One of the major frustrations in microbiology is the interference to bacterial growth caused by previous administration of antibiotics. Culture growth inhibition may occur even if the organism is not sensitive to the antibiotic. Several antibiotic removal devices are now available, based on membrane filtration or resin adsorption. These are useful for liquid specimens such as spinal fluid, body cavity fluid or blood. Although some evaluations have found these devices to be helpful, others have not. This technique was (and is) controversial among infectious disease specialists.