PathogenesisClinical pictureLab treatment amp Prophylaxis By Syed Nafeez Pathogenesis BPertussis is an obligate human parasite surviving only for ID: 613908
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Slide1
PERTUSSIS
Pathogenesis,Clinical picture,Lab ∆,treatment & Prophylaxis
By
Syed
NafeezSlide2
Pathogenesis:
B.Pertussis is an obligate human parasite, surviving only for brief
periods
outside
the host.
Source
:
Early
cases,particularly in catarrhal stage
Carriers
Fomites
Mode of transmission:
Inhalation of
infected
aerosols
(
droplet
infection)
Habit:
localized
in
cilia
of
resp.epitelium,doesn’t
invade
the
bloodstreamSlide3
Infected cilia by
B.pertussis bacilli
bacillus
ciliaSlide4
Mechanism:
Droplet nuclei containing B.pertussis are inhaledAdherence &
rapid
multiplication on
cilia
of
resp.epithelium
of
nasopharynx,trachea
&
bronchiLiberation of
toxins
(PT,TCT)&
other substances…(FHA,AC)Paralyse cilia causing insitu Θ of natural defences of resp.tract secondary infections Irritate cells excessive secretions cough & catarrhal sympt Necrosis with polymorphonuclear obstruction of bronchioles ATELECTASIS infiltration diminished oxygenationInterstitial pneumonia,bronchopneumonia contributes to↑frequency of convulsions in infantsSlide5
Title
ContentSlide6
Host response:
Humoral response by the production of IgA & pertussis toxin antibodies is effective.
These
prevent
attachment
of the
bacillus
.Slide7
Clinical picture:
Pertussis has an insidious onset after an IP of 1-2 weeks & a protracted course comprising of 3 stages:
Catarrhal stage
Paroxysmal stage
Convalescent stage
Each
lasting for an
approximate
of 2
weeksSlide8
Catarrhal stage:
There’s -low grade fever,malaise -catarrhal symptoms-sneezing,
rhinorrhoea
&
lacrimation
-
dry,irritating
cough
During
this
stage the person is highly infectious as large number of bacilli are sprayed in the dropletsThe disease can be arrested at this stage by antibiotic treatment but ∆
is very difficult ‘coz
of its resemblance to typical VIRAL URI wit
flu like symptoms. Slide9
Paroxysmal stage:
Characterised by distinctive bouts of ↑frequency & intensity of cough that’s explosive in natureDuring
each
bout,the
patient
experiences
violent
spasms
of continuous
coughing that almost
empties
the
lungs following which there’s deep inspiration that produces the characteristic ‘WHOOP’The patient’s exhausted at the end of each bout.Post tussive vomiting,cyanosis & convulsions may occur.Young infants become apnoeic.Slide10Slide11
About 40-80 bouts
occur throughout the day,more severe at night,yielding thick
mucous
plugs
.
‘WHOOP’ & major complications
occur
predominantly
in children
The paroxysmal
coughing
predominates in older children & adults.Slide12
T
Blood changes are distinctive & aid in ∆.There’s marked Leucocytosis with an absolute lymphocytosis
.
TLC
-16,000-30,000/
μ
L with 60-80% being lymphocytes
lymphocytes in this blood smear from an 18-month-old child with
the
infection have
lobulated nuclei.The cytology of the cells could be mistaken for neoplastic lymphocytes.
Lymphocytes with lobulated nucleiSlide13
Convalescent stage:
There’s ↓frequency & severity of cough.The disease lasts for 6-8 weeks,though it
maybe
very
protracted
as in
premature
infants,the malnourished, immunocompromised,people with
genetic
susceptibility.Slide14
Complications:
Pulmonary-pneumonia -sc emphysema -atelectasis
Neurological
-epilepsy,paralysis
Miscellaneous
-
haemorrhage
(
sub-conjunctival,epistaxis
) -
otitis
media
-dehydration,malnutritionIn adults-rib fractures,back pain,hearing loss,urinary incontinence,hernias,rectal prolapse.
