Unless precautions are taken, taking antibiotcs can cause a number of infections, including oral thrush. Thrush is a form of fungal infection caused by Candida albicans. Wide-spectrum antibiotics kill most of the bacteria in the body, including the beneficial bacteria that keep Candida albicans under control.
According to Michigan State University, thrush is a serious concern in those with compromised immune systems from diseases such as HIV, cancer or lupus. Often, these patients are given antifungals in addition to antibiotics. In normal patients, eating yogurt with live cultures or taking probiotics during a course of antibiotics can help prevent thrush or other yeast infections.