First Human Case of Meningitis and Sepsis in a Child Caused by Actinobacillus suis or Actinobacillus equuli

Abstract

fWe report the first human case of meningitis and sepsis caused in a child by Actinobacillus suis or A. equuli, a common opportunistic pathogen of swine or horses, respectively. Identification was performed by matrix-assisted laser desorption ionizationtime of flight mass spectrometry and real-time PCR assay. A previous visit to a farm was suspected as the source of infection. CASE REPORTA previously healthy 13-year-old boy who had been suffering from otalgia for 24 h developed fever, headache, photophobia, drowsiness, and neck stiffness and was taken to the emergency department of a local hospital. No cranial traumas were reported. A physical examination found no other meningeal signs, neurological deficits, or papilledema. Otoscopic findings were normal. No petechiae were revealed. Laboratory tests showed neutrophilic leukocytosis (white blood cell [WBC] count, 17,700/l; percentage of neutrophils [N], 85%) and a C-reactive protein (CRP) level of1.0 mg/dl. Upon worsening drowsiness, non-contrast-enhanced magnetic resonance imaging of the head and neck was performed and the finding was normal. A lumbar puncture yielded opalescent cerebrospinal fluid (CSF) under normal pressure with 650 WBC/l, mainly polymorphonuclear cells, an elevated total protein level (254 mg/dl), and a normal glucose level (49 mg/dl). The serum glucose level was 113 mg/dl. The patient was empirically given ceftriaxone intravenously (50 mg/kg) and transferred to our tertiary-referral Children's University Hospital. Laboratory tests were repeated and showed increased neutrophilic leukocytosis (WBC count, 38,560/l; 95% N) and an elevated CRP level (12.7 mg/dl). Gram staining of CSF performed at the local hospital revealed a Gram-negative bacillus. Ceftriaxone was then switched to meropenem at 40 mg/kg/dose three times a day, and dexamethasone at 0.1 mg/kg/dose four times a day was added.Blood cultures carried out with the Bactec system with aerobic vials (Becton Dickinson, Milan, Italy) were positive for a Gramnegative bacillus after 24 h. The CSF culture yielded growth of several colonies of a Gram-negative bacillus on Columbia blood agar and chocolate agar supplemented with PolyViteX (bioMérieux, Florence, Italy) after incubation for 24 h at 37°C under aerobic conditions, while no growth was present on MacConkey agar. The bacterial isolates were identified by the Vitek2 system (bioMérieux) as Actinobacillus ureae (reported as excellent identification). However, the same isolates were identified as A. suis or A. equuli by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (Vitek MS; bioMérieux) with an identification score of 99.9%.Real-time PCR tests of DNA extracted from CSF with the Eusepscreen kit (Eurospital, Italy) for Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae types B and C, noncapsulated H. influenzae, Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae, and Listeria monocytogenes were negative.The 16S rRNA gene sequence, 997 bp long, confirmed the prese...

Actinobacillus ureae may be a critical pathogen in patients with predispositions: A case report and review of the literature

“…As early as 1992, 16S rRNA gene sequencing was carried out to confirm the identity of the organism, [35] while traditional phenotypic testing may cause improper identification, particularly when the isolate is rare, or the biochemical profile of the pathogen is uncommon, or even the automated systems do not have the panels of the organism. As described in the case of A. suis or A. equuli sepsis and meningitis, [36] the isolates yielded A. ureae by the VITEK 2 Compact, while A. suis or A. equuli was suspected based on MALDI-TOF MS and finally confirmed by gene sequencing, which posed a question of the accuracy of identification in previously reported infections by A. ureae . In our case, we not only conducted traditional phenotypic testing but also performed MALDI-TOF MS and 16S rRNA sequencing, proving the identification achieved high reliability.…”

Whole genome sequencing to study antimicrobial resistance and RTX virulence genes in equine Actinobacillus isolates

“…While focussing on equine clinical strains, also novel phenotypic and genetic data on acquired resistance in A. equuli were obtained. In general, identification of A. equuli is considered difficult due to its close relationship to A. suis [ 32 , 56 ]. The use of the 16S rRNA gene was compared to a new MLST and whole genome SNP, showing that 16S rRNA gene sequencing was indeed least reliable in differentiating Actinobacillus species, while whole genome SNP analysis performed best.…”

“…We considered identifications with a log score value > 2.0 to be reliable at the species level. Considering that equine Actinobacillus species may not be easily distinguished, even with MALDI-TOF MS or 16S rRNA gene sequencing [ 32 , 33 ], further identification based on WGS data was performed, as described below. Pure cultures of all isolates were stored at −80 °C for further analysis.…”