Prevalence and antibiotic resistance profile of cerebrospinal fluid pathogens from neurosurgical patients from level 1 trauma center in India

Introduction: The purpose of this study was to investigate the prevalence of Postoperative central nervous system infections (PCNSIs) and antibiotic resistance profiles of causative organisms in trauma patients following neuroinvasive procedures. Materials and Methods: This was a retrospective study conducted over a period of 4 years (2013–2017). All in-patients admitted under a neurotrauma unit meeting the inclusion criteria of PCNSIs were included in the study. Surgical site infections (SSIs) were defined according to the Centers for Disease Control and Prevention 2018 (CDC) criteria. We retrospectively examined the demographic characteristics, type of neurosurgery performed, laboratory data, causative organisms, and antimicrobial susceptibility testing results of patients who had positive cerebrospinal fluid cultures following craniotomy between January 2013 and December 2017. Results: Of total 2500 patients operated during the study, 961 patients were screened for PCNSIs. The estimated prevalence (95% confidence interval) of PCNSIs which is a type of organ/space SSI was 7.2% (6.3–8.3). Males were predominantly affected (85.0%). The mean age (standard deviation) of patients was 31.9 (16.5) years. Of all the cultures sent for microbiological examination, 18.6% were positive. The proportion of Gram-negative bacteria causing PCNSIs was 91.6%. Multidrug-resistant (MDR) Acinetobacter baumannii (41%) was the most common organism isolated. Among Gram-positive bacteria, the most common organism was Staphylococcus aureus (5.5%). All the Gram-positive isolates were susceptible to vancomycin, teicoplanin, and linezolid. Conclusion: There is a high burden of PCNSI caused by MDR Acinetobacter baumannii can pose a major clinical challenge with only few antimicrobials left in the pipeline.

Key-words:

Craniotomy - multidrug-resistant Acinetobacter baumannii - neuroinvasive procedures - postoperative central nervous system infections - trauma patients

Introduction

Postoperative central nervous system infection (PCNSI) in patients undergoing neurosurgical procedures represents a significant threat following neurosurgery, which requires immediate attention. The most common presentations of PCNSI include meningitis, subdural empyema, epidural abscess, and brain abscess.[[1]] The risk factors for postoperative infections after neurosurgical procedures include cerebrospinal fluid (CSF) leak, postoperative monitoring of intracranial pressure, placement of foreign body, ventricular drains, shunt infection, longer duration of procedures, repeat or additional neurosurgical procedures, and emergency procedures.[[2]] A recent study involving 16,200 craniotomies showed that CSF leakage and male sex as independent risk factors for the development of PCNSI.[[3]] Several studies have identified the role of antibiotic prophylaxis after neurosurgical procedures in relation to PCNSI, demonstrating the decline in the incidence of PCNSI with antibiotic prophylaxis.[[1]],[[4]]

Recent studies have reported that the incidence of PCNSI after neurosurgical procedures varies from 0.7%–8.9%.[[3]] The incidence of PCNSI varies between different regions with developed countries having lower incidence than developing countries. Studies have shown the most common causative agent of PCNSIs being Staphylococcus aureus, Coagulase-negative staphylococci followed by the Gram-negative organisms.[[5]] The present study was conducted to establish the prevalence and causative organisms of PCNSIs and the antibiotic resistance profiles of CSF pathogens in trauma patients following neuroinvasive procedures.

Materials and Methods

This was a retrospective study which included patients admitted under a neurotrauma unit who underwent craniotomy between January 2013 and December 2017. These patients were investigated for possible PCNSIs based on clinical signs and symptoms. The patients who met the clinical diagnostic criteria of central nervous system infection were included in the study.[[6]] Patients who underwent cranial operation previously, both by elective and emergency procedures were also included in the study. The patients with clinical, radiological, or microbiological examination suggestive of tubercular/viral/fungal meningitis were excluded from the study. The data of patients with positive culture isolates were collected from medical records. The data included demographic characteristics, types of neurosurgery performed, laboratory data, causative organisms, and antimicrobial susceptibility testing. The main outcome of interest is PCNSIs which is a type of organ/space Surgical site infection (SSI) according to Centers for Disease Control and Prevention 2018 (CDC) criteria used to define SSIs.[[7]] The isolation of the same organism within 7 days from the same patient was regarded as the same isolate and not counted multiple times. All patients received (dose) 2 g of cefoperazone-sulbactam and 300 mg netilmicin as prophylactic therapy 1 h before incision, followed by a 24-h postoperative course.

