投稿分類 微生物

主委發表種類: 壁報

投稿標題(中): 藉由MALDI-TOF質譜儀鑑定Eggerthella lenta和Desulfovibrio desulfuricans引起蜂窩組織炎、骨髓炎及血流感染的案例報告

投稿標題(英): A case report of cellulitis, osteomyelitis, and bloodstream Infection caused by Eggerthella lenta and Desulfovibrio desulfuricans identificated with MALDI-TOF mass spectrometer.

投稿摘要(前言): An 88-year-old man was admitted to the hospital with a pressure sore on his right buttock, complicated by cellulitis, necrosis, and osteomyelitis, which had been present for 1-2 weeks. The wound measured approximately 10+ cm in size and extended deep to the bone, with increased turbid discharge. Laboratory data showed WBC:13,200, Hb: 7.9,Plt: 246,000, Cr.:0.85 ,Na/K:131.6/3.85. HS-CRP: 19.5. Blood cultures collected by the emergency department were flagged positive by the BACTEC FX blood culture system in anaerobic medium. The clinical manifestations, together with the laboratory results, indicated a bloodstream infection (BSI) initially derived from the wound infection. During bloodstream infections, rapid adaptation of empirical treatment according to the microorganism identified is essential to decrease mortality. In this case, co-infected bacteraemia with Eggerthella lenta and Desulfovibrio desulfuricans identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry mass spectrometer (MALDI-TOF MS).

投稿摘要(方法): The contents of the positive vial were used to make a smear slide for Gram staining and were subcultured onto chocolate agar, blood agar, and EMB agar, incubated at 35°C in 5% CO2, and onto CDC anaerobic blood agar, incubated anaerobically at 35°C. Using the Sepsityper extraction kit (Bruker Daltonics) for the rapid diagnosis of bacteremia by MALDI-TOF-MS directly from positive blood cultures. Antibiotic susceptibility testing of clinically isolated anaerobic bacteria was performed using the agar dilution technique (CMP MIC Brucella plate).

投稿摘要(結果): Gram staining revealed predominantly curved gram-negative bacilli and a few gram-positive bacilli from the direct blood smear. After 2 days, small translucent colonies appeared on the anaerobic media, while the aerobic plates remained negative. The colonies being identified by MALDI-TOF MS (bioMérieux Vitek MS Prime) as Eggerthella lenta that previously named Eubacterium lentum is an anaerobic, non-spore-forming, gram-positive bacillus. However, there has been no second gram-negative bacillus strain observed growing on the culture medium at present. The plate was reincubated anaerobically for three more days. Therefore, the extraction of the positive blood culture using the Sepsityper kit and the analysis of the extracted pellets by MALDI-TOF MS (Bruker MALDI Biotyper and bioMérieux Vitek MS Prime) were performed. Both MALDI-TOF MS platforms identified the pellets as Desulfovibrio desulfuricans that is an obligate anaerobic, curved, motile, sulphate-reducing, gram-negative bacillus. After a total of 6 days of incubation, two different colony morphologies were observed upon closer inspection. The two bacterial isolates were then subcultured separately and examined for identification and antibiotic susceptibility test. The small gray smooth colonies and the gray-black smooth colonies were identified by MALDI-TOF MS as E. lenta and D. desulfuricans, respectively.
The antibiotic susceptibility profile of the two isolates in this case showed that E. lenta was susceptible to clindamycin, cefmetazole, metronidazole, and ampicillin/sulbactam; intermediate to piperacillin/tazobactam; and resistant to penicillin. In contrast, D. desulfuricans was susceptible to clindamycin and metronidazole; intermediate to cefmetazole; and resistant to penicillin, ampicillin/sulbactam, and piperacillin/tazobactam.

投稿摘要(討論): E. lenta and D. desulfuricans are primarily associated with diseases of the gastrointestinal tract, hepatobiliary tract, and abdominal abscesses, and have previously been described as causing bacteremia. The difference is that this case was caused by a bloodstream co-infection originating from a pressure sore on the right buttock. However, These anaerobic organisms often grow slowly, with D. desulfuricans taking 4 to 7 days to appear on an agar surface. They are difficult to identify and are frequently overlooked due to overgrowth in mixed cultures. Therefore, we employed MALDI-TOF MS identification system, which has shortened the time required to accurately identify these bacteria from positive blood cultures. In conclusion, the rapid Sepsityper protocol is a commercial assay for the quick identification of bacteria in BSI. Effective treatment options for E. lenta and D. desulfuricans co-infection in this case include clindamycin and metronidazole.

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