In order to improve the detection rate of Listeria, a new method was developed. This new method enables the quantification of Listeria in the cerebrospinal fluid of human patients. In this study, four vegetables were analyzed for microbiological quality and Listeria spp. contamination. The total plate count (TPC) of cabbage, carrot, and lettuce showed statistically significant differences from control. The APC of cucumber and lettuce was the lowest, but still significant.
The study involved a patient with an elevated fever on the day of admission. On the day of admission, the patient had a meningeal irritation sign and the lumbar puncture was immediately performed. The first lumbar puncture performed in the hospital revealed a clear cerebrospinal fluid with 150 leukocytes/mm3, 1680 mg/L protein, and 1.8 mmol/L glucose. The CSF staining was negative for Gram-positive bacteria, fungi, or other microorganisms.
In this prospective study, 14 cerebrospinal fluid samples were obtained from ruminants with listeric encephalitis. Of the 11 CSF samples analyzed bacteriologically, eight had confirmed clinical diagnoses. Only one patient had a positive PCR result in a single case. This was due to the fact that the sample of a sheep treated with antibiotics before the CSF was collected.
The researchers also found that the sensitivity of this new method was improved by using liquid-based methods. While the level of L. monocytogenes was low in the dairy industry, it was still detectable with the cheese smear. In total, seventy-seven FBOs were positive for Listeria spp. during the sampling period. The study showed that the industrial cheesemaker program was successful in detecting L. moncytogenes.
Among the four types of fruits and vegetables tested, cabbage and carrot showed the highest levels of Listeria. The lowest-quality apples, on the other hand, were the least contaminated. A further study will be needed to confirm whether the results of the two tests are accurate. It is important to note that the two tests are independent of each other. They should be carried out in the same laboratory as the test of the food chain.
The detection of Listeria in cerebrospinalian cerebrospinal fluid samples requires the use of a rapid, accurate method for the determination of the pathogen. The researchers also noted that the results of the tests were comparable for the four types of vegetables. A positive result in any one of the vegetable sample is not a cause for alarm, but rather a reflection of the high-quality of the produce.
The study has several strengths. Compared with the conventional PCR-based method, the new test can detect more pathogenic bacteria in the cerebrospinal fluid than traditional culture-based methods. It also offers a faster and more accurate method of detecting L. spp. during acute infections, thereby avoiding a false-negative test. This method is recommended for the detection of Listeria in food-related illnesses.
The study was conducted on 20 clinical CSF samples to identify Listeria. In both laboratories, the microbial quality of the sample is high. For example, the growth rate of bacteria varies according to the temperature, the relative humidity, and the types of food and beverages consumed. However, the rate of contamination in a patient’s CSF is lower in the case of a bacterial infection caused by the contaminated food.
The current method used to detect Listeria spp. in cerebrospinal fluid was effective for a single colony of L. monocytogenes, whereas PCR-based assays were only useful for identifying a single L. spp. in the whole CSF. These results have been published in the scientific journal Biotechniques