CSF samples were collected on suspicion of infection as per standard procedures. One of the specimens was used for Gram staining and bacterial culture the other was used for cytology, protein, and sugar estimations. All CSF-positive culture isolates were identified up to the species level by VITEK 2 GN card (version 7.02, BioMérieux, Inc., Durham, USA). Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion method on Mueller Hinton agar and by Vitek 2 (BioMérieux) system. The results of antibiotic susceptibility were interpreted based on the Clinical and Laboratory Standards Institution guidelines.[[8]] SSIs had to meet the CDC and Prevention 2018 (CDC) criteria.[[7]]

Statistical analysis was done using IBM SPSS (Statistical Package for Social Sciences) Statistics version 22.0 (IBM, Armonk, NY, United States of America). Results were presented with 95% confidence intervals (CIs) in case of categorical variables and as mean or median in case of continuous variables. Chi-square test was used to compare proportions. Student t-test and Mann–Whitney test were used to compare means and medians, respectively.

Results

From 2013–2017, a total of 2500 in-hospital patients were operated on in the department of neurosurgery. We obtained 3591 CSF culture samples from 961 patients admitted under a neurotrauma unit. Of these, 338 CSF samples had a positive growth in culture. The patient's medical records were reviewed. Following review, 180 CSF-positive cultures which met the inclusion cultures were included in the study. The remaining 158 CSF samples were excluded from the study due to multiple CSF samples obtained from the same patient and failure to retrieve patient's medical records. The prevalence (95% CI) of PCNSIs among trauma patients following neuroinvasive procedure was 7.2% (6.3–8.3). Out of 961 patients sampled, 180 (18.7%) patients had a positive CSF culture.

The mean age of the patients with PCNSIs was 31.9 (16.5) years. A majority of patients were males (85.0%). A total of 91 (50.6%) out of 180 patients with PCNSIs did not survive. The proportion of patients who underwent craniotomy, shunt placement, decompressive craniectomy, duraplasty, and Ommaya placement were 33.9%, 51.1%, 61.7%, 26.1%, and 28.9%, respectively. CSF analysis indicated that the patients had low-CSF glucose and high protein levels postoperatively. Male patients (P = 0.001) and decompressive-craniotomy patients (P = 0.02) had higher chances of mortality among PCNSI patients [[Table 1]].

Table 1: Comparison of demographic and clinical parameters of dead and alive patients with postneurosurgical bacterial meningitis (w=180)

The most common organisms causing PCNSIs were Gram-negative bacteria (92.1%). The predominant Gram-negative organism was Acinetobacter baumannii (41.0%) followed by Klebsiella pneumoniae (14.0%), Escherichia coli (11.7%), Pseudomonas aeruginosa (7.8%), Serratia marcescens (7.3%), and Enterobacter cloacae (4.4%). The predominant Gram-positive isolate was Staphylococcus aureus (5.6%) followed by Enterococcus faecium (1.1%) and coagulase-negative staphylococci (1.1%) [[Table 2]].

Table 2: Bacteria isolated from cerebrospinal fluid (n=180)

All the Staphylococcus aureus isolates were sensitive to linezolid, teicoplanin, vancomycin, and netilmicin. The two Enterococcus faecium isolates were all sensitive to linezolid, rifampicin, teicoplanin, and vancomycin. The two coagulase-negative staphylococcus isolates were sensitive to linezolid, rifampicin, teicoplanin, and vancomycin [[Table 3]]. Of the Gram-negative isolates, there were 73 Acinetobacter baumannii, 25 Klebsiella pneumoniae, 21 Escherichia coli, and 14 Pseudomonas aeruginosa isolates available for analysis. The susceptibility testing of the Gram-negative isolates showed that colistin was the most active agent (100%) [[Table 4]].

