There is insufficient evidence to support an evidence-based recommendation regarding the utility of intraoperative cultures at the initial operation to guide antibiotic treatment

In the absence of direct scientific evidence, EXPERT CONSENSUS concluded that:

• Intra-operative cultures of the scalp, wound track, or bone/metal fragments should not be routinely performed at the initial surgery to guide antibiotic prophylaxis. These cultures and subsequent treatments do not predict or prevent future cranial infections.
• Intraoperative cultures are appropriate if intracranial infection is present at the time of surgery.

No evidence or expert opinion supported distinct recommendations based on patient gender, age, wounding mechanism, or military vs. civilian context.

Infection is a major source of morbidity and mortality after pTBI as all pTBI wounds are inherently contaminated. The first pTBI guidelines reported rates for infection varying from 1 to 59% in their included series. When intracranial infection is present, it is the standard of care to obtain cultures from the infected tissue ideally prior to antibiotic initiation to guide future therapies.

The prophylactic use of antibiotics including the type and duration of therapy has been debated in pTBI. This topic is addressed in other sections of these guidelines, but previous authors have reported obtaining cultures of the soft tissue, debris, and wound tract to guide these antibiotic therapies or to predict the future infection pathogens.1-3 Opponents of this approach argue that these cultures do not predict the infective organism and modifying antibiotic therapy based on these cultures may select for other organisms not obtained in the limited sampled area.

The prior guidelines reported studies of cultures of contaminated intraoperative surfaces. However, no recommendation was given regarding if cultures should routinely be performed at the time of index surgeries or if the results from such cultures could or should guide antibiotic therapies.

No additional studies were identified after the publication of the prior pTBI guidelines indicating that the practice of routine culturing of the debris at the time of index operation is less common. Three studies used in the prior guidelines were identified as relevant to this question and meeting inclusion criteria. Although we found studies where individuals had intraoperative cultures taken, we identified no study that compared obtaining intraoperative cultures versus not obtaining intraoperative cultures. We also identified no study that compared broad spectrum antibiotic therapy given initially to patients with penetrating traumatic brain injury versus antibiotic therapy tailored to culture results.

One study of 125 patients from the Iran-Iraq War (Aarabi et al.)1 classified head wounds as penetrating (51.6%), perforating (7.4%), or tangential gutter type (22.4%). However, 18.6% could not be classified.1 This study reported that out of 102 intraoperative brain cultures in 125 patients, 28% were positive and out of 95 intraoperative bone fragment cultures, 21% were positive.1 Gram-positive organisms were grown more frequently from both brain cultures (59%) and bone cultures (76%) compared with gram-negative organisms. The additional studies (Carey et al. and Ecker et al.) demonstrated mostly gram-positive organisms but most deaths in the later study were from infective gram negative organisms, which may imply that the cultured organisms may not be the same bacteria that lead to overt infection.2,3

No study reported harms related to obtaining a culture nor did studies report harms associated with antibiotic treatment. It is unknown if poorer outcomes would have resulted if cultures were not taken and tailored antibiotic therapy not provided resulting in insufficient evidence to determine the benefits and harms of obtaining intraoperative cultures.

Two fundamental questions influence the decision to obtain cultures. Is there a relationship between contamination and subsequent CNS infection and can we prevent deep infections by knowing the contaminating organisms and prescribing antibiotics which target them? The question of antibiotic prophylaxis is addressed in other sections. However, the cultured organisms at the time of initial pTBI surgery do not necessarily correlate with the organisms present when intracranial infections develop3, and therefore tailoring antibiotics to these cultures may not prevent infection. If the information then does not alter patient management, routine cultures at the index operation are not recommended. Intraoperative cultures remain the standard of care during surgical debridement and cleansing of an active intracranial infection to guide further antibiotic treatments.

The lack of direct comparison between patients managed with and without intraoperative cultures limits the conclusions. Additionally, no study reported the patient outcomes including the infection rates or organisms based on tailoring the antibiotics to these intraoperative cultures.

While intraoperative cultures are safe to obtain, the information may not change clinical management or the patient outcome. To date, no study has found a correlation between the culture results and the organisms present at the time of infection nor has the choice of antibiotic based on these culture results led to decreased infection risk. Given this lack of data, we do not recommend routinely obtaining cultures of the soft tissue, debris, foreign bodies, and missile tract. Obtaining cultures during an active cranial infection remains the standard of care.

Future studies comparing the use of antibiotics tailored to intraoperative cultures against broad spectrum antibiotics or no antibiotics at all would be appropriate to definitively answer these questions. Obtaining cultures from scalp wound, brain tract and retained bone fragment may also be considered under specific circumstances. For example, prolonged delays in definitive surgical care as may be present in wartime conditions may increase the value of intraoperative cultures. Additionally, prolonged CSF fistulas that eventually require open surgical repair may be more likely to product an infective organism at time of intraoperative cultures. These scenarios may also be the subject of future research studies.