Neonatal neutrophilia is an infection caused by Listeria monocytogenes and is mainly seen in neonates, the elderly, and immunocompromised patients. Clinical manifestations include neonatal disseminated cornual abscess, meningitis, septicemia, and endocarditis. The disease should be considered in all neonatal infections and in patients with immune deficiencies and fever of unknown origin. The patient’s blood leukocytes are often elevated, with an increased proportion of neutrophils and, rarely, mononuclear cells. In patients with meningitis, the cerebrospinal fluid is cloudy in appearance, with increased protein and neutrophils and decreased sugar levels. However, in a few patients, the cerebrospinal fluid is clarified and the sorted leukocytes are predominantly mononuclear. Cerebrospinal fluid smear staining for bacteria is often negative, but positive results can be obtained with bacterial culture. Bacteriological examination is the key to the diagnosis of the disease. Bacterial cultures of blood, bone marrow, cerebrospinal fluid, damaged skin and mucous membranes, as well as umbilical cord stumps, amniotic fluid, laryngeal and external auditory secretions, feces and urine can be isolated early in the course of the disease. A large number of gram-positive bacilli can be found in inflammatory secretions or meconium smears of newborns. The important point for the diagnosis of the disease is that where diphtheria-like bacteria are isolated from the above specimens, they should not be considered as contamination, but should be further identified. Any Gram-positive bacilli isolated from the blood or cerebrospinal fluid of symptomatic patients, hemolyzed and powered, the possibility of Listeria monocytogenes is high, and further biochemical and animal (guinea pigs and rabbits) pathogenicity tests should be performed. Laboratories with the conditions can make serological identification. Serum antibody potency is often significantly increased during the recovery period, which can be determined by agglutination reaction or complement binding reaction. However, because Listeria has the same antigens as other gram-positive bacteria (staphylococcus, streptococcus, pneumococcus, etc.), it can cause cross-reactivity and is not very helpful for diagnosis.