Comparison of bedside inoculation of culture media with traditional cerebrospinal fluid culture method in patients with suspected bacterial meningitis at Kenyatta National Hopsital

Abstract

Background: The yield of bacterial cultures from cerebral spinal fluid (CSF) at Kenyatta National Hospital (KNH) is very low. Bedside inoculation of culture media with CSF may improve yields. Objective: To compare the culture yield of CSF inoculated onto culture medium at the bedside to CSF which is inoculated onto culture medium in the microbiology laboratory. Hypothesis (Ha) : The yield of CSF inoculated onto culture medium at the bedside would be significantly higher than the yield of CSF inoculated onto culture medium in the microbiology laboratory. Study design: Cross-sectional comparative study Setting: Accident and emergency department and medical wards, Kenyatta National Hospital, Nairobi, Kenya. Study population: CSF from patients admitted to the medical wards at KNH with a clinical diagnosis of meningitis. Study method: Patients admitted with a clinical diagnosis of meningitis were subjected to lumbar puncture after excluding those in whom the procedure was contraindicated. CSF thus obtained was either inoculated onto culture medium at the bedside or put in a sterile specimen bottle. Both samples were then transported to the microbiology laboratory at the same time. CSF in the sterile bottle was inoculated onto culture medium at the laboratory and both samples were then incubated for up to 72 hours under appropriate conditions. Isolated bacteria were identified using standard microbiologic techniques and sensitivity patterns to various antibiotics determined using disk diffusion method. Data management and analysis: Data was entered into a computer database and analyzed using SPSS version 11.5. Comparison between the two culture methods was made using the z test. Results: Two hundred and twenty CSF specimens were obtained during a four month period. S.pneumoniae was isolated from 24 CSF specimens and H.influenzae from 1. Bacterial cultures were positive in 25 (11.4% , 95% CI 7.0- 15.6%) of samples inoculated at the bedside and 23 (10.5%,95% CI 6.5-14.5%) of samples inoculated at the laboratory. Bacteria were isolated 5 hours earlier in samples inoculated at the bedside(95% CI 4.34-6.86 hrs,p<0.05). Four percent of S.pneumoniae isolates were resistant to crystalline penicillin and chloramphenical. Conclusion: There was no significant difference in culture yield after bedside inoculation of culture media with CSF compared to traditional CSF culture method. Bedside inoculation of culture media with CSF resulted in faster time to positive culture. The majority of bacterial isolates were susceptible to antibiotics currently used at KNH