Download Bacterial Infections of the Upper Respiratory Tract

Bacterial Infections of the Upper
Respiratory Tract; Streptococcal
Pharyngitis
Group 4
UPPER RESPIRATORY TRACT
INFECTIONS
• Rhinitis
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• Sinusitis
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• Nasopharyngitis(commo •
n cold)
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• Laryngitis
Pharyngitis
Epiglottis
Laryngotracheatis
Tracheatis
Members
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Orimoloye Philip Oluwafemi
Akinlotan Elizabeth
Imaguezegie Grace Ese
Onochie Martins
Cole Oluwafunke
Adelakun Davidson
Dauda Adebisi
Shote Olaitan B.
Bello Mariam Y.
110705136
120705715
120705739
110705134
110705036
120705706
100705065
100705154
120701709
Members
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Ariahu Nonso
Balogun Abdulkhalil
Agboola Tomilola
Amusa Omolabake R.
Toriola Temilola
Adeyemi Barbara
Ogidan Lucky
Ugboke Joshua O.
Odulaja Ayobami O.
110705052
110705055
110705026
110705046
110705156
120705708
110705109
110705158
120705751
Members
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Oladotun Oluwafunmbi O.
Faminu Akin E.
Ndifon Minka
Mokwenye Sylvester
Awosika Oluwakorede I.
120701737
110701016
110705101
120701718
120705722
INTRODUCTION
• The upper respiratory tract consists of the sinuses, nasal passages,
pharynx, larynx which serve as a gateway for air to move into trachea,
bronchi and pulmonary alveolar spaces.
• The respiratory tract is the most common site with infections by pathogens.
• URTIs is a non specific term used to describe acute infections involving the
nose, paranasal sinuses, pharynx, larynx, trachea and bronchi.
• A wide range of organisms can infect the respiratory tract including
VIRUSES, BACTERIA , FUNGI AND PARASITES.
• Viruses cause most URTIs with rhinovirus, parainfluenza, coronavirus,
adenovirus, respiratory syncytial virus. Coxsackie virus, human
metapneumovirus and influenza virus accounting for most cases.
• It represent the most common acute illnesses evaluated in outpatient
settings.
• It ranges from common colds-typically self limited, catarrhal syndrome of
the nasopharynx to the life threatening epiglottis.
Bacteria that cause upper
respiratory tract infections
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Group A beta haemolytic streptococcus
Group C beta haemolytic streptococcus
Corynebacterium diphtheriae
Neisseria gonorrhoea
Arcanobacterium haemolyticum
Chlamydophilia pneumoniae
Mycoplasma pneumoniae
Haemophilus influenza
Moraxella catarrhalis
Bordetella pertussis
Bordetella parapertussis
MODE OF TRANSMISSION
• Transmission of organisms causing URTIs occurs by aerosols,
droplets from coughing and sneezing or direct hand to hand
contact with infected secretions with subsequent passage to the
nares or eyes.
• These infections occur more frequently in cold seasons or
weather and crowded areas.
• After inhalation or contact with the organism, there is direct
invasion of the respiratory epithelium resulting in symptoms
corresponding to the areas involved.
GENERAL SIGNS AND SYMPTOMS
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There is significant overlap in the clinical manifestations of the different URTIs.
Onset of symptoms occurs 1-3 days after exposure to the pathogens.
Generally, the symptoms of URTIs result from the toxins released from the
pathogens as well as the inflammatory response mounted by the immune system
to fight the infections.
Common symptoms of the URTI’s include
Nasal congestion
Runny nose (rhinorrhoea)
Nasal Discharge( may change from clear to white to green)
Nasal Breathing
Sneezing
Sore throat or scratchy throat
painful swallowing(odynophagia)
cough(from laryngeal swelling and post nasal drip)
malaise and
fever( more common in children)
• Other less common symptoms may include
Foul breath
Poor smelling sensation (hyposmia)
Headache
Shortness of breath
Sinus pain
Itchy and watery eye(conjunctivitis)
Nausea and vomiting
Diarrhoea
Body aches
• Symptoms last between 3-14 days; if symptoms last longer than that
alternative diagnosis should be considered.
GENERAL DIAGNOSIS OF URTIs
• The diagnosis of URTIs is typically made based on REVIEW OF
SYMPTOMS, PHYSICAL EXAMINATION and OCCASIONALLY
LABORATORY TESTS.
