Class 15. Infections of the Central Nervous System

Transcription

1 English Division 6 E.D. Class 15 Infections of the Central Nervous System Pathogenesis, etiologic agents, clinical symptoms, and laboratory diagnosis To be performed: - Read carefully attached case studies and discuss them with your teacher. o Consider the results of CSF examination o Gram-staining of cultured CSF and blood samples from authomated system bottles (BacT/Alert) Demonstrations: o Gram stained slides of the most important bacterial agents of meningitis o Growth of S. pneumoniae, N. meningitidis and H. influenzae on enriched media o s of ELISA tests for antigen detection of H. influenzae, S. pneumoniae and N. meningitidis for cases 1, 2 and 3 in CSF and blood samples. o Bacteria cultured from clinical samples taken in cases 1-3 Maciej Przybylski, Ph. D. 1

2 After revision of clinical cases, see instructions on page 3 Case 1 An eleven-month-old boy was admitted with lowered consciousness, generalized pain and progressive fever since 24 hours. Since one day he had been suffering from rhinorrhea as well and since two days from loose stools, he also stopped feeding. Previously he had been in a healthy condition. He was appropriately vaccinated, ihe also received vaccine against Haemophilus influenzae type b (Hib), at the age of three, four and five months. The family history revealed a brother who had a bacterial meningitis at young age (no detailed data available). On examination a sick infant with an impaired peripheral circulation was seen. The heart rate was 200/min, respiration 75/min. Blood pressure was 120/68 mm Hg; body temperature 41.5ºC. On his back petechiae were present; severe neck stiffness and slight opisthotonus were observed. No ear, nose, throat, cardiac, pulmonal or abdominal abnormalities were found. Shortly after admission child was vomiting. Table I for Case 1. Urine microscopy <1 white blood cell/mm 3 opalescent CSF White cell count 670/mm 3, predominantly neutrophils CSF RBC count 10/mm 3 1,7 g/l (normal: 0,15 0,44 g/l) 1,9 mmol/l (normal: 2,5 4,4 mmol/l) 7,5 mmol/l (normal: 4,4 6,1 mmol/l) CSF direct Gram-stain Gram- rods slide Gram stain to be performed.? See culture plates. Gram stain to be performed.? CSF/blood antigen detection See demonstration ELISA plate.? Blood WBC count 13,7 x 10 9 /mm 3 with 71% neutrophils Urea and electrolytes Normal Case 2. A 4-year-old child presented with a 6-day history of lethargy, pyrexia and vomiting. She had not received any recent antibiotics and there was no history of infectious contacts. There was no significant past medical history or family history; in particular, she had had no similar presentations previously and was thriving. Examination revealed she had mild pyrexia of 37.7 C. She was alert but irritable on handling with no other signs of meningism. There were no other positive findings. Blood investigations revealed the following: haemoglobin 10.6 g/dl; leucocytes /l; neutrophils /l; platelets /l; C-reactive protein (CRP) 286 mg/l; serum glucose 4.5 mmol/l. Urea and electrolytes and liver function tests were normal. Urine microscopy and throat swab were. Chest X-ray was unremarkable. Microbiological blood cultures are after 36 hours of incubation. A lumbar puncture was performed using aseptic technique and cerebrospinal fluid (CSF) obtained: clear CSF white cell count 350/mm 3, 60% neutrophils, 40% mononuclears CSF RBC count 8/mm 3 1,9 g/l 1,9 mmol/l 4,5 mmol/l Blood culture slide Gram-positive cocci slide Gram stain to be performed. See culture plates. Gram stain to be performed. CSF/blood antigen detection See demonstration ELISA plate.? CSF direct Gram-stain No organisms visible 2

