moraxella osloensis , an oxidase - positive , nonmotile , asaccharolytic , aerobic gram - negative coccobacilli is a part of the normal flora of the human respiratory tract ( 1 , 2 ) . the organism is difficult to identify because of presence of several other species with similar phenotypic characteristics . species of some glucose non - fermenting gram - negative bacilli are not only difficult to identify by routine methods , but also the clinical significance is not always easy to interpret . clinical significance of m. osloensis isolates even from normally sterile site may be difficult to determine , because the organism rarely cause invasive infections . we report three cases of m. osloensis meningitis in two children with no known underlying disease and in one adult cancer patient . a 4-yr - old girl was admitted to the pediatric department on may 27 , 2002 , with a 1-day history of headache , fever ( 38.1 ) , abdominal pain , and vomiting ( table 1 ) . her past medical history was unremarkable and she was up - to - date with her immunizations . laboratory tests revealed a peripheral white blood cell ( wbc ) count of 19,800/l ( 91% neutrophils ) , a hemoglobin level of 11.6 g / dl , and a platelet count of 356,000/l . cerebrospinal fluid ( csf ) had a hazy appearance with an increased wbc count of 890/l ( 99% neutrophils ) , but no significant change in glucose concentration of 78 mg / dl , and a protein level of 31 mg / dl ( table 2 ) . the patient became afebrile after 2 days of treatment , and her other symptoms also improved . the csf analysis showed a decreased wbc count to 9/l from 890/l at hospital day 3 . a 15-yr - old boy was admitted to the neurology department on may 18 , 2005 , with a 3-day history of headache and 2 days of generalized petechiae , nausea , and vomiting ( table 1 ) . his past medical history was unremarkable . on admission , his oral temperature was 36.9 , heart rate was 93 beats / min , and blood pressure was 125/82 mmhg . there were no motor or sensory deficits , and the rest of his physical examination was unremarkable . a laboratory investigation at the time of admission revealed a peripheral wbc count of 30,290/l ( 96% neutrophils ) , a hemoglobin level of 15.4 g / dl , and a platelet count of 151,000/l . csf had a cloudy appearance with an increased protein concentration of 575 mg / dl , and a wbc count of 35,500/l ( 90% neutrophils ) and a decreased glucose concentration of 10 mg / dl ( table 2 ) . his clinical condition was improved after 3 days , and the csf analysis showed a decreased wbc count and protein concentration to 4,150/l and 90 mg / dl from 35,500/l and 575 mg / dl , respectively . on 13th hospital day , the csf wbc count decreased to 130/l , and the patient was discharged without complications on 18th hospital day . an 81-yr - old man with a known history of pancreatic cancer ( march , 2004 ) and liver cirrhosis due to hepatitis c virus infection ( june , 2004 ) was admitted to the emergency department on june 6 , 2005 , with drowsy mental status for one day . on admission , he had icteric sclera ( table 1 ) . laboratory investigation revealed a peripheral wbc count of 6,950/l ( 73% neutrophils ) , a hemoglobin level of 12.8 g / dl , and a platelet count of 60,000/l . csf was clear with a protein level of 38 mg / dl , a slightly increased wbc count of 9/l , and a glucose concentration of 76 mg / dl ( table 2 ) . routine blood chemistry showed increased blood urea nitrogen / creatinine of 41.8/2.2 mg / dl , ammonia of 287 g / dl and total bilirubin of 3.1 mg / dl . the patient was treated with cefotaxime for 1 week . on hospital day 3 , the csf wbc count decreased to 0/l . he was managed conservatively and was discharged 18th hospital day without complications . in case no . 2 many gram - negative coccobacilli were detected on smear of a csf . in cases 2 on blood and chocolate agar plates yielded heavy growth of medium sized ( 0.5 - 1 mm ) grayish colonies after overnight co2 incubation . in case no . the gram - stained smear of colonies revealed gram - negative coccobacilli in all three cases . the correct species identification was not achieved not only by the conventional biochemical tests , but also by the api i d 32 gn system ( profile 00000 - 000002 ) , and vitek2 gn system ( biomerieux , marcy l'etoile , france ) , but suggested moraxella spp . 16s rrna gene sequencing ( 3 ) identified all three isolates as m. osloensis ( 98% agreement with genbank accession no . the antimicrobial susceptibility test performed by the disk diffusion method ( 4 ) showed all three isolates were susceptible to ampicillin , cephalothin , cefoxitin , cefotaxime , ceftazidime , cefepime , levofloxacin , imipenem , amikacin , netilmicin , and gentamicin . a 4-yr - old girl was admitted to the pediatric department on may 27 , 2002 , with a 1-day history of headache , fever ( 38.1 ) , abdominal pain , and vomiting ( table 1 ) . her past medical history was unremarkable and she was up - to - date with her immunizations . laboratory tests revealed a peripheral white blood cell ( wbc ) count of 19,800/l ( 91% neutrophils ) , a hemoglobin level of 11.6 g / dl , and a platelet count of 356,000/l . cerebrospinal fluid ( csf ) had a hazy appearance with an increased wbc count of 890/l ( 99% neutrophils ) , but no significant change in glucose concentration of 78 mg / dl , and a protein level of 31 mg / dl ( table 2 ) . the patient became afebrile after 2 days of treatment , and her other symptoms also improved . the csf analysis showed a decreased wbc count to 9/l from 890/l at hospital day 3 . a 15-yr - old boy was admitted to the neurology department on may 18 , 2005 , with a 3-day history of headache and 2 days of generalized petechiae , nausea , and vomiting ( table 1 ) . his past medical history was unremarkable . on admission , his oral temperature was 36.9 , heart rate was 93 beats / min , and blood pressure was 125/82 mmhg . there