• Laboratory testing is generally not recommended in the evaluation of
URTIs because most are are caused by viruses hence specific testing is not
recommended.
• Some important situations where specific testing is required includes:
 suspected strep throat
 Possible bacterial infection
 Prolonged symptoms
 Evaluation of allergens and asthma
 Enlarged lymph node and sore throat that may be caused by Epstein Barr
Virus(mononucleosis)
 Testing for swine flu if suspected.
Introduction
• The Upper respiratory tract consists of the
nose and nasal passages, paranasal sinuses,
the pharynx and the portion of the larynx above
the vocal cords.
• Pharyngitis is the inflammation of the Pharynx,
hypopharynx, uvula and tonsils.
• Streptococcal pharyngitis is mainly caused by
Streptococcus pyogenes. It could also be
caused by a group of species called
Streptococcus dysgalactiae
Introduction
• Although humans can be asymptomatic nasopharyngeal
or perineal carriers of S pyogenes, the organism should
be considered significant if it is detected by culture or
other means.
• The ultimate source of group A streptococci is a person
harboring these organisms.
• The individual may have a clinical or subclinical infection
or may be a carrier distributing streptococci directly to
other persons via droplets from the respiratory tract or
skin.
• The nasal discharges of a person harboring S pyogenes
are the most dangerous source for spread of these
organisms.
Aetiology
• Group A streptococcus (Streptococcus
pyogenes) is the leading cause of pharyngitis
and cellulitis.
• It is also an important cause of impetigo,
necrotizing fascilitis and streptococcal toxic
syndrome.
• It is also the inciting factor of two
immunologic diseases: RHEUMATIC FEVER
AND ACUTE GLOMERULONEPHRITIS
• Streptococcus are gram positive cocci arranged
in chains or pairs.
• All streptococci are CATALASE NEGATIVE.
CLASSIFICATION OF STREPTOCOCCI
Based on the type of hemolysis
1. Alpha hemolytic streptococcus
2. Beta hemolytic streptococcus
3. Peptostreptococcus
ALPHA HEMOLYTIC STREPTOCOCCI
• Form green zone around their colonies as a result of incomplete lysis of
Red Blood cells in the agar.
• The green color is formed when hydrogen peroxide produced by the
bacteria oxidizes hemoglobin (Red) to biliverdin (Green).
• The principle organisms in this group are Streptococcus pneumonia and
Streptococcus viridans group (S. sanguis, S .mutas)
• Streptococci pneumonia growth is inhibited by OPTOCHIN and its
colonies dissolve when exposed to bile while the viridans group doesn’t
exhibit these characteristics.
• Inflammation is thought to be the major way pnemococcus causes disease.
• Viridans streptococci are part of the normal flora of the human pharynx
and intermittently reach the blood stream to cause endocarditis.
• Some viridans group are non hemolytic.
BETA HEMOLYTIC STREPTOCOCCI
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Form a clear zone around their colonies because of complete lysis of red cells
occur.
• Beta hemolysis is due to production of enzymes (hemolysins called streptolysin o
and streptolysin s).
Antigens used in beta hemolysis
1. C- carbohydrate: determines the group, located in the cell wall and its specificity is
determined by an amino sugar.
2. M-protein: most important virulence factor and determines the type of Group A
hemolytic streptococci. It protrudes from the outer surface of the cell and interferes
with ingestion of phagocytes (i.e antiphagocytic). Antibody to M protein provides
type specific immunity.
• Approximately 80 serotypes based on M protein
• The type of M protein produced by the strain of S. pyogenes determines if it will
primarily cause rheumatic fever or acute glomerulonephritis.
• Beta hemolytics are arranged into groups A-H and K-U (Lancefield groups)
based on the antigenic difference of the M protein.
Group A streptococcus (Streptococcus
pyogenes)
• Major bacterial cause of pharyngitis and common cause
of other skin infections (impetigo).
• They adhere to pharyngeal epithelium via pili composed
of lipoteichoic acid and M protein.
• Infection may be invasive (more severe and less common)
or non-invasive.
• Growth of S. pyogenes in the lab is inhibited by the
antibiotic Bacitracin (an important diagnostic criteria).
• Additional complications may be caused by GAS namely:
acute rheumatic fever and acute glomerulonephritis.
Group B streptococcus(Streptococcus
agalactiae)
• Colonizes the genital tract of women and causes neonatal meningitis and
sepsis.
