泌尿道感染患者- 何時須做尿液培養

uncomplicated UTI in women. 
如果沒有抗藥性細菌的危險, 不需要做尿液細菌培養, 抗藥性細菌風險包括過去三個月內
1. 尿曾分離出抗藥菌
2. 住養護中心/住院病患/住長照中心 (但肺炎抗藥性細菌與此無關, 與宿主本身因素有關)
3. 曾使用廣效抗生素(FQ/TMP-SMX/ 3rd cefa)
4. 曾在高抗藥細菌盛行區旅行(印度,以色列,西班牙,墨西哥)


泌尿道感染患者. 何時須做尿液培養
尿培養仍然是診斷UTI的標準。收集的尿液應立即送培養；如果沒有，應冷藏在 4°C。兩種培養技術（浸玻片、瓊脂）被廣泛使用且準確。

2010 年美國傳染病學會 (IDSA) 對女性膀胱炎和腎盂腎炎的共識限制是，對於乾淨捕獲的中流尿液樣本，菌落形成單位 (CFU)/mL 和 10,000 CFU/mL 以上。歷史上，UTI 的定義是基於單個微生物培養物濃度為 100,000 CFU/mL 時的發現。然而，這會漏掉高達 50% 的有症狀感染，因此現在可接受大於 1000 CFU/mL 的較低菌落率。 [ 22 ]

無症狀菌尿的定義仍沿用歷史閾值。女性無症狀菌尿被定義為無症狀個體的尿液培養物（乾淨捕獲或導管插入的標本）生長超過 100,000 CFU/mL。
請注意，恥骨上抽吸培養物中培養的任何數量的尿路病原體均應被視為尿路感染的證據。大約 40% 的腎週膿腫患者進行了無菌尿培養。
單純性尿路感染（膀胱炎）不需要進行尿培養，除非女性經歷過經驗性治療失敗。對懷疑患有上尿路感染或複雜性尿路感染的患者以及初始治療失敗的患者進行尿培養。
如果患者在過去一個月內曾患過尿路感染，那麼復發可能是由同一種微生物引起的。復發代表治療失敗。再感染髮生在 1-6 個月內，通常是由不同的微生物（或同一微生物的血清型）引起的。對再次感染的患者進行尿培養。

如果對未離心的干淨捕獲的中流尿液樣本進行革蘭氏染色顯示每個油浸區域存在 1 個細菌，則代表每毫升尿液中有 10,000 個細菌。革蘭氏染色後以 2000 rpm 離心 5 分鐘並在高倍鏡下檢查的樣本 (5 mL) 將識別出較低的數字。一般來說，革蘭氏染色的敏感性為 90%，特異性為 88%。

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875701/

尿液培養

從單純性膀胱炎到並發膿毒症的複雜性腎盂腎炎，只有通過尿液培養才能絕對準確地診斷尿路感染。尿培養的主要適應症是：
有尿路感染症狀或體徵的患者；
最近治療的尿路感染的隨訪；
拔除留置導尿管；
妊娠期間篩查無症狀菌尿；患有梗阻性尿路病變和瘀血的患者，在使用儀器之前。
尿液標本必須在2小時內立即培養，或者可以通過冷藏或合適的化學添加劑（硼酸鈉）保存。可接受的收集方法有：
仔細清洗後的中流尿液；
通過單次導尿獲得的尿液；
通過恥骨上針抽吸獲得尿液；從封閉式導管引流系統的管子中無菌針吸出尿液。

培養結果取決於發生菌尿的臨床環境。例如，80-90%的急性單純性膀胱炎和急性單純性腎盂腎炎患者的尿液中發現了大腸桿菌。許多鹿角結石患者的尿液中含有分解尿素的變形桿菌。醫院內常見克雷伯氏菌、假單胞菌和腸桿菌感染。除非存在潛在的危險因素，否則金黃色葡萄球菌的存在通常是並發葡萄球菌菌血症的線索。

