You will be shown a paragraph from a biomedical research article. Your task is to extract all drug combinations appearing in a specific sentence within in the paragraph. Each drug combination should be assigned to one of the following three categories:

- POS: Indicates a positive interaction between the drugs in the combination; for instance, drugs that have an additive or synergistic effect.
- NEG: Indicates a negative interaction between the drugs in the combination; for instance, combining these drugs might result in adverse side effects, or might reduce their efficacy.
- COMB: Indicates that the drugs are given in combination, but the type of interaction between the drugs cannot be determined based on the provided context.

Please format your answer as a json array. Each entry in the array should itself be an array formatted as [<drug_1>, <drug_2>, ..., <drug_n>, <category>] where <category> is one of the three categories listed above and <drug_1>, ..., <drug_n> are drug names copied verbatim from the input sentence. Different combinations may involve different numbers of drugs; in other words, the `n` in <drug_n> may vary.

As an example, the following output describes two extracted drug combinations; one between two drugs, and one between three drugs:

[["artesunate", "artemether", "COMB"], ["Nifedipine", "Labetalol", "Prazosin", "POS"]]

The paragraph and specific sentence are below. You should only extract relationships expressed in the specific sentence; the paragraph is provided for context.

In your output, return only the json array and no other text. If no drug combinations appear, return an empty array `[]`.

paragraph: Piperacillin-resistant Escherichia coli bacteraemia: relation to empiric therapy and clinical outcome. Escherichia coli is a leading cause of bacteraemia. The aim of this study was to evaluate all E. coli positive blood cultures collected during a 4-y period in a haematological department using piperacillin plus netilmicin for empiric treatment of febrile episodes . We measured the incidence of piperacillin-resistant E. coli bacteraemia among haematological and non-haematological patients, described the importance of previous antibiotic treatment for resistance development in E. coli and evaluated the impact of piperacillin resistance on the clinical outcome of E. coli bacteraemia. 114 episodes of E. coli bacteraemia in 104 patients were recorded and 98 episodes in 88 patients (42 males and 46 females) with a median age of 64 y (range 19-85 y) were evaluated. In 81.6% of the episodes the patients had a haematological disorder, dominated by acute leukaemia (41.3%), chronic leukaemia (16.3%) and lymphoma (10%). The proportion of piperacillin-resistant E. coli was higher among haematological patients than non-haematological patients (25% vs 0%, p=0.02) and resistance was associated with piperacillin therapy during the previous month (p=0.05). No difference in clinical outcome was found between haematological patients infected with piperacillin-susceptible or -resistant E. coli (intensive care 12% vs 15%; mortality 22% vs 25%).

sentence: The aim of this study was to evaluate all E. coli positive blood cultures collected during a 4-y period in a haematological department using piperacillin plus netilmicin for empiric treatment of febrile episodes .
[["piperacillin", "netilmicin", "COMB"]]