Directly by B.pertussis
Secondary infections
aspirationalSlide15
Lab ∆:
Specimens: nasopharyngeal secretions blood(serum) for serological testing
These
are
processed
through
:
Culture
Direct Fluorescent Ab
testing
Serological
techniques-Ab
titres,ELISAPCRSlide16
Culture:
Nasopharyngeal secretions required for culture are collected by following 4 methods:1)
Cough
plate
method
:
A culture plate of Bordet Gengou
Glycerine
Potato
Blood Agar is held
10-15 cm
infront
of patient’s mouth during a bout of spontaneous or induced cough,such that the resp. exudate impinges directly on the medium.The plate’s sealed & incubated for 48-72 hrs.Advantage is that the
specimen is innoculated
directly,at bedside.
Slide17
2)Pernasal
swab:A swab (dacron or calcium alginate) mounted on a flexible nichrome wire, is passed
along
the
floor
of nasal
cavity
&
material
collected from the pharyngeal
wall
.
Yields the highest % of isolation.Slide18
3)Nasopharyngeal aspiration:
Collected through a soft catheter attached to a syringeIs the ‘preferred’
specimen
.
4)
Postnasal
/
peroral
swab
:
A
cotton
swab(West’s post nasal swab) is passed through mouth & secretions from posterior pharyngeal wall,collected.There’s possibility of salivary contamination.Slide19
Specimens
should be innoculated immediately on BGGPB Agar or its modifications like Lacey’s
DFP medium
In case of
delay,transport
media are
used
:
0.25-0.5 ml of
Casamino
acid
solution,pH
-7.2
Modified Stuart’s mediumMischulow’s charcoal agarModified Regan-Lowe medium:Is a ½ strength charcoal agar supplemented with 10% horse blood & cephalexin(40mg/L)It Θ growth of nasopharyngeal flora.Is also the
medium of choice for culture.Culture plates are incubated for 7 days at high humidity & temperature of 35-36̊ C .
Should be checked for any growth after 48-72 hrs of innoculation & periodically thereafter.Slide20
A positive culture shows the
characteristic ‘bisected pearls’ or ‘mercury drop’ colonies.
Confluent
growth
shows aluminium
paint
appearance
Microscopy
shows a non
motile,gram
negative bacillus.Slide21
Direct FA
testing:Used to identify the bacillus either in direct smears of clinical
specimens
or
from
culture.
Is
inexpensive
.
Provides rapid
diagnosis
&
yields positive results when cultures are negative due to use of antibiotics.Lacks specificity & sensitivity due to cross-reactions with nasopharyngeal flora…..hence,unreliable & no longer recommended.Slide22
Serological techniques:
Focus on identifying significant variations in IgG & IgA titres(upto 4 fold ↑) against
relavant
B.pertussis
virulence
factors
in
both
acute & convalescent phases of the
disease
.Hence,for accurate
∆,
serum
samples in both phases of disease are to be collected.Rise in Ab titres is demonstrated by:Agglutination not helpful as the rise in agglutinating &Gel precipitation precipitating Abs doesn’t occur untill 3rd week
Complement fixation tests of illness
ELISA- highly specific
Proposed as diagnostic method in culture sensitive casesA
significant ↑ in titres(8E -2fold) between acute & convalescent phase is diagnostic of the
diseaseSlide23
PCR:
Most sensitive method to ∆ PertussisSpecimen used – nasopharyngeal aspiration
Primers
for
both
B.pertussis
&
B.parapertussis
should be included
Gives
positive
results even when the organism can’t be cultured.THE BOTTOM LINE:A major problem is the lack of access to diagnostic laboratory methods. Many routine laboratories are not equipped for the diagnosis of B. pertussis infection.
This is the result of a general medical misconception that B. pertussis infection does not frequently occur in the populationSlide24
Treatment:
B.Pertussis isn’t susceptible to penicillinsErythromycin is DOC adults
-250-500mg/6th
hr
14
days
children
-30-60mg/kg/
day
Clarithromycin
Azithromycin
Cotrimoxazole
Chloremphenicol Cough sedatives are not usefulCorticosteroids reserved in severe cases, reduce duration of paroxysmal stage.Adrenergic ᵦ2 stimulants,reduce severity of paroxysms, more useful in infants. Slide25
Prophylaxis:
Preventing the spread of disease by isolation isn’t preferred as max.infectivity is in early stage
when
∆
is
difficult
.
