MICRO Flashcards
1
Q
Outline four (4) ways in which viruses can bypass the blood brain barrier and enter the central nervous system (6)
A
- Entering the nervous system outside the CNS – 1) retrograde spread via axons (e.g. HSV, rabies); 2) anterograde spread via olfactory nerves (VZV, HSV, influenza)
- Direct crossing of the BBB – 3) BBB blood vessel endothelial infection; 4) Trojan horse (crossing by infecting cells that cross the BBB, e.g. lymphocytes, macrophages (e.g. HIV, CMV)
2
Q
Describe the anatomical differences between meningitis, encephalitis, and myelitis (3)
A
Meningitis = inflammation of meninges, encephalitis - ~ of brain parenchyma, myelitis = ~ of spinal cord,
3
Q
Myelitis
A
Inflammation of the spinal cord
4
Q
Meningoencephalitis
A
Inflammation of both meninges and brain parenchyma
5
Q
Encephalomyelitis
A
Inflammation of both the brain and spinal cord
6
Q
Define encephalomyelitis (2)
A
Encephalitis = inflammation of brain parenchyma. Myelitis = inflammation of spinal cord. Encephalomyelitis = inflammation of both simultaneously.
7
Q
Describe acute disseminated encephalomyelitis (4)
A
- Associated with many viral and bacterial infections, e.g. measles, influenza, mumps, etc.
- PIEM = post-infectious encephalomyelitis
- Usually convalescent phase
- Not directly caused by a virus
- Autoimmune reaction
- T-cell response to myelin
8
Q
Name the virus that causes progressive multifocal leukoencephalopathy (½)
A
JC virus
9
Q
State who is at risk of developing this disease (½) [PML]
A
Immunocompromised patient e.g. AIDS
10
Q
Outline the pathogenesis of progressive multifocal leukoencephalopathy (2)
A
JC virus, latent in most of the population. Immunocompromise reactivation
11
Q
State the treatment of progressive multifocal leukoencephalopathy (½)
A
ARVs/ reduce or resolve immunocompromised state
12
Q
Name the fungus that can cause a destructive infection of facial structures and sinuses, and appears as broad non-septate hyphae in tissue (1)
A
Mucor/ Rhizopus – causing mucormycosis
13
Q
Define the terms meningitis and encephalitis (2)
A
Meningitis = inflammation of the meninges Encephalitis = inflammation of the encephalon
14
Q
Name three (3) viral causes of meningitis, and three (3) viral causes of encephalitis (excluding measles and influenza) (3)
A
- Meningitis – mumps, rubella, enterovirus, HIV, arboviruses
- Encephalitis – rabies, mumps, rubella, herpes, varicella, CMV, EBV, HIV, arboviruses
15
Q
Name the lethal form of encephalitis that may develop after infections with certain viruses such as influenza. State the two (2) most significant risk factors for the development of this condition (1½)
A
Reye’s syndrome; age <18y, aspirin ingestion
A rare but serious condition that causes confusion, swelling in the brain and liver damage.
16
Q
Outline two (2) routes by which viruses may spread into the CNS & name one virus as an example of each (3
A
Along motor or sensory peripheral nerves – rabies, HSV; haematogenous spread and disrupt BBB or via “trojan horse”- West Nile virus, HIV
17
Q
Name four viruses that affect the central nervous system and give the typical clinical presentation for each (1½ X 4 = 6)
A
Rabies virus, Herpes simplex virus acute encephalitis
Mumps virus, Enteroviruses (many) aseptic meningitis
Poliovirus 1, 2 and 3 acute flaccid paralysis, aseptic meningitis
18
Q
For which of these is there an effective vaccine? (1½)
A
Poliomyelitis, mumps and rabies
19
Q
Which of these diseases has been targeted for global eradication? (½)
A
Poliomyelitis
20
Q
State which two of the that can cause genital ulceration, can also infect the brain? (2)
A
T. pallidum and H. simplex
21
Q
Outline the pathogenesis of post-infectious encephalomyelitis (2)
A
Molecular mimicry immune response against myelin immune reaction causing inflammation / loss of function.