Table 3: Proportion percentage of Gram-positive bacteria sensitive to antibiotics

Table 4: Proportion percentage of Gram.negative bacteria sensitive to antibiotics

Discussion

PCNSI is one of the most dreadful complications following cranial operations. They are associated with increased costs of treatment, increased length of hospital stay, psychological trauma, and delay in postoperative adjuvant therapies.[[9]] Before the advent of antibiotics for surgical prophylaxis and sterile surgical techniques, the rates of PCNSI were quite high.[[10]],[[11]],[[12]] The overall rate of PCNSIs varies between 0.72% and > 12% according to various size limited studies.[[13]],[[14]],[[15]] The PCNSI patients included in the study were diagnosed by CSF culture, the prevalence of PCNSI in our center was found to be 7.2% which was similar to few previously conducted studies.[[16]],[[17]] However, there are other studies in which the rates were high ranging from 6.5%–12%.[[18]],[[19]]

The culture positive rate of PCNSI in our study was found to be 18.6%, which is low compared to previous studies which showed culture-positive rate of infection approximately 50%.[[15]],[[18]],[[19]] The possible reasons could be similar isolates obtained from the same patient within 7 days were considered as a single isolate. Another reason could be the use of cefoperazone-sulbactam and netilmicin as prophylactic antibiotics followed by the used of therapeutic antibiotics once the infection was diagnosed. The mortality rate of PCNSI in our study was found to be 50.6% which is higher than reported by other studies.[[20]],[[21]]

The predominant organism was Gram-negative bacteria which accounted for 92.1% of the total isolates. Acinetobacter baumannii was the most common causative Gram-negative agent, accounting for 41% of the total isolates. Among the Gram-positive bacteria, Staphylococcus aureus (5.6%) was the most common organism followed by Coagulase-negative staphylococci (1.1%) and Enterococcus faecium (1.1%). The microbiological findings in this study were consistent with previously published studies.[[10]],[[15]],[[22]]

Of the Gram-positive isolates, approximately 60% (6 isolates) of Staphylococcus aureus isolates were methicillin-resistant Staphylococcus aureus (MRSA), and these isolates were susceptible to vancomycin, linezolid, teicoplanin, and netilmicin. The incidence of MRSA in our study was higher in comparison to other studies.[[23]],[[24]] The two coagulase-negative staphylococci isolates were methicillin-resistant coagulase-negative staphylococci (MRCoNS) and were also susceptible to vancomycin, teicoplanin, linezolid rifampicin, and netilmicin. The two Enterococcus faecium isolates were susceptible to linezolid, vancomycin, teicoplanin, and rifampicin. The results of Gram-positive antibiotic sensitivity rates indicate that most effective antibiotics against MRSA, MRCoNS, Enterococcus faecium were vancomycin, teicoplanin, and linezolid. Vancomycin is considered to be the last resort and drug of choice for the treatment of CNS infections caused by the Gram-positive bacteria. However, in the study conducted by Chang et al. had PCNSI caused by vancomycin-resistant Enterococcus faecalis isolates.[[9]] Thus, the emergence of vancomycin resistance could be serious threat for PCNSIs caused by the Gram-positive organisms.

Of the Gram-negative isolates, the most predominant organism was Acinetobacter baumannii (41%) followed by Klebsiella pneumoniae (14%), Escherichia coli (11.7%), and Pseudomonas aeruginosa (7.8%). The rate of carbapenem-resistant Acinetobacter baumannii was 79.4%. The emergence of multidrug-resistant (MDR) Acinetobacter baumannii known as one of the ESKAPE pathogens has become a serious medical problem globally.[[25]] The rise in incidence of MDR Acinetobacter baumannii infections is of great concern due to the lack of treatment options for such pathogens. The most effective antibiotics for the treatment of Gram-negative infections were tigecycline and colistin. The finding was similar to previously published studies.[[9]],[[26]],[[27]]

Early diagnosis and appropriate use of antibiotics is necessary for the management of PCNSIs. There are only few studies available from India with regard to the causative organisms and drug sensitivities of PCNSIs.[[2]],[[3]],[[28]] The present study demonstrated that the distribution of pathogens from our region was similar to the trend observed globally, thus helping the clinicians to choose the appropriate empirical antibiotic treatment for PCNSIs. The limitations of the study were that data with regard to clinical variables were not studied, the isolates included in the study may not be a representative for the whole of India, and the isolates were not characterized to molecular level to depict the resistance characteristics.

Conclusion

PCNSIs represent as serious threat, leading to higher mortality rate. This study also highlights the prevalence and causative organisms of PCNSIs from a tertiary care center located in North India. Our study shows an increasing prevalence of Gram-negative organisms in CSF cultures from PCNSIs after neurosurgery. The management of MDR Acinetobacter baumannii remains a major clinical challenge with only few antibiotics options left for the treatment of PCNSIs.

Conflict of Interest

There are no conflicts of interest.

Financial support and sponsorship

Nil.

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Publication History

Article published online:
09 September 2022