Enrichment culture of CSF is of limited value in the diagnosis of neonatal meningitis

Current methods for microbiological diagnosis of acute central nervous system infections

The incidence of infections affecting the central nervous system has increased in recent years, making neuroinfections a current global health problem. The central nervous system is quite well protected from the external and internal environments, although it is susceptible to infection by a wide variety of pathogens. The etiological diversity further complicates the management of such infections because it is important to identify correctly the specific cause in order to choose the most appropriate antimicrobial therapy. Diagnosis is made not only based on clinical and epidemiological data but also on the results of clinical laboratory and microbiological examination of cerebrospinal fluid. This article aims to review current microbiological methods in the diagnosis of acute central nervous system infections and help healthcare providers to recognize their advantages and limitations in order to manage their patients appropriately.

Total Laboratory Automation and Three Shifts Reduce Turnaround Time of Cerebrospinal Fluid Culture Results in the Chinese Clinical Microbiology Laboratory

Background

Total laboratory automation (TLA) has the potential to reduce specimen processing time, optimize workflow, and decrease turnaround time (TAT). The purpose of this research is to investigate whether the TAT of our laboratory has changed since the adoption of TLA, as well as to optimize laboratory workflow, improve laboratory testing efficiency, and provide better services of clinical diagnosis and treatment.

Materials and Methods

Laboratory data was extracted from our laboratory information system in two 6-month periods: pre-TLA (July to December 2019) and post-TLA (July to December 2020), respectively.

Results

The median TAT for positive cultures decreased significantly from pre-TLA to post-TLA (65.93 vs 63.53, P<0.001). For different types of cultures, The TAT of CSF changed the most (86.76 vs 64.30, P=0.007), followed by sputum (64.38 vs 61.41, P<0.001), urine (52.10 vs 49,57, P<0.001), blood (68.49 vs 66.60, P<0.001). For Ascites and Pleural fluid, there was no significant difference (P>0.05). Further analysis found that the incidence of broth growth only for pre-TLA was 12.4% (14/133), while for post-TLA, it was 3.4% (4/119). The difference was statistically significant (P=0.01). The common isolates from CSF samples were Cryptococcus neoformans, coagulase-negative Staphylococcus, Acinetobacter baumannii, and Klebsiella pneumonia.

Conclusion

Using TLA and setting up three shifts shortened the TAT of our clinical microbiology laboratory, especially for CSF samples.

Higher recovery rate of microorganisms from cerebrospinal fluid samples by the BACTEC culture system in comparison with agar culture

The aim of this study was to assess the diagnostic value of the BACTEC FX blood culture (BC) system as compared to the agar culture (AC) of cerebrospinal fluid samples (CSF), evaluating the recovery rate and the time to detection of microorganisms in a 3.5-year period. From December 2011 to May 2015, 1326 CSF samples (694 patients) were submitted to both AC and BC. Among the 150 positive samples (96 patients), 165 microorganisms were detected: 81 by both the protocols, 77 by BC alone, and 7 by AC alone, demonstrating a higher detection rate of BC (95.8%) than AC (53.3%). Although BC presents some disadvantages, it is able to improve the yield of clinically significant microorganisms, and it could potentially reduce the reporting time as compared to AC. The results obtained highlighted the necessity of a combined approach for the successful detection of central nervous system microbial infections.

Cerebrospinal fluid enrichment broth cultures rarely contribute to the diagnosis of bacterial meningitis

This study included children undergoing lumbar puncture in the emergency department. Bacteria were isolated from 34 (1.7%) of 1898 cerebrospinal fluid (CSF) enrichment broth cultures; 30 were contaminants. The primary CSF Gram stain was negative in all specimens with a positive enrichment broth culture. Enrichment broth cultures rarely contributed to the diagnosis of bacterial meningitis, and positive CSF enrichment broth cultures contributed to diagnostic uncertainty.