• It increases the risk of premature rupture of membrane during pregnancy
and transmission of the organism to the infant.
• They are Bacitracin resistant.
• They hydrolyze (break down) Hippurate (an important diagnostic criteria).
Group C streptococcus (S. equi and S. zooepidemicus)
• S. equi causes strangles in horses.
• S. dysgalactiae is also a member that causes pharyngitis and other
pyogenic infections similar to group A streptococci.
Group D streptococcus
• ENTEROCOCCI (e.g. E. faecalis and E. faecium)
- Members of the normal flora of the colon and are noted to cause URINARY,
BILIARY and CARDIOVASCULAR INFECTIONS.
- They are very hardy organisms; they can grow in hypertonic (65%), saline
or bile and are not killed by Penicillin G.
- Hence synergistic combination of penicillin and aminoglycoside (e.g.
gentamicin) is required to kill enterococci.
- Vancomycin can be used but vancomycin-resistant enterococci (VRE) have
emerged and become an important and much feared cause of lifethreatening nosocomial infection.
• NON ENTEROCOCCI (S.bovis)
- Cause similar infection but are inhibited by 6.5% sodium chloride and are
killed by penicillin.
Groups E, F, G, H, K – U rarely/infrequently cause human infections.
PEPTOSTREPTOCOCCI
• Grow under anaerobic or microaerophilic
conditions and produce variable hemolysis.
• Members of the normal flora of the gut, mouth
and female genital tract.
• Participate in mixed aerobic infections
(infections caused by multiple bacteria:
aerobes and facultative).
• Peptostreptococci and viridans streptococci
(members of the normal oral flora are found in
brain abscesses after dental surgery.
MODE OF TRANSMISSION
• Most streptococci are part of the normal flora of the human
body but produce disease when they get access to blood and
body tissues.
• Viridans and S. pneumoniae are found in the pharynx and
oropharynx.
• S. pyogenes is found in the skin and oropharynx.
• S. galactiae is found in the vagina and the colon.
• Enterococci and anaerobic streptococci are found in the colon.
• GAS (Streptococci pyogenes is transmitted through large
respiratory droplets or direct contact with infected persons or
carriers.
• Outbreak of streptococcal infection may occur as a result of
ingestion of contaminated foods such as milk, meat produce and
eggs.
Morphology and Identification
• Individual cocci are spherical or ovoid and are
arranged in chains.
• Streptococci are gram positive but as culture
ages, they die and lose their gram positivity and
appear as gram negative
• They produce capsules composed of hyaluronic
acid which phagocytosis
• Their cell wall contains proteins (M, T, R
antigens), carbohydrates and peptidoglycans
Morphology and identification
• S pyogenes is Beta Hemolytic
• They grow poorly on solid media or in broth,
unless enriched with blood or tissue fluids.
• Growth and hemolysis are aided by incubation
in 10% Carbon dioxide.
• They grow best at 37oC
• They are facultative anaerobes and grow under
aerobic and anaerobic conditions
Morphology and Identification
• S pyogenes give rise to either matte or glossy
colonies.
• Matte colonies consist of organisms that
produce much M protein and generally are
virulent.
• The S pyogenes in glossy colonies tend to
produce little M protein and are often not
virulent.
Pathogenesis
• ​When the organism enters the upper
respiratory tract, it attaches itself to the
epithelium lipoteichoic acid which is in the
hair-like projections.
• ​M protein and hyaluronic acid in the capsule
of the bacteria inhibits phagocytosis. thus
increasing it's virulence.
• ​Thus causing inflammation (pharyngitis).​
Clinical Features
• Sore throat
• Fever with sudden onset (greater than 38.3
degrees C)
• Tonsilar exudates
• Cervical adenopathy
• Swollen uvula
• Palatal petechiae
• Scarlatiniform rash
The above two are less common and highly
specific.
Differential Diagnosis
Viral Pharyngitis
• Absence of cough
• Absence of Conjunctivitis
• Nasal discharge
• Diarrhea
Complications
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Acute rheumatic fever
Scarlet fever
Streptococcal toxic shock syndrome
Glomerulonephritis
Peritonsilar abscess
Cervical lymphadenitis
Mastoiditis
DIAGNOSIS
• There is broad overlap between the signs and symptoms
of streptococcal and nonstreptococcal (usually viral)
pharyngitis, and the ability to identify streptococcal
pharyngitis accurately on the basis of clinical grounds
alone is generally poor.
