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Diarrhea is a very common side effect of antibiotic use. Unfortunately, this fact is often both overlooked and misunderstood by prescribers, both in terms of definitions and causes. A conventional definition of diarrhea is a change in the usual stool frequency with at least three watery stools per day. From a laboratory perspective, a diarrheal stool should conform to the shape of the container, and since Clostriodioides difficile (formerly Clostridium difficile) colonization without disease is common, formed stools should not be tested for the presence of C. difficile. Antibiotic-associated diarrhea (AAD) may occur during the course or after completion of antibiotics. The prevalence of AAD is reported as between 3.2% and 29% in various studies. The diagnosis of AAD is complicated by the fact that many things cause loose stools, including a variety of bowel-related diseases, parasites, viruses, and bacteria, as well as laxatives and drugs aside from antibiotics, dietary factors, and common underlying conditions seen in healthy people, including lactose intolerance.

Clostridium difficile (C. difficile) infection (CDI) is an increasing common healthcare-associated infection and disproportionally affects our elderly patients and patients in long-term care facilities (LTCFs) (Asempa and Nicolau, Clin Interv Aging. 12:1799, 2017). As described in other chapters of this book, patients with CDI can have multiple loose or watery stools in 1 day causing extreme dehydration, electrolyte disarray, sepsis, toxic megacolon, and even death. With the increasing prevalence and severity of CDI over the past decade, clinicians are understandably concerned when suspecting CDI in one of their patients and keen to test to see if C. difficile is present in the stool. However, the presence of C. difficile in the stool is not sufficient to diagnose CDI, and the current diagnostic tests commercially available are complex. CDI is a toxin-mediated infection and therefore, diagnostic assays often focus on the presence of toxin as a necessary component to develop infection, as opposed to colonization with non-toxigenic C. difficile strain. Nucleic acid amplification test (NAAT), enzyme immunoassay (EIA), and cytotoxigenic culture (CC) and cell cytotoxicity assay (CCTA) are available options. A multistep algorithmic approach has been recommended to utilize the above-mentioned testing. Diagnostics are challenged by decreased immune response in the elderly and delays in an LTCF setting. In this chapter, we will describe the different C. difficile diagnostic tests and their appropriate use in clinical practice in long-term care patients.

The clinical course of IBS is chronic, although symptoms vary and oscillate not only between subtypes, but also within the same patient over time. Overall, women are twice as likely as men to suffer from constipation-associated symptoms such as bloating, straining, abdominal distension and feelings of incomplete evacuation. Men in turn, tend towards diarrhea-associated symptoms, including watery stools, enhanced stool frequency, abdominal pain and bloating. Irrespective of the subtype, patients suffering from IBS tend to exhibit psychiatric and psychosocial disturbances, they are more vulnerable to stress and generally exhibit a high degree of abnormal illness behaviour. The current chapter summarizes major clinical features that are linked to the particular subtype of IBS. We also put interest on factors such as gender differences or lifestyle that may predispose to the occurrence of IBS symptoms.