22
Q
State the key anatomical sites of the pathology of post-infectious encephalomyelitis (acute peri-venous demyelination) and Guillain Barre Syndrome (GBS) (1)
A
demyelination/inflammation of the peripheral nerves; PIEM post infectious encephalomyelitis is due to demyelination/ inflammation of central nervous system.
23
Q
State the most significant anatomical locations affected by post-infectious encephalomyelitis and by poliomyelitis (1)
A
PIEM = white matter; PM = grey matter
24
Q
Compare and contrast herpes simplex meningitis and herpes simplex encephalitis (4)
A
Meningitis: usually HSV-2 with genital reactivation; benign condition not needing treatment (except recurrent meningitis); also may be with HSV-2 primary genital herpes. Encephalitis: urgent acyclovir treatment; mortality high; permanent damage high; HSV-1 more common, worse than HSV-2; viral replication in brain tissue, with preference for temporal lobe.
25
Name one antibiotic currently recommended for the empiric treatment of bacterial meningitis in SA (½)
Cefotaxime/ceftriaxone
26
State the name of the antibiotic which should be administered to all cases of suspected bacterial meningitis and the route of administration (1)
Ceftriaxone given intravenously
27
Explain in terms of both antimicrobial spectrum and pharmacokinetics why this antibiotic is recommended (2)
Covers most common bacteria causing meningitis, including penicillin-resistant S. pneumoniae. Good CSF penetration.
28
If the initial CSF lab results indicate a possible bacterial meningitis, state the empiric antibiotic therapy that would be appropriate while waiting for the bacterial culture and antibiotic sensitivity results. Motivate why this is the antibiotic of choice (2½)
Ceftriaxone/ cefotaxime or “3rd generation cephalosporin” (½)
Covers the 3 common bacteria causing meningitis (1) + (1) for extra information e.g. names of organisms or something about pen resistant pneumococci.
29
Outline two (2) critical principles regarding antibiotic treatment of meningitis (2)
Give first dose as soon as possible within 1-3 hours of arrival (1)
Give higher doses than normal (1)
(Give at correct time intervals/intravenous administration preferable to intramuscular- can get 1 mark for either of these as alternative to higher dose than normal)
30
Briefly describe the mechanism by which glucose in the CSF may be lowered during viral meningoencephalitis (1)
Lymphocyte/ polymorph metabolism
31
Name two causes of meningitis for which there are effective vaccines (2)
Haemophilus influenzae grp B, TB meningitis, Mumps meningitis, Pneumococcus, Meningococcus
32
State four (4) ways in which viruses enter the CNS (2)
- Anterograde neuronal transport
- Retrograde neuronal transport
- Trojan horse transport by lymphocytes/ macrophage line cells
- Infection of endothelium of blood vessels in the BBB
33
Name three (3) common causes of viral meningitis (1½)
Mumps, enteroviruses, herpes simplex, arboviruses
34
Name the three (3) most common causes of uncomplicated viral meningitis (1½)
Mumps, HSV, enteroviruses
35
State which of the viruses that cause meningitis/encephalitis is the most likely to survive for several days to several weeks on a surface, and state why (1)
enteroviruses; non-enveloped, resistant to dehydration
36
Name three (3) viruses that commonly cause aseptic meningitis (1½)
Enteroviruses, mumps virus, Herpes Simplex type 2
37
Name in full two (2) other causes of acute bacterial meningitis. For each organism, briefly outline the age group(s) most commonly affected (4)
- Haemophilus influenzae – young children (rare now due to vaccine)
- Streptococcus pneumoniae – children and adults
- Escherichia coli – neonates
- Listeria monocytogenes – neonates, elderly
- Streptococcus agalactiae (group B streptococcus) – neonates
38
State the full name of the organism causing the meningitis (1)
Neisseria meningitides
39
State where this organism is normally found and how it is transmitted (2) [Neisseria meningitides]
Part of the normal flora of the upper respiratory tract. Transmitted by respiratory droplets
40
State two (2) laboratory tests which may confirm the diagnosis (1)
CSF microscopy and culture, Blood culture, PCR of CSF or blood
41
List four (4) complications, excluding death, of acute bacterial meningitis in infants (2)
Focal neurological deficit: Hearing loss, blindness, intellectual disability, seizures, hydrocephalus
42
State who should be given chemoprophylaxis after contact with a case of meningococcal infection (1½)
Close household contacts, children in the crèche or school class, healthcare workers in close contact with bodily secretions – mouth to mouth, intubation, suctioning.
