Microbiology
Summary
Clostridioides difficile, formerly known as Clostridium difficile, is a gram-positive bacillus and an obligate anaerobe. This bacterium is a spore-former, making it resistant to various environmental factors. It can be found as part of the normal gut flora in around 5% of the population; however, disruption of the intestinal flora can lead to C. difficile infection. In most cases, this infection is caused by transmission of toxigenic strains, commonly through the fecal-oral route. Factors that contribute to the development of the infection include the presence of toxigenic C. diff strains and recent antibiotic use. Notorious antibiotics linked to C. diff infection include clindamycin, fluoroquinolones, penicillins, and broad-spectrum cephalosporins.
Toxigenic C. diff strains produce two toxins, A and B, which act on colonic mucosal cells, disrupting their cytoskeletons and tight junctions, ultimately leading to fluid shifts and inflammatory responses. This results in the main symptom of high volume watery diarrhea, often accompanied by fever and leukocytosis. In severe cases, toxic megacolon may develop. Diagnosing C. diff infection involves testing stool for toxin-producing strains, using polymerase chain reaction (PCR), or enzyme immunoassay (EIA). Treatment options include oral vancomycin, oral fidaxomicin, and in severe cases, IV metronidazole in addition to oral vancomycin. Fecal microbiota transplant (FMBT) is an alternative therapy for cases with multiple recurrences and antibiotic failure.
Lesson Outline
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FAQs
Clostridioides difficile, or C. diff, is a gram-positive bacillus that is a common cause of nosocomial infections. These infections are hospital-acquired and can be severe, often resulting in diarrhea, pseudomembranous colitis, and even toxic megacolon. C. diff is an obligate anaerobe, and its spores are resistant to environmental conditions, making it prevalent in healthcare settings.
Pseudomembranous colitis is a severe form of colitis caused by the production of toxins by C. diff. These toxins cause inflammation and injury to the colon, resulting in the formation of yellowish plaques and a thick, adherent mucus layer covering the colon's lining. Patients with pseudomembranous colitis often present with severe diarrhea, abdominal pain, and fever.
Bacterial spores play a critical role in the transmission and infection of C. diff. As an obligate anaerobe, C. diff forms spores in response to unfavorable environmental conditions, such as exposure to oxygen. These spores are highly resistant to heat, disinfectants, and other harsh conditions, allowing them to survive on surfaces for extended periods. Spore transmission can occur via contact with contaminated surfaces or healthcare workers' hands, leading to nosocomial infection.
PCR is a molecular diagnostic technique used to amplify and detect specific DNA sequences. In the diagnosis of C. diff infections, PCR is employed to identify the presence of C. diff toxin genes. By detecting the genes responsible for producing the toxins, PCR offers a rapid, sensitive, and specific method for diagnosing C. difficile-associated diarrhea and colitis.
Oral vancomycin is a glycopeptide antibiotic used in the treatment of C. diff infections. It works by inhibiting the synthesis of the bacterial cell wall, ultimately killing the bacteria. Oral vancomycin is often the preferred treatment for severe C. diff infections because of its targeted activity and lower risk of promoting further antibiotic resistance compared to other antibiotics. Moreover, oral vancomycin is minimally absorbed systemically, allowing for high concentrations of the drug in the colon to effectively treat the infection.
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