were no motor or sensory deficits , and the rest of his physical examination was unremarkable . a laboratory investigation at the time of admission revealed a peripheral wbc count of 30,290/l ( 96% neutrophils ) , a hemoglobin level of 15.4 g / dl , and a platelet count of 151,000/l . csf had a cloudy appearance with an increased protein concentration of 575 mg / dl , and a wbc count of 35,500/l ( 90% neutrophils ) and a decreased glucose concentration of 10 mg / dl ( table 2 ) . his clinical condition was improved after 3 days , and the csf analysis showed a decreased wbc count and protein concentration to 4,150/l and 90 mg / dl from 35,500/l and 575 mg / dl , respectively . on 13th hospital day , the csf wbc count decreased to 130/l , and the patient was discharged without complications on 18th hospital day . an 81-yr - old man with a known history of pancreatic cancer ( march , 2004 ) and liver cirrhosis due to hepatitis c virus infection ( june , 2004 ) was admitted to the emergency department on june 6 , 2005 , with drowsy mental status for one day . on admission laboratory investigation revealed a peripheral wbc count of 6,950/l ( 73% neutrophils ) , a hemoglobin level of 12.8 g / dl , and a platelet count of 60,000/l . csf was clear with a protein level of 38 mg / dl , a slightly increased wbc count of 9/l , and a glucose concentration of 76 mg / dl ( table 2 ) . routine blood chemistry showed increased blood urea nitrogen / creatinine of 41.8/2.2 mg / dl , ammonia of 287 g / dl and total bilirubin of 3.1 mg / dl . the patient was treated with cefotaxime for 1 week . on hospital day 3 , the csf wbc count decreased to 0/l . 2 many gram - negative coccobacilli were detected on smear of a csf . in cases 2 on blood and chocolate agar plates yielded heavy growth of medium sized ( 0.5 - 1 mm ) grayish colonies after overnight co2 incubation . in case the gram - stained smear of colonies revealed gram - negative coccobacilli in all three cases . the correct species identification was not achieved not only by the conventional biochemical tests , but also by the api i d 32 gn system ( profile 00000 - 000002 ) , and vitek2 gn system ( biomerieux , marcy l'etoile , france ) , but suggested moraxella spp . 16s rrna gene sequencing ( 3 ) identified all three isolates as m. osloensis ( 98% agreement with genbank accession no . the antimicrobial susceptibility test performed by the disk diffusion method ( 4 ) showed all three isolates were susceptible to ampicillin , cephalothin , cefoxitin , cefotaxime , ceftazidime , cefepime , levofloxacin , imipenem , amikacin , netilmicin , and gentamicin . members of the genus moraxella are oxidase - positive , nonmotile , and asaccharolytic coccobacilli . genus moraxella consists of seven species , m. atlantae , m. canis , m. catarrhalis , m. lacunata , m. lincolnii , m. nonliquefaciens , and m. osloensis ( 1 ) . graham et al . ( 5 ) reported that m. osloensis was common and the most frequent isolate from blood and csf among clinical isolates of moraxella spp . it has been rarely reported to cause local or invasive infections , including osteomyelitis , meningitis , bacteremia , pneumonia , and catheter associated infection ( 6 - 11 ) . two patients had known predisposing factors for infection such as cerebrospinal fluid shunt and c8 complement deficiency , but the remaining two patients had no known underlying disease ( 12 ) . the children in case 1 and 2 had no underlying diseases . these children had typical meningitis symptoms such as headache , neck stiffness , nausea , and vomiting , an elevated wbc count , and increased protein in csf analysis . in case 1 , we could not totally exclude the coexistence of viral and bacterial meningitis because we did not test virus culture nor virus antigen assay . the adult patient ( case no . as this patient had drowsy mental status on admission , csf examination and culture were performed to rule out meningitis . a possible explanation of low csf wbc count was due to lower peripheral wbc count resulting from various cytotoxic therapies . the clinical diagnosis of this patient was hepatic encephalopathy because of high blood ammonia and high total bilirubin level . this patient was also diagnosed as bacterial meningitis because of m. osloensis growth from csf . with appropriate antimicrobial agents ' treatment , identification of an unusual bacterial isolate is a very difficult problem in a clinical microbiology laboratory . moraxella spp . grows well in capnophilic conditions , but grows slowly in ambient air which may lead to delays in diagnosis . commercially available using conventional biochemical tests and two commercial identification kits , we were able to infer the genus moraxella . however , we could not definitively identify the species because the results of various biochemical tests are similar among the seven moraxella spp . only with 16s rrna gene sequence analysis , we were able to definitively identify the isolates as m. osloensis ( 3 ) . this new method consists of pcr amplification and sequencing of the 16s rrna gene in bacteria , followed by a comparison of the 16s rrna gene sequence with those registered in genbank . m. osloensis is usually susceptible to penicillin g , cephalosporins , and aminoglycosides ( 5 , 13 ) . there are a few reports that treatment with penicillin g and ampicillin for m. osloensis bacteremia and meningitis has been successful . all three strains were susceptible to majority of antimicrobial agents , including ampicillin , cephalothin , cefotaxime , amikacin , levofloxacin , and imipenem . all patients were treated successfully with third - generation cephalosporins alone or in combination with netilmicin . in conclusion , although m. osloensis meningitis is rare it may cause severe cns infection in children and in adult cancer patient . we were able to definitely identify the species of the isolates only by using 16s rrna gene sequencing .