43
State two (2) antibiotics which may be used as prophylaxis (1)
Ceftriaxone, ciprofloxacin, rifampicin
44
Jason is a 4 y/o who complains of a worsening headache over the course of 2 days. His mother had been treating him with pain syrup but started worrying when he developed a fever, refused to eat and wanted to sleep all the time. She took him to Red Cross Hospital where the paediatrician found that Jason had neck stiffness and signs of raised intracranial pressure. He immediately suspected meningitis and started Jason on antibiotics. Blood cultures & further tests were done to identify the causative organism.
Name the antibiotic that should have been started once meningitis was suspected in Jason (½)
Ceftriaxone/ cefotaxime
45
Neisseria meningitidis is a common cause of meningitis.
State where this organism is normally found in humans (½)
Nasopharynx
46
Name three (3) settings where outbreaks of meningococcal infection may occur (1½)
Military barracks, Boarding schools, Hostels, Creches/pre –school/kindergarten/playschool
47
Ayesha is a 5 y/o girl who is brought into the emergency unit by her mother because she was complaining of a headache and then became very drowsy. O/E the doctor found that Ayesha had neck stiffness. He performed a lumbar puncture and sent the cerebrospinal fluid (CSF) to the laboratory.
Describe the CSF findings for cells, glucose and protein that would make you consider a diagnosis of acute bacterial meningitis (2)
Increased polymorphs (½), decreased glucose (½) (relative to blood glucose) (½) raised protein (½)
48
The finding of organisms on the Gram stain would confirm bacterial meningitis. Given that Ayesha is 5 years old, list the three (3) most likely Gram stain results and give the full name of the organism you would expect for each result (4½)
- Gram-negative (intracellular) diplococci (½) Neisseria (½) meningitidis (½)
- Gram-positive diplococci (½) Streptococcus (½) pneumoniae (½)
- Gram-negative coccobacilli (½) Haemophilus (½) influenzae (½)
49
Name three (3) organisms that can cause the condition named in Question 25 in a child of Sipho’s age (3). Describe the Gram stain appearance of each organism (3)
- Streptococcus pneumoniae – Gram positive cocci in pairs
- Haemophilus influenzae – Pleomorphic Gram negative cocco-bacilli
- Neisseria meningitides – Gram negative diplocococci
50
Give the full name (genus and species) of two organisms that cause acute bacterial meningitis and describe the Gram stain appearance of each (3)
- Streptococcus pneumoniae – gram-positive diplococci (1½)
- Neisseria meningitidis – gram-negative diplococci (intracellular) (1½)
- Haemophilus influenzae – (small) gram-negative bacilli or coccobacilli (1½)
51
Name an antibiotic that is currently recommended as first line therapy for patients presenting with acute bacterial meningitis (1)
Ceftriaxone or cefotaxime (or 3rd generation cephalosporin)
52
Describe how the cerebrospinal fluid (CSF) findings in this condition would differ from those described for TB meningitis (2)
- Predominance of polymorphonuclear cells rather than lymphocytes
- Glucose is lower and or Chloride is normal
53
Name the drug of choice for empiric treatment of meningitis in a child of this age (1)
Third generation (½) cephalosporin (½)
54
Describe the likely laboratory findings on CSF examination in a case of TB meningitis (4)
Increased cells, lymphocyte predominance (2). Raised protein (1). Low glucose (1)
55
State the condition that Dr Johnson was treating when he started ceftriaxone (1)
Acute bacterial meningitis
56
Explain why Dr Johnson started ceftriaxone before the lumbar puncture results were available (2)
Acute bacterial meningitis is a life-threatening condition, and therapy must NEVER be delayed while waiting for lab results/ other investigations.
