Stool Culture

Stool Culture

Dr. Kiarash Ghazvini Department for bacteriology and virology, Mashhad University of medical Sciences

مهم��ترين ب��اكتري ه��اي بيم��اريزاي روده اي ك��ه • Salmonellaشامل قابل گزارش است

• Shigella sp• Campylobacter• 0157:H7, E. Coli• Yersinia enterocolitica• Clostridium difficile• Vibrios cholera•Aeromonas •Plesiomonas. مي باشد.•

مقدمه

•S. aureus و Candida albicans مي را ت�وان ب�ه تع�داد زي�اد و بص�ورت خ�الص از م���دفوع كس���اني ك���ه آن���تي بيوتي���ك گس�ترده مص�رف مي كنن�د ج�دا نم�ود و

ارزش تشخيصي دارد.

مقدمه

• When a stool specimen is sent to the microbiology laboratory for analysis, the physician must correctly request the appropriate examination and understand the limitations of that test.

• In the United States, stool specimens are most commonly sent for "bacterial culture." For most laboratories, this means culturing for C jejuni and Salmonella and Shigella organisms. If other organisms are suspected, the laboratory must be notified.

در بيم�اران بس�تري ك�ه بع�د از س�ه روز •بس��تري در بيمارس��تان دچ��ار اس��هال

ش�ك نم�ود C. difficileش�ده ان�د باي�د ب�ه و م���دفوع از نظ���ر حض���ور توكس���ين

باكتري بررسي شود.

مقدمه

نمون�ه ت�ازه م�دفوع بايس�تي ح�داكثر • دقيق�ه ب�ه آزمايش�گاه منتق�ل 30ظ�رف

س��اعت آم��اده س��ا�زي و 2و در� ع��رض ك�ش�ت ش�ود. �اگ�ر� زم�ان �انتق�ال و كش�ت بيش �از اين �مق���دار باش���د بايس���تي ن�مو�ن��ه م��دف�ع را �در� مح�ي��ط انتق��ال�ي

( اخ��ذ �و Cary-Blair mediumمناس��ب )انتقال داد.

جمع آوري و انتقال نمونه مدفوع

• Refrigeration must be avoided as much as possible.

• No preservatives can be added to stool samples for bacterial detection. Cary-Blair or other suitable transport

• Stool specimens should be transported to the laboratory soon after collection.

سواب ركت�ال ب�راي تش�خيص و شناس�ايي ب�اكتري •ه�اي بيم�ا�ريزا د�رم�وارد اس�هال ح�اد� ك�افي� اس�ت و�لي نمو�ن�ه مناس�بتر� و انت�خ�ابي نمون�ه� م�دفوع ت�ازه اس�ت.� از�مايش�گا�ه مي ت�وان�د روزا�ن�ه ي�ك نمون�ه م��دفو�ع از ه��ر� بي�م��ار را� پ��ذ�يرش نماي��د� و تك��رار آزم�ا�يش بيش از� دوب�ار� در روز� ب�راي ي�ك بيم�ار ت�وج�يهي ن�دارد. �نمون�ه� م�دفو�عي ك�ه ب�راي �ردي�ابي

ارس��ال مي گردد بايد فاق��د محي��ط C. difficile سم �انتقالي باشد.

جمع آوري و انتقال نمونه مدفوع

مدفوع جم�ع آوري ش�ده ك�ه داراي آل�ودگي •خارجي است

نمونه مدفوع آلوده شده با ادرار •نمون��ه ه��اي ب��دون مشخص��ات و ي��ا داراي •

مشخصات نا مناسبدر تم�ام م�وارد ف�وق بايس�تي بخش و پزش�ك مع�ا�لج ر�ا از ع�دم پ�ذ�يرش �و غ�ير قاب�ل قب�ول ب�و�دن ن�م�ون�ه �مطل�ع� نم�و�د. ت�ا در �ص�ورت ني�از

نم�ونه م�ناسب ا�رسال ش�ود

نمونه هاي غير قابل قبول كه نبايستي پذيرش شود

بر روي محيط كشت مناسب نمونه را •بصورت سه فاز كشت نماييد و پليتها را بمدت پيشنهاد شده در جدول زير در انكوباتور قرار

دهيد..

