Download Lecture 1 Bacterial meningitis

Lecture 2
Epidemiology of meninigitis
Dr. Abdelraouf A. Elmanama
Islamic University-Gaza
Medical Technology Department
Lecture outlines
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Epidemiology of menigitis
Risk factors of meningitis
Pathogens details
Vaccines
Prophylactics
Introduction to Lab diagnosis
Epidemiology
– Incidence is between 3-5 per 100,000
– More than 2,000 deaths annually in the U.S.
– Relative frequency of bacterial species varies
with age.
Epidemiology
– Neonates (< 1 Month)
• Gm (-) bacilli 50-60%
• Grp B Strep 20-40%
• Listeria sp. 2-10%
• H. influenza 0-3%
• S. pneumo 0-5%
Epidemiology
– Children (1 month to 15 years)
• H. influenzae
40-60%
– Declining dramatically in many geographic
regions
• N. meningitidis 25-40%
• S. pneumo
10-20%
Epidemiology
– Adults (> 15 years)
• S. pneumo
• N. Meningitidis
30-50%
10-35%
– Major cause in epidemics
• Gm (-) Bacilli
1-10%
– Elderly
• S. aureus
• H. influenzae
5-15%
1-3%
– >60 include Listeria, E. coli, Pseudomonas
Risk factors
• Age .
• Most cases of viral meningitis occur in children
younger than age 5.
• In the past, bacterial meningitis also usually
affected young children.
• But since the mid-1980s, as a result of the
protection offered by current childhood vaccines,
the median age at which bacterial meningitis is
diagnosed has shifted from 15 months to 25
years .
Risk factors
• Living in a community setting .
• College students living in dormitories,
personnel on military bases, and
• children in boarding schools and
• child care facilities
• are at increased risk of meningococcal
meningitis, probably because infectious
diseases tend to spread quickly wherever
large groups of people congregate .
Risk factors
• Pregnancy .If you're pregnant, you're at
increased of contracting listeriosis — an
infection caused by listeria bacteria, which
may also cause meningitis. If you have
listeriosis, your unborn baby is at risk, too .
Risk factors
• Working with animals .People who work
with domestic animals, including dairy
farmers and ranchers, have a higher risk
of contracting listeria, which can lead to
meningitis .
Risk factors
• Compromised immune system .Factors
that may compromise your immune
system —
• including AIDS, diabetes and use of
immunosuppressant drugs — also make
you more susceptible to meningitis.
• Removal of your spleen, an important part
of your immune system, also may increase
your risk .
Risk factors
• Alcoholism
• Autoimmune disorders (e.g., lupus(
• Immunosuppressive drugs (e.g., corticosteroids,
chemotherapies(
• Intravenous drug abuse
• cancer, diabetes
• Smoking
• Head injuries and brain surgery also put patients at risk
for meningitis
Meningitis Pathogens
• L. monocytogenes
Morphology and general
characteristics
– Small G+ B which may appear pleomorphic
– Nonsporing and nonencapsulated
– Motile by peritrichous flagella at RT (umbrella
motility) and polar flagella at 370 C.
Listeria umbrella motility at RT
L. monocytogenes
– Grows well on ordinary lab media and on CBA
it produces beta hemolysis and colonies
resemble Strep. pyogenes colonies
– Aerobic to microaerophilic
• Biochemistry
– Catalase +
– TSI= A/A, H2S– Esculin hydrolysis +
Esculin hydrolysis
Catalase; bubbles production
Typical Listeria rxn
Listeria on BA
– CAMP +
– Grows in 6.5% NaCl
• Antigenic structure
– Four major serogroups (1-4) based on O
antigen
– Serotypes based on H antigen
– Type 1b accounts for most infections;
– May also find 1a and 4b in significant
amounts
Listeria pathogenesis
Listeria pathogenesis
– Pregnancy renders an individual more susceptible to
the infection, though the effect on the mom is usually
minimal. It can be devastating for the fetus or
newborn.
– In neonates, the disease occurs in two forms
• Early onset – the infant is infected transplacentally with the
production of septicemia and granulomatous foci in many
organs. This may result in abortion, stillbirth, premature
delivery, or death soon after birth. The baby is born with
cardio and respiratory distress, vomiting, diarrhea,
meningitis, hepatosplenomegaly, and skin lesions. The
fatality rate is 70-90% in untreated cases.