57
Name in full the organism that caused Frank’s infection (1)
Neisseria meningitidis
58
Briefly outline how this organism is transmitted (1)
From person to person via respiratory droplets
59
State which age group(s) has the highest incidence of infection with this organism (1)
Young children, and teenagers/ young adults
60
This organism can be divided into 13 serogroups. Name three (3) serogroups that are commonly seen in Africa (1½)
Any 3 of A, B, C, W135
61
Outline the recommendations you would give regarding post exposure prophylaxis for this infection (3)
Post exposure prophylaxis (ceftriaxone, ciprofloxacin or rifampicin) should be provided to close household contacts (and in this case would include dormitory contacts), as well as health care workers who performed mouth-to-mouth resuscitation
62
As soon as he arrived in hospital, Frank was started on intravenous antibiotics, even before laboratory results were available. Name the antibiotic that should have been used, and briefly outline why this antibiotic was chosen (2)
- Ceftriaxone / cefotaxime (3rd generation cephalosporin).
- Empiric treatment of acute bacterial meningitis in this age group needs to cover S. pneumoniae, N. meningitidis (and possibly H. influenzae). High rate of penicillin resistance in S. pneumoniae, thus a cephalosporin is used.
63
A Ziehl-Nielsen stain was performed on the CSF. Name in full the organism that can be detected with this stain (1)
Mycobacterium tuberculosis
64
Outline the likely CSF findings in a patient with meningitis due to TB: (you do not need to include actual numbers – indicate whether slightly elevated, elevated, reduced or normal) (2½)
Protein, Glucose, Choride, Slightly-Polymorphonuclear Cells, Lymphocytes
65
Describe the LP findings that would have been seen if Mr George had presented with acute bacterial meningitis (3)
Raised pressure, Turbid fluid (½), Increased leukocytes (½) mainly polys (½), Decreased or absent glucose (½), Increased protein (½), Organisms on Gram stain (½)
66
Name the three most common viruses to cause aseptic meningitis (1½)
Enterovirus, mumps virus, herpes simplex
67
Outline the clinical appearance of uncomplicated aseptic (viral) meningitis (2½)
Fever, headache, neck stiffness, photophobia and vomiting
68
Outline the typical appearance and properties of CSF in cases of aseptic meningitis (3½)
Clear, colourless, low polymorphs, high lymphocytes, normal chloride and glucose, (negative bacterial culture/stain)
69
State how you would confirm the diagnosis of acute pyogenic meningitis (2)
Do lumbar puncture as soon as possible, unless there are contra-indications. In which case do blood culture.
70
List the typical findings on CSF cell count and chemistry in acute pyogenic meningitis (5)
Increased cell count, with polymorphonuclear leucocyte /neutrophil predominance, decreased glucose relative to blood glucose, increased protein, possible organisms seen on Gram stain
71
List the typical findings on CSF cell count and chemistry in acute pyogenic meningitis (5)
Increased cell count, with polymorphonuclear leucocyte /neutrophil predominance, decreased glucose relative to blood glucose, increased protein, possible organisms seen on Gram stain
72
State how you would treat acute pyogenic meningitis. Be as specific as possible (2)
Third generation cephalosporin (ceftriaxone) in high doses intravenously as soon as possible
73
If the base of skull fracture had been diagnosed, give any measures that could have been taken to reduce the risk of patient developing acute pyogenic meningitis (excluding surgical measures) (1)
Vaccination with pneumococcal vaccine
74
Give the full names of the two (2) commonest causes of bacterial meningitis in South Africa in:
Children aged 5 years or more (2)
fants aged less than 2 months (2)
Streptococcus pneumoniae, Neisseria meningitidis
Escherichia coli, Streptococcus agalactiae/Group B streptococcus
75
Cryptococcus neoformans is the commonest cause of meningitis in adults in South Africa (apart from viruses).
