Question

The patient was an 80-year-old female who 10 days previously had a cystocele repair performed. At the time of that hospital admission, a urine culture was ontained that revealed > 100,000 CFU/ml of an Escherichia coli strain that was suusceptible to all antimicrobial agents against which it was tested. Postoperatively, she began a 7-day course of oral cephalexin. She was discharged after an uneventful postoperative courser of 3 days. Ten days postoperatively, she presented with a 3-day history of diarrhea. The patient noted multiple, watery, loose stools without blood, crampy abdominal pain, and vomiting. She presented with a temperature of 38.2 C, pulse rate of 90/min, respiratory rate of 20/min, and blood pressure of 116/53 mm Hg. Her white blood cell count was normal, but a large number (53%) of immature polymorphonuclear cells were seen. Physical examination, electrolytes, liver enzymes, and lipase were all within normal limits. A methylene blue strain for fecal leukocytes showed the presence of rod-shaped bacteria. Cultures for Salmonella, Shigella, Yersinia, and Campylobacter were all negative. An enzyme immunoassay (EIA) that was positive for the presence of a bacterial toxin in the stool established the patient's diagnosis.

1. What organism was causing this woman's diarrhea? 2. For most agents of bacterial diarrheal disease, culture is used to establish the etiology of disease. Why is this strategy not useful in this disease? Why is toxin detection employed to diagnose this disease? How well does it work? 3. What in her history was a predisposing factor for her development of this infection? How did it predispose her? 4. Why is this organism particularly problematic as a nosocomial pathogen? 5. What virulence factors does this organism produce, and what roles do these factors play in the pathogenesis of the disease? 6. Discuss three different types of therapeutic strategies that can be used to treat this disease.

Answer 1

1. The organism causing diarrhea in the given scenario is Clostridium difficile. It is a bacteria normally found in the gut. But alterations in the gut flora like taking antibiotics can predispose to this type of infection.

2.

In bacterial culture, the organism is identified by its growth. It is not possible to take culture from stool, since the gut also contains normal flora and it would not be possible to identify the organism causing infection.

C.difficile is also present as normal gut bacteria. When the gut flora is disturbed by taking antibiotics, its growth increases and causes inflammation. It also produces toxins which are excreted in the stools and this can be detected since it produces specific toxins.

3. The patient was on antibiotic therapy for urinary infection. There are bacteria present normally in the gut. C.difficile is also present and its growth is normally suppressed by the other bacteria. Taking antibiotic causes alteration in the gut bacteria, which leads to growth of C.difficile.

4. C.difficile infection most commonly occurs with antibiotic therapy. Patients can be hospital for a long time due to chronic illness. There can be cross infection if adequate precaution measures are not taken. The health care workers are at risk of transferring the organisms because of contaminated articles or hands. So it is problematic as a nosocomial pathogen.

5. The virulence factors the produced by the organism are the toxins – TcdA and TcdB. The toxins produced leads to host tissue damage and inflammation causing the disease.

6. The drugs used are vancomycin, fidaxomycin and metronidazole

Supportive therapy and fluids

Infection control measures and probiotics