Listeria pathogenesis
• Late onset – the infant is infected from the
genital tract during delivery. Infection usually
begins 1-4 weeks after birth and is manifested
as meningitis with a high fatality rate.
– Antimicrobic susceptibility/treatment
• Prognosis is poor in neonates so infected
moms should be treated as soon as disease is
diagnosed
• Penicillin is the drug of choice. Can also use
erhthromycin or tetracycline.
Streptococcus pneumoniae
Morphology and general
characteristics
MORPHOLOGY
• Gram-positive cocci – lancet / bullet shape
• Diplococci (arranged in pairs) – the adjacent ends of
pair are rounded while other ends are pointed
• Virulent strains are capsulated
CULTURAL CHARACTERISTICS
° Facultative anaerobic; 5-10% CO2 enhance growth
° Grow on enriched media (blood & chocolate agar)
PATHOGENICITY FACTORS
Capsule
• Antiphagocytic
• S. pneumoniae > 80 serotypes on the basis of
antigenic differences in polysaccharide capsule
Toxins and extracellular enzymes
° IgA protease : help in colonization in resp tract
° Pneumolysin - properties like Streptolysin
° Neuroaminidase – spreading factor
•10-30% of normal people carry one or
•more serotypes in throat
•Pneumococcal pneumonia
–High grade fever, cough, rusty sputum
(reddish)
–Difficult breathing, chest pain
•Meningitis (all age groups)
•Sinusitis
•Otitis media
•TREATMENT
• Penicillins – drugs of choice
–Penicillin-resistant strains are treated with erythromycin
•PREVENTION
• Vaccination with polyvalent vaccine prepared
from
polysaccharide capsules of 23 serotypes
• Given to susceptible groups – elderly patients,
diabetics, chronic pulmonary disease,
immunocompromised
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Susceptibility
Children< 2, adults over 65,
Splenectomy,
Chronic lymphatic leukemia, Multiple myeloma,
Sickle cell anemia,
Postinfluenza,
COPD, smokers
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Clinical Features
Rusty sputum Single shaking chill
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Associated Sites of Infection
Bacteremia 25-50%
Pleural effusions, arthritis, meningitis, endocarditis Sinusitis
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Sputum Gram Stain
Encapsulated lancet-shaped Gram-positive diplococci or short chains
Laboratory diagnosis of
S. pneumoniae
• CULTURAL CHARACTERISTICS
• Facultative anaerobic; 5-10% CO2
enhance growth
• Grow on enriched media (blood &
chocolate agar)
• Alpha-haemolytic colonies on blood agar
Optochin
Bile solubility
Quellung reaction
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TREATMENT
Penicillins – drugs of choice
Penicillin-resistant strains have been reported due to
alteration in PBP
Penicillin-resistant strains are treated with erythromycin
PREVENTION
Vaccination with polyvalent vaccine prepared from
polysaccharide capsules of 23 serotypes.
• Given to susceptible groups – elderly patients, diabetics,
chronic pulmonary disease, immunocompromised.
HAEMOPHILUS
• IMPORTANT SPECIES
• H. influenzae
• H. ducreyi
• H. influenzae
• Gram-negative coccobacilli
• Some strains capsulated
• Six serotypes (a-f) on the basis of capsular antigens
• Type b (Hib)- the main pathogen
• Non-capsulated strains are present in nasopharynx of 2580% of healthy people
• Hib in 2-5% of healthy people
Haemophilus influenzae
Growth Requirements
• Growth improved in CO2
• Grow on enriched media (chocolate agar)
• Needs X factor (haematin) & V factor Nicotinamide Adenine
Dinuclotide (NAD)
° Both are present in RBCs and are released
on heating (chocolate agar)
° V- factor can be produced by yeast & S. aureus
° H. influenzae can grow on blood agar in vicinity
of colony of S. aureus - satellitism
SATELLITISM BY H. INFLUENZAE
H. influenzae
colonies
S. aureus
Blood agar
plate
PATHOGENESIS
Type b (capsulated)
• Is primary pathogen
• IgA protease - degrades secretory IgA
and help attachment to respiratory mucosa
• Capsule - antiphagocytic
• Endotoxins
Gram negative bacilli
Enterobacteriacae and Others
• MacConkey agar is good for almost all
gram negative (there are few exceptions)
• Oxidase test for preliminary differentiation
• TSIA for initial identification
• API 20 E is for species identification
Oxidase test
TSIA
API 20 E
API 20 E Flash
Thank you