Rates of cerebrospinal fluid infection and the causative organisms following shunt procedures in Saudi Arabia

Discussion

The burden of infantile hydrocephalus in Saudi Arabia, a developing country, is significantly higher than those in other developed countries, including Sweden, England, Wales, and Japan. The incidence of congenital hydrocephalus in Saudi Arabia is estimated to be 0.81 to 1.6 per 1000 live births.1-3

In this study, the incidence of shunt infections exceeded 32%, which is significantly higher than that reported in similar clinical settings.9,10 Additionally, the causative organisms differed from those found in previous studies conducted in Saudi Arabia, with some new pathogens, such as Serratia marcescens, being identified.3 Thus, management of the factors that contribute to the high rate of shunt infections; such as hygiene, wound care by the patient or the nursing staff, duration of hospital admission, experience of the surgeon, surgical technique used, duration of the procedure, and handling of the indwelling device during surgery; and the more frequent use of antibiotics than that in other countries are required. However, this may lead to the emergence of antibiotic resistance, thus limiting antibiotic choices and efficacy in the future.

Use of VPS is known to be associated with a higher rate of infection than the use of other methods of CSF diversion.11 However, in our study, the rate of infection was higher following EVD procedures, despite VPS procedures being the most commonly performed procedure. It has been reported that the incidence of postsurgical VPS infection ranges from 3% to 9% in Western countries and from 9% to 32% in African countries; the incidence is lower in developed countries.12 In countries in sub-Saharan Africa, especially in regions with endemic bacterial infections, it is advisable to use empirical broad-spectrum antibiotics to prevent postoperative infection.13 Until recently, the use and effects of prophylactic antibiotics have been a source of debate.12,13 For the best results, it is essential to target the most commonly implicated pathogens when administering prophylactic antibiotics before patients undergo surgery.

Sarguna and Lakshmi14 retrospectively analyzed the records of 226 patients who had undergone shunt procedures and found only 9 shunt infections (overall infection rate: 4%); the other CSF and blood cultures were sterile. Their study results indicated that CSF cultures may be negative even when the shunt device harbors infection.15

Staphylococcus species are mainly present on the skin and superficial areas; hence, it is difficult to prevent infections cause by these bacteria.10 This explains why surgical incisions are prone to staphylococcal infections. Staphylococcus epidermidis, which is a part of the normal skin flora, was the most commonly encountered organism in our study; this is in keeping with reported international figures. Staphylococcus epidermidis is a permanent and pervasive colonizer of human skin, and there is a high chance of device contamination during insertion through the scalp skin (Figure 2).16,17

Although most (90%) shunt infections occur within 20 days of surgery, some infections may not occur until many years after surgery.10 Viereck et al15 reported that symptoms of cryptococcal infection started 10 days to 15 months after shunt placement. They also reported a case involving a VPS procedure in which a cryptococcal infection was only detected 20 years after VPS placement. This type of infection is an infrequent complication of VPS, and only 9 cases of shunt-related cryptococcal infections have been reported to date.18 Having said that, our results did not reveal any cases of cryptococcal infection.

Based on imaging findings, the majority of CNS infections can be classified based on their MR sequences T1 and T2 weighted imaging and contrast enhancement characteristics. Ring enhancing lesions, basal ganglia space-occupying lesions, and gray and white matter hyperintensities are common patterns. Imaging is of substantial importance to detect the signs of infection caused by pyogenic bacteria in the subarachnoid space, brain parenchyma, ventricles (ventriculitis or pyocephalus), and the potential extra-axial spaces (epidural or subdural empyema). Similar to parenchymal abscesses, pus in the ventricles (occipital horns) or epidural or subdural space shows restricted diffusion, a useful finding for distinguishing simple effusion from empyema in the context of acute bacterial meningitis (Figures 1 & 2). Magnetic resonance spectroscopy is useful to evaluate necrotic masses; for example, infections with a central necrotic cavity lacking normal brain metabolites (choline, creatine, and n-acetyl aspartate) can be evaluated using this technique. Restricted diffusion or periventricular enhancement depends on whether the patient can mount an inflammatory response against pathogens (Table 3).19-26

Cerebrospinal fluid shunt infections caused by Candida albicans (C. albicans) are rare because this fungal agent only thrives well among individuals in immunosuppressed states.18 Cancer patients, those receiving chemotherapy, or individuals with HIV infection are at higher risk of these CSF shunt infections.12 In this study, C. albicans was identified in CSF cultures from immunocompetent patients (2.5%), even though it is difficult to isolate C. albicans from immunocompetent patients in the laboratory.27

The incidence of CSF shunt infections varies with age; it has been reported to be the highest among infants and to decline with increasing age.12,14 However, this was not the case in our study. The rate of infection was the highest in elderly patients, adults, and pre-school children. This observation concurs with the proposed factors attributing to postoperative infections, including patient age, immune status, environmental exposure, and nutritional status.28 Environmental exposure is the presence of microorganisms that can cause infection. Age is closely related to the immune status. This explains why the least virulent organisms affect children and elderly patients more frequently than the rest of the population.

Cerebrospinal fluid infection is a major concern in the neurosurgical field due to the following reasons: i)adverse cognitive outcomes; ii) high rates of morbidity and mortality; ii) need for prolonged courses of antibiotics following hospitalization; iv) negative psychosocial impact on patients and families; and v)need for shunt revisions. The fact that there is a foreign shunt placed in the body significantly contributes to the development of CSF infections among patients undergoing procedures involving incisions in the ventricular system.28 Insertion of shunt devices requires proper diagnosis and handling; therefore, only sterilized hardware (sterilized by steam, ethylene oxide, and other low-temperature sterilizers) should be used.

Precautions are needed to reduce the rate of CSF infections. Bacteremia must be ruled out based on results of complete white blood cell count, inflammatory markers, and other laboratory procedures. Additionally, if patients and physicians adhered to infection control, bacteremia is less likely to occur. Additionally, attempts should be made to minimize the number of operative room personnel, shorten the operative time, and ensure proper instrument sterilization.28 Recently, a detailed standardized protocol was published for use during CSF shunt surgeries to prevent postoperative infection regardless of the patient’s age.29 The protocol includes guidance on the control of the surgical environment to minimize contamination from air, double gloving, local injection of antibiotics, and detailed postoperative management. The protocol also provides guidance on immersion of devices, optimal timing of skull x-ray, and detailed postoperative management.

Furthermore, at our facility, we advise strict follow-up at the outpatient clinic within 2 weeks of discharge, to assess the surgical wound margins, CSF culture results from the shunt aspirate, blood test, and culture results. Patient attendance at the clinic is significantly influenced by their health-seeking behaviors, which may influence the development of postoperative complications. Thus, we employed a number of strategies to ensure that patients attended their follow-up appointments, such as scheduling in-person follow-up care appointments at the patient’s convenience. Additionally, we attempted to adhere to the core principle of providing the patient or the patient’s parents’ with comprehensive health education, including information on the health condition and possible complications.