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The bacterium Clostridioides difficile, commonly known as C. difficile, is a type of bacteria that can cause severe diarrhea and colitis, particularly in hospitalized patients and those who have recently taken antibiotics [1]. One antibiotic that has been used to treat C. difficile infections is tigecycline, which is a broad-spectrum antibiotic that is effective against a wide range of gram-positive and gram-negative bacteria [2]. However, C. difficile has developed resistance to tigecycline in some cases.

There are several reasons why C. difficile may be resistant to tigecycline. One factor is the bacterium's ability to develop resistance to antibiotics through genetic mutations or the acquisition of resistance genes from other bacteria [3]. C. difficile has been shown to have a high rate of genetic diversity, which allows it to adapt to changing environments and develop resistance to antibiotics [4].

Another factor that may contribute to tigecycline resistance in C. difficile is the bacterium's ability to form biofilms, which are complex communities of bacteria that are embedded in a protective matrix of extracellular polymeric substances [5]. Biofilms can make it difficult for antibiotics to penetrate and kill the bacteria within, allowing them to survive and continue to cause infection.

It is worth noting that tigecycline is not a first-line treatment for C. difficile infections, and other antibiotics such as metronidazole and vancomycin are typically used instead [6]. The Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) recommend using fidaxomicin or vancomycin as first-line treatments for C. difficile infections, and tigecycline is not mentioned in their guidelines [7].

In summary, C. difficile may be resistant to tigecycline due to its ability to develop resistance to antibiotics through genetic mutations or the acquisition of resistance genes, as well as its ability to form biofilms. It is important to note that tigecycline is not a first-line treatment for C. difficile infections and other antibiotics are typically used instead.

Sources:

1. Centers for Disease Control and Prevention. (2021). Clostridioides difficile (C. difficile, C. diff) infection. <https://www.cdc.gov/cdiff/index.html>
2. Food and Drug Administration. (2010). Tigecycline (Tygacil) information. <https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/tigecycline-tygacil-information>
3. Spigaglia, P., & Sorio, T. (2014). Antibiotic resistance in Clostridium difficile: mechanisms and clinical implications. Journal of clinical gastroenterology, 48(6), 465-472.
4. He et al. (2010). Genomic diversity of Clostridium difficile. Nature, 464(7288), 533-537.
5. Donelli, G. (2013). Biofilm-related bacterial infections: challenges for therapy. Frontiers in microbiology, 4, 1-14.
6. Centers for Disease Control and Prevention. (2018). Treatment of Clostridioides difficile infection. <https://www.cdc.gov/cdiff/clinical/treatment.html>
7. McDonald et al. (2018). Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA): 2018 Update on Diagnosis, Treatment, and Prevention of Clostridium difficile Infections. Clinical Infectious Diseases, 66(7), e1-e48.