Multiple risk factors for SSIs exist, and the perioperative use of antimicrobial prophylaxis has been long in use as an attempt to reduce SSI risk. The chosen antimicrobial agent should be effective against the most common surgical-site pathogens. The predominant organisms causing SSIs after clean procedures (i.e., most of the neurosurgical procedures) are skin flora including Staphylococcus Aureus and coagulase-negative Staphylococci (e.g., Staphylococcus Epidermidis) [8,9,10].
The administration of antibiotics is not intended to sterilize tissues, but to act as an adjunct to decrease the intraoperative microbial load to a level that can be managed by the patient’s immunity [11, 12]. To achieve this goal, it is crucial for antibiotic therapy to reach sufficient tissue levels at the time of the expected microbial contamination [9] and the optimal agent should preferably be long-acting, inexpensive, and has a low side effect profile [11].
According to NICE guidelines, single dose of antibiotic prophylaxis should be given on starting anesthesia and repeated dose is given if the duration of surgery is longer than the half-life of the drug used. The aim is to establish adequate tissue levels throughout surgery from the time of incision until closure [13, 14]. The same notion was advocated by the CDC guidelines published in August 2017 [1]. The excessive fear from the devastating complications of SSI after neurosurgical procedure may lead to prolonged antimicrobial prophylaxis practices. The abuse of antibiotics leads to increased drug resistance and bacterial spectral changes [15].
Throughout the conducted study in our university hospital, a local protocol of antimicrobial prophylaxis was used. This included the simultaneous administration of a third-generation cephalosporin, mostly ceftriaxone combined with ampicillin/sulbactam for long durations throughout the hospital stay, and mostly until sutures are removed.
It is possible that this practice contributed to the relatively high infection rate and the presence of predominately gram-negative infections. Additionally, culture results are affected, where about 1/3 of the cultures did not grow organisms. This can be partially explained by the effect of antibiotics in the pre-infection period or attributed to the empirical antibiotics given on suspicion of SSI. The predominance of gram-negative infections (65%) indicates a switch from the conventional gram-positive wound infections. This can be mainly attributed to the overuse of broad-spectrum prophylaxis giving opportunity for otherwise weaker strains to flourish [16, 17]. In support of this, the gram-negative organisms in the current results show multi-drug resistance, especially to the commonly used agents. We regard this as a serious turn of events because the appropriate drug management would entail the use of other more complex agents that have both higher side effects and a higher cost.
Three important results stand out in our study: a relatively high SSI rate of 19%; the most common infective organism being Acinetobacter and CSF leak as the only significant risk factor for SSI. The association of a postoperative CSF leak as the most significant risk factor for SSI indicates the absolute need for its prevention through meticulous surgical technique. It also reinforces the imperative for early and definitive management of a CSF leak in order to prevent serious sequelae.
The failure of our study to find statistical significance with respect to the other risk factors could be attributed to the small sample size relative to the expected incidence of variation in such factors. Thereby, the study might not be sufficiently powered to detect differences in those risk factors. The relatively small total number resulted in smaller numbers available for subgroup analysis and comparisons.
Breach of sterile techniques was recorded in all surgeries as well. This invokes cautionary measures in considering the results of the current study as it increases the number of confounding steps and variables that may have contributed to the outcome. It also emphasizes the role of good infection control practice and its impact on SSI risk.
The setting of the current study could be viewed as a limitation of its own, namely the peculiar pre-study environment and specific antimicrobial prophylaxis regimen. Nevertheless, similar practices are still out there in many developing countries and in some centers in the developed world. Subsequently, any derivations will be considered input to help shape a local corrective practice. In other words, the pattern of predominantly gram-negative microbial prevalence in our SSI sites is peculiar and as such is considered essential to tailor a local antibiotic prophylaxis protocol.
We are aware of the downsides of the current study, being a single-center study with a small number of subjects is on the top of the list, and some data were lost about subtype of SSI despite being a prospective study in addition to a 13.7% attrition which is within the acceptable range and do not undermine the internal validity of the results.