Antibiotic susceptibility of probiotic strains: Is it reasonable to combine probiotics with antibiotics?

OBJECTIVE: The main goal of this study was to determine the in vitro susceptibility of strains collected from marketed probiotics to antibiotics used to treat community-acquired infections. METHODS: The minimum inhibitory concentrations (MICs) of 16 antibiotics were determined using a gradient strip (E test) or the agar dilution method for fidaxomicin. RESULTS: The probiotics demonstrated various antibiotic patterns. Bacterial probiotics are generally susceptible to most prescribed antibiotics orally administered, whereas yeast probiotics, such as Saccharomyces boulardii, are resistant. CONCLUSION: Special attention must be paid to co-prescriptions of antibiotics and probiotics to ensure that the probiotic strain is not susceptible.

Anti-anaerobic activity of a new ß-lactamase inhibitor NXL104 in combination with ß-lactams and metronidazole.

NXL104 is a new ß-lactamase inhibitor (BLI) that inhibits class A and class C ß-lactamase enzymes. In this study, the activity of NXL104 in combination with the third-generation cephalosporins ceftazidime (CAZ) and ceftriaxone (CRO) or with piperacillin (PIP) was evaluated against 316 anaerobic bacteria. Minimum inhibitory concentrations (MICs) were determined using an agar dilution method. The BLIs NXL104 or tazobactam (TAZ) were added to the ß-lactams at a fixed concentration of 4 mg/L. A triple combination of NXL104 with an 8:1 ratio of CAZ and metronidazole (MTZ) was also tested. The activities of CAZ, CRO and PIP in combination with NXL104 were enhanced against many of the bacteria. MIC(50) values (MIC for 50% of the organisms) for CAZ+NXL104 were 8-16-fold lower than those of CAZ against Gram-negative anaerobes. Antibiotic resistance rates against all anaerobic strains were: CAZ, 37.7%; CRO, 31%; CAZ+NXL104, 15.2%; CRO+NXL104, 5.4%; and MTZ, 4.1%. No resistant strains could be observed with PIP+TAZ, PIP+NXL104 or the triple combination MTZ+CAZ+NXL104. In conclusion, the triple combination of MTZ+CAZ+NXL104 demonstrated potent antibacterial activity against anaerobes representing most clinical species. It appears appropriate for the treatment of polymicrobial infections, since CAZ+NXL104 also exhibits potent activity against ß-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa. It is currently being tested in phase 2 clinical trials for the treatment of complicated intra-abdominal infections.