Probiotics were used by 2.6% of patients who had been discharged from 145 U.S. hospitals in 2012, according to an analysis of data by Sarah H. Yi of the Centers for Disease Control and Prevention and her colleagues.

“Whether probiotics are effective in preserving or restoring a healthy microbiome remains unknown, but the high prevalence of probiotic use among hospitalized patients may indicate a growing belief among clinicians that these agents may be an effective strategy for doing so,” Ms. Yi and her colleagues wrote.

The researchers used information contained in the Truven Health MarketScan Hospital Drug Database to estimate probiotic use in the inpatient setting.

Among 1,976,167 pediatric and adult patients discharged from 145 hospitals in 2012, 51,723 (2.6%) of the patients used probiotics. The individuals who used probiotics had been patients at 139 of the 145 hospitals. Compared with patients who had not used probiotics, the patients who had used probiotics were 21 times more likely to have a discharge diagnosis of Clostridium difficile infection (P less than .0001), almost 9 times more likely to have used antimicrobials (P less than .0001), more likely to have been admitted from another inpatient health care facility (P less than .0001), and more likely to have been transferred to another health care facility at discharge (P less than .001). Each of the probiotic formulations used contained between one and four organisms identified at the species level. Saccharomyces boulardii, Lactobacillus acidophilus, L. bulgaricus, and L. rhamnosus were the most commonly used probiotic formulations.

The top five diagnoses for the patients who received probiotics were septicemia (except in labor); pneumonia (except that caused by tuberculosis or sexually transmitted disease); intestinal infection; skin and subcutaneous tissue infections; and urinary tract infections. For those patients not taking probiotics, live-born infants, osteoarthritis, septicemia (except during labor), pneumonia (except that caused by tuberculosis or sexually transmitted disease), and heart failure (nonhypertensive) were the most commonly received diagnoses.

The researchers also analyzed a study of the use of probiotics at 60 hospitals during 2006-2012, which showed annual increases of probiotic use among discharged patients and an overall 2.9-fold increase in probiotic use during those years. Specifically, 10,722 discharged patients used probiotics in 2006, compared with 28,871 patients in 2012.

“Because the patients most likely to benefit [from probiotic use] are also most at risk for an adverse event, preclinical research focused on the selection of likely probiotics and carefully designed clinical trials with systematic assessment of safety is particularly important,” the researchers said.

Among the questions needed to addressed in future research on probiotic use is “which strain-specific organisms, which patient populations, at what doses, and in what time frames (related to antibiotic use in particular) are both safe and effective in the prevention or treatment of which diseases?” according to the researchers.

Read the study in American Journal of Infection Control ( doi: 10.1016/j.ajic.2015.12.001 ).