listeria monocytogenes is a gram - positive rod that is often found in the natural environment including the soil and rivers , wild animals , and livestock , and usually causes human infection through contaminated food . the human listeria infections transmitted by food are different from the enteritis caused by other bacteria . the infections are usually found in immunocompromised patients , pregnant women , infants and babies ; listeria is very rare in healthy children1 - 3 ) . listeria causes central nervous system infections , endocarditis , and sepsis in patients with organ transplants , patients receiving immunosuppressive therapy , and patients with malignancies . an infection during pregnancy can cause miscarriage , sepsis , and premature birth , as well as amnionitis , disseminated abscess accompanied by sepsis , granuloma , and late - onset meningitis , conjunctivitis , and pneumonia4 ) . listeria infection in infants usually causes meningoencephalitis , conjunctivitis , and pneumonia ; it primarily invades the brain stem rather than supratentorial areas , and is often accompanied by complications such as acute hydrocephalus . the clinical symptoms are similar to other cases of meningoencephalitis caused by bacteria including : fever , headache , vomiting , and altered mental status . other forms of central nervous system infection include : encephalitis , brain abscess , and spine abscess . in addition , listeria can cause a suppurative arthritis , osteomyelitis , and liver abscess3 ) . according to prior reports up to the present , infections by listeria are rare in korea5 ) ; however , infections in healthy children without immune system abnormalities are very rare6 ) . here we report a rare case of meningoencephalitis caused by l. monocytogenes in a previously healthy 7-year - old girl . a previously healthy 7-year - old girl presented with periodic fever of over 38 , headache , abdominal pain , and watery diarrhea for six days ; she had projectile vomiting and a severe headache accompanied by lethargy , and was admitted to the hospital . she had never been contacted with contaminated foods and domestic animals . although the mental status was intact at the time of presentation , neck stiffness , the bruzinski sign and kernig sign were all positive ; there was no abnormality in motor function and muscle strength , and sensation was intact . the laboratory tests included : white blood cell counts 21,150/l ( segmented neutrophils 89% , lymphocytes 6.3% ) , esr 57 mm / hr , crp 9.52 mg / dl , and the fasting blood sugar was 169 mg / dl . the cerebrospinal fluid ( csf ) examination showed 1,500/l white blood cells ( segmented neutrophils 30% ) , 250/l red blood cells , a sugar of 25 mg / dl , and protein of 117 mg / dl ; there were no bacteria noted on gram staining . pcr for tuberculosis , the herpes simplex virus antibody test , the co - agglutination test , and cryptococcus antigen test were all negative . we started antibiotic treatment with ceftriaxone and amikacin along with steroid injections before receiving the results of the cultures . on the second hospital day , we added vancomycin to the treatment because of continued fever of over 39 , severe headache , vomiting , and altered mental status ; the patient appeared stuporous and delirious . a brain mri was performed because of a suspected increase in the intracranial pressure and the development of diplopia ; there were no clinical findings suggestive of brain edema , such as an increase in the size of the ventricles . on the third hospital day , the fever and headache continued , and the patient complained of pain in both legs . due to the worsening of the mental status , we repeated the csf examination and blood tests . the results of the blood test showed 37,860/l white blood cells ( segmented neutrophils 88.2% , lymphocytes 5.3% ) , an esr of 50 mm / hr , crp 17.19 mg / dl , and fasting blood sugar of 142 mg / dl . the csf had a white blood cell count of 2,000/l ( segmented neutrophils 35% ) , red blood cell count of 250/l , a sugar of 73 mg / dl , protein 319 mg / dl , and gram - positive rods were confirmed on gram staining . l. monocytogenes was identified in both the blood and csf , and ampicillin was added to the treatment ( fig . the antimicrobial susceptibility test showed that the organisms were sensitive to vancomycin , ampicillin , and aminoglycosides . testing of immunity included : an igg of 872 mg / dl , iga 208 mg / dl , igm 257 mg / dl , and ige 960 iu / ml ; except for the increase in ige , the c3 113 mg / dl , c4 28.2 mg / dl , and ch50 51.1 u / ml were all within normal range . the cd3 was 61.3% ( 1798/mm ) , cd4 32.7% ( 959/mm ) , cd8 35.2% ( 1033/mm ) , and cd19 17% ( 499/mm ) all within normal limits . in addition , an ultrasound of the thymus was within normal limits . on the fourth hospital day , although the patient responded to pain stimulation , her conversation was confused and meaningless . the pupillary reflexes were slow , and nystagmus was noted ; in addition , the muscle strength decreased to grade 2 . the patient developed respiratory difficulty and her state of alertness was at the semicoma level . ct of the brain , showed hydrocephalus , parenchymal edema , and brain stem extrusion along with an increase in the third and fourth cerebral and lateral ventricles ; extraventricular drainage was performed ( fig . additional extraventricular drainage , two consecutive times , was performed on the sixth and fourteenth day . on the 17th hospital day , the csf examination showed 32/l white blood cells , 3,100/l red blood cells , a sugar of 99 mg / dl , and protein of 169 mg / dl ; there were no bacteria detected on gram staining . the worsening hydrocephalus noted on the brain ct and because the level of consciousness was not improving a ventriculoperitoneal shunt procedure was performed on the 