• Therefore, except when obvious viral clinical and
epidemiological features are present, a laboratory test
should be performed to determine whether GAS is
present in the pharynx
• Selective use of diagnostic studies for GAS on the basis
of clinical features increases not only the proportion of
positive test results but also the proportion of patients
who have positive test results and who are truly infected
rather than mere carriers of streptococcus
Clinical diagnosis
• The modified Centor criteria may be used to
determine the management of people with
pharyngitis
• Based on 5 clinical criteria, it indicates the
probability of a streptococcal infection
• One point is given for each of the criteria:
– Absence of cough
– Swollen and tender cervical lymph nodes
– Temperature >38.0 degree celcius
– Tonsillar exudate or swelling
– Age less than 15 (a point is subtracted if age
>44)
Modified Centor score
Points
Probability
Of Strep
Management
1 or
fewer
<10%
N0 antibiotic or
Culture needed
2
11-17%
Antibiotic based on
Culture or RADT
3
28-35%
Antibiotic based on
Culture or RADT
4 or 5
52%
Empiric antibiotics
Laboratory diagnosis
Throat Culture
– Culture of a throat swab on a sheepblood agar
plate has been the standard for the documentation
of the presence of GAS pharyngitis in the upper
respiratory tract and for the confirmation of the
clinical diagnosis of acute streptococcal
pharyngitis .
– If performed correctly, culture of a single throat
swab on a blood agar plate is 90%–95% sensitive
for detection of GAS pharyngitis
Rapid antigen detection test (RADT).
– A major disadvantage of throat cultures is the
delay (overnight or longer) in obtaining results.
– RADTs have been developed for the identification
of GAS pharyngitis directly from throat swabs, with
shorter turnaround time.
– A negative RADT should be accompanied by a
follow-up or back-up throat culture in children and
adolescents, while this is not necessary in adults
under usual circumstances
Treatment
• Untreated streptococcal pharyngitis usually
resolves within a few days.
• The primary reason for treatment with
antibiotics is to reduce the risk of complications
such as rheumatic fever and retropharyngeal
abscesses and they are effective if given within 9
days of the onset of symptoms
Treatment
Analgesics
• Analgesics such as non-steroidal antiinflammatory drugs (NSAIDs) and
paracetamol(acetaminophen) help significantly in
the management of pain associated with strep
throat.
• Viscous lidocaine may also be useful. While
steroids may help with the pain, they are not
routinely recommended.
• Aspirin may be used in adults but is not
recommended in children dueto the risk of Reye's
syndrome
Treatment
Antibiotics
• The antibiotic of choice in the United States for
streptococcal pharyngitis is penicillin V due to
safety, cost, and effectiveness.
• Amoxicillin is preferred in Europe. In India, where
the risk of rheumatic fever is higher, intramuscular
benzathine penicillin G is the first choice for
treatment.
• Appropriate antibiotics decrease the average 3–5
day duration of symptoms by about one day, and
also reduce contagiousness. They are primarily
prescribed out of a motivation to reduce rare
complications such as rheumatic fever and
peritonsillar abscess.
• The arguments in favor of antibiotic treatment should be
balanced by the consideration of possible side effects,
and it is reasonable to suggest that no antimicrobial
treatment be given to healthy adults who have adverse
reactions to medication.
• Antibiotics are prescribed for strep throat at a higher
rate than would be expected from its prevalence.
Erythromycin and other macrolides or clindamycin are
recommended for people with severe penicillin allergies.
• First generation cephalosporins may be used in those
with less severe allergies and some evidence supports
cephalosporins as superior to penicillin.
• Streptococcal infections may also lead to acute
glomerulonephritis; however, the incidence of this side
effect is not reduced by the use of antibiotics.
Prevention
• Tonsillectomy may be a reasonable preventive
measure in those with frequent throat infections
(more than three a year).
• The benefits are, however, small and episodes
typically lessen in time regardless of measures
taken. Recurrent episodes of pharyngitis which test
positive for GAS may also represent a person who
is a chronic carrier of GAS who is getting recurrent
viral infections.
• Treating people who have been exposed but who
are without symptoms is not recommended.
Treating people who are carriers of GAS is not
recommended as the risk of spread and
complications is low.
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