Briefly describe the microscopic morphology of C. neoformans (1)
Encapsulated yeast
76
Describe the pathogenesis of this infection (3)
Present in the environment, especially in bird droppings. Inhaled into lungs, causing asymptomatic infection usually. Can disseminate via blood to meninges & other sites of the body, e.g. skin
77
Describe the population at risk of infection (2)
Immunocompromised patients, e.g. persons with advanced HIV and CD4 counts less than 200, other causes of immunosuppression, e.g. malignancy. Occasionally in apparently immunocompetent persons
78
State how patients present with this infection. Describe the clinical features and the time course of presentation (2)
Usually typical features of meningitis, including headache and fever. Usually subacute over days to weeks. Occasionally more rapid onset. Sometimes very subtle and chronic, e.g. personality change. Or even asymptomatic
79
Name an organism other than Neisseria meningitidis in an acute case of bacterial meningitis that requires close contacts to take chemoprophylaxis. Name the organism in full (1)
Haemophilus influenzae
80
If this was a case of neonatal meningitis, name three (3) organisms/organism groups that you would consider as most likely causes (3)
E.coli and other Enterobacteriaceae, Streptococcus agalactiae (Group B Strep) and Listeria monocytogenes
81
A 7-year old boy, woke up one morning with a headache. His mother gave him paracetamol and sent him to school. Mid-morning the school phoned the mother at work and asked her to collect him, as he had started vomiting. He also experienced the room lights as being excessively bright and he said these made his head hurt. His mother rushed him to their local clinic, who asked them both some questions and then examined him. His temperature was 380 C, his consciousness was not impaired, and his neck was stiff. His mother said he had been well since having flu last winter, and only one of his friends had been ill recently, with something very different – a rash on his hands and mouth. She was more concerned that this was caused by an abnormal spine because his younger sister had had an open sore on her lower back when she was born, and walks with difficulty. She was worried that he may be developing the same problem. The GP reassured her that this was not the same thing, and that there was an outbreak of meningitis in the community. He said it was likely not serious, but to exclude serious problems he needed to take blood for blood tests and cerebrospinal fluid for other tests.
List two (2) possible types of organisms responsible for meningitis in this child (1)
Bacteria/viruses
82
Name two (2) examples within each type of organism most likely to cause meningitis (4)
S. pneumoniae, N. meningitidis, enteroviruses, mumps virus
83
Although the mother states that the friend has a different illness, consisting of a rash on the hands and feet.
Name the disease and organism that could potentially have caused illness in both the friend and her son and describe the characteristics of the rash in this disease (2)
Hand, foot and mouth disease due to particular enterovirus. Blisters
84
James presented to a GP in a small Primary Health Care clinic in a rural area, at least 5 hours away from the nearest hospital.
Outline what the GP should do before referring the child. Be as specific as possible (3)
- Take blood culture
- Give antibiotic – ceftriaxone high dose IV/IM
- Supportive therapy- IV access/ check for hypoglycaemia
85
Describe the impact of the introduction of new vaccines into the Expanded Programme of Immunisation in South Africa (over the past 15 years) on the epidemiology of meningitis in children (5)
2 conjugate vaccines introduced: Haemophilus influenza type b and pneumococcal (7 valent, now 13 valent). Both organisms previously common causes of meningitis in children. Has led to significant decrease in Hib disease (now rare) and also decreased incidence of S. pneumoniae meningitis, though it still remains common cause
86
Name two types of meningitis that can largely be prevented by vaccination (2)
Haemophilus influenzae grp B, TB meningitis, Mumps meningitis, (Pneumococcal)
87
Justin was sent home from his grade 1 class because he had a bad headache. By that evening he seemed to have a fever and was irritable and sleepy. His worried mother took him to a private hospital casualty department. When taking Justin’s history Dr Jones noted that his mother had avoided giving Justin routine childhood vaccinations since this clashed with her beliefs in a variety of forms of alternative medicine. Justin was found to have slight unilateral facial swelling, a high temperature, neck stiffness, and was by now vomiting. A lumbar puncture was done and the cerebrospinal fluid (CSF) sample was sent for urgent microscopy and chemistry, with the following results:
```
Cell count: High, predominantly lymphocytes
Glucose: Slightly reduced
Protein: Slightly raised
No organisms seen
Bacterial and viral cultures pending
```
Dr Jones explained to Justin’s mother that it looked as if Justin had a viral meningitis, probably due to Mumps virus. Luckily, most cases resolved completely within 10 days, though mumps meningoencephalitis could have a number of complications, notably deafness.