3 Case 3. Female patient (43) was admitted to the hospital with a history of abdominal pain lasting for over three weeks. Three days before the admission pain became much more severe. Shortly after admission she developed symptoms of peritonitis. Laparoscopic examination revealed enterocolitis and appendicitis. Appendectomy was performed. After the surgery, patient started to run temperature of 38,5ºC. Second day after surgery she has had headache and neck stiffness. Kernig s sign was positive. Intravenous ampicillin was administered. Table I for Case 3 NMR scan enlargement of cerebral ventricles, no localized inflammatory focuses in brain and cerebellum slightly turbid, reddish White cell count 300/mm 3, predominantly neutrophils RBC count 50/mm 3 1,2 g/l 3,1 mmol/l 6,3 mmol/l CSF direct Gram-stain No organisms were seen. slide Gram stain to be performed. See culture plates. Gram stain to be performed. CSF/blood antigen detection See demonstration ELISA plate.? Blood culture Negative CSF/blood antigen detection See demonstration ELISA plate.? Blood WBC count 17,3 x 10 6 /mm 3 with 94% neutrophils and 3,9% lymphocytes CRP in serum 64,6 mg/l (normal 0 10) Urea and electrolytes Normal Ventriculostomy with fluid drainage was performed, and after therapy with ampicillin the patient s condition improved. On the third day after the surgery patient suffered from neurological disorders: disorientation with subsequent behavioral changes and eventual lost of consciousness. Temperature was as high as 39 C with tachycardia 110/min and blood pressure 100/68 mm Hg. s of examinations performed at the third day after ventriculostomy are presented in Tab. II. Table II for Case 3 NMR scan ischaemic area in upper part of brain stem clear White cell count 13/mm 3, all lymphocytes, no RBCs 1,9 g/l 3,7 mmol/l 5,7 mmol/l CSF Gram stain No organisms were seen Blood culture Blood WBC count 13,5 x 10 6 /mm 3 with 78% neutrophils and 7,6% lymphocytes CRP in serum 32,2 mg/l (normal 0 10) Urea and electrolytes Normal Because of worsened patient s status accompanied with blood and s results, PCRhybridization was performed in CSF sample with primers and probes specific to the infectious agents known to cause infections in central nervous system. s are presented in Tab. III. Table III for Case 3 Cryptococcus neoformans antigen (CSF) TB complex DNA (CSF) HSV-1 DNA (CSF) HSV-2 DNA (CSF) VZV DNA (CSF) CMV DNA (CSF) CMV DNA (blood) positive 3

4 Instructions: For each case, on the table there are plates with the bacteria cultured from appropriate clinical specimens, as well as fixed slides ready to be stained prepared from blood/csf samples cultured in authomated systems. Please perform: 1. Gram-stained slide from cultured CSF 2. Asses bacterial growth on bacteriological media, perform available identification tests (including Gramstained s: Case 1. Gram stained slide: Case 2. Gram stained slide: Case 3. Gram stained slide: Cultured on: Cultured on: Cultured on: Culture results: Culture results: Culture results: 4

5 Common etiologic species Other etiologic species (rare) Haemophilus influenzae Neisseria meningitidis Streptococcus pneumoniae Staphylococcus epidermidis Escherichia coli Klebsiella pneumoniae Pseudomonas aeruginosa Nocardia spp. Viridans streptococci Enterobacter spp. Proteus spp. Citrobacter spp. Microbial causes of meningitis Acute bacterial meningitis Acute viral meningitis Chronic meningitidis Listeria monocytogenes Streptococcus agalactiae Flavobacterium spp. Moraxella spp. Propionibacterium acnes Enterococcus faecalis Salmonella spp. Streptococcus pyogenes Serratia spp. Acinetobacter spp. Pasteurella multocida Aeromonas spp. Enteroviruses Mumps Herpes simplex Varicella-zoster virus Adenoviruses HIV Morbilivirus Rubivirus Epstein-Barr virus Arboviruses Viruses Mumps virus HSV-1/HSV-2 Varicella-zoster virus Arboviruses Flaviviruses Echoviruses Bacteria Mycobacterium tuberculosis Brucella spp. Treponema pallidum Leptospira spp. Nocardia spp. Actinomyces spp. Listeria monocytogenes Very rare agents Spirochetes Mycobacteria Borrelia spp. Rickettsiae Leptospira Brucella spp. Naegleria spp. Fungi Cryptococcus neoformans Coccidoides immitis Histoplasma capsulatum Candida spp. Sporothrix schenckii Aspergillus spp. Likely pathogens and predisposing conditions for brain abscesses Predisposing condition Otitis media or mastoiditis Paranasal sinusitis Dental infection or manipulation Trauma or neurosurgery Cyanotic heart disease Pyogenic lung disease Bacterial endocarditis Gastrointestinal source T-lymphocyte deficiency Neutropenia Pathogens Fusobacterium spp. Coagulase- staphylococci Pseudomonas aeruginosa Haemophilus spp. Nocardia asteroides Actinomyces spp. Fusobacterium spp. Viridans streptococci Enterococci Haemophilus spp. Nocardia spp. Pseudomonas aeruginosa Fungi, especially Aspergillus, Mucor and Rhizopus 5