22nd hospital day . on the 25th hospital day she responded appropriately and her language was no longer confused . on the 31st hospital day , the vital signs were stable , and she was transferred from the intensive care unit to the general ward . the brain ct , on the 38th hospital day , showed a communicating hydrocephalus with ventriculostomy and parenchymal edema . the child recovered consciousness and motor functions and was discharged after 61 days in the hospital . l. monocytogenes is an anaerobic gram - positive bacillus that is usually found in the soil , dust , fertilizer , sewage , river water , plants , and food , as well as animal intestines . meningoencephalitis caused by l. monocytogenes usually occurs in patients with neoplastic disease , those taking high doses of steroids , the elderly with weak immunity , pregnant women , and infants1 - 3 ) . when infection due to listeria occurs , it can be fatal ; the mortality rate is up to 30% . l. monocytogenes enters a variety of host cells such as macrophages , epithelial cells , and parenchymal cells , by phagocytosis . it forms a structure that is wrapped around by actin filament from the host cell in the protoplasm . this results in a protrusion of the membrane of the host cell , and adhesion to nearby cells , facilitating bacterial transmission among cells . as a result , the listeria can hide inside of the host cell and be protected from the immune reaction of host cells , enabling the spread of infection9 ) . l. monocytogenes invasion has a predilection for endothelial cells in brain microvessels , and can cause severe sequelae by affecting white blood cells and stimulating an inflammatory reaction within the central nervous system10 ) . a temporary change in the t - lymphocyte population during the latent period of bacterial infection , has been reported in cases where meningoencephalitis caused by listeria occurred in healthy children1 , 2 ) . cases with meningitis due to virus , bacteria , parasites , or mold that causes acute hydrocephalus as a secondary complication are uncommon1 , 11 ) . however , according to previously reported cases , where meningoencephalitis caused by listeria occurred in healthy children , the disease progressed rapidly and was associated with acute hydrocephalus ; in these cases there was a high mortality rate1 ) . there have been many cases where listeria infections were mistaken for streptococcus pneumonia or diphtheria , which also has a low positive rate of gram staining . a listeria infection must be included in the differential diagnosis of meningoencephalitis , even though such an infection is rare in healthy children without immune function disorders1 , 3 , 4 , 12 ) . in this case , although we were unable to identify listeria strains from the initial gram stain of the csf , we identified listeria , as a gram - positive bacillus , on the second csf gram stain , and have identified l. monocytogenes from the blood and csf cultures . therefore , repeat csf studies should be performed in cases with meningoencephalitis and no specific organism identified on initial evaluations1 , 3 , 9 ) . the antibiotics used to treat meningoencephalitis caused by listeria include ampicillin and penicillin ; use combined with aminoglycoisides such as gentamicin and amikacin have been reported to be effective5 , 10 , 13 , 14 ) . while vancomycin has been effective with in vitro testing , it has had a high failure rate clinically10 , 13 , 14 ) . in addition , third generation cephalosporins are not used because they have no bactericidal effects1 , 5 ) . third generation cephalosporins and vancomycin are recommended as initial empirical antibiotics in bacterial meningitis where penicillin - resistant pneumococcal infections have been documented10 , 14 ) . in this case , she had taken the conjugated pneumococcal vaccines and there were no bacteria on the initial csf gram stain , so we started initial antibiotics treatment with ceftriaxone and amikacin . then we added vancomycin on the second hospital day , and on the third hospital day we discontinued ceftriaxone and added ampicillin after identifying a listeria strain . susceptibility results showed that the organism was sensitive to vancomycin , ampicillin , and aminoglycosides . even after normal initial neuroimaging of meningoencephalitis caused by listeria , follow up studies are needed during the course of the infection . listeria infections can be complicated by hydrocephalus and/or brain edema within 1 week of the start of treatment ; as was noted in the case presented here . therefore , repeated neuroimaging is necessary to identify the associated complications1 , 7 ) . in conclusion , we treated an unusual case of meningoencephalitis caused by l. monocytogenes in a healthy child without any underlying disease including an immune disorder . if gram - positive bacilli are observed in the csf , meningoencephalitis caused by l. monocytogenes should be suspected ; repeat csf studies and neuroimaging are essential for early detection of neurological complications3 , 15 ) .
listeria monocytogenes is a facultative anaerobic , gram - positive bacillus that is isolated from the soil , vegetables , and wild or domestic animals . 
 listeria occurs predominantly in the elderly , immunocompromised patients , pregnant women and newborns . 
 infections by this microorganism are rare in healthy infants and children . 
 l. monocytogenes may cause meningitis , meningoencephalitis , brain abscess , pyogenic arthritis , osteomyelitis , and liver abscesses in children . 
 the course of meningoencephalitis by listeria is often severe and even fatal . 
 acute hydrocephalus can develop as a complication and the mortality associated with listeriosis is significantly high . 
 we present a case of meningoencephalitis caused by l. monocytogenes in a previously healthy 7-year - old girl .