**2.9 Concerns about probiotics**

Although there are numerous advantages and health benefits associated with probiotics or probiotic food products, there are risks associated with probiotic therapy. These risks are mainly concerned with respect to safety in vulnerable target groups such as immunocompromised individuals (pregnant women, babies and the elderly) or critically ill or hospitalized patients (Boyle et al., 2006; Jankovic et al., 2010).

Probiotic cultures are resistant to some antibiotics. There is concern about the possible transfer of antimicrobial resistance from probiotic strains to pathogenic bacteria in the gut. For example, many *Lactobacillus* strains are naturally resistant to vancomycin, which poses a potential threat of transfer of this resistance to other pathogenic bacteria such as *Staphylococcus aureus*. However, these vancomycin-resistant genes in lactobacilli are chromozomal and not readily transferred to other species.

Another important area of concern is the risk of sepsis. There have been several reports of cases of *Lactobacillus* sepsis and other bacterial sepsis due to the intake of probiotic supplements (Boyle et al., 2006). One case included a 67 year-old man who was taking probiotic capsules daily for mitral regurgitation and developed *Lactobacillus rhamnosus* endocarditis after a dental procedure (Borriello et al., 2003; Mackay et al., 1999). In another case, a 4-month old infant with antibiotic-associated diarrhoea, who was given *Lactobacillus rhamnosus* after cardiac surgery, developed *Lactobacillus* endocarditis 3 weeks after *Lactobacillus rhamnosus* treatment (Boyle et al., 2006; Kunz et al., 2004). However, there have been no reports to date on the occurrence of *Bifidobacterium* sepsis. All cases of bacterial sepsis from the use of probiotics (*Lactobacillus* spp.) have occurred in immunocompromised individuals or patients who have a chronic disease or debilitation. No cases have been reported in healthy individuals (Boyle et al., 2006). There have also been several cases of fungemia associated with *Saccharomyces boulardii*. However, investigation of these cases revealed that the infection was due to contamination of inserted catheters. It is therefore now recommended that *Saccharomyces boulardii* probiotics be prepared in powdered form under stringent hygienic conditions to prevent contamination (Borriello et al., 2003; Salminen et al., 1998). There is a small risk of adverse metabolic effects from manipulation of the microbiota with the use of probiotics, although probiotic studies to date have not shown significant adverse effects on growth or nutrition (Boyle et al., 2006). A review of safety assessments of probiotics was recently published (Sanders et al., 2010).