Explain the features of the CSF laboratory results that led Dr Jones to conclude that Justin’s meningitis was viral (3)
- From the chemistry, normal glucose and slightly raised protein are compatible with viral meningitis. (Low glucose and distinctly raised protein usual in bacterial meningitis.)
- A high WCC with lymphocyte predominance usually indicates a viral infection. Lack of organisms on direct microscopy does not rule out a bacterial infection but makes it less likely.
88
Apart from viral culture, what other method can be used to detect specific viruses in the CSF and is particularly important for (rapid) detection of herpes simplex in cases of suspected herpes simplex encephalitis? (½)
Polymerase Chain Reaction
89
If the initial CSF laboratory results had indicated a bacterial meningitis, what empiric antibiotic therapy would be appropriate while Dr Jones waits for the bacterial culture and antibiotic sensitivity results? (½) Why is this the antibiotic of choice? (2) (½x2 = 2½)
- Ceftriaxone/ cefotaxime or “3rd generation cephalosporin” (½)
- Covers the 3 common bacteria causing meningitis (1) + (1) for extra information e.g. names of organisms or something about pen resistant pneumococci.
90
If the Gram stain had shown gram-negative intracellular diplococci, what diagnosis would you make? (½) What additional treatment measures would you take besides the treatment of the patient with an antibiotic? (1½) (½x1½ = 2)
- Meningococcal meningitis or Neisseria meningitides (½)
- Isolation of patient (½)
- Prophylaxis for close contacts (1)
91
Name in full two (2) common pathogens that appear as Gram negative diplococci, and indicate which would be the one causing the infection in this case (2½)
Neisseria meningitidis – this case. Neisseria gonorrhoeae
92
Outline how this organism is spread and list three (3) settings where outbreaks are likely to occur (2)
- Respiratory droplets from person to person
| - Schools, crèches, hostels, dormitories, military bases
93
Describe what measures can be taken to prevent infection due to this organism at both an individual level (i.e. after exposure) as well as a community level. Include in your answer who should be targeted for preventive measures, and any limitations of these measures (4)
- Post exposure chemoprophylaxis (½) to close household contacts (½), and anyone in intimate contact with respiratory secretions (½).
- Vaccination (½) – usually only in epidemic situations (½), or to asplenic patients or those with complement deficiency (1). Current vaccines do not include serogroup B (½).
94
State the antibiotic of choice for empiric treatment of acute bacterial meningitis (before the causative organism is known), and explain your answer (2)
Ceftriaxone. Many cases meningitis caused by S. pneumoniae, and there is substantial resistance to penicillin among S. pneumonia isolates, hence ceftriaxone is first line therapy
95
The Ziehl Neelsen stain is performed to detect the presence of acid fast bacteria, in particular Mycobacterium tuberculosis. Describe the typical laboratory CSF findings of a patient who has meningitis due to M. tuberculosis (2)
Markedly raised protein, lymphocytes. May be mild elevation neutrophils. Low to normal glucose
96
Give the full names of the three organisms likely to cause meningitis in this age group (3)
Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae
97
Explain why ceftriaxone is the antibiotic chosen for the empiric treatment of meningitis in South Africa (3)
- Covers the common organisms (1)
- Is still active against penicillin-resistant S. pneumoniae (1)
- Therapeutic levels are achieved in the CSF/Crosses the BBB (1)
