Identification of Bacterial Agents causing Meningitis in Adult Population using BACTEC FX40 System

Introduction: Bacterial meningitis among adults is a medical emergency and requires immediate diagnosis as well as immediate treatment. As clinical diagnosis is not always reliable, laboratory isolation along with antimicrobial susceptibility results are crucial. Conventional agar culture methods gives poor sensitivity and delayed results. Automated culture methods like BACTEC are suitable option for culture of sterile fluids beside blood culture. Aim: To determine the bacterial agents causing meningitis in this region, along with their antibiogram by using automated culture system BACTEC FX40. Materials and Methods: This cross-sectional, observational study was conducted between October 2019-September 2020 in Department of Microbiology, Rohilkhand Medical College and Hospital, Bareilly, Uttar Pradesh, India. Cereospinal Fluid (CSF) samples received from medicine Intensive Care Unit (ICU) and wards were processed by inoculating them on BD BACTEC Peds Plus/F bottle and then incubating them on BACTEC BD FX40 system. The bottles flagged and positive were subcultured and further processed according to standard laboratory procedures. The antibiotic sensitivity test was performed from isolated organisms by Kirby-Bauer Disc Diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: A total of 108 CSF were received for culture by automated methods from patients suspected of meningitis during the study period. Out of them 84 (77.8%) beeped as positive while 24 (22.2%) were sterile. From the positives, 77 showed growth of gram positive cocci, three were gram negative bacilli and four showed growth of environmental and skin contaminants that were excluded from the study. All gram positive cocci were identified as Staphylococcus aureus (S. aureus). The antibiotic sensitivity testing showed 100% sensitivity to vancomycin and linezolid. Only 25 isolates of S. aureus were sensitive to cefoxitin. Both the isolates of Escherichia coli (E. coli) were sensitive to cefazolin, ceftazidime, aztreonam. Pseudomonas aeruginosa (P. aeruginosa) was sensitive to amikacin and piperacillin/tazobactum. Conclusion: A shift in the trend was observed in the aetiology of bacterial meningitis with Methicillin Resistant Staphylococcus aureus (MRSA) as the most predominant isolate among adult population. BACTEC FX40 system was found more sensitive in detecting pathogens over the conventional methods with reduced time to positivity. Early detection of causative organism will facilitate early initiation of suitable antibiotic therapy, thereby reducing mortality and meningitis associated complications.