Is it really so “difficult” for Clostridium difficile to appear?

Is it really so “difficult” for Clostridium difficile to appear?

When I saw this bacterium, the thought came to my mind: there is no wife in wife cake and no fish in fish-flavored pork shreds, so is it really so "difficult" for Clostridium difficile to appear?

Let us learn about what Clostridium difficile is.

Clostridium difficile is widely distributed in soil, various domestic and wild animals, and even in human feces. Because the bacteria are extremely sensitive to oxygen, it was difficult to separate and culture from feces at that time. So is it "difficult" for Clostridium difficile to appear? It seems not, but it is "difficult" to cultivate.

Although it is difficult to cultivate, what does it look like exactly?

Clostridium difficile is a Gram-positive, thick, long rod. It has an oval spore that is larger in diameter than the bacterium. It has flagella all over its body, so it can move. It is strictly anaerobic. After cultivation, yellow-green fluorescence can be seen under ultraviolet light. Clostridium difficile spores are highly resistant to common disinfectants, antibiotics, high concentrations of oxygen or gastric acid, but its reproductive bodies are more sensitive to these factors.

How does it make people sick?

(1) Mucus layer: loosely attached to the surface of bacteria, adheres to and colonizes the surface of intestinal epithelial cells.

(2) Cell surface protein 84 is a mucosal lytic enzyme secreted by bacteria that can lead to degradation of the colonic mucosa.

(3) Exotoxins: Most pathogenic Clostridium difficile strains can produce Clostridium difficile toxin A and Clostridium difficile toxin B. They can inactivate the Rho protein family in epithelial cells, leading to cell apoptosis and producing cytopathic effects. They are the most important pathogenic substances of Clostridium difficile. In addition, Ted B greater than 0.1 nmol/L can also increase intracellular reactive oxygen intermediates and promote cell necrosis.

The specific treatment process is that Clostridium difficile transferase is composed of two components, CDTa and CDTb. CDTb binds to cell surface receptors and mediates the toxic subunit CDTa into the cytoplasm; CDTa destroys the cytoskeleton and causes epithelial cell death.

In simple terms, b opens up the human network and brings a into the human body. a destroys the cells and the epithelial cells cannot withstand it and die.

So what kind of diseases can epithelial cell death lead to?

(1) Asymptomatic carriers: They are an important source of infection. It has been confirmed that 60%-70% of newborns, 3% of children over 3 years old, 3% of adults and 10% of the elderly carry Clostridium difficile asymptomatically. The intestines of newborns and infants lack receptors for the toxins produced by Clostridium difficile, and they often carry the bacteria without causing disease.

(2) Nosocomial diarrhea: History of hospitalization, underlying diseases, elderly people, use of acid suppressants, and previous antibiotic treatment are risk factors. Among them, a history of antibiotic treatment is the most important high-risk factor. Watery diarrhea often occurs 5-10 days after the use of antibiotics for prevention or treatment. It is also traditionally called antibiotic-associated diarrhea. However, more than 30% of diarrhea cases have no history of antibiotic treatment, which is related to the history of hospitalization, the patient's age, or underlying diseases. It has been reported that within 1 week of hospitalization, 13%-20% of hospitalized patients can be detected with Clostridium difficile, and the detection rate can increase to 50% within 4 weeks of admission.

After Clostridium difficile enters the duodenum through the stomach, the spores are stimulated by primary bile acids from the liver and begin to germinate and form vegetative factors, which have a significant inhibitory effect. In addition to the type of antibiotic, the duration of action, dosage and combined effects of antibiotics are important. Although all antibiotics and even acid suppressant treatments are associated with CDI, lincomycin, cephalosporins and quinolone antibiotics are the most common causes; antibiotics can destroy the normal intestinal flora, which is an influencing factor for the germination of Clostridium difficile spores to form vegetative bodies and toxicity. In the colon, secondary bile acids inhibit the germination of Clostridium difficile spores, promote the formation of vegetative bodies and excrete them with feces.

3) Pseudomembranous colitis: 5% of CDI patients may experience bloody diarrhea, discharge pseudomembranes, and be accompanied by systemic poisoning symptoms such as fever and leukocytosis. Severe cases may be life-threatening.

So what’s the best way to prevent it?

The main measures for treating CDI include: immediately discontinuing the relevant antibiotics, which can relieve mild diarrhea symptoms; patients with more severe diarrhea or colitis need to be treated with metronidazole or vancomycin; about 20%-30% of patients will relapse or even relapse repeatedly, mainly because antibiotics can kill bacterial propagules but not spores, and fecal microbiota transplant (FMT) from healthy people can be tried for treatment.

Because Clostridium difficile is widely present in medical and natural environments, it is difficult to prevent CDI. Healthcare professionals should pay attention to hand hygiene to significantly reduce the incidence of CDI. Currently, there is no vaccine for prevention.

Through our understanding of Clostridium difficile, we found that the proportion of asymptomatic carriers is relatively high. Long-term use of antibiotics can easily lead to endogenous infections. Therefore, when diarrhea symptoms occur, in addition to paying attention to the color and shape of the stool, there are many other things to pay attention to. Microorganisms are a huge system, and the more we know about it, the better we can respond and prevent it.

References in this article are from the ninth edition of Medical Microbiology