macrophages. Polypeptides produced by cells. Other cells that produce febrile cytokines are keratinocytes, endothelial cells, B cells, mesangial cells, epithelial cells and glial cells. Endogenous pyrogens (interleukin-1, tumor necrosis factor, interferon, gp130 receptor-activating family: interleukin-6, interleukin-11, leukemia inhibitory factor, ciliary neurotrophic factor, and tumorigenic protein-M) The metabolism of the thermoregulatory body causes fever, and the synthesis of prostaglandin E2 seems to play a key role.

Main manifestations of infection

The main manifestation of infection is that the body's temperature rises above the normal body temperature limit

Oral temperature> 37.8 ° C or rectal temperature> 38.2 ° C or simply body temperature is higher than the normal daily value.

Human body temperature is mainly controlled by the hypothalamus, and body temperature regulation mainly depends on the balance between the loss of peripheral heat and the heat produced by tissues (especially the liver and muscles). In healthy people, the body temperature regulation center maintains the internal organ body temperature at 37 ~ 38 . Raise the given temperature of the thalamus, stimulate the vasomotor center to shrink the blood vessels, return blood from the periphery, reduce heat loss, and eventually increase the body temperature. Tremor, increase heat generation through muscle contraction, may also be excited. The maintenance and production of heat will continue until The temperature of the blood supply to the thalamic neurons reaches a new predetermined point, and then the thalamus maintains this new heat. To re-determine a lower temperature, the process of heat loss can be initiated through sweating and vasodilation.

In the 24 hours of the day, the temperature is lowest in the morning and highest in the afternoon. The temperature variation range, that is, the physiological change rhythm of the temperature is about 0.6 ° C.

Infection diagnosis

Medical history and symptoms can provide important clues to fever of unknown cause. Information such as travel and contact with certain items or animals is also important. For example, some areas in the United States are endemic areas of coccidioidosis and histoplasmosis, and typhoid fever may Have a history of drinking unclean water, brucellosis, a history of working in a meat processing plant, etc.

Fever with unknown causes, the fever type is generally not diagnostic value, but there are exceptions. Fever the next day or fever every 3 days indicates malaria, but the diagnosis also needs to find Plasmodium from the blood smear. In periodic neutropenia Every 21 days, the peripheral neutrophil count drops to a very low level, which often causes infection and fever. For patients with periodic fever, Hodgkin's disease should be suspected.

Comprehensive repetitive physical examination, especially the skin, eyes, nail bed, lymph nodes, heart, abdomen, etc. is important.

Laboratory tests include the isolation and culture of blood and other collectable bodily fluids from bacteria, fungi, viruses, and mycobacteria, full blood cell counts, and antibody titrations (such as typhoid, brucellosis, and certain viral diseases). For some Diagnosis of diseases (such as infective endocarditis) may require multiple blood collections, such as 2 to 3 times a day, for isolation and culture; the diagnosis of protozoan disease (such as malaria) requires a direct blood test and antibody titer Elevated levels can diagnose many infectious diseases, but the interval between the collection of serum samples should be regular. New and more specific immunological and molecular biological techniques (such as PCR) established in recent years may also help diagnosis. In addition, anaerobic bacteria Infection has become a growing concern because it requires anaerobic or hypoxic cultures to find it, especially infections caused by obligate anaerobes (such as tetanus) and microaerobic bacteria (such as H. pylori). More and more attention is being paid.

Non-invasive measures (especially ultrasound, CT and MRI) reduce the need for traumatic treatment. Ultrasound can show cardiac neoplasms and abnormalities of pancreas, liver, kidney and bladder; CT can show abdominal tumors, retroperitoneal, Abnormal sternal and mesenteric lymph nodes can also detect defects in the spleen, kidney, adrenal glands, pancreas, heart, middle diaphragm, and pelvis; radionuclide scanning, especially 111 indium labeled granulocytes, can help locate infection and observe the infection MRI is better than CT in detecting fever of unknown origin, including the nervous system.

Traumatic diagnostic measures are also needed, such as liver, bone marrow or other related parts: skin, pleura, lymph nodes, intestines, muscle biopsy. Biopsy specimens should be subjected to histopathological examination and isolation of bacteria, fungi, viruses and mycobacteria. In In 90% of cases, the diagnosis of fever of unknown origin varies.

Infection infection treatment

There is always a debate on whether fever caused by infectious diseases needs treatment. Experiments have shown that the host's defense mechanism can be strengthened by fever. In this way, fever is beneficial and should not be routinely cooled. However, no clinical study supports fever. Beneficial (except for previous studies of thermotherapy for syphilis). Fever should be treated for children who may have severe illness; fever may increase the need for O2. For adult patients with cardiopulmonary insufficiency, cooling treatment should also be considered. For every 1 ° C increase in body temperature, the consumption of oxygen increases by 13%; for patients with dementia, fever can cause changes in mental state.

Cerebral cyclooxygenase inhibitors are effective at lowering the temperature. Acetaminophen, aspirin, and other NSAIDs are the most commonly used. Although corticosteroids also have a fever-reducing effect, they should not be used only because they have effects on the immune system.

Unexplained fever

Those with rectal temperature 38.3 for 3 weeks or more, and the cause has not been found after a week of comprehensive examination.

The definition of fever of unknown cause is beneficial to retrospective and prospective clinical research, but it should not be absolute. Some people have proposed that the fever time should be 2 weeks, after 3 days of hospitalization or 3 outpatients, no fever cause has been found. The diagnosis should include Thermal observation, detailed medical history and physical examination, laboratory examinations and non-invasive or invasive measures.

Infection by cause

Divided by the types of pathogens: 1 non-specific infections, also known as purulent infections, general infections, the pathogens are mostly purulent bacteria, but the same pathogen can cause a variety of purulent infections, and different pathogens can Cause the same disease. 2 Specific infections are infections caused by specific bacteria such as Mycobacterium tuberculosis and tetanus. Unlike non-specific infections, their clinical manifestations, course changes, and treatment principles and methods have distinct characteristics.

According to the scope of infection: divided into localized and diffuse.

According to the course of disease: acute, subacute, chronic.

Psychological Terminology

Infection is somehow causing the same emotions and actions of others. It is essentially the transmission and communication of emotions and has a great role in interaction. First, infections can change a person's mood. Second, infection can cause people to spontaneously develop a mood that is consistent with the environment and adjust their own physical and mental. Third, infection can improve team affinity and cohesion.