6 Comments for class 22 (CNS infections) Case 1. Possible causes and laboratory confirmation Patient presents signs of bacterial meningitis, which can be due to Neisseria meningitidis, Haemophilus influenzae type b or Streptococcus pneumoniae. Differential diagnosis should be based on CSF examination, cultures of CSF and blood, and bacterial antigen detection in CSF and blood (if possible). Additional examination comprises full blood count, urea and electrolytes. Management Intravenous cefotaxime for 7-10 days is advised by international guidelines. Delay in therapy is correlated with increased mortality risk and should not exceed 30 minutes since decision is taken. Children (>4 weeks old) who are being treated for possible meningitis (who have not yet received parenteral antibiotics, or who have received their first dose less than 1 hour ago) should be given dexamethasone (steroid). The vaccines against Hib are very safe and highly effective. By the age of 6 months, every infant should receive at least three doses (at the age of three, four and five months). A fourth dose (booster) should be given to children between 12 and 18 months of age. Vaccination failure can be either caused by an immune deficiency or by decreased affinity of the available antibodies, which both may show a genetic (family-related) tendency. If immune deficiency is considered, particularly deficient anti-hib immunoglobulin levels (most often IgG2 or IgM) were found in previous studied as a cases of vaccination failure. Similar to this, revieved patient showed low levels of specific anti-hib IgG and IgM. This is thought to be due to a slow learning effect of the immune system (see chart below) Complications Advanced Haemophilus influenzae type b meningitis can lead to brain damage, coma, and death. Survivors can suffer longterm complications, including hearing loss, mental retardation, paralysis, and seizures. Current evidence suggests that steroids protect against neurological sequelae from bacterial meningitis and may reduce mortality. The benefit is probably greatest if steroids are given at least 15 minutes before the first dose of antibiotics. Case 2. Acute meningitis (SAM) is an infrequent event, with an incidence of % of cases in various series. In children, SAM occurs primarily in those with known pre-existing abnormalities of the central nervous system (CNS) such as previous neurosurgery or trauma (mostly placement or revision of a ventriculo-peritoneal shunt). Other reasons of SAM include immunosuppression and occult CNS abnormalities. It is vital to detect such an abnormalities as they may predispose to recurrent episodes of meningitis. For example, intraspinal epidermoid cysts are very rare, but can cause recurrent episodes of bacterial meningitis via dermal sinus tracts that allow communication between the surface of the skin and the subarachnoid space. Therefore thorough clinical examination should be performed in all cases of unexplained SAM to look for cutaneous stigmata of underlying CNS abnormality such as dermal sinus tracts, skin depressions or abnormal hair follicle implantation. This highlights the importance of performing neuroimaging of the head and spine, in addition to a thorough clinical examination, to allow detection of all occult abnormalities. MRI is the imaging of choice of the spine as CT may miss subtle but important findings. Less frequently, SAM may also be caused by secondary haematogenous spread from distant primary foci such as endocarditis or bronchopneumonia, or by direct local spread from a parameningeal focus such as sinusitis, cavernous sinus thrombosis, vertebral osteomyelitis or extradural abscess. Case 3. Shortly after appendectomy patient suffered from meningitis. In the performed NMR scan, except ventricles dilatation, no intracranial focuses were detected, what indicated a need for endoscope-ventriculostomy. In the cultured blood sample Staphylococcus haemolyticus was detected once, and ampicillin-resistant Listeria monocytogenes was detected in CSF sample. Staphylococcus haemolyticus was not detected in the subsequent blood samples and was considered as a contamination from the skin. Antibacterial therapy against L. monocytogenes gave positive result (subsidence of symptoms, improvement in the CSF parameters, ). After next two days, deterioration occurred, and further examination were performed. Symptoms were characteristic rather for viral encephalitis than for meningitis. Although detection of pathogens antigens or nucleic acids in the CSF would give unambiguous answer, number of nucleic acid copies or antigen load during encephalitis may be below the detection limit of regular technology. PCR modifications leading to sensitivity augmentation are used (nested PCR, PCR-fluorescent hybridization, real-time PCR). In the reviewed case, all results were, except HSV-1 DNA detection in cerebrospinal fluid. PCR results gave the evidence of HSV-1 as the causative agent of encephalitis, therefore intravenous acyclovir should be started immediately together with other general supportive measures. Encephalitis is often a localized infection with lesser reaction of the immune system, but serum and CSF sample testing for virus-specific IgM-class antibodies against HSV or echoviruses, Coxsackieviruses or mumps may be helpful in the situation, when there are results of direct laboratory microbiological diagnosis (pathogen detection). Commonly observed pathogenetic changes during HSV-1 encephalitis comprise perineural inflammatory infiltration and degenerative changes of neurons. Ischaemic effects of HSV-1 infection of the CNS are rare, but may be present. Decreased number of lymphocytes in peripheral blood (20-30% of normal count) was one of the possible risk factors exposing patient to the infections. 6