Hence,prophylactic
measures mainly include:
immunoprophylaxis
Vaccines
currently used:DPT/DTwP/Triple antigen vaccineDTaPTdapChemoprophylaxisGeneral prophylaxisSlide26
Immunoprophylaxis:
1)DPT/DTwP/Triple antigen vaccine:Composed of
diphteria
&
tetanus
toxoids,killed
B.pertussis
(
smooth phase-1 strain)adsorbed on aluminium phosphate.thiomersol
as
preservative
Dosing schedule:3 Primary doses-at 6,10 & 14 weeks of life2 Booster doses-1st booster at 15-18 months -2nd at 5 years Dose & route:0.5 ml,IMSite: AL aspect of thigh in infants
or deltoid Slide27
Side
-effects:Minor reactions:Localized
to
site-soreness,swelling,redness
Systemic-fever,fussiness,drowsiness,anorexia
Moderate
reactions
:
Seen
in about 1:100/1000
shots
:
Crying non-stop for 3 hrs or moreFever of 105̊ F or moreLess often in about 1:1750 shots:Seizures(convulsions,spasms,staring spells)Collapse or fainting-child becomes blue,pale,limp & non-responsive
Severe reactions:rareProlonged
seizures,↓consciousness,coma,permanent brain damage &
death.!!!DPT vaccine is
contraindicated if moderate to
severe reactions
occur.Also contraindicated
below 6 weeks of life & above
6 yrs
Last for 1-2 days
Treat with analgesicsSlide28
2)
DTaP Vaccine: Is an acellular vaccine with pertussis
component
consisiting
of
inactivated
pertussis
toxin, filamentous
hemagglutinin
,
pertactin
, or
fimbriae
along with diphteria & tetanus toxoids in concentrations similar to DTwP vaccine.Indicated for children of 6 weeks-6 years of life.Dosing schedule is the same.Slide29
3)Tdap
vaccine: Is an acellular vaccine with concentrations of diphteria toxoid & pertussis component
reduced
to
1/10
of
DTaP
vaccine.
for adolescents between the ages of 10 and 18 years
preservative free (which means that, like most new vaccines, it doesn't contain
thimerosal
)
A similar
Tdap vaccine, Adacel, is being reviewed by the FDA & might be available for people between the ages of 11 and 64, which would be good news for adults who also want protection against pertussis.Slide30
Prevention and treatment prophylaxis of secondary cases
The CDC has defined a close contact as:someone having face-to-face exposure within 3 feet of a symptomatic patient someone who has had direct contact with respiratory, oral, or nasal secretions from a symptomatic patient someone who has shared the same confined space for more than 1 hour with a symptomatic person.
Chemoprophylaxis is given with recommended antibiotics and dosage
regimens,identical
to those used for treatment of active infection.
should be started in the
asympto-matic
person within 21 days of cough onset in the index patient.
highly recommended for all children younger than 12 months and women in the third trimester of pregnancy who have been exposed to
pertussis
Slide31
Epidemiology:
Predominantly a pediatric disease.Incidence & mortality highest in
1st
year
of life.
Common in
females
than
males
at all ages.
Worldwide
distribution
with most deaths occuring in Africa, Asia,central & latin America.Occurs endemically & epidemicallyIn recent years,there’s been resurgence of the disease in USA & eastern european countriesAlso,there’s
an ↑ in number of cases being reported in
Asia. Slide32
The Statistics:
According to WHO estimates,around 2.95 lakh persons died of whooping cough in 2002.
In
developing
countries,the
case
fatality
rates range
from
4-15% in infantsAbout 10% of cases & 50% of
deaths
occur in children <1yrIn India, there’s been marked decline in reported cases from 1987-2005 year cases reported 1987 1.63 lakh 2002 26700 2005 43955Slide33
THANK YOUSlide34
XCUSE me
if u have slept through!!
&