True bacteriuria is defined as quantitative culture of bacteria ≥10^5/ml in the middle segment of urine or qualitative culture of bacteria in suprapubic cystocentesis urine on both occasions. The primary cause of true bacteriuria is urinary tract infection. The following diseases are also causes of true bacteriuria: 1. Acute pyelonephritis Acute pyelonephritis (acute pyelonephritis) is an acute purulent inflammation caused by bacterial invasion of the renal pelvis, renal calyces and renal parenchyma. The duration of the disease does not exceed 6 months. 2, chronic pyelonephritis Chronic pyelonephritis is a chronic inflammation caused by bacterial infection of the kidney, the lesion mainly invades the renal interstitium and renal pelvis, calyces tissue. The persistence or recurrence of inflammation leads to damage to the interstitium, renal pelvis, and renal calyces, resulting in scarring and kidney atrophy and dysfunction. Patients may usually only have back pain and/or low fever, and may not have the obvious symptoms of urinary tract infection such as painful urination, frequent urination and urgent urination. Patients with a history of long-term or recurrent urinary tract infections may develop uremia in the late stage. 3, actinomycosis Actinomycosis is a chronic purulent inflammatory disease caused by Actinomyces israeli. According to the modern biological classification, actinomycosis is not a fungus but an anaerobic bacteria. Due to the similarity of the lesions caused by it to mycosis, and in accordance with past custom, actinomycosis is still usually described together with fungal diseases. Actinomyces has a cell wall, its chemical composition is similar to bacteria, no nuclear membrane. Mycobacteria are filamentous, similar to fungi, the thickness of the mycelium is similar to the common rod, generally not more than 1μm in diameter. mycelium branching, can be broken into rod-shaped. There are many kinds of actinomycetes. In the natural world is very widely distributed, air, soil, water sources have actinomycetes exist. A few strains are pathogenic to humans, the most important of which is Actinomyces Israelis. Actinomyces israeli is the normal flora of the human oral cavity in the decay of the parasitic bacteria, in the tooth, trauma or other reasons caused by oral mucosa damage, actinomyces can be invaded by the wound. It can also enter the gastrointestinal or lung through swallowing or inhalation of bacterial material. Therefore, actinomycosis mainly occurs in the cervical face and thoracic and abdominal organs. 4, mycoplasma infection Mycoplasma (mycoplasma) is the smallest microorganism that lives outside the cell. It is a class of prokaryotic cellular microorganisms lacking cell walls, generally between 0.3-0.5um in size, highly polymorphic, with spherical, rod-shaped, filamentous, branched and other forms. It differs from cells and from viruses. It is diverse, widely distributed and causes considerable harm, involving humans, animals, plants and insects in many fields, which adversely affects human health and scientific research. Of the 16 species of mycoplasma isolated from humans, five are pathogenic to humans, namely Mycoplasma pneumoniae (M. pneumoniae), Mycoplasma urealyticum (Ureaplasma urealyticum), Mycoplasma hominis (M. homins), Mycoplasma genitalium (M. genitalium) and Mycoplasma fermentans (M. fermentans). The genus Ureaplasma (ureaplasma) contains bodies such as Mycoplasma urealyticum, Mycoplasma urealyticum and Mycoplasma humanum that are pathogenic to humans. Mycoplasma pneumoniae is the main cause of respiratory tract infections and pneumonia. Mycoplasma urealyticum and Mycoplasma humanum, on the other hand, cause genitourinary tract infections. 5, mycoplasma urinary tract infection Mycoplasma urinary and genital tract infections are called mycoplasma urinary tract infections. Mycoplasma (Mycoplasma) is a group of bacteria and viruses between the smallest known microorganisms that can live independently. Recently, the pathogenicity of Mycoplasma genitalium (MG) has attracted attention.