We write in reference to a recent article published in the BMJ from Hickson et al.1 indicating that twice-daily intake of a probiotic drink for 1 week longer than antibiotic treatment can prevent diarrhoea associated with antibiotic use. The study appeared flawed in that no ‘high risk antibiotic’ use was included in the study, a point raised in a subsequent letter by Billyard.2
Further to this, we decided to look at the antimicrobial susceptibility pattern of organisms contained in commercially available products that claim to contain bacteria. The chosen products included a drink containing Lactobacillus casei and a capsule formulation that claimed to contain five different Lactobacillus spp.
Antimicrobial susceptibility tests were performed by the disc diffusion technique using BSAC guidelines. As there are no published zone sizes for lactobacilli using these guidelines, zone diameters were interpreted from a range of other organisms. Our results would indicate that the lactobacilli isolated from these products are susceptible in vitro to many of the antibiotics associated with diarrhoea and Clostridium difficile.
The bacteria obtained from the capsule were susceptible to a range of cephalosporins, carbapenems and clindamycin, whereas those from the liquid formulation were resistant to oral cephalosporins but susceptible to clindamycin and cefuroxime.
One can therefore conclude that the bacteria contained in these products are unlikely to offer a protective effect in vivo when they are themselves susceptible to the same antibiotics considered to be high risk for antibiotic-associated diarrhoea.
Funded internally by the Microbiology Department Freeman Hospital.
None to declare.