Antibiotic time-lag combination therapy with fosfomycin for postoperative intra-abdominal abscesses

The first-line treatment for intra-abdominal abscess is source control. Sometimes, however, source control is too invasive for relatively small abscesses and is not feasible due to the risk of injury to some organs. Based on reports that fosfomycin (FOM) can break up biofilms to enhance the permeability of other antibiotics, we investigated the FOM time-lag combination therapy (FOM-TLCT). We enrolled 114 patients who had intra-abdominal abscess after gastrointestinal surgery and examined the efficacy of FOM-TLCT using the same therapeutic antibiotic (TA) as that which had been used previously, but had proven ineffective, at the same dose schedule. The efficacy endpoint determination was carried out as follows: among the systemic inflammatory response syndrome (SIRS)-positive cases, even after administration of TA, excellent outcome was defined as SIRS negative within 7 days of FOM-TLCT with TA without the need for other treatment, including other antibiotics or drainage. Of the 114 patients enrolled, 104 cases (SIRS positive 73; SIRS negative 31) were assessed. Ten patients were excluded; four had received TA at higher doses, three had received different TAs, and three were considered to have bacteria resistant to TAs. Among these patients, 86.3% (63/73) of the SIRS-positive cases were classified as excellent, and 90.3% (28/31) of the SIRS-negative cases were classified as effective. In total, the efficacy rate was 87.5% (91/104). The total no-response rates were 12.5% (13/104). FOM-TLCT seems to be effective for treating refractory intra-abdominal abscess.