روش كشت و محيطهاي كشت

محيط كشت انكوباسيونMacConkey Agar (MAC) O2, 35°C x 24 hours

Xylose Lysine Deoxycholate (XLD),Hektoen, Salmonella-Shigella (SS), orDecoxycholate Agar (DCA) -selective for Salmonella

O2, 35°C x 24 hours

Gram Negative Broth or Selenite F -enrichment media for Salmonella

Subcultured after incubation O2, 35°C x 6-8 hours onto XLD, SS or DCA

Sorbitol MacConkey (SMA) O2, 35°C x 24 hours

Campylobacter Agar Microaerophilic, 42°C x 72 hours

محيط كشت انكوباسيونBlood Agar (BA) or

Aeromonas selectiveO2, 35°C x 24 hours

Thiosulfate Citrate – Bile Salts – Sucrose

(TCBS) - selective for Vibrio

O2, 35°C x 48 hours

Yersinia Agar (CIN) O2, 30°C x 72 hours

كشت در صورت درخواست و اعالم پزشك معالج

Campylobacter jejuni

• C. jejuni grows best at 42° C in an atmosphere containing 5% to 10% oxygen. Campylobacter species are therefore considered microaerophilic.

• Many laboratories purchase tanks of gas with an appropriate mixture to provide an atmosphere for culturing this organism.

Campylobacter jejuni

• In settings where this is not practical (e.g., when evaluating an outbreak in an area without immediate access to a laboratory), an acceptable atmosphere can be created with little expense by using a candle jar.

Campylobacter jejuni

• C jejuni has characteristic colonial morphology, described as "running" and "wet-looking"because the colonies seem to run together. Microscopic morphology shows the typical gram-negative, curved rods that look like a seagull'swings.

• This characteristic morphology of the genus Campylobacter differentiates it from P. aeruginosa, which also grows at 42° C and is oxidase positive.

Salmonellae

• Salmonella infections are confirmed by culture

• Organisms are most likely to be recovered from blood cultures of patients suspected of typhoid fever if the specimens are obtained during the first week of the infection.

Salmonellae

• Stool cultures yield the organisms during the third and fourth week of the infection.

• Routine microbiologic media such as sheep blood agar and MacConkey agar, and highly selective enteric media, such as Hektoen enteric (HE) agar and xylose-lysine-deoxycholate (XLD) agar are used for recovery.

• Serotyping should be performed whenever possible.

Shigellae

• Shigellae are fragile organisms that do not survive well outside the host for a long period. These organisms are particularly susceptible to acid pH; therefore stool samples should be processed as soon as they are received in the laboratory .

Shigellae

• Diarrheic stools from patients with suspected shigellosis contain pus and blood, a presentation typical of an invasive agent.

• Bloody stools must be plated as soon as possible on appropriate enteric media.

Escherichia coli

• Diarrheogenic E. coli do not look different on a growth plate from E. coli that do not cause diarrheal disease.

• Diagnosis of diarrheal disease caused by E. coli requires a high index of suspicion from the clinician on the basis of history and physical findings.

Escherichia coli

• In addition, because E. coli are part of the normal fecal flora, special tests are needed to differentiate these pathogens from the routinely isolated nonpathogenic E. coli.

• For example, – many enterohemorrhagic E. coli do not ferment sorbitol. Sorbitol-

negative E. coli can be selected in the laboratory by using a sorbitol plate, such as sorbitol MacConkey agar

– Antisera are also used to screen for specific serotypes.– Enteroinvasive E. coli produce colonies and biochemical

reactions similar to those of Shigella species. Tests to differentiate between these pathogens should be performed.

Yersinia species

• Yersinia sp. grow well at 25° C.

• This characteristic may be used in the laboratory.

• Plating and incubation at this temperature and the use of selective media (e.g., cefsulodin-irgasan-novobiocin [CIN] agar) permit ready isolation of Yersinia organisms.

Yersinia species

• Cold enrichment procedures, such as placing fecal samples on isotonic saline and keeping them at 4° C before the inoculation of selective medium, have increased recovery of the organism.

Vibrio species

• Vibrio sp. requires highly selective medium for maximum recovery. Thiosulfate-citrate-bile salts-sucrose (TCBS) agar inhibits the usual colon flora.

• In addition, TCBS agar differentiates sucrose-fermenting from non-sucrose-fermenting vibrios

كل��ني ب��اكتري ه��ايي ك��ه احتم��ال مي رود بيم�اريزا باش�د را بايس�تي ب�ا كم�ك تس���تهاي بيوش���يميايي شناس���ايي و تع���يين جنس و گون���ه نم���ود. ب���راي ب�اكتري ه�اي بيم�اريزا انج�ام تس�ت آن�تي بي��وگرام ب��ر اس��اس روش اس��تاندارد

ضروري است.

گزارش نتايج

جداسازي و شناسايي باكتري هاي– Salmonella – Shigella sp– Campylobacter– 0157:H7 E. Coli– Yersinia enterocolitica– Vibrios cholera– Aeromonas – Plesiomonas.

با اهميت مي باشد و بايستي گزارش گردد.الزم به ذكر است كه گزارش عدم جداسازي هر يك از باكتري •

هاي فوق نيز بايد اعالم گردد.

Hanging latrine on Meghna River, Nepal