年輕男性體內的微生物與導致女性單純感染的微生物相似。腸球菌和凝固酶陰性葡萄球菌在老年男性中更為常見；最有可能代表最近的儀器或導管插入術。除了留置導尿管、院內尿路感染或多個抗生素療程後復發感染的患者外，白色念珠菌很少見。儘管可能的微生物和通常的易感模式足以指導單純性尿路感染的初始經驗性治療，但急性細菌性腎盂腎炎和復雜性尿路感染的充分治療需要基於致病細菌及其抗菌敏感性的分離的精確治療。 [13]


Urine Culture


Urine culture remains the criterion standard for the diagnosis of UTI. Collected urine should be sent for culture immediately; if not, it should be refrigerated at 4°C. Two culture techniques (dip slide, agar) are widely used and accurate.
The 2010 Infectious Disease Society of America (IDSA) consensus limits for cystitis and pyelonephritis in women are more than 1000 colony-forming units (CFU)/mL and more than 10,000 CFU/mL, respectively, for clean-catch midstream urine specimens. Historically, the definition of UTI was based on the finding at culture of 100,000 CFU/mL of a single organism. However, this misses up to 50% of symptomatic infections, so the lower colony rate of greater than 1000 CFU/mL is now accepted. [22]
The definition of asymptomatic bacteriuria still uses the historical threshold. Asymptomatic bacteruria in a female is defined as a urine culture (clean-catch or catheterized specimen) growing greater than 100,000 CFU/mL in an asymptomatic individual.
Note that any amount of uropathogen grown in culture from a suprapubic aspirate should be considered evidence of a UTI. Approximately 40% of patients with perinephric abscesses have sterile urine cultures.
An uncomplicated UTI (cystitis) does not require a urine culture unless the woman has experienced a failure of empiric therapy. Obtain a urine culture in patients suspected of having an upper UTI or a complicated UTI, as well in those in whom initial treatment fails.
If the patient has had a UTI within the last month, relapse is probably caused by the same organism. Relapse represents treatment failure. Reinfection occurs in 1-6 months and usually is due to a different organism (or serotype of the same organism). Obtain a urine culture for patients who are reinfected.
If a Gram stain of an uncentrifuged, clean-catch, midstream urine specimen reveals the presence of 1 bacterium per oil-immersion field, it represents 10,000 bacteria/mL of urine. A specimen (5 mL) that has been centrifuged for 5 minutes at 2000 rpm and examined under high power after Gram staining will identify lower numbers. In general, a Gram stain has a sensitivity of 90% and a specificity of 88%.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875701/
Urine culture
The diagnosis of UTI from simple cystitis to complicated pyelonephritis with sepsis can be established with absolute certainty only by cultures of urine. The major indications for urine cultures are:
Patients with symptoms or signs of UTIs;
Follow-up of recently treated UTI;
Removal of indwelling urinary catheter;
Screening for asymptomatic bacteriuria during pregnancy; and
Patients with obstructive uropathy and stasis, before instrumentation.
Urine specimens must be cultured promptly within 2h or can be preserved by refrigeration or a suitable chemical additive (boric acid sodium formate). Acceptable methods of collection are:
Midstream urine after careful washing;
Urine obtained by single catheterization;
Urine obtained by supra pubic needle aspiration; and
Sterile needle aspiration of urine from the tube of a closed catheter drainage system.
Results of cultures depend on the clinical setting in which bacteriuria occurs. For example, E. coli are found in the urine of 80-90% of patients with acute uncomplicated cystitis and acute uncomplicated pyelonephritis. Many patients with staghorn calculi harbour urea-splitting proteus organisms in their urine. Klebsiella, Pseudomonas and Enterobacter infections are commonly acquired in the hospital. The presence of Staphylococcus aureus often is a clue to concomitant Staphylococcal bacteremia, unless an underlying risk factor exists.
Micro-organisms in young men are similar to the organisms that cause uncomplicated infections in women. Enterococci and coagulase-negative staphylococci are more common in elderly men; most likely representing recent instrumentation or catheterization. C. albicans is rarely encountered except in patients with indwelling catheters, nosocomial UTIs or relapsing infections after multiple courses of antibiotics. Although the likely organism and usual susceptible patterns are sufficient to guide initial empiric therapy of uncomplicated UTI, adequate treatment of acute bacterial pyelonephritis and complicated UTIs necessitates precise therapy based on isolation of the causative bacterium and its antimicrobial susceptibility.[13]