The US Food and Drug Administration (FDA) has sent a stern letter to Glaxo SmithKline (GSK) warning about ongoing cross-contamination problems at its facility in Worthing, UK. The letter dates back to an inspection carried out in July 2015 that caused the UK’s largest drugmaker to stop production in part of the plant. The FDA said that since 2012 it has found 187 instances of penicillin in non-penicillin manufacturing areas, and that GSK’s procedures are “wholly inadequate.”

“Contamination of non-beta-lactam drugs with beta-lactam drugs presents great risks to patient safety, including anaphylaxis and death. No safe level of penicillin contamination has been determined to be a tolerable risk,” the FDA wrote. The agency has given GSK two options: dedicate the facility solely to penicillin API production so that cross-contamination would not be a problem, or submit a plan for full decontamination. However, it has warned that the latter option would be extremely difficult to carry out and would be subject to comprehensive vetting.

GSK had to recall more than 425,000 Bactroban antibiotic creams last year after an FDA inspection. The company is now said to be proposing a recall for the small number of Bactroban batches that remain within their shelf life. The FDA has also uncovered several other problems at the plant. The letter said there have been ongoing issues with microbial contamination in the water used to make APIs, with 25 breaches of the alert level in the period between April 2014 and February 2015.

Three batches of APIs were rejected because of out-of-spec testing. Also, the inspectors said that in one API batch, GSK identified green fibres, which were probably from scouring pads, red flakes likely to be paint in the manufacturing plant, and black particulates that were consistent with glass particles.

The FDA has asked GSK to provide a risk assessment for its API manufacturing process and other drugs produced with the same equipment. This should include an evaluation of the physical condition of the facility as well as cleaning and preventative maintenance measures.