In TE/PPE therapy, the choice of antibiotics is always empiric. In the present study, broad spectrum agents such as carbapenem or broad spectrum penicillin were used in almost all cases as an initial antibiotics. The choice depends on the patient’s risk status or whether the empyema is community-acquired or nosocomial. In selecting the initial antibiotics, the target bacteria are often unknown so patients are treated empirically without culture data. Microbiological diagnosis is said to be achieved in only over 50% of cases  and it takes approximately a week to recognize the microbial etiologies. This means that culture data often do not reflect the full disease process and that the treatment is not always based on the culture data. Only Gram staining from the pleural effusions and peripheral blood or properties of the pleural effusions are the tips of the target bacteria. Thus, choosing broad spectrum agents is unavoidable in the induction of TE/PPE treatment.
When switching the antibiotics from broad to narrow spectrum agents pre- and postoperatively the decision should be made empirically because the target often remains invisible. The reasons for switching to narrow agents in our study were the preoperative fever reduction or intraoperative findings showing only serous effusion in all loculated cavities. On the other hand, when converting the antibiotics into broad agents, the decision is often made based on prolonged fever elevation or the remaining of the high level of WBC count. These decisions are not based on the result of bacterial culture so it does not correspond to so-called de-escalation or escalation of antibiotics. The ACCP category of the pleural effusion was 3 in 26 cases (79%). Preoperatively, pleural effusion was always obtained from one of the loculated cavities. Disrupting the loculated cavity in VATS-D, even in the case of preoperative diagnosis was category 3, often proving that the contents of cavities were homogenous and that some cavity contains pus. Therefore, the differential diagnosis of categories 3 and 4 or PPE and TE is often unclear. Thus, PPE and TE were examined without distinction in this study.
This study may be deviate from the international standards because metronidazole (MNZ) is not used and procalcitonin is not measured as an inflammatory marker. This is attributed to the special circumstances in Japan, intravenous MNZ and measuring procalcitonin were not commercially available or not covered by health insurance until late 2014 and early 2016. Currently, Japanese JAID/JSC recommends MNZ in combination with ABPC or 4th generation cephalosporin as a second choice regimen in both multidrug resistance risk and risk-free cases. For the purpose of suppressing the use of carbapenem to avoid antimicrobial resistance, MNZ may be chosen much in the future. Serum procalcitonin level-guided antibiotic use is reported to reduce antibiotic use . Serum level of procalcitonin rise or fall rapidly in bacterial infection with high sensitivity and specificity. It may be a useful biomarker for diseases such as TE/PPE that require empiric discontinuation or changes in antibiotics.
VATS-D is an evidential treatment for TE/PPE. It is said to shorten the chest tube duration and hospital stay  and reduce hospital death or one-year mortality compared with simple drainage or intrapleural fibrinolytic therapy [6, 8]. The reported success rate in VATS-D is approximately 90% [3, 6, 8]. However, descriptions about the duration of antibiotic use are few. In our study, the duration of antibiotic use was 2 weeks. Although the duration of antibiotics was shorter than the description in guidelines, the success rate in our study was 88% whichand it was similar to previous reports. On the other hand, it took two weeks from the onset to the operation. Urgent VATS-D is required to shorten the total hospital stay and the duration of antibiotic use.
There is no evidential consensus on the optimal duration of antibiotic therapy after surgical intervention in TE/PPE. The Sanford Guide states 4-6 weeks . In BTS guidelines, it is stated that approximately 3 weeks may be optimal . These descriptions include both surgical and nonsurgical cases. There seems to be no consensus on when to quit antibiotic therapy, especially after surgery. In the present study, a median fever exceeding 37.5ºC remained for 3 days. The WBC count and percentage of segmented neutrophils took from 4 to 7 days to return to the normal baseline value. Discontinuation of antibiotics was decided based on the patient’s physical or laboratory data. The mean and median postoperative duration of antibiotic use in this study was 7 days. Preoperatively antibiotics were used approximately 5 days. Antibiotic treatment in their primary care doctors was not reflected in the data we used. However, since the time from the onset to surgery was approximately 2 weeks, the total preoperative antibiotics are expected to be up to 2 weeks at the longest. As a result, the total antibiotic duration, including post and preoperation can be estimated to be 3 weeks in this study, and the postoperative antibiotic duration following VATS-D must be approximately 5 days.